JP2005017762A

JP2005017762A - Fixing device and image forming apparatus

Info

Publication number: JP2005017762A
Application number: JP2003183243A
Authority: JP
Inventors: Hiroyuki Kunii; 博之国井; Hisashi Kikuchi; 尚志菊地; Takashi Fujita; 貴史藤田; Katsuhiro Echigo; 勝博越後; Satohiko Baba; 聡彦馬場; Shigeo Kurotaka; 重夫黒高; Atsushi Nakato; 淳中藤; Yukimichi Someya; 幸道染矢
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2003-06-26
Filing date: 2003-06-26
Publication date: 2005-01-20
Anticipated expiration: 2023-06-26
Also published as: JP4255760B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device whose rise time is short while preventing the hot offset of toner, the rupture of a fixing member and the occurrence of wrinkles and irregular gloss or the like by efficiently easily discharging the heat of the fixing member and restraining temperature rise. <P>SOLUTION: In the fixing device for fixing an image by making recording material P to which a toner image is transferred pass through a nip part N formed by the fixing member 2 heated by a heating means 5 and a pressure member 14 press-contacting with the member 2, the member 2 includes a low temperature part in an inner part than the highest temperature part and is set so that heat resistance from the highest temperature part to the low temperature part may be different in the longitudinal direction of the fixing member. The heat resistance is the one going toward the center of rotation, is different between the center part 2c and the ends 2a and 2b of the member 2 in the longitudinal direction, and is made smaller at the ends 2a and 2b than at the center part 2c. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、加熱手段で加熱される定着部材を有する定着装置、及びこの定着装置を備えた複写機、プリンタ、ファクシミリやこれらの複合機等の画像形成装置に関する。
【０００２】
【従来の技術】
複写機、プリンタ、ファクシミリ或いはこれらの少なくとも１つの機能を備えた複合機等として構成される電子写真方式の画像形成装置には、定着装置が装着されている。定着装置は、加熱手段により加熱される定着部材と、定着部材と圧接する加圧部材とを備え、トナー画像が転写されている記録材を、定着部材と加圧部材とにより形成されるニップ部を通過させることでトナー画像を記録材上に定着する方式が一般的に採用されている。定着部材は金属製の芯金上に弾性層及び離型層を積層されていて、熱容量が比較的大きいため、室温から設定温度まで加熱するのに掛かる立ち上がり時間は長くなる。
【０００３】
定着部材に対する加熱方式としては、定着部材の内部にハロゲンヒータ等の加熱手段を設けて内部から加熱する場合や、定着部材の外部に加熱手段を設けて外部から加熱する場合がある。内部から定着部材を加熱する定着装置としては特許文献１があり、外部から定着部材を加熱する定着装置としては、特許文献２が挙げられる。
【０００４】
【特許文献１】
特開平１１−１８４２９１号公報
【特許文献２】
特開２００２−４０８５５号公報
【０００５】
【発明が解決しようとする課題】
定着部材は、一般に記録材の幅よりも長手方向へ長さ形成されているので、定着部材の長さよりも小さいサイズの記録材を連続的に通紙定着を行うと、非通紙部分の温度が上がり、破壊されることがある。また、小さいサイズの用紙を連続的に通紙した直後に大きいサイズの用紙を定着させようとした際には、非通紙部分が通紙部分よりも高温になっているため、定着部材に温度ムラが発生し、シワや光沢ムラ、さらにはホットオフセット等の不具合が発生することがあった。また、特許文献１のように定着部材の内部から加熱する場合には、外部から定着部材を材加熱する場合よりも室温から設定温度まで加熱するのに掛かる立ち上がり時間は長くなる。
本発明は、定着部材の熱を効率よく逃がし易くして温度上昇を抑え、トナーのホットオフセット等や、定着部材の破壊、シワや光沢ムラ等の発生を防止しつつ、立ち上がり時間の短い定着装置、及び画像形成装置を提供することを目的とする。
【０００６】
【課題を解決するための手段】
上記目的を設定するため、請求項１の発明は、加熱手段により加熱される定着部材と、定着部材と圧接する加圧部材とを備え、トナー画像が転写されている記録材を、定着部材と加圧部材とにより形成されるニップ部を通過させることで定着を行う定着装置において、定着部材は、最高温度部分よりも内部に低温部分を含み、最高温度部分から低温部分への熱抵抗が、定着部材の長手方向で異なることを特徴としている。
【０００７】
請求項２の発明は、請求項１記載の定着装置において、定着部材は、その回転中心方向への熱抵抗が、長手方向の中央部と端部とで異なり、中央部よりも端部の熱抵抗が小さいことを特徴としている。
【０００８】
請求項３の発明は、請求項１または２記載の定着装置において、定着部材は、金属性の芯金上に形成した断熱層を有することを特徴としている。
【０００９】
請求項４の発明は、加熱手段により加熱される定着部材と、定着部材と圧接する加圧部材とを備え、トナー画像が転写されている記録材を、定着部材と加圧部材とにより形成されるニップ部を通過させることで定着を行う定着装置において、定着部材は、最高温度部分よりも内部に断熱層及び低温部分を含み、断熱層の表面側と内面側との間の温度差が、定着部材の長手方向で異なることを特徴としている。
【００１０】
請求項５の発明は、請求項１ないし４の何れかに記載の定着装置において、定着部材は、最高温度部分よりも内部に空洞を含み、この空洞内に熱を定着部材外部へ逃がす熱移動部を有することを特徴としている。
【００１１】
請求項６の発明は、加熱手段により加熱される定着部材と、定着部材と圧接する圧部材とを備え、トナー画像が転写されている記録材を、定着部材と加圧部材とにより形成されるニップ部を通過させることで定着を行う定着装置において、定着部材は、最高温度部分よりも内部に空洞を含み、この空洞内における放熱量が定着部材の長手方向で異なることを特徴としている。
【００１２】
請求項７の発明は、請求項６記載の定着装置において、定着部材は、金属性の芯金と、芯金の厚みが所定の厚みよりも薄い部分の空洞内部の表面に設けた断熱部材とを有することを特徴としている。
【００１３】
請求項８の発明は、請求項６または７記載の定着装置において、空洞内の表面積が、長手方向において中央部よりも端部の方で大きいことを特徴としている。
【００１４】
請求項９の発明は、請求項６、７または８記載の定着装置において、空洞内に熱を定着部材外部へ逃がす熱移動部を有することを特徴としている。請求項１０の発明は、請求項５または９記載の定着装置において、熱移動部が、空洞と定着部材の外部とを連通する開口であることを特徴としている。請求項１１の発明は、請求項１０記載の定着装置において、空洞内の熱を開口から外部へ強制的に移動させるファンを有することを特徴としている。
【００１５】
請求項１２の発明は、請求項１１記載の定着装置において、用紙サイズを検出する用紙サイズ検出手段によって検出した用紙サイズと、用紙の通紙枚数を計数する通紙枚数計数手段によって計数した通紙枚数とに基づいて、ファンの駆動状態を変更制御する制御部を有することを特徴としている。
【００１６】
請求項１３の発明は、請求項１１記載の定着装置において、空洞内部の端部の温度を検知する第１の温度検知手段と、空洞内部の中央部の温度を検知する第２の温度検知手段とを有し、第１及び第２の温度検知手段で検出された温度情報の差に基づいてファンの駆動状態を変更制御する制御部を有することを特徴としている。
【００１７】
請求項１４の発明は、像担持体と、この像担持体に形成されるトナー像を記録材に転写する転写手段と、記録材に転写されたトナー画を記録材に定着する定着装置とを備えた画像形成装置において、定着装置として、請求項１ないし１３の何れかに記載の定着装置を用いたことを特徴としている。
【００１８】
【発明の実施の形態】
発明の背景
定着装置において、定着部材の温度の立ち上がり時間を短縮することは省エネのために重要である。芯金や弾性層を薄肉化することで装置を低熱容量にでき、立ち上がり時間を短縮することは可能である。これにより立ち上がり時間はかなり短縮できるが、加熱手段が内部にある場合には、定着部材の内面から表面まで熱伝導で熱が伝わるのに時間のロスがある。特に十分な厚さの弾性層が必要なカラー画像に対応する定着装置においては、この時間のロスは大きい。このため立ち上がり時間の遅れや、通紙時の定着部材の温度低下からの復帰に時間が掛かり、連続通紙時に定着部材の温度が下がるので定着性が悪くなるなどの問題がある。
【００１９】
この対策として特許文献２の記載のように、定着部材の表面側に加熱手段を配置し、定着部材表面を直接加熱する外部加熱方式が提案されている。外部加熱方式では、加熱が必要な表層のみを加熱しているので、立ち上がり時間は非常に速く、また通紙時の温度低下からの復帰のレスポンスも良い。しかし実際の表層の熱は、加熱が不要な部材内部や加圧部材等に逃げて行くため、表層のみの加熱の理論値よりは立ち上がり時間は遅くなる。
【００２０】
このため表層の下には断熱層が設けられ、この断熱性を向上させることで立ち上がり時間を短縮することを図っている。断熱性の良い部材としては、熱伝導率の低い空気などの気体を内部に含んだ部材が一般的で、例えば、特開２０００−２０６８１５号公報では、発泡シリコーンゴムが良く使用されている。発泡シリコーンは空気を含むため熱伝導率が低く、断熱性は良いが、ニップ部内では圧縮されて空気含有率が小さくなり、熱伝導率が大きくなってしまう。また、圧縮変形するので高面圧が掛けられないことや、変形の繰り返しにより経時で劣化する等の問題がある。更に圧縮により回転半径が変化するので記録材等を一定速度で搬送する駆動側部材としては不向きであるという欠点がある。剛性が高く、変形の小さい断熱材としては、特開２００２−４０８５５号公報に記載の多孔質セラミックスや、特開２０００−２７５９９６号公報に記載の多孔質樹脂や中空粒子をバインダーに混合したものが挙げられる。
【００２１】
このような背景を踏まえ、本発明にかかる定着装置や画像形成装置の構成や作用を説明すると、請求項１では、定着部材が最高温度部分よりも内部に低温部分を含み、最高温度部分から低温部分への熱抵抗が定着部材の長手方向で異なるようにしている。定着部材には、その長手方向において熱の伝わり易い部位と伝わりにくい部位とが形成されることになり、熱の伝わり易い部位では、温度上昇を抑えられることになる。このため、定着部材における温度ムラの発生が抑制され、温度ムラに起因するシワや光沢ムラ、さらにはホットオフセット等の不具合を防止できる。ここでいう熱抵抗を異ならせるとは、例えば定着部材を構成する断熱層を薄くすることである。ここでいう加熱の形態としては、定着部材を外側から加熱するものと、例えば芯金と断熱層の間に加熱部を設けた誘電加熱も含まれる。この場合、通紙基準位置は定められてはいない。
【００２２】
請求項２では、定着部材は、その回転中心方向への熱抵抗が、長手方向の中央部と端部とで異なり、中央部よりも端部の熱抵抗が小さくされている。これにより、非通紙部となる端部側での熱が逃げやすくなり、端部の昇温を防できる。この場合、加熱が定着基部の外側であれば、最高温度部分は定着部材の外側となり、温度の立ち上げ時間が短く、記録材への熱供給効率が高くなる。この場合、通紙基準位置は定着部材の中央となる。請求項３では、定着部材が、金属性の芯金上に形成した断熱層を有することを特定している。
【００２３】
請求項４では、定着部材が、最高温度部分よりも内部に断熱層及び低温部分を含み、断熱層の表面側と内面側との間の温度差が定着部材の長手方向で異なるように設けている。これは、断熱層の断熱率が異なるようにしたもので、非通紙部分となる定着部材の端部の断熱率を低くすることで、熱が逃げやすくなり、温度上昇を抑えられる。このため、定着部材における温度ムラの発生が抑制され、温度ムラに起因するシワや光沢ムラ、さらにはホットオフセット等の不具合を防止できる。
【００２４】
請求項５では、定着部材は、最高温度部分よりも内部に空洞を含み、この空洞内に熱を定着部材外部へ逃がす熱移動部を設けている。これは、定着部材を加熱すると、時間の経過とともに、その内部の温度は上昇する。特に芯金が金属の場合、非通紙部の温度が上昇すると、その熱が芯金に伝熱することで芯金自体の温度が上昇する。
したがって、熱移動部を設けることで、定着部材の空洞内の熱を定着部材外部へ逃がすことができ、定着部材の内部が冷却され、内部温度の上昇を抑えられる。このため、定着部材における内部温度のムラの発生が抑制され、温度ムラに起因するシワや光沢ムラ、さらにはホットオフセット等の不具合を防止できる。
【００２５】
請求項６は、定着部材は、最高温度部分よりも内部に空洞を含み、この空洞内における放熱量が定着部材の長手方向で異なるようにしている。この場合、放熱量の高い部位の温度は逃げやすくなるので、非通紙部に相当する部位の内部における放熱量を大きくすることで、定着部材における内部温度のムラの発生が抑制され、温度ムラに起因するシワや光沢ムラ、さらにはホットオフセット等の不具合を防止できる。
【００２６】
請求項７は、定着部材の金属性の芯金を有する場合に、芯金の厚みが所定の厚みよりも薄い部分の空洞内部の表面に断熱部材を設けている。断熱部材を設けると、熱が空洞内部に伝わりにくくなるので、通紙部に相当する部位の芯金を薄くした場合、その内部に断熱部材を設けることで、通紙部に相当する部位の熱は逃げにくくなり、温度の立ち上がりを素早く行える。また、非通紙部に相当する部位の熱は断熱部材がないので、逃げ易くなり、温度上昇を抑えられる。
【００２７】
請求項８では、空洞内の表面積を長手方向において中央部よりも端部の方を大きくしている。すなわち、定着部材の空洞内部の長手方向の位置において、中央部よりも端部の冷却効率を上げている。このため、中央部よりも端部の温度の冷却効率が上がり、端部温度上昇を防止できる。
【００２８】
請求項９は、空洞内に熱を定着部材外部へ逃がす熱移動部を設けている。したがって、定着部材の空洞内の熱を定着部材外部へ逃がすことができ、定着部材の内部が冷却され、内部温度の上昇を抑えられる。このため、定着部材における内部温度のムラの発生が抑制され、温度ムラに起因するシワや光沢ムラ、さらにはホットオフセット等の不具合を防止できる。熱移動部としては、空洞と定着部材の外部とを連通する開口や、空洞と定着部材の外部とを連通するヒートパイプが挙げられる。
【００２９】
開口を設けた定着部材の場合、さらに、空洞内の熱を開口から外部へ強制的に移動させるファンを設けると、定着部材の内部の冷却効率が高まり、内部温度の上昇を抑えられ、定着部材における内部温度のムラの発生を抑制することができ、温度ムラによる不具合を防止することができる。
【００３０】
請求項１２は、用紙サイズを検出する用紙サイズ検出手段によって検出した用紙サイズと、用紙の通紙枚数を計数する通紙枚数計数手段によって計数した通紙枚数とに基づいて、ファンの駆動状態を変更制御する制御部を設けている。これは、転写材のサイズが大きい場合や、サイズが小さく枚数が少ない場合には端部昇温がほとんど起こらないため、ファンを駆動する必要性が薄くなるためである。したがって用紙サイズや通紙枚数から定着部材の端部温度が上昇度合いを推定し、必要のない場合には、ファンを停止状態とし、必要のある場合にはファンを駆動させることにより、消費電力を低減しながら、無駄のない冷却が可能となる。
【００３１】
請求項１３は、空洞内部の端部の温度を検知する第１の温度検知手段と、空洞内部の中央部の温度を検知する第２の温度検知手段とを設け、これら温度検知手段で検出された温度情報の差に基づいてファンの駆動状態を変更するようにしている。そもそも定着部材の長手方向において、温度差（温度ムラ）が発生することが問題となっている。また、温度差があっても許容範囲はあるので、定着部材内部の中央と端部の温度差が所定範囲の場合にはファンを停止状態とし、所定の温度以上の時にはファンを駆動させることにより、消費電力を低減しながら、無駄のない冷却が可能となる。
【００３２】
請求項１４は、画像形成装置に上述の定着装置を用いている。このような定着装置を用いることで、トナーのホットオフセット等や定着部材の破壊、シワや光沢ムラ等の発生を防止しつつ、立ち上がり時間が短かく、省電力な画像形成装置を達成することができる。
【００３３】
【実施例】
図１３に示す画像形成装置は、電子写真方式のフルカラーのプリンタの一形態である。このプリンタは、箱状の装置本体５００内に、像担持体となる複数の感光体ドラム５０４Ｙ，５０４Ｍ，５０４Ｃ，５０４ＢＫを備えた感光体ユニット５０２Ｙ，５０２Ｍ，５０２Ｃ，５０２ＢＫと、感光体ドラム５０４Ｙ，５０４Ｍ，５０４Ｃ，５０４ＢＫと対向配置され、転写材としての用紙Ｐを搬送する転写搬送体としての転写搬送ベルト５０３を有する転写ユニット５６０と、転写搬送ベルト５０３によって搬送される用紙Ｐに感光体ドラム５０４Ｙ，５０４Ｍ，５０４Ｃ，５０４ＢＫ上のトナー像を転写する転写手段としての転写ローラ５０１Ｙ，５０１Ｍ，５０１Ｃ，５０１ＢＫが設けられている。
【００３４】
転写搬送ベルト５０３は、その１つに回転駆動力が伝達される複数のローラに架け渡されて矢印Ａで示す方向に回転駆動可能に設けられている。転写搬送ベルト３は、各感光体ドラムの表面に圧接するように配設されている。各感光体ドラムとの対向側には、現像装置５０５Ｙ，５０５Ｍ，５０５Ｃ，５０５ＢＫがそれぞれ配置されている。各現像装置は、複数色、例えばイエロー（以下Ｙという）、マゼンタ（以下Ｍという）、シアン（以下Ｃという）、ブラック（以下Ｋという）の各トナーとキャリアとを有する２成分現像剤を、それぞれ感光体ドラム５０４Ｙ，５０４Ｍ，５０４Ｃ，５０４ＢＫ上に形成される静電潜像に供給して各静電潜像を現像するものである。
【００３５】
感光体ユニット５０２Ｙ，５０２Ｍ，５０２Ｃ，５０２Ｋの上方には露光手段としての書き込み装置５０６が配置され、感光体ユニット２Ｙ，２Ｍ，２Ｃ，２Ｋの下方には両面ユニット５０７が配置されている。両面ユニット７の下方には、サイズの異なる転写材Ｐが収納可能な給紙カセット５１３，５１４が配設されている。装置本体５００の左方には反転ユニット５０８が配置され、装置本体１の右側には手差しトレイ５１５が矢印Ｂ方向に開閉可能に設けられている。転写搬送ベルト５０３と反転ユニット５０８との間には定着装置５０９が配置されている。定着装置９の転写材搬送方向下流側には反転搬送路５１０が分岐して形成され、シート状の転写材Ｐを反転搬送路１０に配置された排紙ローラ５１１によって装置上部に設けられた排紙トレイ５１２に案内している。
【００３６】
各感光体ユニットは、各感光体ドラム上にＹ，Ｍ，Ｃ，ＢＫ各色に対応するのトナー像を形成するためのユニットである。各感光体ユニットには、各感光体ドラムの表面を均一に帯電する図示しない帯電装置、感光体ドラムの表面をブラシローラおよびクリーニングブレードでクリーニングするクリーニング装置とが設けられている。各感光体ユニットおよび各帯電装置は、装置本体１に配置される場所を除いては同一構成となっている。
【００３７】
書き込み装置５０６は、図示しないレーザ光源としてのレーザダイオードからのＹ画像データで変調されたＹ用レーザ光、Ｍ画像データにより変調されたＭ用レーザ光、Ｃ画像データにより変調されたＣ用レーザ光、ＢＫ画像データにより変調されたＢＫ用レーザ光とを、図示しないレンズ、ミラーを介して各感光体ドラムに照射して、ドラム表面に静電潜像を形成する。
【００３８】
両面ユニット５０７は、用紙Ｐの両面に画像を形成する両面画像形成モード時に、片面に画像が形成されてから反転ユニット５０８の反転搬送路５４４に搬送されてスイッチバック搬送されることで表裏が反転される用紙Ｐを受け入れ、これを各感光体ドラムと転写搬送ベルト５０３との間に形成される転写部へと再搬送する。
【００３９】
反転ユニット５０８は、複数の搬送ローラと、複数の搬送ガイド板とからなり、両面画像形成モード時に片面画像形成後の転写材を、その表裏を反転させて両面ユニット５０７へ送り出す機能や、画像形成後の転写材をそのままの向きで機外へ排出する機能、画像形成後の転写材を、その表裏を反転させて機外へ排出する機能を備えている。給紙カセット５１３，５１４が配置されている給紙部には、給紙カセット１３，１４上の用紙Ｐを１枚ずつに分離して給紙する分離給紙部５４５，５４６が設けられている。
【００４０】
本形態では、図示しない操作部により画像形成が指示されると、各感光体ドラムが図示しない駆動源により回転駆動されて時計回り方向に回転する。そして各帯電装置は、図示しない電源から帯電バイアスが印加されて各感光体ドラムをそれぞれ一様に帯電させる。一様に帯電された各感光体ドラムは、書き込み装置５０６にて、Ｙ，Ｍ，Ｃ，Ｋ各色の画像データで変調されたレーザ光により露光されて、各表面に静電潜像が形成される。これら感光体ドラム上の静電潜像は、ドラムの回転と、各現像装置が有する図示しない現像スリーブが図示しない駆動源で回転駆動されることにより現像されてＹ，Ｍ，Ｃ，Ｋ各色のトナー像となる。
【００４１】
給紙カセット５１３，５１４のうち、選択された方の給紙カセットからは、１枚の用紙Ｐが分離されて、感光体ユニット５０２Ｙよりも給紙部側に配設されたレジストローラ５５１へ給紙される。本形態では、装置本体５００の右方側部に手差しトレイ５１５が配置され、この手差しトレイ５１５からも用紙がレジストローラ５５１へ給紙可能とされている。レジストローラ５５１は、各用紙を各感光体ドラムのトナー像とその先端が一致するタイミングで転写搬送ベルト５０３上へ送り出す。送り出された用紙Ｐは、転写搬送ベルト５０３を巻き掛けている紙吸着ローラ５２によって帯電される転写搬送ベルト３に静電的に吸着されて各転写部へと搬送される。
【００４２】
搬送された用紙Ｐには、各転写部を順に通過する際に、図示しない電源から転写バイアスが供給された転写ローラ５０１Ｙ，５０１Ｍ，５０１Ｃ，５０１ＢＫを受けることで、各感光体ドラム上のＹ，Ｍ，Ｃ，Ｋ各色のトナー像が順次に重ね合わせて転写され、４色重ね合わせのフルカラートナー像が形成される。フルカラートナー像が形成された用紙Ｐは、定着装置５０９によりフルカラートナー像が定着され、その後は指定されたモードに応じた排紙路を通って排紙トレイ５１２に反転排出される場合や、定着装置５０９から直進して反転ユニット５０８内を通ってストレートに排紙される。
【００４３】
画像形成装置において、両面画像形成モードが選択されているときには、記録媒体Ｐは、片面にトナー像が形成されて定着装置５０９でトナー像が定着された後に、反転ユニット５０８内の反転搬送路５４４内に送り込まれ、ここでスイッチバックされてから両面ユニット５０７に搬送され、そこから再給送されて表面画像形成時と同様に裏面に画像が形成されて排出される。
【００４４】
以上の作像動作は、４色重ね合わせのフルカラーモードが図示しない操作部で選択されたときの動作であるが、３色重ね合わせのフルカラーモードが操作部で選択されたときにはＫトナー像の形成が省略されてＹ，Ｍ，Ｃ３色のトナー像の重ね合わせによるフルカラー画像が用紙Ｐ上に形成される。また、白黒画像形成モードが操作部で選択されたときには、Ｋトナー像の形成のみが行われて白黒画像が用紙Ｐ上に形成される。
（実施例１）
図１は、本発明を適用したの定着装置５０９の概略構成図である。ここに示す定着装置５０９は、定着部材としてのローラ形状である定着部材２と、この定着部材２にバネ１５によって加圧したローラ形状の加圧部材１４とを有し、これらの部材が互いに圧接することによりニップ部Ｎを形成している。加圧部材１４は図示しない駆動モータにより駆動されて回転し、その駆動力を定着部材２に伝えて従動回転させている。定着部材２の外部には、加熱手段としてハロゲンヒータ５と反射板６とが設置されている。反射板６は、ヒータの熱を定着部材２に向かって反射するものである。定着部材２の表面２ａは、ハロゲンヒータ５からの輻射熱や反射板６で反射される輻射熱によって設定温度になるように制御されている。定着動作としては、未定着トナーが付着した用紙Ｐが定着部材２および加圧部材１４の中央部を基準として狭持搬送されながら加熱加圧されて定着される。
【００４５】
定着部材２は外形３０ｍｍで用紙幅方向に延びるローラ形状で、図４に示すように、金属製で筒状の芯金４と、芯金４の周囲に中空糸を何層も巻きつけて形成された断熱層３とから構成されている。つまり、定着部材２は、その内部に空洞４ａを備えている。中空糸としてはポリエステル、ポリイミド、ポリアミドイミド、ポリベンゾイミダゾール、ポリベンゾビスオキサゾール、ポリフェニレンサルファイド、ガラス、セラミックス、金属などの中空構造が挙げられる。断熱効果を高くするという点では材料を限定するものではないが、本例では、耐熱性、材料自体の熱伝導率、強度を考慮してポリイミド中空糸を採用している。ポリイミド中空糸は、外計２３０μｍ、内計１５０μｍであり、この中空糸を密に巻き付けることで高い断熱性と剛性を備える。定着部材２の表層近傍には、図２（ａ）に示すように弾性層１２として０．１ｍｍ厚のシリコーンゴム層があり、表層には離型層１３として１５μｍ厚のＰＦＡチューブが被服してある。
【００４６】
加圧部材１４は外経３０ｍｍで、用紙幅方向に延びるローラ形状で、図２（ｂ）に示すように中空糸を金属製の芯金４上に約２ｍｍの層になるよう巻き付けて構成されている。中空糸層１６の上には弾性層として１ｍｍのシリコーンゴム層１７が形成され、表層は離型層１８として１５μｍのＰＦＡチューブが被覆してある。このような構成で、定着部材２と加圧部材１４を面圧２ｋｇ／ｃｍ^２になるように圧接した場合において、中空糸層はほとんど変形せず、均一なニップ部Ｎを形成できる。
【００４７】
これら定着部材２及び加圧部材１４の矢印Ｃで示す長手方向（用紙幅方向）への長さは、通常使用する用紙Ｐの幅よりも長く形成されている。定着部材２の両端は、開口されていて、空洞４ａ内に熱を定着部材外部へ逃がす熱移動部１２，１３を構成している。
【００４８】
次に動作を説明すると、図３のような従来の定着部材を用いた場合、例えば通常サイズの用紙Ｐが通紙可能な定着装置において、通常サイズよりも小さい用紙Ｐを連続的に通紙した場合には、通紙領域では用紙およびトナーに熱を奪われた後、再加熱されるので温度はほぼ一定になる。しかし、非通紙領域は用紙Ｐによって熱を奪われず、加熱されっぱなしになるため、高温になり、断熱層や弾性層の劣化や、小サイズの用紙の連続通紙後に通常サイズの用紙を通紙した際には非通紙部が高温になっているためトナーのホットオフセットや用紙のシワ等が発生してしまう。
【００４９】
本発明にかかる定着部材２は、図４に示したように、小サイズの用紙を通紙した際の非通紙部となる定着部材２の端部２ａ、２ｂ側に位置する弾性層３の厚みを通紙部である中央部２ｃよりも小さくし、定着部材２の表層から芯金４への熱抵抗を端部２ａ、２ｂと中央部２ｃとで異ならせている。すなわち断熱層３の表面側３ａと内面側３ｂとの間の温度差が、定着部材２の長手方向で異なっている。断熱層３には高剛性の中空糸を用いているため、断熱層３の剛性が高く、断熱層３の厚みを変えても加圧による変形量はほとんど変わらず、ニップ部Ｎの用紙搬送方向への幅のバラツキは小さい。定着部材２の表層は、図１に示すハロゲンヒータ５の輻射熱により加熱され、断熱層３により表層に熱が保持される。この状態で、通紙を行うと表層の熱が通紙された用紙Ｐ及びトナーＴに移動して定着される。このように表層の熱は用紙Ｐおよびトナーに奪われ、ハロゲンヒータ５の輻射により再加熱され、これを繰り返すことで連続的に定着できる。
【００５０】
このように短時間の加熱定着のスパンであれば表層の熱はすぐに用紙ＰおよびトナーＴに奪われてほとんど定着部材２の内部には伝導しない。しかし、小サイズ紙の連続定着動作のように比較的長時間で通紙部と非通紙部がある場合では、定着部材２の非通紙部表層と芯金４の部分の温度勾配（温度差）が大きくなり、非通紙部表層の熱が芯金４に伝導されるようになる。特に、非通紙領域の断熱層３は中央部よりも薄いため、表層の熱は中央部よりも速く芯金４に伝導し、非通紙領域の表層の温度上昇を抑えることができる。さらに、芯金４の厚みが中央部２ｃよりも端部２ａ、２ｂ側の方が厚いので、熱容量が大きく、温度が飽和しにくい。このため、非通紙領域の表層の温度上昇を長時間抑え、通紙部と非通紙部の温度差を小さく保つことでトナーＴのホットオフセットや、定着部材２の破壊、またシワや光沢ムラ等の発生を防止できる。また、空洞４ａ内に熱は定着部材外部へ熱移動部１２，１３から逃げるので定着部材２の内部温度の上昇を低減することができる。ここでは、例えば、通常サイズがＡ３サイズ紙、小サイズ紙がＡ４サイズというような定型サイズを想定して説明しているが、これら用紙サイズを限定するものではなく、図５のように定型用紙サイズの種類に対応するように段階的に断熱層３の厚さを変化させた場合や図６のように連続的に断熱層３の厚さを変化させた構成でも良い。本例において定着部材２の最高温度部分とは、広義には表層全体となり、狭義には非通紙部に位置する端部表層となる。低温部分とは、広義には空洞４ａの表面全体であり、狭義には中央部２ｃに位置する空洞４ａの表面となる。
（実施例２）
図７に示す定着部材２は、実施例１と略同様の構成であり、定着部材２の熱移動部１２，１３である端部の開口近傍にファン８を設け、定着部材２の内部の芯金４を冷却するようにしたものである。本例ではファン８により定着部材２の空洞４ａ内に空気を送風している。このため、芯金４の温度が飽和しにくくなり、より非通紙領域の表層の温度上昇を長時間抑え、通紙部と非通紙部の温度差を小さく保つことができ、トナーのホットオフセットや、定着部材の破壊、またシワや光沢ムラ等の発生を防止できる。本例ではファン８により定着部材２の空洞４ａ内に空気を送風しているが、ファン８で空洞４ａ内の空気を吸引して熱を逃がすようにしても良い。
（実施例３）
図８に示す定着部材２は、実施例２と略同様の構成であり、芯金４の表面積を中央部よりも端部の方を大きくするようにした。芯金４の表面を機械的に荒らして凹凸を設けるか、また、フィン形状にすることで表面積が増え、請求項２の場合よりも効率的に冷却できる。また、図９に示すように断熱層３の厚みに対応して、例えば中央部２ｃから端部２ａ、２ｂに渡って表面積を段階的もしくは連続的に表面積を変えるようにしても良い。このように構成することで、非通紙領域の表層の温度上昇を長時間抑え、通紙部と非通紙部の温度差を小さく保つことでトナーのホットオフセットや、定着部材の破壊、またシワや光沢ムラ等の発生を防止できる。
（実施例４）
図１０に示す定着部材２は、実施例２と略同様の構成であり、芯金４の中央部４ｂのみに発泡シリコーン製の断熱シート９を設けたものである。このように断熱シート９を配設すると、中央部２ｃの温度の低下を防ぎつつ端部２ａ、２ｂのみを冷却できるため、非通紙部の温度上昇部分のみを冷却することができる。
（実施例５）
本例は、用紙サイズを検出する用紙サイズ検出手段としての用紙サイズセンサ１９によって検出した用紙サイズと、用紙Ｐの通紙枚数を計数する通紙枚数計数手段としての通紙枚数計測器２０によって計数した通紙枚数とに基づいて、ファン８の駆動状態を制御部としてのコントローラ１０で変更制御するものである。
【００５１】
コントローラ１０は、周知のコンピュータで構成されていて、通紙が始まると、用紙サイズセンサ１９からの用紙サイズ情報を取り込み、用紙サイズが通常のサイズか小サイズかを判断するとともに、通紙枚数計測器２０で計数した通紙枚数情報を取り込む。そして、用紙サイズが通常サイズの場合は通紙枚数に関わらずファン８を駆動しない。また、用紙Ｐが小サイズであると判断した、且つ通紙枚数が所定枚数以上となると、ファン８を駆動して定着部材２の芯金４を冷却する。このように用紙サイズや通紙枚数によってファン８の駆動を切換制御することで、省電力化を図れると共に、無駄な冷却動作を行わずに済む。
（実施例６）
本例は、図１２に示すように、空洞４ａ内部の端部４ｃの温度を検知する第１の温度検知手段となる温度センサ１１ａと、空洞４ａ内部の中央部４ｂの温度を検知する第２の温度検知手段となる温度センサ１１ｂとを設けるとともに、これら温度センサ１１ａ、１１ｂで検出された温度情報の差に基づいてファン８の駆動状態を制御部となるコントローラ１４で変更制御するものである。
【００５２】
コントローラ１４は、周知のコンピュータで構成されていて、温度センサ１１ａ、１１ｂからの温度情報の差が所定温度差以上になった場合に、定着部材２の路端部温度上昇が発生している見做し、ファン８を駆動する。このように空洞４ａ内の端部４ｃと中央部４ｂの温度差が所定温度差以上となる場合だけ、ファン８を駆動するので、省電力化を図れると共に無駄な冷却動作を行わずに済む。
【００５３】
各実施例に通紙部とは、用紙Ｐが当する定着部材２幅を指し、非通紙部とは用紙Ｐの幅よりも外側に位置する端部２ａ、２ｂを指す。上記各実施例において、定着部材２はローラ形状の構成で説明したが、図１４、図１５に示すように定着部材２とテンションローラ１７に定着ベルト１６を張架した形態の定着装置についても適応できる。定着ベルト１６を用いる場合には、ハロゲンヒータ５でベルトを加熱すればよい。なお、図１５に示す定着部材２は、断面扇形状でって、固定状態とされていて、定着ベルト１６が摺接するようになっている。
【００５４】
【発明の効果】
本発明によれば、定着部材には、その長手方向において熱の伝わり易い部位と伝わりにくい部位とが形成されることになり、熱の伝わり易い部位では温度上昇を抑えられることになるので、定着部材における温度ムラの発生が抑制され、温度ムラに起因するシワや光沢ムラ、さらにはホットオフセット等の不具合を防止できる。
【００５５】
本発明によれば、断熱層の断熱率が異なるようにしたもので、非通紙部分となる定着部材の端部の断熱率を低くすることで、熱が逃げやすくなって温度上昇が抑えられため、定着部材における温度ムラの発生が抑制され、温度ムラに起因するシワや光沢ムラ、さらにはホットオフセット等の不具合を防止できる。
本発明によれば、定着部材の空洞内における放熱量が定着部材の長手方向で異ならせることで、放熱量の高い部位の温度は逃げやすくなるので、非通紙部に相当する部位の内部における放熱量を大きくすることで、定着部材における内部温度のムラの発生が抑制され、温度ムラに起因するシワや光沢ムラ、さらにはホットオフセット等の不具合を防止できる。
【図面の簡単な説明】
【図１】本発明が適用された定着装置の概略構成図である。
【図２】（ａ）は定着部材の部分拡大断面図、（ｂ）は加圧部材の部分拡大断面図である。
【図３】従来の定着部材の構成を示す概略断面図である。
【図４】本発明の実施例１に示す定着装置における定着部材の概略断面図である。
【図５】本発明の実施例１に示す定着装置における別の定着部材の概略断面図である。
【図６】本発明の実施例１に示す定着装置における別の定着部材の概略断面図である。
【図７】本発明の実施例２に示す定着装置における定着部材の概略断面図である。
【図８】本発明の実施例３に示す定着装置における定着部材の概略断面図である。
【図９】本発明の実施例３に示す定着装置における別の定着部材の概略断面図である。
【図１０】本発明の実施例４に示す定着装置における定着部材の概略断面図である。
【図１１】本発明の実施例５に示す定着装置における定着部材とその制御系を示す概略構成図である。
【図１２】本発明の実施例６に示す定着装置における定着部材とその制御系を示す概略構成図である。
【図１３】本発明の定着装置を搭載する画像記録装置の概略構成図である。
【図１４】本発明を適用したベルト状の定着部材を用いた定着装置の概略構成図である。
【図１５】本発明を適用したベルト状の定着部材を用いた別な定着装置の概略構成図である。
【符号の説明】
２定着部材
２ａ、２ｂ長手方向の端部
２ｃ長手方向の中央部
３断熱層
３ａ断熱層の表面側
３ｂ断熱層の内面側
４芯金
４ａ空洞
４ｂ空洞の中央部
４ｃ空洞の端部
５加熱手段
８ファン
９断熱部材
１０、１４制御部
１１ａ第１の温度検知手段
１１ｂ第２の温度検知手段
１２，１３熱移動部
１４加圧部材
１９用紙サイズ検出手段
２０通紙枚数計数手段
５０４Ｙ，５０４Ｍ，５０４Ｃ，５０４ＢＫ像担持体
５０９定着装置
５６０転写手段
Ｔトナー画像
Ｐ記録材
Ｎニップ部
Ｃ定着部材の長手方向[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device having a fixing member heated by a heating means, and an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine including the fixing device.
[0002]
[Prior art]
A fixing device is mounted on an electrophotographic image forming apparatus configured as a copying machine, a printer, a facsimile, or a multifunction machine having at least one of these functions. The fixing device includes a fixing member heated by a heating unit, and a pressure member in pressure contact with the fixing member, and a recording material on which a toner image is transferred is formed in a nip portion formed by the fixing member and the pressure member. In general, a method of fixing a toner image on a recording material by passing the toner is used. Since the fixing member has an elastic layer and a release layer laminated on a metal core and has a relatively large heat capacity, the rise time required for heating from room temperature to a set temperature becomes long.
[0003]
As a heating method for the fixing member, there are a case where heating means such as a halogen heater is provided inside the fixing member and heating is performed from inside, or a case where heating means is provided outside the fixing member and heating is performed from outside. As a fixing device that heats the fixing member from the inside, there is Patent Document 1, and as a fixing device that heats the fixing member from the outside, Patent Document 2 can be cited.
[0004]
[Patent Document 1]
JP 11-184291 A
[Patent Document 2]
JP 2002-40855 A
[0005]
[Problems to be solved by the invention]
Since the fixing member is generally formed longer in the longitudinal direction than the width of the recording material, if the recording material having a size smaller than the length of the fixing member is continuously fixed, the temperature of the non-sheet passing portion is determined. May go up and be destroyed. In addition, when trying to fix a large size sheet immediately after passing a small size sheet continuously, the non-sheet passing part is hotter than the sheet passing part. Unevenness may occur, causing problems such as wrinkles, uneven glossiness, and hot offset. Further, when heating from the inside of the fixing member as in Patent Document 1, the rise time required for heating from the room temperature to the set temperature becomes longer than when the fixing member is heated from the outside.
The present invention relates to a fixing device having a short rise time while preventing the heat of the fixing member from being efficiently released to suppress the temperature rise and preventing the occurrence of hot offset of the toner, the destruction of the fixing member, wrinkles, uneven gloss, and the like. And an image forming apparatus.
[0006]
[Means for Solving the Problems]
In order to set the above object, the invention of claim 1 provides a fixing member heated by a heating means and a pressure member in pressure contact with the fixing member, and a recording material onto which a toner image is transferred, and a fixing member. In a fixing device that performs fixing by passing through a nip formed by a pressure member, the fixing member includes a low temperature portion inside the highest temperature portion, and the thermal resistance from the highest temperature portion to the low temperature portion is It is different in the longitudinal direction of the fixing member.
[0007]
According to a second aspect of the present invention, in the fixing device according to the first aspect, the fixing member has different heat resistance in the direction of the rotation center between the central part and the end part in the longitudinal direction, and the heat at the end part rather than the central part. It is characterized by low resistance.
[0008]
According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the fixing member has a heat insulating layer formed on a metallic cored bar.
[0009]
According to a fourth aspect of the present invention, a recording material having a fixing member heated by a heating unit and a pressure member in pressure contact with the fixing member is formed by the fixing member and the pressure member. In the fixing device for fixing by passing through the nip portion, the fixing member includes a heat insulating layer and a low temperature portion inside the highest temperature portion, and the temperature difference between the surface side and the inner surface side of the heat insulating layer is It is different in the longitudinal direction of the fixing member.
[0010]
According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the fixing member includes a cavity inside the highest temperature portion, and heat transfer that releases heat to the outside of the fixing member. It has the part.
[0011]
According to a sixth aspect of the present invention, a recording material having a fixing member heated by a heating means and a pressure member in pressure contact with the fixing member is formed by the fixing member and the pressure member. In a fixing device that performs fixing by passing through a nip portion, the fixing member includes a cavity inside the highest temperature portion, and a heat radiation amount in the cavity is different in the longitudinal direction of the fixing member.
[0012]
According to a seventh aspect of the present invention, in the fixing device according to the sixth aspect, the fixing member includes a metallic cored bar, and a heat insulating member provided on a surface inside the cavity where the thickness of the cored bar is smaller than a predetermined thickness. It is characterized by having.
[0013]
According to an eighth aspect of the present invention, in the fixing device according to the sixth or seventh aspect, the surface area in the cavity is larger at the end portion than at the central portion in the longitudinal direction.
[0014]
According to a ninth aspect of the present invention, in the fixing device according to the sixth, seventh, or eighth aspect, the heat transfer section that releases heat to the outside of the fixing member is provided in the cavity. According to a tenth aspect of the present invention, in the fixing device according to the fifth or ninth aspect, the heat transfer portion is an opening that communicates the cavity and the outside of the fixing member. According to an eleventh aspect of the present invention, there is provided the fixing device according to the tenth aspect, further comprising a fan for forcibly moving the heat in the cavity from the opening to the outside.
[0015]
According to a twelfth aspect of the invention, in the fixing device according to the eleventh aspect, the paper size detected by the paper size detecting means for detecting the paper size and the paper passing count counted by the paper passing number counting means for counting the number of paper passing sheets. It has a control part which changes and controls the drive state of a fan based on the number of sheets.
[0016]
According to a thirteenth aspect of the present invention, in the fixing device according to the eleventh aspect, the first temperature detecting means for detecting the temperature of the end portion inside the cavity and the second temperature detecting means for detecting the temperature of the central portion inside the cavity. And a control unit that changes and controls the driving state of the fan based on the difference between the temperature information detected by the first and second temperature detecting means.
[0017]
According to a fourteenth aspect of the present invention, there is provided an image carrier, transfer means for transferring a toner image formed on the image carrier to a recording material, and a fixing device for fixing the toner image transferred to the recording material to the recording material. In the image forming apparatus provided, the fixing device according to any one of claims 1 to 13 is used as the fixing device.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Background of the Invention
In the fixing device, shortening the rise time of the temperature of the fixing member is important for energy saving. By reducing the thickness of the metal core and the elastic layer, the apparatus can have a low heat capacity and the rise time can be shortened. As a result, the rise time can be considerably shortened, but when the heating means is inside, there is a time loss in transferring heat by heat conduction from the inner surface to the surface of the fixing member. In particular, in a fixing device corresponding to a color image that requires a sufficiently thick elastic layer, this time loss is large. For this reason, there are problems such as a delay in the rise time and a time taken to recover from a decrease in the temperature of the fixing member when the paper is passed, and the fixing property is deteriorated because the temperature of the fixing member is lowered when the paper is continuously passed.
[0019]
As a countermeasure against this, an external heating method has been proposed in which a heating unit is arranged on the surface side of the fixing member and the surface of the fixing member is directly heated as described in Patent Document 2. In the external heating method, since only the surface layer that needs to be heated is heated, the rise time is very fast, and the response from the temperature drop at the time of paper passing is good. However, since the actual heat of the surface layer escapes to the inside of the member that does not need to be heated, the pressure member, etc., the rise time is later than the theoretical value of heating only the surface layer.
[0020]
For this reason, a heat insulating layer is provided under the surface layer, and the rise time is shortened by improving the heat insulating property. As a member having good heat insulation, a member containing a gas such as air having low thermal conductivity is generally used. For example, in Japanese Unexamined Patent Publication No. 2000-206815, foamed silicone rubber is often used. Foamed silicone contains air and thus has a low thermal conductivity and good heat insulation, but is compressed in the nip portion to reduce the air content and increase the thermal conductivity. In addition, there is a problem that high surface pressure cannot be applied because of compressive deformation, and deterioration with time is caused by repeated deformation. Further, since the radius of rotation changes due to compression, there is a disadvantage that it is not suitable as a driving side member for conveying a recording material or the like at a constant speed. As a heat insulating material having high rigidity and small deformation, porous ceramics described in JP-A No. 2002-40855, porous resins described in JP-A No. 2000-275996, or hollow particles are mixed with a binder. Can be mentioned.
[0021]
Based on such a background, the configuration and operation of the fixing device and the image forming apparatus according to the present invention will be described. In claim 1, the fixing member includes a low temperature portion inside the maximum temperature portion, and the low temperature from the maximum temperature portion. The thermal resistance to the portion is made different in the longitudinal direction of the fixing member. In the fixing member, a part where heat is easily transmitted and a part where heat is difficult to be transmitted are formed in the longitudinal direction, and the temperature rise is suppressed in a part where heat is easily transmitted. For this reason, the occurrence of temperature unevenness in the fixing member is suppressed, and problems such as wrinkles and gloss unevenness due to temperature unevenness, and hot offset can be prevented. Differentiating the thermal resistance here means, for example, making the heat insulating layer constituting the fixing member thin. The form of heating herein includes one that heats the fixing member from the outside and dielectric heating in which a heating unit is provided between the cored bar and the heat insulating layer, for example. In this case, the paper passing reference position is not defined.
[0022]
According to a second aspect of the present invention, the fixing member has a thermal resistance in the direction of the center of rotation that is different between the central portion and the end portion in the longitudinal direction, and the thermal resistance of the end portion is smaller than that of the central portion. As a result, the heat on the end side that becomes the non-sheet passing portion can easily escape, and the temperature rise at the end portion can be prevented. In this case, if the heating is outside the fixing base, the maximum temperature portion is outside the fixing member, the temperature rise time is short, and the heat supply efficiency to the recording material is high. In this case, the sheet passing reference position is the center of the fixing member. In the third aspect of the present invention, it is specified that the fixing member has a heat insulating layer formed on a metallic cored bar.
[0023]
According to a fourth aspect of the present invention, the fixing member includes a heat insulating layer and a low temperature portion inside the highest temperature portion, and the temperature difference between the surface side and the inner surface side of the heat insulating layer is different in the longitudinal direction of the fixing member. Yes. This is because the heat insulating rates of the heat insulating layers are different. By reducing the heat insulating rate of the end portion of the fixing member, which is a non-sheet passing portion, heat can easily escape and temperature rise can be suppressed. For this reason, the occurrence of temperature unevenness in the fixing member is suppressed, and problems such as wrinkles and gloss unevenness due to temperature unevenness, and hot offset can be prevented.
[0024]
According to a fifth aspect of the present invention, the fixing member includes a cavity inside the highest temperature portion, and a heat transfer portion that releases heat to the outside of the fixing member is provided in the cavity. This is because when the fixing member is heated, the temperature inside increases as time passes. In particular, when the core metal is a metal, when the temperature of the non-sheet passing portion is increased, the heat is transferred to the core metal, so that the temperature of the core metal itself is increased.
Therefore, by providing the heat transfer portion, the heat in the cavity of the fixing member can be released to the outside of the fixing member, the inside of the fixing member is cooled, and an increase in the internal temperature can be suppressed. For this reason, the occurrence of uneven internal temperature in the fixing member is suppressed, and problems such as wrinkles and gloss unevenness due to temperature unevenness, and hot offset can be prevented.
[0025]
According to the sixth aspect of the present invention, the fixing member includes a cavity inside the highest temperature portion, and the heat radiation amount in the cavity is different in the longitudinal direction of the fixing member. In this case, since the temperature of the part where the heat dissipation amount is high is likely to escape, by increasing the heat dissipation amount inside the part corresponding to the non-sheet passing portion, the occurrence of uneven internal temperature in the fixing member is suppressed and the temperature unevenness is suppressed. It is possible to prevent defects such as wrinkles, gloss unevenness, and hot offset caused by the above.
[0026]
According to a seventh aspect of the present invention, when the fixing member has a metal core, the heat insulating member is provided on the surface inside the cavity where the thickness of the core is thinner than a predetermined thickness. When a heat insulating member is provided, heat is not easily transmitted to the inside of the cavity. Therefore, when the core metal corresponding to the paper passing part is thinned, the heat of the part corresponding to the paper passing part can be provided by providing the heat insulating member inside. Is more difficult to escape and can quickly rise in temperature. Further, since there is no heat insulating member for the heat corresponding to the non-sheet passing portion, it is easy to escape and the temperature rise can be suppressed.
[0027]
In the eighth aspect, the surface area in the cavity is made larger at the end than at the center in the longitudinal direction. In other words, the cooling efficiency of the end portion is higher than that of the central portion at the position in the longitudinal direction inside the cavity of the fixing member. For this reason, the cooling efficiency of the temperature at the end portion is higher than that at the center portion, and an increase in end temperature can be prevented.
[0028]
According to a ninth aspect of the present invention, a heat transfer part for releasing heat to the outside of the fixing member is provided in the cavity. Therefore, the heat in the cavity of the fixing member can be released to the outside of the fixing member, the inside of the fixing member is cooled, and an increase in the internal temperature can be suppressed. For this reason, the occurrence of uneven internal temperature in the fixing member is suppressed, and problems such as wrinkles and gloss unevenness due to temperature unevenness, and hot offset can be prevented. Examples of the heat transfer unit include an opening that communicates the cavity and the outside of the fixing member, and a heat pipe that communicates the cavity and the outside of the fixing member.
[0029]
In the case of a fixing member provided with an opening, if a fan for forcibly moving the heat in the cavity from the opening to the outside is provided, the cooling efficiency inside the fixing member is increased, and an increase in the internal temperature can be suppressed. The occurrence of non-uniformity in internal temperature can be suppressed, and problems due to temperature non-uniformity can be prevented.
[0030]
According to a twelfth aspect of the present invention, the driving state of the fan is determined based on the paper size detected by the paper size detecting means for detecting the paper size and the number of passing sheets counted by the passing number counting means for counting the number of passing sheets. A control unit for controlling the change is provided. This is because when the size of the transfer material is large or when the size is small and the number of sheets is small, the edge temperature rise hardly occurs, and the necessity of driving the fan is reduced. Therefore, the degree of increase in the end temperature of the fixing member is estimated from the paper size and the number of sheets to be passed, and when it is not necessary, the fan is stopped, and when necessary, the fan is driven to reduce the power consumption. While reducing, it becomes possible to cool without waste.
[0031]
According to a thirteenth aspect of the present invention, the first temperature detecting means for detecting the temperature of the end portion inside the cavity and the second temperature detecting means for detecting the temperature of the central portion inside the cavity are provided, and detected by these temperature detecting means. The driving state of the fan is changed based on the difference in temperature information. In the first place, there is a problem that a temperature difference (temperature unevenness) occurs in the longitudinal direction of the fixing member. In addition, even if there is a temperature difference, there is an allowable range, so when the temperature difference between the center and the end inside the fixing member is within a predetermined range, the fan is stopped and when the temperature is higher than the predetermined temperature, the fan is driven. This makes it possible to cool without waste while reducing power consumption.
[0032]
According to another aspect of the present invention, the above-described fixing device is used in the image forming apparatus. By using such a fixing device, it is possible to achieve a power saving image forming apparatus with a short rise time while preventing occurrence of hot offset of the toner, destruction of the fixing member, wrinkles, gloss unevenness, and the like. it can.
[0033]
【Example】
The image forming apparatus shown in FIG. 13 is one form of an electrophotographic full-color printer. This printer includes a photoconductor unit 502Y, 502M, 502C, and 502BK having a plurality of photoconductor drums 504Y, 504M, 504C, and 504BK as image carriers in a box-shaped apparatus main body 500, and photoconductor drums 504Y and 504Y. 504M, 504C, and 504BK, and a transfer unit 560 having a transfer conveyance belt 503 as a transfer conveyance body that conveys a sheet P as a transfer material, and a photosensitive drum 504Y on the sheet P conveyed by the transfer conveyance belt 503. , 504M, 504C, and 504BK are provided as transfer rollers 501Y, 501M, 501C, and 501BK as transfer means for transferring toner images on the toner images.
[0034]
The transfer / conveying belt 503 is provided so as to be driven to rotate in a direction indicated by an arrow A, spanned by a plurality of rollers to which rotational driving force is transmitted. The transfer conveyance belt 3 is disposed so as to be in pressure contact with the surface of each photosensitive drum. Developing devices 505Y, 505M, 505C, and 505BK are arranged on the side facing each photosensitive drum. Each developing device includes a two-component developer having a plurality of colors, for example, yellow (hereinafter referred to as Y), magenta (hereinafter referred to as M), cyan (hereinafter referred to as C), and black (hereinafter referred to as K) toner and a carrier. The electrostatic latent images are respectively supplied to the electrostatic latent images formed on the photosensitive drums 504Y, 504M, 504C, and 504BK, and each electrostatic latent image is developed.
[0035]
A writing device 506 as an exposure unit is disposed above the photoreceptor units 502Y, 502M, 502C, and 502K, and a duplex unit 507 is disposed below the photoreceptor units 2Y, 2M, 2C, and 2K. Below the duplex unit 7, paper feed cassettes 513 and 514 that can store transfer materials P of different sizes are disposed. A reversing unit 508 is disposed on the left side of the apparatus main body 500, and a manual feed tray 515 is provided on the right side of the apparatus main body 1 so as to be openable and closable in the arrow B direction. A fixing device 509 is disposed between the transfer conveyance belt 503 and the reversing unit 508. A reverse conveyance path 510 is branched and formed on the downstream side of the fixing device 9 in the transfer material conveyance direction, and the sheet-like transfer material P is discharged at the upper portion of the apparatus by a discharge roller 511 disposed in the reverse conveyance path 10. Guide to the paper tray 512.
[0036]
Each photoconductor unit is a unit for forming a toner image corresponding to each color of Y, M, C, and BK on each photoconductor drum. Each photoconductor unit is provided with a charging device (not shown) that uniformly charges the surface of each photoconductor drum, and a cleaning device that cleans the surface of the photoconductor drum with a brush roller and a cleaning blade. Each photoconductor unit and each charging device have the same configuration except for a place in the apparatus main body 1.
[0037]
The writing device 506 includes a Y laser beam modulated by Y image data from a laser diode as a laser light source (not shown), an M laser beam modulated by M image data, and a C laser beam modulated by C image data. The photosensitive drum is irradiated with BK laser light modulated by the BK image data through a lens and a mirror (not shown) to form an electrostatic latent image on the drum surface.
[0038]
In the duplex image forming mode in which the duplex unit 507 forms an image on both sides of the paper P, the image is formed on one side and then conveyed to the reversal conveyance path 544 of the reversing unit 508 to be switched back and reversed. The received paper P is received and re-conveyed to a transfer portion formed between each photosensitive drum and the transfer conveyance belt 503.
[0039]
The reversing unit 508 includes a plurality of conveying rollers and a plurality of conveying guide plates. In the double-sided image forming mode, the reversing unit 508 reverses the front and back of the transfer material and sends it to the double-sided unit 507. It has a function of discharging the subsequent transfer material out of the apparatus in the same orientation, and a function of discharging the transfer material after image formation outside the apparatus with its front and back reversed. In the paper feed unit in which the paper feed cassettes 513 and 514 are arranged, separation paper feed units 545 and 546 for separating and feeding the paper P on the paper feed cassettes 13 and 14 one by one are provided. .
[0040]
In this embodiment, when image formation is instructed by an operation unit (not shown), each photosensitive drum is rotated by a drive source (not shown) to rotate clockwise. Each charging device applies a charging bias from a power source (not shown) to uniformly charge each photosensitive drum. Each uniformly charged photosensitive drum is exposed by a writing device 506 with laser light modulated with image data of each color of Y, M, C, and K, and an electrostatic latent image is formed on each surface. The These electrostatic latent images on the photoconductive drum are developed by rotating the drum and a developing sleeve (not shown) included in each developing device by a driving source (not shown) to generate each of the Y, M, C, and K colors. It becomes a toner image.
[0041]
One sheet P is separated from the selected one of the sheet cassettes 513 and 514, and is supplied to a registration roller 551 disposed closer to the sheet feed unit than the photosensitive unit 502Y. Paper. In this embodiment, a manual feed tray 515 is disposed on the right side portion of the apparatus main body 500, and paper can be fed from the manual feed tray 515 to the registration rollers 551. The registration roller 551 feeds each sheet onto the transfer / conveying belt 503 at a timing when the toner image of each photosensitive drum coincides with the leading edge thereof. The fed paper P is electrostatically adsorbed by the transfer conveyance belt 3 charged by the paper suction roller 52 around which the transfer conveyance belt 503 is wound, and is conveyed to each transfer unit.
[0042]
The conveyed paper P receives transfer rollers 501Y, 501M, 501C, and 501BK supplied with a transfer bias from a power source (not shown) when sequentially passing through the respective transfer units, whereby Y, The toner images of M, C, and K colors are sequentially superimposed and transferred to form a four-color superimposed full-color toner image. The full color toner image is fixed on the paper P on which the full color toner image is formed by the fixing device 509, and then the paper P is reversed and discharged to the discharge tray 512 through the discharge path corresponding to the designated mode. From the apparatus 509, it goes straight through the reversing unit 508 and is discharged straight.
[0043]
In the image forming apparatus, when the double-sided image forming mode is selected, the recording medium P has a reversal conveyance path 544 in the reversing unit 508 after a toner image is formed on one side and the toner image is fixed by the fixing device 509. Then, after being switched back, the sheet is conveyed to the duplex unit 507, and is fed again from there, and an image is formed on the back surface and discharged in the same manner as in the front surface image formation.
[0044]
The above image forming operation is an operation when the full color mode for superimposing four colors is selected by an operation unit (not shown). However, when the full color mode for superimposing three colors is selected by the operation unit, a K toner image is formed. Is omitted, and a full-color image is formed on the paper P by superimposing Y, M, and C three color toner images. When the monochrome image forming mode is selected on the operation unit, only the K toner image is formed and a monochrome image is formed on the paper P.
(Example 1)
FIG. 1 is a schematic configuration diagram of a fixing device 509 to which the present invention is applied. The fixing device 509 shown here has a fixing member 2 in the form of a roller as a fixing member, and a roller-shaped pressing member 14 that is pressed against the fixing member 2 by a spring 15, and these members are in pressure contact with each other. By doing so, the nip portion N is formed. The pressure member 14 is rotated by being driven by a drive motor (not shown), and the driving force is transmitted to the fixing member 2 to be rotated. Outside the fixing member 2, a halogen heater 5 and a reflection plate 6 are installed as heating means. The reflection plate 6 reflects the heat of the heater toward the fixing member 2. The surface 2 a of the fixing member 2 is controlled to reach a set temperature by radiant heat from the halogen heater 5 and radiant heat reflected by the reflecting plate 6. As the fixing operation, the sheet P to which unfixed toner is attached is heated and pressed while being nipped and transported with respect to the central portions of the fixing member 2 and the pressure member 14 and fixed.
[0045]
The fixing member 2 has a roller shape with an outer diameter of 30 mm and extends in the paper width direction. As shown in FIG. 4, the fixing member 2 is formed of a metal cored bar 4 and a plurality of hollow fibers wound around the cored bar 4. It is comprised from the heat insulation layer 3 made. That is, the fixing member 2 has a cavity 4a therein. Examples of the hollow fiber include hollow structures such as polyester, polyimide, polyamideimide, polybenzimidazole, polybenzobisoxazole, polyphenylene sulfide, glass, ceramics, and metal. The material is not limited in terms of increasing the heat insulating effect, but in this example, polyimide hollow fiber is adopted in consideration of heat resistance, thermal conductivity of the material itself, and strength. The polyimide hollow fiber has an outer total of 230 μm and an inner total of 150 μm, and has high heat insulation and rigidity by tightly winding this hollow fiber. In the vicinity of the surface layer of the fixing member 2, as shown in FIG. 2A, there is a silicone rubber layer having a thickness of 0.1 mm as the elastic layer 12, and a 15 μm-thick PFA tube is coated on the surface layer as the release layer 13. is there.
[0046]
The pressing member 14 has a roller diameter of 30 mm and extends in the paper width direction, and is configured by winding a hollow fiber around a metal core 4 in a layer of about 2 mm as shown in FIG. ing. A 1 mm silicone rubber layer 17 is formed on the hollow fiber layer 16 as an elastic layer, and a 15 μm PFA tube is coated on the surface layer as a release layer 18. With such a configuration, the fixing member 2 and the pressure member 14 are brought to a surface pressure of 2 kg / cm. ² In such a case, the hollow fiber layer is hardly deformed and a uniform nip portion N can be formed.
[0047]
The lengths of the fixing member 2 and the pressure member 14 in the longitudinal direction (paper width direction) indicated by the arrow C are formed longer than the width of the normally used paper P. Both ends of the fixing member 2 are opened to form heat transfer portions 12 and 13 for releasing heat to the outside of the fixing member in the cavity 4a.
[0048]
Next, the operation will be described. When the conventional fixing member as shown in FIG. 3 is used, for example, in a fixing device capable of passing a normal size paper P, a paper P smaller than the normal size is continuously passed. In such a case, in the paper passing area, the paper and toner are deprived of heat and then reheated, so that the temperature becomes substantially constant. However, since the non-sheet passing area is not deprived of heat by the sheet P and is kept heated, it becomes high temperature, the heat insulating layer and the elastic layer are deteriorated, and the normal size sheet is removed after the small sheet is continuously passed. When the paper is passed, the non-sheet passing portion is at a high temperature, so that toner hot offset, paper wrinkles, and the like occur.
[0049]
As shown in FIG. 4, the fixing member 2 according to the present invention has an elastic layer 3 positioned on the end portions 2a and 2b side of the fixing member 2 which becomes a non-sheet passing portion when a small size sheet is passed. The thickness is made smaller than the central portion 2c which is a paper portion, and the thermal resistance from the surface layer of the fixing member 2 to the cored bar 4 is different between the end portions 2a and 2b and the central portion 2c. That is, the temperature difference between the surface side 3 a and the inner surface side 3 b of the heat insulating layer 3 is different in the longitudinal direction of the fixing member 2. Since a highly rigid hollow fiber is used for the heat insulating layer 3, the heat insulating layer 3 has high rigidity, and even if the thickness of the heat insulating layer 3 is changed, the amount of deformation due to the pressure hardly changes, and the paper conveyance direction of the nip portion N There is little variation in width. The surface layer of the fixing member 2 is heated by the radiant heat of the halogen heater 5 shown in FIG. 1, and the heat is retained on the surface layer by the heat insulating layer 3. When paper is passed in this state, the heat of the surface layer moves to the paper P and toner T through which the paper has passed, and is fixed. In this way, the heat of the surface layer is taken away by the paper P and the toner, reheated by the radiation of the halogen heater 5, and can be continuously fixed by repeating this.
[0050]
As described above, in the case of a short heat-fixing span, the heat of the surface layer is immediately taken away by the paper P and the toner T and hardly conducted into the fixing member 2. However, in the case where there is a paper passing portion and a non-paper passing portion for a relatively long time as in the continuous fixing operation of small size paper, the temperature gradient (temperature) between the non-paper passing portion surface layer of the fixing member 2 and the cored bar 4 portion. (Difference) increases, and the heat of the surface layer of the non-sheet passing portion is conducted to the cored bar 4. In particular, since the heat insulating layer 3 in the non-sheet-passing region is thinner than the central portion, the heat of the surface layer is conducted to the core metal 4 faster than the central portion, and the temperature rise of the surface layer in the non-sheet-passing region can be suppressed. Furthermore, since the thickness of the cored bar 4 is thicker at the end portions 2a and 2b than at the central portion 2c, the heat capacity is large and the temperature is not easily saturated. For this reason, the temperature rise of the surface layer in the non-sheet-passing area is suppressed for a long time, and the temperature difference between the sheet-passing portion and the non-sheet-passing portion is kept small, thereby causing hot offset of the toner T, destruction of the fixing member 2, wrinkles and gloss. Generation of unevenness can be prevented. Further, since heat escapes from the heat transfer portions 12 and 13 to the outside of the fixing member in the cavity 4a, an increase in the internal temperature of the fixing member 2 can be reduced. Here, for example, the standard size is assumed to be A3 size paper and the small size paper is A4 size. However, the paper size is not limited, and the standard size paper as shown in FIG. A configuration in which the thickness of the heat insulating layer 3 is changed stepwise so as to correspond to the type of size, or the thickness of the heat insulating layer 3 may be continuously changed as shown in FIG. In this example, the maximum temperature portion of the fixing member 2 is the entire surface layer in a broad sense and the end surface layer located in a non-sheet passing portion in a narrow sense. The low temperature portion is the entire surface of the cavity 4a in a broad sense and the surface of the cavity 4a located in the central portion 2c in a narrow sense.
(Example 2)
The fixing member 2 shown in FIG. 7 has substantially the same configuration as that of the first embodiment, and a fan 8 is provided in the vicinity of the opening of the end portions that are the heat transfer portions 12 and 13 of the fixing member 2, and the core inside the fixing member 2 is provided. The gold 4 is cooled. In this example, air is blown into the cavity 4 a of the fixing member 2 by the fan 8. For this reason, the temperature of the cored bar 4 is less likely to be saturated, the temperature rise of the surface layer in the non-sheet passing region can be suppressed for a long time, and the temperature difference between the sheet passing portion and the non-sheet passing portion can be kept small. It is possible to prevent the occurrence of offset, destruction of the fixing member, wrinkles and gloss unevenness. In this example, air is blown into the cavity 4a of the fixing member 2 by the fan 8, but the air in the cavity 4a may be sucked by the fan 8 to release heat.
Example 3
The fixing member 2 shown in FIG. 8 has substantially the same configuration as that of Example 2, and the surface area of the cored bar 4 is made larger at the end than at the center. The surface of the metal core 4 is mechanically roughened to provide unevenness, or the surface area is increased by forming a fin shape, so that cooling can be performed more efficiently than in the case of claim 2. Moreover, as shown in FIG. 9, according to the thickness of the heat insulation layer 3, for example, the surface area may be changed stepwise or continuously from the central portion 2c to the end portions 2a, 2b. With this configuration, the temperature rise of the surface layer in the non-sheet passing area is suppressed for a long time, and the temperature difference between the sheet passing portion and the non-sheet passing portion is kept small, so that the toner hot offset, the fixing member is destroyed, Generation of wrinkles and uneven gloss can be prevented.
(Example 4)
The fixing member 2 shown in FIG. 10 has substantially the same configuration as that of the second embodiment, and is provided with a heat insulating sheet 9 made of foamed silicone only in the central portion 4 b of the cored bar 4. By disposing the heat insulating sheet 9 in this manner, only the end portions 2a and 2b can be cooled while preventing the temperature of the central portion 2c from being lowered, and therefore only the temperature rising portion of the non-sheet passing portion can be cooled.
(Example 5)
In this example, the sheet size detected by a sheet size sensor 19 serving as a sheet size detecting unit that detects the sheet size and the sheet passing number counting unit 20 serving as a sheet passing number counting unit that counts the number of sheets P passing through the sheet P are counted. Based on the number of sheets passed, the drive state of the fan 8 is changed and controlled by the controller 10 as a control unit.
[0051]
The controller 10 is constituted by a well-known computer. When paper feeding starts, the controller 10 takes in paper size information from the paper size sensor 19 to determine whether the paper size is a normal size or a small size, and measures the number of papers to be passed. The information on the number of passing sheets counted by the container 20 is taken in. When the paper size is the normal size, the fan 8 is not driven regardless of the number of sheets to be passed. Further, when it is determined that the paper P is a small size and the number of sheets to be passed becomes a predetermined number or more, the fan 8 is driven to cool the core 4 of the fixing member 2. Thus, by controlling the drive of the fan 8 according to the paper size and the number of sheets to be passed, it is possible to save power and to avoid unnecessary cooling operation.
(Example 6)
In this example, as shown in FIG. 12, a temperature sensor 11a serving as a first temperature detecting means for detecting the temperature of the end 4c inside the cavity 4a and a second temperature for detecting the temperature of the central part 4b inside the cavity 4a. The temperature sensor 11b serving as the temperature detecting means is provided, and the drive state of the fan 8 is changed and controlled by the controller 14 serving as the control unit based on the difference in temperature information detected by the temperature sensors 11a and 11b. .
[0052]
The controller 14 is composed of a known computer, and when the difference in temperature information from the temperature sensors 11a and 11b is equal to or greater than a predetermined temperature difference, the temperature at the end of the fixing member 2 is increased. Then, the fan 8 is driven. In this way, the fan 8 is driven only when the temperature difference between the end 4c and the center 4b in the cavity 4a is equal to or greater than a predetermined temperature difference, so that power saving can be achieved and unnecessary cooling operation can be avoided.
[0053]
In each embodiment, the paper passing portion refers to the width of the fixing member 2 to which the paper P hits, and the non-paper passing portion refers to the end portions 2a and 2b positioned outside the width of the paper P. In each of the above embodiments, the fixing member 2 has been described as having a roller shape. However, as shown in FIGS. 14 and 15, the fixing member 2 and the tension roller 17 are also applied to a fixing device in which the fixing belt 16 is stretched. it can. When the fixing belt 16 is used, the belt may be heated by the halogen heater 5. The fixing member 2 shown in FIG. 15 has a fan shape in cross section and is in a fixed state so that the fixing belt 16 is in sliding contact.
[0054]
【The invention's effect】
According to the present invention, the fixing member is formed with a part where heat is easily transmitted and a part where heat is not easily transmitted in the longitudinal direction, and the temperature rise is suppressed at the part where heat is easily transmitted. Generation of temperature unevenness in the member is suppressed, and problems such as wrinkles and gloss unevenness due to temperature unevenness, and hot offset can be prevented.
[0055]
According to the present invention, the heat insulation rate of the heat insulation layer is different, and by reducing the heat insulation rate of the end portion of the fixing member that becomes a non-sheet passing portion, heat can easily escape and temperature rise can be suppressed. Therefore, occurrence of temperature unevenness in the fixing member is suppressed, and problems such as wrinkles, gloss unevenness, and hot offset due to temperature unevenness can be prevented.
According to the present invention, since the heat radiation amount in the cavity of the fixing member varies in the longitudinal direction of the fixing member, the temperature of the portion with a high heat radiation amount is easily escaped. By increasing the heat radiation amount, the occurrence of uneven internal temperature in the fixing member is suppressed, and problems such as wrinkles and gloss unevenness due to temperature unevenness, and hot offset can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a fixing device to which the present invention is applied.
2A is a partially enlarged sectional view of a fixing member, and FIG. 2B is a partially enlarged sectional view of a pressure member.
FIG. 3 is a schematic cross-sectional view showing a configuration of a conventional fixing member.
FIG. 4 is a schematic cross-sectional view of a fixing member in the fixing device according to the first exemplary embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view of another fixing member in the fixing device according to the first exemplary embodiment of the present invention.
FIG. 6 is a schematic cross-sectional view of another fixing member in the fixing device shown in Embodiment 1 of the present invention.
FIG. 7 is a schematic cross-sectional view of a fixing member in a fixing device according to Embodiment 2 of the present invention.
FIG. 8 is a schematic cross-sectional view of a fixing member in a fixing device according to Embodiment 3 of the present invention.
FIG. 9 is a schematic cross-sectional view of another fixing member in the fixing device according to Embodiment 3 of the present invention.
FIG. 10 is a schematic cross-sectional view of a fixing member in a fixing device according to Embodiment 4 of the present invention.
FIG. 11 is a schematic configuration diagram illustrating a fixing member and its control system in the fixing device according to the fifth exemplary embodiment of the present invention.
FIG. 12 is a schematic configuration diagram showing a fixing member and its control system in the fixing device shown in Embodiment 6 of the present invention.
FIG. 13 is a schematic configuration diagram of an image recording apparatus equipped with the fixing device of the present invention.
FIG. 14 is a schematic configuration diagram of a fixing device using a belt-like fixing member to which the present invention is applied.
FIG. 15 is a schematic configuration diagram of another fixing device using a belt-shaped fixing member to which the present invention is applied.
[Explanation of symbols]
2 Fixing member
2a, 2b Longitudinal end
2c Longitudinal center
3 Insulation layer
3a Surface side of heat insulation layer
3b Inner surface side of heat insulation layer
4 cored bar
4a cavity
4b Center of the cavity
4c End of cavity
5 Heating means
8 fans
9 Insulation material
10, 14 Control unit
11a First temperature detection means
11b Second temperature detecting means
12, 13 Heat transfer part
14 Pressure member
19 Paper size detection means
20 Number of paper passing counting means
504Y, 504M, 504C, 504BK Image carrier
509 Fixing device
560 transfer means
T Toner image
P Recording material
N Nip part
C Longitudinal direction of fixing member

Claims

A fixing member heated by a heating unit and a pressure member in pressure contact with the fixing member, and a recording material on which a toner image is transferred pass through a nip formed by the fixing member and the pressure member. In the fixing device for fixing by
The fixing device includes a low-temperature portion inside the highest-temperature portion, and a thermal resistance from the highest-temperature portion to the low-temperature portion is different in the longitudinal direction of the fixing member.

The fixing device according to claim 1.
The fixing device according to claim 1, wherein the fixing member has a thermal resistance in a rotation center direction which is different between a central portion and an end portion in the longitudinal direction, and a thermal resistance of the end portion is smaller than the central portion.

The fixing device according to claim 1 or 2,
The fixing device, wherein the fixing member has a heat insulating layer formed on a metallic cored bar.

A fixing member heated by a heating unit and a pressure member in pressure contact with the fixing member, and a recording material on which a toner image is transferred pass through a nip formed by the fixing member and the pressure member. In the fixing device for fixing by
The fixing member includes a heat insulating layer and a low temperature portion inside the highest temperature portion, and the temperature difference between the surface side and the inner surface side of the heat insulating layer is different in the longitudinal direction of the fixing member. apparatus.

The fixing device according to any one of claims 1 to 4,
The fixing member includes a cavity inside the highest temperature portion, and has a heat transfer part that releases heat to the outside of the fixing member.

A fixing member heated by a heating unit and a pressure member in pressure contact with the fixing member, and a recording material on which a toner image is transferred pass through a nip formed by the fixing member and the pressure member. In the fixing device for fixing by
The fixing device includes a cavity inside the highest temperature portion, and a heat radiation amount in the cavity is different in a longitudinal direction of the fixing member.

The fixing device according to claim 6.
The fixing device includes a metallic cored bar and a heat insulating member provided on a surface inside the cavity in a portion where the thickness of the cored bar is smaller than a predetermined thickness.

The fixing device according to claim 6 or 7, wherein:
The fixing device according to claim 1, wherein a surface area in the cavity is larger in an end portion than in a central portion in the longitudinal direction.

The fixing device according to claim 6, 7 or 8.
A fixing device having a heat transfer part for escaping heat to the outside of the fixing member in the cavity.

The fixing device according to claim 5 or 9, wherein
The fixing device according to claim 1, wherein the heat transfer portion is an opening that communicates the cavity and the outside of the fixing member.

The fixing device according to claim 10.
A fixing device having a fan for forcibly moving heat in the cavity from the opening to the outside.

The fixing device according to claim 11.
Control for changing and controlling the driving state of the fan based on the paper size detected by the paper size detecting means for detecting the paper size and the number of passed sheets counted by the passed sheet number counting means for counting the number of passed sheets. A fixing device.

The fixing device according to claim 11.
The first and second temperature detection means includes first temperature detection means for detecting the temperature of the end portion inside the cavity, and second temperature detection means for detecting the temperature of the central portion inside the cavity. And a control unit that changes and controls the driving state of the fan based on a difference in temperature information detected by the means.

An image forming apparatus comprising: an image carrier; a transfer unit that transfers a toner image formed on the image carrier to a recording material; and a fixing device that fixes the toner image transferred to the recording material to the recording material. ,
An image forming apparatus using the fixing device according to claim 1 as the fixing device.