JP3962639B2

JP3962639B2 - Heater control device

Info

Publication number: JP3962639B2
Application number: JP2002181508A
Authority: JP
Inventors: 智広玉置
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2002-06-21
Filing date: 2002-06-21
Publication date: 2007-08-22
Anticipated expiration: 2022-06-21
Also published as: JP2004028622A

Description

【０００１】
【発明の属する技術分野】
本発明は、非接触の温度検出装置に係るヒータ制御装置に関し、特に電子写真装置，静電記録装置等の画像形成装置に用いられる定着装置の温度検出に好適な温度検出装置に関するものである。
【０００２】
【従来の技術】
ヒータにより加熱される定着ローラを用いた定着装置は、複写機やレーザプリンタ等の画像形成装置において多用されている。
【０００３】
このような定着装置では、定着ローラの表面温度を所定温度に維持するためのサーミスタや、定着ローラの異常昇温時にヒータへの通電経路を遮断するための温度ヒューズ，サーモスイッチ等の温度検知素子を定着ローラ表面に当接させている。
【０００４】
このため、接触キズが定着ローラに発生し、白スジ，黒スジ，定着不良などの問題が発生することがある。
【０００５】
そこで、温度検知手段を、記録材の通過領域である画像域外において定着ローラに当接させる手法が考えられるが、画像域内の温度検知が不可能であることや、定着装置が大型化するため、最近では温度検知手段を画像域内において定着ローラに非接触に近接させる手法が考えられている。
【０００６】
この非接触温度検知手段は、開口部を有するケーシングと、このケーシングに内装されるとともに、開口部を通過した赤外線を吸収する高分子材料から成る赤外線吸収フィルムと、この赤外線吸収フィルムに密着するように配設した赤外線検知用のサーミスタ素子と、ケーシングの温度を検出する温度補償用のサーミスタ素子を備えたものである。
【０００７】
この非接触温度検知手段は、ケーシングの開口部を通過した赤外線がその開口部の直下に配設した赤外線吸収フィルムに吸収されることによって赤外線吸収フィルムの温度が上昇し、赤外線吸収フィルムに密着して配設したサーミスタ素子がその温度変化を検出する。図７のように赤外線検知用サーミスタ素子１０と温度補償用サーミスタ素子１１はともに同等の温度−抵抗特性のものを使用しており、同一の抵抗値の固定抵抗Ｒ１およびＲ２がそれぞれ直列に接続されている。
【０００８】
対象物からの赤外線を赤外線吸収フィルムが吸収するとフィルムの温度が上昇し、赤外線検知用サーミスタの抵抗値が温度補償用サーミスタに比して小さくなるため、ｂ＞ａとなっており、電圧ａと電圧ｂをＡ／Ｄコンバータによりデジタル値に変換してマイクロコンピュータに取り込むか、電圧ａと電圧ｂの電位差を図４で示されるように抵抗ブリッジ回路でＡ−Ｂ間の電位差に相当する出力電圧をｃとして検出して、電圧ｃと電圧ｂをＡ／Ｄコンバータによりデジタル値に変換してマイクロコンピュータに取り込み、マイクロコンピュータはこれらの２つの電圧のデジタル値をデータテーブルもしくは関数により変換して定着ローラの温度を検出している。
【０００９】
【発明が解決しようとする課題】
しかしながら、前述の従来例で説明した非接触温度検知手段を用いた温度検出手法では、定着ローラの温度制御中に赤外線検知用サーミスタ素子の故障や伝送線が断線してオープン状態になった場合、出力電圧ａが基準電圧Ｖと同じになってしまうため、ａとｂの関係が逆転してｂ＜ａとなる。また、温度補償用サーミスタ素子の短絡や伝送線が筐体と短絡した場合には出力電圧ｂがＧＮＤと同じになってしまうため、同様にａとｂの関係が逆転してｂ＜ａとなる。するとマイクロコンピュータが出力電圧ａとｂもしくはａとｃのデジタル値を基に温度に変換した際に、定着ローラの温度を実際より低い温度として検出してしまい、定着ローラを加熱し続ける結果、サーモスイッチ等の安全装置が働くまで定着ローラが過昇温してしまうと言う問題があった。
【００１０】
本発明は、このような状況のもとでなされたもので、非接触の温度検知手段を用いた、感熱素子の断線や短絡による故障を正確に検出できるヒータ制御装置を提供することを目的とするものである。
【００１１】
【課題を解決するための手段】
前記目的を達成するため、本発明では、ヒータ制御装置を次の（１）ないし（８）のとおりに構成する。
【００１２】
（１）加熱対象を加熱するヒータと、前記加熱対象からの赤外線を吸収するフィルムと、前記フィルムの温度に応じて抵抗が変化する第１の温度検知素子と、前記フィルムを保持する保持体の温度に応じて抵抗が変化する温度補償用の第２の温度検知素子と、前記第１の温度検知素子と第１の抵抗素子を直列接続した第１の直列回路と、前記第２の温度検知素子と第２の抵抗素子を直列接続した第２の直列回路とを並列接続した抵抗ブリッジ回路における、前記第１の温度検知素子と前記第１の抵抗素子の接続点の電圧である第１の電圧と、前記第２の温度検知素子と前記第２の抵抗素子の接続点の電圧である第２の電圧とに基づいて前記加熱対象の温度を検出し、前記ヒータへの通電を制御する制御手段と、を有し、前記制御手段は、前記第１の電圧が前記第１の温度検知素子の断線を示す電圧の場合、及び、前記第２の電圧が前記第２の温度検知素子の短絡を示す電圧の場合、前記ヒータへの通電を停止することを特徴とするヒータ制御装置。
（２）前記（１）記載のヒータ制御装置において、前記制御手段は、前記第１の電圧が前記第１の温度検知素子の断線を示す電圧の場合、及び、前記第２の電圧が前記第２の温度検知素子の短絡を示す電圧の場合、表示手段に故障表示を行わせることを特徴とするヒータ制御装置。
（３）加熱対象を加熱するヒータと、前記加熱対象からの赤外線を吸収するフィルムと、前記フィルムの温度に応じて抵抗が変化する第１の温度検知素子と、前記フィルムを保持する保持体の温度に応じて抵抗が変化する温度補償用の第２の温度検知素子と、前記第１の温度検知素子と第１の抵抗素子を直列接続した第１の直列回路と、前記第２の温度検知素子と第２の抵抗素子を直列接続した第２の直列回路とを並列接続した抵抗ブリッジ回路における、前記第１の温度検知素子と第１の抵抗素子の接続点の電圧である第１の電圧と、前記第２の温度検知素子と第２の抵抗素子の接続点の電圧である第２の電圧とをデジタル値に変換して、これらの２つのデジタル値に基づいて前記加熱対象の温度を検出し、前記ヒータへの通電を制御する制御手段と、を有し、前記制御手段は、前記第１の電圧から変換されたデジタル値が前記第１の温度検知素子の断線を示す値の場合、及び、前記第２の電圧から変換されたデジタル値が前記第２の温度検知素子の短絡を示す値の場合、前記ヒータへの通電を停止することを特徴とするヒータ制御装置。
（４）前記（３）記載のヒータ制御装置において、前記制御手段は、前記第１の電圧から変換されたデジタル値が前記第１の温度検知素子の断線を示す値の場合、及び、前記第２の電圧から変換されたデジタル値が前記第２の温度検知素子の短絡を示す値の場合、表示手段に故障表示を行わせることを特徴とするヒータ制御装置。
（５）加熱対象を加熱するヒータと、前記加熱対象からの赤外線を吸収するフィルムと、前記フィルムの温度に応じて抵抗が変化する第１の温度検知素子と、前記フィルムを保持する保持体の温度に応じて抵抗が変化する温度補償用の第２の温度検知素子と、前記第１の温度検知素子と第１の抵抗素子を直列接続した第１の直列回路と、前記第２の温度検知素子と第２の抵抗素子を直列接続した第２の直列回路とを並列接続した抵抗ブリッジ回路における、前記第１の温度検知素子と第１の抵抗素子の接続点の電圧である第１の電圧と、前記第２の温度検知素子と第２の抵抗素子の接続点の電圧である第２の電圧と、前記第１の電圧と前記第２の電圧の差分の電圧である第３の電圧のうち、前記第１の電圧もしくは前記第２の電圧と前記第３の電圧とに基づいて前記加熱対象の温度を検出し、前記ヒータへの通電を制御する制御手段と、を有し、前記制御手段は、前記第１の電圧が前記第１の温度検知素子の断線を示す電圧の場合、及び、前記第２の電圧が前記第２の温度検知素子の短絡を示す電圧の場合、前記ヒータへの通電を停止することを特徴とするヒータ制御装置。
（６）前記（５）記載のヒータ制御装置において、前記制御手段は、前記第１の電圧が前記第１の温度検知素子の断線を示す電圧の場合、及び、前記第２の電圧が前記第２の温度検知素子の短絡を示す電圧の場合、表示手段に故障表示を行わせることを特徴とするヒータ制御装置。
（７）加熱対象を加熱するヒータと、前記加熱対象からの赤外線を吸収するフィルムと、前記フィルムの温度に応じて抵抗が変化する第１の温度検知素子と、前記フィルムを保持する保持体の温度に応じて抵抗が変化する温度補償用の第２の温度検知素子と、前記第１の温度検知素子と第１の抵抗素子を直列接続した第１の直列回路と、前記第２の温度検知素子と第２の抵抗素子を直列接続した第２の直列回路とを並列接続した抵抗ブリッジ回路における、前記第１の温度検知素子と第１の抵抗素子の接続点の電圧である第１の電圧と、前記第２の温度検知素子と第２の抵抗素子の接続点の電圧である第２の電圧と、前記第１の電圧と前記第２の電圧の差分の電圧である第３の電圧のうち、第１の電圧もしくは第２の電圧と第３の電圧をデジタル値に変換して、これらの２つのデジタル値に基づいて前記加熱対象の温度を検出し、前記ヒータへの通電を制御する制御手段と、を有し、前記制御手段は、前記第１の電圧から変換されたデジタル値が前記第１の温度検知素子の断線を示す値の場合、及び、前記第２の電圧から変換されたデジタル値が前記第２の温度検知素子の短絡を示す値の場合、前記ヒータへの通電を停止することを特徴とするヒータ制御装置。
（８）前記（７）記載のヒータ制御装置において、前記制御手段は、前記第１の電圧から変換されたデジタル値が前記第１の温度検知素子の断線を示す値の場合、及び、前記第２の電圧から変換されたデジタル値が前記第２の温度検知素子の短絡を示す値の場合、表示手段に故障表示を行わせることを特徴とするヒータ制御装置。
【００２１】
【発明の実施の形態】
以下本発明の実施の形態を、画像記録装置に用いられる、温度検出装置の実施例により詳しく説明する。
【００２２】
【実施例】
（実施例１）
記録紙上の未定着画像を定着させる画像記録装置は、画像記録装置内部に、図示を省略したが、表面に静電潜像を形成する像担持体、像担持体の表面の電荷を除電する前露光手段、像担持体の表面を所望の電位に帯電させる１次帯電手段、帯電した像担持体上を露光して静電潜像を形成させる露光手段、像担持体上の静電潜像を現像剤で現像して可視像化する現像器、現像器で現像された像担持体上のトナー画像を記録材に転写する転写装置等が設けられている。また、記録材に転写されたトナー画像を、加熱および加圧された定着ローラにより溶融定着させるローラ定着装置である定着ユニットが画像記録装置の所定位置に配置され、各部材により画像形成の各プロセスが適宜実行されることにより所望の画像を得ることができるようになっている。なお、記録材には記録紙やＯＨＰ用紙などが用いられる。
【００２３】
次に図５により定着ユニットの構成を説明する。図５において、２は加熱ローラであり、アルミニウム，鉄等のパイプ材にシリコーンゴム，フッ素ゴム等の耐熱弾性体の層を形成し表面にＰＦＡ，ＰＴＦＥといった離型層を被覆したローラである。前記加熱ローラ２に圧接して配設された加圧ローラ３も加熱ローラと同様に芯金の上にシリコーンゴム，フッ素ゴム等の耐熱弾性体の層を形成したローラである。前記加熱ローラ（加熱部材）２と加圧ローラ（バックアップ部材）３には記録材Ｓが通紙され、記録材Ｓ上のトナーＴは加熱ローラ２と加圧ローラ３との間で加熱および加圧されて定着される。前記加熱ローラ２の内部にはヒータ４が配設されており、加熱ローラ２を内部より加熱する。また前記加熱ローラ２の表面温度を検知するために温度検知手段たる温度検知素子５が加熱ローラに面して非接触に配置されており、加熱ローラ２の温度を検出する。温度検知素子５からのデータに基づいて加熱ローラ２の表面温度を所定の設定温度（プリント温度）または非定着時の待機温度（スタンバイ温度）に保つようになっている。加熱ローラにはまた、過昇温を検知するため、サーモスイッチ６が非接触に配設されており、過昇温が検知された場合、ヒータへの通電を遮断するようになっている。
【００２４】
次に、温度検知素子５の構成について詳細を図６を用いて説明する。図６において、７はアルミ等熱伝導性の高い材料でできたケースであり、ケース７の一面に設けた開口部８に加熱ローラから放射される赤外光を吸収する耐熱フィルム９が閉塞するように設けられる。耐熱フィルム９のケース内面側には、赤外線検知用サーミスタ素子１０を接着剤等で密着させて固定する。赤外線検知用サーミスタ素子１０の近傍には、ケース内の雰囲気温度を測定するための温度補償用サーミスタ素子１１を配設する。赤外線検知用サーミスタ素子１０と温度補償用サーミスタ素子１１のリード線１２は、ケース７に設けたソケット（図示なし）にそれぞれ接続して外部に取り出すようにする。
【００２５】
次に、温度検知素子５の動作について簡単に説明する。まず、ケース７の開口部８に取り付けた樹脂フィルム９に加熱ローラ２からの赤外線が入射すると、フィルム９に赤外線が吸収されてフィルム９の温度が赤外線量に応じて上昇する。そして、樹脂フィルム９の温度は、フィルム裏面に密着固定した赤外線検知用サーミスタ素子１０に伝導してサーミスタ素子１０の抵抗変化として検出する。赤外線検知用サーミスタ素子１０の抵抗は、ケースの温度による影響を受けており、温度補償用サーミスタ素子１１を用いて、ケース温度に相当する温度を検出してその影響を排除している。ここでケーシングをアルミ等熱伝導性の高い材料でできたケースにするのは、雰囲気温度の変化に対する温度補償用サーミスタ素子１１の追従性を向上させるためである。
【００２６】
次に実施例１である、前記温度検知素子５を用いた、“温度検出装置”を、図１を用いて説明する。
【００２７】
図１において、赤外線検知用サーミスタ素子１０と温度補償用サーミスタ素子１１はそれぞれ３３ｋΩの抵抗素子Ｒ１，Ｒ２と直列に接続されて、基準電源Ｖとグランドの間に接続されている。すなわち、赤外線検知用サーミスタ素子１０，温度補償用サーミスタ素子１１，抵抗素子Ｒ１，Ｒ２は抵抗ブリッジ回路を構成しており、この抵抗ブリッジ回路には基準電源電圧が印加されている。抵抗ブリッジ回路の出力である、赤外線検知用サーミスタ素子１０と温度補償用サーミスタ素子１１の出力はそれぞれ電圧ａ，ｂである。電圧ａ，ｂは８ｂｉｔＡ／Ｄコンバータ１２，１３に入力され、電圧ａに対応するデジタル出力ｊと電圧ｂに対応するデジタル出力ｋがマイクロコンピュータ１６で読まれる。マイコン１６はそれらのデジタル出力をデータテーブルに当てはめ、加熱ローラ２の温度を検出し、その温度が目標温度以下の場合はヒータ４に通電し、目標温度以上の場合は通電を止める。出力電圧ａはコンパレータ１４にも入力され、固定抵抗Ｒ３とＲ４により分圧された電圧値ＶＨと比較される。ＶＨは赤外線検知サーミスタが極低温であっても電圧出力ａが超えないように設定されている。赤外線検知用サーミスタ素子は例えば０℃であっても１０００ｋΩの抵抗値を持っており、それに対して抵抗素子Ｒ１は３３ｋΩに設定されているため、Ｒ３＝３３ｋΩ、Ｒ４＝１．５ＭΩとすることで極低温下でも赤外線検知サーミスタが断線していなければコンパレータ１４の出力ｍは“Ｌ”となっている。一方、赤外線検知サーミスタが断線してａ＝Ｖとなると、コンパレータ１４の出力ｍが“Ｈ”となり、マイコン１６は信号ｍを入力ポートで読み取ることで赤外線検知用サーミスタ１０もしくはその伝送線が断線していると判断し、ヒータ４への通電を止めるとともに装置の動作を停止して、表示装置に温度検知素子５が故障したことを表示する。また、出力電圧ｂはコンパレータ１５にも入力され、固定抵抗Ｒ５とＲ６により分圧された電圧値ＶＬと比較される。ＶＬは温度補償用サーミスタ１１が通常使用状態での最高温度であっても電圧出力ｂが下回らないように設定されている。温度補償用サーミスタ素子１１は例えば１８０℃であっても７ｋΩの抵抗値を持っており、それに対して抵抗素子Ｒ２は３３ｋΩに設定されているため、Ｒ５＝３３ｋΩ、Ｒ６＝５．６ｋΩとすることで通常使用状態ではコンパレータ１５の出力ｎは“Ｌ”となっている。一方、温度補償用サーミスタが短絡してｂ＝ＧＮＤとなると、コンパレータ１５の出力ｎが“Ｈ”となり、マイコン１６は信号ｎを入力ポートで読み取ることで温度補償用サーミスタ１１もしくはその伝送線が短絡していると判断し、ヒータ４への通電を止めるとともに装置の動作を停止して、表示装置に温度検知素子５が故障したことを表示する。
【００２８】
なお、本実施例では過昇温を防止するために赤外線検知用サーミスタの断線と温度補償用サーミスタの短絡を検知するように構成したが、さらにコンパレータを追加することで、赤外線検知用サーミスタの短絡や温度補償用サーミスタの断線を検知するようにすれば、より効果的である。
【００２９】
以上説明したように、本実施例によれば、赤外線検知サーミスタおよび温度補償用サーミスタの故障を検知することができ、定着ローラが過昇温する前にヒータへの通電を停止することが可能となる。
【００３０】
（実施例２）
次に実施例２である“温度検出装置”を図２を用いて説明する。赤外線検知用サーミスタ素子１０と温度補償用サーミスタ素子１１はそれぞれ３３ｋΩの抵抗素子Ｒ１，Ｒ２と直列に接続されて、基準電源Ｖとグランドの間に接続されている。すなわち、赤外線検知用サーミスタ素子１０，温度補償用サーミスタ素子１１，抵抗素子Ｒ１，Ｒ２は抵抗ブリッジ回路を構成しており、この抵抗ブリッジ回路には基準電源電圧が印加されている。抵抗ブリッジ回路の出力である、赤外線検知用サーミスタ素子１０と温度補償用サーミスタ素子１１の出力はそれぞれ電圧ａ，ｂである。電圧ａ，ｂは８ｂｉｔＡ／Ｄコンバータ１２，１３に入力され、電圧ａに対応するデジタル出力ｊと電圧ｂに対応するデジタル出力ｋがマイクロコンピュータ１６で読まれる。マイコン１６はそれらのデジタル出力をデータテーブルに当てはめ、加熱ローラ２の温度を検出し、その温度が目標温度以下の場合はヒータ４に通電し、目標温度以上の場合は通電を止める。マイコン１６は同時に赤外線検知サーミスタの断線検知のため、デジタル値ｊの値がＦＦＨかどうかを判定する。赤外線検知用サーミスタ素子は例えば０℃であっても１０００ｋΩの抵抗値を持っており、それに対して抵抗素子Ｒ１は３３ｋΩに設定されているため、０℃という低温下であっても、デジタル出力はＦ７Ｈとなり、断線以外でＦＦＨとなることはない。デジタル値ｊの値がＦＦＨであった場合、赤外線検知用サーミスタ１０もしくはその伝送線が断線していると判断し、ヒータ４への通電を止めるとともに装置の動作を停止して、表示装置に温度検知素子５が故障したことを表示する。
【００３１】
さらにマイコン１６は温度補償用サーミスタの短絡検知のため、デジタル値ｋの値が３０Ｈ以下かどうかを判定する。温度補償用サーミスタ素子は通常の使用状態においては１８０℃以上の高温になることは無く、デジタル値が所定値３０Ｈ以下になったことで、サーミスタ素子や伝送線のグランドとの短絡異常と判断でき、ヒータ４への通電を止めるとともに装置の動作を停止して、表示装置に温度検知素子５が故障したことを表示する。
【００３２】
以上説明したように、本実施例では過昇温を防止するために赤外線検知用サーミスタの断線と温度補償用サーミスタの短絡を検知するように構成したが、さらにデジタル値ｊが３０Ｈ以下であった場合に赤外線検知用サーミスタの短絡と判断し、また、デジタル値ｋの値がＦＦＨであった場合に温度補償用サーミスタの断線と判断するようにすれば、より効果的である。
【００３３】
（実施例３）
次に実施例３である“温度検出装置”を図３を用いて説明する。赤外線検知用サーミスタ素子１０と温度補償用サーミスタ素子１１はそれぞれ３３ｋΩの抵抗素子Ｒ１，Ｒ２と直列に接続されて、基準電源Ｖとグランドの間に接続されている。すなわち、赤外線検知用サーミスタ素子１０，温度補償用サーミスタ素子１１，抵抗素子Ｒ１，Ｒ２は抵抗ブリッジ回路を構成しており、この抵抗ブリッジ回路には基準電源電圧が印加されている。抵抗ブリッジ回路の出力である、赤外線検知用サーミスタ素子１０と温度補償用サーミスタ素子１１の出力はそれぞれ電圧ａ，ｂである。差動増幅回路１７は電圧ａ，ｂを入力としており、１５倍に増幅された出力が電圧ｃである。電圧ａ，ｃは８ｂｉｔＡ／Ｄコンバータ１２，１３に入力され、電圧ａに対応するデジタル出力ｊと電圧ｃに対応するデジタル出力ｍがマイクロコンピュータ１６で読まれる。マイコン１６はそれらのデジタル出力をデータテーブルに当てはめ、加熱ローラ２の温度を検出し、その温度が目標温度以下の場合はヒータ４に通電し、目標温度以上の場合は通電を止める。本実施例では、電圧ａとｃにより温度検出するようにしたが、電圧ａの代りに電圧ｂを使用することも可能である。
【００３４】
出力電圧ａはコンパレータ１４にも入力され、固定抵抗Ｒ３とＲ４により分圧された電圧値ＶＨと比較される。ＶＨは赤外線検知サーミスタが極低温であっても電圧出力ａが超えないように設定されている。赤外線検知用サーミスタ素子は例えば０℃であっても１０００ｋΩの抵抗値を持っており、それに対して抵抗素子Ｒ１は３３ｋΩに設定されているため、Ｒ３＝３３ｋΩ，Ｒ４＝１．５ＭΩとすることで極低温下でも赤外線検知サーミスタが断線していなければコンパレータ１４の出力ｍは“Ｌ”となっている。一方、赤外線検知サーミスタが断線してａ＝Ｖとなると、コンパレータ１４の出力ｍが“Ｈ”となり、マイコン１６は信号ｍを入力ポートで読み取ることで赤外線検知用サーミスタ１０もしくはその伝送線が断線していると判断し、ヒータ４への通電を止めるとともに装置の動作を停止して、表示装置に温度検知素子５が故障したことを表示する。また、出力電圧ｂはコンパレータ１５にも入力され、固定抵抗Ｒ５とＲ６により分圧された電圧値ＶＬと比較される。ＶＬは温度補償用サーミスタが通常使用状態での最高温度であっても電圧出力ｂが下回らないように設定されている。温度補償用サーミスタ素子は例えば１８０℃であっても７ｋΩの抵抗値を持っており、それに対して抵抗素子Ｒ１は３３ｋΩに設定されているため、Ｒ３＝３３ｋΩ，Ｒ４＝５．６ｋΩとすることで通常使用状態ではコンパレータ１５の出力ｎは“Ｌ”となっている。一方、温度補償用サーミスタが短絡してｂ＝ＧＮＤとなると、コンパレータ１５の出力ｎが“Ｈ”となり、マイコン１６は信号ｎを入力ポートで読み取ることで温度補償用サーミスタ１１もしくはその伝送線が短絡していると判断し、ヒータ４への通電を止めるとともに装置の動作を停止して、表示装置に温度検知素子５が故障したことを表示する。
【００３５】
本実施例では過昇温を防止するために赤外線検知用サーミスタの断線と温度補償用サーミスタの短絡を検知するように構成したが、さらにコンパレータを追加することで、赤外線検知用サーミスタの短絡や温度補償用サーミスタの断線を検知するようにすればより効果的である。
【００３６】
（実施例４）
次に実施例４である“温度検出装置”を図４を用いて説明する。赤外線検知用サーミスタ素子１０と温度補償用サーミスタ素子１１はそれぞれ３３ｋΩの抵抗素子Ｒ１，Ｒ２と直列に接続されて、基準電源Ｖとグランドの間に接続されている。すなわち、赤外線検知用サーミスタ素子１０，温度補償用サーミスタ素子１１，抵抗素子Ｒ１，Ｒ２は抵抗ブリッジ回路を構成しており、この抵抗ブリッジ回路には基準電源電圧が印加されている。抵抗ブリッジ回路の出力である、赤外線検知用サーミスタ素子１０と温度補償用サーミスタ素子１１の出力はそれぞれ電圧ａ，ｂである。差動増幅回路１７は電圧ａ，ｂを入力としており、１５倍に増幅された出力が電圧ｃである。電圧ａ，ｂ、ｃは８ｂｉｔＡ／Ｄコンバータ１２，１３、１８に入力され、電圧ａに対応するデジタル出力ｊと電圧ｂに対応するデジタル出力ｎおよび電圧ｃに対応するデジタル出力ｍがマイクロコンピュータ１６で読まれる。マイコン１６はそれらのデジタル出力のうちｊとｍをデータテーブルに当てはめ、加熱ローラ２の温度を検出し、その温度が目標温度以下の場合はヒータ４に通電し、目標温度以上の場合は通電を止める。本実施例では、デジタル出力ｊとｍにより温度検出するようにしたが、デジタル出力ｊの代わりにｎを使用することも可能である。
【００３７】
マイコン１６は同時に赤外線検知サーミスタの断線検知のため、デジタル値ｊの値がＦＦＨかどうかを判定する。赤外線検知用サーミスタ素子は例えば０℃であっても１０００ｋΩの抵抗値を持っており、それに対して抵抗素子Ｒ１は３３ｋΩに設定されているため、０℃という低温下であっても、デジタル出力はＦ７Ｈとなり、断線以外でＦＦＨとなることはない。デジタル値ｊの値がＦＦＨであった場合、赤外線検知用サーミスタ１０もしくはその伝送線が断線していると判断し、ヒータ４への通電を止めるとともに装置の動作を停止して、表示装置に温度検知素子５が故障したことを表示する。さらにマイコン１６は温度補償用サーミスタの短絡検知のため、デジタル値ｎの値が３０Ｈ以下かどうかを判定する。温度補償用サーミスタ素子は通常の使用状態においては１８０℃以上の高温になることは無く、デジタル値が所定値３０Ｈ以下になったことで、サーミスタ素子や伝送線のグランドとの短絡異常と判断でき、ヒータ４への通電を止めるとともに装置の動作を停止して、表示装置に温度検知素子５が故障したことを表示する。
【００３８】
本実施例では過昇温を防止するために赤外線検知用サーミスタの断線と温度補償用サーミスタの短絡を検知するように構成したが、さらにデジタル値ｊが３０Ｈ以下であった場合に赤外線検知用サーミスタの短絡と判断し、また、デジタル値ｎの値がＦＦＨであった場合に温度補償用サーミスタの断線と判断するようにすればより効果的である。
【００３９】
【発明の効果】
以上説明したように、本発明によれば、加熱対象を加熱するヒータと、前記加熱対象からの赤外線を吸収するフィルムの温度に応じて抵抗が変化する第１の温度検知素子と、前記フィルムを保持する保持体の温度に応じて抵抗が変化する温度補償用の第２の温度検知素子と、前記第１の温度検知素子と第１の抵抗素子の接続点の電圧である第１の電圧と、前記第２の温度検知素子と第２の抵抗素子の接続点の電圧である第２の電圧とに基づいて前記加熱対象の温度を検出し、前記ヒータへの通電を制御する制御手段とを有し、前記制御手段は、前記第１の電圧が前記第１の温度検知素子の断線を示す電圧の場合、及び、前記第２の電圧が前記第２の温度検知素子の短絡を示す電圧の場合、前記ヒータへの通電を停止するので、前記第１及び第２の温度検知素子の故障時の加熱対象の過昇温を未然に防止できる。
【図面の簡単な説明】
【図１】実施例１の要部構成を示す図
【図２】実施例２の要部構成を示す図
【図３】実施例３の要部構成を示す図
【図４】実施例４の要部構成を示す図
【図５】定着ユニットの構成を示す断面図
【図６】温度検知素子の詳細を示す断面図
【図７】従来例の説明図
【符号の説明】
７ケース
９耐熱フィルム
１０赤外線検知用サーミスタ素子
１１温度補償用サーミスタ素子
１６マイクロコンピュータ
Ｒ１，Ｒ２抵抗[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a non-contact temperature detecting device.Heater control device according toIn particular, the present invention relates to a temperature detection device suitable for temperature detection of a fixing device used in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus.
[0002]
[Prior art]
A fixing device using a fixing roller heated by a heater is widely used in image forming apparatuses such as copying machines and laser printers.
[0003]
In such a fixing device, a thermistor for maintaining the surface temperature of the fixing roller at a predetermined temperature, a temperature detection element such as a temperature fuse, a thermo switch, etc. for cutting off the energization path to the heater when the fixing roller is abnormally heated. Is brought into contact with the surface of the fixing roller.
[0004]
For this reason, contact scratches may occur on the fixing roller, and problems such as white streaks, black streaks, and poor fixing may occur.
[0005]
Therefore, a method of bringing the temperature detection means into contact with the fixing roller outside the image area, which is the recording material passage area, can be considered, but because the temperature detection in the image area is impossible or the fixing device is enlarged, Recently, a method has been considered in which the temperature detecting means is brought close to the fixing roller in a non-contact manner in the image area.
[0006]
The non-contact temperature detection means is in close contact with the casing having an opening, an infrared absorbing film made of a polymer material that absorbs infrared rays that pass through the opening, and is attached to the infrared absorbing film. And a thermistor element for temperature compensation for detecting the temperature of the casing.
[0007]
This non-contact temperature detecting means is that the infrared ray that has passed through the opening of the casing is absorbed by the infrared ray absorbing film disposed immediately below the opening, whereby the temperature of the infrared ray absorbing film rises and adheres to the infrared ray absorbing film. The thermistor element arranged in this way detects the temperature change. As shown in FIG. 7, both the infrared detecting thermistor element 10 and the temperature compensating thermistor element 11 have the same temperature-resistance characteristics, and fixed resistors R1 and R2 having the same resistance value are connected in series. ing.
[0008]
When the infrared ray absorbing film absorbs infrared rays from the object, the temperature of the film rises, and the resistance value of the infrared detecting thermistor becomes smaller than that of the temperature compensating thermistor, so b> a, and the voltage a The voltage b is converted into a digital value by an A / D converter and taken into a microcomputer, or the potential difference between the voltage a and the voltage b is output as a potential difference between A and B in a resistance bridge circuit as shown in FIG. Is detected as c, and the voltage c and voltage b are converted into digital values by an A / D converter and taken into a microcomputer. The microcomputer converts the digital values of these two voltages by a data table or function and fixes them. The temperature of the roller is detected.
[0009]
[Problems to be solved by the invention]
However, in the temperature detection method using the non-contact temperature detection means described in the above-mentioned conventional example, when the infrared detection thermistor element is broken or the transmission line is disconnected during the temperature control of the fixing roller, Since the output voltage a becomes the same as the reference voltage V, the relationship between a and b is reversed and b <a. Further, when the temperature compensation thermistor element is short-circuited or the transmission line is short-circuited to the housing, the output voltage b becomes the same as GND, and similarly, the relationship between a and b is reversed and b <a. . Then, when the microcomputer converts the temperature based on the digital values of the output voltages a and b or a and c, the temperature of the fixing roller is detected as a lower temperature than the actual temperature. There was a problem that the fixing roller would overheat until a safety device such as a switch worked.
[0010]
  The present invention has been made under such circumstances, and can accurately detect a failure due to disconnection or short circuit of a thermal element using a non-contact temperature detection means.Heater control deviceIs intended to provide.
[0011]
[Means for Solving the Problems]
  In order to achieve the above object, in the present invention,Heater controlConfigure the device as described in (1) to (8) below.CompleteThe
[0012]
  (1)A heater for heating an object to be heated, and the heatingFilm that absorbs infrared rays from the object, and the temperature of the filmResistance changes according toDoFirst temperature detectionTemperature of element and holding body for holding the filmResistance changes according toFor temperature compensationSecond temperature detectionAn element and saidFirst temperature detectionA first series circuit in which an element and a first resistance element are connected in series;,SaidSecond temperature detectionIn a resistance bridge circuit in which an element and a second series circuit in which a second resistance element is connected in series are connected in parallel,First temperature detectionElement andSaidFirst resistance elementContactThe first voltage that is the voltage at the junctionPower ofPressure and,in frontRecordSecond temperature detectionElement andSaidSecond resistance elementContactThe second voltage that is the voltage at the junctionPower ofWith pressureOn the basis ofSaidheatingDetect target temperatureAnd control means for controlling energization to the heaterWhen,The control means includesThe firstPower ofPressureButSaidWhen the voltage indicates a disconnection of the first temperature detection element, and when the second voltage is a voltage indicating a short circuit of the second temperature detection element, the energization to the heater is stopped.It is characterized byHeater controlapparatus.
(2) In the heater control device according to (1), the control unit may be configured such that the first voltage is a voltage indicating a disconnection of the first temperature detection element, and the second voltage is the first voltage. In the case of a voltage indicating a short circuit of the two temperature detection elements, a heater control device that causes the display means to display a failure.
(3) A heater that heats the heating target, a film that absorbs infrared rays from the heating target, a first temperature detection element whose resistance changes according to the temperature of the film, and a holding body that holds the film A second temperature sensing element for temperature compensation whose resistance changes according to temperature, a first series circuit in which the first temperature sensing element and the first resistance element are connected in series, and the second temperature sensing A first voltage which is a voltage at a connection point of the first temperature detection element and the first resistance element in a resistance bridge circuit in which an element and a second series circuit in which the second resistance element is connected in series is connected in parallel And a second voltage, which is a voltage at a connection point between the second temperature detection element and the second resistance element, is converted into a digital value, and the temperature of the heating object is determined based on these two digital values. Detect and control energization to the heater And when the digital value converted from the first voltage is a value indicating a disconnection of the first temperature detection element, and the control means is converted from the second voltage. When the digital value is a value indicating a short circuit of the second temperature detection element, the heater control device stops energization of the heater.
(4) In the heater control apparatus according to (3), the control unit may be configured such that the digital value converted from the first voltage is a value indicating the disconnection of the first temperature detection element, and the first A heater control device, wherein when the digital value converted from the voltage of 2 is a value indicating a short circuit of the second temperature detection element, the display means performs a failure display.
(5) A heater that heats the heating target, a film that absorbs infrared rays from the heating target, a first temperature detection element whose resistance changes according to the temperature of the film, and a holding body that holds the film A second temperature sensing element for temperature compensation whose resistance changes according to temperature, a first series circuit in which the first temperature sensing element and the first resistance element are connected in series, and the second temperature sensing A first voltage which is a voltage at a connection point of the first temperature detection element and the first resistance element in a resistance bridge circuit in which an element and a second series circuit in which the second resistance element is connected in series is connected in parallel A second voltage that is a voltage at a connection point between the second temperature detection element and the second resistance element, and a third voltage that is a difference voltage between the first voltage and the second voltage. Of these, the first voltage or the second voltage and the third voltage Control means for detecting the temperature of the object to be heated based on the voltage and controlling energization to the heater, wherein the control means is configured such that the first voltage is a disconnection of the first temperature detection element. And a heater control device that stops energization of the heater when the second voltage is a voltage indicating a short circuit of the second temperature detection element.
(6) In the heater control apparatus according to (5), the control unit may be configured such that the first voltage is a voltage indicating a disconnection of the first temperature detection element, and the second voltage is the first voltage. In the case of a voltage indicating a short circuit of the two temperature detection elements, a heater control device that causes the display means to display a failure.
(7) A heater that heats the heating target, and a film that absorbs infrared rays from the heating target. A first temperature sensing element whose resistance changes according to the temperature of the film; a second temperature sensing element for temperature compensation whose resistance changes according to the temperature of the holding body for holding the film; A resistance in which a first series circuit in which one temperature detection element and a first resistance element are connected in series and a second series circuit in which the second temperature detection element and a second resistance element are connected in series are connected in parallel In the bridge circuit, a first voltage that is a voltage at a connection point between the first temperature detection element and the first resistance element, and a voltage at a connection point between the second temperature detection element and the second resistance element. Of the second voltage and the third voltage that is the difference voltage between the first voltage and the second voltage, the first voltage or the second voltage and the third voltage are converted into digital values. The temperature of the heating object is detected based on these two digital values. Control means for controlling energization to the heater, wherein the control means is a digital value converted from the first voltage is a value indicating a disconnection of the first temperature detection element, and When the digital value converted from the second voltage is a value indicating a short circuit of the second temperature detection element, energization of the heater is stopped.
(8) In the heater control apparatus according to (7), the control unit may be configured such that the digital value converted from the first voltage is a value indicating a disconnection of the first temperature detection element, and the first A heater control device, wherein when the digital value converted from the voltage of 2 is a value indicating a short circuit of the second temperature detection element, the display means performs a failure display.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to examples of temperature detection devices used in image recording apparatuses.
[0022]
【Example】
Example 1
The image recording apparatus for fixing the unfixed image on the recording paper is omitted inside the image recording apparatus, but before the charge on the surface of the image carrier that forms an electrostatic latent image is eliminated. Exposure means, primary charging means for charging the surface of the image carrier to a desired potential, exposure means for exposing the charged image carrier to form an electrostatic latent image, and electrostatic latent image on the image carrier A developing device that develops with a developer to form a visible image, a transfer device that transfers the toner image on the image carrier developed by the developing device to a recording material, and the like are provided. Also, a fixing unit, which is a roller fixing device that melts and fixes the toner image transferred to the recording material by a heated and pressurized fixing roller, is disposed at a predetermined position of the image recording device, and each process of image formation by each member Is appropriately executed so that a desired image can be obtained. Note that recording paper, OHP paper, or the like is used as the recording material.
[0023]
Next, the configuration of the fixing unit will be described with reference to FIG. In FIG. 5, reference numeral 2 denotes a heating roller, which is a roller in which a layer of a heat-resistant elastic body such as silicone rubber or fluorine rubber is formed on a pipe material such as aluminum or iron and a release layer such as PFA or PTFE is coated on the surface. The pressure roller 3 disposed in pressure contact with the heating roller 2 is also a roller in which a layer of a heat-resistant elastic body such as silicone rubber or fluororubber is formed on a core metal like the heating roller. The recording material S is passed through the heating roller (heating member) 2 and the pressure roller (backup member) 3, and the toner T on the recording material S is heated and heated between the heating roller 2 and the pressure roller 3. It is pressed and fixed. A heater 4 is disposed inside the heating roller 2 and heats the heating roller 2 from the inside. In addition, a temperature detecting element 5 serving as a temperature detecting means for detecting the surface temperature of the heating roller 2 is disposed in a non-contact manner facing the heating roller, and detects the temperature of the heating roller 2. Based on the data from the temperature detection element 5, the surface temperature of the heating roller 2 is maintained at a predetermined set temperature (printing temperature) or a standby temperature during non-fixing (standby temperature). The heating roller is also provided with a thermo switch 6 in a non-contact manner for detecting an excessive temperature rise. When the excessive temperature rise is detected, the heater is cut off from energization.
[0024]
Next, the configuration of the temperature detection element 5 will be described in detail with reference to FIG. In FIG. 6, 7 is a case made of a material having high thermal conductivity such as aluminum, and a heat-resistant film 9 that absorbs infrared light emitted from the heating roller is blocked in an opening 8 provided on one surface of the case 7. It is provided as follows. An infrared detection thermistor element 10 is adhered and fixed to the case inner surface side of the heat-resistant film 9 with an adhesive or the like. In the vicinity of the infrared detecting thermistor element 10, a temperature compensating thermistor element 11 for measuring the ambient temperature in the case is disposed. The lead wires 12 of the infrared detecting thermistor element 10 and the temperature compensating thermistor element 11 are connected to sockets (not shown) provided in the case 7 and taken out to the outside.
[0025]
Next, the operation of the temperature detection element 5 will be briefly described. First, when infrared rays from the heating roller 2 are incident on the resin film 9 attached to the opening 8 of the case 7, the infrared rays are absorbed by the film 9, and the temperature of the film 9 rises according to the amount of infrared rays. The temperature of the resin film 9 is detected as a resistance change of the thermistor element 10 by being conducted to the infrared detecting thermistor element 10 that is closely fixed to the back surface of the film. The resistance of the infrared detection thermistor element 10 is affected by the temperature of the case. The temperature compensation thermistor element 11 is used to detect the temperature corresponding to the case temperature and eliminate the influence. The reason why the casing is made of a case made of a material having high thermal conductivity such as aluminum is to improve the followability of the temperature compensating thermistor element 11 with respect to changes in the ambient temperature.
[0026]
Next, a “temperature detection apparatus” using the temperature detection element 5 according to the first embodiment will be described with reference to FIG.
[0027]
In FIG. 1, an infrared detection thermistor element 10 and a temperature compensation thermistor element 11 are connected in series with 33 kΩ resistance elements R1 and R2, respectively, and connected between a reference power supply V and the ground. That is, the infrared detection thermistor element 10, the temperature compensation thermistor element 11, and the resistance elements R1 and R2 constitute a resistance bridge circuit, and a reference power supply voltage is applied to the resistance bridge circuit. Outputs of the infrared detection thermistor element 10 and the temperature compensation thermistor element 11 that are outputs of the resistance bridge circuit are voltages a and b, respectively. The voltages a and b are input to the 8-bit A / D converters 12 and 13, and the digital output j corresponding to the voltage a and the digital output k corresponding to the voltage b are read by the microcomputer 16. The microcomputer 16 applies these digital outputs to the data table, detects the temperature of the heating roller 2, energizes the heater 4 when the temperature is lower than the target temperature, and stops energization when the temperature is higher than the target temperature. The output voltage a is also input to the comparator 14 and is compared with the voltage value VH divided by the fixed resistors R3 and R4. VH is set so that the voltage output a does not exceed even when the infrared detection thermistor is at a very low temperature. For example, the thermistor element for infrared detection has a resistance value of 1000 kΩ even at 0 ° C., whereas the resistance element R1 is set to 33 kΩ, so that R3 = 33 kΩ and R4 = 1.5 MΩ. If the infrared detection thermistor is not disconnected even at a very low temperature, the output m of the comparator 14 is “L”. On the other hand, when the infrared detection thermistor is disconnected and a = V, the output m of the comparator 14 becomes “H”, and the microcomputer 16 reads the signal m at the input port, thereby disconnecting the infrared detection thermistor 10 or its transmission line. The heater 4 is turned off and the operation of the apparatus is stopped, and the display device displays that the temperature detecting element 5 has failed. The output voltage b is also input to the comparator 15 and compared with the voltage value VL divided by the fixed resistors R5 and R6. VL is set so that the voltage output b does not drop even when the temperature compensation thermistor 11 is at the maximum temperature in the normal use state. The temperature compensation thermistor element 11 has a resistance value of 7 kΩ even at 180 ° C., for example, and the resistance element R2 is set to 33 kΩ, so that R5 = 33 kΩ and R6 = 5.6 kΩ. In the normal use state, the output n of the comparator 15 is “L”. On the other hand, when the temperature compensation thermistor is short-circuited and b = GND, the output n of the comparator 15 becomes “H”, and the microcomputer 16 reads the signal n at the input port so that the temperature compensation thermistor 11 or its transmission line is short-circuited. The heater 4 is turned off and the operation of the apparatus is stopped, and the display device displays that the temperature detecting element 5 has failed.
[0028]
In this embodiment, in order to prevent overheating, the infrared detection thermistor is disconnected and the temperature compensation thermistor is short-circuited. However, by adding a comparator, the infrared detection thermistor is short-circuited. It is more effective if the disconnection of the temperature compensation thermistor is detected.
[0029]
As described above, according to this embodiment, it is possible to detect a failure of the infrared detection thermistor and the temperature compensation thermistor, and to stop energizing the heater before the fixing roller overheats. Become.
[0030]
(Example 2)
Next, a “temperature detection apparatus” which is Embodiment 2 will be described with reference to FIG. The infrared detecting thermistor element 10 and the temperature compensating thermistor element 11 are connected in series with the 33 kΩ resistance elements R1 and R2, respectively, and connected between the reference power supply V and the ground. That is, the infrared detection thermistor element 10, the temperature compensation thermistor element 11, and the resistance elements R1 and R2 constitute a resistance bridge circuit, and a reference power supply voltage is applied to the resistance bridge circuit. Outputs of the infrared detection thermistor element 10 and the temperature compensation thermistor element 11 that are outputs of the resistance bridge circuit are voltages a and b, respectively. The voltages a and b are input to the 8-bit A / D converters 12 and 13, and the digital output j corresponding to the voltage a and the digital output k corresponding to the voltage b are read by the microcomputer 16. The microcomputer 16 applies these digital outputs to the data table, detects the temperature of the heating roller 2, energizes the heater 4 when the temperature is lower than the target temperature, and stops energization when the temperature is higher than the target temperature. At the same time, the microcomputer 16 determines whether the value of the digital value j is FFH in order to detect disconnection of the infrared detection thermistor. The thermistor element for infrared detection has a resistance value of 1000 kΩ even at 0 ° C., for example, and the resistance element R 1 is set to 33 kΩ, so that the digital output is low even at a low temperature of 0 ° C. F7H, and FFH will not occur except for disconnection. When the value of the digital value j is FFH, it is determined that the infrared detection thermistor 10 or its transmission line is disconnected, the heater 4 is turned off and the operation of the device is stopped, and the temperature of the display device is reduced. It displays that the detection element 5 has failed.
[0031]
Further, the microcomputer 16 determines whether or not the digital value k is 30H or less in order to detect a short circuit of the temperature compensation thermistor. The temperature compensation thermistor element does not reach a high temperature of 180 ° C or higher under normal use conditions, and it can be determined that the thermistor element or the transmission line ground is short-circuited abnormally because the digital value is 30H or less. Then, the energization of the heater 4 is stopped and the operation of the apparatus is stopped, and the display device displays that the temperature detecting element 5 has failed.
[0032]
As described above, in this embodiment, in order to prevent an excessive temperature rise, a disconnection of the infrared detection thermistor and a short circuit of the temperature compensation thermistor are detected, but the digital value j is 30H or less. In this case, it is more effective if it is determined that the infrared detection thermistor is short-circuited, and if the digital value k is FFH, it is determined that the temperature compensation thermistor is disconnected.
[0033]
(Example 3)
Next, a “temperature detection apparatus” which is Embodiment 3 will be described with reference to FIG. The infrared detecting thermistor element 10 and the temperature compensating thermistor element 11 are connected in series with the 33 kΩ resistance elements R1 and R2, respectively, and connected between the reference power supply V and the ground. That is, the infrared detection thermistor element 10, the temperature compensation thermistor element 11, and the resistance elements R1 and R2 constitute a resistance bridge circuit, and a reference power supply voltage is applied to the resistance bridge circuit. Outputs of the infrared detection thermistor element 10 and the temperature compensation thermistor element 11 that are outputs of the resistance bridge circuit are voltages a and b, respectively. The differential amplifier circuit 17 receives the voltages a and b, and the output amplified 15 times is the voltage c. The voltages a and c are input to the 8-bit A / D converters 12 and 13, and the digital output j corresponding to the voltage a and the digital output m corresponding to the voltage c are read by the microcomputer 16. The microcomputer 16 applies these digital outputs to the data table, detects the temperature of the heating roller 2, energizes the heater 4 when the temperature is lower than the target temperature, and stops energization when the temperature is higher than the target temperature. In this embodiment, the temperature is detected by the voltages a and c, but the voltage b can be used instead of the voltage a.
[0034]
The output voltage a is also input to the comparator 14 and is compared with the voltage value VH divided by the fixed resistors R3 and R4. VH is set so that the voltage output a does not exceed even when the infrared detection thermistor is at a very low temperature. For example, the thermistor element for infrared detection has a resistance value of 1000 kΩ even at 0 ° C., whereas the resistance element R1 is set to 33 kΩ, so that R3 = 33 kΩ and R4 = 1.5 MΩ. If the infrared detection thermistor is not disconnected even at a very low temperature, the output m of the comparator 14 is “L”. On the other hand, when the infrared detection thermistor is disconnected and a = V, the output m of the comparator 14 becomes “H”, and the microcomputer 16 reads the signal m at the input port, thereby disconnecting the infrared detection thermistor 10 or its transmission line. The heater 4 is turned off and the operation of the apparatus is stopped, and the display device displays that the temperature detecting element 5 has failed. The output voltage b is also input to the comparator 15 and compared with the voltage value VL divided by the fixed resistors R5 and R6. VL is set so that the voltage output b does not fall even when the temperature compensation thermistor is at the maximum temperature in the normal use state. The thermistor element for temperature compensation has a resistance value of 7 kΩ even at 180 ° C., for example, and the resistance element R1 is set to 33 kΩ, so that R3 = 33 kΩ and R4 = 5.6 kΩ. In the normal use state, the output n of the comparator 15 is “L”. On the other hand, when the temperature compensation thermistor is short-circuited and b = GND, the output n of the comparator 15 becomes “H”, and the microcomputer 16 reads the signal n at the input port so that the temperature compensation thermistor 11 or its transmission line is short-circuited. The heater 4 is turned off and the operation of the apparatus is stopped, and the display device displays that the temperature detecting element 5 has failed.
[0035]
In this embodiment, in order to prevent overheating, the infrared detection thermistor is disconnected and the temperature compensation thermistor is detected to be short-circuited. It is more effective if the disconnection of the compensation thermistor is detected.
[0036]
(Example 4)
Next, a “temperature detection apparatus” that is Embodiment 4 will be described with reference to FIG. The infrared detecting thermistor element 10 and the temperature compensating thermistor element 11 are connected in series with the 33 kΩ resistance elements R1 and R2, respectively, and connected between the reference power supply V and the ground. That is, the infrared detection thermistor element 10, the temperature compensation thermistor element 11, and the resistance elements R1 and R2 constitute a resistance bridge circuit, and a reference power supply voltage is applied to the resistance bridge circuit. Outputs of the infrared detection thermistor element 10 and the temperature compensation thermistor element 11 that are outputs of the resistance bridge circuit are voltages a and b, respectively. The differential amplifier circuit 17 receives the voltages a and b, and the output amplified 15 times is the voltage c. The voltages a, b, c are input to the 8-bit A / D converters 12, 13, 18, and the digital output j corresponding to the voltage a, the digital output n corresponding to the voltage b, and the digital output m corresponding to the voltage c are converted to the microcomputer 16. Read on. The microcomputer 16 applies j and m of these digital outputs to the data table, detects the temperature of the heating roller 2, energizes the heater 4 when the temperature is lower than the target temperature, and energizes when the temperature is higher than the target temperature. stop. In this embodiment, the temperature is detected by the digital outputs j and m. However, n can be used instead of the digital output j.
[0037]
At the same time, the microcomputer 16 determines whether the value of the digital value j is FFH in order to detect disconnection of the infrared detection thermistor. The thermistor element for infrared detection has a resistance value of 1000 kΩ even at 0 ° C., for example, and the resistance element R 1 is set to 33 kΩ, so that the digital output is low even at a low temperature of 0 ° C. F7H, and FFH will not occur except for disconnection. When the value of the digital value j is FFH, it is determined that the infrared detection thermistor 10 or its transmission line is disconnected, the heater 4 is turned off and the operation of the device is stopped, and the temperature of the display device is reduced. It displays that the detection element 5 has failed. Further, the microcomputer 16 determines whether the value of the digital value n is 30H or less in order to detect a short circuit of the temperature compensation thermistor. The temperature compensation thermistor element does not reach a high temperature of 180 ° C or higher under normal use conditions, and it can be determined that the thermistor element or the transmission line ground is short-circuited abnormally because the digital value is 30H or less. Then, the energization of the heater 4 is stopped and the operation of the apparatus is stopped, and the display device displays that the temperature detecting element 5 has failed.
[0038]
In this embodiment, in order to prevent an excessive temperature rise, a disconnection of the infrared detection thermistor and a short circuit of the temperature compensation thermistor are detected. However, when the digital value j is 30H or less, the infrared detection thermistor It is more effective if it is determined that the temperature compensation thermistor is disconnected when the digital value n is FFH.
[0039]
【The invention's effect】
  As explained above, according to the present invention,The resistance changes according to the temperature of the heater that heats the heating object, the first temperature detection element whose resistance changes according to the temperature of the film that absorbs infrared rays from the heating object, and the holding body that holds the film. A second temperature sensing element for temperature compensation, a first voltage which is a voltage at a connection point between the first temperature sensing element and the first resistance element, the second temperature sensing element and the second temperature sensing element. Control means for detecting the temperature of the object to be heated based on a second voltage that is a voltage at a connection point of the resistance element, and controlling energization to the heater, wherein the control means includes the first voltage When the voltage is a voltage indicating a disconnection of the first temperature detection element, and when the second voltage is a voltage indicating a short circuit of the second temperature detection element, the energization to the heater is stopped. The heating target at the time of failure of the first and second temperature sensing elements Thereby preventing the Atsushi Nobori in advance.
[Brief description of the drawings]
FIG. 1 is a diagram showing a main configuration of a first embodiment.
FIG. 2 is a diagram showing a main configuration of a second embodiment.
FIG. 3 is a diagram showing a configuration of main parts of a third embodiment.
FIG. 4 is a diagram showing a main configuration of a fourth embodiment.
FIG. 5 is a cross-sectional view showing a configuration of a fixing unit.
FIG. 6 is a cross-sectional view showing details of a temperature detecting element.
FIG. 7 is an explanatory diagram of a conventional example.
[Explanation of symbols]
7 cases
9 Heat resistant film
10 Thermistor element for infrared detection
11 Thermistor element for temperature compensation
16 Microcomputer
R1, R2 resistance

Claims

A heater for heating an object to be heated;
A film that absorbs infrared rays from the heating object;
A first temperature sensing element whose resistance changes according to the temperature of the film;
A second temperature sensing element for temperature compensation whose resistance changes according to the temperature of the holding body for holding the film;
Parallel connection first series circuit connected said first temperature sensing element and the first resistive element in series, and a second series circuit connected in series with said second temperature sensing element and the second resistive element in the resistance bridge circuit, said first temperature sensing element and the first and the first voltage contact a voltage of connection point of the resistance element, before Symbol said second temperature sensing element and the second resistive element tangent detecting the temperature of the heating target based on the second voltage is the voltage of the connection point, and a control means for controlling the energization of the heater,
Wherein if the first voltage is a voltage indicating the disconnection of the first temperature sensing element, and, when the second voltage is a voltage indicating a short circuit of the second temperature sensing element, A heater control device that stops energization of the heater .

The heater control device according to claim 1, wherein
The control means displays when the first voltage is a voltage indicating a disconnection of the first temperature detection element, and when the second voltage is a voltage indicating a short circuit of the second temperature detection element. A heater control device characterized by causing a means to display a failure .

A heater for heating an object to be heated;
A film that absorbs infrared rays from the heating object;
A first temperature sensing element whose resistance changes according to the temperature of the film;
A second temperature sensing element for temperature compensation whose resistance changes according to the temperature of the holding body for holding the film ;
Parallel connection first series circuit connected said first temperature sensing element and the first resistive element in series, and a second series circuit connected in series with said second temperature sensing element and the second resistive element in the resistance bridge circuit, connection of the first temperature sensing element and the first voltage is a voltage of the connection point of the first resistance element, the second temperature sensing element and the second resistive element converting the second voltage is a voltage of the point into a digital value, to detect the temperature of the heating object on the basis of these two digital values, and control means for controlling the energization of the heater, the Have
The control means is configured such that the digital value converted from the first voltage is a value indicating the disconnection of the first temperature detection element, and the digital value converted from the second voltage is the second value. If a value indicating a short circuit of the temperature sensing element, a heater control apparatus characterized by stopping the energization of the heater.

In the heater control device according to claim 3,
The control means is configured such that the digital value converted from the first voltage is a value indicating the disconnection of the first temperature detection element, and the digital value converted from the second voltage is the second value. In the case of a value indicating a short circuit of the temperature detection element, a heater control device that causes the display means to perform a failure display .

A heater for heating an object to be heated;
A film that absorbs infrared rays from the heating object;
A first temperature sensing element whose resistance changes according to the temperature of the film;
A second temperature sensing element for temperature compensation whose resistance changes according to the temperature of the holding body for holding the film ;
Parallel connection first series circuit connected said first temperature sensing element and the first resistive element in series, and a second series circuit connected in series with said second temperature sensing element and the second resistive element in the resistance bridge circuit, connection of the first temperature sensing element and the first voltage is a voltage of the connection point of the first resistance element, the second temperature sensing element and the second resistive element a second voltage which is the voltage of the point, of the first voltage and said a differential voltage between the second voltage third voltage, said first voltage or said second the temperature of the heating target is detected and and a control means for controlling the energization of the heater based on the said a voltage third voltage,
Wherein if the first voltage is a voltage indicating the disconnection of the first temperature sensing element, and, when the second voltage is a voltage indicating a short circuit of the second temperature sensing element, A heater control device that stops energization of the heater .

In the heater control device according to claim 5 ,
The control means displays when the first voltage is a voltage indicating a disconnection of the first temperature detection element, and when the second voltage is a voltage indicating a short circuit of the second temperature detection element. A heater control device characterized by causing a means to display a failure .

A heater for heating an object to be heated;
A film that absorbs infrared rays from the heating object;
A first temperature sensing element whose resistance changes according to the temperature of the film;
A second temperature sensing element for temperature compensation whose resistance changes according to the temperature of the holding body for holding the film ;
Parallel connection first series circuit connected said first temperature sensing element and the first resistive element in series, and a second series circuit connected in series with said second temperature sensing element and the second resistive element in the resistance bridge circuit, connection of the first temperature sensing element and the first voltage is a voltage of the connection point of the first resistance element, the second temperature sensing element and the second resistive element a second voltage which is the voltage of the point, of the first voltage and the second is a differential voltage between the voltage of the third voltage, a first voltage or a second voltage When the third voltage into digital values, and detects the temperature of the heating object on the basis of these two digital values, and a control means for controlling the energization of the heater,
The control means is configured such that the digital value converted from the first voltage is a value indicating the disconnection of the first temperature detection element, and the digital value converted from the second voltage is the second value. If a value indicating a short circuit of the temperature sensing element, a heater control apparatus characterized by stopping the energization of the heater.

In the heater control device according to claim 7 ,
The control means is configured such that the digital value converted from the first voltage is a value indicating the disconnection of the first temperature detection element, and the digital value converted from the second voltage is the second value. In the case of a value indicating a short circuit of the temperature detection element, a heater control device that causes the display means to perform a failure display .