JP2004078181A - Fixing device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which allows acquisition of images of high quality free from unevenness of printing quality like gloss by accurately controlling the temperature of a fixing member 20 even at the time of using a fixing belt having an elastic layer as the fixing member and to provide an image forming device having the fixing device mounted therein. <P>SOLUTION: Power required for heating, which is supplied to a heating body 16 is corrected by prescribed power before a temperature detection means 18 detects a temperature variance accompanied with inrush of a recording material P, and the power required for heating, which is supplied to the heating body 16 is corrected by the prescribed power at a prescribed timing when the fixing device is started at the time of print start, and a value of the prescribed power is approximately equal to a power value required for giving a prescribed temperature to the fixing device. The value of the prescribed power is determined in accordance with a heat capacity of the recording material, a heat storage condition of the fixing device, etc. as needed. <P>COPYRIGHT: (C)2004,JPO

Description

【０１１０】
ＰＩＤ制御を行わず所定の電力を投入する時間は定着ベルト２０の温度リップルを最小限にするように選んだものである。通紙開始時の記録材Ｐの突入前から補正した電力を投入する。これは、記録材Ｐの定着ニップ部への突入と同時に補正電力を投入すると、定着ベルト２０の温度の低下が大きくなってしまう場合があるためである。補正電力投入のタイミングが早すぎると定着ベルト２０の温度の上昇が大きくなってしまい、遅すぎると前出したように記録材Ｐの定着ニップ部への突入後に定着ベルト２０の温度の低下が生じてしまう。本実施の形態においては、適切なタイミングである約０．５秒を用いた。また、ＰＩＤ制御を行わず所定の電力を投入する時間が短すぎると、通常のＰＩＤ制御に近づくため、所定電力投入の効果が小さくなってしまう。長すぎると通紙時に伴う定着ベルト２０の温度の変動が大きくなりＰＩＤ制御に戻った際に温度リップルが大きくなってしまう。このため、本実施の形態では通紙開始前約０．５秒から約１秒間、所定電力投入制御を行うこととした。
【０１１１】
図１０に本実施の形態における、電力制御方法についてのフローチャートを示す。
【０１１２】
以下にフローに従って、実際の補正動作について説明する。
【０１１３】
図１０において、画像形成装置は電源ＯＮ後にプリント信号を受信可能な状態に立ち上がる（ａ１）。図不示のホストコンピュータからプリントコマンドを受信（ａ２）すると、プリント信号からペーパーモードを読み取る（ａ３）。プリンタ内の制御回路部（ＣＰＵ）２１は、表１に示すようにペーパーモードに対応した通紙時投入電力Ｅ２（Ｗ）を決定する（ａ４）。その後、制御回路部２１はヒータ駆動回路２８を駆動することにより、定着ベルト２０を所定温度に温調すべく、ヒータ２１の立ち上げ温調制御を開始する（ａ５）。定着ベルト２０が所定温度付近になり、立ち上げ温調が終了（ａ６）すると、プリント温調温度である１９０℃を目標温度に設定してＰＩＤ制御により目標温度に温調される（ａ７）。その後、記録材突入の約０．５秒前まで、ＰＩＤ制御を行いながら、目標温度で待機する（ａ８）。
【０１１４】
記録材突入の約０．５秒前になると、ＰＩＤ制御を中止し、ａ４時に決定された通紙時投入電力として所定の電力Ｅ２（Ｗ）を出力し（ａ９）、記録材突入後約約０．５秒後まで継続して、Ｅ２（Ｗ）を投入しつづける（ａ１０）。その後、プリント温調温度である１９０℃を目標温度に設定してＰＩＤ制御を再開する（ａ１１）。
【０１１５】
以上の動作をプリント終了まで続け（ａ１２）、プリントジョブが終了した時点で、温調制御が終了する（ａ１３）。この補正は、プリンタ内の制御回路部（ＣＰＵ）２１内に備えられた、ペーパーモードと通紙時投入電力Ｅ２（Ｗ）のテーブル（表１）に基づいて行う。
【０１１６】
以上、説明したように、記録材Ｐの突入タイミングの前後一定時間、ＰＩＤ制御を中止し、定着ヒータに投入される電力を所定の値に補正して投入することによって、温度検知のむだ時間による通紙開始時の記録材Ｐの突入に伴う温度変動を生じることなく、より安定した温度制御を行うことができる。
【０１１７】
さらに、記録材Ｐの坪量による熱容量の違いを考慮した、所定電力の補正を行うことによって、記録材Ｐの熱容量にかかわらず、安定した温度制御を行うことが出来る。
【０１１８】
（４）本実施の形態を用いた場合の、温度測定結果および画像出力実験結果
本実施の形態においては、通紙開始時の記録材突入前の約０．５秒から約１秒間、ＰＩＤ制御を禁止するとともに表１に基づいた固定電力を投入し、その後ＰＩＤ制御を再開するようにした。このとき投入される電力は先述したように用いる紙の坪量に従い決定されるものである。ＰＩＤ制御を禁止し、所定の電力を投入する時間については、上述した理由から記録材突入前の約０．５秒から約１秒間としてある。
【０１１９】
１）実験方法
定着装置はプロセススピード８７ｍｍ／ｓｅｃで回転し、メインサーミスタ１８の検知温度を１９０℃となるように温調され、十分な時間が経過している。
この状態で、坪量が１２８ｇ／ｍ^２であるニューＮＰＩ上質紙１２８ｇ（日本製紙、商品名）という記録材を連続通紙（１６枚／分）した。
【０１２０】
この際、定着スリーブ２０内面温度として、メインサーミスタ１８の温度測定値を記録した。また、電力についてはＹＯＫＯＧＡＷＡ製ＷＴ２００　ＤＩＧＩＴＡＬ　ＰＯＷＥＲ　ＭＥＴＥＲを介して電力値の出力を同じくキーエンス製ＰＣ用温度レコーダーＮＲ２５０にてＡ／Ｄ変換しＰＣに取り込むことにより測定した。
【０１２１】
定着後画像の光沢度については、測定器として、日本電色工業株式会社製の光沢度計ＰＧ−３Ｄを使用し、ＪＩＳ　Ｚ　８７４１における７５度鏡面光沢度測定方法により測定を行った。
【０１２２】
記録材上のトナー量としては、イエロー、マゼンタ、シアン、ブラックの、いわゆる１次色のべた画像部のトナー量が約０．５〜０．６ｍｇ／ｃｍ^２、レッド、グリーン、ブルーの、いわゆる２次色（二色のトナーを重ねた画像）のべた画像部のトナー量が約１．０〜１．２ｍｇ／ｃｍ^２の状態で定着を行い、定着後画像の光沢度を測定した。
【０１２３】
定着性を評価する為の擦り試験としては、記録材Ｐ上に５ｍｍ×５ｍｍの黒単色のべ夕画像を形成し、本実施の形態における定着装置を用いて５０枚連続して１６ｐｐｍの速度で定着し、その後、画像形成面上にシルボンＣ（商品名）を介して所定重量（２００ｇ）のおもりを載せた状態で画像形成面を５往復摺擦させ、その摺擦の前後での、画像の反射濃度低下率（％）を求めた。この反射濃度の変化率（濃度低下率）が小さいほど定着性が良いと言える。反射濃度の測定にはＧｒｅｔａｇ　Ｍａｃｂｅｔｈ　ＲＤ９１８（商品名）を用いた。測定には定着した５０枚の記録材のうち１，２，３，５，１０，２０，３０，４０，５０枚目の記録材の各被記録紙で９点の濃度低下率を測定して、その最悪値を用いた。
【０１２４】
２）実験結果
図７に本実施の形態を用いた場合の定着装置における通紙前後での定着ヒータ１６に投入する電力と定着ベルト２０内面温度の挙動を記録したグラフを示す。
【０１２５】
図７に示すように記録材Ｐの定着ニップ部突入前後において、安定した温調（温度リップル約７℃）を示した。
【０１２６】
このとき、記録材Ｐの定着ニップ部突入前後に定着ヒータ１６に投入される電力は、空回転時の約８０Ｗから記録材Ｐが定着ニップ部に突入する０．５秒前に、強制的に約３００Ｗが投入されており、記録材Ｐが定着ニップ突入した後に大きな電力変動を生じることなく、安定した温調制御を行うことができた。
【０１２７】
このように、約７℃以内の温度リップルを保つことができれば、出力された印刷物の一枚内でのグロス変動は、単色で約４、２次色では約６であった。表２に、本実施の形態における、各色のグロスの、記録材１枚内での平均値及び記録材１枚内でのグロス変動幅を示す。このように本発明を適用することにより平均値が比較的高く、記録材１枚内での変動幅も小さい、安定したグロスを得ることが出来た。
【０１２８】
【表２】

【０１２９】
また、定着性試験における濃度低下率の最悪値は１５％であり、良好な定着性を得ることができた。
【０１３０】
（５）比較例１
従来の定着装置においては、記録材Ｐ突入前後での所定電力投入を行わず、全てＰＩＤ制御により温調制御を行っている。
【０１３１】
１）実験方法
第一の実施の形態における実験と同様の定着装置構成、測定方法を用いて実験を行ったので、ここでは省略する。ただし、従来の定着装置における制御は上述したとおり、所定電力投入を行わず、全てＰＩＤ制御により温調制御を行った点が異なる。
【０１３２】
２）実験結果
図６に比較例１の定着装置における、記録材の定着ニップ部突入前後に定着ヒータ１６に投入される電力と、定着ベルト２０内面の温度挙動を記録したグラフを示す。
【０１３３】
図６に示すように記録材Ｐが定着ニップ部に突入する前の空回転時においては、定着スリーブ２０内面温度は安定した挙動を示すものの、記録材Ｐがの定着ニップ部に突入した直後に、定着スリーブ２０内面温度は、目標温度に対して約１０℃低い値まで降下した後、目標温度に対して約７℃高い温度まで上昇する。その後、定着スリーブ２０内面温度が安定するまでに、約１０秒を要し、温度リップルは約１７℃となった。そして、その後の記録材Ｐ連続通紙においては、安定した温調（温度リップル約６℃）を示した。
【０１３４】
このように、約１７℃の温度リップルを生じた場合、試験に用いたインライン型の電子写真方式カラー画像形成装置においては出力された印刷物のグロスは、記録材Ｐ一枚内において、単色で約９、２次色では約１４変動し、画質の低下を招いた（表３）。
【０１３５】
【表３】

【０１３６】
また、定着性試験における濃度低下率の最悪値は２８％であった。定着性が２０％を超えるような場合には、画像をユーザーが使用している時に、文字がはがれたり、ハーフトーン画像がぼやけてしまうばかりでなく、手や衣服やほかの紙が汚れるといった問題が発生する。
【０１３７】
記録材Ｐ内の、濃度低下率の大きい領域は、定着ベルト２０内面の温度が落ち込んだ領域と一致しており、温度リップルが生じることによる部分的な温度低下が、定着性に影響を及ぼしていることが分かった。このように、本比較例においては、測定ポイントによる定着性のばらつきが大きく、定着装置として、十分な性能が得られない。
【０１３８】
（６）考察
記録材Ｐが定着ニップ部に突入する前後に、所定の値に固定された電力を投入することによる効果は、以下のように考えられる。
【０１３９】
空回転時および通紙時における、安定した状態において、定着ヒータ１６に投入される電力は、ほぼ一定である。定常時における前回転時必要電力値をＥ１（Ｗ）、記録材通紙時の呈上時に必要とされる電力値をＥ２（Ｗ）とする。
【０１４０】
記録材Ｐが定着ニップ部に突入するとき、記録材により、定着ベルト２０温度が急激に効果する。通常のＰＩＤ制御であれば、温度変動をメインサーミスタ１８によって検知してから、電力制御が行われる。このため、メインサーミスタ１８が発熱部から離れて設置されている場合、急激な温度変化が生じた際に、メインサーミスタ１８の検知温度が、定着ヒータ１６や定着ニップ部の温度の実際の温度と異なる値を示すため、過剰に電力が投入されたり、逆に投入電力が不足する場合がある。そのため、温度リップルが生じ、定着スリーブ２０内面温度が安定しない。
【０１４１】
これに対して、本実施例においては、記録材Ｐが定着ニップ部に突入するタイミングとあわせて、あらかじめ必要とされる電力Ｅ２（Ｗ）を固定値として投入するため、電力の過不足が生じない。したがって、通常のＰＩＤ制御よりも温度リップルを小さくすることが可能となる。
【０１４２】
所定電力の投入は長時間は必要でなく、ある程度定着ベルト２０内面温度が安定するまでの区間投入すれば、その後は通常のＰＩＤ制御に復帰しても、十分安定した温調制御が可能である。
【０１４３】
また、記録材Ｐの性質によって、通紙により定着ベルト２０から奪われる熱量は異なるため、本実施の形態においては、特に記録材Ｐの坪量に着目し、熱容量の違いを考慮した略必要電力に補正した。
これにより、安定した温度制御（温度リップル約７℃）が達成できた。
【０１４４】
（７）所定電力値について
尚、通紙開始時に投入される所定電力値はＥ２（Ｗ）と略同一であれば良く、Ｅ２（Ｗ）との電力差の大きさについては所望の温度リップルとなる範囲であれば良い。
【０１４５】
すなわち、本実施の形態においてはペーパーモードにより、記録材が定着ニップ部に突入する前後に投入する所定電力（通紙時オフセット電力）を決定している。このとき、ペーパーモードの対応メディアにおいて必要な電力が厳密に一致していなくても、略同一であればよい。これは、一定時間の所定電力投入後はＰＩＤ制御に戻ることによって、再び目標温度に近づくように制御されるからである。つまり、厳密に一致していない場合に温度が目標温度から遠ざかることになるが、その後再びＰＩＤ制御により、目標温度に近づく様に制御されるわけである。そのときの温度変動が所望の温度リップル内であれば良い。
【０１４６】
一般にプリントスピードが高速の場合においては記録材Ｐの坪量の違いに伴う適切な通紙時オフセット電力の違いの差がさらに大きくなるため、本実施の形態よりさらに細かく通紙時オフセット電力の場合分けを行うことが必要である。このような場合には、ペーパーモードをさらに細かくすることや、紙厚センサなどを利用して坪量と対応させることにより、さらに細かい坪量と通紙時オフセット電力の対応を行うことで、所望の温度リップル内での温度制御が可能である。
【０１４７】
（８）まとめ
以上、本実施の形態においては、通紙開始時の記録材Ｐが定着ニップ部に突入するタイミング前後に、一定時間ＰＩＤ制御を禁止し、定着ヒータ１６に投入される電力を所定の値に補正して投入することによって、温度検知のむだ時間による通紙開始時の記録材Ｐの突入に伴う温度変動を生じることなく、より安定した温度制御を行うことができた。
【０１４８】
また、投入する電力値を決定する際に、記録材Ｐの坪量による熱容量の違いを考慮し、補正を行うことにより、さらに正確に安定した温度制御を行うことができた。
【０１４９】
温度リップルを小さく押さえることで、定着部材の正確な温調制御を行い、その結果良好な定着性を示し、定着温調温度が不適切な場合に発生する画像不良が無く、グロスなどの印字品質ムラのない高品質な画像を得ることができた。
【０１５０】
〈実施の形態２〉
本実施の形態では、通紙開始時の記録材Ｐが定着ニップ部に突入するタイミングの前後一定時間ＰＩＤ制御を禁止し、定着ヒータ１６に投入される電力を所定の電力に補正して投入する際に、メディアセンサを用いて定着装置からの伝熱性や熱容量が特殊な記録材Ｐを検知し、その伝熱性や熱容量を考慮した略必要電力値に補正することによって、温度検知のむだ時間による、記録材Ｐが定着ニップ部に突入した際の温度変動を生じることなく、より安定した温度制御を行う方法について説明する。
【０１５１】
本実施の形態では、定着装置の大まかな構成と制御は実施の形態１と同様である。しかし、定着ヒータ１６に投入される電力を所定の電力に補正する際に、定着装置からの伝熱性や熱容量が特殊な記録材Ｐの、伝熱性や熱容量を考慮した略必要電力値に補正することが異なる。
【０１５２】
画像形成装置の構成は実施の形態１と同様であり、図１に示すとおりである。また、定着装置の構成は、実施の形態１と同様で図２〜４に示した通りであり、重複する説明は省略する。
【０１５３】
記録材Ｐ表面の平滑性が悪い、いわゆるラフ紙と呼ばれる記録材や、ＯＨＴなどのフィルム系の記録材においては定着装置から記録材Ｐへの伝熱性や熱容量が異なることから、定着時の条件が同じであっても、所定の電力に補正する際に必要な電力が異なる。
【０１５４】
これは、略同一な坪量の記録材において、一般的な平滑紙の熱の伝わりに比べて、ラフ紙においては表面の平滑性が悪いことにより熱の伝わりが悪く、また、ＯＨＴなどのフィルム系の記録材においては表面性が良いことと、材質が違うために熱容量が大きいことから定着の際により多くの熱量を必要とするからである。
【０１５５】
より正確な温度制御を行う為には、定着ヒータ１６に投入される電力を所定の電力に補正する際に、定着装置からの伝熱性や熱容量が特殊な記録材Ｐの伝熱性や熱容量を考慮した略必要電力値に補正することが有効である。よって、これらのメディアの違いをメディアセンサ５１で判別することによって伝熱性や熱容量を考慮した略必要電力値に補正することとした。
【０１５６】
メディアセンサ５１の構成概略図を図８に示す。メディアセンサ５１は光源としてＬＥＤ３３、読取手段としてＣＭＯＳセンサ３４、結像レンズとしてレンズ３５、３６を有している。ＬＥＤ３３を光源とする光は、レンズ３５を介し、記録材搬送ガイド３１もしくは記録材搬送ガイド３１上の記録材Ｐ表面に照射される。この反射光は、レンズ３６を介し集光されてＣＭＯＳセンサ３４に結像される。これによって、記録紙搬送ガイド３１もしくは記録材Ｐの表面映像を読み取る。これにより、記録材Ｐの紙繊維の表面状態を読み込み、そのアナログ出力をＡ／Ｄ変換しディジタルデータとする。ディジタルデータのゲイン演算及びフィルタ演算は、制御プロセッサ（図不示）によってプログラマブルに処理される。そして、映像比較演算をおこない、この映像比較演算結果に基づき紙種を判定する。
【０１５７】
本実施の形態では定着ヒータ１６に投入する電力を補正する際に、メディアセンサ５１により記録材がラフ紙、またはＯＨＴなどのフィルム系の記録材であることを検知することにより記録材Ｐの伝熱性や熱容量の違いを考慮した略必要電力に補正することにした。ここで実施の形態１における所定電力値は、同一ペーパーモード内においても、記録材Ｐがラフ紙である場合やＯＨＴなどのフィルム系の記録材である場合には異なる補正値を用いるものとした。
【０１５８】
表４に本実施の形態における各ペーパーモードと通紙時投入電力の関係を示す。
【０１５９】
【表４】

【０１６０】
記録材Ｐが一般的な伝熱性および熱容量をもつメディアの場合には、実施の表４の「平滑紙」欄の値を用いる。
【０１６１】
記録材がラフ紙の場合には表４に示すように、補正値を一般的な平滑紙に比べて小さくし、また、ＯＨＴなどのフィルム系の記録材（フィルムメディア）の場合には補正値を一般的な平滑紙に比べて大きくした。
【０１６２】
次に、本実施の形態を用いた場合の実際の補正動作について説明する。
【０１６３】
図１１に本実施の形態における、記録材Ｐが定着ニップ部に突入タイミングの前後一定時間ＰＩＤ制御を禁止し、定着ヒータに投入される電力を所定の値に補正して投入する際に、メディアセンサを用いて定着装置からの伝熱性や熱容量が特殊な記録材Ｐを検知し、その伝熱性や熱容量を考慮して定着ヒータ１６に必要となる必要電力値を投入する方法についてのフローチャートを示す。
【０１６４】
以下にフローに従って、実際の補正動作について説明する。
【０１６５】
図１１において、画像形成装置は電源ＯＮ後にプリント信号を受信可能な状態に立ち上がる（ｂ１）。不図示のホストコンピュータからプリントコマンドを受信（ｂ２）すると、プリント信号からペーパーモードを読み取る（ｂ３）。その後、制御回路部２１はヒータ駆動回路２８を駆動することにより、定着ベルト２０を所定温度に温調すべく、ヒータ２１の立ち上げ温調制御を開始する（ｂ４）。その後、メディアセンサ５１により記録材Ｐが普通紙であるか、ラフ紙（伝熱性が低く、熱容量の小さい記録材）であるか、フィルムメディア（伝熱性が高く、熱容量の大きい記録材）であるかを判別する（ｂ５）。その後、プリンタ内の制御回路部（ＣＰＵ）２１は、表１、４に示すようにペーパーモードと記録材の特性（普通紙であるか、ラフ紙であるか、フィルムメディアであるか）に対応した通紙時投入電力Ｅ２（Ｗ）を決定する（ｂ６）。定着ベルト２０が所定温度付近になり立ち上げ温調が終了（ｂ７）すると、プリント温調温度である１９０℃を目標温度に設定してＰＩＤ制御により目標温度に温調される（ｂ８）。その後、記録材が定着ニップ部に突入する約０．５秒前まで定着器を駆動、温調しつつ、待機する（ｂ９）。
【０１６６】
記録材が定着ニップ部に突入する約０．５秒前を検知した際に（ｂ９）、ＰＩＤ制御を禁止し、ｂ６時に決定された通紙時投入電力Ｅ２（Ｗ）を出力し（ｂ１０）、記録材た定着ニップ部へ突入した後約約０．５秒経過するまで、Ｅ２を投入し続ける（ｂ１１）。その後、プリント温調温度である１９０℃を目標温度に設定してＰＩＤ制御を再開する（ｂ１２）。
【０１６７】
以上の動作をプリント終了まで継続し（ｂ１３）、プリントジョブが終了すると同時に、温調制御が終了する（ｂ１４）。
【０１６８】
以上、説明したように、通紙開始時の記録材Ｐが定着ニップ部に突入するタイミングの前後一定時間、ＰＩＤ制御を禁止し、定着ヒータに投入される電力を所定の値に補正して投入する際に、メディアセンサを用いて定着装置からの伝熱性や熱容量が特殊な記録材Ｐを検知し、その伝熱性や熱容量を考慮した略必要電力値に補正することによって、温度検知のむだ時間に記録材Ｐが定着ニップ部に突入した際に、定着ベルトの温度変動を生じることなく、より安定した温度制御を行うことができる。
【０１６９】
次に、本実施の形態を用いた場合の、温度挙動の安定化や、画質改善の効果を、従来例や実施の形態１との比較により示すため、以下に示す条件で、定着装置の温度挙動を測定し、定着画像の確認を行った。
【０１７０】
定着装置はプロセススピード８７ｍｍ／ｓｅｃで回転し、メインサーミスタ検知温度を１９０℃一定になるように温調され十分な時間が経過している。この状態において、ラフメディアとして、坪量が７５ｇ／ｍ^２であるＦｏｘＲｉｖｅｒＢｏｎｄ（Ｆｏｘ　Ｒｉｖｅｒ、商品名）と、フィルムメディアとして、坪量が１６６ｇ／ｍ^２であるカラーレーザー光沢フィルム　ＧＦ−２（Ｃａｎｏｎ販売、商品名）を連続通紙（１６枚／分）した。
【０１７１】
この際に、定着スリーブ２０内面温度として、メインサーミスタ１８の温度測定値を記録した。
【０１７２】
また、電力についてはＹＯＫＯＧＡＷＡ製ＷＴ２００　ＤＩＧＩＴＡＬ　ＰＯＷＥＲ　ＭＥＴＥＲを介して電力値の出力を同じくキーエンス製ＰＣ用温度レコーダーＮＲ２５０にてＡ／Ｄ変換しＰＣに取り込むことにより測定した。
【０１７３】
通紙前に定着ヒータ１６に投入される電力はそれぞれの条件において略同一であり、約８０Ｗであった。
【０１７４】
表５に比較例１の定着装置と実施の形態１、２における通紙前後での温度リップルを示す。
【０１７５】
【表５】

【０１７６】
表５から分かるように、本実施の形態を行うことによって、さらに安定した温度制御（温度リップル約７℃）が達成できた。
【０１７７】
これは次のような根拠による。
【０１７８】
十分に温まった定着装置において、ＦｏｘＲｉｖｅｒＢｏｎｄ（７５ｇ／ｍ^２）は坪量から該当するペーパーモードで定着ヒータ１６に投入される電力は実施の形態１においては２７５Ｗである。しかし、この記録材はいわゆるラフ紙と呼ばれる伝熱性が悪く、熱容量の小さい記録材であり、記録材に与えられる熱量が、通常の平滑紙に比べて小さくなる為、所定電力を投入した際に相対的に電力過剰の状態となる。このため、記録材Ｐが定着ニップ部に突入時した際に温度上昇が発生し、温度リップルが一般的な平滑紙に比べて大きくなる。
【０１７９】
実施の形態２においては、ラフ紙を判別することによって、記録材が定着ニップ部に突入する前後で投入される電力は、ラフ紙の低伝熱性、低熱容量という性質を考慮して、小さく設定されていることから、記録材Ｐの突入時の温度上昇がおさえられる為、温度リップルが小さくなる。
【０１８０】
ＯＨＴなどのフィルム系の記録材においては、ラフ紙とは逆方向の補正により、同様の効果が得られる。
【０１８１】
このように、本実施の形態においては、記録材Ｐがラフ紙やＯＨＴ等のフィルムメディアである場合に、メディアセンサの検知結果にしたがって記録材が定着ニップ部に突入する際に投入される所定電力値の値補正することによって、安定した温度制御（温度リップル約７℃）が達成できた。
【０１８２】
尚、本実施の形態においてはラフ紙とＯＨＴなどのフィルム系記録材の判別による、投入電力の変更について説明したが、ラフ紙以外の、定着装置からの伝熱性や熱容量が特殊な記録材Ｐについても同様な補正によって通紙時オフセット電力を決定することが可能である。
【０１８３】
〈実施の形態３〉
本実施の形態では、記録材Ｐが定着ニップ部に突入するタイミングの前後一定時間ＰＩＤ制御を禁止し、定着ヒータ１６に投入される電力を所定の電力に補正して投入する際に、定着装置の蓄熱具合により、所定電力値を補正することによって、記録材Ｐが定着ニップ部に突入した際の温度変動を抑え、より安定した温度制御を行う方法について説明する。
【０１８４】
本実施の形態では、定着装置の大まかな構成と制御は実施の形態１、２と同様である。しかし、記録材Ｐが定着ニップ部に突入するタイミングの前後で、所定電力で定着ヒータ１６に投入される電力を補正する際に、所定電力値を、定着装置の蓄熱具合を考慮した値に補正することが異なる。
【０１８５】
画像形成装置の構成は実施の形態１と同様であり、図１に示すとおりである。また、定着装置の構成は、実施の形態１、２と同様で図２〜４に示した通りである。よって重複する説明は省略する。
【０１８６】
本実施の形態では記録材Ｐが定着ニップ部に突入するタイミングの前後に、所定電力で定着ヒータ１６に投入する電力を補正する際に、定着装置の蓄熱具合を考慮した略必要電力に補正することとした。
【０１８７】
つまりは、空回転時に安定した温調を行うために必要な電力を、「空回転オフセット電力」として、記録材Ｐの通紙時に、安定した温調を行う為に必要な電力を、「通紙時に投入される所定電力」とする。
【０１８８】
このとき、「通紙時に投入される所定電力＝空回転オフセット電力＋通紙時オフセット電力」となるように、「通紙時オフセット電力」を定義する。また、本実施の形態においては、空回転オフセット電力を定着装置の蓄熱具合によって変動するものとした。
【０１８９】
空回転オフセット電力や、通紙時オフセット電力の最適値は、定着装置の蓄熱具合によって変動する。例えば、室温状態の定着装置の立ち上げ直後の、最適な空回転オフセット電力は約２００Ｗ、十分に温まった定着装置においては、空回転オフセット電力は約８０Ｗが最適である。
【０１９０】
また、ペーパーモードが厚紙１の場合、通紙時オフセット電力は、室温状態からの定着装置立ち上げ直後では４２０Ｗ、十分に温まった状態においては３００Ｗが最適である。
【０１９１】
本実施の形態においては、このような、定着装置の蓄熱具合によって定着ヒータ１６に投入する電力が異なる場合においても、所定電力値を補正し、より精密な温調制御に対応できるようにした。
【０１９２】
表６に、本実施の形態の定着装置が十分に温まっている状態での、各ペーパーモードにおける通紙時オフセット電力を示す。前述した実施の形態１では、定着装置が十分に温まっている状態であり、この時の空回転オフセット電力は８０Ｗに相当する。この電力と表６に示す通紙時オフセット電力を足し合わせたものは、実施の形態１の表１に示した通紙時投入電力と等しい。
【０１９３】
【表６】

【０１９４】
また、定着装置の蓄熱具合は室温状態からの立ち上げ後の定着ヒータ１６への電力投入時間に依存することが分かっているため、本実施の形態においては印字カウントに従い空回転オフセット電力を変更することとした。印字カウントとは室温状態からの立ち上げ後に連続印字した場合の、定着装置のＡ４サイズ紙の印字枚数に対応するカウント数である。印字カウントとヒータホルダ温度、空回転オフセット電力は再現良く表７に示すような関係を示すことが分かった。
【０１９５】
【表７】

【０１９６】
さらに、本実施の形態においては、プリントジョブ終了後、定着装置が蓄熱した状態で再び立ち上げ制御を行う場合には、ヒータ１６へ通電を開始する直前の、サブサーミスタ１９の検知温度に応じて、定着装置の蓄熱具合を予想し、定着器の蓄熱具合が同等となる印字カウントを決定して、空回転オフセット電力を決定している。具体的には通電開始時のサブサーミスタ１９の検知温度が４０℃以下であるときには立ち上げ後のヒータホルダ温度が５５℃以下であることが予想される為、印字カウントは１であるとして、連続印字されれば１枚毎にカウントを２、３、４と増加させ、それに伴い空回転オフセット電力は下げる制御を用いる。以下同様にして、立ち上げ開始前の検知温度が４１〜５５℃であるときには、ヒーターホルダ温度が６０℃程度であると予想されるため、印字カウントは２あるとする。同様に、検知温度が５６〜７５℃であるときには印字カウント３、検知温度が７６〜９５℃であるときには印字カウント４、検知温度が９６〜１２５℃であるときには印字カウント６、検知温度が１２６℃以上であるときには印字カウント１０として、空回転オフセット電力を決定する。
【０１９７】
図１２に本実施の形態における、記録材Ｐが定着ニップ部に突入するタイミングの前後一定時間ＰＩＤ制御を禁止し、定着ヒータに投入される電力を所定の値に補正して投入する際に、定着装置の蓄熱具合を考慮した必要電力値と略同一に補正する方法についてのフローチャートを示す。
【０１９８】
以下にフローに従って、実際の補正動作について説明する。
【０１９９】
図１２において、画像形成装置は電源ＯＮ後にプリント信号を受信可能な状態に立ち上がる（ｃ１）。図不示のホストコンピュータからプリントコマンドを受信（ｃ２）すると、プリント信号からペーパーモードを読み取る（ｃ３）。そして、サブサーミスタ１９の温度Ｔａを検知する（ｃ４）。この検知温度Ｔａから、表７にしたがって、空回転オフセット電力（Ｗ）を決定する（ｃ５）。その後、制御回路部２１はヒータ駆動回路２８を駆動することにより、定着ベルト２０を所定温度に温調すべく、ヒータ２１の立ち上げ温調制御を開始する（ｃ６）。その後、メディアセンサ５１により記録材Ｐが普通紙であるか、ラフ紙（伝熱性の低い記録材）であるか、フィルムメディア（伝熱性の高い記録材）であるかを判別する（ｃ７）。その後、プリンタ内の制御回路部（ＣＰＵ）２１は、表６に示すようにペーパーモードと記録材の性質（普通紙であるか、ラフ紙であるか、フィルムメディアであるか）に対応した通紙時オフセット電力（Ｗ）を決定する（ｃ８）。定着ベルト２０の温度が所定温度に近づき、立ち上げ温調が終了（ｃ９）すると、プリント温調温度である１９０℃を目標温度に設定してＰＩＤ制御により目標温度に温調される（ｃ１０）。その後、記録材が定着ニップ部に突入する約０．５秒前まで、定着装置を駆動、温調した状態で待機させる（ｃ１１）。
【０２００】
定着ニップ部に記録材が突入する約０．５秒前を検知した時点で、ＰＩＤ制御を禁止し、ｃ５で決定された空回転オフセット電力（Ｗ）とｃ８で決定された通紙時オフセット電力（Ｗ）との和の電力（Ｗ）を出力し（ｃ１２）、記録材突入後から約０．５秒後まで継続して、この電力を印加しつづける（ｃ１３）。その後、プリント温調温度である１９０℃を目標温度に設定してＰＩＤ制御を再開する（ｃ１４）。
【０２０１】
以上の動作をプリント終了まで継続し（ｃ１５）、プリントジョブが終了すると同時に、温調制御が終了する（ｃ１６）。
【０２０２】
以上、説明したように、記録材Ｐが定着ニップ部に突入するタイミングの前後一定時間ＰＩＤ制御を禁止し、定着ヒータに投入される電力を所定の値に補正して投入する際に、定着装置の蓄熱具合を考慮した略必要電力値に補正することによって、温度検知のむだ時間により、記録材Ｐ体定着ニップ部の突入した際に、定着ベルト２０の温度変動を生じることなく、より安定した温度制御を行うことができる。
【０２０３】
本実施の形態においては、定着器の室温状態から、耐久中の高温状態までの幅広い条件において通紙時に投入する電力が精度良く決定できる為、さらに安定した温度制御を行うことができる。
【０２０４】
このようにして定着器の蓄熱具合によらず安定した温度制御（温度リップル約７℃）が達成できた。
【０２０５】
以上、本実施の形態では、記録材Ｐが定着ニップ部に突入するタイミング前後一定時間ＰＩＤ制御を禁止し、定着ヒータ１６に投入される電力を所定の電力に補正して投入する際に、定着装置の蓄熱具合を考慮した、略必要電力値に補正することによって、温度検知のむだ時間による通紙開始時の記録材Ｐの突入に伴う温度変動を生じることなく、より安定した温度制御を行うことができた。
【０２０６】
このように、温度リップルを小さく押さえることで、定着部材の正確な温調制御を行い、その結果良好な定着性を示し、定着温調温度が不適切な場合に発生する画像不良が無く、グロスなどの印字品質ムラのない高画質な画像を得ることができた。
【０２０７】
〈実施の形態４〉
本実施の形態では、録材Ｐが定着ニップ部に突入するタイミング前後に、ＰＩＤ制御を禁止し、定着ヒータ１６に投入される電力を所定の電力に補正して投入する際に、環境センサを用いて記録材Ｐの水分量の違いを考慮した略必要電力に補正することによって、記録材Ｐが定着ニップ部に突入した際に、定着ベルトの温度変動を生じることなく、より安定した温度制御を行う方法について説明する。
【０２０８】
本実施の形態では、定着装置の大まかな構成と制御は実施の形態３と同様である。しかし、定着ヒータ１６に投入される電力を補正する際に、記録材Ｐの環境放置状態による熱容量の違いを考慮した略必要電力に補正することが異なる。
【０２０９】
画像形成装置の構成は実施の形態１と同様であり図１に示すとおりである。また、定着装置の構成は、実施の形態１、２、３と同様で図２〜４に示した通りであり、重複する説明は省略する。
【０２１０】
本実施の形態では定着ヒータ１６に投入する電力を補正する際に、環境センサ５０により環境を検知することにより記録材Ｐの放置された環境による熱容量の違いを考慮した略必要電力に補正することにした。補正電力を考えるときに空回転オフセット電力補正分と通紙時オフセット電力補正分の和を補正電力として扱い、ここで通紙時オフセット電力を記録材Ｐの吸湿具合によって変動するものとし、高含水量環境（例えばＨ／Ｈ（３０℃／８０％Ｒｈ）環境）においてはより多くの電力を投入することとした。
【０２１１】
図９に３種類の環境における各坪量の放置紙を連続通紙したときに必要な電力を示す。条件は以下のとおりである。プロセススピードは８７ｍｍ／ｓｅｃ、１９０℃一定温調にて十分な時間が経過した状態で測定した。図９に示すように、Ｈ／Ｈ環境においては、各坪量の環境放置紙の連続通紙（１６枚／分）時の定着ヒータ１６に投入する、温度維持に必要な電力は、Ｌ／Ｌ（１５℃．１０％）環境放置紙やＪ／Ｊ（２４．５℃．４５％）環境放置紙の場合に比べて、約３０Ｗ大きいと言う傾向を示した。
【０２１２】
Ｈ／Ｈ環境放置紙において連続通紙（１６枚／分）時の定着ヒータ１６に投入する電力が大きくなるのは、紙が吸湿していることにより熱容量が大きくなっていることによる。
【０２１３】
本実施の形態は、高湿度環境放置紙を用いた場合の連続通紙時の定着ヒータ１６に投入する温度維持に必要な電力が、通常環境或いは低湿度環境放置しを用いた場合に比べて高いことに対応させる為に行うものである。
【０２１４】
表８に本実施の形態におけるペーパーモードと通紙時オフセット電力の関係を示す。
【０２１５】
【表８】

【０２１６】
図１３に、本実施の形態における、記録材Ｐが定着ニップ部に突入するタイミングの前後一定時間ＰＩＤ制御を禁止し、定着ヒータ１６に投入される電力を所定の値に補正して投入する際に、環境センサを用いて記録材Ｐの環境放置状態の違いを考慮して定着ヒータ１６に必要となる必要電力値と略同一になるよう投入電力を補正する方法についてのフローチャートを示す。
【０２１７】
以下にフローに従って、実際の補正動作について説明する。
【０２１８】
図１３において、画像形成装置は電源ＯＮ後にプリント信号を受信可能な状態に立ち上がる（ｄ１）。不図示のホストコンピュータからプリントコマンドを受信（ｄ２）すると、プリント信号からペーパーモードを読み取る（ｄ３）。そして、サブサーミスタ１９の温度Ｔａを検知する（ｄ４）。この検知温度Ｔａから、表７にしたがって、空回転オフセット電力（Ｗ）を決定する（ｄ５）。その後、環境センサ５０により画像形成装置の雰囲気環境の絶対水分量Ｘ（ｇ／ｋｇ：乾燥空気１ｋｇ中の水分量）を算出し、その絶対水分量が２１（ｇ／ｋｇ）以上であれば、高含水量環境、そうでなければ一般環境であると判別する（ｄ６）。その後、制御回路部２１はヒータ駆動回路２８を駆動することにより、定着ベルト２０を所定温度に温調すべく、ヒータ２１の立ち上げ温調制御を開始する（ｄ７）。その後、メディアセンサ５１により記録材Ｐが普通紙であるか、ラフ紙（伝熱性が低く、熱容量の小さい記録材）であるか、フィルムメディア（伝熱性が高く、熱容量の大きい記録材）であるかを判別する（ｄ８）。その後、プリンタ内の制御回路部（ＣＰＵ）２１は、表６、８に示すようにペーパーモードと記録材の性質（普通紙であるか、ラフ紙であるか、フィルムメディアであるか）、また雰囲気環境（高含水量環境であるか、一般環境であるか）に対応した通紙時オフセット電力（Ｗ）を決定する（ｄ９）。定着ベルト２０温度が所定の値に近づき、立ち上げ温調が終了（ｄ１０）すると、プリント温調温度である１９０℃を目標温度に設定してＰＩＤ制御により目標温度に温調される（ｄ１１）。その後、記録材が定着ニップ部に突入する約０．５秒前を検知するまで、定着装置は駆動、温調された状態で待機する（ｄ１２）。
【０２１９】
記録材が定着ニップ部に突入するの約０．５秒前を検知した後、ＰＩＤ制御を禁止し、ｄ５時に決定された空回転オフセット電力（Ｗ）とｄ８時に決定された通紙時オフセット電力（Ｗ）との和の電力（Ｗ）を投入し（ｄ１３）、記録材が定着ニップ部に突入した後約０．５秒経過するまで継続する（ｄ１４）。その後、プリント温調温度である１９０℃を目標温度に設定してＰＩＤ制御を再開し、定着ベルト２０温度は目標温度に温調される（ｄ１５）。
【０２２０】
プリント終了までＰＩＤ制御を継続し（ｄ１６）、プリントジョブ終了と同時に温調制御が終了する（ｄ１７）。この補正は、プリンタ内の制御回路部（ＣＰＵ）２１内に、サブサーミスタ１９の検知温度Ｔａと空回転オフセット電力（Ｗ）のテーブル（表７）と、ペーパーモードとメディアセンサ５１の判別結果による記録材の性質（普通紙であるか、ラフ紙であるか、フィルムメディアであるか）と雰囲気環境（高含水量環境であるか、一般環境であるか）をパラメータとして持つ、通紙時オフセット電力Ｅ２（Ｗ）決定用テーブル（表６、８）を備え、そのテーブルに基づいて行う。
【０２２１】
以上、説明したように、記録材Ｐが定着ニップ部に突入するタイミング前後一定時間ＰＩＤ制御を禁止し、定着ヒータ１６に投入される電力を所定の値に補正して投入する際に、環境センサを用いて記録材Ｐの環境放置状態の違いを考慮した略必要電力に補正することによって、記録材Ｐが定着ニップ部に突入した際の温度変動を生じることなく、より安定した温度制御を行うことができる。
【０２２２】
次に、本実施の形態を用いた場合の、定着ベルト２０温度挙動や、画質に対する効果を、従来例や実施の形態３との比較により示す。
【０２２３】
実験条件は次に示すとおりである。
【０２２４】
定着装置はプロセススピード８７ｍｍ／ｓｅｃで回転し、メインサーミスタ検知温度を１９０℃一定になるように温調され十分な時間が経過している。この状態で、通常の平滑紙として、坪量が６４ｇ／ｍ^２であるオフィスプランナー（Ｃａｎｏｎ販売、商品名）と、１０５ｇ／ｍ^２であるニューＮＰＩ上質紙１０５ｇ（日本製紙、商品名）というメディアのＪ／Ｊ（２４．５℃／４５％Ｒｈ）環境放置紙と、Ｈ／Ｈ（３０℃．８０％）環境放置紙を連続通紙（１６枚／分）した。
【０２２５】
この際に、定着スリーブ内面温度として、メインサーミスタ１８出力をモニターした。
【０２２６】
また、電力についてはＹＯＫＯＧＡＷＡ製ＷＴ２００　ＤＩＧＩＴＡＬ　ＰＯＷＥＲ　ＭＥＴＥＲを介して電力値の出力を同じくキーエンス製ＰＣ用温度レコーダーＮＲ２５０にてＡ／Ｄ変換しＰＣに取り込むことにより測定した。
【０２２７】
通紙前に定着ヒータ１６に投入される電力はそれぞれの条件において略同一であり、約８０Ｗであった。
【０２２８】
表９に従来の定着装置と実施の形態３、４における通紙前後での温度リップルを示す。
【０２２９】
【表９】

【０２３０】
表９から分かるように、本実施の形態を行うことによって、さらに安定した温度制御（温度リップル約７℃）が達成できた。
【０２３１】
これは次のような根拠による。
【０２３２】
十分に温まった定着装置の通紙前の空回転時において温度維持に必要な電力は約８０Ｗであり、Ｊ／Ｊ（２４．５℃．４５％）環境においてペーパーモードが普通紙のとき（６１〜１０５ｇ／ｍ^２）、このペーパーモードにおける通紙時オフセット電力を用いて電力補正を行うとき、投入される電力は２７５Ｗ（８０＋１９５Ｗ）である。一方、Ｈ／Ｈ（３０℃．８０％）環境放置紙であるＮＰＩ（１０５ｇ／ｍ^２）で連続通紙（１６枚／分）を行った場合、記録材の熱容量が大きい為、定着装置の温度維持に必要な電力はＪ／Ｊ環境放置紙を使用した場合より大きく、この差から温度リップルを生じてしまう。
【０２３３】
本実施の形態においては、高含水量環境でない場合の投入電力は２７５Ｗであるのに対し、高含水量環境であるＨ／Ｈ環境においては２９０Ｗ（８０＋２１０Ｗ）を投入することとした。
【０２３４】
上記制御により、記録材の放置環境を問わず、常に適切な電力補正が行われるため，所望の温度リップル（約７℃）での温度制御が達成できた。
【０２３５】
このように、本実施の形態においては、記録材Ｐの環境放置状態の違いを考慮して、記録材が定着ニップ部に突入する際に投入する電力を補正することによって、安定した温度制御（温度リップル約７℃）が達成できた。
【０２３６】
尚、Ｈ／Ｈ環境などの高含水量環境時はペーパーモードにおける通紙時オフセット電力を変更している。このとき、ペーパーモードの対応メディアにおいて必要な電力が厳密に一致していなくても、略同一であればよく、そのときの温度変動が所望の温度リップル内であれば良い。
【０２３７】
一般にプリントスピードが高速の場合においては、記録材Ｐの吸湿量の違いに伴う適切な通紙時オフセット電力の違いの差がさらに大きくなるため、高含水量環境時において、開直紙と放置紙を区別する必要が生じる場合がある。このような場合には記録材Ｐへの転写時における転写バイアスの情報などを利用して開直紙と放置紙を区別することにより、所望の温度リップル内での温度制御が可能である。以上、本実施の形態では、記録材Ｐが定着ニップ部に突入するタイミングの前後一定時間ＰＩＤ制御を禁止し、定着ヒータ１６に投入される電力を所定の電力に補正して投入する際に、環境センサを用いて記録材Ｐの環境放置状態の違いを考慮した略必要電力に補正することによって、記録材Ｐが定着ニップ部に突入する際の温度変動を生じることなく、より安定した温度制御を行うことができた。
【０２３８】
このように、温度リップルを小さく押さえることで、定着部材の正確な温調制御を行い、その結果良好な定着性を示し、定着温調温度が不適切な場合に発生する画像不良が無く、グロスなどの印字品質ムラのない高画質な画像を得ることができた。
【０２３９】
〈実施の形態５〉
本実施の形態においては、紙突入時だけでなく、前回転時においても固定電力を投入する区間を設け、前回転中の温度リップルを小さくすることにより、より安定した定着性能を確保する方法について説明する。
【０２４０】
（１）画像形成装置例
本実施の形態では、画像形成装置の構成は実施の形態１と同様であり図１に示すとおりである。よって、重複する説明は省略する。
【０２４１】
（２）定着装置１２
本実施の形態では、定着装置の構成は、実施の形態１、２、３と同様で図２〜４に示した通りであり、重複する説明は省略する。
【０２４２】
（３）定着装置の立ち上げ温度制御
図１８を用いて本実施の形態における定着装置の制御シーケンスについて説明する。本実施の形態においては、次のようにして立ち上げ温度制御を行っている。
【０２４３】
すなわち、「立ち上げ電力（第一電力レベル）出力」→「所定温度検知」→「一定電力（第二電力レベル）投入」→「ＰＩＤ制御」、である。
【０２４４】
「立ち上げ電力（第一電力レベル）」には、オンデマンド性を確保する為に、定着ヒータ１６には電力１０００Ｗが投入される。加圧ローラ２２の回転に伴い、定着ベルト２０は従動回転しながら定着ヒータ１６により加熱される。本実施の形態においては「立ち上げ電力（１０００Ｗ）」投入後、すぐには「ＰＩＤ制御」に移行せず、メインサーミスタ１８の検知温度が所定温度（目標温度−２０℃：本実施の形態では、目標温度は１９０℃であることから、１９０℃−２０℃＝１７０℃）に達したときに、約１．５秒間、「第二の電力レベルである所定電力（約２００Ｗ）」を投入した後に「ＰＩＤ制御」に移行し、以後は「ＰＩＤ制御」により定着ヒータ１６への投入電力は制御するようにした。
【０２４５】
図２２に本実施の形態における、立ち上げ温調中にフィードバック制御を禁止する領域を設け、前記領域内において、定着ヒータ１６に投入される電力に、定着装置温度をすみやかに立ち上げるための第一電力レベルと、定着装置温度を安定させるための第二電力レベルと、の二段階の電力レベルを用い、立ち上げ温調中に所定温度を検知した後に切り替える方法についてのフローチャートを示す。
【０２４６】
以下にフローに従って、実際の補正動作について説明する。
【０２４７】
図２２において、画像形成装置は電源ＯＮ後にプリント信号を受信可能な状態に立ち上がる（ｅ１）。不図示のホストコンピュータからプリントコマンドを受信（ｅ２）すると、制御回路部２１はヒータ駆動回路２８を駆動することにより、定着ベルト２０を所定温度に温調すべく、ヒータ２１の立ち上げ温調制御を開始する（ｅ３）。まず、立ち上げ電力（第一の電力レベル）として、１０００Ｗを投入する（ｅ４）。その後メインサーミスタ１８の温度をモニターし（ｅ５）、メインサーミスタ１８の検知温度が所定温度（目標温度−２０℃：本実施の形態では、目標温度は１９０℃であることから、１９０℃−２０℃＝１７０℃）を検知するまで定着装置を駆動させた状態で待機させる（ｅ６）。
【０２４８】
メインサーミスタ１８が所定温度を検知した時点で、第二の電力レベルである所定電力として２００Ｗが、定着ヒーター１６に投入される（ｅ７）。この電力は１．５秒間継続して投入され（ｅ８）、１．５秒経過したら、立ち上げ温調制御を終了して（ｅ９）、ＰＩＤ制御に移行する（ｅ１０）。以降は、実施の形態４と同様の制御（図１３、ｄ１１〜ｄ１７に記載されたものと同様。図２２中では、「通常温調」と表現した。）を行う。以上の動作をプリントが終了まで続け（ｅ１１）、プリントジョブが終了したら、温調制御が終了する（ｅ１２）。
【０２４９】
以上、説明したように、立ち上げ温調中にフィードバック制御を禁止する領域を設け、前記領域内において、定着ヒータ１６に投入される電力に、定着装置温度をすみやかに立ち上げるための第一電力レベルと、定着装置温度を安定させるための第二電力レベルと、の二段階の電力レベルを用い、立ち上げ温調中に所定電力を検知した後に、第一電力レベルから第二電力レベルに切り替えることによって、オーバーシュートや温度リップルを生じることなく、より安定した温度制御を行うことができる。
【０２５０】
次に、本実施の形態を用いた場合の定着装置の温度プロファイルと、定着性及び光沢度の測定結果を示す。
【０２５１】
本実験の内容は、次のとおりである。
【０２５２】
１）測定方法
定着装置の定着ベルト２０内面温度として、メインサーミスタ１８の出力をモニターした。
【０２５３】
また、電力についてはＹＯＫＯＧＡＷＡ製ＷＴ２００　ＤＩＧＩＴＡＬ　ＰＯＷＥＲ　ＭＥＴＥＲを介して電力値の出力をキーエンス製ＰＣ用温度レコーダーＮＲ２５０にてＡ／Ｄ変換しＰＣに取り込むことにより測定した。
【０２５４】
定着後画像の光沢度（グロス）については、次の方法を用いて測定を行った。測定器として、日本電色工業株式会社製の光沢度計ＰＧ−３Ｄを使用し、ＪＩＳＺ　８７４１における７５度鏡面光沢度測定方法により測定を行った。記録材上のトナー量としては、イエロー、マゼンタ、シアン、ブラックの、いわゆる１次色のべた画像部のトナー量が約０．５〜０．６ｍｇ／ｃｍ^２、レッド、グリーン、ブルーの、いわゆる２次色のべた部が約１．０〜１．２ｍｇ／ｃｍ^２の状態で定着を行い、定着後画像の光沢度を測定した。
【０２５５】
定着性を評価する為の擦り試験としては、記録材Ｐ上に５ｍｍ×５ｍｍの黒単色のべ夕画像を形成し、本実施の形態における定着装置を用いて５０枚連続して１６ｐｐｍの速度で定着し、その後、画像形成面上にシルボンＣ（商品名）を介して２００ｇのおもりを載せ、画像形成面を５往復摺擦させ、その摺擦の前後で画像の反射濃度の低下率（％）を求めた。この反射濃度の変化率（濃度低下率）が小さいほど定着性が良いと言える。測定には定着した５０枚の記録材のうち１，２，３，５，１０枚目で、９点の濃度低下率を測定して、その最悪値を用いた。
【０２５６】
２）実験条件
本実験において、定着装置は室温から立ち上げるものとする。定着装置は、動作を開始するのとほぼ同時に、定着ヒータ１６に第一の電力（１０００Ｗ）が投入され、メインサーミスタ１８の検知温度が目標温度１７０℃（目標温度（１９０℃）−２０℃）になるまでこの電力を投入した。
【０２５７】
メインサーミスタ１８の検知温度が１７０℃に達した時点で約１．５秒間ＰＩＤ制御を禁止し、第二の電力（約２００Ｗ）を投入する。第二の電力投入から１．５秒後に、立ち上げの目標温度を１９０℃として、ＰＩＤ制御を再開し、目標温度で一定になるように温調を行った。その後、坪量が７５ｇ／ｍ^２であるゼロックス４０２４（Ｘｅｒｏｘ、商品名）という記録材を連続通紙した。
【０２５８】
尚、投入した約２００Ｗの電力は空回転状態で１９０℃温調を行う為に必要な電力、つまりは目標温度での温度維持に必要な電力値である。
【０２５９】
また、耐久試験として、本実施の形態における定着装置を用い、２枚間欠の連続印字を１５万枚行い、耐久後の加圧ローラのトルクを測定した。
【０２６０】
３）実験結果
図１９に本実施の形態を用いた場合の定着装置における立ち上げ温調での定着ヒータ１６に投入する電力と定着ベルト２０内面の温度挙動をあらわすグラフを示す。
【０２６１】
図１９に示すように立ち上げによるオーバーシュートも含めて安定した温調（温度リップル約７℃、目標温度に対して±３．５℃）を示した。
【０２６２】
温度リップルが約７℃の場合には、試験に用いたインライン型の電子写真方式カラー画像形成装置においては、出力された印刷物のグロスは単色で約４の変動幅であり、また、２次色では約６の変動幅と小さかった（表１０）。
【０２６３】
【表１０】

【０２６４】
また、耐久試験として、坪量７５ｇ／ｍ^２、ＵＳレターサイズのゼロックス４０２４紙を１５万枚、２枚間欠でプリントした。定着性の濃度低下率の最悪値は１３％であり、各測定ポイントでのばらつきも少なく、安定した良好な定着性を得ることができた。
【０２６５】
さらに、目標温度に近いところで定着できる為、記録材や印字パターンによらずホットオフセットなどの定着不良が生じることなく高品質な画像を得ることができた。
【０２６６】
また、耐久試験後の、駆動トルクを測定したところ約３．０ｋｇｆ・ｃｍであった。このとき定着装置の不具合は見られなかった。
【０２６７】
（４）比較例２
図２０を用いて比較例における定着装置の立ち上げ時の制御シーケンスについて説明する。
【０２６８】
本比較例においては、「立ち上げ電力（１０００Ｗ）出力」→「所定温度（１７０℃）検知」→「ＰＩＤ制御」、という立ち上げ制御を行っている。すなわち、定着ヒータ１６に、第一の電力（１０００Ｗ）を投入し、メインサーミスタ１８の検知温度が１７０℃に達した時点で、立ち上げの目標温度を１９０℃として、ＰＩＤ制御に移行し、第二の電力を投入する区間を持たないことを特徴とする。
【０２６９】
このとき、図２１に示すように、ＰＩＤ制御中にオーバーシュートが発生し、また、オーバーシュートに伴う温度リップルも大きくなってしまう。
【０２７０】
本比較例の定着装置を用いた場合における定着ベルト温度挙動測定、定着性評価、および耐久試験結果を示す。
【０２７１】
１）実験方法
実施の形態５における定着装置を用いた実験と同様にして行ったのでここでは省略する。
【０２７２】
２）実験条件
室温状態である定着装置は、動作するのとほぼ同時に定着ヒータ１６に、第一の電力（１０００Ｗ）が投入され、メインサーミスタ１８の検知温度が目標温度１７０℃になるまで第一の電力を投入した。その後、第二の電力投入は行わず、目標温度を１９０℃としたＰＩＤ制御に移行する。その後、坪量が７５ｇ／ｍ^２であるゼロックス４０２４（Ｘｅｒｏｘ、商品名）というメディアを連続通紙（１６枚／分）した。
【０２７３】
また、実施の形態５で説明したものと同様の耐久試験を実施した。
【０２７４】
３）実験結果
図２１に従来例における立ち上げ温調での定着ヒータ１６に投入する電力と定着ベルト２０裏面の温度挙動をあらわすグラフを示す。
【０２７５】
図２１に示すように、定着ベルト２０裏面温度は、約９秒で所望の温度に立ち上がるものの、その後オーバーシュートを起こし、約２１０℃まで温度が上昇した。その後、定着ベルト２０裏面温度は、上下動を繰り返し、目標温度である１９０℃に対して温度リップル７℃以内で安定するまでに、さらに１０秒程度を要した。
【０２７６】
このようなオーバーシュートを生じた場合、試験に用いたインライン型の電子写真方式カラー画像形成装置においては、出力された印刷物のグロスは一枚の出力紙内で、単色で約８変動し、また、２次色では約１３変動し、画質の低下を招いた（表１１）。
【０２７７】
【表１１】

【０２７８】
また、定着性の濃度低下率の最悪値は２２％であった。濃度低下率が２０％を超えるような場合には、画像をユーザーが使用している時に、文字がはがれたり、ハーフトーンの画像がぼやけてしまうばかりでなく、手や衣服やほかの紙が汚れたりする等の問題が発生した。
【０２７９】
さらに、オーバーシュートの途中で紙が通紙された場合、記録材や印字パターンによらずホットオフセットなどの定着不良が生じてしまうという問題を生じた。
【０２８０】
また、耐久試験後の定着装置の駆動トルクを測定したところ約４．５ｋｇｆ・ｃｍであった。このとき、条件によっては定着装置の駆動中に定着ベルトのスリップが発生することがあった。
【０２８１】
（５）考察
まず、オーバーシュートと温度リップルについて述べる。
【０２８２】
本実施の形態を用いた場合に効果の得られる理由は次のようである。従来の定着装置においては、定着ベルト２０の弾性層に用いられるシリコーンゴムの熱伝導率が小さく、熱容量が大きいため、定着ヒータ１６の昇温に対する定着ベルト２０の温度応答性が悪い。また、メインサーミスタ１８の位置が発熱部である定着ヒータ１６から離れていることによる検知タイミングの遅れがあることから、立ち上げ時のように、温度が急激に上昇する場合には、メインサーミスタ１８の検知温度は、定着ニップ部の温度を大きく下回る値を示すこととなる。そのため、定着ヒータ１６の温度が実際には十分昇温しているにも関わらず、メインサーミスタ１８の検知温度は十分上昇していない為、高い電力が投入されつづけることとなり、オーバーシュートを生じる。
【０２８３】
また、一旦オーバーシュートを生じると、メインサーミスタ１８が、一定のタイムラグの後、所望の温度より高いことを検知し、電力を抑える制御を行う。このとき、電力を抑えて、定着ヒータ１６の発熱量を小さくし、定着ニップ部の温度が適正となっても、メインサーミスタ１８は、検知温度が高いと認識してしまう。このため、必要以上に電力を抑えることとなってしまい、アンダーシュートを生じる。このオーバーシュート、アンダーシュートの繰り返しが、温度リップルとなって現れる。
【０２８４】
さらに本定着装置においては、温度の応答性が悪い定着ベルト２０を用いた状態でオンデマンド性を確保するべく、立ち上げ電力に大きな電力（１０００Ｗ）を用いる為に、その後すぐさまＰＩＤ制御などのフィードバック制御に戻った場合、電力の変動幅が大きく、温度変動の大きい不安定な制御となる。
【０２８５】
ここで、立ち上げ電力投入後、メインサーミスタ１８の検知温度が所定温度（目標温度−２０℃）に達したときに、約１．５秒間所定電力（約２００Ｗ）を投入することで、ＰＩＤ制御に移行する際の電力変動を比較的緩やかにすることにより、オーバーシュートを小さくし、また、オーバーシュートに伴う温度リップルも小さくすることができる。
【０２８６】
次に、定着部材の耐久性について述べる。
【０２８７】
従来例のように立ち上げにおいて定着スリーブ２０内面温度が約２１０℃まで達する場合、定着ヒータ１６と定着ベルト２０内面の間に介在するグリスが、急速に劣化する。定着ベルト２０と、定着ヒータ１６をはじめとするベルト内部の構成物との動摩擦力は、特にグリスの状態に大きく影響され、グリスが不必要な部位に移動することにより量が減少した場合や、グリス自体が劣化した場合には、この動摩擦力が大きくなることが知られている。
【０２８８】
このため、定着装置の耐久が進むと、定着装置のトルクが上昇し、最悪の場合、定着ヒータ１６をはじめとするベルト内部の構成物との動摩擦力が、加圧ローラ２２、もしくは記録材Ｐとの最大静止摩擦力を超え、定着ベルト２０のスリップが発生してしまう。
【０２８９】
定着ベルト２０と、定着ヒータ１６をはじめとするベルト内部の構成物との動摩擦力は、定着装置の駆動時における、駆動手段への負荷のなかでも最も大きな要因である。即ち、定着装置の駆動トルクを測定値によって、代用することができる。
【０２９０】
この定着装置の初期状態における駆動トルクは約１．５ｋｇｆ・ｃｍであり、定着ベルト２０のスリップは、この駆動トルクが約４．０ｋｇｆ・ｃｍを超えるとで発生する場合があることが分かっている。
【０２９１】
実施の形態５および比較例２においては、耐久寿命が短くなる顕著なものとして、定着ベルト２０のスリップを例として挙げたが、定着装置のオーバーシュートが大きい場合には、定着装置内の各部材に過度の負担を強いることから、本実施の形態を用いてオーバーシュートを防止することで、定着装置内の各部材の寿命を伸ばす効果があることは言うまでもない。
【０２９２】
尚、実施の形態５で説明した、第二の電力の値（約２００Ｗ）は定着装置の空回転状態で安定して１９０℃温調を維持する為に必要な電力であり、実験的に求めたものである。ただし、ここで投入する電力は、必要電力と厳密に一致していなくても、略同一であればよい。すなわち、第二電力を投入し、定着装置温度が安定した後はＰＩＤ制御によっても大幅な電力変動は生じない為、温度リップルを小さくすることができる。
【０２９３】
以上、本実施の形態では、立ち上げ温調中にフィードバック制御を禁止する領域を設け、前記領域内において、定着ヒータ１６に投入される電力に、定着装置温度をすみやかに立ち上げるための第一電力レベルと、定着装置温度を安定させるための第二電力レベルと、の二段階の電力レベルを有し、第一の電力を投入した立ち上げ温調中に所定温度を検知した際に、第二の電力に切り替え、定着装置温度が安定した状態でフィードバック制御に復帰することによって、オーバーシュートを生じることなく、より安定した温度制御を行うことができた。
【０２９４】
このように、オーバーシュートとそれに伴う温度リップルを小さく押さえることで、定着装置の寿命が長く、また、定着部材の正確な温調制御を行い、その結果良好な定着性を示し、定着温調温度が不適切な場合に発生する画像不良が無く、グロスなどの印字品質ムラのない高画質な画像を得ることができた。
【０２９５】
〈実施の形態６〉
本実施の形態では、立ち上げ温調中にフィードバック制御を禁止する領域を設け、前記領域内において、定着ヒータ１６に投入される電力に、定着装置温度をすみやかに立ち上げるための第一電力レベルと、定着装置温度を安定させるための第二電力レベルと、の二段階の電力レベルを有し、第一電力レベルでの立ち上げ温調中に所定温度を検知した際、第二電力レベルに切り替えることを特徴とする定着装置において、第二電力レベルを、立ち上げ前のサブサーミスタ１９の検知温度に基づいて補正することによって、オーバーシュートを生じることなく、より安定した温度制御を行う方法について説明する。
【０２９６】
本実施の形態では、定着装置の大まかな構成と制御は実施の形態５と同様である。しかし、定着ヒータ１６に投入される電力を補正する際に、定着装置の蓄熱具合を考慮した略必要電力に補正することが異なる。
【０２９７】
画像形成装置の構成は実施の形態１と同様であり、図１に示すとおりである。また、定着装置の構成は、実施の形態１と同様で図２〜４に示した通りである。よって重複する説明は省略する。
【０２９８】
本実施の形態では、立ち上げ温調中に定着ヒータ１６に投入する第二の電力レベルを補正する際に、定着装置の蓄熱具合を考慮した略必要電力に補正することとした。
【０２９９】
つまりは、立ち上げ温調中に所定温度を検知した後において、定着装置を目標温度で温度維持するのに必要な、第二の電力レベルを、定着装置の蓄熱具合によって変動するものとした。例えば、室温状態からの定着装置の立ち上げ電力投入後、所定温度を検知した際に、定着装置を目標温度に維持するのに必要な第二の電力レベルが約２００Ｗ、また十分に温まった定着装置を立ち上げた際に、定着装置を目標温度に維持するのに必要な第二の電力レベルが約８０Ｗであることから、定着装置の蓄熱具合を考慮し、定着装置の蓄熱具合によって定着ヒータ１６に投入すべき電力が異なる状況に対応できるようにした。
【０３００】
本実施の形態においては、通電開始時のサブサーミスタ１９の検知温度から定着装置の蓄熱具合を予想し、所定電力値を変更することとした。
【０３０１】
図１６にヒータホルダ１７の温度と定着装置の温度を所定の値に維持するのに必要な電力の値との関係をプロットしたグラフを示す。このように、ヒータホルダ温度と、定着装置の温度を所定の値に維持するのに必要となる電力の値は再現良く図１６に示すような関係を示す。
【０３０２】
【表１２】

【０３０３】
そこで、本実施の形態においては、プリントジョブ終了後、定着装置に余熱が残った状態で再び立ち上げる場合には、通電開始時のサブサーミスタ１９の検知温度に応じて表１２に示すように、立ち上げ後のヒータホルダ１７の温度を予想し、第二電力レベルの値を決定している。
【０３０４】
具体的には、通電開始時のサブサーミスタ１９の検知温度が４０℃以下であるときには立ち上げ後のヒータホルダ温度が５５℃以下であることが予想される為、立ち上げ１として、第二電力レベルの値として、２００Ｗを用いる。
【０３０５】
以下同様にして、立ち上げ開始前のサブサーミスタ検知温度が４１〜５５℃であるときには立ち上げ２とし、５６〜７５℃であるときには立ち上げ３であるとし、７６〜９５℃であるときには立ち上げ４であるとし、９６〜１２５℃であるときには立ち上げ５であるとし、１２６℃以上であるときには立ち上げ６であるとして、第二電力レベルの値を決定する。
【０３０６】
図２３に本実施の形態における、立ち上げ温調中にフィードバック制御を禁止する領域を設け、前記領域内において、定着ヒータ１６に投入される電力に、定着装置温度をすみやかに立ち上げるための第一電力レベルと、定着装置温度を安定させるための第二電力レベルと、の二段階の電力レベルを有し、立ち上げ温調中に所定温度を検知した後に第一電力レベルから、第二電力レベルに、投入電力レベルを切り替える際に、第二電力レベルを、立ち上げ前のサブサーミスタ１９の検知温度に基づいて、定着装置の蓄熱具合を考慮した必要電力値に補正する方法についてのフローチャートを示す。
【０３０７】
以下にフローに従って、実際の補正動作について説明する。
【０３０８】
図２３において、画像形成装置は電源ＯＮ後にプリント信号を受信可能な状態に立ち上がる（ｆ１）。不図示のホストコンピュータからプリントコマンドを受信（ｆ２）すると、まず、サブサーミスタの温度Ｔａを検知して（ｆ３）、サブサーミスタの検知温度の結果からテーブル（表１２）に従い所定電力（第二の電力レベル）（Ｗ）を決定する（ｆ４）。その後、制御回路部２１はヒータ駆動回路２８を駆動することにより、定着ベルト２０を所定温度に温調すべく、ヒータ２１の立ち上げ温調制御を開始する（ｆ５）。まず、立ち上げ電力（第一の電力レベル）として、１０００Ｗを投入する（ｆ６）。その後メインサーミスタの温度をモニターし（ｆ７）、メインサーミスタ１８の検知温度が所定温度（目標温度−２０℃：本実施の形態では、目標温度は１９０℃であることから、１９０℃−２０℃＝１７０℃）を検知するまで待つ（ｆ８）。
【０３０９】
メインサーミスタ１８の検知温度が所定温度になると、次に、ｆ４で決定した第二の電力レベルを出力する（ｆ９）。この動作を１．５秒間継続した後（ｆ１０）、立ち上げ温調制御が終了して（ｆ１１）、ＰＩＤ制御に復帰し、目標温度での温調が行われる（ｆ１２）。以降、通常温調制御（図１３、ｄ１１〜ｄ１７に記載されたものと同様の制御）をプリント終了まで続け（ｆ１３）、プリントジョブが終了したら、温調制御が終了する（ｆ１４）。
【０３１０】
以上、説明したように、立ち上げ温調中にフィードバック制御を禁止する領域を設け、前記領域内において、定着ヒータ１６に投入される電力に、定着装置温度をすみやかに立ち上げるための第一電力レベルと、定着装置温度を安定させるための第二電力レベルと、の二段階の電力レベルを有し、立ち上げ温調中に所定温度を検知した後に、第一電力レベルから、第二電力レベルに切り替える際に、第二電力レベルを、立ち上げ前のサブサーミスタ１９の検知温度に基づいて、定着装置の蓄熱具合を考慮した必要電力値に補正することによって、オーバーシュートを生じることなく、より安定した温度制御を行うことができる。
【０３１１】
本実施の形態を用いた場合の効果については、原理的に実施の形態１と同様であるため、ここでは省略する。しかし、本実施の形態においては、室温状態の定着装置から十分に暖まった状態の定着装置まで幅広い条件の定着装置において立ち上げ時に投入する電力が精度良く決定できる為、さらに安定した温度制御を行うことができる。
【０３１２】
このようにして定着装置の蓄熱具合によらず安定した温度制御（温度リップル約７℃以内）が達成できた。
【０３１３】
このように、オーバーシュートとそれに伴う温度リップルを小さく押さえることで、定着装置の寿命が長く、また、定着部材の正確な温調制御を行い、その結果良好な定着性を示し、定着温調温度が不適切な場合に発生する画像不良が無く、グロスなどの印字品質ムラのない高画質な画像を得ることができた。
【０３１４】
また、ここでは立ち上げ前のサブサーミスタ１９の検知温度を用いて、ヒータホルダ温度を予測し、所定電力値を決定したが、サブサーミスタを使わず、印字枚数数からヒータホルダ温度を予測し、所定電力値を決定する方法を用いても良い。
【０３１５】
〈実施の形態７〉
本実施の形態では、立ち上げ温調中にフィードバック制御を禁止する領域を設け、前記領域内において、定着ヒータ１６に投入される電力に、定着装置温度をすみやかに立ち上げるための第一電力レベルと、定着装置温度を安定させるための第二電力レベルと、の二段階の電力レベルを用い、立ち上げ温調中に所定温度を検知した後に第一電力レベルから、第二電力レベルへ切り替える際に、第二電力レベルは、ヒータホルダ１７に当接させたサーミスタの検知温度に基づいて、定着装置の蓄熱具合を考慮した必要電力値に補正されることによって、オーバーシュートを生じることなく、さらに安定した温度制御を行う方法について説明する。
【０３１６】
本実施の形態では、定着装置の大まかな構成と制御は実施の形態１と同様であるが、図１７に示すように、ヒータホルダ１７内には第三の温度検知手段としての第三のサーミスタ７０が設置されている。定着ヒータ１６に投入される電力を補正する際に、第三のサーミスタ７０を利用して、定着装置の蓄熱具合を考慮した略必要電力値に補正することが異なる。
【０３１７】
画像形成装置の構成は実施の形態１と同様であり、図１に示すとおりである。また、定着装置の構成は、先述したように図２〜４に示した通りである。よって重複する説明は省略する。
【０３１８】
本実施の形態では定着装置の蓄熱具合を考慮する際に、ヒータホルダ１７に当接した第三のサーミスタ７０を用いて蓄熱具合を直接測定することとした。
【０３１９】
このようにする事によって、定着装置の蓄熱具合をより精度よく求めることができる。
【０３２０】
図１６にヒータホルダ１７の温度と、定着装置温度を維持するために必要な、電力値との関係をプロットしたものを示す。このように、ヒータホルダ温度と、定着装置の温度維持に必要となる所定電力値は再現良く図７に示すような関係を示す。
【０３２１】
第三のサーミスタ７０の検知温度から、図１６において線形補間により決定された所定電力値を用いることによって、さらに精度よく必要電力値を求めることができる。
【０３２２】
本実施の形態を用いた場合の効果については、原理的に実施の形態６と同様であるため、ここでは省略する。しかし、本実施の形態においては、室温状態の定着装置から十分に暖まった状態の定着装置まで幅広い条件の定着装置において、立ち上げ時に投入する第二電力レベルの値がさらに精度良く決定できる為、非常に安定した立ち上げ温度制御を行うことができる。
【０３２３】
このようにすることによって、定着装置の蓄熱具合によらず安定した立ち上げ温度制御（温度リップル約７℃以内）が達成できた。
【０３２４】
このように、オーバーシュートとそれに伴う温度リップルを小さく押さえることで、定着装置の寿命が長く、また、定着部材の正確な温調制御を行い、その結果良好な定着性を示し、定着温調温度が不適切な場合に発生する画像不良が無く、グロスなどの印字品質ムラのない高画質な画像を得ることができた。
【０３２５】
〈その他〉
１）このように、上述した実施の形態１〜４において、プロセススピードは８７ｍｍ／ｓｅｃ、プリントスピードは１６枚／分、温調温度は１９０℃、所定電力の投入時間は通紙開始時の記録材突入前の約０．５秒から約１秒間として説明した。しかし、記録材の種類や得たい画像の画質によっては、もしくはより良好な定着性を得る為などの条件によっては、プロセススピードやプリントスピード、温調温度、を異なる設定にしたほうが良い場合が考えられる。このような場合においても、本発明法を適用することによって、温度変動の小さい精度の良い温調を行うことが可能であり、同様の効果が得られる。このとき、補正される所定電力の値と所定電力の投入時間は、プロセススピード、プリントスピード、温調温度によって異なることは言うまでもない。
【０３２６】
２）また、上述した各実施の形態において、温度制御を行う為の電力制御として基本的にＰＩＤ制御を用いる場合について説明した。これは目標温度に素早く近づけ、尚且つ外乱に対しても強い制御方法として用いたものである。よって、Ｐ制御、ＰＩ制御、またその他のフィードバック制御を用いても温度制御を行うことができ、同様の効果が得られる。
【０３２７】
３）また、上述した実施の形態１〜７において、記録材の熱容量や定着装置からの伝熱性の違いを考慮して所定電力の値を決定するために、ペーパーモードや、メディアセンサ、環境センサを用いて説明した。が、実際に定着装置に記録材が突入する前に記録材の熱容量や定着装置からの伝熱性の違いを直接測定する方法を用いて、その結果を所定電力の値に反映することによっても本発明を適用することができ、同様もしくは温度制御の点では更に精度の良い温度制御を行うことができる。
【０３２８】
４）また、上述した実施の形態１〜４において、定着装置の蓄熱具合を考慮して所定電力の値を決定するために、定着装置の印字枚数や、通電開始時のサブサーミスタ１９の温度を用いて説明しが、実際に定着装置内、例えばヒータホルダ１７や加圧ローラ２２に新たなサーミスタを追加し、定着装置の蓄熱具合を直接測定する方法を用いても本発明を適用することができ、同様もしくは温度制御の点では更に精度の良い温度制御を行うことができる。
【０３２９】
５）また、上述した実施の形態５〜７において、プロセススピードは８７ｍｍ／ｓｅｃ、温調温度は１９０℃、所定電力の投入時間はメインサーミスタ１８の検知温度が１７０℃（目標温度−２０℃）の後で、約１．５秒として説明した。しかし、記録材の種類や得たい画像の画質によっては、もしくはより良好な定着性を得る為などの条件によっては、プロセススピードやプリントスピード、温調温度、を異なる設定にしても、本発明を適用することによって、温度変動の小さい精度の良い温調制御を行うことが可能である。このとき、補正される所定電力の値と所定電力の投入時間は、プロセススピード、温調温度によって異なることは言うまでもない。
【０３３０】
６）また、上述した実施の形態５〜７において、立ち上げ電力制御は２段階の制御として説明したが、３段階以上の制御を用いても差し支えない。この場合は、電力値の設定等、より精密な制御が可能となり、より安定した温調制御が可能となる。
【０３３１】
７）また、上述した各実施の形態において、定着ヒータ１６に供給する電力を、それぞれの条件に好適な定着装置に必要な所定電力で補正する制御として説明したが、この制御を擬似的に達成する方法として、温調時の目標温度を一時的に変更して定着ヒータ１６に供給する電力が結果的に定着装置に必要な所定電力となるように目標温度の変更で補正してもよい。つまり、上述した実施の形態１〜４において、記録材Ｐが定着ニップ部に突入する約０．５秒前から約１秒間メインサーミスタ１８、もしくはサブサーミスタ１９の目標温度を記録材Ｐが突入する前の状態より高く設定して、結果的に定着装置を所定温度に維持するのに必要な電力が投入されるように制御する方法や、上述した実施の形態５〜７において、メインサーミスタ１８の検知温度が１７０℃（目標温度−２０℃）に到達した後で、約１．５秒間目標温度を高く設定し、結果的に定着装置を所定温度に維持するために必要な電力が投入されるように制御する方法を用いてもよく、同様の効果が得られる。
【０３３２】
８）また、上述した各実施の形態において、定着装置の第一の温度検知手段は加熱体とは異なる場所にあるものとして説明したが、第一の温度検知手段が加熱体上にあったとしても、例えば、発熱領域と異なる場所にある場合や、温度検知手段の応答性が遅い場合においても、同様の効果が得られる。
【０３３３】
９）また、上述した各実施の形態において、定着ベルト２０の熱容量は少なくとも４．２×１０^−２Ｊ／ｃｍ^２・℃以上４．２Ｊ／ｃｍ^２・℃のもので構成される定着装置を用いて説明した。これは、定着ベルト２０の熱容量が４．２×１０^−２Ｊ／ｃｍ^２・℃以上の場合にはオンデマンド性が損なわれ、定着ベルト２０の熱容量が４．２Ｊ／ｃｍ^２・℃以下の場合には、定着ベルト２０の弾性層厚みが十分確保できず、光沢ムラ等の画像不良が現れるためである。しかしながら、上記以外の熱容量を有する定着ベルトを有する定着装置であっても本発明を適用することができ、同様の効果が得ることが可能である。
【０３３４】
１０）また、本発明の実施の形態においては、定着ベルト２０に弾性層を設けた定着装置について説明した。しかしながら、定着部材が実施の形態中で説明した程度の熱容量を持つ定着装置であれば、弾性層の有無は特に問わない。
【０３３５】
１１）また、加熱体としてセラミック基板上に抵抗発熱体を形成してなるセラミックヒータを用いる定着装置において説明した。これはローコストなカラー用オンデマンド定着装置の加熱体として用いる為であり、加熱体にハロゲンランプや電磁誘導発熱部材を用いることもでき、同様の効果が得られる。
【０３３６】
１２）また、定着ニップを形成させる第一と第二の定着部材は、実施の形態１ないし７の定着ベルトや加圧ローラの形態に限られるものではない。第一と第二の定着部材の両方に加熱体（熱源）を具備させた形態の装置にすることもできる。
【０３３７】
１３）また、加熱体は必ずしも定着ニップ部２７に位置していなくてもよい。例えば、熱源を定着ニップ部２７よりも定着ベルト移動方向上流ないし下流側に位置させて配設することも出来る。
【０３３８】
１４）また、実施例の定着装置は加圧用回転体駆動方式であるが、エンドレスの定着ベルトの内周面に駆動ローラを設け、定着ベルトにテンションを加えながら駆動する方式の装置であってもよい。
【０３３９】
１５）また、本発明において定着装置には、未定着画像を記録材上に永久画像として加熱定着させる定着装置ばかりでなく、未定着画像を記録材上に仮定着させる像加熱装置、画像を担持した記録材を再加熱して、光沢等の画像表面性を改質する像加熱装置なども包含される。
【０３４０】
１６）また、画像形成装置の作像方式は電子写真方式に限られず、静電記録方式、磁気記録方式等であってもよいし、また転写方式でも直接方式でもよい。
【０３４１】
【発明の効果】
以上説明したように、本発明によれば、定着装置において定着部材として弾性層を有する定着ベルトを用いた場合でも定着部材の正確な温調制御を行い、その結果グロスなどの印字品質ムラのない高画質な画像を得ることができ、また耐久性が高く高寿命な定着装置、および該定着装置を搭載した画像形成装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態におけるカラー画像形成装置の概略構成図
【図２】本発明の第一ないし七の実施の形態における定着装置の断面模式図
【図３】本発明の第一ないし七の実施の形態における定着ヒータ・メインサーミスタ・サブサーミスタの位置関係を示す斜視模型図
【図４】加熱体としてのセラミックヒータの構成模式図
【図５】本発明の定着装置の制御回路部（ＣＰＵ）と定着ヒータ駆動回路部のブロック図
【図６】従来の定着装置を用いてメディアの通紙前後の温度変化と投入電力のグラフ
【図７】本発明の第一の実施の形態における定着装置を用いてメディアの通紙前後の温度変化と投入電力のグラフ
【図８】メディアセンサを示す概略構成図
【図９】各環境放置紙を連続通紙する際に必要となる電力のグラフ
【図１０】本発明の第一の実施の形態における、記録材Ｐの坪量による熱容量の違いを考慮した定着ヒータ１６に必要となる必要電力値と略同一に補正する方法についてのフローチャート
【図１１】メディアセンサを用いて定着装置からの伝熱性が特殊な記録材Ｐを検知し、その伝熱性を考慮して定着ヒータ１６に必要となる必要電力値と略同一に補正する方法についてのフローチャート
【図１２】定着装置の蓄熱具合を考慮した定着ヒータ１６に必要となる必要電力値と略同一に補正する方法についてのフローチャート
【図１３】環境センサを用いて記録材Ｐの環境放置状態の違いを考慮して定着ヒータ１６に必要となる必要電力値と略同一に補正する方法についてのフローチャート
【図１４】従来の定着装置における立ち上げ温調での定着ヒータに投入する電力と定着ベルトの温度を示す図
【図１５】本発明の第四の実施の形態における定着装置における立ち上げ温調での定着ヒータに投入する電力と定着ベルトの温度を示す図
【図１６】ヒータホルダの温度と所定電力値の関係をプロットした図
【図１７】本発明の第七の実施の形態における定着装置の断面模式図
【図１８】本発明の第四の実施の形態における定着装置の立ち上げ電力制御図
【図１９】本発明の実施の形態における定着装置の立ち上げ温度プロファイル図
【図２０】従来の定着装置の立ち上げ電力制御図
【図２１】従来の定着装置の立ち上げ温度プロファイル図
【図２２】通紙開始時の記録材Ｐの突入タイミングとあわせて、一定時間ＰＩＤ制御を行わず、定着ヒータに投入される電力を所定の値に補正して投入する際に、環境センサを用いて記録材Ｐの環境放置状態の違いを考慮して定着ヒータ１６に必要となる必要電力値と略同一に補正する方法についてのフローチャート
【図２３】環境センサを用いて記録材Ｐの環境放置状態の違いを考慮して定着ヒータ１６に必要となる必要電力値と略同一に補正する方法についてのフローチャート
【図２４】従来のベルト定着方式の定着装置の断面模式図
【図２５】従来のベルト定着方式において定着ベルト内面当接型のサーミスタを用いた定着装置の断面模式図
【符号の説明】
１Ｍ、１Ｃ、１Ｙ、１Ｂｋ　画像形成部
２ａ、２ｂ、２ｃ、２ｄ　感光ドラム
３ａ、３ｂ、３ｃ、３ｄ　帯電ローラ
４ａ、４ｂ、４ｃ、４ｄ　現像装置
５ａ、５ｂ、５ｃ、５ｄ　転写ローラ
６ａ、６ｂ、６ｃ、６ｄ　ドラムクリーニング装置
１２　定着装置
１６　セラミックヒータ（加熱体）
１８　メインサーミスタ（第一の温度検知手段）
１９　サブサーミスタ（第一の温度検知手段）
２０　定着ベルト（第一の回転体）
２１　制御回路部（電力制御部）
２２　加圧ローラ（第二の回転体）
２８　電源（電力供給部）
４０　中間転写ベルト
４４　２次転写ローラ
４５　ベルトクリーニング装置
４６　レジストローラ
５０　環境センサ
５１　メディアセンサ
Ｐ　記録材
Ｎ　（１次）転写部
Ｍ　（２次）転写部
ｔ　トナー[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing device and an image forming device.
[0002]
More specifically, at least a heating body, a power supply unit (heating means) for supplying power to the heating body, at least one or more temperature detecting means, a first rotating body that moves together with a recording material, A second rotating body that forms a pressure-contact portion with the recording material, and the power supplied from the power supply unit to the heating body is feedback-controlled based on the temperature detected by the temperature detection unit, and A fixing device for controlling the temperature of the first rotating body, holding and conveying the recording material carrying the image in the press-contact portion and heating the same, and including the fixing device, for example, an electrophotographic copying machine, a printer, The present invention relates to an image forming apparatus such as a facsimile.
[0003]
[Prior art]
2. Description of the Related Art In recent years, colorization in image forming apparatuses such as printers and copiers has been advanced. As a fixing device used in such a color image forming apparatus, a heat roller type fixing device having an elastic layer on a fixing member is well known.
[0004]
However, in the heat roller type fixing method having an elastic layer, the heat capacity of the heat roller itself becomes large, and the time required for raising the temperature of the fixing roller to a temperature suitable for fixing the toner image (warm-up time) ) Was long. Further, the cost of the fixing device has been expensive.
[0005]
As a fixing device having a short warm-up time, a fixing device of a belt fixing type often used in a black and white image forming apparatus is well known. FIG. 24 shows a schematic configuration model diagram of an example of such a belt fixing device.
[0006]
Reference numeral 201 denotes the overall reference number of the belt fixing device of the present embodiment. Reference numeral 202 denotes a fixing belt unit, which is a heater holder 207 having a substantially semi-circular cross section in cross section, a fixing heater 204 fixedly disposed on the lower surface of the heater holder 207 along the length of the heater holder (perpendicular to the drawing), An assembly comprising an endless belt-shaped (cylindrical) thin-layer fixing belt 203 loosely fitted to a heater holder 207 provided therewith.
[0007]
Reference numeral 205 denotes an elastic pressure roller, and both ends of the metal core are rotatably supported between side plates of the fixing device.
[0008]
The fixing belt unit 202 is arranged on the upper side of the elastic pressure roller 205 in parallel with the pressure roller 205 with the fixing heater 204 facing downward, and a predetermined pressing force is applied to both ends of the heater holder 207 by urging means (not shown). Is pressed down. As a result, the lower surface of the fixing heater 204 is pressed against the upper surface of the elastic pressure roller 205 with the fixing belt 203 interposed therebetween against the elasticity of the pressure roller, thereby forming a fixing nip portion 206 having a predetermined width.
[0009]
The elastic pressure roller 205 is driven to rotate at a predetermined peripheral speed in the direction of the arrow by a drive mechanism (not shown). Due to the rotational drive of the elastic pressure roller 205, a rotational force acts on the fixing belt 203 in the fixing nip portion 206 by the frictional force between the elastic pressure roller 205 and the outer surface of the fixing belt 203, and the fixing belt 203 has an inner peripheral surface. Is in a driven rotation state around the outer periphery of the heater holder 207 at a peripheral speed substantially corresponding to the peripheral speed of the elastic pressure roller 205 in the direction of the arrow while sliding in close contact with the lower surface of the fixing heater 204 in the fixing nip portion 206.
[0010]
The fixing belt 203 is an endless belt made of a heat-resistant resin having a thickness of about 50 μm, and a release layer (a coating layer of a fluororesin or the like) having a thickness of 10 μm is formed on the surface thereof. Further, in order to reduce the heat capacity of the fixing belt 203, no elastic layer is used for the fixing belt 203.
[0011]
The fixing heater 204 has a resistance heating element formed on a ceramic substrate. A temperature detection unit 209 is in contact with the back surface of the fixing heater 204 to detect the temperature of the fixing heater 204, and the power supplied to the fixing heater 204 is controlled by a control unit (not shown) so that the temperature of the fixing heater 204 becomes a desired temperature. It is controlled to control the temperature.
[0012]
When the elastic pressure roller 205 is driven to rotate, the fixing belt 203 is driven to rotate, and the fixing heater 204 rises to a predetermined temperature and the temperature is controlled, the recording material P carrying the unfixed toner image t is transferred to the fixing nip. It is introduced between a fixing belt 203 and an elastic pressure roller 205. The unfixed toner image carrying surface of the recording material P comes into close contact with the outer surface of the fixing belt 203 and is conveyed by nipping the fixing nip 206 together with the fixing belt 203. In the nipping and conveying process, the heat of the fixing heater 204 is applied to the recording material P via the fixing belt 203, and the pressing force of the fixing nip portion 206 causes the unfixed toner image t to remain on the recording material P permanently. The image is fixed by heat and pressure as a fixed image. The recording material P passes through the fixing nip 206 and is discharged with a curvature separated from the surface of the fixing belt 203.
[0013]
In the fixing device 201 having such a configuration, the heat capacity of the fixing belt 203 is very small, and after the power is supplied to the fixing heater 204, the temperature of the fixing nip portion 206 can be raised to a temperature at which the toner image can be fixed in a short time. It is possible.
[0014]
However, when such a belt fixing device 201 using the fixing belt 203 having no elastic layer is used as a fixing device of a color image forming apparatus, the fixing belt 203 serving as a fixing member has no elastic layer. The surface of the fixing belt 203 cannot follow the unevenness of the surface of the recording material P, the unevenness due to the presence or absence of the toner layer, and the unevenness of the toner layer itself. Would. In the convex portion that is in good contact with the fixing belt 203, heat is transmitted well from the fixing belt 203, so a large amount of heat is given. In the concave portion that does not contact the fixing belt 203 very well, the heat from the fixing belt 203 is applied to the convex portion. Because it is harder to transmit than in the case, the amount of heat given is small. As described above, since the amount of heat applied to the toner layer changes due to the unevenness of the toner layer, the melted state of the toner becomes uneven, resulting in uneven gloss and affecting the image after fixing.
[0015]
In particular, in the case of a color image, since toner images of a plurality of colors are superimposed and mixed and used, the unevenness of the toner layer is larger than that of a black and white image, and when the fixing belt 203 has no elastic layer, the gloss of the image after fixing is high. The unevenness increases and the image quality deteriorates. Further, when the recording material P is an OHP sheet, when the image after fixing is projected, light scattering occurs due to the non-uniform appearance of the image after fixing microscopically. It causes a decline.
[0016]
A method of applying silicone oil or the like to the fixing belt 203 without the elastic layer and applying silicone oil or the like to the recording material P or the uneven portion of the unfixed toner image t so that heat is uniformly transmitted to the fixing belt 203 can be considered, but the cost increases. That is, there is a problem that the image and the recording material P after fixing are sticky with oil.
[0017]
Therefore, a fixing device that constitutes a low-cost color-on-demand fixing device by using a fixing belt having an elastic layer in the belt fixing device has been proposed (for example, see Patent Document 1).
[0018]
FIG. 25 is a schematic configuration diagram of a belt fixing device using a fixing belt 203 having an elastic layer as a fixing member. The same reference numerals are given to the same components and parts as those in the apparatus of FIG. 24, and the description will not be repeated.
[0019]
When this fixing device is used, since the thermal conductivity of the silicone rubber used for the elastic layer of the fixing belt 203 is small, the temperature responsiveness of the fixing belt 203 is poor, and the fixing speed is increased with respect to the temperature rising speed of the fixing heater 204. The temperature of the sleeve rises very slowly. Furthermore, the difference between the temperature of the fixing heater 204 and the temperature of the fixing belt 203 reaches a maximum of several tens of degrees Celsius. For this reason, in a system in which the temperature detecting element 209 is installed on the back surface of the fixing heater 204 as in the related art, it is very difficult to control the temperature of the fixing belt 203.
[0020]
Therefore, in the apparatus shown in FIG. 25, the temperature detecting unit 209 is disposed on the inner surface or the surface of the fixing belt 203 instead of the fixing heater 204, and the temperature of the fixing belt 203 itself is detected, and feedback control such as PID control is performed. The temperature of the fixing belt 203 is controlled by controlling the temperature of the fixing heater 204.
[0021]
By using such a configuration, the temperature of the fixing belt 203 can be controlled with higher accuracy.
[0022]
[Patent Document 1]
JP-A-11-15303
[0023]
[Problems to be solved by the invention]
However, when the fixing operation was performed using this fixing device, the following two problems occurred.
[0024]
(1) Problem 1
When the recording material P is fed from a state where the temperature is regulated and the temperature is stable, the temperature of the fixing belt 203 rapidly decreases immediately after the recording material P enters the fixing nip portion 206, and then the temperature rises. However, overshoot occurs, resulting in a large temperature fluctuation.
[0025]
This phenomenon will be described.
[0026]
In the conventional fixing device, the recording material P is passed after the PID control is continuously performed in the idling state. At this time, as shown in FIG. 5, immediately after the recording material P enters the fixing nip portion 206, the temperature of the inner surface of the fixing belt 203 rapidly decreases, and then the temperature rises, but overshoot occurs. More specifically, as shown in FIG. 5, at the time of idle rotation before the sheet is passed, the temperature of the inner surface of the fixing sleeve 203 is stable, but immediately after the recording material P enters the fixing nip 206, the fixing belt 203 The temperature of the inner surface dropped to a temperature about 10 ° C. lower than the target temperature, then rose to a value about 7 ° C. higher than the target temperature, and then took about 10 seconds to stabilize. Immediately after the recording material P enters the fixing nip portion 206 and until the temperature of the inner surface of the fixing sleeve 203 is stabilized, the temperature ripple (difference between the maximum value and the minimum value of the temperature within a certain time) is about 17 ° C. Was. In the subsequent continuous paper passing, stable temperature control (temperature ripple of about 6 ° C.) was exhibited.
[0027]
In a state where the temperature of the inner surface of the fixing sleeve 203 is stable at the time of idling, the electric power supplied to the fixing heater 204 is constant at about 80 W, and thereafter, during continuous paper passing, the temperature of the inner surface of the fixing sleeve 203 becomes stable. In this state, the electric power supplied to the fixing heater 204 is substantially constant at about 300 W.
[0028]
On the other hand, immediately after the recording material P entered the fixing nip portion 206, the recording material P showed a behavior of rising to about 500 W with a decrease in temperature, settling to about 300 W after vibrating for about 20 seconds. This phenomenon was not solved even by adjusting the gains of the PID control, and it was difficult to further suppress the temperature fluctuation.
[0029]
When a temperature fluctuation of about 17 ° C. occurs in this way, in the electrophotographic color image forming apparatus used in the test, the fixability of the output printed matter greatly varies, and the glossiness (gloss) greatly fluctuates. Image quality was reduced. Further, there is a problem that a fixing failure occurs due to a large temperature change depending on a recording material or a print pattern.
[0030]
This phenomenon is more remarkable when the process speed is higher. At the time of the measurement in FIG. 6, the process speed was 87 mm / sec. However, when the process speed was 190 mm / sec, the temperature of the inner surface of the fixing belt 203 was increased. Immediately after the recording material P enters the fixing nip portion 206, the recording material P drops to a value lower by about 20 ° C. than the target temperature, then rises to a temperature higher by about 8 ° C. than the target temperature, and reaches a temperature of about 28 ° C. It became a ripple. In this case, the fluctuation range of the glossiness is further increased, and the partial fixing failure also worsens.
[0031]
(2) Problem 2
Large overshoot at startup. Further, the temperature ripple at the time of startup is large, and the temperature variation at the time of entry of the recording material after startup is large.
[0032]
This phenomenon will be described.
[0033]
In this fixing device, the startup temperature control sequence includes the following two steps a and b.
[0034]
a. "Start-up (fixed) power control"
b. "PID control"
The “start-up power control” a is a control in which a fixed power is supplied to quickly start the fixing device temperature and secure the on-demand property. In this example, 1000 W is supplied to the fixing heater 204. It is thrown. At this time, the fixing belt 203 is heated by the fixing heater 204 while being driven to rotate with the rotation of the pressure roller 205. When the temperature detected by the temperature detecting means 209 reaches a predetermined temperature (target temperature −20 ° C .: for example, if the target temperature is 190 ° C., 190 ° C.−20 ° C. = 170 ° C.), the “PID control” of b is performed. After that, the power supplied to the fixing heater 204 is controlled by the PID control so that the temperature on the back surface of the fixing belt 203 approaches the target temperature.
[0035]
When the above control is used, as shown in FIG. 21, overshoot occurs and the temperature ripple accompanying the overshoot increases.
[0036]
When the overshoot and the temperature ripple at the time of startup increase, the following two problems occur.
[0037]
▲ 1 ▼. When the operation at a high temperature due to the overshoot at the time of startup is repeated, damage to each component of the fixing device is increased, and the life of the fixing device is shortened.
[0038]
▲ 2 ▼. Since the temperature ripple at the start-up is large, the temperature at the moment when the recording material P enters is not stabilized, and the temperature fluctuation while the recording material P passes through the fixing nip portion 206 becomes large. The fluctuation of gloss in the image becomes large, which is not preferable in image quality. Further, depending on the type of the recording material P and the printing pattern, a fixing failure occurs at a point where the temperature is lowered.
[0039]
On the other hand, it is possible to suppress the overshoot to some extent by gently starting with a small amount of power, but in this case, it takes a long time until the fixing device rises to a predetermined temperature, and the on-demand property is impaired. Would.
[0040]
As described above, when the conventional fixing device control method is used, there is a trade-off between the on-demand property and the stability of the temperature control.
[0041]
The present inventors have conducted intensive studies on this phenomenon, and found that these problems occur for the following two reasons.
[0042]
1) Since silicone rubber used for the elastic layer of the fixing belt 203 has a low thermal conductivity and a large heat capacity, the responsiveness between the time when the fixing heater 204 is energized and the temperature of the fixing belt 203 rises is poor.
[0043]
2) There is a delay in the detection timing due to the position of the temperature detecting means 209 for detecting the temperature of the back surface of the fixing belt 203 being away from the fixing heater 204 which is a heating element.
[0044]
That is, since feedback control represented by PID control is realized by detecting a change in the control amount and adding an operation amount corresponding to the change, when the temperature control based on the PID control is performed, the above-described control is performed. If the dead time (time lag) due to the two reasons 1) and 2) becomes large and the temperature change is large, such as at startup or when the recording material P enters, power detected by the temperature detection unit 209 is subjected to power control. However, since the actual temperatures of the fixing heater 204 and the fixing nip 206 already have different values, accurate temperature control cannot be performed, and overshoot and hunting (temperature ripple) are likely to occur.
[0045]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a long service life of a fixing device even when a fixing belt having an elastic layer is used as a fixing member in a fixing device. Performing a control, as a result, a good fixing property, there is no image defect that occurs when the fixing temperature control temperature is inappropriate, it is possible to obtain a high quality image without print quality unevenness such as gloss, And an image forming apparatus equipped with the fixing device.
[0046]
[Means for Solving the Problems]
The present invention is a fixing device and an image forming apparatus having the following configurations.
[0047]
At least a heating element, a power supply unit for supplying electric power to the heating element, at least one or more temperature detecting means, a first rotating element that moves together with the recording material, and a pressure contact part with the recording material are formed. Temperature control of the first rotating body by feedback-controlling the power supplied from the power supply unit to the heating body based on the temperature detected by the temperature detecting means. In a fixing device that heats the recording material holding the image in the press-contact portion by nipping and conveying,
Before the temperature detecting means detects a temperature change due to the entry of the recording material into the pressure contact portion, power required for heating supplied to the heating element is corrected by a predetermined power. .
[0048]
As a result, the overshoot and temperature ripple are kept small to prolong the life of the fixing device, and perform accurate temperature control of the fixing member. As a result, good fixing performance is exhibited, and the fixing temperature is inappropriate. In this case, it is possible to obtain a high-quality image free from image defects that occur in any case and without print quality unevenness such as gloss.
[0049]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described.
[0050]
Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.
[0051]
<Embodiment 1>
(1) Example of image forming apparatus
FIG. 1 is a schematic configuration diagram illustrating a color image forming apparatus according to Embodiment 1 of the present invention. The image forming apparatus of the present embodiment is a tandem type full color printer of an electrophotographic system.
[0052]
The image forming apparatus includes an image forming unit 1Y for forming a yellow image, an image forming unit 1M for forming a magenta image, an image forming unit 1C for forming a cyan image, and a black image. It has four image forming units (image forming units) of the image forming unit 1Bk to be formed, and these four image forming units are arranged in a line at a fixed interval.
[0053]
Photosensitive drums 2a, 2b, 2c, and 2d are installed in the image forming units 1Y, 1M, 1C, and 1Bk, respectively. Around the photosensitive drums 2a, 2b, 2c, 2d, charging rollers 3a, 3b, 3c, 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d, a drum cleaning device 6a, Exposure devices 7a, 7b, 7c, and 7d are respectively installed above the charging rollers 3a, 3b, 3c, and 3d and the developing devices 4a, 4b, 4c, and 4d. I have. The developing devices 4a, 4b, 4c, and 4d store yellow toner, magenta toner, cyan toner, and black toner, respectively.
[0054]
An endless belt-shaped intermediate transfer member 40 as a transfer medium is in contact with each primary transfer portion N of each of the photosensitive drums 2a, 2b, 2c, and 2d of the image forming portions 1Y, 1M, 1C, and 1Bk. The intermediate transfer belt 40 is stretched between a drive roller 41, a support roller 42, and a secondary transfer opposing roller 43, and is rotated (moved) in the direction of the arrow (clockwise) by the drive of the drive roller 41.
[0055]
The transfer rollers 5a, 5b, 5c, 5d for primary transfer are in contact with the photosensitive drums 2a, 2b, 2c, 2d via the intermediate transfer belt 40 at the respective primary transfer nips N.
[0056]
The secondary transfer opposing roller 43 contacts the secondary transfer roller 44 via the intermediate transfer belt 40 to form a secondary transfer portion M. The secondary transfer roller 44 is provided so as to be able to freely contact and separate from the intermediate transfer belt 40.
[0057]
A belt cleaning device 45 that removes and collects untransferred toner remaining on the surface of the intermediate transfer belt 40 is provided near the drive roller 41 outside the intermediate transfer belt 40.
[0058]
Further, a fixing device 12 is provided downstream of the secondary transfer unit M in the transport direction of the recording material P.
[0059]
Further, an environment sensor 50 and a media sensor 51 are installed in the image forming apparatus.
[0060]
When an image forming operation start signal (print start signal) is issued, each of the photosensitive drums 2a, 2b, 2c, and 2d of the image forming units 1Y, 1M, 1C, and 1Bk, which are driven to rotate at a predetermined process speed, is charged with a charging roller. In the present embodiment, the electrodes 3a, 3b, 3c, and 3d are uniformly charged to a negative polarity.
[0061]
The exposure devices 7a, 7b, 7c and 7d convert the input color-separated image signals into optical signals at a laser output unit (not shown), and convert the converted optical signals into laser beams. Scanning exposure is performed on each of the charged photosensitive drums 2a, 2b, 2c, and 2d to form an electrostatic latent image.
[0062]
First, the yellow toner is charged on the surface of the photosensitive member by the developing device 4a to which a developing bias having the same polarity as the charging polarity (negative polarity) of the photosensitive drum 2a is applied onto the photosensitive drum 2a on which the electrostatic latent image is formed. The electrostatic latent image is visualized by electrostatic attraction according to the electric potential, and is used as a developed image. This yellow toner image is primarily transferred onto the rotating intermediate transfer belt 40 by the transfer roller 5a to which a primary transfer bias (a polarity opposite to that of the toner (positive polarity)) is applied at the primary transfer portion N. Is done. The intermediate transfer belt 40 to which the yellow toner image has been transferred is rotated toward the image forming unit 1M.
[0063]
In the image forming section 1M, the magenta toner image formed on the photosensitive drum 2b in the same manner as described above is superimposed on the yellow toner image on the intermediate transfer belt 40, and is transferred by the primary transfer section N. Is done.
[0064]
Thereafter, the cyan and black toner images formed by the photosensitive drums 2c and 2d of the image forming units 1C and 1Bk are respectively primary-colored on the yellow and magenta toner images superimposedly transferred on the intermediate transfer belt 40. A full-color toner image is formed on the intermediate transfer belt 40 by superimposing sequentially at the transfer portion N.
[0065]
Then, the recording material (transfer material) P is conveyed to the secondary transfer unit M by the registration roller 46 at the timing when the leading end of the full-color toner image on the intermediate transfer belt 40 is moved to the secondary transfer unit M. A full-color toner image is secondarily transferred to the recording material P by the secondary transfer roller 44 to which a secondary transfer bias (a polarity opposite to that of the toner (positive polarity)) is applied. The recording material P on which the full-color toner image has been formed is conveyed to the fixing device 12, where the full-color toner image is heated and pressed at the fixing nip between the fixing belt 20 and the pressure roller 22 to melt on the surface of the recording material P. After fixing, the sheet is discharged to the outside, and becomes an output image of the image forming apparatus. Then, a series of image forming operations ends.
[0066]
Note that the image forming apparatus has an environment sensor 50, and biases and fixing conditions of charging, development, primary transfer, and secondary transfer are changed according to an atmosphere environment (temperature, humidity) in the image forming apparatus. It has a possible configuration, and is used for adjusting the density of a toner image formed on the recording material P and for achieving optimal transfer and fixing conditions. Further, the image forming apparatus has a media sensor 51, and by determining the recording material P, the transfer bias and the fixing condition can be changed according to the recording material. Is used to achieve optimal transfer and fixing conditions.
[0067]
At the time of the primary transfer, the primary transfer residual toner remaining on the photosensitive drums 2a, 2b, 2c, and 2d is removed and recovered by the drum cleaning devices 6a, 6b, 6c, and 6d. Further, the secondary transfer residual toner remaining on the intermediate transfer belt 40 after the secondary transfer is removed and collected by the belt cleaning device 45.
[0068]
(2) Fixing device 12
FIG. 2 is a schematic model diagram of the fixing device 12 in the present embodiment. The fixing device 12 of the present embodiment is a heating device of a fixing belt heating system and a rotating body driving system for tension (tensionless type).
[0069]
1) Overall configuration of device 12
Reference numeral 20 denotes a fixing belt as a first rotating body (first fixing member), which is a cylindrical (endless belt-shaped, sleeve-shaped) member having an elastic layer provided on a belt-shaped member. The fixing belt 20 will be described in detail in section 6) below.
[0070]
Reference numeral 22 denotes a pressure roller as a second rotating body (second fixing member). Reference numeral 17 denotes a heater holder having a heat resistance and rigidity of a substantially semicircular trough-shaped cross section as a heating element holding member. Reference numeral 16 denotes a fixing heater as a heating element (heat source). It is arranged along. The fixing belt 20 is loosely fitted to the heater holder 17. In the present embodiment, the fixing heater 16 is a ceramic heater as described in detail in the section 2) described later.
[0071]
The heater holder 17 is formed of a liquid crystal polymer resin having high heat resistance, and serves to hold the fixing heater 16 and guide the fixing belt 20. In this example, Zenit 7755 (trade name) manufactured by DuPont was used as the liquid crystal polymer. The maximum usable temperature of Zenite 7755 is about 270 ° C.
[0072]
The pressure roller 22 is formed by forming a silicone rubber layer having a thickness of about 3 mm on a stainless steel core by injection molding, and coating a PFA resin tube having a thickness of about 40 μm thereon. The pressure roller 22 is disposed so that both ends of the cored bar are rotatably held between the inner and outer side plates (not shown) of the apparatus frame 24 by bearings. A fixing belt unit including the fixing heater 16, the heater holder 17, the fixing belt 20, and the like is disposed above the pressure roller 22 in parallel with the pressure roller 22 with the heater 16 facing downward. Is urged in the axial direction of the pressure roller 22 by a pressure mechanism (not shown) with a force of 98 N (10 kgf) on one side and a total pressure of 196 N (20 kgf) so that the downward surface of the fixing heater 16 is interposed via the fixing belt 20. The elastic layer of the pressure roller 22 is pressed against the elastic layer with a predetermined pressing force against the elasticity of the elastic layer to form a fixing nip portion 27 having a predetermined width required for heat fixing. The pressurizing mechanism has a pressure release mechanism, and is configured to release the pressurization at the time of jam clearance or the like and to easily remove the recording material P.
[0073]
Reference numerals 18 and 19 denote main and sub thermistors as first and second temperature detecting means. The main thermistor 18 as the first temperature detecting means is disposed in non-contact with the fixing heater 16 which is a heating element, and in this embodiment, is elastically brought into contact with the inner surface of the fixing belt 20 above the heater holder 17 to fix the image. The temperature of the inner surface of the belt 20 is detected. The sub thermistor 19 as the second temperature detecting means is disposed at a position closer to the fixing heater 16 which is a heat source than the main thermistor 18, and in this embodiment, is in contact with the back surface of the fixing heater 16. Detect temperature.
[0074]
The main thermistor 18 has a thermistor element attached to the tip of a stainless steel arm 25 fixedly supported by the heater holder 17, and the arm 25 elastically swings, so that the inner surface of the fixing belt 20 becomes unstable. In this case, the thermistor element is always kept in contact with the inner surface of the fixing belt 20.
[0075]
FIG. 3 is a perspective model diagram showing a positional relationship between the fixing heater 16, the main thermistor 18, and the sub thermistor 19 in the fixing device of the present embodiment. The main thermistor 18 is arranged near the longitudinal center of the fixing belt 20, and the sub thermistor 19 is arranged near the end of the fixing heater 16. The main thermistor 18 is arranged so as to contact the inner surface of the fixing belt 20 and the back surface of the fixing heater 16, respectively.
[0076]
The outputs of the main thermistor 18 and the sub thermistor 19 are connected to a control circuit unit (CPU) 21 via A / D converters 64 and 65, respectively. The content of the temperature control of the fixing heater 16 is determined based on the above, and the power supply to the fixing heater 16 is controlled by the heater drive circuit unit 28 (FIGS. 2 and 4) as a power supply unit (heating unit).
[0077]
Reference numerals 23 and 26 denote an entrance guide and a fixing / discharge roller mounted on the apparatus frame 24. The entrance guide 23 is provided so that the recording material P, which has passed through the secondary transfer nip, is accurately guided to a fixing nip 27 which is a pressure contact portion between the fixing belt 20 and the pressure roller 22 in the fixing heater 16. Play the role of leading. The entrance guide 23 of the present embodiment is made of polyphenylene sulfide (PPS) resin.
[0078]
The pressure roller 22 is driven to rotate at a predetermined peripheral speed in the direction of the arrow by a driving means (not shown). A rotational force acts on the cylindrical fixing belt 20 by the frictional contact between the outer surface of the pressure roller 22 and the fixing belt 20 at the fixing nip 27 due to the rotation of the pressing roller 22, and the fixing belt 20 is rotated. The inner surface of the heater holder 17 is driven to rotate in the direction shown by the arrow while sliding in close contact with the downward surface of the fixing heater 16. Grease is applied to the inner surface of the fixing belt 20 to ensure slidability between the heater holder 17 and the inner surface of the fixing belt 20.
[0079]
The pressure roller 22 is driven to rotate, whereby the cylindrical fixing belt 20 is driven to rotate, and power is supplied to the fixing heater 16, and the temperature of the fixing heater 16 rises to a predetermined temperature. In the adjusted state, the recording material P carrying the unfixed toner image is guided and introduced along the entrance guide 23 between the fixing belt 20 and the pressure roller 22 of the fixing nip portion 27, and is introduced. At this time, the toner image carrying surface side of the recording material P is in close contact with the outer surface of the fixing belt 20, and the fixing nip portion 27 is nipped and transported together with the fixing belt 20. In the nipping and conveying process, the heat of the fixing heater 16 is applied to the recording material P via the fixing belt 20, and the unfixed toner image t on the recording material P is heated and pressed onto the recording material P to be fused and fixed. You. The recording material P that has passed through the fixing nip 27 is separated from the fixing belt 20 by a curvature, and is discharged by a fixing discharge roller 26.
[0080]
2) Main thermistor 18
As shown in FIGS. 2 and 3, the main thermistor 18 is arranged near the longitudinal center of the fixing belt 20, and is arranged so as to contact the inner surface of the fixing belt 20. The main thermistor 18 is used as means for detecting the temperature of the fixing belt 20 which is closer to the temperature of the fixing nip. Therefore, in normal operation, the temperature is controlled so that the detected temperature of the main thermistor 18 becomes the target temperature.
[0081]
3) Sub thermistor 19
As shown in FIG. 3, the sub thermistor 19 is disposed near an end of the fixing heater 16 and is arranged so as to contact the back surface of the fixing heater 16. The sub thermistor 19 serves as a safety device that detects the temperature of the fixing heater 16 as a heating element and monitors the temperature of the fixing heater so as not to exceed a predetermined temperature.
[0082]
Further, the sub-thermistor 19 monitors the overshoot of the temperature of the fixing heater 16 at the time of startup and the temperature rise of the end portion. If it exceeds, it is used for determining to perform control such as lowering the throughput so that the end portion temperature rise does not deteriorate further.
[0083]
4) Fixing heater 16
In the present embodiment, the fixing heater 16 as a heat source is configured to apply a conductive paste containing a silver-palladium alloy on a substrate of aluminum nitride in a film having a uniform thickness by a screen printing method, thereby forming a resistance heating element. A ceramic heater, which is formed and coated with a pressure-resistant glass, is used.
[0084]
FIGS. 4A and 4B are structural model diagrams of an example of such a ceramic heater. FIG. 4A is a partially cutaway surface model diagram, FIG. 4B is a rear model diagram, and FIG. 4C is an enlarged cross-sectional model diagram.
[0085]
The fixing heater 16
▲ 1 ▼. A horizontally long aluminum nitride substrate a whose longitudinal direction is the direction perpendicular to the paper passing direction,
▲ 2 ▼. A 10 μm thick conductive paste containing a silver-palladium (Ag / Pd) alloy, which is applied in a linear or band shape by screen printing on the surface side of the aluminum nitride substrate a along its length and generates heat when a current flows. Resistance heating element layer b having a width of about 1 to 5 mm,
(3). As a power supply pattern for the resistance heating element layer b, first and second electrode portions c and d and extended electric circuit portions e and f are also formed on the surface side of the aluminum nitride substrate a by screen printing of silver paste or the like. ,
▲ 4 ▼. In order to protect the resistance heating element layer b and the extended electric circuit portions e and f and to secure insulation, the thin film having a thickness of about 10 μm, which can withstand rubbing with the fixing belt 20, is formed thereon. Glass coat g,
▲ 5 ▼. Sub thermistor 19 provided on the back side of aluminum nitride substrate a
Etc.
[0086]
The fixing heater 16 is fixedly supported by a heater holder 17 with its front side exposed downward.
[0087]
A power supply connector 30 is mounted on the first and second electrode portions c and d of the fixing heater 16. When power is supplied from the heater drive circuit section 28 to the first and second electrode sections c and d via the power supply connector 30 described above, the resistance heating element layer b generates heat, and the fixing heater 16 quickly rises in temperature. . The heater drive circuit 28 is controlled by the control circuit (CPU) 21.
[0088]
In normal use, the driven rotation of the fixing belt 20 starts with the rotation of the pressure roller 22, and the temperature of the inner surface of the fixing belt 20 increases with the temperature of the fixing heater 16. The power supply to the fixing heater 16 is controlled by PID control, and the input power is controlled so that the inner surface temperature of the fixing belt 20, that is, the detected temperature of the main thermistor 18 becomes 190 ° C.
[0089]
5) Fixing heater drive circuit section 28
FIG. 5 is a block diagram of a control circuit unit (CPU) 21 as a temperature control unit of the fixing unit and a fixing heater driving circuit unit 28. The power supply electrode sections cd of the fixing heater 16 are connected to the fixing heater drive circuit section 28 via a power supply connector (not shown).
[0090]
In the fixing heater drive circuit unit 28, reference numeral 60 denotes an AC power supply, 61 denotes a triac, 62 denotes a zero-cross generation circuit, and 21 denotes a control circuit unit (CPU). The triac 61 is controlled by the control circuit unit 21. The triac 61 turns on and off the heating resistor layer b of the fixing heater 16.
[0091]
The AC power supply 60 sends a zero cross signal to the control circuit section 21 via the zero cross detection circuit 62. The control circuit 21 controls the triac 61 based on the zero cross signal. In this way, when the heating resistor layer b of the fixing heater 16 is energized from the fixing heater driving circuit section 28, the entire temperature of the fixing heater 16 rapidly rises.
[0092]
The outputs of the main thermistor 18 for detecting the temperature of the fixing belt 20 and the sub thermistor 19 for detecting the temperature of the fixing heater 16 are taken into the control circuit (CPU) 21 via A / D converters 64 and 65, respectively.
[0093]
The control circuit unit 21 controls the heater power by controlling the power supplied to the fixing heater 16 by controlling the AC voltage applied to the fixing heater 16 by the triac 61 based on the temperature information of the fixing heater 16 from the main thermistor 18 by controlling the phase and wave number. Control is performed so that the temperature is maintained at a predetermined control target temperature (set temperature).
[0094]
That is, the temperatures of the main thermistor 18 and the sub thermistor 19 are monitored as voltage values by the control circuit section 21 so that the temperature of the fixing belt 20 is maintained at a predetermined set temperature and the fixing heater 16 is controlled. The power supply to the fixing heater 16 is controlled so as to be driven within a predetermined temperature.
[0095]
PID control is used as a typical temperature control method. As a power control method, there are a wave number control, a phase control, and the like. Here, the phase control will be described.
[0096]
That is, the control circuit 21 detects the temperature of the main thermistor 18 every 2 μsec, and determines the amount of power supply to the fixing heater 16 by PID control so as to control the temperature to a desired temperature within the control circuit 21. For example, in order to specify the power in 5% steps, generally, an energization angle of 5% is used for one half-wave of an AC waveform supplied from a power supply. The energization angle is obtained as a timing at which the triac 61 is turned on when the zero-cross signal is detected by the zero-cross generation circuit 62.
[0097]
6) Fixing belt 20
In the present embodiment, the fixing belt 20 is a cylindrical (endless belt-shaped) member in which an elastic layer is provided on a belt-shaped member.
[0098]
Specifically, a silicone rubber layer (elastic layer) having a thickness of about 300 μm is formed on a cylindrical endless belt (belt base material) having a thickness of 30 μm by SUS by a ring coating method. Of the PFA resin tube (outermost surface layer). When the heat capacity of the fixing belt 20 formed in such a configuration was measured, it was 12.2 × 10 ^-2 J / cm ² ・ ℃ (fixing belt 1cm ² Heat capacity per unit).
[0099]
▲ 1 ▼. Base layer of fixing belt
Although a resin such as polyimide can be used for the base layer of the fixing belt 20, a metal such as SUS or nickel has a thermal conductivity about 10 times as large as that of polyimide and can obtain higher on-demand property. Therefore, in the present embodiment, SUS which is metal is used for the base layer of the fixing belt 20.
[0100]
▲ 2 ▼. Elastic layer of fixing belt
As the elastic layer of the fixing belt 20, a rubber layer having a relatively high thermal conductivity is used. This is to obtain a higher on-demand property. The material used in the present embodiment has a specific heat of about 12.2 × 10 ^-1 J / g · ° C.
[0101]
(3). Release layer of fixing belt
By providing a fluororesin layer on the surface of the fixing belt 20, the releasability of the surface is improved, and the offset phenomenon that occurs when the toner once adheres to the surface of the fixing belt 20 and moves to the recording material P again is reduced. Can be prevented. Further, by forming the fluororesin layer on the surface of the fixing belt 20 as a PFA tube, it is possible to more easily form a uniform fluororesin layer.
[0102]
▲ 4 ▼. Heat capacity of fixing belt
In general, when the heat capacity of the fixing belt 20 increases, the temperature rise becomes slow, and the on-demand property is impaired. For example, depending on the configuration of the fixing device, assuming that the temperature rises within one minute without standby temperature control, the heat capacity of the fixing belt 20 is about 4.2 J / cm. ² -It is known that it is necessary to be below ℃.
[0103]
In the present embodiment, at the time of startup from a room temperature state, an electric power of about 1000 W is applied to the fixing heater 16, and the fixing belt 20 is designed to start up at 190 ° C. within 20 seconds. The silicone rubber layer has a specific heat of about 12.2 × 10 ^-1 In this case, the thickness of the silicone rubber must be 500 μm or less, and the heat capacity of the fixing belt 20 is about 18.9 × 10 ^-2 J / cm ² ・ It must be below ℃. Conversely, 4.2 × 10 ^-2 J / cm ² If the temperature is set to be lower than or equal to ° C., the rubber layer of the fixing belt 20 becomes extremely thin, and the image quality such as OHT permeability and gloss unevenness is equivalent to an on-demand fixing device having no elastic layer.
[0104]
In the present embodiment, the thickness of the silicone rubber necessary for obtaining a high-quality image such as OHT transparency and gloss setting is 200 μm or more. The heat capacity at this time is 8.8 × 10 ^-2 J / cm ² -It was ° C.
[0105]
That is, the heat capacity of the fixing belt 20 in the same fixing device configuration as that of the present embodiment is 4.2 × 10 ^-2 J / cm ² ・ ℃ or more 4.2J / cm ² -Generally below ℃. Among them, a heat capacity of 8.8 × 10 can achieve both on-demand performance and high image quality. ^-2 J / cm ² ・ ℃ or more 18.9 × 10 ^-2 J / cm ² -A fixing belt having a temperature of not more than ° C was used.
[0106]
(3) Temperature control of the fixing device at the start of paper passing
In the present embodiment, when correcting the power supplied to the fixing heater 16, the power that is substantially the same as the required power value required for the fixing heater, taking into account the difference in heat capacity due to the basis weight of the recording material P, is taken into account. It is determined that P is supplied at the same time as P enters the fixing nip. This is because it is experimentally known that the required power value varies depending on the basis weight of the recording material P when continuous paper feeding is performed under the same conditions.
[0107]
In the present embodiment, the electric power supplied to the fixing heater 16 is corrected from the required electric power value obtained by the experiment according to the table classified according to the paper mode. Actually, when the user designates the print mode, the print mode information is received together with the print signal from the host computer 70, and the control circuit 21 determines the input power at the time of paper passing.
[0108]
Table 1 shows the relationship between each paper mode and the power input during paper passing in this embodiment.
[0109]
[Table 1]

[0110]
The time during which predetermined power is applied without performing PID control is selected so as to minimize the temperature ripple of the fixing belt 20. The corrected electric power is supplied before the recording material P enters at the time of the start of sheet feeding. This is because if the correction power is supplied at the same time when the recording material P enters the fixing nip, the temperature of the fixing belt 20 may be greatly reduced. If the timing of inputting the correction power is too early, the temperature of the fixing belt 20 rises greatly, and if it is too late, the temperature of the fixing belt 20 decreases after the recording material P enters the fixing nip as described above. Would. In this embodiment, an appropriate timing of about 0.5 seconds is used. Also, if the time during which the predetermined power is applied without performing the PID control is too short, the PID control approaches the normal PID control, and the effect of the predetermined power input is reduced. If the length is too long, the temperature fluctuation of the fixing belt 20 at the time of paper passing becomes large, and when returning to the PID control, the temperature ripple becomes large. For this reason, in the present embodiment, the predetermined power supply control is performed from about 0.5 seconds to about 1 second before the start of sheet feeding.
[0111]
FIG. 10 shows a flowchart of the power control method in the present embodiment.
[0112]
The actual correction operation will be described below according to the flow.
[0113]
In FIG. 10, after the power is turned on, the image forming apparatus rises to a state in which a print signal can be received (a1). When a print command is received from a host computer (not shown) (a2), the paper mode is read from the print signal (a3). The control circuit unit (CPU) 21 in the printer determines the paper feeding power E2 (W) corresponding to the paper mode as shown in Table 1 (a4). After that, the control circuit section 21 drives the heater drive circuit 28 to start the temperature control of the heater 21 to control the temperature of the fixing belt 20 to a predetermined temperature (a5). When the temperature of the fixing belt 20 becomes close to a predetermined temperature and the startup temperature control is completed (a6), the print temperature control temperature of 190 ° C. is set to the target temperature, and the temperature is controlled to the target temperature by PID control (a7). Thereafter, the apparatus waits at the target temperature while performing PID control until about 0.5 seconds before the recording material enters (a8).
[0114]
About 0.5 seconds before the entry of the recording material, the PID control is stopped, and a predetermined power E2 (W) is output as the input power at the time of paper passage determined at a4 (a9). E2 (W) is continuously supplied until 0.5 seconds later (a10). Thereafter, the print temperature control temperature of 190 ° C. is set to the target temperature, and the PID control is restarted (a11).
[0115]
The above operation is continued until the printing is completed (a12), and when the print job is completed, the temperature control is completed (a13). This correction is performed based on a table (Table 1) of the paper mode and the input power E2 (W) at the time of paper passage provided in the control circuit unit (CPU) 21 in the printer.
[0116]
As described above, the PID control is stopped for a fixed time before and after the timing of the entry of the recording material P, and the electric power supplied to the fixing heater is corrected to a predetermined value and supplied, whereby the temperature detection dead time is reduced. More stable temperature control can be performed without causing temperature fluctuations due to the entry of the recording material P at the start of sheet feeding.
[0117]
Further, by performing correction of the predetermined power in consideration of the difference in heat capacity due to the basis weight of the recording material P, stable temperature control can be performed regardless of the heat capacity of the recording material P.
[0118]
(4) Temperature measurement result and image output experiment result when this embodiment is used
In the present embodiment, the PID control is prohibited and the fixed power based on Table 1 is applied for about 0.5 to about 1 second before entering the recording material at the start of sheet feeding, and then the PID control is restarted. I did it. The power input at this time is determined according to the basis weight of the paper used as described above. The time during which the PID control is prohibited and the predetermined power is applied is set from about 0.5 seconds to about 1 second before the recording material enters, for the reason described above.
[0119]
1) Experimental method
The fixing device is rotated at a process speed of 87 mm / sec, and the temperature of the main thermistor 18 is controlled so as to be 190 ° C., and sufficient time has passed.
In this state, the grammage is 128 g / m ² Was passed continuously (16 sheets / min) using a recording material called New NPI fine paper 128 g (Nippon Paper Industries, trade name).
[0120]
At this time, a measured value of the temperature of the main thermistor 18 was recorded as the inner surface temperature of the fixing sleeve 20. The electric power was measured by converting the output of the electric power value through the WT200 DIGITAL POWER METER manufactured by Yokogawa, similarly to A / D conversion by the KEYENCE PC temperature recorder NR250, and taking in the PC.
[0121]
The glossiness of the image after fixing was measured using a gloss meter PG-3D manufactured by Nippon Denshoku Industries Co., Ltd. according to a 75 ° specular gloss measurement method in JIS Z8741.
[0122]
As the toner amount on the recording material, the toner amount of a solid image portion of a so-called primary color of yellow, magenta, cyan, and black is about 0.5 to 0.6 mg / cm. ² , Red, green, blue, the so-called secondary color (image in which two color toners are superimposed), the toner amount in the solid image portion is about 1.0 to 1.2 mg / cm. ² , And the glossiness of the image after fixing was measured.
[0123]
As a rubbing test for evaluating the fixing property, a black single-color image of 5 mm × 5 mm was formed on the recording material P, and 50 sheets were continuously used at a speed of 16 ppm using the fixing device of the present embodiment. After fixing, a weight of a predetermined weight (200 g) is placed on the image forming surface via Sylbon C (trade name), and the image forming surface is rubbed five times back and forth, and the image before and after the rubbing is rubbed. Of the reflection density (%) was determined. It can be said that the smaller the rate of change of the reflection density (density reduction rate), the better the fixability. Gretag Macbeth RD918 (trade name) was used for the measurement of the reflection density. For the measurement, the density reduction rate of 9 points was measured for each of the recording sheets of the 1, 2, 3, 5, 10, 20, 30, 40, and 50 sheets of the 50 fixed recording materials. , The worst value was used.
[0124]
2) Experimental results
FIG. 7 shows a graph in which the power applied to the fixing heater 16 and the behavior of the inner surface temperature of the fixing belt 20 before and after the paper is passed in the fixing device in the case of using the present embodiment are recorded.
[0125]
As shown in FIG. 7, a stable temperature control (temperature ripple of about 7 ° C.) was observed before and after the recording material P entered the fixing nip.
[0126]
At this time, the electric power supplied to the fixing heater 16 before and after the recording material P enters the fixing nip portion is forced from about 80 W during idle rotation to 0.5 seconds before the recording material P enters the fixing nip portion. Approximately 300 W was supplied, and stable temperature control could be performed without causing large power fluctuations after the recording material P entered the fixing nip.
[0127]
As described above, if the temperature ripple within about 7 ° C. could be maintained, the gloss variation within one sheet of the output printed matter was about 4 for a single color and about 6 for a secondary color. Table 2 shows the average value of the gloss of each color in one recording material and the variation range of the gloss in one recording material in the present embodiment. As described above, by applying the present invention, it was possible to obtain a stable gloss having a relatively high average value and a small fluctuation range within one recording material.
[0128]
[Table 2]

[0129]
Further, the worst value of the density reduction rate in the fixing property test was 15%, and good fixing property was obtained.
[0130]
(5) Comparative example 1
In the conventional fixing device, a predetermined power is not supplied before and after the recording material P enters, and the temperature control is all performed by PID control.
[0131]
1) Experimental method
An experiment was performed using the same fixing device configuration and measurement method as those of the experiment in the first embodiment, and thus the description is omitted here. However, the control in the conventional fixing device is different from the above in that the temperature control is performed by PID control without inputting a predetermined power as described above.
[0132]
2) Experimental results
FIG. 6 shows a graph in which the power supplied to the fixing heater 16 before and after the recording material enters the fixing nip portion and the temperature behavior of the inner surface of the fixing belt 20 in the fixing device of Comparative Example 1 are shown.
[0133]
As shown in FIG. 6, during idling before the recording material P enters the fixing nip portion, the inner surface temperature of the fixing sleeve 20 shows a stable behavior, but immediately after the recording material P enters the fixing nip portion. Then, the inner surface temperature of the fixing sleeve 20 drops to a value about 10 ° C. lower than the target temperature, and then rises to a temperature about 7 ° C. higher than the target temperature. After that, it took about 10 seconds for the inner surface temperature of the fixing sleeve 20 to stabilize, and the temperature ripple became about 17 ° C. In the subsequent continuous feeding of the recording material P, stable temperature control (temperature ripple of about 6 ° C.) was exhibited.
[0134]
As described above, when a temperature ripple of about 17 ° C. occurs, in the in-line type electrophotographic color image forming apparatus used for the test, the gloss of the printed matter output is about one color in one recording material P. In the case of the 9th and secondary colors, the image fluctuated by about 14 and the image quality was lowered (Table 3).
[0135]
[Table 3]

[0136]
Further, the worst value of the density reduction rate in the fixing property test was 28%. When the fixing property exceeds 20%, not only characters are peeled off when the user uses the image, the halftone image is blurred, but also the hands, clothes and other paper are stained. Occurs.
[0137]
The region of the recording material P where the density reduction rate is large coincides with the region where the temperature of the inner surface of the fixing belt 20 has dropped, and the partial temperature decrease due to the occurrence of the temperature ripple affects the fixing property. I knew it was there. As described above, in this comparative example, there is a large variation in the fixing property depending on the measurement points, and sufficient performance as a fixing device cannot be obtained.
[0138]
(6) Consideration
The effect of applying a fixed power to a predetermined value before and after the recording material P enters the fixing nip is considered as follows.
[0139]
In a stable state at the time of idling and at the time of paper passing, the power supplied to the fixing heater 16 is substantially constant. The required power value during the pre-rotation at the regular time is E1 (W), and the required power value at the time of presentation when the recording material is passed is E2 (W).
[0140]
When the recording material P enters the fixing nip portion, the temperature of the fixing belt 20 is sharply affected by the recording material. In the case of normal PID control, power control is performed after the main thermistor 18 detects temperature fluctuation. For this reason, when the main thermistor 18 is installed away from the heat generating portion, when a sudden temperature change occurs, the detected temperature of the main thermistor 18 is different from the actual temperatures of the fixing heater 16 and the fixing nip. Since different values are indicated, power may be supplied excessively, or the supplied power may be insufficient. Therefore, a temperature ripple occurs, and the inner surface temperature of the fixing sleeve 20 is not stabilized.
[0141]
On the other hand, in the present embodiment, the required power E2 (W) is supplied as a fixed value in synchronization with the timing at which the recording material P enters the fixing nip portion. Absent. Therefore, it is possible to reduce the temperature ripple as compared with the normal PID control.
[0142]
It is not necessary to apply the predetermined power for a long time, and if the section is applied for a period until the inner surface temperature of the fixing belt 20 is stabilized to some extent, even after returning to the normal PID control, sufficiently stable temperature control can be performed. .
[0143]
Further, since the amount of heat deprived from the fixing belt 20 due to the paper passing varies depending on the properties of the recording material P, in the present embodiment, attention is paid particularly to the basis weight of the recording material P, and the substantially required power in consideration of the difference in heat capacity is considered. Was corrected.
As a result, stable temperature control (temperature ripple of about 7 ° C.) was achieved.
[0144]
(7) Predetermined power value
Note that the predetermined power value input at the start of paper passing may be substantially the same as E2 (W), and the magnitude of the power difference from E2 (W) may be within a range that provides a desired temperature ripple.
[0145]
That is, in the present embodiment, the predetermined power (offset power at the time of paper passing) to be applied before and after the recording material enters the fixing nip is determined by the paper mode. At this time, even if the required powers of the corresponding media in the paper mode do not exactly match, they need only be approximately the same. This is because the control is returned to the target temperature again by returning to the PID control after the predetermined power supply for a certain time. That is, when the temperature does not exactly match, the temperature goes away from the target temperature, but thereafter, the PID control is again performed so that the temperature approaches the target temperature. It suffices if the temperature fluctuation at that time is within a desired temperature ripple.
[0146]
In general, when the printing speed is high, the difference between the appropriate offset powers at the time of paper passing due to the difference of the basis weights of the recording materials P is further increased. It is necessary to make a division. In such a case, the paper mode is made finer, and the basis weight is made to correspond to the basis weight using a paper thickness sensor or the like, so that the correspondence between the finer basis weight and the offset electric power at the time of paper passing is achieved. Can be controlled within the temperature ripple.
[0147]
(8) Summary
As described above, in the present embodiment, the PID control is prohibited for a certain period of time before and after the timing when the recording material P enters the fixing nip at the start of sheet feeding, and the power supplied to the fixing heater 16 is corrected to a predetermined value. By doing so, more stable temperature control could be performed without causing temperature fluctuations due to the intrusion of the recording material P at the start of sheet feeding due to the dead time of temperature detection.
[0148]
Further, when determining the power value to be supplied, by taking into account the difference in heat capacity due to the basis weight of the recording material P and performing correction, more accurate and stable temperature control could be performed.
[0149]
By controlling the temperature ripple to a small value, accurate temperature control of the fixing member is performed, and as a result, good fixing performance is exhibited. There is no image defect that occurs when the fixing temperature is inappropriate, and printing quality such as gloss is improved. High quality images without unevenness could be obtained.
[0150]
<Embodiment 2>
In the present embodiment, the PID control is prohibited for a certain time before and after the timing when the recording material P enters the fixing nip at the time of the start of sheet feeding, and the power supplied to the fixing heater 16 is corrected to a predetermined power and supplied. At this time, the heat transfer and heat capacity from the fixing device are detected by using a media sensor to detect a special recording material P, and the heat transfer and heat capacity are corrected to a substantially required power value, thereby reducing the temperature detection dead time. A method of performing more stable temperature control without causing temperature fluctuation when the recording material P enters the fixing nip will be described.
[0151]
In this embodiment, the general configuration and control of the fixing device are the same as in the first embodiment. However, when correcting the electric power supplied to the fixing heater 16 to a predetermined electric power, the electric conductivity and the heat capacity from the fixing device are corrected to a substantially necessary electric power value of the special recording material P in consideration of the heat transfer and the heat capacity. That is different.
[0152]
The configuration of the image forming apparatus is the same as that of the first embodiment, and is as shown in FIG. Further, the configuration of the fixing device is the same as that of the first embodiment, and is as shown in FIGS.
[0153]
In the case of a recording material called rough paper or a recording material of a film type such as OHT having poor smoothness of the surface of the recording material P, heat transfer from the fixing device to the recording material P and heat capacity are different. Are the same, the power required for correcting to a predetermined power is different.
[0154]
This is because, in a recording material having approximately the same basis weight, heat transmission is poor due to poor surface smoothness of rough paper, and heat transmission is poor in rough paper as compared with general smooth paper. This is because a system-based recording material has a good surface property and has a large heat capacity due to a different material, so that a larger amount of heat is required for fixing.
[0155]
In order to perform more accurate temperature control, when the electric power supplied to the fixing heater 16 is corrected to a predetermined electric power, the heat conductivity and heat capacity from the fixing device take into account the heat conductivity and heat capacity of the special recording material P. It is effective to correct the value to the required power value. Therefore, the difference between these media is determined by the media sensor 51 to correct the approximate required power value in consideration of the heat conductivity and the heat capacity.
[0156]
FIG. 8 shows a schematic diagram of the configuration of the media sensor 51. The media sensor 51 has an LED 33 as a light source, a CMOS sensor 34 as reading means, and lenses 35 and 36 as imaging lenses. Light using the LED 33 as a light source is applied to the recording material transport guide 31 or the surface of the recording material P on the recording material transport guide 31 via a lens 35. The reflected light is condensed via the lens 36 and is imaged on the CMOS sensor 34. Thereby, the surface image of the recording paper transport guide 31 or the recording material P is read. Thereby, the surface state of the paper fiber of the recording material P is read, and the analog output is A / D converted to digital data. The gain operation and the filter operation of the digital data are programmably processed by a control processor (not shown). Then, an image comparison operation is performed, and a paper type is determined based on the result of the image comparison operation.
[0157]
In the present embodiment, when correcting the electric power supplied to the fixing heater 16, the media sensor 51 detects that the recording material is rough paper or a film-type recording material such as OHT, thereby transmitting the recording material P. The power was corrected to approximately the required power in consideration of differences in thermal properties and heat capacity. Here, the predetermined power value in the first embodiment uses a different correction value even when the recording material P is rough paper or a film-type recording material such as OHT, even in the same paper mode. .
[0158]
Table 4 shows the relationship between each paper mode and the input power at the time of paper passing in the present embodiment.
[0159]
[Table 4]

[0160]
When the recording material P is a medium having general heat conductivity and heat capacity, the value in the “smooth paper” column in Table 4 of the embodiment is used.
[0161]
As shown in Table 4, when the recording material is rough paper, the correction value is made smaller than that of general smooth paper, and when the recording material is a film-based recording material (film media) such as OHT, the correction value is reduced. Was made larger than that of general smooth paper.
[0162]
Next, an actual correction operation using the present embodiment will be described.
[0163]
FIG. 11 shows that, in the present embodiment, the PID control is prohibited for a certain period of time before and after the recording material P enters the fixing nip portion, and the power supplied to the fixing heater is corrected to a predetermined value when the recording material P is supplied. FIG. 9 is a flowchart showing a method for detecting a recording material P having a special heat transfer property and heat capacity from a fixing device using a sensor, and supplying a necessary power value to the fixing heater 16 in consideration of the heat transfer property and heat capacity. .
[0164]
The actual correction operation will be described below according to the flow.
[0165]
In FIG. 11, after the power is turned on, the image forming apparatus rises to a state in which a print signal can be received (b1). When a print command is received from a host computer (not shown) (b2), the paper mode is read from the print signal (b3). Thereafter, the control circuit unit 21 drives the heater driving circuit 28 to start the temperature control of the heater 21 to control the temperature of the fixing belt 20 to a predetermined temperature (b4). After that, the recording material P is a plain paper, a rough paper (a recording material having a low heat conductivity and a small heat capacity), or a film medium (a recording material having a high heat conductivity and a large heat capacity) by the media sensor 51. Is determined (b5). Thereafter, the control circuit unit (CPU) 21 in the printer responds to the paper mode and the characteristics of the recording material (whether it is plain paper, rough paper, or film media) as shown in Tables 1 and 4. The paper feeding power E2 (W) is determined (b6). When the temperature of the fixing belt 20 reaches a predetermined temperature and the startup temperature control is completed (b7), the print temperature control temperature of 190 ° C. is set to the target temperature, and the temperature is controlled to the target temperature by PID control (b8). After that, the fixing unit is driven and waits for about 0.5 seconds before the recording material enters the fixing nip while controlling the temperature (b9).
[0166]
When detecting about 0.5 seconds before the recording material enters the fixing nip portion (b9), the PID control is prohibited, and the paper-feeding input power E2 (W) determined at b6 is output (b10). Then, E2 is continuously supplied until about 0.5 second elapses after the recording material enters the fixing nip portion (b11). Thereafter, the print temperature control temperature of 190 ° C. is set to the target temperature, and the PID control is restarted (b12).
[0167]
The above operation is continued until the printing is completed (b13), and at the same time when the print job is completed, the temperature control is completed (b14).
[0168]
As described above, the PID control is prohibited for a certain time before and after the timing when the recording material P enters the fixing nip at the start of sheet feeding, and the power supplied to the fixing heater is corrected to a predetermined value and supplied. In this case, the heat transfer and heat capacity from the fixing device are detected using a media sensor to detect a special recording material P, and the power is corrected to a substantially required power value in consideration of the heat transfer and heat capacity, so that the dead time of temperature detection is reduced. When the recording material P enters the fixing nip, the temperature of the fixing belt does not fluctuate, and more stable temperature control can be performed.
[0169]
Next, in order to show the effects of stabilizing the temperature behavior and improving the image quality in the case of using the present embodiment by comparing with the conventional example and the first embodiment, the temperature of the fixing device under the following conditions is shown. The behavior was measured, and the fixed image was confirmed.
[0170]
The fixing device rotates at a process speed of 87 mm / sec, and the temperature is controlled so that the main thermistor detection temperature becomes constant at 190 ° C., and sufficient time has passed. In this state, the basis weight of the rough media is 75 g / m. ² Fox River Bond (Fox River, trade name) and a film medium having a basis weight of 166 g / m2. ² Color Laser Gloss Film GF-2 (available from Canon, trade name) was continuously passed (16 sheets / min).
[0171]
At this time, a measured value of the temperature of the main thermistor 18 was recorded as the inner surface temperature of the fixing sleeve 20.
[0172]
The electric power was measured by converting the output of the electric power value through the WT200 DIGITAL POWER METER manufactured by Yokogawa, similarly to A / D conversion by the KEYENCE PC temperature recorder NR250, and taking in the PC.
[0173]
The electric power supplied to the fixing heater 16 before passing the paper was substantially the same under each condition, and was about 80 W.
[0174]
Table 5 shows the temperature ripple before and after the paper passing in the fixing device of Comparative Example 1 and the first and second embodiments.
[0175]
[Table 5]

[0176]
As can be seen from Table 5, more stable temperature control (temperature ripple of about 7 ° C.) was achieved by performing this embodiment.
[0177]
This is based on the following grounds.
[0178]
In a sufficiently warmed fixing device, Fox River Bond (75 g / m ² The power input to the fixing heater 16 in the paper mode corresponding to the basis weight is 275 W in the first embodiment. However, this recording material has poor heat conductivity, so-called rough paper, and is a recording material having a small heat capacity.Since the amount of heat applied to the recording material is smaller than that of ordinary smooth paper, when a predetermined power is applied, The state is relatively excessive in power. For this reason, when the recording material P enters the fixing nip portion, a temperature rise occurs, and the temperature ripple becomes larger than that of general smooth paper.
[0179]
In the second embodiment, the power supplied before and after the recording material enters the fixing nip portion is set to be small in consideration of the properties of the rough paper such as low heat conductivity and low heat capacity by determining the rough paper. As a result, the temperature rise when the recording material P enters is suppressed, so that the temperature ripple is reduced.
[0180]
For a film-based recording material such as OHT, the same effect can be obtained by correcting in the direction opposite to that of the rough paper.
[0181]
As described above, in the present embodiment, when the recording material P is a film medium such as rough paper or OHT, a predetermined amount of the recording material P to be inserted when the recording material enters the fixing nip portion according to the detection result of the media sensor. By correcting the power value, stable temperature control (temperature ripple of about 7 ° C.) was achieved.
[0182]
In the present embodiment, the description has been given of the change of the input power based on the discrimination between the rough paper and the film-based recording material such as OHT. It is also possible to determine the offset power at the time of sheet passing by the same correction.
[0183]
<Embodiment 3>
In the present embodiment, the PID control is prohibited for a fixed time before and after the timing at which the recording material P enters the fixing nip portion, and when the power supplied to the fixing heater 16 is corrected to a predetermined power and supplied, a fixing device is used. A description will be given of a method of correcting a predetermined power value according to the heat storage condition, thereby suppressing a temperature change when the recording material P enters the fixing nip portion and performing more stable temperature control.
[0184]
In this embodiment, the general configuration and control of the fixing device are the same as in the first and second embodiments. However, before and after the timing at which the recording material P enters the fixing nip portion, when correcting the power supplied to the fixing heater 16 with the predetermined power, the predetermined power value is corrected to a value in consideration of the heat storage condition of the fixing device. To be different.
[0185]
The configuration of the image forming apparatus is the same as that of the first embodiment, and is as shown in FIG. The configuration of the fixing device is the same as in the first and second embodiments, and is as shown in FIGS. Therefore, a duplicate description will be omitted.
[0186]
In this embodiment, before and after the timing at which the recording material P enters the fixing nip portion, when correcting the power supplied to the fixing heater 16 with a predetermined power, the power is corrected to substantially the required power in consideration of the heat storage condition of the fixing device. I decided.
[0187]
In other words, the power required for performing stable temperature control during idle rotation is referred to as “idling rotation offset power”, and the power required for performing stable temperature control when the recording material P passes is referred to as “passage power”. "Predetermined electric power to be supplied at the time of paper".
[0188]
At this time, the “offset power at the time of paper passing” is defined such that “predetermined power input at the time of paper passing = offset power at idle rotation + offset power at the time of paper passing”. Further, in the present embodiment, the idle rotation offset power is varied depending on the heat storage condition of the fixing device.
[0189]
The optimum values of the idle rotation offset power and the sheet-passing offset power vary depending on the heat storage condition of the fixing device. For example, the optimal idle rotation offset power is about 200 W immediately after the fixing device is started up at room temperature, and the optimal idle rotation offset power is about 80 W in a sufficiently warmed fixing device.
[0190]
When the paper mode is the thick paper 1, the optimum offset power during paper passing is 420 W immediately after the fixing device is started from a room temperature state, and 300 W when the fixing device is sufficiently warmed.
[0191]
In the present embodiment, even when the electric power supplied to the fixing heater 16 varies depending on the heat storage condition of the fixing device, the predetermined electric power value is corrected so that more precise temperature control can be performed.
[0192]
Table 6 shows the sheet passing offset power in each paper mode when the fixing device of the present embodiment is sufficiently warmed. In the first embodiment described above, the fixing device is in a sufficiently warmed state, and the idle rotation offset power at this time is equivalent to 80 W. The sum of this power and the sheet passing offset power shown in Table 6 is equal to the sheet passing input power shown in Table 1 of the first embodiment.
[0193]
[Table 6]

[0194]
In addition, since it is known that the heat storage condition of the fixing device depends on the power supply time to the fixing heater 16 after the start-up from the room temperature state, the idle rotation power is changed according to the print count in the present embodiment. I decided. The print count is a count number corresponding to the number of printed sheets of A4 size paper of the fixing device when continuous printing is performed after startup from a room temperature state. It was found that the print count, the heater holder temperature, and the idle rotation offset power showed the relationship shown in Table 7 with good reproducibility.
[0195]
[Table 7]

[0196]
Further, in the present embodiment, when the start-up control is performed again after the end of the print job while the fixing device is storing heat, the start-up control is performed according to the detected temperature of the sub thermistor 19 immediately before the energization of the heater 16 is started. The idle rotation power is determined by estimating the heat storage condition of the fixing device, determining the print count at which the heat storage condition of the fixing device becomes equal. Specifically, when the detected temperature of the sub-thermistor 19 at the start of energization is 40 ° C. or less, the heater holder temperature after startup is expected to be 55 ° C. or less. If this is done, control is used to increase the count to 2, 3, and 4 for each sheet, and accordingly, decrease the idle rotation offset power. Similarly, when the detected temperature before the start of the startup is 41 to 55 ° C., the heater holder temperature is expected to be about 60 ° C., so the print count is assumed to be 2. Similarly, when the detected temperature is 56 to 75 ° C., the print count is 3, when the detected temperature is 76 to 95 ° C., the print count is 4, when the detected temperature is 96 to 125 ° C., the print count is 6, and the detected temperature is 126 ° C. In the above case, the idle rotation power is determined as the print count 10.
[0197]
FIG. 12 shows that, in the present embodiment, when the PID control is prohibited for a certain period of time before and after the timing when the recording material P enters the fixing nip, the power supplied to the fixing heater is corrected to a predetermined value and supplied. 5 is a flowchart illustrating a method of correcting the power value to be substantially the same as the required power value in consideration of the heat storage condition of the fixing device.
[0198]
The actual correction operation will be described below according to the flow.
[0199]
In FIG. 12, after the power is turned on, the image forming apparatus rises to a state in which a print signal can be received (c1). When a print command is received from a host computer (not shown) (c2), the paper mode is read from the print signal (c3). Then, the temperature Ta of the sub thermistor 19 is detected (c4). From the detected temperature Ta, the idle rotation power (W) is determined according to Table 7 (c5). Thereafter, the control circuit unit 21 drives the heater drive circuit 28 to start the temperature control of the heater 21 in order to control the temperature of the fixing belt 20 to a predetermined temperature (c6). Thereafter, the media sensor 51 determines whether the recording material P is plain paper, rough paper (a recording material having low heat conductivity), or a film medium (a recording material having high heat conductivity) (c7). Thereafter, the control circuit unit (CPU) 21 in the printer, as shown in Table 6, communicates with the paper mode and the properties of the recording material (whether it is plain paper, rough paper, or film media). The paper-time offset power (W) is determined (c8). When the temperature of the fixing belt 20 approaches the predetermined temperature and the start-up temperature control ends (c9), the print temperature control temperature of 190 ° C. is set to the target temperature, and the target temperature is controlled by the PID control (c10). . Thereafter, the fixing device is driven and kept in a standby state with the temperature adjusted until about 0.5 seconds before the recording material enters the fixing nip (c11).
[0200]
At the time point when about 0.5 seconds before the recording material enters the fixing nip portion, the PID control is prohibited, and the idle rotation power (W) determined at c5 and the sheet passing offset power determined at c8. The power (W) that is the sum of (W) and (W) is output (c12), and this power is continuously applied until about 0.5 seconds after the recording material enters (c13). Thereafter, the print temperature control temperature of 190 ° C. is set to the target temperature, and the PID control is restarted (c14).
[0201]
The above operation is continued until the printing is completed (c15), and at the same time when the print job is completed, the temperature control is completed (c16).
[0202]
As described above, when the PID control is prohibited for a predetermined time before and after the timing at which the recording material P enters the fixing nip, and the power supplied to the fixing heater is corrected to a predetermined value and supplied, the fixing device Is corrected to the substantially required power value in consideration of the heat storage condition of the recording material P, and due to the dead time of the temperature detection, the temperature of the fixing belt 20 does not fluctuate when the recording material P body fixing nip portion enters, and the temperature is more stable. Temperature control can be performed.
[0203]
In the present embodiment, the power to be supplied at the time of paper passing can be determined with high accuracy under a wide range of conditions from the room temperature state of the fixing device to the high temperature state during durability, so that more stable temperature control can be performed.
[0204]
Thus, stable temperature control (temperature ripple of about 7 ° C.) was achieved regardless of the heat storage condition of the fixing device.
[0205]
As described above, in the present embodiment, the PID control is prohibited for a certain period of time before and after the timing when the recording material P enters the fixing nip portion, and when the power supplied to the fixing heater 16 is corrected to a predetermined power and supplied, the fixing is performed. By performing correction to the substantially required power value in consideration of the heat storage condition of the apparatus, more stable temperature control can be performed without causing temperature fluctuation due to the entry of the recording material P at the start of sheet feeding due to temperature detection dead time. I was able to.
[0206]
As described above, by controlling the temperature ripple to a small value, accurate temperature control of the fixing member is performed. As a result, good fixing performance is exhibited, and there is no image defect that occurs when the fixing temperature control temperature is inappropriate. Thus, a high-quality image without uneven printing quality was obtained.
[0207]
<Embodiment 4>
In this embodiment, before and after the timing when the recording material P enters the fixing nip portion, the PID control is prohibited, and when the power supplied to the fixing heater 16 is corrected to a predetermined power and supplied, the environment sensor is turned on. By correcting the power to approximately the required power in consideration of the difference in the amount of water of the recording material P, when the recording material P enters the fixing nip portion, the temperature of the fixing belt does not fluctuate, and more stable temperature control is performed. Will be described.
[0208]
In the present embodiment, the general configuration and control of the fixing device are the same as in the third embodiment. However, when the power supplied to the fixing heater 16 is corrected, the correction is performed to substantially the required power in consideration of the difference in heat capacity depending on the state of the recording material P being left in the environment.
[0209]
The configuration of the image forming apparatus is the same as that of the first embodiment and is as shown in FIG. The configuration of the fixing device is the same as in the first, second, and third embodiments, and is as shown in FIGS.
[0210]
In the present embodiment, when correcting the power supplied to the fixing heater 16, the environment sensor 50 detects the environment, and the power is corrected to substantially the required power in consideration of the difference in heat capacity due to the environment where the recording material P is left. I made it. When considering the correction power, the sum of the idle rotation offset power correction and the sheet offset power correction is treated as the correction power. Here, it is assumed that the sheet transmission offset power varies depending on the degree of moisture absorption of the recording material P. In a water volume environment (for example, an H / H (30 ° C./80% Rh) environment), more power is supplied.
[0211]
FIG. 9 shows the electric power required when continuously passing the abandoned paper of each basis weight in three types of environments. The conditions are as follows. The process speed was measured at 87 mm / sec at a constant temperature of 190 ° C. after a sufficient time had elapsed. As shown in FIG. 9, in the H / H environment, the power required to maintain the temperature, which is supplied to the fixing heater 16 when the environment-leaved paper of each grammage is continuously passed (16 sheets / min), is L / H. There was a tendency to be about 30 W larger than that of L (15 ° C. 10%) environment-leaved paper or J / J (24.5 ° C. 45%) environment-leaved paper.
[0212]
The reason why the power supplied to the fixing heater 16 during continuous paper feeding (16 sheets / minute) in the H / H environment-leaved paper is increased is that the heat capacity is increased due to moisture absorption of the paper.
[0213]
In the present embodiment, the electric power required to maintain the temperature applied to the fixing heater 16 during continuous paper feeding when using paper left in a high-humidity environment is lower than that in the case where the paper is left in a normal environment or in a low-humidity environment. It is done to correspond to high.
[0214]
Table 8 shows a relationship between the paper mode and the offset power at the time of paper passing in the present embodiment.
[0215]
[Table 8]

[0216]
FIG. 13 illustrates a case where the PID control is prohibited for a predetermined time before and after the timing when the recording material P enters the fixing nip portion in the present embodiment, and the power supplied to the fixing heater 16 is corrected to a predetermined value and supplied. FIG. 7 shows a flowchart of a method for correcting the input power to be substantially the same as the required power value required for the fixing heater 16 by using the environment sensor in consideration of the difference in the state of leaving the recording material P in the environment.
[0217]
The actual correction operation will be described below according to the flow.
[0218]
In FIG. 13, after the power is turned on, the image forming apparatus rises to a state in which a print signal can be received (d1). When a print command is received from a host computer (not shown) (d2), the paper mode is read from the print signal (d3). Then, the temperature Ta of the sub thermistor 19 is detected (d4). From the detected temperature Ta, the idle rotation power (W) is determined according to Table 7 (d5). Thereafter, the absolute moisture content X (g / kg: moisture content in 1 kg of dry air) of the atmosphere environment of the image forming apparatus is calculated by the environment sensor 50, and if the absolute moisture content is 21 (g / kg) or more, It is determined that the environment is a high water content environment, otherwise it is a general environment (d6). After that, the control circuit unit 21 drives the heater drive circuit 28 to start the temperature control of the heater 21 to control the temperature of the fixing belt 20 to a predetermined temperature (d7). After that, the recording material P is a plain paper, a rough paper (a recording material having a low heat conductivity and a small heat capacity), or a film medium (a recording material having a high heat conductivity and a large heat capacity) by the media sensor 51. Is determined (d8). Thereafter, as shown in Tables 6 and 8, the control circuit unit (CPU) 21 in the printer determines the paper mode and the properties of the recording material (whether it is plain paper, rough paper, or film media), and The sheet passing offset power (W) corresponding to the atmosphere environment (whether the environment is a high water content environment or a general environment) is determined (d9). When the temperature of the fixing belt 20 approaches a predetermined value and the startup temperature control ends (d10), the print temperature control temperature of 190 ° C. is set to the target temperature, and the temperature is controlled to the target temperature by PID control (d11). . Thereafter, the fixing device is driven and waits in a temperature-controlled state until it detects about 0.5 seconds before the recording material enters the fixing nip (d12).
[0219]
After detecting about 0.5 seconds before the recording material enters the fixing nip portion, the PID control is prohibited, and the idle rotation power (W) determined at d5 and the sheet passing offset power determined at d8. The power (W) which is the sum of (W) and (W) is supplied (d13), and the operation is continued until about 0.5 second elapses after the recording material enters the fixing nip (d14). Thereafter, the print temperature control temperature of 190 ° C. is set to the target temperature and the PID control is restarted, and the temperature of the fixing belt 20 is adjusted to the target temperature (d15).
[0220]
The PID control is continued until the printing ends (d16), and the temperature control ends at the same time when the print job ends (d17). This correction is based on a table (Table 7) of the detected temperature Ta of the sub thermistor 19 and the idle rotation offset power (W) in the control circuit unit (CPU) 21 in the printer, and the determination result of the paper mode and the media sensor 51. Offset at the time of paper passing with properties of recording material (whether it is plain paper, rough paper, film media) and atmosphere environment (whether high water content environment or general environment) as parameters Power E2 (W) determination tables (Tables 6 and 8) are provided, and the determination is performed based on the tables.
[0221]
As described above, when the PID control is prohibited for a fixed time before and after the timing at which the recording material P enters the fixing nip portion, and the power supplied to the fixing heater 16 is corrected to a predetermined value and supplied, the environment sensor is used. Is used to correct the power to approximately the required power in consideration of the difference in the state of leaving the recording material P in the environment, thereby performing more stable temperature control without causing a temperature change when the recording material P enters the fixing nip portion. be able to.
[0222]
Next, the effects on the temperature behavior of the fixing belt 20 and the image quality when this embodiment is used will be described by comparison with the conventional example and the third embodiment.
[0223]
The experimental conditions are as follows.
[0224]
The fixing device rotates at a process speed of 87 mm / sec, and the temperature is controlled so that the main thermistor detection temperature becomes constant at 190 ° C., and sufficient time has passed. In this state, the basis weight is 64 g / m2 as normal smooth paper. ² Office planner (Canon sales, product name) and 105g / m ² New NPI high-quality paper 105g (Nippon Paper Industries, trade name), a J / J (24.5 ° C / 45% Rh) environment-leaved paper and a H / H (30 ° C. 80%) environment-leaved paper continuously Paper was passed (16 sheets / min).
[0225]
At this time, the output of the main thermistor 18 was monitored as the fixing sleeve inner surface temperature.
[0226]
The electric power was measured by converting the output of the electric power value through the WT200 DIGITAL POWER METER manufactured by Yokogawa, similarly to A / D conversion by the KEYENCE PC temperature recorder NR250, and taking in the PC.
[0227]
The electric power supplied to the fixing heater 16 before passing the paper was substantially the same under each condition, and was about 80 W.
[0228]
Table 9 shows temperature ripples before and after paper passing in the conventional fixing device and the third and fourth embodiments.
[0229]
[Table 9]

[0230]
As can be seen from Table 9, more stable temperature control (temperature ripple of about 7 ° C.) was achieved by performing the present embodiment.
[0231]
This is based on the following grounds.
[0232]
The power required for maintaining the temperature during the idling of the sufficiently heated fixing device before paper passing is about 80 W, and when the paper mode is the plain paper in the J / J (24.5 ° C. 45%) environment (61). ~ 105g / m ² ), When performing power correction using the offset power at the time of paper passing in the paper mode, the input power is 275 W (80 + 195 W). On the other hand, NPI (105 g / m. ² ), When the continuous paper is fed (16 sheets / min), the heat capacity of the recording material is large, so that the electric power required to maintain the temperature of the fixing device is larger than when using the J / J environment-leaved paper. Temperature ripple will occur.
[0233]
In the present embodiment, the input power when the environment is not the high water content environment is 275 W, whereas the input power is 290 W (80 + 210 W) in the H / H environment which is the high water content environment.
[0234]
By the above control, appropriate power correction is always performed regardless of the environment in which the recording material is left, so that temperature control at a desired temperature ripple (about 7 ° C.) can be achieved.
[0235]
As described above, in the present embodiment, the temperature applied to the recording material P when entering the fixing nip portion is corrected in consideration of the difference in the state of leaving the recording material P in the environment, thereby achieving stable temperature control ( Temperature ripple of about 7 ° C.).
[0236]
In a high water content environment such as an H / H environment, the offset power during paper passing in the paper mode is changed. At this time, even if the required powers of the corresponding media in the paper mode do not exactly match, they need only be substantially the same, and the temperature fluctuation at that time may be within the desired temperature ripple.
[0237]
In general, when the printing speed is high, the difference in the offset power at the time of appropriate paper passing due to the difference in the amount of moisture absorption of the recording material P is further increased. May need to be distinguished. In such a case, it is possible to control the temperature within a desired temperature ripple by discriminating the open paper and the abandoned paper using information on a transfer bias at the time of transfer to the recording material P. As described above, in the present embodiment, when the PID control is prohibited for a predetermined time before and after the timing at which the recording material P enters the fixing nip portion, the power supplied to the fixing heater 16 is corrected to a predetermined power and supplied. By using an environment sensor to compensate for the substantially required power in consideration of the difference in the state of leaving the recording material P in the environment, more stable temperature control can be achieved without causing temperature fluctuation when the recording material P enters the fixing nip. Was able to do.
[0238]
As described above, by controlling the temperature ripple to a small value, accurate temperature control of the fixing member is performed. As a result, good fixing performance is exhibited, and there is no image defect that occurs when the fixing temperature control temperature is inappropriate. Thus, a high-quality image without uneven printing quality was obtained.
[0239]
<Embodiment 5>
In the present embodiment, a method for securing a more stable fixing performance by providing a section in which fixed power is supplied not only at the time of paper entry but also at the time of pre-rotation and reducing the temperature ripple during the pre-rotation. explain.
[0240]
(1) Example of image forming apparatus
In the present embodiment, the configuration of the image forming apparatus is the same as that of the first embodiment and is as shown in FIG. Therefore, duplicate description will be omitted.
[0241]
(2) Fixing device 12
In the present embodiment, the configuration of the fixing device is the same as in the first, second, and third embodiments, and is as shown in FIGS.
[0242]
(3) Startup temperature control of the fixing device
A control sequence of the fixing device according to the present embodiment will be described with reference to FIG. In the present embodiment, the startup temperature control is performed as follows.
[0243]
That is, “startup power (first power level) output” → “predetermined temperature detection” → “constant power (second power level) input” → “PID control”.
[0244]
For the “start-up power (first power level)”, 1000 W of power is supplied to the fixing heater 16 in order to ensure on-demand performance. With the rotation of the pressure roller 22, the fixing belt 20 is heated by the fixing heater 16 while being driven to rotate. In the present embodiment, immediately after the “start-up power (1000 W)” is applied, the process does not immediately shift to the “PID control”, and the detected temperature of the main thermistor 18 is a predetermined temperature (target temperature−20 ° C .: Since the target temperature is 190 ° C., when the temperature reaches 190 ° C.−20 ° C. = 170 ° C.), “the predetermined power (about 200 W) which is the second power level” is supplied for about 1.5 seconds. Thereafter, the process shifts to the "PID control", and thereafter, the power supplied to the fixing heater 16 is controlled by the "PID control".
[0245]
FIG. 22 shows a region where the feedback control is prohibited during the startup temperature control according to the present embodiment. In the above-described region, the power supplied to the fixing heater 16 is used to quickly start the fixing device temperature. FIG. 9 is a flowchart illustrating a method of switching after detecting a predetermined temperature during startup temperature control using two power levels of one power level and a second power level for stabilizing the fixing device temperature.
[0246]
The actual correction operation will be described below according to the flow.
[0247]
In FIG. 22, the image forming apparatus rises to a state in which a print signal can be received after the power is turned on (e1). When a print command is received from a host computer (not shown) (e2), the control circuit unit 21 drives the heater drive circuit 28 to control the rising temperature of the heater 21 to control the temperature of the fixing belt 20 to a predetermined temperature. Is started (e3). First, 1000 W is supplied as startup power (first power level) (e4). Thereafter, the temperature of the main thermistor 18 is monitored (e5), and the detected temperature of the main thermistor 18 is a predetermined temperature (target temperature −20 ° C .: In this embodiment, since the target temperature is 190 ° C., 190 ° C.-20 ° C.) = 170 ° C.), and waits while the fixing device is driven (e6).
[0248]
When the main thermistor 18 detects the predetermined temperature, 200 W is supplied to the fixing heater 16 as the predetermined power which is the second power level (e7). This electric power is supplied continuously for 1.5 seconds (e8), and after 1.5 seconds, the startup temperature control is terminated (e9), and the process shifts to PID control (e10). Thereafter, the same control as that of the fourth embodiment (similar to the control described in d11 to d17 in FIG. 13 and expressed as “normal temperature control” in FIG. 22) is performed. The above operation is continued until the printing is completed (e11), and when the print job is completed, the temperature control is completed (e12).
[0249]
As described above, the area where the feedback control is prohibited during the temperature control during startup is provided, and the power supplied to the fixing heater 16 includes the first power for promptly raising the fixing device temperature in the area. After switching to the second power level from the first power level after detecting a predetermined power during startup temperature control, using two power levels of the power level and the second power level for stabilizing the fixing device temperature. Thus, more stable temperature control can be performed without causing overshoot or temperature ripple.
[0250]
Next, a temperature profile of the fixing device and a measurement result of the fixing property and the glossiness when the present embodiment is used will be described.
[0251]
The contents of this experiment are as follows.
[0252]
1) Measurement method
The output of the main thermistor 18 was monitored as the inner surface temperature of the fixing belt 20 of the fixing device.
[0253]
The power was measured by A / D converting the output of the power value via a YOKOGAWA WT200 DIGITAL POWER METER by a KEYENCE PC temperature recorder NR250 and loading it into a PC.
[0254]
The glossiness (gloss) of the image after fixing was measured using the following method. As a measuring device, a gloss meter PG-3D manufactured by Nippon Denshoku Industries Co., Ltd. was used, and the measurement was performed by a 75-degree specular gloss measuring method in JISZ8741. As the toner amount on the recording material, the toner amount of a solid image portion of a so-called primary color of yellow, magenta, cyan, and black is about 0.5 to 0.6 mg / cm. ² , Red, green, blue, so-called secondary color solid portion is about 1.0 to 1.2 mg / cm ² , And the glossiness of the image after fixing was measured.
[0255]
As a rub test for evaluating the fixing property, a 5 mm × 5 mm monochromatic black image was formed on the recording material P, and 50 sheets were continuously printed at a speed of 16 ppm using the fixing device of the present embodiment. After fixing, a 200 g weight is placed on the image forming surface via Sylbon C (trade name), and the image forming surface is rubbed back and forth five times. ). It can be said that the smaller the rate of change of the reflection density (density reduction rate), the better the fixability. For the measurement, the density reduction rate at 9 points was measured on the first, second, third, fifth and tenth sheets of the 50 fixed recording materials, and the worst value was used.
[0256]
2) Experimental conditions
In this experiment, the fixing device is started from room temperature. Almost simultaneously with the start of the operation of the fixing device, the first electric power (1000 W) is supplied to the fixing heater 16, and the detected temperature of the main thermistor 18 is set to the target temperature of 170 ° C. (target temperature (190 ° C.)-20 ° C.). This power was turned on until.
[0257]
When the detected temperature of the main thermistor 18 reaches 170 ° C., the PID control is prohibited for about 1.5 seconds, and the second power (about 200 W) is supplied. 1.5 seconds after the second power was turned on, the target temperature for starting was set to 190 ° C., and the PID control was restarted, and the temperature was adjusted so as to be constant at the target temperature. After that, the grammage is 75 g / m ² Xerox 4024 (Xerox, trade name) was continuously fed.
[0258]
The supplied power of about 200 W is the power required to perform the temperature control at 190 ° C. in the idling state, that is, the power value required to maintain the temperature at the target temperature.
[0259]
Further, as a durability test, the fixing device according to the present embodiment was used to perform continuous printing of 150,000 sheets on two sheets intermittently, and the torque of the pressure roller after the durability was measured.
[0260]
3) Experimental results
FIG. 19 is a graph showing the power supplied to the fixing heater 16 and the temperature behavior of the inner surface of the fixing belt 20 in the fixing device in the startup temperature control in the case of using the present embodiment.
[0261]
As shown in FIG. 19, stable temperature control (temperature ripple of about 7 ° C., ± 3.5 ° C. with respect to the target temperature) including overshoot due to startup was exhibited.
[0262]
When the temperature ripple is about 7 ° C., in the in-line type electrophotographic color image forming apparatus used for the test, the gloss of the output printed matter is a single color and has a fluctuation range of about 4, and the secondary color In this case, the fluctuation range was about 6 (Table 10).
[0263]
[Table 10]

[0264]
As a durability test, a basis weight of 75 g / m ² 150,000 sheets of US letter size Xerox 4024 paper were printed intermittently. The worst value of the density lowering rate of the fixability was 13%, and there was little variation at each measurement point, and stable and good fixability could be obtained.
[0265]
Further, since fixing can be performed at a temperature close to the target temperature, a high-quality image can be obtained without fixing defects such as hot offset irrespective of a recording material or a printing pattern.
[0266]
When the driving torque after the durability test was measured, it was about 3.0 kgf · cm. At this time, no malfunction of the fixing device was observed.
[0267]
(4) Comparative example 2
A control sequence when starting up the fixing device in the comparative example will be described with reference to FIG.
[0268]
In this comparative example, the start-up control of “output of start-up power (1000 W)” → “detection of predetermined temperature (170 ° C.)” → “PID control” is performed. That is, the first power (1000 W) is supplied to the fixing heater 16, and when the detected temperature of the main thermistor 18 reaches 170 ° C., the target temperature for starting is set to 190 ° C., and the process shifts to PID control. It is characterized in that there is no section for inputting the second power.
[0269]
At this time, as shown in FIG. 21, overshoot occurs during PID control, and the temperature ripple accompanying the overshoot increases.
[0270]
The results of the measurement of the fixing belt temperature behavior, the evaluation of the fixing property, and the durability test results when the fixing device of this comparative example is used are shown.
[0271]
1) Experimental method
Since the experiment was performed in the same manner as the experiment using the fixing device in the fifth embodiment, the description is omitted here.
[0272]
2) Experimental conditions
In the fixing device in the room temperature state, the first power (1000 W) is supplied to the fixing heater 16 almost simultaneously with the operation, and the first power is supplied until the detected temperature of the main thermistor 18 reaches the target temperature 170 ° C. did. After that, the second power supply is not performed, and the process shifts to PID control in which the target temperature is set to 190 ° C. After that, the grammage is 75 g / m ² Xerox 4024 (Xerox, trade name) was continuously passed (16 sheets / min).
[0273]
Further, the same durability test as that described in the fifth embodiment was performed.
[0274]
3) Experimental results
FIG. 21 is a graph showing the power supplied to the fixing heater 16 and the temperature behavior of the back surface of the fixing belt 20 at the startup temperature control in the conventional example.
[0275]
As shown in FIG. 21, the back surface temperature of the fixing belt 20 rises to a desired temperature in about 9 seconds, but after that, overshoot occurs, and the temperature rises to about 210 ° C. Thereafter, the back surface temperature of the fixing belt 20 repeatedly moved up and down, and it took about another 10 seconds until the temperature ripple was stabilized within 7 ° C. with respect to the target temperature of 190 ° C.
[0276]
When such an overshoot occurs, in the in-line type electrophotographic color image forming apparatus used for the test, the gloss of the output printed matter fluctuates by about 8 in a single color within one sheet of output paper, and In the case of the secondary color, the value fluctuated by about 13 and the image quality was lowered (Table 11).
[0277]
[Table 11]

[0278]
In addition, the worst value of the density reduction rate of the fixing property was 22%. If the density reduction rate exceeds 20%, not only characters are peeled off when the image is used by the user, the halftone image is blurred, but also hands, clothes, and other paper are stained. Or other problems occurred.
[0279]
Further, when the paper is passed during the overshoot, there is a problem that a fixing failure such as a hot offset occurs regardless of the recording material or the print pattern.
[0280]
When the driving torque of the fixing device after the durability test was measured, it was about 4.5 kgf · cm. At this time, slippage of the fixing belt may occur during driving of the fixing device depending on conditions.
[0281]
(5) Consideration
First, overshoot and temperature ripple will be described.
[0282]
The reason why an effect can be obtained when this embodiment is used is as follows. In the conventional fixing device, since the thermal conductivity of silicone rubber used for the elastic layer of the fixing belt 20 is small and the heat capacity is large, the temperature responsiveness of the fixing belt 20 to the temperature rise of the fixing heater 16 is poor. Further, since the detection timing is delayed due to the position of the main thermistor 18 being separated from the fixing heater 16 which is a heat-generating portion, when the temperature rises sharply as at the time of startup, the main thermistor 18 Indicates a value that is significantly lower than the temperature of the fixing nip portion. Therefore, despite the fact that the temperature of the fixing heater 16 has actually risen sufficiently, the detected temperature of the main thermistor 18 has not risen sufficiently, so that high power continues to be supplied and overshoot occurs.
[0283]
Further, once an overshoot occurs, the main thermistor 18 detects that the temperature is higher than a desired temperature after a certain time lag, and performs control to suppress power. At this time, even if the power is suppressed, the amount of heat generated by the fixing heater 16 is reduced, and the temperature of the fixing nip becomes appropriate, the main thermistor 18 recognizes that the detected temperature is high. For this reason, the power is suppressed more than necessary, and an undershoot occurs. This repetition of overshoot and undershoot appears as a temperature ripple.
[0284]
Further, in the present fixing device, in order to use a large power (1000 W) for the start-up power in order to secure the on-demand property in a state in which the fixing belt 20 having a poor temperature response is used, feedback such as PID control is performed immediately thereafter. When returning to the control, the fluctuation range of the electric power is large and the control becomes unstable with a large temperature fluctuation.
[0285]
Here, when the detected temperature of the main thermistor 18 reaches a predetermined temperature (target temperature −20 ° C.) after the start-up power is supplied, the predetermined power (about 200 W) is supplied for about 1.5 seconds to perform PID control. The overshoot can be reduced and the temperature ripple associated with the overshoot can be reduced by making the power fluctuation at the time of the transition to relatively gentle.
[0286]
Next, the durability of the fixing member will be described.
[0287]
When the temperature of the inner surface of the fixing sleeve 20 reaches about 210 ° C. during startup as in the conventional example, the grease interposed between the fixing heater 16 and the inner surface of the fixing belt 20 rapidly deteriorates. The kinetic frictional force between the fixing belt 20 and components inside the belt such as the fixing heater 16 is greatly affected by the state of grease in particular, and when the amount is reduced by moving to an unnecessary portion of the grease, It is known that when the grease itself is deteriorated, the dynamic friction force increases.
[0288]
For this reason, as the durability of the fixing device advances, the torque of the fixing device increases, and in the worst case, the kinetic friction force between the fixing heater 16 and other components inside the belt is reduced by the pressure roller 22 or the recording material P. , And the slip of the fixing belt 20 occurs.
[0289]
The kinetic frictional force between the fixing belt 20 and components inside the belt such as the fixing heater 16 is the largest factor among the loads on the driving means when the fixing device is driven. That is, the driving torque of the fixing device can be substituted by the measured value.
[0290]
The driving torque in the initial state of the fixing device is about 1.5 kgf · cm, and it is known that the slip of the fixing belt 20 may occur when the driving torque exceeds about 4.0 kgf · cm. .
[0291]
In the fifth embodiment and the comparative example 2, the slip of the fixing belt 20 has been described as an example in which the durable life is shortened. However, when the overshoot of the fixing device is large, each member in the fixing device is used. It is needless to say that the present embodiment has the effect of extending the life of each member in the fixing device by preventing overshoot using the present embodiment.
[0292]
The value of the second power (about 200 W) described in the fifth embodiment is the power required to stably maintain the temperature control at 190 ° C. in the idling state of the fixing device, and is obtained experimentally. It is a thing. However, the power input here does not have to exactly match the required power, but may be substantially the same. That is, after the second power is supplied and the fixing device temperature is stabilized, no significant power fluctuation occurs even by the PID control, so that the temperature ripple can be reduced.
[0293]
As described above, in the present embodiment, an area where the feedback control is prohibited during the startup temperature control is provided, and in the above-described area, the electric power supplied to the fixing heater 16 is used to quickly start the fixing device temperature. It has two power levels, a power level and a second power level for stabilizing the fixing device temperature, and when a predetermined temperature is detected during startup temperature control with the first power applied, By switching to the second power and returning to the feedback control with the fixing device temperature stabilized, more stable temperature control could be performed without overshooting.
[0294]
As described above, by suppressing the overshoot and the accompanying temperature ripple to a small value, the life of the fixing device is prolonged, and accurate temperature control of the fixing member is performed. There was no image defect that occurred when the image was inappropriate, and a high-quality image without print quality unevenness such as gloss could be obtained.
[0295]
<Embodiment 6>
In the present embodiment, an area where the feedback control is prohibited during the startup temperature control is provided. In the area, the power supplied to the fixing heater 16 includes the first power level for promptly raising the fixing device temperature. And a second power level for stabilizing the fixing device temperature, and has a two-stage power level, and when a predetermined temperature is detected during startup temperature control at the first power level, the second power level A method of performing more stable temperature control without causing overshoot by correcting the second power level based on the detected temperature of the sub thermistor 19 before startup in the fixing device characterized by switching. explain.
[0296]
In this embodiment, the general configuration and control of the fixing device are the same as those in the fifth embodiment. However, when the power supplied to the fixing heater 16 is corrected, the correction is performed to substantially the required power in consideration of the heat storage condition of the fixing device.
[0297]
The configuration of the image forming apparatus is the same as that of the first embodiment, and is as shown in FIG. The configuration of the fixing device is the same as that of the first embodiment, and is as shown in FIGS. Therefore, a duplicate description will be omitted.
[0298]
In the present embodiment, when correcting the second power level to be supplied to the fixing heater 16 during the startup temperature adjustment, the correction is made to substantially the required power in consideration of the heat storage condition of the fixing device.
[0299]
In other words, the second power level required to maintain the temperature of the fixing device at the target temperature after the detection of the predetermined temperature during the start-up temperature control varies depending on the heat storage condition of the fixing device. For example, when a predetermined temperature is detected after power-on of the fixing device from a room temperature state, a second power level required to maintain the fixing device at the target temperature is about 200 W, and a sufficiently warmed fixing device is used. Since the second power level required to maintain the fixing device at the target temperature when the device is started up is about 80 W, the heat storage condition of the fixing device is taken into consideration, and the fixing heater is determined by the heat storage condition of the fixing device. The power to be supplied to the 16 can be adapted to different situations.
[0300]
In the present embodiment, the predetermined power value is changed by estimating the heat storage condition of the fixing device from the temperature detected by the sub thermistor 19 at the start of energization.
[0301]
FIG. 16 shows a graph in which the relationship between the temperature of the heater holder 17 and the value of the electric power required to maintain the temperature of the fixing device at a predetermined value is plotted. As described above, the heater holder temperature and the value of the electric power required to maintain the temperature of the fixing device at a predetermined value show the relationship shown in FIG. 16 with good reproducibility.
[0302]
[Table 12]

[0303]
Therefore, in the present embodiment, when the fixing device is restarted after the print job is completed with residual heat remaining, as shown in Table 12, according to the detected temperature of the sub thermistor 19 at the time of energization start, The temperature of the heater holder 17 after startup is predicted, and the value of the second power level is determined.
[0304]
Specifically, when the detected temperature of the sub-thermistor 19 at the start of energization is 40 ° C. or lower, the heater holder temperature after startup is expected to be 55 ° C. or lower. 200W is used as the value of.
[0305]
Similarly, when the sub-thermistor detection temperature before the start of the startup is 41 to 55 ° C., the startup is 2; when the temperature is 56 to 75 ° C., the startup is 3; The power level is determined to be 4, the startup is 5 when the temperature is 96 to 125 ° C., and the startup is 6 when the temperature is 126 ° C. or higher, and the value of the second power level is determined.
[0306]
FIG. 23 shows a region in this embodiment in which feedback control is prohibited during startup temperature control. In the region, the power supplied to the fixing heater 16 is used to quickly raise the fixing device temperature. One power level and a second power level for stabilizing the fixing device temperature, and have two power levels. FIG. 9 is a flowchart showing a method for correcting the second power level to a required power value in consideration of the heat storage condition of the fixing device based on the detected temperature of the sub thermistor 19 before startup when switching the input power level to the power level. Show.
[0307]
The actual correction operation will be described below according to the flow.
[0308]
In FIG. 23, after the power is turned on, the image forming apparatus rises to a state in which a print signal can be received (f1). When a print command is received from a host computer (not shown) (f2), first, the temperature Ta of the sub thermistor is detected (f3), and a predetermined power (second power) is obtained from the result of the detected temperature of the sub thermistor according to the table (Table 12). The power level (W) is determined (f4). Thereafter, the control circuit unit 21 drives the heater drive circuit 28 to start the temperature control of the heater 21 to control the temperature of the fixing belt 20 to a predetermined temperature (f5). First, 1000 W is supplied as startup power (first power level) (f6). Thereafter, the temperature of the main thermistor is monitored (f7), and the detected temperature of the main thermistor 18 is a predetermined temperature (target temperature −20 ° C .: in this embodiment, the target temperature is 190 ° C .; 170 ° C.) is detected (f8).
[0309]
When the detected temperature of the main thermistor 18 reaches a predetermined temperature, the second power level determined at f4 is output (f9). After this operation is continued for 1.5 seconds (f10), the start-up temperature control ends (f11), returns to the PID control, and the temperature is controlled at the target temperature (f12). Thereafter, the normal temperature control (the same control as described in d11 to d17 in FIG. 13) is continued until the printing is completed (f13), and when the print job is completed, the temperature control is completed (f14).
[0310]
As described above, the area where the feedback control is prohibited during the temperature control during startup is provided, and the power supplied to the fixing heater 16 includes the first power for promptly raising the fixing device temperature in the area. And a second power level for stabilizing the fixing device temperature. After detecting a predetermined temperature during startup temperature control, the first power level is changed to a second power level. When switching to the second power level, the second power level is corrected to a required power value in consideration of the heat storage condition of the fixing device based on the detected temperature of the sub thermistor 19 before startup, so that overshoot does not occur. Stable temperature control can be performed.
[0311]
The effect obtained by using this embodiment is basically the same as that of the first embodiment, and will not be described here. However, in the present embodiment, in the fixing device under a wide range of conditions from a fixing device in a room temperature state to a fixing device in a sufficiently warm state, the power to be supplied at the time of startup can be determined with high accuracy, so that more stable temperature control is performed. be able to.
[0312]
In this way, stable temperature control (temperature ripple within about 7 ° C.) was achieved regardless of the heat storage condition of the fixing device.
[0313]
As described above, by suppressing the overshoot and the accompanying temperature ripple to a small value, the life of the fixing device is prolonged, and accurate temperature control of the fixing member is performed. There was no image defect that occurred when the image was inappropriate, and a high-quality image without print quality unevenness such as gloss could be obtained.
[0314]
Further, here, the heater holder temperature is predicted using the detected temperature of the sub thermistor 19 before startup, and the predetermined power value is determined. However, without using the sub thermistor, the heater holder temperature is predicted from the number of printed sheets, and the predetermined power value is obtained. A method of determining a value may be used.
[0315]
<Embodiment 7>
In the present embodiment, an area where the feedback control is prohibited during the start-up temperature control is provided, and the power supplied to the fixing heater 16 includes a first power level for promptly raising the fixing device temperature in the area. And a second power level for stabilizing the fixing device temperature, when switching from the first power level to the second power level after detecting a predetermined temperature during startup temperature control. Further, the second power level is corrected to a required power value in consideration of the heat storage condition of the fixing device based on the detected temperature of the thermistor brought into contact with the heater holder 17, so that overshoot does not occur and the second power level is further stabilized. A method for performing the temperature control described above will be described.
[0316]
In the present embodiment, the general configuration and control of the fixing device are the same as those in the first embodiment. However, as shown in FIG. 17, a third thermistor 70 as a third temperature detecting means is provided in the heater holder 17. Is installed. When the power supplied to the fixing heater 16 is corrected, the third thermistor 70 is used to correct the power to a substantially required power value in consideration of the heat storage condition of the fixing device.
[0317]
The configuration of the image forming apparatus is the same as that of the first embodiment, and is as shown in FIG. The configuration of the fixing device is as shown in FIGS. Therefore, a duplicate description will be omitted.
[0318]
In the present embodiment, when the heat storage condition of the fixing device is considered, the heat storage condition is directly measured using the third thermistor 70 in contact with the heater holder 17.
[0319]
By doing so, the heat storage condition of the fixing device can be obtained more accurately.
[0320]
FIG. 16 shows a plot of the relationship between the temperature of the heater holder 17 and the power value required to maintain the fixing device temperature. As described above, the relationship between the heater holder temperature and the predetermined power value required for maintaining the temperature of the fixing device is shown in FIG. 7 with good reproducibility.
[0321]
By using the predetermined power value determined by the linear interpolation in FIG. 16 from the temperature detected by the third thermistor 70, the required power value can be obtained more accurately.
[0322]
The effect of the present embodiment is basically the same as that of the sixth embodiment, and therefore will not be described here. However, in the present embodiment, in a fixing device under a wide range of conditions from a fixing device in a room temperature state to a fixing device in a sufficiently warmed state, the value of the second power level to be supplied at startup can be more accurately determined. Very stable start-up temperature control can be performed.
[0323]
By doing so, stable start-up temperature control (temperature ripple within about 7 ° C.) could be achieved regardless of the heat storage condition of the fixing device.
[0324]
As described above, by suppressing the overshoot and the accompanying temperature ripple to a small value, the life of the fixing device is prolonged, and accurate temperature control of the fixing member is performed. There was no image defect that occurred when the image was inappropriate, and a high-quality image without print quality unevenness such as gloss could be obtained.
[0325]
<Others>
1) As described above, in the above-described first to fourth embodiments, the process speed is 87 mm / sec, the print speed is 16 sheets / min, the temperature adjustment temperature is 190 ° C., and the predetermined power supply time is the recording at the start of sheet feeding. The description has been made from about 0.5 seconds to about 1 second before the material enters. However, depending on the type of recording material and the image quality of the image to be obtained, or depending on conditions such as obtaining better fixing properties, it may be better to set the process speed, print speed, and temperature control temperature differently. Can be Even in such a case, by applying the method of the present invention, it is possible to perform accurate temperature control with small temperature fluctuation, and the same effect can be obtained. At this time, it goes without saying that the value of the predetermined power to be corrected and the input time of the predetermined power are different depending on the process speed, the printing speed, and the regulated temperature.
[0326]
2) In each of the above-described embodiments, a case has been described in which PID control is basically used as power control for performing temperature control. This is used as a control method that quickly approaches the target temperature and is strong against disturbance. Therefore, temperature control can be performed by using P control, PI control, or other feedback control, and the same effect can be obtained.
[0327]
3) In Embodiments 1 to 7 described above, in order to determine the value of the predetermined power in consideration of the difference in the heat capacity of the recording material and the heat conductivity from the fixing device, a paper mode, a media sensor, and an environment sensor are used. It was explained using. However, this method can also be applied by directly measuring the difference in heat capacity of the recording material and the heat transfer from the fixing device before the recording material actually enters the fixing device, and reflecting the result in the value of the predetermined power. The present invention can be applied, and temperature control can be performed with higher accuracy in terms of temperature control as well.
[0328]
4) In the first to fourth embodiments, in order to determine the value of the predetermined power in consideration of the heat storage condition of the fixing device, the number of prints of the fixing device and the temperature of the sub thermistor 19 at the start of energization are determined. The present invention can be applied to a method in which a new thermistor is actually added to the inside of the fixing device, for example, the heater holder 17 or the pressure roller 22, and the heat storage state of the fixing device is directly measured. In addition, temperature control can be performed with higher accuracy in terms of the same or similar temperature control.
[0329]
5) In the above-described fifth to seventh embodiments, the process speed is 87 mm / sec, the temperature control temperature is 190 ° C., and the detection time of the main thermistor 18 is 170 ° C. (target temperature−20 ° C.) during the predetermined power supply time. After about 1.5 seconds. However, depending on the type of the recording material and the image quality of the image to be obtained, or depending on conditions such as obtaining a better fixing property, even if the process speed, the print speed, and the temperature control temperature are set differently, the present invention can be applied. By applying this, it is possible to perform accurate temperature control with small temperature fluctuations. At this time, it goes without saying that the value of the predetermined power to be corrected and the input time of the predetermined power are different depending on the process speed and the regulated temperature.
[0330]
6) In the above-described fifth to seventh embodiments, the start-up power control has been described as a two-step control, but a control of three or more steps may be used. In this case, more precise control such as setting of an electric power value can be performed, and more stable temperature control can be performed.
[0331]
7) In each of the above-described embodiments, the power supplied to the fixing heater 16 is described as a control for correcting the power supplied to the fixing heater 16 with a predetermined power required for the fixing device suitable for each condition. As a method, the target temperature at the time of temperature adjustment may be temporarily changed, and the correction may be made by changing the target temperature so that the power supplied to the fixing heater 16 eventually becomes the predetermined power required for the fixing device. That is, in the above-described first to fourth embodiments, the recording material P enters the target temperature of the main thermistor 18 or the sub thermistor 19 for about 1 second from about 0.5 second before the recording material P enters the fixing nip portion. In the method of setting higher than the previous state and controlling so that electric power required to maintain the fixing device at a predetermined temperature is supplied as a result, and in the above-described fifth to seventh embodiments, the main thermistor 18 is controlled. After the detected temperature reaches 170 ° C. (target temperature −20 ° C.), the target temperature is set high for about 1.5 seconds, and as a result, power necessary to maintain the fixing device at a predetermined temperature is supplied. Such a control method may be used, and the same effect is obtained.
[0332]
8) In each of the above-described embodiments, the first temperature detecting unit of the fixing device is described as being located at a place different from the heating element. However, it is assumed that the first temperature detecting unit is located on the heating element. The same effect can be obtained, for example, even when the device is located in a place different from the heat generation region or when the response of the temperature detecting means is slow.
[0333]
9) In each of the above embodiments, the heat capacity of the fixing belt 20 is at least 4.2 × 10 ^-2 J / cm ² ・ ℃ or more 4.2J / cm ² The description has been made using the fixing device composed of the one of ° C. This is because the heat capacity of the fixing belt 20 is 4.2 × 10 ^-2 J / cm ² If the temperature is higher than ° C, the on-demand property is impaired, and the heat capacity of the fixing belt 20 is 4.2 J / cm. ² If the temperature is lower than or equal to ° C., the elastic layer thickness of the fixing belt 20 cannot be sufficiently secured, and image defects such as uneven gloss appear. However, the present invention can be applied to a fixing device having a fixing belt having a heat capacity other than the above, and the same effect can be obtained.
[0334]
10) In the embodiment of the present invention, the fixing device in which the fixing belt 20 is provided with the elastic layer has been described. However, the presence or absence of the elastic layer is not particularly limited as long as the fixing member has a heat capacity of the degree described in the embodiment.
[0335]
11) Also, the description has been given of a fixing device using a ceramic heater having a resistance heating element formed on a ceramic substrate as a heating element. This is because it is used as a heating element of a low-cost color on-demand fixing device, and a halogen lamp or an electromagnetic induction heating member can be used as the heating element, and the same effect can be obtained.
[0336]
12) Further, the first and second fixing members for forming the fixing nip are not limited to the forms of the fixing belt and the pressure roller of the first to seventh embodiments. It is also possible to provide an apparatus in which both the first and second fixing members are provided with a heating element (heat source).
[0337]
13) The heating element does not necessarily have to be located in the fixing nip 27. For example, the heat source may be disposed upstream or downstream of the fixing nip 27 in the fixing belt moving direction.
[0338]
14) In addition, the fixing device of the embodiment is a driving device for a rotating pressurizing member, but a device of a type in which a driving roller is provided on an inner peripheral surface of an endless fixing belt and driven while applying tension to the fixing belt. Good.
[0339]
15) In the present invention, the fixing device includes not only a fixing device that heats and fixes an unfixed image on a recording material as a permanent image, but also an image heating device that tentatively fixes an unfixed image on a recording material, and an image bearing device. An image heating device that reheats the recording material to improve the image surface properties such as glossiness is also included.
[0340]
16) The image forming method of the image forming apparatus is not limited to the electrophotographic method, but may be an electrostatic recording method, a magnetic recording method, or the like, or may be a transfer method or a direct method.
[0341]
【The invention's effect】
As described above, according to the present invention, accurate temperature control of the fixing member is performed even when a fixing belt having an elastic layer is used as a fixing member in the fixing device, and as a result, there is no print quality unevenness such as gloss. It is possible to provide a fixing device that can obtain a high-quality image and has high durability and a long life, and an image forming apparatus equipped with the fixing device.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a color image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view of a fixing device according to the first to seventh embodiments of the present invention.
FIG. 3 is a perspective model view showing a positional relationship among a fixing heater, a main thermistor, and a sub thermistor in the first to seventh embodiments of the present invention.
FIG. 4 is a schematic diagram of a configuration of a ceramic heater as a heating element.
FIG. 5 is a block diagram of a control circuit unit (CPU) and a fixing heater driving circuit unit of the fixing device of the present invention.
FIG. 6 is a graph showing a change in temperature and an input power before and after a medium is passed using a conventional fixing device.
FIG. 7 is a graph of a change in temperature and an input power before and after a medium is passed using a fixing device according to the first embodiment of the present invention;
FIG. 8 is a schematic configuration diagram showing a media sensor.
FIG. 9 is a graph of electric power required when continuously passing each environmentally-leaved paper.
FIG. 10 is a flowchart illustrating a method of correcting the power required by the fixing heater 16 to be substantially equal to the required power in consideration of a difference in heat capacity depending on the basis weight of the recording material P according to the first embodiment of the present invention.
FIG. 11 shows a method of detecting a recording material P having special heat conductivity from a fixing device using a media sensor, and correcting the recording material P to substantially the same as the required power value required for the fixing heater 16 in consideration of the heat conductivity. Flowchart
FIG. 12 is a flowchart of a method for correcting the required power value necessary for the fixing heater 16 to be substantially the same as that of the fixing device in consideration of the heat storage condition of the fixing device.
FIG. 13 is a flowchart of a method for correcting the required power value required for the fixing heater 16 to be substantially the same as that of the recording material P by using an environment sensor in consideration of a difference in a state of leaving the recording material P in an environment
FIG. 14 is a diagram showing electric power supplied to a fixing heater and a temperature of a fixing belt in a conventional fixing device at a startup temperature control.
FIG. 15 is a diagram showing the power supplied to the fixing heater and the temperature of the fixing belt at the startup temperature control in the fixing device according to the fourth embodiment of the present invention.
FIG. 16 is a diagram in which a relationship between a temperature of a heater holder and a predetermined power value is plotted.
FIG. 17 is a schematic sectional view of a fixing device according to a seventh embodiment of the present invention.
FIG. 18 is a power control diagram of a fixing device according to a fourth embodiment of the present invention.
FIG. 19 is a startup temperature profile of the fixing device according to the embodiment of the present invention.
FIG. 20 is a diagram illustrating a startup power control diagram of a conventional fixing device.
FIG. 21 is a startup temperature profile diagram of a conventional fixing device.
22 does not perform PID control for a fixed time in accordance with the entry timing of the recording material P at the start of sheet feeding, and corrects the electric power supplied to the fixing heater to a predetermined value when supplying the electric power to the fixing heater. Flowchart for a method of correcting the required power value required for the fixing heater 16 to be substantially the same as the required power value in consideration of the difference in the state of leaving the recording material P in the environment.
FIG. 23 is a flowchart of a method for correcting the required power value required for the fixing heater 16 to be substantially equal to the required power value of the fixing heater 16 in consideration of a difference in a state of leaving the recording material P in an environment using an environment sensor.
FIG. 24 is a schematic cross-sectional view of a fixing device of a conventional belt fixing method.
FIG. 25 is a schematic cross-sectional view of a fixing device using a thermistor of a fixing belt inner surface contact type in a conventional belt fixing method.
[Explanation of symbols]
1M, 1C, 1Y, 1Bk Image forming unit
2a, 2b, 2c, 2d Photosensitive drum
3a, 3b, 3c, 3d Charging roller
4a, 4b, 4c, 4d Developing device
5a, 5b, 5c, 5d Transfer roller
6a, 6b, 6c, 6d Drum cleaning device
12 Fixing device
16 Ceramic heater (heating body)
18 Main thermistor (first temperature detecting means)
19 Sub thermistor (first temperature detecting means)
20 Fixing belt (first rotating body)
21 Control circuit unit (power control unit)
22 Pressure roller (second rotating body)
28 Power supply (power supply unit)
40 Intermediate transfer belt
44 Secondary transfer roller
45 Belt cleaning device
46 Registration Roller
50 Environmental Sensor
51 Media sensor
P recording material
N (primary) transfer unit
M (secondary) transfer unit
t toner

Claims (36)

At least a heating element, a power supply unit for supplying electric power to the heating element, at least one or more temperature detecting means, a first rotating element that moves together with the recording material, and a pressure contact part with the recording material are formed. Temperature control of the first rotating body by feedback-controlling the power supplied from the power supply unit to the heating body based on the temperature detected by the temperature detecting means. In a fixing device that heats the recording material holding the image in the press-contact portion by nipping and conveying,
Before the temperature detecting means detects a temperature change due to the entry of the recording material into the pressure contact portion, power required for heating supplied to the heating element is corrected by a predetermined power. . 2. The fixing device according to claim 1, wherein the temperature detection unit performs a temperature detection at a location different from a heating area of the heating element. 3. The fixing device according to claim 1, wherein the predetermined power value is substantially equal to a power value required after the recording material enters the fixing device. 4. The fixing device according to claim 1, wherein the feedback control is not performed during the predetermined power supply. The fixing device according to claim 1, wherein the output of the predetermined power value is achieved by changing a target temperature of the temperature detection unit. When the temperature detecting means is the first temperature detecting means, in addition to the first temperature detecting means, has a second temperature detecting means, the place where the temperature detection of the second temperature detecting means is the The output of the value of the predetermined power is achieved by varying a target temperature of the second temperature detecting means in a place closer to or within a heating area of the heating element than the first temperature detecting means. The fixing device according to claim 1, wherein: 7. The fixing device according to claim 1, wherein the value of the predetermined power is determined based on a heat storage condition of the fixing device. When the temperature detecting means is the first temperature detecting means, in addition to the first temperature detecting means, has a second temperature detecting means, the place where the temperature detection of the second temperature detecting means is the Before starting the fixing device at the start of the image forming operation, the detected temperature of the second temperature detecting means is set at a location closer to or within the heat generating area of the heating element than the first temperature detecting means. The fixing device according to claim 7, wherein a value of the predetermined power is determined. 9. The fixing device according to claim 1, wherein the value of the predetermined power is determined based on the number of prints of the fixing device. 10. The fixing device according to claim 1, wherein the value of the predetermined power is determined from a heat capacity of the recording material. The fixing device according to claim 1, wherein the value of the predetermined power is determined based on a basis weight of the recording material. The fixing device according to claim 10, wherein the value of the predetermined power is determined based on a paper mode to which a recording material belongs. 13. The fixing device according to claim 10, wherein the value of the predetermined power is determined based on a degree of moisture absorption of the recording material. 14. The fixing device according to claim 1, wherein the value of the predetermined power is determined based on whether heat transfer from the fixing device to the recording material is good or bad. 15. The fixing device according to claim 14, wherein when the recording material is rough paper, the value of the predetermined power is determined in consideration of heat transfer from the fixing device. 15. The fixing device according to claim 14, wherein when the recording material is a film, the value of the predetermined power is determined in consideration of heat transfer from the fixing device. At least a heating element, a power supply unit for supplying electric power to the heating element, at least one or more temperature detecting means, a first rotating element that moves together with the recording material, and a pressure contact part with the recording material are formed. Temperature control of the first rotating body by feedback controlling power supplied from the power supply unit to the heating body based on the temperature detected by the temperature detecting means. In the fixing device that heats the recording material holding the image in the press-contact portion while nipping and conveying,
When starting the fixing device at the start of printing, providing an area for inhibiting the feedback control,
In the region, at least two power levels of a first power level for quickly raising the fixing device temperature and a second power level for stabilizing the fixing device temperature, and thereafter the feedback control is performed. A fixing device characterized by shifting. 18. The fixing device according to claim 17, wherein the temperature detection unit performs temperature detection at a location different from a heating area of the heating element. 19. The fixing device according to claim 17, wherein the output of the value of the predetermined power is achieved by changing a target temperature of the temperature detecting unit. When the temperature detecting means is the first temperature detecting means, in addition to the first temperature detecting means, has a second temperature detecting means, the place where the temperature detection of the second temperature detecting means is the The output of the value of the predetermined power is achieved by varying a target temperature of the second temperature detecting means in a place closer to or within a heating area of the heating element than the first temperature detecting means. The fixing device according to claim 17, wherein: 21. The fixing device according to claim 17, wherein a value of a power level after the second power level is determined based on a heat storage state of the fixing device. When the temperature detecting means is the first temperature detecting means, in addition to the first temperature detecting means, has a second temperature detecting means, the place where the temperature detection of the second temperature detecting means is the Before starting the fixing device at the start of the image forming operation, the detected temperature of the second temperature detecting means is set at a location closer to or within the heat generating area of the heating element than the first temperature detecting means. 22. The fixing device according to claim 21, wherein a value of a power level after the second power level is determined. 23. The fixing device according to claim 21, wherein a value of a power level after the second power level is determined based on the number of printed sheets of the fixing device. In addition to the first and second temperature detecting means, a third temperature detecting means is provided, and a place for performing the temperature detection of the third temperature detecting means is located within the heat generating region of the heating element and the first temperature detecting means. 22. A fixing device constituting part excluding a rotating body, wherein a value of a power level after the second power level is determined from a temperature detected by the third temperature detecting means. 23. The fixing device according to any one of 23. Claims 1, wherein the heat capacity of the first rotary member is ^{4.2 × 10 -2 J / cm 2} · ℃ than 4.2J / cm ² · ℃ less according to any one of the 24 Fixing device. The heat capacity of the first rotating body is not less than 8.82 × 10 ^-2 J / cm ² · ° C. and not more than 18.9 × 10 ^-2 J / cm ² · ° C. 25. The fixing device according to any one of the above. 27. The fixing device according to claim 1, wherein a fixing belt having a belt-shaped member provided with an elastic layer is used as the first rotating body. The fixing device according to claim 27, wherein a base material of the fixing belt is made of a heat-resistant resin. The fixing device according to claim 27, wherein a base material of the fixing belt is made of metal. 30. The fixing device according to claim 27, wherein a release layer is provided on the outermost layer of the fixing belt. 31. The fixing device according to claim 1, wherein a linear heating element is used as the heating element. 32. The fixing device according to claim 1, wherein a ceramic heater having a resistance heating element formed on a ceramic substrate is used as the heating element. 33. The fixing device according to claim 1, wherein a resin material is used for a heating element holding member that holds the heating element. The fixing device according to claim 33, wherein the heating element holding member is made of a liquid crystal polymer. An image forming apparatus comprising the fixing device according to claim 1. The image forming apparatus according to claim 35, wherein the image forming apparatus is a color image forming apparatus that forms a color image by superimposing a plurality of color toner images.

Images