JP4193429B2

JP4193429B2 - Image forming apparatus

Info

Publication number: JP4193429B2
Application number: JP2002198424A
Authority: JP
Inventors: 和善伊藤; 康博上原
Original assignee: Fuji Xerox Co Ltd; Fujifilm Business Innovation Corp
Current assignee: Fujifilm Business Innovation Corp
Priority date: 2002-07-08
Filing date: 2002-07-08
Publication date: 2008-12-10
Anticipated expiration: 2022-07-08
Also published as: JP2004037412A

Description

【０００１】
【発明の属する技術分野】
本発明は、定着部材又は中間転写体に接触して温度を検出する温度検出装置を備えた画像形成装置に関する。
【０００２】
【従来の技術】
一般に、粉状のトナーを用いる画像形成装置においてトナー像を定着する工程は、トナー像を記録媒体上に静電的に転写した後、加熱部材と加圧部材との間に記録媒体を挟み込んで、トナー像を加熱して記録媒体に圧着する方法が広く採用されている。また、トナー像を中間転写体に一次転写した後、中間転写体上でトナー像を加熱し、このトナー像を記録媒体に圧着して、二次転写と定着とを同時に行う画像形成装置も知られている。
【０００３】
上記加熱部材又は中間転写体を加熱する手段として、特開平１０−２５４２６３号公報、特開平１０−３０１４１５号公報、特開平１１−３５２８０４号公報等には、加熱部材又は中間転写体に導電性層を設け、電磁誘導加熱によって導電性層を発熱させるものが記載されている。電磁誘導加熱は、変動磁界を発生する励磁コイルを導電性層と対向するように配置し、導電性層を貫通する磁束を発生させることにより、導電性層に渦電流が生じ発熱するものである。電磁誘導加熱によれば、加熱部材又は中間転写体を直接加熱することができ、極めて短い時間で導電性層を発熱させることができる。このため、装置の起動時や待機状態から復帰する時に、効率良くウォーミングアップを行うことができ、消費電力を低減することができる。
【０００４】
一方、トナー像を適切な温度で加熱して良好な定着を行なうために、加熱部材又は中間転写体の温度を測定して、所定の温度に維持する必要がある。温度測定の手段としては、一般に、被測定体に接触させて温度を測定する、サーミスタや熱電対等の温度センサが用いられる。
特開平９−２９２７９０号公報に記載の定着装置は、図９に示すように、無張架の状態で支持されたフィルム部材２０１と、フィルム部材２０１の内周面に近接して配置されたフィルムガイド部材２０２と、フィルム部材２０１に圧接された加圧ロール２０３と、フィルム部材２０１及び加圧ロール２０３のそれぞれの内側に配置され、これらを加熱する第１の電磁誘導加熱装置２０４及び第２の電磁誘導加熱装置２０５とを備えている。また、フィルム部材２０１の内周面に接触するようにフィルムガイド部材２０２に固定された第１のサーミスタ２０６と、加圧ロール２０３の表面に接触するように配置された第２のサーミスタ２０７とを備えている。そして、第１のサーミスタ２０６及び第２のサーミスタ２０７によって、フィルム部材２０１及び加圧ロール２０３の温度を測定し、この測定値に基づいて誘導加熱用インバータを制御し、インバータが生成する高周波電流を第１の電磁誘導加熱装置２０４及び第２の電磁誘導加熱装置２０５へ供給し、フィルム部材２０１が目標温度となるように動作させる。
【０００５】
【発明が解決しようとする課題】
しかしながら、上記定着装置で用いられている接触式の温度センサには次のような問題点がある。
上記フィルム部材２０１は、無張架の状態で支持されているため、静止時と周回駆動時とで該フィルム部材２０１の周面の形状が変化する。このため、フィルム部材２０１の静止時に該フィルム部材２０１の内周面に第１のサーミスタ２０６を接触させても、周回駆動にともなって該フィルム部材２０１の周面の形状が変化すると、フィルム部材２０１と第１のサーミスタ２０６とが離間してしまう。そして、フィルム部材２０１の温度を正確に測定するのが困難となってしまう。また、加圧ロール２０３の周回駆動にともなって、第２のサーミスタ２０７が加圧ロール２０３の表面に摺擦され、加圧ロール２０３を傷付けてしまうおそれがある。
【０００６】
一方、被測定体に非接触の状態で温度を測定する、赤外線等を利用した温度センサを用いることによって、周回中のフィルム部材の温度を正確に測定したり、被測定体の表面を傷付けることなく温度を測定できる。しかし、このような非接触式の温度センサはコストが非常に高い。
【０００７】
本願発明は、上記のような事情に鑑みてなされたものであり、その目的は、接触式の温度検出装置によって定着部材又はトナー像が一旦転写される中間転写体の温度を正確に測定し、適切な定着温度を維持することである。
【０００８】
【課題を解決するための手段】
上記の課題を解決するために、請求項１に係る発明は、像担持体上に形成された帯電電位の差による潜像にトナーを選択的に転移してトナー像を形成する画像形成部と、形成された前記トナー像を記録媒体上に転写する転写部と、前記トナー像を担持した記録媒体に押圧される定着部材と、前記定着部材を所定温度に加熱する加熱装置と、前記定着部材の温度を検出する温度検出装置と、を有し、前記温度検出装置は、前記定着部材に接触して該定着部材の温度を検出する温度センサと、板バネからなり、一端が固定支持され、他端付近に前記温度センサが取りつけられた弾性支持部と、前記弾性支持部の前記温度センサが取りつけられた端部付近の、該温度センサが取りつけられた面と反対側に、所定の角度を付けて連続する屈曲部と、前記弾性支持部が湾曲した状態となるように、前記屈曲部をその軸線方向と直角方向には拘束し、軸線方向には移動可能に保持する拘束部とを有し、前記温度センサが前記弾性支持部の弾性反発力によって前記定着部材に圧接されていることを特徴とする画像形成装置を提供する。
【０００９】
上記画像形成装置では、温度検出装置の弾性支持部が湾曲した状態に拘束され、小さな接触圧で定着部材に当接されている。これにより、接触圧は小さく維持されるが、定着部材の変位に対して弾性支持部の反発力で追従することができ、温度センサが定着部材に接触した状態が保たれる。このため、温度センサが定着部材の温度を正確に測定することができ、この定着部材をトナー像を担持した記録媒体に押圧し、適切な温度でトナー像を記録媒体に溶融・圧着することができる。
【００１０】
上記画像形成装置が備える温度検出装置は、屈曲部がその軸線と直角方向に拘束されることにより、温度センサに被測定体である定着部材の接触圧が作用しない状態でも、図７に仮想線で示すように、弾性支持部１０１が湾曲した状態となっている。そして、温度センサ１０２に被測定体との接触圧Ａが作用すると、弾性支持部１０１の非拘束の端部１０１ａが屈曲部１０３の軸線方向に弾性的に後退する（図７に実線で示す状態）。したがって、所定の接触圧で温度センサ１０２と被測定体とが圧接されていると、被測定体が進退移動した場合に弾性支持部１０１の弾性変形によって温度センサ１０２が進退移動に追従し、常に接触状態が維持され、安定して正確な温度検知が行なわれる。
【００１１】
また、屈曲部１０３が拘束されていることにより、弾性支持部１０１を所定の曲率で湾曲させたときの、温度センサ１０２と被測定体との接触圧が小さくなる。つまり、図８に示すように、直線状の板バネからなる弾性支持部１１１を、温度センサ１１２と被測定体との接触圧Ｂによって同じ曲率に湾曲させたときと比べると、屈曲部１０３の拘束によって接触圧Ａが小さくなる。これにより、温度センサ１０２が被測定体に強く押し付けられて、移動する被測定体との摺動を阻害したり、被測定体に過度の変形が生じるのを防止することができる。
なお、図８中に符号Ｃで示すように、弾性支持部１１１を形成する板バネにあらかじめ曲げ加工を施しておくことによって、被測定体と温度センサとの接触圧を低減することもできる。しかし、薄い板バネを所定の曲率となるように塑性変形を生じさせることは難しく、製品化したときの形状にばらつきが生じ易い。このため、図８中の符号Ｃで示す形状に板バネを曲げ加工して用いる構造は、多数生産を行なう製品には採用することができない。
【００１２】
請求項２に係る発明は、請求項１に記載の画像形成装置において、前記定着部材は、周方向に周回駆動される無端状ベルトであり、該無端状ベルトの周回方向における上流側に前記弾性支持部の固定された端部があり、該弾性支持部の屈曲部が設けられた部分が下流側となるように配置され、前記温度センサが、前記無端状ベルトの周面に当接されているものとする。
【００１３】
この画像形成装置では、周回駆動される無端状ベルトの上流側から弾性支持部が徐々に接近し、後退可能な端部に取り付けられた温度センサが接触する。したがって、温度センサと無端状ベルトとの間に多少の摩擦があっても、無端状ベルトは温度センサに対して円滑に摺動し、周回移動する。また、温度センサと無端状ベルトとの間の接触圧は小さくなっており、柔軟なベルトに生じる変形を小さく抑えることができる。特に、無端状ベルトが無張力状態又は張力が小さい状態では、ベルトは変形し易くなるが、接触圧が小さくなるので過度の変形が生じるのを防止することができる。
【００１４】
請求項３に係る発明は、請求項２に記載の画像形成装置において、前記温度センサは、前記無端状ベルトの内周面に当接されており、前記弾性支持部が湾曲する曲率は、前記温度センサが当接される位置付近における前記無端状ベルトの曲率より大きくなっているものとする。
【００１５】
上記画像形成装置が備える温度検出装置は、弾性支持部の曲率が無端状ベルトの曲率より大きいため、無端状ベルトの内側の限られた空間内で、該無端状ベルトの内周面に密着するように圧接される。そして、周回移動する無端状ベルトが揺れても、温度センサは該弾性支持部の弾性反発力によって追従する。このため、温度センサは無端状ベルトの周回駆動時に、該無端状ベルトに接触した状態で維持され、無端状ベルトの温度を安定して正確に測定することができる。
【００１６】
請求項４に係る発明は、請求項２又は請求項３に記載の画像形成装置において、前記無端状のベルトは、無張力状態で支持されているものとする。
【００１７】
上記無端状のベルトは無張架であるため周回駆動中に該ベルトの周面の形状が変化し易くなっているが、上記温度センサはこのベルトの周面の変位に追従して、該ベルトの周面に接触したまま屈曲部の軸線方向に移動する。このため、ベルトが周回駆動中に形状変化を生じても、温度センサを接触させ、正確に温度を測定することができる。また、屈曲部によって弾性支持部の弾性反発力が抑制されているため、温度センサがベルトに強く圧接されて、該ベルトに突出した膨らみが生じるのを防ぐことができる。
【００１８】
請求項５に係る発明は、像担持体上に形成された帯電電位の差による潜像にトナーを選択的に転移してトナー像を形成する画像形成部と、形成された前記トナー像が一旦転写される中間転写体と、前記中間転写体を所定温度に加熱する加熱装置と、前記中間転写体の温度を検出する温度検出装置と、前記トナー像を記録媒体に転写すると同時に定着する転写定着部と、を有し、前記温度検出装置は、前記中間転写体に接触して該中間転写体の温度を検出する温度センサと、板バネからなり、一端が固定支持され、他端付近に前記温度センサが取りつけられた弾性支持部と、前記弾性支持部の前記温度センサが取りつけられた端部付近の、該温度センサが取りつけられた面と反対側に、所定の角度を付けて連続する屈曲部と、前記弾性支持部が湾曲した状態となるように、前記屈曲部をその軸線方向と直角方向には拘束し、軸線方向には移動可能に保持する拘束部とを有し、前記温度センサが前記弾性支持部の弾性反発力によって前記定着部材に圧接されていることを特徴とする画像形成装置を提供する。
【００１９】
上記画像形成装置では、中間転写体が進行方向と直角の方向に変位するような場合に、温度センサが中間転写体に良好に接触している状態が維持され、中間転写体の温度を正確に測定することができる。したがって、該中間転写体を加熱装置によって適切に加熱することができる。そして、この中間転写体上でトナー像を加熱して、記録媒体に転写と定着とを同時に行い、特にカラー画像を形成する場合には、色ずれの少ない画像を得ることができる。
【００２０】
請求項６に係る発明は、請求項１又は請求項５に記載の画像形成装置において、前記屈曲部は、前記弾性支持部と前記屈曲部とのなす角度が９０°以上で１８０°以下となるように、前記弾性支持部と連続する板バネを折り曲げて形成されているものとする。
【００２１】
上記弾性支持部と屈曲部とは、９０°〜１８０°で連続しており、温度センサに被測定体との接触圧が作用したときに、屈曲部は大きな変形を生じることなくその軸線方向に移動し、温度センサが無端状ベルトの進退に追従する。また、屈曲部は弾性支持部と連続する板バネで形成されており、弾性支持部と屈曲部とを小さい工数で容易に製作することができる。
【００２２】
請求項７に係る発明は、請求項１又は請求項５に記載の画像形成装置において、前記屈曲部は、該屈曲部の軸線方向に変位して前記拘束部における拘束から脱落するのを抑止する係止部を有するものとする。
【００２３】
上記画像形成装置では、弾性支持部の弾性反発力によって屈曲部が拘束部における拘束から脱落する方向に移動するのを防ぐことができる。つまり、温度センサに接触圧が作用しないときには、屈曲部をその軸線に沿って弾性支持部との接合されている方向へ引き出す力が作用するが、係止部によって拘束部から抜け出すのが抑えられ、弾性支持部の湾曲した形態が維持される。
【００２４】
【発明の実施の形態】
以下、本願に係る発明の実施の形態を図に基づいて説明する。
図１は、請求項１に係る発明の一実施形態である画像形成装置の概略構成図である。
図１に示す画像形成装置は、一様帯電後に像光を照射することにより表面に静電電位の差による潜像が形成される円筒状の感光体ドラム１を備えており、この感光体ドラム１の周囲に、感光体ドラム１の表面を一様に帯電させる帯電装置２と、感光体ドラム１に像光を照射して表面に潜像を形成する露光装置３と、感光体ドラム上の潜像にトナーを選択的に転移させてトナー像を形成する現像ユニット４と、感光体ドラム１と対向し、周面が周回可能に支持される無端ベルト状の中間転写体５と、トナー像の転写後に感光体ドラム１に残留するトナーを除去するクリーニング装置６と、感光体ドラム１の表面を除電する除電露光装置７とを備えている。
【００２５】
また、上記中間転写体５の内側には、感光体ドラム上に形成されたトナー像を中間転写体５に一次転写させる転写帯電器８と、２つの支持ロール９ａ、９ｂと、二次転写を行うための転写対向ロール１０とが配置されており、これらによって中間転写体５が周回可能に張架されている。該転写対向ロール１０と中間転写体５を介して対向する位置には、中間転写体上のトナー像を記録紙に転写する転写ロール１１が配設されており、該転写対向ロール１０と転写ロール１１との圧接部に、用紙トレイ（図示しない）から記録紙が送り込まれる。圧接部の下流側には、記録紙上のトナー像を加熱溶融して記録紙に圧着する定着装置１２と、中間転写体５に沿って、中間転写体上に残留するトナーを除去するクリーニング装置１３とが設けられている。
【００２６】
上記感光体ドラム１は、ドラム表面にSe、a-Si、a-SiC、Cds等の各種無機感光材料、有機感光材料、アモルファスセレン系感光材料、アモルファスシリコン系感光材料等からなる感光体層を有するものを用いることができる。
【００２７】
上記帯電装置２は、ステンレススチール、アルミニウム等の導電性を有する金属のロールに高抵抗材料のコーティングを施したものであり、感光体ドラム１に当接され、従動回転するようになっている。そして、所定の電圧が印加されることにより、該ロールと感光体ドラム１との接触部近傍における微小間隙内で継続的な放電を生じ、感光体ドラム１の表面をほぼ一様に帯電するものである。
【００２８】
上記露光装置３は、画像信号に基づいて点滅するレーザー光を発生し、これをポリゴンミラーによって感光体ドラム１の主走査方向にスキャンするものである。これにより感光体ドラム１の表面に静電潜像が形成される。
【００２９】
上記現像ユニット４は、イエロー、マゼンタ、シアン、ブラックのトナーを収容した４台の現像器が回転可能に支持されており、順次各現像器が感光体ドラム１と近接・対向して、各色に対応した潜像に、トナーを転移して可視像を形成するものである。
【００３０】
ベルト状の上記中間転写体５は、ベース層と表面層との２層構造となっており、ベース層には、耐熱性、強度、表面平滑性を考慮してポリイミド、ポリアミド、ポリアミドイミド等の耐熱性樹脂や、アルミニウム、ステンレス等の金属を用い、表面層には、耐熱性およびトナーとの離型性の高いシリコーンゴム、フッ素ゴム等を用いている。
【００３１】
上記転写帯電器８は、感光体ドラム１上のトナー像が、効率良く中間転写体５へ転移するように、電圧を印加することによって中間転写体５の裏面に電荷を付与するものである。
【００３２】
上記転写ロール１１は、導電性もしくは半導電性のロール状部材からなり、転写対向ロール１０との間に電圧を印加することによって、中間転写体上のトナー像を記録紙に一括転写する。
【００３３】
次に、上記定着装置１２が有する構成の詳細について、図２に基づいて説明する。
この定着装置１２は、無端ベルト状の加熱回転体２１と、該加熱回転体２１の周面と対向する位置に支持された電磁誘導加熱装置２２と、加熱回転体２１に圧接される加圧ロール２３と、加熱回転体２１の内周面に支持され、加圧ロール２３との間に加熱回転体２１を挟み込む加圧部材２４と、加圧ロール２３と加圧部材２４との圧接部の下流側近傍に支持された剥離部材２５とを有している。また、加圧ロール２３と加圧部材２４との圧接部の上流側近傍に加熱回転体２１の内周面の温度を測定する温度検出装置２６が設けられ、加熱回転体２１の外周面付近には周回速度センサ２７が設けられている。
【００３４】
上記加熱回転体２１は、ベルト状の導電性層２１ａを基層として、その上に弾性層２１ｂと、表面離型層２１ｂとが積層されている。導電性層２１ａは、例えば鉄、磁性ステンレス、ニッケルなどの磁性金属、またはこれら主体の合金や非磁性ステンレス、アルミニウム、銅などの非磁性金属、またはこれら主体の合金を、厚さ５μｍ〜５０μｍで形成したものが用いられ、電磁誘導で十分な発熱が得られるような固有抵抗値となるように材質が選択される。弾性層２１ｂは、記録紙上のトナー像に加熱回転体２１の表面を密着させるものであり、耐熱性を有し、熱伝導率の高いシリコーンゴム、フッ素ゴム、フルオロシリコンゴム等が用いられ、厚さ１０μｍ〜５００μｍ、硬度６００（ＪＩＳ−ＫＡ型試験機）以下とするのが望ましい。表面離型層２１ｃは、厚さ１μｍ〜１００μｍの、フッ素樹脂、シリコーン樹脂、フルオロシリコンゴム、フッ素ゴム、シリコーンゴム、ＰＦＡ（テトラフルオロエチレン−パーフルオロアルコキシビニルエーテル共重合体）、ＰＴＦＥ（ポリテトラフルオロエチレン）、ＦＥＰ（テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体）等の離型性及び耐熱性の高いものを用いることができる。また、加熱回転体２１の最表層である表面離型層２１ｃには、周回速度センサ２７によって加熱回転体の周回速度を検知するため、該周回速度センサ２７から照射された光を反射する単数又は複数の反射体が設けられている。
なお、この加熱回転体２１は、ポリイミド、ポリイミドアミド等に代表される耐熱性の高いシート状部材を基層とし、その上に導電性層、さらにその上に弾性層、表面離型層を積層したものでもよい。
【００３５】
上記加圧ロール２３は、金属製の円筒状芯金２３ａを芯材とし、該芯金２３ａの表面にスポンジやゴムなどの弾性層２３ｂを備えている。この加圧ロール２３は、駆動モータ（図示しない）によって回転駆動され、これにともなって加熱回転体２１が従動回転する。
【００３６】
上記電磁誘導加熱装置２２は、加熱回転体２１の外周面に沿って、この外周面とのギャップが１〜３ｍｍとなるよう配置されており、加熱回転体２１の導電性層を発熱させるものである。この電磁誘導加熱装置２２は、台座２２ａに支持されたフェライト等からなる磁性体コア２２ｂと、この磁性体コア２２ｂの周囲に巻き回された励磁コイル２２ｃと、この励磁コイル２２ｃに交流電流を供給する励磁回路２２ｄとで主要部が構成されている。台座２２ａは、非磁性で耐熱性を有するものであり、ポリカーボネイト、ＰＰＳ（ポリフェニレンサルファイド）等の耐熱性樹脂、耐熱ガラス又は液晶ポリマー等が用いられる。磁性体コア２２ｂは、単一のコアブロック、あるいは複数のコアブロックを連続で配設する。
【００３７】
上記加圧部材２４は、加圧ロール２３の周面に沿った形に湾曲した弾性部材２４ｂと、該弾性部材２４ｂよりもプロセス下流側に突出部を有する圧力付与部材２４ｃと、加熱回転体２１の幅方向における両端部には、内周面に沿って配置されているベルト走行ガイド（図示しない）とが、金属製あるいは耐熱性樹脂等のホルダー２４ａによって支持されている。
【００３８】
上記金属製のホルダー２４ａの、電磁誘導加熱装置２２と対向する部分には、加熱回転体２１の導電性層２１ａを通過した磁束を集める磁性体２４ｆと、該磁性体２４ｆ上に、加熱回転体の内周面に沿って該加熱回転体のガイドをするガイドパッド２４ｇとが設けられている。磁性体２４ｆは、鉄、コバルト、ニッケル、フェライト等の磁性材料からなり、ガイドパッド２４ｇは、加熱回転体２１からの熱移動が生じにくい熱伝導率の低い材料を用いる。
【００３９】
上記弾性部材２４ｂは、加圧ロール２３に圧接されており、加圧ロール２３の周面に倣って凹型であるため、加熱回転体２１を介して加圧ロール２３との間に十分な圧接幅を得ることができる。また、弾性部材２４ｂの表面には低摩擦層２４ｅが設けられており、加熱回転体２１の内周面との摩擦を低減できる。
【００４０】
上記圧力付与部材２４ｃは、加圧ロール２３が有する弾性体層２３ｂより硬質の材料からなり、該圧力付与部材２４ｃと加圧ロール２３との圧接部では、該加圧ロール２３の弾性体層２３ｂにひずみが生じる。ひずみが生じた部分では、加熱回転体２１と加圧ロール２３との間に挟み込まれた記録紙Ｐの移動速度と、加熱回転体２１の周回速度とに差が生じ、記録紙Ｐと加熱回転体２１との付着力が低下し、記録紙Ｐが剥離され易くなる。
【００４１】
なお、上記ベルト走行ガイドは、加熱回転体２１の内周面と摺擦するため摩擦係数が低く、なおかつ、加熱回転体２１からの熱移動量を低減するために熱伝導率の低い材料からなるものが望ましい。
【００４２】
上記剥離部材２５は、一端が固定支持された支持部材２５ａと、これに支持されている剥離シート２５ｂとからなり、剥離シート２５ｂの先端が加熱回転体２１に近接又は接触するように配置されている。これにより、圧接部を通過した記録紙Ｐと加熱回転体２１との間に剥離シート２５ｂが入り込み、記録紙Ｐを加熱回転体２１から剥離する。
【００４３】
上記温度検出装置２６は、加熱回転体２１に接触して該加熱回転体２１の温度を検出する温度センサ３１と、温度センサ３１を支持し、該温度センサ３１を加熱回転体２１の内周面に圧接する支持部材３２と、支持部材３２の一部が湾曲した状態となるように該支持部材３２を拘束する拘束部材３３とで構成されている。そして、温度センサ３１の検出値によって、励磁回路２２ｄから励磁コイル２２ｃへの電力供給量が制御され、加熱回転体２１の表面温度が所望の温度を維持するようになっている。
【００４４】
上記温度センサ３１は、被測定体に接触した状態で温度を測定するものであり、ゼーベック効果を利用した熱電対や、抵抗の温度係数が大きい素子を用いたサーミスタ等が用いられる。これらの接触式の温度センサは安価であるため、装置のコストを低減できる。
【００４５】
上記支持部材３２は、加熱回転体２１の曲率より大きい曲率で弾性的に湾曲した状態となるように支持された弾性支持部３２ａと、該弾性支持部３２ａと連続し、約９０°に折り曲げられた屈曲部３２ｂと、該屈曲部３２ｂの先端を折り曲げた係止部３２ｃとを有している。上記弾性支持部３２ａの一端は拘束部材３３に固定され、他端に取り付けられた温度センサ３１が湾曲した弾性支持部３２ａの弾性反発力で加熱回転体２１の内周面に押圧されている。この支持部材３２は、１枚の板バネを折り曲げて弾性支持部３２ａと、屈曲部３２ｂと、係止部３２ｃとを形成したものであってもよいし、弾性支持部３２ａとなる板バネに他の部材を接合して屈曲部３２ｂ及び係止部３２ｃを形成してもよい。板バネは、バネ定数ｋが０．０１Ｎ／ｍｍ以上、１Ｎ／ｍｍ以下であり、厚みが０．０５ｍｍ以上、１．０ｍｍ以下、幅が０．５ｍｍ以上、２ｍｍ以下であるものが望ましい。
【００４６】
上記拘束部材３３は、ＰＰＳ（ポリフェニレンサルファイド）等の耐熱性樹脂からなる板状部材又はブロック状部材であって、加圧部材２４に固定され、ガイド３３ａとなる孔又はスリットが設けられている。ガイド３３ａには支持部材３２の屈曲部３２ｂが挿通され、屈曲部をその軸線方向と直角方向に拘束し、軸線方向には移動可能となるように案内するものとなっている。
【００４７】
上記屈曲部３２ｂの拘束により、弾性支持部３２ａには湾曲するような変形が生じ、湾曲面の外側に取り付けられた温度センサ３１が加熱回転体２１に圧接されるときの接触圧を小さくすることができる。そして、屈曲部３２ｂが軸線方向に移動可能となっていることにより、温度センサ３１は弾性支持部３２ａの弾性反発力で進退可能となり、加熱回転体２１の変位に対して追従するものとなっている。また、弾性支持部３２ａの反発力によって屈曲部３２ｂがガイド３３ａから脱落する方向に移動したときには、係止部３２ｃが拘束部材３３に係止され、屈曲部３２ｂのガイド３３ａからの脱落を抑止するものとなっている。
【００４８】
上記周回速度センサ２７は、加熱回転体２１の周面に向けて光照射を行い、該加熱回転体２１の周面に設けられた反射体による反射光を検知する。そして、加熱回転体の周長、あるいは反射体が複数設けられている場合は該反射体間の距離と、最初の反射光を検知してから次の反射光を検知するまでの時間とから、加熱回転体２１の周回速度を検出するものである。
【００４９】
なお、上記画像形成装置で用いられるトナーは、イエロー、マゼンタ、シアン又はブラックの色素を含有した熱可塑性のバインダで構成され、公知の材料によって形成することができる。
【００５０】
次に、上記画像形成装置及び定着装置１２の動作について説明する。
まず、感光体ドラム１の表面が帯電装置２でほぼ一様に帯電され、次いで露光装置３から像光が照射されて感光体ドラム１の表面に静電電位の差による潜像が形成される。そして、感光体ドラム１の回転により現像ユニット４の１つの現像器４ａと対向する位置に移動し、現像器４ａから１色目のトナーが転移され、トナー像が形成される。このトナー像は感光体ドラム１の周回移動により中間転写体５との対向位置に搬送され、中間転写体上に静電的に一次転写される。
【００５１】
一方、一次転写後に感光体ドラム１上に残留するトナーはクリーニング装置７により除去され、感光体ドラム１の表面は除電露光装置８により電位的に初期化され、再び帯電装置２との対向位置に移動する。
以後、現像ユニット４の３つの現像器４ｂ、４ｃ、４ｄが順次感光体ドラム１と対向する位置に移動し、同様に２色目、３色目、４色目のトナー像が順次形成され、中間転写体５上に重ねて転写される。
【００５２】
中間転写体上に重ね合わされたトナー像Ｔは、中間転写体５の周回移動により、転写ロール１１と転写対向ロール１０との対向位置に搬送され、用紙トレイから送り込まれた記録紙Ｐに当接される。転写ロール１１と中間転写体５との間には転写用バイアス電圧が印加されており、トナー像Ｔは記録紙上に二次転写される。
【００５３】
未定着のトナー像Ｔを担持した記録紙Ｐは定着装置１２へ搬送され、定着装置１２の有する加熱回転体２１と加圧ロール２３との間に送り込まれる。そして、記録紙Ｐは、電磁誘導加熱装置２２によって所定の温度に加熱された加熱回転体２１と、加圧ロール２３とによって加熱押圧され、トナー像Ｔは記録紙Ｐに溶融圧着される。記録紙Ｐは、加圧ロール２３の弾性層２３ｂが圧力付与部材２４ｃによって変形している部分で、加熱回転体２１から剥離され易い状態となり、さらに、剥離部材２５によって加熱回転体２１から剥離される。
【００５４】
上記定着装置１２では、加圧ロール２３が駆動を開始し、加熱回転体２１が従動して周回を開始するのとほぼ同時、あるいは開始直後に、電磁誘導加熱装置２２が有する励磁回路２２ｄから励磁コイル２２ｃに交流電流が供給される。励磁コイル２２ｃに交流電流が供給されると、励磁コイル２２ｃの周囲に矢印Ｈで示される磁束が生成消滅を繰り返す。そして、この磁束Ｈが加熱回転体２１が有する導電性層２１ａを横切るとき、その磁界の変化を妨げる磁界を生じるように、導電性層２１ａには渦電流が発生し、該導電性層２１ａの表皮抵抗及び導電性層２１ａを流れる電流の大きさに比例して発熱する。一方、導電性層２１ａを貫通した磁束は、加圧部材２４が有する磁性体２４ｆに向かって閉じた経路を形成する。
【００５５】
一方、加熱回転体２１が周回移動すると、該加熱回転体２１は無張力状態で支持されているため周面の形状が変化する。この形状の変化にともなって、温度センサ３１が当接している位置でも、加熱回転体２１はその周面と直角方向に変位する。これに対して温度検出装置３２は、図３に示すように、弾性支持部３２ａが変形し、屈曲部３２ｂが拘束部材３３に対して摺動することにより、温度センサ３１が加熱回転体２１の進退に追従して常に接触した状態が維持される。これにより、温度センサ３１は加熱回転体２１の温度を正確に検出する。そして、この検出値に基づいて励磁回路２２ｄから励磁コイル２２ｃへ電力供給が制御され、加熱回転体２１の表面が所望の温度に加熱される。
【００５６】
このとき、弾性支持部３２ａは、屈曲部３２ｂが拘束されることによってあらかじめ湾曲しているため、加熱回転体２１と温度センサ３１との接触圧による変位量が少なくなっている。これにより、温度センサ３１と加熱回転体２１の内周面との接触圧は小さく保持されるとともに、加熱回転体２１の変位に適切に追従することが可能となる。したがって、柔軟なベルト状部材である加熱回転体２１を過度に変形させることなく、温度を正確に検出することができる。
【００５７】
上記弾性支持部３２ａに比べて、図４に示すように一端が固定されているだけの弾性支持部３２ａ´では、弾性支持部３２ａ´が加熱回転体２１´との接触圧によって大きく変位し、接触圧も大きくなっている。さらに弾性支持部３２ａ´の移動が案内されていないため、加熱回転体２１の内周面に対して温度センサ３１´を安定した状態で摺動させることが難しい。このため、温度センサ３１´の検出値に誤差が生じることがある。また、温度センサ３１´が加熱回転体２１´に強く押し付けられ、加熱回転体２１´の周面に突出した膨らみが生じてしまったり、加熱回転体の内周面が傷ついてしまうことになる。
【００５８】
図５は、上記定着装置１２で用いることのできる他の温度検出装置を示す概略構成図である。
この温度検出装置は、加熱回転体２１の温度を検出する、熱電対やサーミスタ等の接触式の温度センサ４１と、温度センサ４１を支持し、該温度センサ４１を加熱回転体２１の内周面に圧接する支持部材４２と、支持部材４２の一部が湾曲した状態となるように該支持部材４２を拘束する拘束部材４３とで構成されている。
【００５９】
上記支持部材４２は、上記温度検出装置２６が有する支持部材３２と同様に、弾性支持部４２ａと、屈曲部４２ｂと、係止部４２ｃとを有している。また、拘束部材４３は耐熱性樹脂からなり、ガイド４３ａとなる孔又はスリットが加熱回転体２１の重心を通るように設けられており、ガイド４３ａに屈曲部４２ｂが挿通される。そして、温度センサ４１が加熱回転体２１に当接される位置で、この温度センサ４１を支持する弾性支持部４２ａと加熱回転体２１の接線とがほぼ一致するようになっている。この温度検出装置では、加熱回転体２１の周面の変位による圧接力が屈曲部４２ｂに効率良く伝達され、ガイド４３ａによって屈曲部４２ｂを案内しやすい。このため、温度センサ４１は加熱回転体２１の周面の形状に追従して、該加熱回転体２１の内周面に圧接され、温度を正確に検出することができる。
【００６０】
図６は、請求項５に係る発明の一実施形態である画像形成装置の概略構成図である。
この画像形成装置は、静電電位の差による潜像が形成される円筒状の感光体ドラム５１と、この感光体ドラム５１の周囲に、帯電装置５２と、露光装置５３と、現像ユニット５４と、無端状ベルトの中間転写体５５と、クリーニング装置５６と、除電露光装置５７とを備えている。また、中間転写体５５の内側には、感光体ドラム上に形成されたトナー像を中間転写体５５に一次転写させる転写帯電器５８と、２つの支持ロール５９ａ、５９ｂと、二次転写を行うための転写ロール６０とが配置されており、これらによって中間転写体５５が周回可能に張架されている。さらに、転写ロール６０と中間転写体５５を介して対向する位置には、加圧ロール６１が配設されており、中間転写体５５の内周面に沿って、中間転写体５５及び中間転写体上のトナー像を加熱する電磁誘導加熱装置６２と、該中間転写体の温度を測定する温度検出装置６３と、外周面に沿ってクリーニング装置６４とが設けられている。
なお、感光体ドラム５１、帯電装置５２、露光装置５３、現像ユニット５４、クリーニング装置５６、除電露光装置５７、転写帯電器５８は、図１に示す画像形成装置と同様のものを用いることができる。
【００６１】
上記中間転写体５は、耐熱性の高いシート状部材からなる基層と、その上に積層された導電性層と、最も上層となる表面離型層との３層で構成されており、導電性層は、電磁誘導で十分な発熱が得られるような固有抵抗値となるように材質が選択される。また、表面離型層は、離型性の高いシート又はコート層であることが好ましく、一次転写時のトナー像の静電転写性も考慮して、カーボンブラックなどの導電材料を分散し、抵抗調整を行ったシートを用いてもよい。
【００６２】
上記温度検出装置６３は、図２に示す定着装置が有する温度検出装置２６と同様のものを用いることができ、温度センサは弾性支持部の弾性反発力によって中間転写体５５の内周面に圧接され、温度を検出するものとなっている。
【００６３】
この画像形成装置では、感光体ドラム５１から中間転写体５５上に転写され、複数色が重ね合わされた複数のトナー像Ｔは、中間転写体５の周回移動により、電磁誘導加熱装置６２と対向する加熱領域を通過する。トナー像Ｔは、中間転写体上で加熱されて溶融し、転写ロール６０と加圧ロール６１との圧接部に搬送される。この搬送にタイミングを合わせて、記録紙Ｐが用紙トレイ（図示しない）から中間転写体５５と加圧ロール６１との間に送り込まれ、トナー像Ｔが記録紙Ｐに圧着され、転写と定着とが同時に行なわれる。
【００６４】
このとき、温度検出装置６３の検出値によって電磁誘導加熱装置６２に供給する電力が制御され、中間転写体５５の表面温度が所望の温度を維持するようになっている。この温度検出装置６３では、弾性支持部の弾性反発力が抑制されるため、温度センサが中間転写体５５に強く圧接されて中間転写体５５が過度に変形したり、傷付くのを防ぐことができる。
【００６５】
【発明の効果】
以上説明したように、本願発明に係る画像形成装置では、温度検出装置の弾性支持部が湾曲した状態となるように屈曲部が拘束されているため、弾性支持部に取りつけられた温度センサが被測定体の接触圧によって、該被測定体に接触したまま屈曲部の軸線方向に移動する。そして、弾性支持部の弾性反発力が抑制されるため、温度センサは被測定体に適当な圧接力で接触し、被測定体を傷付けることなく、正確に温度を測定することができる。そして、被測定体である定着部材又は中間転写体の温度を正確に制御してトナー像の良好な定着を行なうことができる。
【図面の簡単な説明】
【図１】請求項１に係る発明の一実施形態である画像形成装置の概略構成図である。
【図２】図１に示す画像形成装置が有する定着装置の概略構成図である。
【図３】図２に示す定着装置が有する温度検出装置の形状の変化を説明する図である。
【図４】図３に示す温度検出装置と比較される温度検出装置の形状の変化を説明する図である。
【図５】図２に示す定着装置で用いることのできる他の温度検出装置を示す概略構成図である。
【図６】請求項５に係る発明の一実施形態である画像形成装置の概略構成図である。
【図７】請求項１に係る発明の温度検出装置の作用を説明する図である。
【図８】図７に示す温度検出装置と比較される温度検出装置の作用を説明する図である。
【図９】従来の温度センサを有する定着装置を示す概略構成図である。
【符号の説明】
１、５１感光体ドラム
２、５２帯電装置
３、５３露光装置
４、５４現像ユニット
５、５５中間転写体
６、５６クリーニング装置
７、５７除電露光装置
８、５８転写帯電器
９、５９支持ロール
１０転写対向ロール
１１、６０転写ロール
１２定着装置
１３、６４クリーニング装置
２１加熱回転体
２２、６２電磁誘導加熱装置
２３、６１加圧ロール
２４加圧パッド
２５剥離部材
２６、６３温度検出装置
２７周回速度センサ
３１、４１温度センサ
３２、４２支持部材
３３、４３拘束部材[0001]
BACKGROUND OF THE INVENTION
  The present inventionThe present invention relates to an image forming apparatus provided with a temperature detection device that detects a temperature in contact with a fixing member or an intermediate transfer member..
[0002]
[Prior art]
  In general, in a process of fixing a toner image in an image forming apparatus using powdered toner, a toner image is electrostatically transferred onto a recording medium, and then the recording medium is sandwiched between a heating member and a pressure member. A method in which a toner image is heated and pressed onto a recording medium is widely used. Also known is an image forming apparatus that primarily transfers a toner image to an intermediate transfer member, then heats the toner image on the intermediate transfer member, and presses the toner image onto a recording medium to simultaneously perform secondary transfer and fixing. It has been.
[0003]
  As means for heating the heating member or the intermediate transfer member, Japanese Patent Application Laid-Open No. 10-254263, Japanese Patent Application Laid-Open No. 10-301415, Japanese Patent Application Laid-Open No. 11-352804, etc. include a conductive layer on the heating member or the intermediate transfer member. And heating the conductive layer by electromagnetic induction heating is described. In electromagnetic induction heating, an exciting coil that generates a variable magnetic field is disposed so as to face a conductive layer, and a magnetic flux penetrating the conductive layer is generated to generate eddy current in the conductive layer and generate heat. . According to electromagnetic induction heating, the heating member or the intermediate transfer member can be directly heated, and the conductive layer can generate heat in a very short time. For this reason, warming up can be performed efficiently when the apparatus is activated or when returning from the standby state, and power consumption can be reduced.
[0004]
  On the other hand, in order to heat the toner image at an appropriate temperature and perform good fixing, it is necessary to measure the temperature of the heating member or the intermediate transfer member and maintain it at a predetermined temperature. As a means for measuring temperature, generally, a temperature sensor such as a thermistor or a thermocouple that measures the temperature by contacting the object to be measured is used.
  As shown in FIG. 9, a fixing device described in Japanese Patent Laid-Open No. 9-292790 includes a film member 201 supported in a non-tensioned state, and a film disposed close to the inner peripheral surface of the film member 201. The guide member 202, the pressure roll 203 pressed against the film member 201, the first electromagnetic induction heating device 204 and the second electromagnetic heating device 204 disposed inside each of the film member 201 and the pressure roll 203 and heating them. And an electromagnetic induction heating device 205. In addition, a first thermistor 206 fixed to the film guide member 202 so as to contact the inner peripheral surface of the film member 201 and a second thermistor 207 arranged so as to contact the surface of the pressure roll 203 are provided. I have. Then, the temperature of the film member 201 and the pressure roll 203 is measured by the first thermistor 206 and the second thermistor 207, the induction heating inverter is controlled based on the measured value, and the high frequency current generated by the inverter is generated. It supplies to the 1st electromagnetic induction heating apparatus 204 and the 2nd electromagnetic induction heating apparatus 205, and it is operated so that the film member 201 may become target temperature.
[0005]
[Problems to be solved by the invention]
  However, the contact-type temperature sensor used in the fixing device has the following problems.
  Since the film member 201 is supported in a non-tensioned state, the shape of the peripheral surface of the film member 201 changes between the stationary state and the circular driving state. For this reason, even if the first thermistor 206 is brought into contact with the inner peripheral surface of the film member 201 when the film member 201 is stationary, the shape of the peripheral surface of the film member 201 changes as the film member 201 is driven. And the first thermistor 206 are separated from each other. And it becomes difficult to measure the temperature of the film member 201 correctly. Further, as the pressurizing roll 203 is driven around, the second thermistor 207 may be rubbed against the surface of the pressurizing roll 203 to damage the pressurizing roll 203.
[0006]
  On the other hand, by using a temperature sensor that uses infrared rays or the like to measure the temperature in a non-contact state with the object to be measured, the temperature of the film member during circulation can be accurately measured or the surface of the object to be measured can be damaged. Temperature can be measured. However, such a non-contact type temperature sensor is very expensive.
[0007]
  The present invention has been made in view of the above circumstances, and its purpose is to use a contact-type temperature detection device.Intermediate transfer member onto which a fixing member or toner image is once transferredIs to accurately measure the temperature of the toner and maintain an appropriate fixing temperature.
[0008]
[Means for Solving the Problems]
  In order to solve the above-described problems, an invention according to claim 1 includes an image forming unit that selectively transfers toner to a latent image due to a difference in charging potential formed on an image carrier to form a toner image. A transfer unit that transfers the formed toner image onto a recording medium, a fixing member that is pressed against the recording medium that carries the toner image, a heating device that heats the fixing member to a predetermined temperature, and the fixing member A temperature detection device that detects the temperature of the temperature detection device, the temperature detection device comprising a temperature sensor that contacts the fixing member and detects the temperature of the fixing member, and a leaf spring, one end of which is fixedly supported, A predetermined angle is formed between the elastic support portion to which the temperature sensor is attached in the vicinity of the other end and the surface of the elastic support portion in the vicinity of the end portion to which the temperature sensor is attached opposite to the surface on which the temperature sensor is attached. Followed by A curved portion, and a restraining portion that restrains the bent portion in a direction perpendicular to the axial direction and movably holds in the axial direction so that the elastic support portion is in a curved state. An image forming apparatus is provided, wherein a sensor is pressed against the fixing member by an elastic repulsive force of the elastic support portion.
[0009]
  In the image forming apparatus, the elastic support portion of the temperature detection device is restrained in a curved state and is in contact with the fixing member with a small contact pressure. Thereby, although the contact pressure is kept small, the displacement of the fixing member can follow the repulsive force of the elastic support portion, and the temperature sensor is kept in contact with the fixing member. For this reason, the temperature sensor can accurately measure the temperature of the fixing member, and the fixing member can be pressed against the recording medium carrying the toner image, and the toner image can be melted and pressed onto the recording medium at an appropriate temperature. it can.
[0010]
  The temperature detection device provided in the image forming apparatus is:The bent part is constrained in the direction perpendicular to its axis, whichFixing member that is the object to be measuredEven in a state where the contact pressure does not act, the elastic support portion 101 is in a curved state as indicated by a virtual line in FIG. When the contact pressure A with the measured object acts on the temperature sensor 102, the unconstrained end portion 101a of the elastic support portion 101 is elastically retracted in the axial direction of the bent portion 103 (a state indicated by a solid line in FIG. 7). ). Therefore, when the temperature sensor 102 and the measured object are pressed against each other with a predetermined contact pressure, the temperature sensor 102 follows the forward / backward movement due to elastic deformation of the elastic support portion 101 when the measured object moves forward / backward, and always The contact state is maintained, and stable and accurate temperature detection is performed.
[0011]
  Further, since the bent portion 103 is constrained, the contact pressure between the temperature sensor 102 and the measured object when the elastic support portion 101 is bent with a predetermined curvature is reduced. That is, as shown in FIG. 8, when the elastic support portion 111 made of a linear leaf spring is bent to the same curvature by the contact pressure B between the temperature sensor 112 and the measured object, The contact pressure A is reduced by the restraint. As a result, it is possible to prevent the temperature sensor 102 from being strongly pressed against the object to be measured and hindering sliding with the moving object to be measured, or preventing excessive deformation of the object to be measured.
  In addition, as shown by the code | symbol C in FIG. 8, the contact pressure of a to-be-measured body and a temperature sensor can also be reduced by giving beforehand the bending process to the leaf | plate spring which forms the elastic support part 111. FIG. However, it is difficult to cause plastic deformation so that a thin leaf spring has a predetermined curvature, and the shape when manufactured is likely to vary. For this reason, the structure in which the leaf spring is bent into the shape indicated by the symbol C in FIG. 8 cannot be used for products that are produced in large numbers.
[0012]
  The invention according to claim 2 is described in claim 1.Image forming apparatusInThe fixing member isAn endless belt that is driven to circulate in a circumferential direction, and an end portion of the elastic support portion that is fixed on the upstream side in the circumferential direction of the endless belt and a bent portion of the elastic support portion is provided. It is arranged to be on the downstream side, and the temperature sensor is in contact with the peripheral surface of the endless belt.
[0013]
  thisImage forming apparatusThen, the elastic support part gradually approaches from the upstream side of the endless belt that is driven to circulate, and a temperature sensor attached to the retractable end part comes into contact. Therefore, even if there is some friction between the temperature sensor and the endless belt, the endless belt slides smoothly with respect to the temperature sensor and moves around. In addition, the contact pressure between the temperature sensor and the endless belt is small, and deformation that occurs in the flexible belt can be suppressed to a low level. In particular, when the endless belt is in a non-tensioned state or in a state where the tension is low, the belt is easily deformed, but since the contact pressure is small, excessive deformation can be prevented.
[0014]
  The invention according to claim 3 is described in claim 2.Image forming apparatusThe temperature sensor is in contact with the inner peripheral surface of the endless belt, and the curvature of the elastic support portion is more than the curvature of the endless belt in the vicinity of the position where the temperature sensor is in contact. Assume that it is getting bigger.
[0015]
  the aboveThe temperature detection device provided in the image forming apparatus isSince the curvature of the elastic support portion is larger than the curvature of the endless belt, the elastic support portion is pressed into close contact with the inner peripheral surface of the endless belt in a limited space inside the endless belt. And even if the endless belt moving in a circle is shaken, the temperature sensor follows the elastic repulsive force of the elastic support portion. For this reason, the temperature sensor is maintained in contact with the endless belt when the endless belt is driven to circulate, and the temperature of the endless belt can be measured stably and accurately.
[0016]
  The invention according to claim 4 is the image forming apparatus according to claim 2 or claim 3.The endless belt is supported in a tensionless state.
[0017]
  Since the endless belt is a non-tensioned belt, the shape of the circumferential surface of the belt is likely to change during circular driving, but the temperature sensor follows the displacement of the circumferential surface of the belt, and the belt It moves in the axial direction of the bent portion while being in contact with the peripheral surface. For this reason, even if the belt undergoes a shape change while being driven, the temperature sensor can be brought into contact and the temperature can be accurately measured. Further, since the elastic repulsion force of the elastic support portion is suppressed by the bent portion, it is possible to prevent the temperature sensor from being strongly pressed against the belt and causing a bulge protruding from the belt.
[0018]
  Claim 5According to the invention, an image forming unit that selectively transfers toner to a latent image due to a difference in charging potential formed on an image carrier to form a toner image, and an intermediate in which the formed toner image is once transferred A transfer member, a heating device that heats the intermediate transfer member to a predetermined temperature, a temperature detection device that detects the temperature of the intermediate transfer member, and a transfer fixing unit that simultaneously transfers and fixes the toner image to a recording medium. The temperature detection device comprises a temperature sensor that detects the temperature of the intermediate transfer body by contacting the intermediate transfer body, and a leaf spring, one end of which is fixedly supported, and the temperature sensor is mounted near the other end. An elastic support portion, and a bent portion that is continuous at a predetermined angle on the opposite side of the surface of the elastic support portion to which the temperature sensor is attached, on the side opposite to the surface to which the temperature sensor is attached, Elastic support The bending portion is constrained in a direction perpendicular to the axial direction thereof and is held movably in the axial direction so that the temperature sensor is elastic of the elastic support portion. An image forming apparatus is provided that is pressed against the fixing member by a repulsive force.
[0019]
  In the image forming apparatus, when the intermediate transfer member is displaced in a direction perpendicular to the traveling direction, the temperature sensor is kept in good contact with the intermediate transfer member, and the temperature of the intermediate transfer member is accurately adjusted. Can be measured. Therefore, the intermediate transfer member can be appropriately heated by the heating device. Then, when the toner image is heated on the intermediate transfer member and transferred and fixed onto the recording medium at the same time, particularly when a color image is formed, an image with little color misregistration can be obtained.
[0020]
  The invention according to claim 6 is the image forming apparatus according to claim 1 or 5.The bent portion is formed by bending a leaf spring continuous with the elastic support portion so that an angle formed by the elastic support portion and the bent portion is 90 ° or more and 180 ° or less. To do.
[0021]
  The elastic support portion and the bent portion are continuous at 90 ° to 180 °, and when the contact pressure with the object to be measured acts on the temperature sensor, the bent portion is not greatly deformed in the axial direction. The temperature sensor follows the advance and retreat of the endless belt. Further, the bent portion is formed of a leaf spring continuous with the elastic support portion, and the elastic support portion and the bent portion can be easily manufactured with a small number of man-hours.
[0022]
  The invention according to claim 7 is the image forming apparatus according to claim 1 or 5.The bent portion includes a locking portion that is displaced in the axial direction of the bent portion and prevents the bent portion from falling off from the restraint in the restraint portion.
[0023]
  the aboveImage forming apparatusThen, it can prevent that a bending part moves in the direction which falls from the restraint in a restraint part by the elastic repulsive force of an elastic support part. That is, when the contact pressure does not act on the temperature sensor, a force that pulls the bent portion in the direction in which the bent portion is joined to the elastic support portion acts along the axis, but it is possible to prevent the locking portion from coming out of the restraining portion. The curved form of the elastic support part is maintained.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the invention according to the present application will be described with reference to the drawings.
  FIG.Claim 11 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the invention.is there.
  The image forming apparatus shown in FIG. 1 includes a cylindrical photosensitive drum 1 on which a latent image due to a difference in electrostatic potential is formed by irradiating image light after uniform charging, and this photosensitive drum. 1, a charging device 2 for uniformly charging the surface of the photosensitive drum 1, an exposure device 3 for irradiating the photosensitive drum 1 with image light to form a latent image on the surface, and a photosensitive drum A developing unit 4 that selectively transfers toner to the latent image to form a toner image, an endless belt-like intermediate transfer member 5 that is opposed to the photosensitive drum 1 and is supported so that the circumferential surface can circulate, and a toner image A cleaning device 6 that removes toner remaining on the photosensitive drum 1 after the transfer of the toner, and a static elimination exposure device 7 that neutralizes the surface of the photosensitive drum 1.
[0025]
  Further, inside the intermediate transfer member 5, a transfer charger 8 for primarily transferring the toner image formed on the photosensitive drum to the intermediate transfer member 5, two supporting rolls 9a and 9b, and secondary transfer are performed. A transfer counter roll 10 for carrying out is disposed, and the intermediate transfer body 5 is stretched around these rolls so as to be able to go around. A transfer roll 11 for transferring a toner image on the intermediate transfer body onto a recording sheet is disposed at a position facing the transfer opposing roll 10 via the intermediate transfer body 5. The transfer opposing roll 10 and the transfer roll The recording paper is fed from a paper tray (not shown) to the press contact portion with the paper 11. On the downstream side of the pressure contact portion, a fixing device 12 that heats and melts the toner image on the recording paper and press-bonds it to the recording paper, and a cleaning device 13 that removes the toner remaining on the intermediate transfer member along the intermediate transfer member 5. And are provided.
[0026]
  The photoreceptor drum 1 has a photoreceptor layer made of various inorganic photosensitive materials such as Se, a-Si, a-SiC, and Cds, organic photosensitive materials, amorphous selenium photosensitive materials, amorphous silicon photosensitive materials, etc. on the drum surface. It can be used.
[0027]
  The charging device 2 is obtained by coating a metal roll having conductivity such as stainless steel or aluminum with a coating of a high resistance material. The charging device 2 is in contact with the photosensitive drum 1 and is driven to rotate. When a predetermined voltage is applied, a continuous discharge is generated in a minute gap in the vicinity of the contact portion between the roll and the photosensitive drum 1, and the surface of the photosensitive drum 1 is charged almost uniformly. It is.
[0028]
  The exposure device 3 generates a flashing laser beam based on an image signal, and scans this in the main scanning direction of the photosensitive drum 1 by a polygon mirror. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 1.
[0029]
  The developing unit 4 is rotatably supported by four developing units containing yellow, magenta, cyan, and black toners. Each developing unit sequentially approaches and opposes the photosensitive drum 1 for each color. A visible image is formed by transferring toner to a corresponding latent image.
[0030]
  The belt-shaped intermediate transfer member 5 has a two-layer structure of a base layer and a surface layer. The base layer is made of polyimide, polyamide, polyamideimide, etc. in consideration of heat resistance, strength, and surface smoothness. A heat-resistant resin, a metal such as aluminum or stainless steel is used, and a silicone rubber, fluorine rubber, or the like that has high heat resistance and high releasability from the toner is used for the surface layer.
[0031]
  The transfer charger 8 applies a voltage to the back surface of the intermediate transfer member 5 by applying a voltage so that the toner image on the photosensitive drum 1 is efficiently transferred to the intermediate transfer member 5.
[0032]
  The transfer roll 11 is made of a conductive or semiconductive roll-shaped member, and applies a voltage to the transfer facing roll 10 to collectively transfer the toner image on the intermediate transfer body onto the recording paper.
[0033]
  Next, the details of the configuration of the fixing device 12 will be described with reference to FIG.
  The fixing device 12 includes an endless belt-shaped heating rotator 21, an electromagnetic induction heating device 22 supported at a position facing the peripheral surface of the heating rotator 21, and a pressure roll pressed against the heating rotator 21. 23, a pressure member 24 supported by the inner peripheral surface of the heating rotator 21 and sandwiching the heating rotator 21 between the pressure roll 23, and a downstream of the pressure contact portion between the pressure roll 23 and the pressure member 24 And a peeling member 25 supported in the vicinity of the side. In addition, a temperature detection device 26 that measures the temperature of the inner peripheral surface of the heating rotator 21 is provided in the vicinity of the upstream side of the press-contact portion between the pressure roll 23 and the pressing member 24, and is provided near the outer peripheral surface of the heating rotator 21. A circulation speed sensor 27 is provided.
[0034]
  The heating rotator 21 has a belt-like conductive layer 21a as a base layer, and an elastic layer 21b and a surface release layer 21b are laminated thereon. The conductive layer 21a is made of, for example, a magnetic metal such as iron, magnetic stainless steel, or nickel, or a main alloy thereof, a nonmagnetic metal such as nonmagnetic stainless steel, aluminum, or copper, or a main alloy thereof with a thickness of 5 μm to 50 μm. The formed material is used, and the material is selected so as to have a specific resistance value that allows sufficient heat generation by electromagnetic induction. The elastic layer 21b is for making the surface of the heating rotator 21 in close contact with the toner image on the recording paper, and has heat resistance, high thermal conductivity such as silicone rubber, fluorine rubber, fluorosilicone rubber, etc. It is desirable that the thickness is 10 μm to 500 μm and the hardness is 600 (JIS-KA type tester) or less. The surface release layer 21c has a thickness of 1 μm to 100 μm and is made of fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA (tetrafluoroethylene-perfluoroalkoxyvinyl ether copolymer), PTFE (polytetrafluoro). Ethylene), FEP (tetrafluoroethylene-hexafluoropropylene copolymer) and the like having high mold release properties and heat resistance can be used. In addition, the surface release layer 21c, which is the outermost layer of the heating rotator 21, has a singularity that reflects the light emitted from the circumferential speed sensor 27 in order to detect the circumferential speed of the heating rotator by the circumferential speed sensor 27. A plurality of reflectors are provided.
  The heating rotator 21 has a sheet-like member with high heat resistance represented by polyimide, polyimide amide and the like as a base layer, and a conductive layer formed thereon, and further an elastic layer and a surface release layer laminated thereon. It may be a thing.
[0035]
  The pressure roll 23 has a metal cylindrical cored bar 23a as a core material, and includes an elastic layer 23b such as sponge or rubber on the surface of the cored bar 23a. The pressure roll 23 is rotationally driven by a drive motor (not shown), and the heating rotator 21 is driven to rotate accordingly.
[0036]
  The electromagnetic induction heating device 22 is arranged along the outer peripheral surface of the heating rotator 21 so that the gap with the outer peripheral surface is 1 to 3 mm, and generates heat in the conductive layer of the heating rotator 21. is there. The electromagnetic induction heating device 22 includes a magnetic core 22b made of ferrite or the like supported by a pedestal 22a, an excitation coil 22c wound around the magnetic core 22b, and supplies an alternating current to the excitation coil 22c. The main part is composed of the excitation circuit 22d. The pedestal 22a is non-magnetic and heat-resistant, and heat-resistant resin such as polycarbonate, PPS (polyphenylene sulfide), heat-resistant glass, liquid crystal polymer, or the like is used. The magnetic core 22b has a single core block or a plurality of core blocks arranged continuously.
[0037]
  The pressure member 24 includes an elastic member 24b curved in a shape along the peripheral surface of the pressure roll 23, a pressure applying member 24c having a protrusion on the downstream side of the process from the elastic member 24b, and the heating rotator 21. A belt travel guide (not shown) arranged along the inner peripheral surface is supported by both ends in the width direction by holders 24a made of metal or heat resistant resin.
[0038]
  A magnetic body 24f that collects magnetic flux that has passed through the conductive layer 21a of the heating rotator 21 is disposed on a portion of the metal holder 24a that faces the electromagnetic induction heating device 22, and a heating rotator is provided on the magnetic body 24f. A guide pad 24g for guiding the heating rotator is provided along the inner peripheral surface of the heating pad. The magnetic body 24f is made of a magnetic material such as iron, cobalt, nickel, and ferrite, and the guide pad 24g is made of a material having low thermal conductivity that hardly causes heat transfer from the heating rotator 21.
[0039]
  The elastic member 24b is in pressure contact with the pressure roll 23 and has a concave shape following the circumferential surface of the pressure roll 23. Therefore, a sufficient pressure contact width is provided between the elastic member 24b and the pressure roll 23 via the heating rotator 21. Can be obtained. Further, a low friction layer 24e is provided on the surface of the elastic member 24b, and friction with the inner peripheral surface of the heating rotator 21 can be reduced.
[0040]
  The pressure applying member 24c is made of a material harder than the elastic layer 23b of the pressure roll 23, and the elastic layer 23b of the pressure roll 23 is in a pressure contact portion between the pressure applying member 24c and the pressure roll 23. Distortion occurs. In the portion where the distortion occurs, a difference occurs between the moving speed of the recording paper P sandwiched between the heating rotator 21 and the pressure roll 23 and the rotating speed of the heating rotator 21, and the recording paper P and the heating rotation. The adhesive force with the body 21 is reduced, and the recording paper P is easily peeled off.
[0041]
  The belt travel guide is made of a material having a low coefficient of friction because it slides on the inner peripheral surface of the heating rotator 21 and a low thermal conductivity in order to reduce the amount of heat transfer from the heating rotator 21. Things are desirable.
[0042]
  The release member 25 includes a support member 25a having one end fixedly supported and a release sheet 25b supported by the support member 25a. The release member 25b is disposed so that the tip of the release sheet 25b is close to or in contact with the heating rotator 21. Yes. As a result, the release sheet 25 b enters between the recording paper P that has passed through the press contact portion and the heating rotator 21, and the recording paper P is peeled from the heating rotator 21.
[0043]
  The temperature detection device 26 is in contact with the heating rotator 21 and detects the temperature of the heating rotator 21, and supports the temperature sensor 31, and the temperature sensor 31 is connected to the inner peripheral surface of the heating rotator 21. And a restraining member 33 for restraining the support member 32 so that a part of the support member 32 is curved. The amount of power supplied from the excitation circuit 22d to the excitation coil 22c is controlled by the detection value of the temperature sensor 31, and the surface temperature of the heating rotator 21 is maintained at a desired temperature.
[0044]
  The temperature sensor 31 measures the temperature in contact with the object to be measured, and a thermocouple using the Seebeck effect, a thermistor using an element having a large temperature coefficient of resistance, or the like is used. Since these contact-type temperature sensors are inexpensive, the cost of the apparatus can be reduced.
[0045]
  The support member 32 is continuous with the elastic support portion 32a supported so as to be elastically curved with a curvature larger than the curvature of the heating rotator 21, and is bent at about 90 °. A bent portion 32b, and a locking portion 32c formed by bending the tip of the bent portion 32b. One end of the elastic support portion 32a is fixed to the restraining member 33, and the temperature sensor 31 attached to the other end is pressed against the inner peripheral surface of the heating rotator 21 by the elastic repulsive force of the curved elastic support portion 32a. The support member 32 may be formed by bending a single plate spring to form an elastic support portion 32a, a bent portion 32b, and a locking portion 32c, or a plate spring serving as the elastic support portion 32a. Other members may be joined to form the bent portion 32b and the locking portion 32c. The leaf spring preferably has a spring constant k of 0.01 N / mm to 1 N / mm, a thickness of 0.05 mm to 1.0 mm, and a width of 0.5 mm to 2 mm.
[0046]
  The restraining member 33 is a plate-like member or block-like member made of a heat-resistant resin such as PPS (polyphenylene sulfide), and is fixed to the pressure member 24 and provided with holes or slits serving as guides 33a. A bent portion 32b of the support member 32 is inserted into the guide 33a, and the bent portion is constrained in a direction perpendicular to the axial direction and guided so as to be movable in the axial direction.
[0047]
  Due to the restraint of the bent portion 32b, the elastic support portion 32a is deformed to be curved, and the contact pressure when the temperature sensor 31 attached to the outside of the curved surface is pressed against the heating rotator 21 is reduced. Can do. And since the bending part 32b can move to an axial direction, the temperature sensor 31 can advance / retreat with the elastic repulsive force of the elastic support part 32a, and follows the displacement of the heating rotary body 21. Yes. Further, when the bent portion 32b moves in the direction of dropping from the guide 33a due to the repulsive force of the elastic support portion 32a, the locking portion 32c is locked by the restraining member 33, and the falling of the bent portion 32b from the guide 33a is suppressed. It has become a thing.
[0048]
  The circumferential speed sensor 27 irradiates light toward the peripheral surface of the heating rotator 21 and detects light reflected by the reflector provided on the peripheral surface of the heating rotator 21. And from the circumference of the heating rotator, or the distance between the reflectors when a plurality of reflectors are provided, and the time from detection of the first reflected light to detection of the next reflected light, The rotating speed of the heating rotator 21 is detected.
[0049]
  The toner used in the image forming apparatus is composed of a thermoplastic binder containing a yellow, magenta, cyan, or black pigment, and can be formed of a known material.
[0050]
  Next, operations of the image forming apparatus and the fixing device 12 will be described.
  First, the surface of the photosensitive drum 1 is charged almost uniformly by the charging device 2, and then image light is irradiated from the exposure device 3 to form a latent image on the surface of the photosensitive drum 1 due to the difference in electrostatic potential. . Then, the photosensitive drum 1 rotates to move to a position facing one developing device 4a of the developing unit 4, and the first color toner is transferred from the developing device 4a to form a toner image. This toner image is conveyed to a position facing the intermediate transfer member 5 by the circumferential movement of the photosensitive drum 1, and is electrostatically primary-transferred onto the intermediate transfer member.
[0051]
  On the other hand, the toner remaining on the photosensitive drum 1 after the primary transfer is removed by the cleaning device 7, and the surface of the photosensitive drum 1 is potentialally initialized by the static elimination exposure device 8, and again at a position facing the charging device 2. Moving.
  Thereafter, the three developing devices 4b, 4c, and 4d of the developing unit 4 sequentially move to positions facing the photosensitive drum 1, and similarly, toner images of the second, third, and fourth colors are sequentially formed, and the intermediate transfer member is formed. 5 is superimposed and transferred.
[0052]
  The toner image T superimposed on the intermediate transfer member is conveyed to a position where the transfer roller 11 and the transfer counter roller 10 face each other by the circumferential movement of the intermediate transfer member 5, and comes into contact with the recording paper P fed from the paper tray. Is done. A transfer bias voltage is applied between the transfer roll 11 and the intermediate transfer member 5, and the toner image T is secondarily transferred onto the recording paper.
[0053]
  The recording paper P carrying the unfixed toner image T is conveyed to the fixing device 12 and sent between the heating rotator 21 and the pressure roll 23 of the fixing device 12. Then, the recording paper P is heated and pressed by the heating rotator 21 heated to a predetermined temperature by the electromagnetic induction heating device 22 and the pressure roll 23, and the toner image T is melt-pressed on the recording paper P. The recording paper P is in a state where the elastic layer 23b of the pressure roll 23 is deformed by the pressure applying member 24c and is easily peeled off from the heating rotator 21, and is further peeled off from the heating rotator 21 by the peeling member 25. The
[0054]
  In the fixing device 12, excitation is performed from the excitation circuit 22 d of the electromagnetic induction heating device 22 almost simultaneously with or immediately after the pressure roll 23 starts driving and the heating rotator 21 is driven to start the circulation. An alternating current is supplied to the coil 22c. When an alternating current is supplied to the exciting coil 22c, the magnetic flux indicated by the arrow H around the exciting coil 22c repeats generation and disappearance. Then, when this magnetic flux H crosses the conductive layer 21a of the heating rotator 21, an eddy current is generated in the conductive layer 21a so as to generate a magnetic field that hinders the change of the magnetic field, and the conductive layer 21a Heat is generated in proportion to the magnitude of the current flowing through the skin resistance and the conductive layer 21a. On the other hand, the magnetic flux penetrating through the conductive layer 21a forms a closed path toward the magnetic body 24f included in the pressing member 24.
[0055]
  On the other hand, when the heating rotator 21 moves around, the shape of the peripheral surface changes because the heating rotator 21 is supported in a tensionless state. With this change in shape, the heating rotator 21 is displaced in the direction perpendicular to the peripheral surface even at the position where the temperature sensor 31 is in contact. On the other hand, as shown in FIG. 3, in the temperature detection device 32, the elastic support portion 32 a is deformed and the bent portion 32 b slides with respect to the restraining member 33, so that the temperature sensor 31 is The contact state is always maintained following the advance and retreat. Thereby, the temperature sensor 31 accurately detects the temperature of the heating rotator 21. Based on this detection value, power supply from the excitation circuit 22d to the excitation coil 22c is controlled, and the surface of the heating rotator 21 is heated to a desired temperature.
[0056]
  At this time, since the elastic support portion 32a is curved in advance by restraining the bent portion 32b, the amount of displacement due to the contact pressure between the heating rotator 21 and the temperature sensor 31 is reduced. Thereby, the contact pressure between the temperature sensor 31 and the inner peripheral surface of the heating rotator 21 is kept small, and it is possible to appropriately follow the displacement of the heating rotator 21. Therefore, the temperature can be accurately detected without excessively deforming the heating rotator 21 that is a flexible belt-like member.
[0057]
  Compared with the elastic support portion 32a, in the elastic support portion 32a ′ whose one end is fixed as shown in FIG. 4, the elastic support portion 32a ′ is largely displaced by the contact pressure with the heating rotator 21 ′. The contact pressure is also increasing. Furthermore, since the movement of the elastic support portion 32 a ′ is not guided, it is difficult to slide the temperature sensor 31 ′ in a stable state with respect to the inner peripheral surface of the heating rotator 21. For this reason, an error may occur in the detection value of the temperature sensor 31 ′. Further, the temperature sensor 31 ′ is strongly pressed against the heating rotator 21 ′, and a bulge protruding on the peripheral surface of the heating rotator 21 ′ is generated, or the inner peripheral surface of the heating rotator is damaged.
[0058]
  FIG. 5 is a schematic configuration diagram showing another temperature detection device that can be used in the fixing device 12.
  The temperature detection device supports a temperature sensor 41 and a contact-type temperature sensor 41 such as a thermocouple or a thermistor for detecting the temperature of the heating rotator 21, and the temperature sensor 41 is used as an inner peripheral surface of the heating rotator 21. And a restraining member 43 that restrains the support member 42 so that a part of the support member 42 is curved.
[0059]
  The support member 42 includes an elastic support portion 42a, a bent portion 42b, and a locking portion 42c, like the support member 32 included in the temperature detection device 26. The restraining member 43 is made of a heat-resistant resin, and a hole or slit serving as the guide 43a is provided so as to pass through the center of gravity of the heating rotator 21. The bent portion 42b is inserted into the guide 43a. The elastic support portion 42 a that supports the temperature sensor 41 and the tangent line of the heating rotator 21 substantially coincide with each other at a position where the temperature sensor 41 is in contact with the heating rotator 21. In this temperature detection device, the pressure contact force due to the displacement of the peripheral surface of the heating rotator 21 is efficiently transmitted to the bent portion 42b, and the bent portion 42b is easily guided by the guide 43a. For this reason, the temperature sensor 41 follows the shape of the peripheral surface of the heating rotator 21 and is pressed against the inner peripheral surface of the heating rotator 21 so that the temperature can be accurately detected.
[0060]
  FIG.Claim 51 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the invention.
  This image forming apparatus includes a cylindrical photosensitive drum 51 on which a latent image due to a difference in electrostatic potential is formed, a charging device 52, an exposure device 53, and a developing unit 54 around the photosensitive drum 51. , An endless belt intermediate transfer member 55, a cleaning device 56, and a static elimination exposure device 57. In addition, on the inner side of the intermediate transfer member 55, a transfer charger 58 that primarily transfers the toner image formed on the photosensitive drum to the intermediate transfer member 55, two support rolls 59a and 59b, and secondary transfer is performed. A transfer roll 60 is disposed, and the intermediate transfer body 55 is stretched around these so as to be able to go around. Further, a pressure roll 61 is disposed at a position facing the transfer roll 60 via the intermediate transfer member 55, and the intermediate transfer member 55 and the intermediate transfer member are disposed along the inner peripheral surface of the intermediate transfer member 55. An electromagnetic induction heating device 62 for heating the upper toner image, a temperature detection device 63 for measuring the temperature of the intermediate transfer member, and a cleaning device 64 are provided along the outer peripheral surface.
  The photosensitive drum 51, the charging device 52, the exposure device 53, the developing unit 54, the cleaning device 56, the static elimination exposure device 57, and the transfer charging device 58 can be the same as the image forming apparatus shown in FIG. .
[0061]
  The intermediate transfer member 5 is composed of three layers: a base layer made of a sheet member having high heat resistance, a conductive layer laminated thereon, and a surface release layer which is the uppermost layer. The material of the layer is selected so as to have a specific resistance value that allows sufficient heat generation by electromagnetic induction. In addition, the surface release layer is preferably a sheet or coat layer having high release properties, and in consideration of electrostatic transfer properties of the toner image during primary transfer, a conductive material such as carbon black is dispersed to provide resistance. You may use the sheet | seat which adjusted.
[0062]
  The temperature detection device 63 can be the same as the temperature detection device 26 included in the fixing device shown in FIG. 2, and the temperature sensor is pressed against the inner peripheral surface of the intermediate transfer member 55 by the elastic repulsion force of the elastic support portion. Thus, the temperature is detected.
[0063]
  In this image forming apparatus, the plurality of toner images T transferred from the photosensitive drum 51 onto the intermediate transfer body 55 and overlaid with a plurality of colors are opposed to the electromagnetic induction heating device 62 by the circumferential movement of the intermediate transfer body 5. Pass through the heating zone. The toner image T is heated and melted on the intermediate transfer member, and is conveyed to the pressure contact portion between the transfer roll 60 and the pressure roll 61. The recording paper P is fed from a paper tray (not shown) between the intermediate transfer body 55 and the pressure roll 61 in time with this conveyance, and the toner image T is pressed against the recording paper P to transfer and fix. Are performed simultaneously.
[0064]
  At this time, the power supplied to the electromagnetic induction heating device 62 is controlled by the detection value of the temperature detection device 63 so that the surface temperature of the intermediate transfer member 55 maintains a desired temperature. In this temperature detection device 63, since the elastic repulsion force of the elastic support portion is suppressed, the temperature sensor is strongly pressed against the intermediate transfer body 55 to prevent the intermediate transfer body 55 from being excessively deformed or damaged. it can.
[0065]
【The invention's effect】
  As explained above, according to the present inventionIn the image forming apparatus, the temperature detecting deviceSince the bent portion is constrained so that the elastic support portion is curved, the axis of the bent portion is maintained while the temperature sensor attached to the elastic support portion is in contact with the measured object by the contact pressure of the measured object. Move in the direction. And since the elastic repulsion force of an elastic support part is suppressed, a temperature sensor can contact a to-be-measured body by appropriate press-contact force, and can measure temperature correctly, without damaging to-be-measured body.Then, the toner image can be satisfactorily fixed by accurately controlling the temperature of the fixing member or the intermediate transfer member, which is the measurement object.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the invention according to claim 1;Is1 is a schematic configuration diagram of an image forming apparatus.
2 has the image forming apparatus shown in FIG.Fixing deviceIt is a schematic block diagram.
3 is a diagram for explaining a change in shape of a temperature detection device included in the fixing device shown in FIG. 2; FIG.
4 is a diagram for explaining a change in shape of the temperature detection device compared with the temperature detection device shown in FIG. 3; FIG.
FIG. 5 is a schematic configuration diagram showing another temperature detection device that can be used in the fixing device shown in FIG. 2;
[Fig. 6]Claim 51 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the invention.
FIG. 7 is a diagram for explaining the operation of the temperature detection device according to the first aspect of the present invention.
FIG. 8 is a diagram for explaining the operation of the temperature detection device compared with the temperature detection device shown in FIG. 7;
FIG. 9 is a schematic configuration diagram illustrating a fixing device having a conventional temperature sensor.
[Explanation of symbols]
  1, 51 Photosensitive drum
  2,52 Charging device
  3, 53 Exposure equipment
  4, 54 Development unit
  5, 55 Intermediate transfer member
  6, 56 Cleaning device
  7, 57 Static elimination exposure equipment
  8,58 Transfer charger
  9, 59 Support roll
10 Transfer facing roll
11, 60 Transfer roll
12 Fixing device
13, 64 Cleaning device
21 Heating rotating body
22, 62 Electromagnetic induction heating device
23, 61 Pressure roll
24 Pressure pad
25 Peeling member
26, 63 Temperature detector
27 Orbital speed sensor
31, 41 Temperature sensor
32, 42 Support member
33, 43 Restraint member

Claims

An image forming unit that selectively transfers toner to a latent image due to a difference in charging potential formed on the image carrier to form a toner image;
A transfer portion for transferring the formed toner image onto a recording medium;
A fixing member pressed against the recording medium carrying the toner image;
A heating device for heating the fixing member to a predetermined temperature;
A temperature detecting device for detecting the temperature of the fixing member,
The temperature detector is
A temperature sensor for detecting the temperature of the fixing member in contact with the fixing member;
An elastic support portion comprising a leaf spring, one end fixedly supported, and the temperature sensor mounted near the other end;
A bent portion that is continuous at a predetermined angle on the opposite side of the surface of the elastic support portion to which the temperature sensor is attached, opposite to the surface to which the temperature sensor is attached;
A constraining portion that restrains the bent portion in a direction perpendicular to the axial direction and holds the movably in the axial direction so that the elastic support portion is in a curved state;
The image forming apparatus, wherein the temperature sensor is pressed against the fixing member by an elastic repulsive force of the elastic support portion.

The fixing member is an endless belt that is driven in a circumferential direction.
There is an end portion to which the elastic support portion is fixed on the upstream side in the circumferential direction of the endless belt, and the portion provided with the bent portion of the elastic support portion is disposed on the downstream side,
The image forming apparatus according to claim 1, wherein the temperature sensor is in contact with a peripheral surface of the endless belt.

The temperature sensor is in contact with the inner peripheral surface of the endless belt,
The image forming apparatus according to claim 2, wherein the curvature of the elastic support portion is larger than the curvature of the endless belt in the vicinity of a position where the temperature sensor is in contact.

The image forming apparatus according to claim 2, wherein the endless belt is supported in a tensionless state.

An image forming unit that selectively transfers toner to a latent image due to a difference in charging potential formed on the image carrier to form a toner image;
An intermediate transfer body to which the formed toner image is once transferred;
A heating device for heating the intermediate transfer member to a predetermined temperature;
A temperature detecting device for detecting the temperature of the intermediate transfer member;
A transfer fixing unit that transfers the toner image to a recording medium and fixes the toner image at the same time,
The temperature detector is
A temperature sensor that contacts the intermediate transfer member and detects the temperature of the intermediate transfer member;
An elastic support portion comprising a leaf spring, one end fixedly supported, and the temperature sensor mounted near the other end;
A bent portion that is continuous at a predetermined angle on the opposite side of the surface of the elastic support portion to which the temperature sensor is attached, opposite to the surface to which the temperature sensor is attached;
A constraining portion that restrains the bent portion in a direction perpendicular to the axial direction and holds the movably in the axial direction so that the elastic support portion is in a curved state;
The image forming apparatus, wherein the temperature sensor is pressed against the fixing member by an elastic repulsive force of the elastic support portion.

The bent portion is formed by bending a leaf spring continuous with the elastic support portion so that an angle formed by the elastic support portion and the bent portion is 90 ° or more and 180 ° or less. The image forming apparatus according to claim 1 or 5 .

6. The image forming apparatus according to claim 1 , wherein the bent portion includes a locking portion that is displaced in an axial direction of the bent portion and prevents the bent portion from falling off from the restraint in the restraint portion. .