JP2004029194A

JP2004029194A - Image forming apparatus having fixing device

Info

Publication number: JP2004029194A
Application number: JP2002182678A
Authority: JP
Inventors: Masayasu Onodera; 小野寺　正泰
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 2002-06-24
Filing date: 2002-06-24
Publication date: 2004-01-29

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a fixing device which prevents fixation from worsening without dropping the productivity and inhibits a glossiness difference between the front surface (at the time of first fixing on the surface) and the rear surface (at the time of second fixing on the rear side surface). <P>SOLUTION: In the fixing device for the image forming apparatus, a pressing means for pressing a second roller member to a first roller member via a belt member is provided. An image is formed on a first surface of a transfer material and a toner image on the first surface of the transfer material is fixed by passing through the fixing device and then the transfer materia passed through the fixing device is carried by circulation reversal and an image is formed on a second surface of the transfer material and a toner image on the second surface of the transfer material is fixed by passing through the fixing device. Thus toner images on both surfaces of the transfer material are fixed. The fixing device is characterized in that the pressing force to the second roller member by the pressing means is changed between when fixing on the first surface and when fixing on the second surface. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、複写機、プリンタ、ＦＡＸ等の電子写真方式の画像形成装置に関し、特にベルト方式の定着装置を有する画像形成装置に関する。
【０００２】
【従来の技術】
近年、複写機、プリンタ、ＦＡＸ等の電子写真方式の画像形成装置においては、画質への要求が高まり、該画像形成装置の定着装置によって画像の光沢度を上げる、或いは制御する、という動きが見られている。
【０００３】
従来より、複写機、プリンタ、ＦＡＸ等の電子写真方式の画像形成装置に用いられている定着装置として、弾性層を有して所定の温度に維持された発熱ゴムローラと、発熱ゴムローラに圧接し、弾性層を有する加圧ゴムローラとによって、未定着のトナー画像が形成された転写材を挟持搬送しつつ加熱する熱ローラ定着方式が多用されている。
【０００４】
しかしながら、この種の装置では、発熱ゴムローラの熱容量が大きいので、ウォーミングアップ時間が長くなると共に、弾性層内側の温度が高くなり、発熱ゴムローラの寿命を短くしていた。
【０００５】
また、省エネルギー化への要求が高まり、定着部において、同じ消費電力でなるべく高い定着性を得られる定着装置の開発が進められたり、高品質化への要求により、定着部によって画像の光沢度を上げるという動きが見られている。
【０００６】
また、カラー画像ではベタ面積が大きい画像が多く、そのベタ画像も黒以外のものが多くて光沢むらなどが目立つ。上記の発熱ゴムローラ及び加圧ゴムローラにハードローラを用いる場合は、転写材（記録紙）やトナー層の凹凸に応じた光沢のむらが生じるため、画像品位が低下するという問題点があった。
【０００７】
これらの問題を解決するため、無端状のベルト部材（定着ベルト）を用い、複数のローラ部材により定着ベルトを張架し、また、内部に定着ベルトを加熱する発熱体を有し、定着ベルトと対向する発熱ローラと、定着ベルトを挟んで発熱ローラと対向するローラ部材（加圧ローラ）とを設け、発熱ローラと加圧ローラとの間の定着ニップ部と、発熱ローラにより加熱された定着ベルトと加圧ローラとにより形成されるベルトニップ部とにて記録紙上のトナー画像（トナー像）を定着する定着方式を用いた画像形成装置が、特開平１０−３１９７７２号公報等により開示されている。
【０００８】
また前記定着ベルトを用いた画像形成装置に再給紙機構（ＡＤＵ機構）を設け、定着装置により、転写材の一方の面に転写されたトナー像を定着した後、一方の面にトナー像が定着された転写材を再給紙機構により循環反転搬送（反転通紙）し、再度転写材の他方の面に転写されたトナー像を定着する両面画像形成方法がとられている。
【０００９】
さらに両面画像形成後、ステイプル等で両面にトナー画像が形成された転写材を後処理する装置を備えた後処理装置付きの画像形成装置も近来多く用いられている。
【００１０】
【発明が解決しようとする課題】
しかしながら、上記画像形成装置における両面コピー時に、表面（２回定着器を通過する面、第１面）と裏面（１回しか定着器を通過しない面、第２面）とで光沢度が異なるという問題が起こる。特に、ステイプル等で綴じたときにページの左右で光沢度が異なることになり、好ましくない。
【００１１】
この原因としては、２回定着器を通過する表面（第１面）の方が、１回しか定着器を通過しない裏面（第２面）よりも光沢度が高くなってしまう。
【００１２】
しかしながら、２回定着における光沢度の変化幅を図２３に示すように、例えば、転写材（記録紙）として斤量１２８ｇ／ｍ^２のコート紙（商品名：ＮＫアート紙）を用いた場合で、上ローラ（発熱ローラ）と下ローラ（加圧ローラ）とのニップ部における加圧圧力（押圧力）が２００ｋＰａで定着線速度が通常線速度（８０〜２５０ｍｍ／ｓ）の１／２のとき（◆）と、加圧圧力（押圧力）が２００ｋＰａで定着線速度が通常線速度の１／３のとき（■）と、加圧圧力（押圧力）が１４０ｋＰａで定着線速度が通常線速度の１／３のとき（▲）と、の１回目定着時の光沢度（１回目光沢度、（°））と２回定着時とにおける光沢度（２回目光沢度、（°））の変化幅は、図に見られるように、２回目光沢度増量分（°）としては１回目光沢度にかかわらず、２回定着を行うと概ね光沢度は１０〜２５°向上する。また両面コピー時の表裏の光沢度差を図２４に示すように、例えば、上ローラ（発熱ローラ）と下ローラ（加圧ローラ）とのニップ部における加圧圧力を１３９ｋＰａ、上ローラ温度（発熱ローラ温度＝定着ベルト温度）を１９８℃とし、記録紙として斤量１２８ｇ／ｍ^２のコート紙（商品名：ＮＫアート紙）を用いた場合で、上ローラ（発熱ローラ）温度変化に対しての記録紙のベルトニップ部通紙時間（ｍｓ）が１／２線速度相当ニップ時間（定着線速度が通常線速度（８０〜２５０ｍｍ／ｓ）の１／２の線速度での記録紙のベルトニップ部通紙時間）で片面１回定着時の光沢度（°、塗りつぶし三角印）と下ローラ（加圧ローラ）温度差（°）に対しての反転通紙（循環反転搬送）による光沢度上昇量（＝光沢度差（°）：白抜き三角印）、および下ローラ温度（加圧ローラ温度）変化に対しての記録紙のベルトニップ部通紙時間（ｍｓ）が１／３線速度相当ニップ時間（定着線速度が通常線速度（８０〜２５０ｍｍ／ｓ）の１／３の線速度での記録紙のベルトニップ部通紙時間）で片面１回定着時の光沢度（°、塗りつぶし丸印）と反転通紙による光沢度上昇量（＝光沢度差（°）：白抜き丸印）の両面コピー時の表裏の光沢度差（°）は、図に見られるように表裏の光沢度差は概ね１０〜２５°となる。即ち、１回目（１回定着時）と２回目（２回定着時）との光沢度差は概ね１０〜２５°の範囲となる。
【００１３】
この１回目（１回定着時）と２回目（２回定着時）との光沢度差をなくするために考えられる対策としては、
▲１▼２回目の定着の時に定着温度を下げて光沢度を向上させない
▲２▼上ローラ（発熱ローラ）と下ローラ（加圧ローラ）との温度差を大きくする（下ローラの温度を下げる）、
等の対策が講じられているが、
▲１▼の場合、定着器の温度を下げるのには時間がかかり、生産性が落ちてしまうという問題が起こる。また▲２▼の場合下ローラ（加圧ローラ）からの熱供給が減少するので、定着性が悪くなってしまうという問題が起こる。
【００１４】
本発明は上記の問題点を解決し、生産性を落とすことなく、また定着性を悪することを防止し、１回定着時（表面定着時）と２回定着時（裏面定着時）との表裏の光沢度差を抑止する定着装置を有する画像形成装置を提供することを目的とする。
【００１５】
【課題を解決するための手段】
上記本発明の目的は下記の構成により達成される。
【００１６】
（１）無端状のベルト部材と、前記ベルト部材の内周面の一方を張架する第１のローラ部材と、前記ベルト部材を挟んで前記第１のローラ部材と当接する第２のローラ部材と、前記第１のローラ部材と平行で離間して設けられ、前記ベルト部材の前記ベルト部材の内周面の他方を張架する加熱手段を設けた第３のローラ部材とを備え、転写材上のトナー像を定着する定着装置を有する画像形成装置において、前記定着装置に、前記第２のローラ部材を前記ベルト部材を介して前記第１のローラ部材に押圧する押圧手段を設け、転写材の第１面に画像形成を行い前記定着装置を通して転写材の第１面のトナー像を定着した後、前記定着装置を通過した転写材を循環反転搬送して前記転写材の第２面に画像形成を行い前記定着装置を通して転写材の第２面のトナー像を定着し、転写材の第１面と第２面との両面のトナー像を定着するもので、第１面の定着時と第２面の定着時とで前記押圧手段による前記第２のローラ部材への押圧力を変更することを特徴とする定着装置を有する画像形成装置（第１の発明）。
【００１７】
（２）無端状のベルト部材と、前記ベルト部材の内周面の一方を張架する第１のローラ部材と、前記ベルト部材を挟んで前記第１のローラ部材と当接する第２のローラ部材と、前記第１のローラ部材と平行で離間して設けられ、前記ベルト部材の内周面の他方を張架する加熱手段を設けた第３のローラ部材とを備え、前記ベルト部材を挟んで前記第１のローラ部材と前記第２のローラ部材との間に定着ニップ部を形成し、また、前記ベルト部材と前記第２のローラ部材との間にベルトニップ部を形成して、前記定着ニップ部および前記ベルトニップ部により転写材上のトナー像を定着する定着装置を有する画像形成装置において、前記定着装置に、前記ベルトニップ部の前記ベルト部材の移動方向幅を変更するベルトニップ幅変更手段を設け、転写材の第１面に画像形成を行い前記定着装置を通して転写材の第１面のトナー像を定着した後、前記定着装置を通過した転写材を循環反転搬送して前記転写材の第２面に画像形成を行い前記定着装置を通して転写材の第２面のトナー像を定着し、転写材の第１面と第２面との両面のトナー像を定着するもので、第１面の定着時と第２面の定着時とで前記ベルトニップ幅変更手段による前記ベルト部材の移動方向幅を変更することを特徴とする定着装置を有する画像形成装置（第２の発明）。
【００１８】
（３）無端状のベルト部材と、前記ベルト部材の内周面の一方を張架する第１のローラ部材と、前記ベルト部材を挟んで前記第１のローラ部材と当接する第２のローラ部材と、前記第１のローラ部材と平行で離間して設けられ、前記ベルト部材の内周面の他方を張架する加熱手段を設けた第３のローラ部材とを備え、前記ベルト部材を挟んで前記第１のローラ部材と前記第２のローラ部材との間に定着ニップ部を形成し、また、前記ベルト部材と前記第２のローラ部材との間にベルトニップ部を形成して、前記定着ニップ部および前記ベルトニップ部により転写材上のトナー像を定着する定着装置を有する画像形成装置において、前記定着装置に、前記ベルトニップ部の前記第２のローラ部材に接触する圧力を変更する圧力変更手段を設け、転写材の第１面に画像形成を行い前記定着装置を通して転写材の第１面のトナー像を定着した後、前記定着装置を通過した転写材を循環反転搬送して前記転写材の第２面に画像形成を行い前記定着装置を通して転写材の第２面のトナー像を定着し、転写材の第１面と第２面との両面のトナー像を定着するもので、第１面の定着時と第２面の定着時とで前記圧力変更手段により前記ベルトニップ部の前記第２のローラ部材に接触する圧力を変更することを特徴とする定着装置を有する画像形成装置（第３の発明）。
【００１９】
（４）加熱手段を有し金属製の芯金と弾性層からなる第１のローラ部材と、前記第１のローラ部材に対向して設けられた金属製の芯金と弾性層からなる第２のローラ部材とを備え、転写材上のトナー像を定着する定着装置を有する画像形成装置において、前記定着装置に、前記第２のローラ部材を前記第１のローラ部材に押圧する押圧手段を設け、転写材の第１面に画像形成を行い前記定着装置を通して転写材の第１面のトナー像を定着した後、前記定着装置を通過した転写材を循環反転搬送して前記転写材の第２面に画像形成を行い前記定着装置を通して転写材の第２面のトナー像を定着し、転写材の第１面と第２面との両面のトナー像を定着するもので、第１面の定着時と第２面の定着時とで前記押圧手段による前記第２のローラ部材への押圧力を変更することを特徴とする定着装置を有する画像形成装置（第４の発明）。
【００２０】
（５）無端状のベルト部材と、前記ベルト部材の内周面の一方を張架する第１のローラ部材と、前記ベルト部材を挟んで前記第１のローラ部材と当接する第２のローラ部材と、前記第１のローラ部材と平行して設けられ、前記ベルト部材の内周面の他方を張架する加熱手段を設けた第３のローラ部材とを備え、転写材上のトナー像を定着する定着装置を有する画像形成装置において、前記定着装置に、前記第２のローラ部材を前記第１のローラ部材に押圧する押圧バネと押圧バネ固定部材とからなる押圧手段を設けると共に、転写材搬送間隔を変更する転写材搬送間隔変更手段を設け、転写材の第１面に画像形成を行い前記定着装置を通して転写材の第１面のトナー像を定着した後、前記定着装置を通過した転写材を循環反転搬送して前記転写材の第２面に画像形成を行い前記定着装置を通して転写材の第２面のトナー像を定着し、転写材の第１面と第２面との両面のトナー像を定着するもので、第１面の画像形成から第２面の画像形成に移行する際の転写材搬送間隔を、前記第１面または前記第２面が連続して画像形成される際の転写材搬送間隔よりも長くし、その間に前記押圧手段の押圧バネ固定部材を移動させることを特徴とする定着装置を有する画像形成装置（第５の発明）。
【００２１】
（６）無端状のベルト部材と、前記ベルト部材の内周面の一方を張架する第１のローラ部材と、前記ベルト部材を挟んで前記第１のローラ部材と当接する第２のローラ部材と、前記第１のローラ部材と平行して設けられ、前記ベルト部材の内周面の他方を張架する加熱手段を設けた第３のローラ部材とを備え、前記ベルト部材を挟んで前記第１のローラ部材と前記第２のローラ部材との間に定着ニップ部を形成し、また、前記ベルト部材と前記第２のローラ部材との間にベルトニップ部を形成して、前記定着ニップ部および前記ベルトニップ部により転写材上のトナー像を定着する定着装置を有する画像形成装置において、前記定着装置に、前記第２のローラ部材の位置を移動させる移動手段を設けると共に、転写材搬送間隔を変更する転写材搬送間隔変更手段を設け、転写材の第１面に画像形成を行い前記定着装置を通して転写材の第１面のトナー像を定着した後、前記定着装置を通過した転写材を循環反転搬送して前記転写材の第２面に画像形成を行い前記定着装置を通して転写材の第２面のトナー像を定着し、転写材の第１面と第２面との両面のトナー像を定着するもので、第１面の画像形成から第２面の画像形成に移行する際の転写材搬送間隔を、前記第１面または前記第２面が連続して画像形成される際の転写材搬送間隔よりも長くし、その間に前記定着装置の移動手段により前記第２のローラ部材の位置を移動させることを特徴とする定着装置を有する画像形成装置（第６の発明）。
【００２２】
（７）無端状のベルト部材と、前記ベルト部材の内周面の一方を張架する第１のローラ部材と、前記ベルト部材を挟んで前記第１のローラ部材と当接する第２のローラ部材と、前記第１のローラ部材と平行して設けられ、前記ベルト部材の内周面の他方を張架する加熱手段を設けた第３のローラ部材とを備え、前記ベルト部材を挟んで前記第１のローラ部材と前記第２のローラ部材との間に定着ニップ部を形成し、また、前記ベルト部材と前記第２のローラ部材との間にベルトニップ部を形成して、前記定着ニップ部および前記ベルトニップ部により転写材上のトナー像を定着する定着装置を有する画像形成装置において、前記定着装置に、前記ベルトニップ部を形成するためのベルト部材が掛け渡される補助ローラ部材を設けると共に、転写材搬送間隔を変更する転写材搬送間隔変更手段を設け、転写材の第１面に画像形成を行い前記定着装置を通して転写材の第１面のトナー像を定着した後、前記定着装置を通過した転写材を循環反転搬送して前記転写材の第２面に画像形成を行い前記定着装置を通して転写材の第２面のトナー像を定着し、転写材の第１面と第２面との両面のトナー像を定着するもので、第１面の画像形成から第２面の画像形成に移行する際の転写材搬送間隔を、前記第１面または前記第２面が連続して画像形成される際の転写材搬送間隔よりも長くし、その間に前記定着装置の前記補助ローラ部材を移動させることを特徴とする定着装置を有する画像形成装置（第７の発明）。
【００２３】
（８）無端状のベルト部材と、前記ベルト部材の内周面の一方を張架する第１のローラ部材と、前記ベルト部材を挟んで前記第１のローラ部材と当接する第２のローラ部材と、前記第１のローラ部材と平行して設けられ、前記ベルト部材の内周面の他方を張架する加熱手段を設けた第３のローラ部材とを備え、前記ベルト部材を挟んで前記第１のローラ部材と前記第２のローラ部材との間に定着ニップ部を形成し、また、前記ベルト部材と前記第２のローラ部材との間にベルトニップ部を形成して、前記定着ニップ部および前記ベルトニップ部により転写材上のトナー像を定着する定着装置を有する画像形成装置において、前記定着装置に、前記ベルトニップ部の第２のローラ部材に接触する圧力を変更するための前記ベルト部材の内面を摺動する摺動部材と、前記摺動部材を前記ベルト部材を介して前記第２のローラ部材に押圧する摺動補助部材と、からなる圧力変更手段を設けると共に、転写材搬送間隔を変更する転写材搬送間隔変更手段を設け、転写材の第１面に画像形成を行い前記定着装置を通して転写材の第１面のトナー像を定着した後、前記定着装置を通過した転写材を循環反転搬送して前記転写材の第２面に画像形成を行い前記定着装置を通して転写材の第２面のトナー像を定着し、転写材の第１面と第２面との両面のトナー像を定着するもので、前記第１面の画像形成から前記第２面の画像形成に移行する際の転写材搬送間隔を、前記第１面または前記第２面が連続して画像形成される際の転写材搬送間隔よりも長くし、その間に前記圧力変更手段の前記摺動補助部材を移動させることを特徴とする定着装置を有する画像形成装置（第８の発明）。
【００２４】
（９）無端状のベルト部材と、前記ベルト部材の内周面の一方を張架する第１のローラ部材と、前記ベルト部材を挟んで前記第１のローラ部材と当接する第２のローラ部材と、前記第１のローラ部材と平行して設けられ、前記ベルト部材の内周面の他方を張架する加熱手段を設けた第３のローラ部材とを備え、前記ベルト部材を挟んで前記第１のローラ部材と前記第２のローラ部材との間に定着ニップ部を形成し、また、前記ベルト部材と前記第２のローラ部材との間にベルトニップ部を形成して、前記定着ニップ部および前記ベルトニップ部により転写材上のトナー像を定着する定着装置を有する画像形成装置において、前記定着装置に、前記ベルトニップ部を挟んで前記第２のローラ部材に対向する固定部材を設け、且つ、押圧バネと押圧バネ固定部材とからなる前記第２のローラ部材の圧力変更手段を設けると共に、転写材搬送間隔を変更する転写材搬送間隔変更手段を設け、転写材の第１面に画像形成を行い前記定着装置を通して転写材の第１面のトナー像を定着した後、前記定着装置を通過した転写材を循環反転搬送して前記転写材の第２面に画像形成を行い前記定着装置を通して転写材の第２面のトナー像を定着し、転写材の第１面と第２面との両面のトナー像を定着するもので、前記第１面の画像形成から前記第２面の画像形成に移行する際の転写材搬送間隔を、前記第１面または前記第２面が連続して画像形成される際の転写材搬送間隔よりも長くし、その間に前記第２のローラ部材の前記圧力変更手段の押圧バネ固定部材を移動させることを特徴とする定着装置を有する画像形成装置（第９の発明）。
【００２５】
（１０）無端状のベルト部材と、前記ベルト部材の内周面の一方を張架する第１のローラ部材と、前記ベルト部材を挟んで前記第１のローラ部材と当接する第２のローラ部材と、前記第１のローラ部材と平行して設けられ、前記ベルト部材の内周面の他方を張架する加熱手段を設けた第３のローラ部材とを備え、前記ベルト部材を挟んで前記第１のローラ部材と前記第２のローラ部材との間に定着ニップ部を形成し、また、前記ベルト部材と前記第２のローラ部材との間にベルトニップ部を形成して、前記定着ニップ部および前記ベルトニップ部により転写材上のトナー像を定着する定着装置を有する画像形成装置において、前記定着装置に、前記ベルト部材にテンションを付与するテンション補助ローラを設けると共に、転写材搬送間隔を変更する転写材搬送間隔変更手段を設け、転写材の第１面に画像形成を行い前記定着装置を通して転写材の第１面のトナー像を定着した後、前記定着装置を通過した転写材を循環反転搬送して前記転写材の第２面に画像形成を行い前記定着装置を通して転写材の第２面のトナー像を定着し、転写材の第１面と第２面との両面のトナー像を定着するもので、前記第１面の画像形成から前記第２面の画像形成に移行する際の転写材搬送間隔を、前記第１面または前記第２面が連続して画像形成される際の転写材搬送間隔よりも長くし、その間に前記定着装置の前記テンション補助ローラを移動させることを特徴とする定着装置を有する画像形成装置（第１０の発明）。
【００２６】
（１１）加熱手段を有し金属製の芯金と弾性層からなる第１のローラ部材と、前記第１のローラ部材に対向して設けられた金属製の芯金と弾性層からなる第２のローラ部材とを備え、転写材上のトナー像を定着する定着装置を有する画像形成装置において、前記定着装置に、押圧バネと押圧バネ固定部材とからなり前記第２のローラ部材を前記第１のローラ部材に押圧する押圧手段とを設けると共に、転写材搬送間隔を変更する転写材搬送間隔変更手段を設け、転写材の第１面に画像形成を行い前記定着装置を通して転写材の第１面のトナー像を定着した後、前記定着装置を通過した転写材を循環反転搬送して前記転写材の第２面に画像形成を行い前記定着装置を通して転写材の第２面のトナー像を定着し、転写材の第１面と第２面との両面のトナー像を定着するもので、前記第１面の画像形成から前記第２面の画像形成に移行する際の転写材搬送間隔を、前記第１面または前記第２面が連続して画像形成される際の転写材搬送間隔よりも長くし、その間に前記押圧手段の前記押圧バネ固定部材を移動させることを特徴とする定着装置を有する画像形成装置（第１１の発明）。
【００２７】
【発明の実施の形態】
以下、本願発明の実施の形態を説明する。なお、本欄の記載は請求項の技術的範囲や用語の意義を限定するものではない。また、以下の、本発明の実施の形態における断定的な説明は、ベストモードを示すものであって、本発明の用語の意義や技術的範囲を限定するものではない。
【００２８】
本発明に係わる定着装置を用いる画像形成装置の一実施形態の画像形成プロセスおよび各機構について、図１ないし図２２を用いて説明する。図１は、本発明に係わる定着装置を用いる画像形成装置の一実施形態を示すカラー画像形成装置の断面構成図であり、図２は、本発明に係わる第１の例の定着装置を示す概要断面構成図であり、図３は、第１面（表面）の定着時および第２面（裏面）の定着時に用いられる押圧手段を示す図であり、図４は、図２の定着装置における第１面（表面）の定着時および第２面（裏面）の定着時に用いられるベルトニップ幅変更の第１の例を示す図であり、図５は、第１面（表面）の定着時および第２面（裏面）の定着時に用いられるベルトニップ幅変更手段を示す図であり、図６は、図２の定着装置における第１面（表面）の定着時および第２面（裏面）の定着時に用いられるベルトニップ幅変更の第２の例を示す図であり、図７は、第１面（表面）の定着時および第２面（裏面）の定着時に用いられるベルトニップ幅変更手段を示す図であり、図８は、図２の定着装置における第１面（表面）の定着時および第２面（裏面）の定着時に用いられる圧力変更手段の第１の例を示す図であり、図９は、図２の定着装置におけるる第１面（表面）の定着時および第２面（裏面）の定着時に用いられる圧力変更手段の第２の例を示す図であり、図１０は、図２の定着装置における第１面（表面）の定着時および第２面（裏面）の定着時に用いられる圧力変更手段の第３の例を示す図であり、図１１は、第１面（表面）の定着時および第２面（裏面）の定着時に用いられる圧力変更手段を示す図であり、図１２は、本発明に係わる第２の例の定着装置を示す概要断面構成図であり、図１３は、本発明に係わる第１の例の定着装置における第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の転写材搬送間隔を示す図であり、図１４は、図１３の定着装置における第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に用いられるベルトニップ幅変更の第１の例を示す図であり、図１５は、図１３の定着装置における第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に用いられるベルトニップ幅変更の第２の例を示す図であり、図１６は、図１３の定着装置における第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に用いられる圧力変更手段の第１の例を示す図であり、図１７は、図１３の定着装置における第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に用いられる圧力変更手段の第２の例を示す図であり、図１８は、図１３の定着装置における第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に用いられる圧力変更手段の第３の例を示す図であり、図１９は、本発明に係わる第２の例の定着装置における第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の転写材搬送間隔を示す図であり、図２０は、定着荷重と光沢度の関係を示す図であり、図２１は、記録紙のベルトニップ部通紙時間と光沢度の関係を示す図であり、図２２は、本発明による表裏の光沢度差を抑止した結果を示す図である。なお、定着装置の各例において機能、構造を同じくする部材には同一の番号を付した。
【００２９】
図１によれば、画像形成装置ＧＳは、画像形成装置本体ＧＨと画像形成装置本体ＧＨの上部に設けられる画像読取装置ＳＣとから構成される。
【００３０】
画像形成装置本体ＧＨは、タンデム型カラー画像形成装置と称せられるもので、中間転写体の移動方向に沿ってイエロー、マゼンタ、シアンおよび黒色の各カラートナー像を形成する画像形成ユニットを配置し、各画像形成ユニットの像担持体上に形成したカラートナー像を中間転写体上に多重転写して重ね合わせた後、転写材上に一括転写するものである。
【００３１】
図において、画像形成装置本体ＧＨの上部に配設される画像読取装置ＳＣ上に載置された原稿画像が光学系により走査露光され、ラインイメージセンサＣＣＤに読み込まれ、ラインイメージセンサＣＣＤにより光電変換されたアナログ信号は、画像処理部において、アナログ処理、Ａ／Ｄ変換、シェーディング補正、画像圧縮処理等を行った後、画像書込手段としての露光光学系３に画像データ信号を送る。
【００３２】
また図において、中間転写体である中間転写ベルト６の周縁部には、イエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）及び黒色（Ｋ）の各色毎の画像形成用として４組のプロセスユニット１００がカラートナー像の形成手段として、図の矢印で示す鉛直方向の中間転写ベルト６の回転方向に対して、中間転写ベルト６に沿って垂直方向に縦列配置され、Ｙ、Ｍ、Ｃ、Ｋの順に配置されている。
【００３３】
４組のプロセスユニット１００は何れも共通した構造であり、それぞれ、像担持体である感光体ドラム１と、帯電手段としての帯電器２と、画像書込手段としての露光光学系３と、現像手段としての現像器４と像担持体クリーニング手段としての感光体クリーニング装置１９０とからなっている。
【００３４】
像担持体である感光体ドラム１は、例えば外径が４０〜１００ｍｍ程度のアルミニウム等の金属性の部材によって形成される円筒状の基体の外周に、感光体層厚として層厚（膜厚）２０〜４０μｍ程度の有機感光体層（ＯＰＣ）の光導電層を形成したものである。感光体ドラム１は、図示しない駆動源からの動力により、導電層を接地された状態で矢印で示す方向に、例えば８０〜２８０ｍｍ／ｓ程度の線速度で回転される。
【００３５】
感光体ドラム１の周りには、帯電手段としての帯電器２、画像書込手段としての露光光学系３、現像手段としての現像器４を１組とした画像形成部が、図の矢印にて示す感光体ドラム１の回転方向に対して配置される。
【００３６】
帯電手段としての帯電器２は、感光体ドラム１の移動方向に対して直交する方向（図において紙面垂直方向）に感光体ドラム１と対峙し近接して取り付けられる。帯電器２は、感光体ドラム１の有機感光体層に対し所定の電位を与えるコロナ放電電極としての放電ワイヤを備え、トナーと同極性のコロナ放電によって帯電作用（本実施形態においてはマイナス帯電）を行い、感光体ドラム１に対し一様な電位を与える。
【００３７】
画像書込手段である露光光学系３は、不図示の半導体レーザ（ＬＤ）光源から発光されるレーザ光を、回転多面鏡（符号なし）により主走査方向に回転走査し、ｆθレンズ（符号なし）、反射ミラー（符号なし）等を経て感光体ドラム１上を画像信号に対応する電気信号による露光（画像書込）を行い、感光体ドラム１の表面の感光体層に原稿画像に対応する静電潜像を形成する。
【００３８】
現像手段としての現像器４は、感光体ドラム１の帯電極性と同極性に帯電されたイエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）若しくは黒色（Ｋ）の各色の２成分現像剤をそれぞれ収容し、例えば厚み０．５〜１ｍｍ、外径１５〜２５ｍｍの円筒状の非磁性のステンレスあるいはアルミ材で形成された現像剤担持体である現像ローラ４ａを備えている。現像ローラ４ａは、突き当てコロ（不図示）により感光体ドラム１と所定の間隙、例えば１００〜１０００μｍをあけて非接触に保たれ、感光体ドラム１の回転方向と順方向に回転するようになっており、現像時、現像ローラ４ａに対してトナーと同極性（本実施形態においてはマイナス極性）の直流電圧或いは直流電圧に交流電圧を重畳する現像バイアス電圧を印加することにより、感光体ドラム１上の露光部に対して反転現像が行われる。
【００３９】
中間転写体である中間転写ベルト６は、体積抵抗率が１Ｅ＋７〜１Ｅ＋９Ω・ｃｍ程度で、表面抵抗率が１Ｅ＋１０〜１Ｅ＋１２Ω／□程度の半導電性の無端状（シームレス）の樹脂ベルト部材が用いられ、例えば変性ポリイミド、熱硬化ポリイミド、エチレンテトラフルオロエチレン共重合体、ポリフッ化ビニリデン、ナイロンアロイ等のエンジニアリングプラスチックに導電材料を分散した厚さ０．０５〜０．５ｍｍの半導電性の樹脂フィルム基体である。中間転写ベルト６の基体としては、この他に、シリコンゴム或いはウレタンゴム等に導電材料を分散した厚さ０．５〜２．０ｍｍの半導電性ゴムベルトを使用することもできる。中間転写ベルト６はテンションローラ６ａを含む複数のローラ部材により巻回され、鉛直方法に回動可能に支持されている。中間転写体としてはドラム状のものを用いることも可能である。
【００４０】
各色毎の第１の転写手段としての１次転写ローラ７は、例えばシリコンやウレタン等の発泡ゴムを用いたローラ状の導電性部材からなり、中間転写ベルト６を挟んで各色毎の感光体ドラム１に対向して設けられ、中間転写ベルト６の背面を押圧して感光体ドラム１との間に転写域を形成する。１次転写ローラ７には定電流制御によりトナーと反対極性（本実施形態においてはプラス極性）の直流定電流が印加され、転写域に形成される転写電界によって、感光体ドラム１上のトナー像が中間転写ベルト６上に転写される。
【００４１】
画像形成工程（画像形成プロセス）について以下に説明する。
画像記録のスタートにより不図示の感光体駆動モータの始動によりＹの感光体ドラム１が図の矢印で示す方向へ回転され、Ｙの帯電器２によってＹの感光体ドラム１に電位が付与される。Ｙの感光体ドラム１は電位を付与された後、Ｙの露光光学系３によって第１の色信号すなわちＹの画像データに対応する電気信号による露光（画像書込）が行われ、Ｙの感光体ドラム１上にイエロー（Ｙ）の画像に対応する静電潜像が形成される。この潜像はＹの現像器４により反転現像され、Ｙの感光体ドラム１上にイエロー（Ｙ）のトナーからなるトナー像が形成される。Ｙの感光体ドラム１上に形成されたＹのトナー像は１次転写手段としての１次転写ローラ７により中間転写ベルト６上に転写される。
【００４２】
次いで、Ｍの帯電器２によってＭの感光体ドラム１に電位が付与される。Ｍの感光体ドラム１は電位を付与された後、Ｍの露光光学系３によって第１の色信号すなわちＭの画像データに対応する電気信号による露光（画像書込）が行われ、Ｍの感光体ドラム１上にマゼンタ（Ｍ）の画像に対応する静電潜像が形成される。この潜像はＭの現像器４により反転現像され、Ｍの感光体ドラム１上にイエロー（Ｍ）のトナーからなるトナー像が形成される。Ｍの感光体ドラム１上に形成されたＭのトナー像は、１次転写手段としての１次転写ローラ７によりＹのトナー像の重ね合わせて中間転写ベルト６上に転写される。
【００４３】
同様のプロセスにより、Ｃの感光体ドラム１上に形成されたシアン（Ｃ）のトナーからなるトナー像と、Ｋの感光体ドラム１上に形成された黒色（Ｋ）のトナーからなるトナー像が順次中間転写ベルト６上に重ね合わせて形成され、中間転写ベルト６の周面上に、Ｙ、Ｍ、Ｃ及びＫのトナーからなる重ね合わせのカラートナー像が形成される。
【００４４】
転写後のそれぞれの感光体ドラム１の周面上に残ったトナーは像担持体クリーニング手段としての感光体クリーニング装置１９０によりクリーニングされる。
【００４５】
一方、給紙カセット２０Ａ、２０Ｂ、２０Ｃ内に収容された転写材としての記録紙Ｐは、給紙カセット２０Ａ、２０Ｂ、２０Ｃにそれぞれ設けられる送り出しローラ２１および給紙ローラ２２Ａにより給紙され、搬送ローラ２２Ｂ、２２Ｃ、２２Ｄ、レジストローラ２３を経て、トナーと反対極性（本実施形態においてはプラス極性）の電圧が印加される２次転写手段としての２次転写ローラ７Ａに搬送され、２次転写ローラ７Ａの転写域において、中間転写ベルト６上に形成された重ね合わせのカラートナー像（カラー画像）が記録紙Ｐ上に一括して転写される。
【００４６】
カラー画像が転写された記録紙Ｐは、後段において詳述する定着装置１７（或いは定着装置１７Ａ）により定着処理され、排紙ローラ２４に挟持されて機外の排紙トレイ２５上に載置される。
【００４７】
また、２次転写手段としての２次転写ローラ７Ａにより記録紙Ｐ上にカラー画像が転写された後、記録紙Ｐを曲率分離した中間転写ベルト６は、中間転写体クリーニング手段としての中間転写体クリーニング装置１９０ａにより残留トナーが除去される。
【００４８】
両面画像形成時には、一方の面（第１面（表面））にカラー画像（カラートナー像）が形成され、定着装置１７（或いは定着装置１７Ａ）から排出された記録紙Ｐは、分岐手段２６によりシート排紙路から分岐され、それぞれ給紙搬送手段を構成する、下方の循環通紙路２７Ａを経て、再給紙機構（ＡＤＵ機構）である反転搬送路２７Ｂにより表裏を反転され、再給紙搬送部２７Ｃを通過して、給紙ローラ２２Ｄにおいて合流する。反転搬送（循環反転搬送）された記録紙Ｐは、タイミングローラ２３（後段において詳述する転写材搬送間隔変更手段）を経て、再度２次転写ローラ７Ａに搬送され、記録紙Ｐの他方の面（第２面（裏面））上にカラー画像（カラートナー像）が一括転写される。カラー画像が転写された記録紙Ｐは、定着装置１７により定着処理され、排紙ローラ２４に挟持されて機外の排紙トレイ２５上に載置される。
【００４９】
一方、２次転写ローラ７Ａにより記録紙Ｐにカラー画像を転写した後、記録紙Ｐを曲率分離した中間転写ベルト６は、中間転写体クリーニング手段８Ａにより残留トナーが除去される。
【００５０】
なお、上記画像形成装置の説明においては、カラー画像形成にて説明したが、モノクロ画像を形成する場合も本発明に含まれるものである。
【００５１】
図２によれば、本発明の第１の例の定着装置１７は、無端状のベルト部材として定着ベルト２７を用い、第１のローラ部材として張架ローラ１７ｃを用い、第２のローラ部材として加圧ローラ１７ｂを用い、第３のローラ部材として、例えば内部に加熱部材としてのハロゲンランプＨＬａを有する発熱ローラ１７ａを用いるもので、定着ベルト２７の回転方向の一方の側端部（回転方向の下流側で、定着ベルト２７の内周面の一方）において張架ローラ１７ｃにより定着ベルト２７を張架し、また定着ベルト２７の回転方向他方の側端部（回転方向の上流側で、定着ベルト２７の内周面の他方）において発熱ローラ１７ａにより定着ベルト２７を張架し、また定着ベルト２７を挟んで張架ローラ１７ｃと当接する加圧ローラ１７ｂを備えたものであり、定着ベルト２７と加圧ローラ１７ｂとの間にベルトニップ部Ｎａ（第１の定着工程を行う部分）を形成すると共に、定着ベルト２７を挟んで張架ローラ１７ｃと加圧ローラ１７ｂとの間に定着ニップ部Ｎｂ（第２の定着工程を行う部分）を形成し、ベルトニップ部Ｎａと定着ニップ部Ｎｂとを通して熱と圧力とを加えることにより、図１にて説明した記録紙Ｐ上の第１面（表面）のトナー像（或いはカラートナー像）或いは循環反転搬送（反転通紙）して第２面（裏面）のトナー像（カラートナー像）を定着するものである。
【００５２】
定着ベルト２７としては、基体として内径７０〜１２０ｍｍ程度で厚さ２０〜８０μｍ程度の、例えばニッケル電鋳ベルトを用いた金属ベルトや、厚さ４０〜１５０μｍ程度のポリイミドやポリアミド等を用いた耐熱性の樹脂ベルトの外側（外周面）に、厚さ１００〜３００μｍ程度の絶縁性のシリコンゴムを被覆したものに、離型層として表面に厚さ３０〜５０μｍ程度のＰＦＡ（パーフルオロアルコキシ）コーティング加工を施したものを用いる。
【００５３】
張架ローラ１７ｃは、例えばＳＴＫＭ（機械構造用炭素鋼鋼管）を用いた、肉厚２〜５ｍｍ程度の円筒状の金属パイプ１７１ｃと、該金属パイプ１７１ｃの外周面に例えばシリコン材を用い、厚さが（肉厚）３〜１０ｍｍ厚で、ゴム硬度が２５〜３０Ｈｓ（ＪＩＳ、Ａゴム硬度）程度のシリコンのゴム部材からなる弾性層１７２ｃと、弾性層１７２ｃ表面の厚さ１５〜３０μｍ程度のＰＦＡ（パーフルオロアルコキシ）チューブを用いた離型層１７３ｃとからなり、外径３０〜５０ｍｍ程度の軟らかめソフトローラとして形成される。
【００５４】
加圧ローラ１７ｂとしては、例えばＳＴＫＭ（機械構造用炭素鋼鋼管）を用いた、肉厚２〜５ｍｍ程度の円筒状の金属パイプ１７１ｂと、該金属パイプ１７１ｂの外周面に例えばシリコン材を用い、厚さ（肉厚）１〜５ｍｍ厚の薄肉で、ゴム硬度が４０Ｈｓ〜７０Ｈｓ（ＪＩＳ、Ａゴム硬度）のやや硬めのゴム層よりなるゴムローラ層１７２ｂと、該ゴムローラ層１７２ｂの表面に厚さ１５〜５０μｍ程度のＰＦＡ（パーフルオロアルコキシ）チューブを被覆した離型層１７３ｂとを形成した、外径４０〜６０ｍｍ程度のやや硬めのソフトローラとして構成される。また加圧ローラ１７ｂの内部に、図に点線で示すように、加熱部材としてのハロゲンランプＨＬａを設け、定着ベルト２７を加熱するようにしてもよい。
【００５５】
内部にハロゲンランプＨＬａを有する発熱ローラ１７ａは、例えばアルミ材を用いた、肉厚１〜２ｍｍ程度の円筒状の金属パイプ１７１ａと、該金属パイプ１７１ａの外周面に被覆した厚さ１５〜５０μｍ程度のＰＦＡ（パーフルオロアルコキシ）チューブからなる離型層１７３ａとを形成した、外径４０〜６０ｍｍ程度のローラ部材として構成される。
【００５６】
定着ベルト２７と加圧ローラ１７ｂとの間に形成されるベルトニップ部Ｎａと、ソフトローラである張架ローラ１７ｃとソフトローラである加圧ローラ１７ｂとの間に形成させる定着ニップ部Ｎｂとにより記録紙Ｐ上の第１面（表面）のトナー像（或いはカラートナー像）或いは循環反転搬送（反転通紙）して第２面（裏面）のトナー像（カラートナー像）をトナー像（或いはカラートナー像）が定着される。
【００５７】
また、発熱ローラ１７ａに定着ベルト２７を挟んで接触または非接触の温度センサＴＳ１を設け、発熱ローラ１７ａおよび定着ベルト２７の温度制御を行う。
【００５８】
上記定着装置１７においては、冒頭にて述べたように、図１にて述べた画像形成装置における両面コピー時に、２回定着器を通過する表面（第１面）の方が、１回しか定着器を通過しない裏面（第２面）よりも光沢度が高くなってしまい、表面（２回定着器を通過する面、第１面）と裏面（１回しか定着器を通過しない面、第２面）とで光沢度が異なってしまう。特に、ステイプル等で綴じたときにページの左右で光沢度が異なることになり、好ましくない。前述したように、この表裏の光沢度差は概ね１０〜２５°の範囲である。
【００５９】
この表裏の光沢度差を解消するための本発明の各手段について以下に説明するが、その前に、図２０ないし図２２により、それらの本発明の手段によって表裏の光沢度差が解消される前提について説明する。
【００６０】
先ず、表裏の光沢度差を解消するための本発明に係わる、第２のローラ部材を第１のローラ部材に押圧する圧力（押圧力＝加圧圧力）を変更する手段（押圧手段）による定着時の定着ニップ部での定着荷重と、或いは第２のローラ部材をベルト部材を介して第１のローラ部材にの押圧する圧力（押圧力＝加圧圧力）を変更する手段（圧力変更手段）による定着時のベルトニップ部での定着荷重と、或いはベルトニップ部の第２のローラ部材に接触する圧力（押圧力＝加圧圧力）を変更する手段（圧力変更手段）による定着時のベルトニップ部での定着荷重と、光沢度との関係を図２０に示すが、光沢度の荷重依存性は、例えば定着ベルトの温度を１８５℃、下ローラ（加圧ローラ）の温度を１４０℃とし、斤量１２８ｇ／ｍ^２のコート紙（商品名：ＮＫアート紙）を用いた場合、図に示すように、定着時の定着荷重（定着時の加圧圧力（押圧力））が大きいほどベルトニップ部或いは定着ニップ部での定着後のトナー画像の光沢度は高光沢となる。定着時の定着ニップ部或いはベルトニップ部での光沢度と加圧圧力（定着荷重）には相関があり、加圧圧力（押圧力）を大とすると高光沢となり、加圧圧力（押圧力）を小とすると低光沢となる。
【００６１】
また、表裏の光沢度差を解消するための本発明に係わる、ベルトニップ部でのベルト部材の移動方向幅（記録紙のベルトニップ部通紙時間）を変更する手段（ベルトニップ幅変更手段）による定着時の記録紙のベルトニップ部通紙時間（ベルトニップ部の幅）と、或いは本発明の第２のローラ部材の位置を移動させベルトニップ部の幅（記録紙のベルトニップ部通紙時間）を変更する手段（移動手段）による定着時の記録紙のベルトニップ部通紙時間（ベルトニップ部の幅）と、光沢度との関係を図２１に示すが、例えば転写材（記録紙）としてＰＰＣ用コート紙（王子製紙製ＰＰＣ用コート紙、斤量１００ｇ／ｍ^２）を用い、定着ニップ部の記録紙の通紙時間を２８ｍｓ、定着ベルトの温度を２００℃程度とした場合で、下ローラ（加圧ローラ）の温度が１７０℃（塗りつぶし黒丸）のときと、下ローラ（加圧ローラ）の温度が１４０℃（白抜き丸印）のときと、下ローラ（加圧ローラ）の温度が１１０℃（塗りつぶし三角印）のときとの光沢度の変化幅は、図に見られるように、何れの場合においても定着時の記録紙の通紙時間（ベルトニップ部の幅）が大きいほど定着後のトナー画像の光沢度は高光沢となる。定着時の光沢度とベルトニップ部の幅は相関があり、ベルトニップ部の幅を大とすると高光沢となり、ベルトニップ部の幅を小とすることにより低光沢となる。
【００６２】
本発明による表裏の光沢度差を抑止した結果としては、図２２に示すように、記録紙上のトナー画像（トナー像）の１面目（表面）のみ或いは２面目（裏面）のみの１回目の定着時の光沢度を白枠棒グラフで、該トナー画像（トナー像）の２回目の定着時の光沢度（図２３或いは図２４にて述べた概ね１０〜２５°の範囲の光沢度差）を斜線ハッチング棒グラフで、また、１面目として例えば表面トナー画像（トナー像）を形成した後反転通紙（循環反転搬送）し、上記図２０にて示した本発明の押圧力（加圧圧力）の変更手段（押圧手段或いは圧力変更手段）、或いは図２１にて示した本発明のベルトニップ部の幅（記録紙の通紙時間）を長くする手段（ベルトニップ幅変更手段或いは移動手段）、等を用いて、循環反転搬送（反転通紙）した記録紙上の２面目（裏面）のトナー画像（トナー像）を１回で定着したときの光沢度を網掛ハッチング棒グラフで、各図２２に示すように、記録紙上の例えば表面のトナー画像（トナー像）の１面目のみの１回目の定着時の光沢度と、該トナー画像（トナー像）の２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。図２０による定着時の押圧力（加圧圧力）変更手段による場合は、１回目は低定着圧力（このときの光沢度は低い）、２回目は高定着圧力とすることで、両面とも同程度の光沢度となる。また、図２１のベルトニップ部の幅（記録紙のベルトニップ部通紙時間）の変更手段による場合は、１回目はベルトニップ部の幅を小（このときの光沢度は低い）とし、２回目はベルトニップ部の幅を大とすることで、両面とも同程度の光沢度となる。
【００６３】
次に、表裏の光沢度差を解消するための本発明の各定着方法について、図３ないし図１０、及び前述した図２、図２０ないし図２２により以下に説明する。
【００６４】
図２または図３によれば、本発明の定着装置１７は、図２にて述べた構成であり、第１面の定着時と第２面の定着時とで、図３に示すような押圧手段により定着時の張架ローラ１７ｃへの加圧ローラ１７ｂの押圧力（加圧圧力）を変更するものである。
【００６５】
押圧手段による定着時の加圧ローラ１７ｂの押圧力の変更は、両端部のバネ受けＳＰＡ１の下部に設けられる偏芯カムＨＣ１の回転により行われる。偏芯カム駆動モータＭａ１の回転を受けて、減速機構ＧＫ１を通して偏芯カムＨＣ１に設けられる偏芯軸Ｊａ１を回転駆動し、両端部の偏芯カムＨＣ１の回転が行われる。両端部の偏芯カムＨＣ１が、図３に矢印で示す時計方向へ回転されると、両端部のバネ受けＳＰＡ１が上側へ持ち上げられて位置を移動され、両端部の押圧バネＳＰａ１が加圧ローラ１７ｂの両端部の回転軸Ｊｔ１を押圧（加圧）し、加圧ローラ１７ｂを定着ベルト２７を介して張架ローラ１７ｃに押圧（加圧）するものである。この際、循環反転搬送（反転通紙）した第２面（裏面）の定着時に、前記押圧手段による定着時の加圧ローラ１７ｂへの押圧力を、第１面（表面）の定着時の押圧手段による加圧ローラ１７ｂへの押圧力よりも大きくなるように短時間で行うことにより、図２０にて述べたように、定着時の定着荷重（定着時の加圧圧力（押圧力））が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【００６６】
上記により、定着時の定着圧力（定着荷重）の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【００６７】
また、図２、図４、図５によれば、本発明の定着装置１７は、図２にて述べた構成であり、第１面の定着時と第２面の定着時とで、例えば図５に示すようなベルトニップ幅変更手段により図４に一点鎖線で示す位置に加圧ローラ１７ｂの位置を変更し、定着時のベルトニップ部Ｎａの定着ベルト２７の移動方向幅（記録紙のベルトニップ部通紙時間）を変更するものである。
【００６８】
ベルトニップ幅変更手段によるベルトニップ部Ｎａの定着ベルト２７の移動方向幅の変更は、両端部のバネ受けＳＰＡ２の下部に設けられる偏芯カムＨＣ２の回転により行われる。偏芯カム駆動モータＭａ２の回転を受けて、減速機構ＧＫ２を通して偏芯カムＨＣ２に設けられる偏芯軸Ｊａ２を回転駆動し、両端部の偏芯カムＨＣ２の回転が行われる。両端部の偏芯カムＨＣ２が、図５に矢印で示す時計方向へ回転されると、両端部のバネ受けＳＰＡ２が上側へ持ち上げられて位置を移動され、両端部の押圧バネＳＰａ２が加圧ローラ１７ｂの両端部の回転軸Ｊｔを押圧（加圧）し、加圧ローラ１７ｂを定着ベルト２７を介して張架ローラ１７ｃに押圧（加圧）すると共に、ベルトニップ部Ｎａの定着ベルト２７の移動方向幅も変更される。
【００６９】
循環反転搬送（反転通紙）した第２面（裏面）の定着時に、ベルトニップ幅変更手段によるベルトニップ部Ｎａの定着ベルト２７の移動方向幅（記録紙のベルトニップ部通紙時間）を、第１面（表面）の定着時の加圧ローラ１７ｂによるベルトニップ部Ｎａの定着ベルト２７の移動方向幅（記録紙のベルトニップ部通紙時間）よりも大きくする。これにより、定着時のベルトニップ部での定着ベルトの移動方向幅の変更が短時間で行われると共に、また図２１にて述べたように、定着時のベルトニップ部の幅（記録紙のベルトニップ部通紙時間）が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と循環反転搬送（反転通紙）した２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【００７０】
上記により、定着時のベルトニップ部の幅の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【００７１】
また図６または図７によれば、図６に示すように、定着装置１７に、ベルトニップ部Ｎａを形成するための定着ベルト２７が掛け渡される補助ローラ部材としての補助ローラＨＲａを設け、例えば図７に示すようなベルトニップ幅変更手段によりベルトニップ部Ｎａの定着ベルト２７の移動方向幅の変更を変更するものである。
【００７２】
ベルトニップ幅変更手段によるベルトニップ部Ｎａの定着ベルト２７の移動方向幅の変更は、両端部のバネ受けＳＰＡ３の下部に設けられる偏芯カムＨＣ３の回転により行われる。偏芯カム駆動モータＭａ３の回転を受けて、減速機構ＧＫ３を通して偏芯カムＨＣ３に設けられる偏芯軸Ｊａ３を回転駆動し、両端部の偏芯カムＨＣ３の回転が行われる。両端部の偏芯カムＨＣ３が、図７に矢印で示す時計方向へ回転されると、両端部のバネ受けＳＰＡ３が下側へ押し下げられて位置を移動され、両端部の押圧バネＳＰａ３が補助ローラＨＲａの両端部の回転軸Ｊｔ２を押圧（加圧）し、補助ローラＨＲａが図６の点線の位置に移動する。これにより、定着ベルト２７の加圧ローラ１７ｂに対する巻きかけ量、即ち、ベルトニップ部Ｎａの定着ベルト２７の移動方向幅が変更される。
【００７３】
循環反転搬送（反転通紙）した第２面（裏面）の定着時に、ベルトニップ幅変更手段によるベルトニップ部Ｎａの定着ベルト２７の移動方向幅（記録紙のベルトニップ部通紙時間）を、第１面（表面）のベルトニップ部Ｎａの定着ベルト２７の移動方向幅（記録紙のベルトニップ部通紙時間）よりも大きくする。これにより、定着時のベルトニップ部での定着ベルトの移動方向幅の変更が短時間で行われると共に、また図２１にて述べたように、定着時のベルトニップ部の幅（記録紙のベルトニップ部通紙時間）が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【００７４】
上記により、定着時のベルトニップ部の幅の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【００７５】
また図８によれば、本発明の定着装置１７は、図２にて述べた構成であり、第１面の定着時と第２面の定着時とで、図８に示すような圧力変更手段により定着時のベルトニップ部Ｎａの加圧ローラ１７ｂに接触する圧力（押圧力＝加圧圧力）を変更するものである。
【００７６】
圧力変更手段による定着時のベルトニップ部Ｎａの加圧ローラ１７ｂに接触する圧力の変更は、保持部材ＨＧとバネ受けＳＰＡ４との間に設けられる押圧バネＳＰａ４と、保持部材ＨＧの上部に設けられる偏芯カムＨＣ４の回転により行われる。偏芯カム駆動モータＭａ４の回転を受けて、減速機構ＧＫ４を通して偏芯カムＨＣ４に設けられる偏芯軸Ｊａ４を回転駆動し、偏芯カムＨＣ４の回転が行われる。偏芯カムＨＣ４が、図８に矢印で示す時計方向へ回転されると、バネ受けＳＰＡ４が下側へ押し下げられて位置を移動され、押圧バネＳＰａ４がバネ受けＳＰＡ４を押圧（加圧）し、補助加圧パッドＨＰを定着ベルト２７を介して加圧ローラ１７ｂに押圧（加圧）するものである。循環反転搬送（反転通紙）した第２面（裏面）の定着時に、前記圧力変更手段によるベルトニップ部Ｎａの加圧ローラ１７ｂに接触する圧力（押圧力＝加圧圧力）を、第１面（表面）の定着時の圧力変更手段によるベルトニップ部Ｎａの加圧ローラ１７ｂに接触する圧力（押圧力＝加圧圧力）よりも大きくなるように変更を行う。これにより、定着時のベルトニップ部Ｎａへの押圧力の変更が短時間で行われると共に、図２０にて述べたように、定着時の定着荷重（定着時の加圧圧力（押圧力））が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【００７７】
上記により、定着時のベルトニップ部の押圧力（定着荷重）の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【００７８】
また図９に示すように、定着装置１７に、ベルトニップ部Ｎａを挟んで加圧ローラ１７ｂに対向する固定部材である固定板ＫＰａを定着ベルト２７の内部に設け、例えば図５にてベルトニップ幅変更手段として説明した押圧バネＳＰａ２と押圧バネ固定部材としてのバネ受けＳＰＡ２等を圧力変更手段として用い、ベルトニップ部Ｎａでの加圧ローラ１７ｂの固定板ＫＰａへの押圧力の変更を、該圧力変更手段により行い、図に一点鎖線で示すように、下側から上側へ加圧ローラ１７ｂを押し上げ、定着ベルト２７を介して固定板ＫＰａに加圧ローラ１７ｂを押圧（加圧）するようにしてもよい。この際、循環反転搬送（反転通紙）した第２面（裏面）の定着時に、前記圧力変更手段による加圧ローラ１７ｂのベルトニップ部Ｎａに接触する圧力（押圧力＝加圧圧力）を、第１面（表面）の定着時の圧力変更手段による加圧ローラ１７ｂのベルトニップ部Ｎａに接触する圧力（押圧力＝加圧圧力）よりも大きくなるように前記圧力変更手段による定着時の加圧ローラ１７ｂの定着ベルト２７への押圧力（加圧圧力）の変更を短時間で行う。これにより、定着時のベルトニップ部Ｎａへの押圧力の変更が短時間で行われると共に、図２０にて述べたように、定着時の定着荷重（定着時の加圧圧力（押圧力））が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【００７９】
上記により、定着時のベルトニップ部の押圧力（定着荷重）の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【００８０】
また図１０または図１１によれば、図１０に示すように、定着装置１７に、ベルトニップ部Ｎａを挟んで加圧ローラ１７ｂに対向するテンション補助ローラＴＲａを定着ベルト２７の内部に設け、例えば図１１に示すように、押圧バネＳＰａ５と押圧バネ固定部材としてのバネ受けＳＰＡ５を圧力変更手段として用い、該圧力変更手段により定着時の加圧ローラ１７ｂへのテンション補助ローラＴＲａの押圧力（加圧圧力）を変更するものである。
【００８１】
圧力変更手段による定着時のテンション補助ローラＴＲａの押圧力の変更は、両端部のバネ受けＳＰＡ５の下部に設けられる偏芯カムＨＣ５の回転により行われる。偏芯カム駆動モータＭａ５の回転を受けて、減速機構ＧＫ５を通して偏芯カムＨＣ５に設けられる偏芯軸Ｊａ５を回転駆動し、両端部の偏芯カムＨＣ５の回転が行われる。両端部の偏芯カムＨＣ５が、図１１に矢印で示す時計方向へ回転されると、両端部のバネ受けＳＰＡ５が下側へ押し下げられて位置を移動され、両端部の押圧バネＳＰａ５がテンション補助ローラＴＲａの両端部の回転軸Ｊｔ４を押圧（加圧）し、テンション補助ローラＴＲａを定着ベルト２７を介して加圧ローラ１７ｂに押圧（加圧）するものである。
【００８２】
ベルトニップ部Ｎａでのテンション補助ローラＴＲａの加圧ローラ１７ｂへの押圧力の変更を、該圧力変更手段により行い、図１０に一点鎖線で示すように、斜め下側へテンション補助ローラＴＲａを押し下げ、定着ベルト２７を介して加圧ローラ１７ｂにテンション補助ローラＴＲａを押圧（加圧）するようにしてもよい。この際、循環反転搬送（反転通紙）した第２面（裏面）の定着時に、前記圧力変更手段によるテンション補助ローラＴＲａのベルトニップ部Ｎａに接触する圧力（押圧力＝加圧圧力）を、第１面（表面）の定着時の圧力変更手段によるテンション補助ローラＴＲａのベルトニップ部Ｎａに接触する圧力（押圧力＝加圧圧力）よりも大きくなるように前記圧力変更手段による定着時のテンション補助ローラＴＲａの定着ベルト２７への押圧力（加圧圧力）の変更を短時間で行う。これにより、定着時のベルトニップ部Ｎａへの押圧力の変更が短時間で行われると共に、また図２０にて述べたように、定着時の定着荷重（定着時の加圧圧力（押圧力））が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【００８３】
なお上記において、定着ベルト２７への定着時の押圧力（加圧圧力）の変更を、発熱ローラ１７ａを図１０に一点鎖線で示す右方向の位置へ移動し、張架ローラ１７ｃと発熱ローラ１７ａとの間を広げてベルトニップ部Ｎａの幅を大きくするようにすることも可能である。また、張架ローラ１７ｃを左方向へ位置を移動し、ベルトニップ部Ｎａの幅を大きくするようにしてもよい。
【００８４】
上記により、定着時のベルトニップ部の押圧力（定着荷重）の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【００８５】
図１２によれば、本発明の第２の例の定着装置１７Ａは、第１のローラ部材として加熱ローラ１７ｄを用い、第２のローラ部材として図２の第１の例の定着装置１７において第２のローラ部材として用いた加圧ローラ１７ｂを用い、例えば加熱ローラ１７ｄの内部に加熱部材としてのハロゲンランプＨＬａを備えたものであり、加熱ローラ１７ｄと加圧ローラ１７ｂとの間に定着ニップ部Ｎｂを形成し、定着ニップ部Ｎｂを通して熱と圧力とを加えることにより、図１にて説明した記録紙Ｐ上の第１面（表面）のトナー像（或いはカラートナー像）或いは循環反転搬送（反転通紙）して第２面（裏面）のトナー像（カラートナー像）を定着するものである。この際、加圧ローラ１７ｂの内部にも加熱部材としてのハロゲンランプＨＬａを配設するようにしてもよい。
【００８６】
内部にハロゲンランプＨＬａを設けた加熱ローラ１７ｄは、例えばＳＴＫＭ（機械構造用炭素鋼管）を用いた、肉厚２〜５ｍｍ程度の円筒状の芯金としての金属パイプ１７１ｄと、該金属パイプ１７１ｄの外周面に例えばシリコン材を用い、厚さが（肉厚）５〜１５ｍｍ厚で、ゴム硬度が２５〜３０Ｈｓ（ＪＩＳ、Ａゴム硬度）程度のシリコンのゴム部材からなる弾性層１７２ｄと、弾性層１７２ｄ表面の厚さ１５〜３０μｍ程度のＰＦＡ（パーフルオロアルコキシ）チューブを用いた離型層１７３ｄとからなり、外径４０〜６０ｍｍ程度の軟らかめソフトローラとして形成される。
【００８７】
加圧ローラ１７ｂとしては、図２にて述べたと同様に、例えばＳＴＫＭ（機械構造用炭素鋼管）を用いた、肉厚２〜５ｍｍ程度の円筒状の芯金としての金属パイプ１７１ｂと、該金属パイプ１７１ｂの外周面に例えばシリコン材を用い、厚さ（肉厚）１〜５ｍｍ厚の薄肉で、ゴム硬度が４０Ｈｓ〜７０Ｈｓ（ＪＩＳ、Ａゴム硬度）のやや硬めのゴム部材からなる弾性層としてのゴムローラ層１７２ｂと、該ゴムローラ層１７２ｂの表面に厚さ１５〜５０μｍ程度のＰＦＡ（パーフルオロアルコキシ）チューブを被覆した離型層１７３ｂとを形成した、外径４０〜６０ｍｍ程度のやや硬めのソフトローラとして構成される。
【００８８】
ソフトローラである加熱ローラ１７ｄとソフトローラである加圧ローラ１７ｂとの間に形成させる定着ニップ部Ｎｂにより記録紙Ｐ上の第１面（表面）のトナー像（或いはカラートナー像）或いは循環反転搬送（反転通紙）して第２面（裏面）のトナー像（カラートナー像）をトナー像（或いはカラートナー像）が定着される。
【００８９】
また、加熱ローラ１７ｄに接触または非接触の温度センサＴＳ１を設け、加熱ローラ１７ｄおよび定着ベルト２７の温度制御を行う。
【００９０】
上記定着装置１７Ａにおいても、冒頭にて述べたように、図１にて述べた画像形成装置における両面コピー時に、２回定着器を通過する表面（第１面）の方が、１回しか定着器を通過しない裏面（第２面）よりも光沢度が高くなってしまい、表面（２回定着器を通過する面、第１面）と裏面（１回しか定着器を通過しない面、第２面）とで光沢度が異なってしまう。特に、ステイプル等で綴じたときにページの左右で光沢度が異なることになり、好ましくない。前述したように、この表裏の光沢度差は概ね１０〜２５°の範囲である。
【００９１】
第２の例の定着装置１７Ａにおける本発明により表裏の光沢度差が解消される前提は、図２０および図２２にて前述したと同様である。この第２の例の定着装置１７Ａにおける表裏の光沢度差を解消するための本発明の定着方法について、図１２、及び前述した図３、図２０ないし図２２により以下に説明する。
【００９２】
図１２または、前述した図３によれば、本発明の定着装置１７Ａは、図１２にて述べた構成であり、第１面の定着時と第２面の定着時とで、図３にて述べたように、押圧手段により定着時の加熱ローラ１７ｄへの加圧ローラ１７ｂの押圧力（加圧圧力）を変更するものである。
【００９３】
押圧手段による定着時の加圧ローラ１７ｂの押圧力の変更は、図３にて述べたと同様である。循環反転搬送（反転通紙）した第２面（裏面）の定着時に、前記押圧手段による定着時の加圧ローラ１７ｂへの押圧力を、第１面（表面）の定着時の押圧手段による加圧ローラ１７ｂへの押圧力よりも大きくなるよう短時間で変更を行う。これにより、図２０にて述べたように、定着時の定着荷重（定着時の加圧圧力（押圧力））が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【００９４】
上記により、定着時の定着圧力（定着荷重）の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【００９５】
次に、上記図２ないし図１１にて説明した本発明に係わる第１の例の定着装置１７、或いは図１２にて説明した本発明に係わる第２の例の定着装置１７Ａにおける、第１面（表面）と第２面（裏面）との光沢度差を抑止する定着方法に加えて、前述した押圧手段、圧力変更手段等による定着時のベルトニップ部での定着荷重の変更のタイミングや、ベルトニップ幅変更手段、移動手段等によるベルトニップ部の幅の変更のタイミングについて、図１３ないし図１９、及び前述した図３、図５、図７、図１１、図２０ないし図２２により以下に説明する。上記変更タイミングは、何れも第１面の画像形成から第２面の画像形成に移行する際に、転写材搬送間隔を変更する転写材搬送間隔変更手段（図１にて説明したタイミングローラ２３）にて行われるものである。
【００９６】
図１３に示す本発明の定着装置は、図２にて説明した第１の例の定着装置１７と同様な構成であり、各部材は、図２にて説明したと同様な構造、機能の部材が用いられる。
【００９７】
上記定着装置１７においては、冒頭にて述べたように、図１にて述べた画像形成装置における両面コピー時に、２回定着器を通過する表面（第１面）の方が、１回しか定着器を通過しない裏面（第２面）よりも光沢度が高くなってしまい、表面（２回定着器を通過する面、第１面）と裏面（１回しか定着器を通過しない面、第２面）とで光沢度が異なってしまう。特に、ステイプル等で綴じたときにページの左右で光沢度が異なることになり、好ましくない。前述したように、この表裏の光沢度差は概ね１０〜２５°の範囲である。
【００９８】
上記第１の例の定着装置１７において、本発明による表裏の光沢度差が解消される前提は、図２０および図２２にて前述したと同様である。この第１の例の定着装置１７における、第１面の画像形成から第２面の画像形成に移行する際の、転写材搬送間隔を変更する転写材搬送間隔変更手段としては、図１にて説明した転写材としての記録紙Ｐを第１の転写手段の転写域に給送するタイミングローラ２３を転写材搬送間隔変更手段として用いて行われるものである。
【００９９】
図１３または図３によれば、本発明の定着装置１７は、図１３にて述べた構成であり、図１３に一点鎖線で示す第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の、第１面（表面）の転写材としての記録紙Ｐの後端部Ｐｂと反転通紙（循環反転搬送）された記録紙Ｐの第２面（裏面）の先端部Ｐａとの間の転写材搬送間隔を、例えば１５ｍｓとし、図１３に実線で示す第１面（表面）のみ（または第２面（裏面）のみ（不図示））が連続して画像形成される際の、先の記録紙Ｐの後端部Ｐｂと後の記録紙Ｐの先端部Ｐａとの間の転写材搬送間隔、例えば１０ｍｓ、よりも長くなるようにタイミングローラ２３を制御し、その間に図３に示すような押圧手段の押圧バネ固定部材としてのバネ受けＳＰＡ１を移動させて、加圧ローラ１７ｂを押圧し、定着ニップ部Ｎｂ押圧力を大きくして、裏面の光沢度を上げるものである。
【０１００】
押圧バネ固定部材としてのバネ受けＳＰＡ１の移動は、両端部のバネ受けＳＰＡ１の下部に設けられる偏芯カムＨＣ１の回転により行われる。偏芯カム駆動モータＭａの回転を受けて、減速機構ＧＫ１を通して偏芯カムＨＣ１に設けられる偏芯軸Ｊａ１を回転駆動し、両端部の偏芯カムＨＣ１の回転が行われる。両端部の偏芯カムＨＣ１が、図３に矢印で示す時計方向へ回転されると、両端部のバネ受けＳＰＡ１が上側へ持ち上げられて位置を移動する。これにより、両端部の押圧バネＳＰａ１が加圧ローラ１７ｂの両端部の回転軸Ｊｔを押圧（加圧）し、加圧ローラ１７ｂを定着ベルト２７を介して張架ローラ１７ｃに押圧（加圧）し、定着ニップ部Ｎｂの押圧力が大きくなる。第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に、張架ローラ１７ｃに対する加圧ローラ１７ｂの押圧力が大きくなる方向を移動方向としてバネ受けＳＰＡ１を上方に移動させる。これにより、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時の定着圧力（定着荷重）の変更が短時間で行われると共に、また図２０にて述べたように、定着時の定着荷重（定着時の加圧圧力（押圧力））が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【０１０１】
上記により、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時の定着圧力（定着荷重）の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【０１０２】
また図１３、図１４、または前述した図５によれば、本発明の定着装置１７は、図１３および図１４にて述べた構成である。図１４に一点鎖線で示す第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の、第１面（表面）の転写材としての記録紙Ｐの後端部Ｐｂと反転通紙（循環反転搬送）された記録紙Ｐの第２面（裏面）の先端部Ｐａとの間の転写材搬送間隔を、例えば１５ｍｓとし、図１４に実線で示す第１面（表面）のみ（または第２面（裏面）のみ（不図示））が連続して画像形成される際の、先の記録紙Ｐの後端部Ｐｂと後の記録紙Ｐの先端部Ｐａとの間の転写材搬送間隔、例えば１０ｍｓ、よりも長くなるようにタイミングローラ２３を制御し、その間に図５に示すような移動手段により加圧ローラ１７ｂの位置を移動させて、ベルトニップ部Ｎａの幅を広げて、通紙時間を長くし、裏面の光沢度を上げるものである。
【０１０３】
加圧ローラ１７ｂの位置の移動の変更は、図５に示す両端部のバネ受けＳＰＡ２下部に設けられる偏芯カムＨＣ２の回転により行われる。偏芯カム駆動モータＭａ２の回転を受けて、減速機構ＧＫ２を通して偏芯カムＨＣ２に設けられる偏芯軸Ｊａ２を回転駆動し、両端部の偏芯カムＨＣ２の回転が行われる。両端部の偏芯カムＨＣ２が、図５に矢印で示す時計方向へ回転されると、両端部のバネ受けＳＰＡ２が上側へ持ち上げられて位置を移動され、両端部の押圧バネＳＰａ２が加圧ローラ１７ｂの両端部の回転軸Ｊｔ１を押圧（加圧）し、加圧ローラ１７ｂを定着ベルト２７を介して張架ローラ１７ｃに押圧（加圧）、移動させるものである。この際、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に、ベルトニップ部Ｎａでの定着ベルト２７の移動方向幅（記録紙のベルトニップ部通紙時間）が大きくなる方向を移動方向として加圧ローラ１７ｂを上方に移動さる。これにより、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時のベルトニップ部での定着ベルトの移動方向幅の変更が短時間で行われると共に、また図２１にて述べたように、定着時のベルトニップ部の幅（記録紙のベルトニップ部通紙時間）が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と循環反転搬送（反転通紙）した２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【０１０４】
上記により、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時のベルトニップ部の幅の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【０１０５】
また図１５または前述した図７によれば、本発明の定着装置１７は、図１３および図７にて述べた構成である。図１５に一点鎖線で示す第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の、第１面（表面）の転写材としての記録紙Ｐの後端部Ｐｂと反転通紙（循環反転搬送）された記録紙Ｐの第２面（裏面）の先端部Ｐａとの間の転写材搬送間隔を、例えば１５ｍｓとし、図１５に実線で示す第１面（表面）のみ（または第２面（裏面）のみ（不図示））が連続して画像形成される際の、先の記録紙Ｐの後端部Ｐｂと後の記録紙Ｐの先端部Ｐａとの間の転写材搬送間隔、例えば１０ｍｓ、よりも長くなるようにタイミングローラ２３を制御し、その間に前記補助ローラＨＲａの位置を移動させて、ベルトニップ部Ｎａの幅を広げて、通紙時間を長くし、裏面の光沢度を上げるものである。
【０１０６】
該補助ローラＨＲａの位置の移動の変更は、例えば図７にて説明した押圧バネＳＰａ３と押圧バネ固定部材としてのバネ受けＳＰＡ３とを用いて行われ、押圧バネＳＰａ３が補助ローラＨＲａの両端部を押圧（加圧）し、補助ローラＨＲａが定着ベルト２７を押圧（加圧）、移動させるものである。この際、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に、ベルトニップ部Ｎａでの定着ベルト２７の移動方向幅（記録紙のベルトニップ部通紙時間）が大きくなる方向を移動方向として補助ローラＨＲａを左下方に移動させる。これにより、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時のベルトニップ部での定着ベルトの移動方向幅の変更が短時間で行われると共に、また図２１にて述べたように、定着時のベルトニップ部の幅（記録紙のベルトニップ部通紙時間）が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と循環反転搬送（反転通紙）した２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【０１０７】
上記により、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時のベルトニップ部の幅の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【０１０８】
また図１６または前述した図８によれば、本発明の定着装置１７は、図１３および図８にて述べた構成である。図１６に一点鎖線で示す第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の、第１面（表面）の転写材としての記録紙Ｐの後端部Ｐｂと反転通紙（循環反転搬送）された記録紙Ｐの第２面（裏面）の先端部Ｐａとの間の転写材搬送間隔を、例えば１５ｍｓとし、図１６に実線で示す第１面（表面）のみ（または第２面（裏面）のみ（不図示））が連続して画像形成される際の、先の記録紙Ｐの後端部Ｐｂと後の記録紙Ｐの先端部Ｐａとの間の転写材搬送間隔、例えば１０ｍｓ、よりも長くなるようにタイミングローラ２３を制御し、その間に前記保持部材ＨＧの位置を移動させて、定着ベルト２７を押圧し、ベルトニップ部Ｎａの押圧力を大きくして裏面の光沢度を上げるものである。
【０１０９】
該保持部材ＨＧの位置の移動の変更は、保持部材ＨＧとバネ受けＳＰＡ４との間に設けられる押圧バネＳＰａ４と、保持部材ＨＧの上部に設けられる偏芯カムＨＣ４の回転により行われる。偏芯カム駆動モータＭａの回転を受けて、減速機構ＧＫを通して偏芯カムＨＣ４に設けられる偏芯軸Ｊａ４を回転駆動し、偏芯カムＨＣ４の回転が行われる。偏芯カムＨＣ４が、図１６に矢印で示す時計方向へ回転されると、バネ受けＳＰＡ４が下側へ押し下げられて位置を移動され、押圧バネＳＰａ４がバネ受けＳＰＡ４を押圧（加圧）し、補助加圧パッドＨＰを定着ベルト２７を介して加圧ローラ１７ｂに押圧（加圧）するものである。この際、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に、ベルトニップ部Ｎａへの押圧力（加圧圧力）が大きくなる方向を移動方向として偏芯カムＨＣ４を回転させて保持部材ＨＧを下方に移動させる。これにより、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時のベルトニップ部の定着圧力（定着荷重）の変更が短時間で行われると共に、また図２０にて述べたように、定着時の定着荷重（定着時の加圧圧力（押圧力））が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【０１１０】
上記により、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時のベルトニップ部の定着圧力（定着荷重）の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【０１１１】
また図１７または前述した図５によれば、本発明の定着装置１７は、図１３および図９にて述べた構成である。図１７に一点鎖線で示す第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の、第１面（表面）の転写材としての記録紙Ｐの後端部Ｐｂと反転通紙（循環反転搬送）された記録紙Ｐの第２面（裏面）の先端部Ｐａとの間の転写材搬送間隔を、例えば１５ｍｓとし、図１７に実線で示す第１面（表面）のみ（または第２面（裏面）のみ（不図示））が連続して画像形成される際の、先の記録紙Ｐの後端部Ｐｂと後の記録紙Ｐの先端部Ｐａとの間の転写材搬送間隔、例えば１０ｍｓ、よりも長くなるようにタイミングローラ２３を制御し、その間に加圧ローラ１７ｂの位置を移動させて、定着ベルト２７を固定板ＫＰａに押圧し、ベルトニップ部Ｎａの押圧力を大きくして裏面の光沢度を上げるものである。
【０１１２】
該加圧ローラ１７ｂの位置の移動の変更は、例えば図５にて説明した押圧バネＳＰａ２と押圧バネ固定部材としてのバネ受けＳＰＡ２とを用いて行われ、押圧バネＳＰａ２が加圧ローラ１７ｂの両端部を押圧（加圧）し、加圧ローラ１７ｂが固定板ＫＰａに定着ベルト２７を押圧（加圧）、移動させるものである。この際、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に、ベルトニップ部Ｎａでの定着ベルト２７の移動方向幅（記録紙のベルトニップ部通紙時間）が大きくなる方向を移動方向として加圧ローラ１７ｂを上方に移動させる。これにより、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時のベルトニップ部での押圧力の変更が短時間で行われると共に、また図２０にて述べたように、定着時の定着荷重（定着時の加圧圧力（押圧力））が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と循環反転搬送（反転通紙）した２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【０１１３】
上記により、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時のベルトニップ部の幅の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【０１１４】
また図１８または前述した図１１によれば、本発明の定着装置１７は、図１３および図１０にて述べた構成である。図１８に一点鎖線で示す第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の、第１面（表面）の転写材としての記録紙Ｐの後端部Ｐｂと反転通紙（循環反転搬送）された記録紙Ｐの第２面（裏面）の先端部Ｐａとの間の転写材搬送間隔を、例えば１５ｍｓとし、図１８に実線で示す第１面（表面）のみ（または第２面（裏面）のみ（不図示））が連続して画像形成される際の、先の記録紙Ｐの後端部Ｐｂと後の記録紙Ｐの先端部Ｐａとの間の転写材搬送間隔、例えば１０ｍｓ、よりも長くなるようにタイミングローラ２３を制御し、その間にテンション補助ローラＴＲａの位置を移動させて、ベルトニップ部Ｎａの押圧力を大きくして裏面の光沢度を上げるものである。
【０１１５】
該テンション補助ローラＴＲａの位置の移動の変更は、例えば図１１にて説明した押圧バネＳＰａ５と押圧バネ固定部材としてのバネ受けＳＰＡ５とを用いて行われ、押圧バネＳＰａ５がテンション補助ローラＴＲａの両端部を押圧（加圧）し、テンション補助ローラＴＲａが定着ベルト２７を押圧（加圧）、移動させるものである。この際、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に、ベルトニップ部Ｎａでの定着ベルト２７の移動方向幅（記録紙のベルトニップ部通紙時間）が大きくなる方向を移動方向としてテンション補助ローラＴＲａを右下方に移動させる。これにより、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時のベルトニップ部の定着圧力（定着荷重）の変更が短時間で行われると共に、また図２０にて述べたように、定着時の定着荷重（定着時の加圧圧力（押圧力））が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と循環反転搬送（反転通紙）した２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【０１１６】
なお上記において、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着ベルト２７への定着時の押圧力（加圧圧力）の変更を、発熱ローラ１７ａを図１８に一点鎖線で示す右方向の位置へ移動し、張架ローラ１７ｃと発熱ローラ１７ａとの間を広げてベルトニップ部Ｎａの幅を大きくするようにすることも可能である。また、張架ローラ１７ｃを左方向へ位置を移動し、ベルトニップ部Ｎａの幅を大きくするようにしてもよい。
【０１１７】
上記により、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時のベルトニップ部の幅の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【０１１８】
図１９によれば、本発明の第２の例の定着装置１７Ａは、図１２で述べた構成と同様である。
【０１１９】
上記定着装置１７Ａにおいても、冒頭にて述べたように、図１にて述べた画像形成装置における両面コピー時に、２回定着器を通過する表面（第１面）の方が、１回しか定着器を通過しない裏面（第２面）よりも光沢度が高くなってしまい、表面（２回定着器を通過する面、第１面）と裏面（１回しか定着器を通過しない面、第２面）とで光沢度が異なってしまう。特に、ステイプル等で綴じたときにページの左右で光沢度が異なることになり、好ましくない。前述したように、この表裏の光沢度差は概ね１０〜２５°の範囲である。
【０１２０】
第２の例の定着装置１７Ａにおける本発明により表裏の光沢度差が解消される前提は、図２０および図２２にて前述したと同様である。この第２の例の定着装置１７Ａにおける表裏の光沢度差を解消するための本発明の定着方法について、図１９、及び前述した図３、図２１および図２２により以下に説明する。
【０１２１】
図１９または前述した図３、図１２によれば、本発明の定着装置１７Ａは、図１２で述べた構成であり、図１９に一点鎖線で示す第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の、第１面（表面）の転写材としての記録紙Ｐの後端部Ｐｂと反転通紙（循環反転搬送）された記録紙Ｐの第２面（裏面）の先端部Ｐａとの間の転写材搬送間隔を、例えば１５ｍｓとし、図１９に実線で示す第１面（表面）のみ（または第２面（裏面）のみ（不図示））が連続して画像形成される際の、先の記録紙Ｐの後端部Ｐｂと後の記録紙Ｐの先端部Ｐａとの間の転写材搬送間隔、例えば１０ｍｓ、よりも長くなるようにタイミングローラ２３を制御し、その間に押圧手段のバネ受けＳＰＡ１の位置を移動させて、加圧ローラ１７ｂを押圧し、定着ニップ部Ｎｂの押圧力を大きくして裏面の光沢度を上げるものである。
【０１２２】
該押圧手段による位置の移動の変更は、図３に示す押圧バネＳＰａ１と押圧バネ固定部材としてのバネ受けＳＰＡ１とを用いて行われ、押圧バネＳＰａ１が加圧ローラ１７ｂの両端部を押圧（加圧）し、加圧ローラ１７ｂを加熱ローラ１７ｄに押圧（加圧）させるものである。この際、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際に、定着ニップ部Ｎｂでの押圧力が大きくなる方向を移動方向として加圧ローラ１７ｂを上方に移動させる。これにより、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着ニップ部での押圧力の変更が短時間で行われると共に、また図２０にて述べたように、定着時の定着荷重（定着時の加圧圧力（押圧力））が大きいほど定着後のトナー画像の光沢度は高光沢となり、図２２にて述べたように、表面のトナー画像（トナー像）の１面目の１回目と循環反転搬送（反転通紙）した２回目の定着時の光沢度とを加えたものは、循環反転搬送（反転通紙）した２面目の裏面のトナー画像（トナー像）を１回で定着したときの光沢度と略等しくなる。
【０１２３】
上記により、第１面（表面）の画像形成から第２面（裏面）の画像形成に移行する際の定着時のベルトニップ部の幅の変更が短時間でできるので、生産性の低下が発生しない。また、十分な定着性が得られる温度設定ができるので、定着性が低下することはない。
【０１２４】
【発明の効果】
上記各本発明によれば、生産性が落ちることなく、また定着性が悪くなることが防止され、１回定着時（表面定着時）と２回定着時（裏面定着時）との表裏の光沢度差が抑止される定着装置を有する画像形成装置の提供が可能となる。
【図面の簡単な説明】
【図１】本発明に係わる定着装置を用いる画像形成装置の一実施形態を示すカラー画像形成装置の断面構成図である。
【図２】本発明に係わる第１の例の定着装置を示す概要断面構成図である。
【図３】第１面の定着時および第２面の定着時に用いられる押圧手段を示す図である。
【図４】図２の定着装置における第１面の定着時および第２面の定着時に用いられるベルトニップ幅変更の第１の例を示す図である。
【図５】第１面（表面）の定着時および第２面（裏面）の定着時に用いられるベルトニップ幅変更手段を示す図である。
【図６】図２の定着装置における第１面の定着時および第２面の定着時に用いられるベルトニップ幅変更の第２の例を示す図である。
【図７】第１面（表面）の定着時および第２面（裏面）の定着時に用いられるベルトニップ幅変更手段を示す図である。
【図８】図２の定着装置における第１面の定着時および第２面の定着時に用いられる圧力変更手段の第１の例を示す図である。
【図９】図２の定着装置におけるる第１面の定着時および第２面の定着時に用いられる圧力変更手段の第２の例を示す図である。
【図１０】図２の定着装置における第１面の定着時および第２面の定着時に用いられる圧力変更手段の第３の例を示す図である。
【図１１】第１面（表面）の定着時および第２面（裏面）の定着時に用いられる圧力変更手段を示す図である。
【図１２】本発明に係わる第２の例の定着装置を示す概要断面構成図である。
【図１３】本発明に係わる第１の例の定着装置における第１面の画像形成から第２面の画像形成に移行する際の転写材搬送間隔を示す図である。
【図１４】図１３の定着装置における第１面の画像形成から第２面の画像形成に移行する際に用いられるベルトニップ幅変更の第１の例を示す図である。
【図１５】図１３の定着装置における第１面の画像形成から第２面の画像形成に移行する際に用いられるベルトニップ幅変更の第２の例を示す図である。
【図１６】図１３の定着装置における第１面の画像形成から第２面の画像形成に移行する際に用いられる圧力変更手段の第１の例を示す図である。
【図１７】図１３の定着装置における第１面の画像形成から第２面の画像形成に移行する際に用いられる圧力変更手段の第２の例を示す図である。
【図１８】図１３の定着装置における第１面の画像形成から第２面の画像形成に移行する際に用いられる圧力変更手段の第３の例を示す図である。
【図１９】本発明に係わる第２の例の定着装置における第１面の画像形成から第２面の画像形成に移行する際の転写材搬送間隔を示す図である。
【図２０】定着荷重と光沢度の関係を示す図である。
【図２１】記録紙のベルトニップ部通紙時間と光沢度の関係を示す図である。
【図２２】本発明による表裏の光沢度差を抑止した結果を示す図である。
【図２３】２回定着における光沢度の変化幅を示す図である。
【図２４】両面コピー時の表裏の光沢度差を示す図である。
【符号の説明】
１　感光体ドラム
２　帯電器
３　露光光学系
４　現像器
６　中間転写ベルト
７　１次転写ローラ
７Ａ　２次転写ローラ
１７　定着装置
１７ａ　発熱ローラ
１７ｂ　加圧ローラ
１７ｃ　張架ローラ
１７ｄ　加熱ローラ
２７　定着ベルト
１００　プロセスユニット
ＨＣ１，ＨＣ２，ＨＣ３，ＨＣ４，ＨＣ５　偏芯カム
ＨＧ　保持部材
ＨＰ　補助加圧パッド
ＨＬａ　ハロゲンランプ
ＨＲａ　補助ローラ
ＫＰａ　固定板
Ｎａ　ベルトニップ部
Ｎｂ　定着ニップ部
ＳＰａ１，ＳＰａ２，ＳＰａ３，ＳＰａ４，ＳＰａ５　押圧バネ
ＳＰＡ１，ＳＰＡ２，ＳＰＡ３，ＳＰＡ４，ＳＰＡ５　バネ受け
ＴＲａ　テンション補助ローラ
Ｐ　記録紙[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus such as a copier, a printer, and a facsimile, and more particularly, to an image forming apparatus having a belt type fixing device.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in electrophotographic image forming apparatuses such as copiers, printers, and facsimile machines, the demand for image quality has increased, and there has been a movement to increase or control the glossiness of an image by a fixing device of the image forming apparatus. Has been.
[0003]
Conventionally, as a fixing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, a heating rubber roller having an elastic layer and maintained at a predetermined temperature, and pressed against the heating rubber roller, 2. Description of the Related Art A heat roller fixing system in which a transfer material having an unfixed toner image formed thereon is heated while being nipped and conveyed by a pressure rubber roller having an elastic layer is often used.
[0004]
However, in this type of apparatus, the heat capacity of the heat generating rubber roller is large, so that the warm-up time is long, the temperature inside the elastic layer is high, and the life of the heat generating rubber roller is shortened.
[0005]
In addition, the demand for energy saving has increased, and the fixing unit has been developing a fixing device capable of obtaining as high a fixing performance as possible with the same power consumption. The movement of raising is seen.
[0006]
In addition, many color images have a large solid area, and many of the solid images are other than black. When a hard roller is used as the heating rubber roller and the pressure rubber roller, there is a problem that image quality is deteriorated because unevenness of gloss occurs according to unevenness of a transfer material (recording paper) and a toner layer.
[0007]
In order to solve these problems, an endless belt member (fixing belt) is used, a fixing belt is stretched by a plurality of roller members, and a heating element for heating the fixing belt is provided inside. A heating roller facing the heating roller and a roller member (pressure roller) facing the heating roller with the fixing belt interposed therebetween; a fixing nip portion between the heating roller and the pressure roller; and a fixing belt heated by the heating roller. An image forming apparatus using a fixing method for fixing a toner image (toner image) on recording paper by a belt nip formed by a pressure roller and a belt nip is disclosed in Japanese Patent Application Laid-Open No. H10-319772. .
[0008]
Further, a re-feeding mechanism (ADU mechanism) is provided in the image forming apparatus using the fixing belt, and after the toner image transferred to one surface of the transfer material is fixed by the fixing device, the toner image is formed on one surface. A double-sided image forming method has been adopted in which the fixed transfer material is circulated and inverted (reversed sheet passing) by a re-feeding mechanism, and the toner image transferred to the other surface of the transfer material is fixed again.
[0009]
Further, an image forming apparatus equipped with a post-processing device having a device for post-processing a transfer material having a toner image formed on both sides by stapling or the like after forming a double-sided image is also often used.
[0010]
[Problems to be solved by the invention]
However, the glossiness differs between the front surface (the surface that passes through the fixing device twice, the first surface) and the back surface (the surface that passes the fixing device only once, the second surface) during duplex copying in the image forming apparatus. Problems arise. In particular, when the sheets are stapled or the like, the glossiness differs between the left and right sides of the page, which is not preferable.
[0011]
This is because the glossiness of the front surface (first surface) that passes through the fixing device twice is higher than that of the back surface (second surface) that passes through the fixing device only once.
[0012]
However, as shown in FIG. 23, the width of change in the glossiness in the two-time fixing is, for example, 128 g / m 2 as a transfer material (recording paper). ² When the coated pressure (pressing force) at the nip between the upper roller (heating roller) and the lower roller (pressure roller) is 200 kPa and the fixing linear velocity is When the normal linear velocity (80 to 250 mm / s) is 1/2 (◆), when the applied pressure (pressing force) is 200 kPa and the fixing linear velocity is 1/3 of the normal linear velocity (■), When the pressure / pressure (pressing force) is 140 kPa and the fixing linear velocity is 1/3 of the normal linear velocity (▲), the gloss at the first fixing (first gloss, (°)) and the fixing at the second fixing As can be seen from the figure, the change width of the glossiness (second glossiness, (°)) between (1) and (2) indicates that the fixing is performed twice regardless of the first glossiness as the second glossiness increment (°). And the glossiness is generally improved by 10 to 25 °. Further, as shown in FIG. 24, the gloss difference between the front and back sides during duplex copying is, for example, a pressure of 139 kPa at a nip between an upper roller (heating roller) and a lower roller (pressure roller), and an upper roller temperature (heat generation). Roller temperature = fixing belt temperature) is 198 ° C., and the basis weight is 128 g / m ² When the coated paper (trade name: NK art paper) is used, the paper nip passing time (ms) of the recording paper with respect to the temperature change of the upper roller (heating roller) is a nip time equivalent to a 1/2 linear velocity. Glossiness (°, filled triangle) at the time of fixing once on one side with (fixing linear speed is 1/2 the linear speed of normal linear speed (80 to 250 mm / s) the paper passing time in the belt nip portion of recording paper) Glossiness increase (= glossiness difference (°): open triangle) with respect to the temperature difference (°) between the lower roller (pressure roller) and the lower roller (pressure roller), and the lower roller temperature ( The paper passing time (ms) of the recording paper in the belt nip portion with respect to the change of the pressure roller temperature is 1/3 linear speed equivalent nip time (fixing linear speed is 1/3 of normal linear speed (80 to 250 mm / s)). Glossiness at the time of fixing once on one side with the recording paper at the belt nip at the linear velocity The gloss difference (°) between the front and back sides during duplex copying of °, filled circles) and the gloss increase (= gloss difference (°): white circles) due to reverse passing as shown in the figure. The gloss difference between the front and back is approximately 10 to 25 °. That is, the gloss difference between the first time (at the time of the first fixing) and the second time (at the time of the second fixing) is approximately in the range of 10 to 25 °.
[0013]
Possible measures to eliminate the difference in gloss between the first time (at the time of the first fixing) and the second time (at the time of the second fixing) include:
(1) The fixing temperature is not lowered at the time of the second fixing to improve the glossiness
(2) Increase the temperature difference between the upper roller (heating roller) and the lower roller (pressure roller) (lower the temperature of the lower roller);
Although measures such as are taken,
In the case of (1), it takes time to lower the temperature of the fixing device, and there is a problem that productivity is lowered. Further, in the case of (2), the heat supply from the lower roller (pressure roller) is reduced, so that there is a problem that the fixing property is deteriorated.
[0014]
The present invention solves the above-mentioned problems, does not reduce productivity, and prevents deterioration of fixability, and can be used for fixing once (at the time of surface fixing) and fixing twice (at the time of backside fixing). An object of the present invention is to provide an image forming apparatus having a fixing device that suppresses a difference in glossiness between front and back sides.
[0015]
[Means for Solving the Problems]
The object of the present invention is achieved by the following configurations.
[0016]
(1) An endless belt member, a first roller member that stretches one of the inner peripheral surfaces of the belt member, and a second roller member that contacts the first roller member with the belt member interposed therebetween. And a third roller member provided in parallel with and separated from the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member of the belt member, An image forming apparatus having a fixing device for fixing the toner image above, wherein the fixing device is provided with pressing means for pressing the second roller member against the first roller member via the belt member; After the image is formed on the first surface of the transfer material and the toner image on the first surface of the transfer material is fixed through the fixing device, the transfer material passed through the fixing device is circulated and conveyed, and the image is formed on the second surface of the transfer material. Form the transfer material through the fixing device Fixing the toner image on the second surface and fixing the toner images on both the first surface and the second surface of the transfer material, wherein the pressing means is used when the first surface is fixed and when the second surface is fixed. An image forming apparatus having a fixing device, wherein the pressing force applied to the second roller member is changed by the fixing device.
[0017]
(2) An endless belt member, a first roller member that stretches one of the inner peripheral surfaces of the belt member, and a second roller member that contacts the first roller member with the belt member interposed therebetween. And a third roller member provided in parallel with and separated from the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member, and Forming a fixing nip portion between the first roller member and the second roller member, and forming a belt nip portion between the belt member and the second roller member; In an image forming apparatus having a fixing device for fixing a toner image on a transfer material by a nip portion and the belt nip portion, a belt nip width change for changing a width of the belt nip portion in a moving direction of the belt member is provided to the fixing device. Provide means After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. An image is formed on the transfer material, and the toner image on the second surface of the transfer material is fixed through the fixing device, and the toner images on both the first surface and the second surface of the transfer material are fixed. An image forming apparatus having a fixing device, wherein the belt nip width changing means changes the width of the belt member in the moving direction between the time of fixing the second surface and the time of fixing the second surface.
[0018]
(3) An endless belt member, a first roller member that stretches one of the inner peripheral surfaces of the belt member, and a second roller member that contacts the first roller member with the belt member interposed therebetween. And a third roller member provided in parallel with and separated from the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member, and Forming a fixing nip portion between the first roller member and the second roller member, and forming a belt nip portion between the belt member and the second roller member; In an image forming apparatus having a fixing device for fixing a toner image on a transfer material by a nip portion and the belt nip portion, a pressure for changing a pressure of the fixing device to contact the second roller member of the belt nip portion is provided. Change means is provided, After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material that has passed through the fixing device is circulated and conveyed to the second surface of the transfer material. An image is formed on the transfer material, and the toner image on the second surface of the transfer material is fixed through the fixing device, and the toner images on both the first surface and the second surface of the transfer material are fixed. An image forming apparatus having a fixing device, wherein the pressure changing means changes the pressure at which the second roller member of the belt nip portion is brought into contact with the second roller member during the fixing of the second surface (third invention) .
[0019]
(4) A first roller member having a heating means and made of a metal core and an elastic layer, and a second roller made of a metal core and an elastic layer provided opposite to the first roller member. And an image forming apparatus having a fixing device for fixing a toner image on a transfer material, wherein the fixing device is provided with pressing means for pressing the second roller member against the first roller member. After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material passing through the fixing device is circulated and conveyed to the second surface of the transfer material. Forming an image on the surface, fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material. To the second roller member by the pressing means at the time of fixing the second surface. An image forming apparatus having a fixing device, characterized in that to change the pressing force (the fourth invention).
[0020]
(5) An endless belt member, a first roller member that stretches one of the inner peripheral surfaces of the belt member, and a second roller member that contacts the first roller member with the belt member interposed therebetween. And a third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surface of the belt member, and fixing the toner image on the transfer material. In the image forming apparatus having a fixing device, a pressing unit including a pressing spring for pressing the second roller member against the first roller member and a pressing spring fixing member is provided in the fixing device, and the transfer material is conveyed. A transfer material conveyance interval changing unit for changing an interval is provided, an image is formed on the first surface of the transfer material, and the toner image on the first surface of the transfer material is fixed through the fixing device. Is circulated and inverted and Forming an image on the second surface of the transfer material, fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material; The transfer material transport interval when shifting from one-side image formation to the second surface image formation is made longer than the transfer material transport interval when the first surface or the second surface is continuously formed. An image forming apparatus having a fixing device, wherein a pressing spring fixing member of the pressing means is moved during this time (a fifth invention).
[0021]
(6) An endless belt member, a first roller member that stretches one of the inner peripheral surfaces of the belt member, and a second roller member that contacts the first roller member with the belt member interposed therebetween. And a third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member, wherein the third roller member is provided with the belt member interposed therebetween. Forming a fixing nip portion between the first roller member and the second roller member; and forming a belt nip portion between the belt member and the second roller member to form the fixing nip portion. And an image forming apparatus having a fixing device for fixing a toner image on a transfer material by the belt nip portion, wherein the fixing device is provided with a moving means for moving a position of the second roller member, and a transfer material transfer interval is provided. Change transcription A transfer interval changing unit is provided, an image is formed on the first surface of the transfer material, and the toner image on the first surface of the transfer material is fixed through the fixing device. An image is formed on the second surface of the transfer material, the toner image on the second surface of the transfer material is fixed through the fixing device, and the toner images on both the first surface and the second surface of the transfer material are fixed. The transfer material conveyance interval at the time of transition from the first surface image formation to the second surface image formation is longer than the transfer material conveyance interval when the first surface or the second surface is continuously formed. An image forming apparatus having a fixing device, wherein the position of the second roller member is moved by a moving unit of the fixing device during the period (sixth invention).
[0022]
(7) An endless belt member, a first roller member that stretches one of the inner peripheral surfaces of the belt member, and a second roller member that contacts the first roller member with the belt member interposed therebetween. And a third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member, wherein the third roller member is provided with the belt member interposed therebetween. Forming a fixing nip portion between the first roller member and the second roller member; and forming a belt nip portion between the belt member and the second roller member to form the fixing nip portion. And an image forming apparatus having a fixing device for fixing a toner image on a transfer material by the belt nip portion, wherein the fixing device includes an auxiliary roller member around which a belt member for forming the belt nip portion is wound. , Roll A transfer material conveyance interval changing unit for changing the material conveyance interval is provided, an image is formed on the first surface of the transfer material, and the toner image on the first surface of the transfer material is fixed through the fixing device, and then passes through the fixing device. The transfer material is circulated and conveyed to form an image on the second surface of the transfer material, the toner image on the second surface of the transfer material is fixed through the fixing device, and both the first and second surfaces of the transfer material are fixed. The transfer material conveyance interval when the image forming apparatus shifts from the image forming operation on the first surface to the image forming operation on the second surface is performed, and the image is continuously formed on the first surface or the second surface. An image forming apparatus having a fixing device, wherein the auxiliary roller member of the fixing device is moved during the transfer material conveyance interval to be longer than the transfer material conveyance interval (seventh invention).
[0023]
(8) An endless belt member, a first roller member that stretches one of the inner peripheral surfaces of the belt member, and a second roller member that contacts the first roller member with the belt member interposed therebetween. And a third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member, wherein the third roller member is provided with the belt member interposed therebetween. Forming a fixing nip portion between the first roller member and the second roller member; and forming a belt nip portion between the belt member and the second roller member to form the fixing nip portion. And an image forming apparatus having a fixing device for fixing a toner image on a transfer material by the belt nip portion, wherein the belt for changing a pressure of the fixing device to contact a second roller member of the belt nip portion is provided. Slide the inner surface of the member Transfer member for changing the transfer material transfer interval, provided with a pressure changing means including a sliding member that performs sliding and a sliding auxiliary member that presses the sliding member against the second roller member via the belt member. A transfer interval changing unit is provided, an image is formed on the first surface of the transfer material, and the toner image on the first surface of the transfer material is fixed through the fixing device. An image is formed on the second surface of the transfer material, the toner image on the second surface of the transfer material is fixed through the fixing device, and the toner images on both the first surface and the second surface of the transfer material are fixed. The transfer material conveyance interval at the time of shifting from the image formation of the first surface to the image formation of the second surface is set as the transfer material conveyance interval at the time when the first surface or the second surface is continuously image-formed. Longer, during which the sliding aid of the pressure changing means An image forming apparatus having a fixing apparatus characterized by moving the timber (eighth invention).
[0024]
(9) An endless belt member, a first roller member that stretches one of the inner peripheral surfaces of the belt member, and a second roller member that contacts the first roller member with the belt member interposed therebetween. And a third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member, wherein the third roller member is provided with the belt member interposed therebetween. Forming a fixing nip portion between the first roller member and the second roller member; and forming a belt nip portion between the belt member and the second roller member to form the fixing nip portion. And an image forming apparatus having a fixing device for fixing a toner image on a transfer material by the belt nip portion, wherein the fixing device is provided with a fixing member facing the second roller member with the belt nip portion interposed therebetween. Pressing spring and pressing A pressure change means for the second roller member comprising a spring fixing member; and a transfer material transfer interval changing means for changing a transfer material transfer interval, and forming an image on the first surface of the transfer material. After fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material passing through the fixing device is circulated and inverted to form an image on the second surface of the transfer material, and the second material of the transfer material is passed through the fixing device. Fixing the toner image on the first surface and fixing the toner image on both surfaces of the first and second surfaces of the transfer material. When the image formation on the first surface is shifted to the image formation on the second surface, The transfer material transfer interval is made longer than the transfer material transfer interval when the first surface or the second surface is continuously image-formed, and the pressing spring of the pressure changing means of the second roller member during that time. A fixing device for moving a fixing member. An image forming apparatus having (ninth invention).
[0025]
(10) An endless belt member, a first roller member that stretches one of the inner peripheral surfaces of the belt member, and a second roller member that contacts the first roller member with the belt member interposed therebetween. And a third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member, wherein the third roller member is provided with the belt member interposed therebetween. Forming a fixing nip portion between the first roller member and the second roller member; and forming a belt nip portion between the belt member and the second roller member to form the fixing nip portion. And an image forming apparatus having a fixing device for fixing a toner image on a transfer material by the belt nip portion, wherein the fixing device is provided with a tension auxiliary roller for applying tension to the belt member, and the transfer material conveyance interval is reduced. A transfer material conveyance interval changing unit is further provided to form an image on the first surface of the transfer material, fix the toner image on the first surface of the transfer material through the fixing device, and circulate the transfer material passing through the fixing device. The image is formed on the second surface of the transfer material by reversing and conveying, and the toner image on the second surface of the transfer material is fixed through the fixing device, and the toner images on both surfaces of the first and second surfaces of the transfer material are formed. The transfer material conveyance interval when the image is transferred from the first surface image formation to the second surface image formation is set when the first surface or the second surface is continuously formed. An image forming apparatus having a fixing device, wherein the tension assisting roller of the fixing device is moved during the interval longer than a transfer material conveyance interval (a tenth invention).
[0026]
(11) A first roller member having a heating means and made of a metal core and an elastic layer, and a second roller made of a metal core and an elastic layer provided opposite to the first roller member. An image forming apparatus having a fixing device for fixing a toner image on a transfer material, wherein the fixing device includes a pressing spring and a pressing spring fixing member, and the second roller member is fixed to the first roller member. And a transfer member changing unit for changing a transfer member transfer interval, forming an image on the first surface of the transfer material, and forming a first surface of the transfer material through the fixing device. After fixing the toner image, the transfer material passed through the fixing device is circulated and conveyed to form an image on the second surface of the transfer material, and the toner image on the second surface of the transfer material is fixed through the fixing device. , Both sides of the first and second sides of the transfer material The toner image is fixed, and the transfer material conveyance interval when shifting from the image formation on the first surface to the image formation on the second surface is set such that the image is continuously formed on the first surface or the second surface. An image forming apparatus having a fixing device, wherein the pressing spring fixing member of the pressing means is moved during the transfer material transfer interval when the transfer material is transported (an eleventh invention).
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope.
[0028]
An image forming process and each mechanism of an embodiment of an image forming apparatus using a fixing device according to the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of a color image forming apparatus showing an embodiment of an image forming apparatus using a fixing device according to the present invention, and FIG. 2 is a schematic diagram showing a first example of a fixing device according to the present invention. FIG. 3 is a cross-sectional configuration diagram, FIG. 3 is a diagram showing pressing means used at the time of fixing the first surface (front surface) and at the time of fixing the second surface (back surface), and FIG. FIGS. 5A and 5B are diagrams illustrating a first example of a belt nip width change used at the time of fixing the first surface (front surface) and the time of fixing the second surface (back surface). FIGS. FIG. 6 is a diagram showing a belt nip width changing means used at the time of fixing the two surfaces (back surface). FIG. 6 shows the fixing device of FIG. 2 at the time of fixing the first surface (front surface) and at the time of fixing the second surface (back surface). FIG. 7 is a view showing a second example of changing the belt nip width used, and FIG. FIG. 8 is a diagram showing a belt nip width changing means used at the time of fixing of the first surface (front surface) and at the time of fixing of the first surface (front surface) in the fixing device of FIG. FIG. 9 is a diagram illustrating a first example of a pressure changing unit used at the time of fixing the (back surface), and FIG. 9 is a diagram illustrating a state of fixing the first surface (front surface) and the second surface (back surface) in the fixing device of FIG. FIG. 10 is a diagram illustrating a second example of a pressure changing unit used at the time of fixing, and FIG. 10 is a diagram illustrating pressures used at the time of fixing the first surface (front surface) and at the time of fixing the second surface (back surface) in the fixing device of FIG. FIG. 11 is a diagram illustrating a third example of the changing unit, and FIG. 11 is a diagram illustrating a pressure changing unit used at the time of fixing the first surface (front surface) and the time of fixing the second surface (back surface). FIG. 13 is a schematic cross-sectional configuration diagram showing a second example of a fixing device according to the present invention. FIG. 14 is a diagram showing a transfer material conveyance interval when the image forming apparatus shifts from the image formation on the first surface (front surface) to the image formation on the second surface (back surface) in the fixing device of the first example relating to the brightness. FIG. 15 is a diagram illustrating a first example of a belt nip width change used when shifting from image formation on the first surface (front surface) to image formation on the second surface (back surface) in the fixing device of No. 13; FIG. 16 is a diagram illustrating a second example of changing the belt nip width used when shifting from image formation on the first surface (front surface) to image formation on the second surface (back surface) in the fixing device in FIG. 13; FIG. 17 is a diagram showing a first example of a pressure changing unit used when shifting from image formation on the first surface (front surface) to image formation on the second surface (back surface) in the fixing device in FIG. 13; 13, the image formation on the first surface (front surface) to the second surface (back surface) in the fixing device of FIG. FIG. 18 is a diagram illustrating a second example of a pressure changing unit used when shifting to image formation. FIG. 18 illustrates a state in which the first surface (front surface) of the fixing device illustrated in FIG. FIG. 19 is a diagram illustrating a third example of a pressure changing unit used when shifting to image formation. FIG. 19 is a diagram illustrating a first example of a fixing device according to a second example of the present invention. FIG. 20 is a diagram showing a transfer material conveyance interval when shifting to image formation on two sides (back side), FIG. 20 is a diagram showing a relationship between a fixing load and glossiness, and FIG. 21 is a belt nip portion of a recording paper FIG. 22 is a diagram illustrating the relationship between the sheet passing time and the glossiness, and FIG. 22 is a diagram illustrating the result of suppressing the gloss difference between the front and back sides according to the present invention. In each example of the fixing device, members having the same function and structure are denoted by the same reference numerals.
[0029]
According to FIG. 1, the image forming apparatus GS includes an image forming apparatus main body GH and an image reading device SC provided on an upper portion of the image forming apparatus main body GH.
[0030]
The image forming apparatus main body GH is called a tandem-type color image forming apparatus, and arranges image forming units that form yellow, magenta, cyan, and black color toner images along the moving direction of the intermediate transfer member, The color toner images formed on the image carriers of the respective image forming units are multiplex-transferred onto the intermediate transfer member, superimposed, and then collectively transferred onto a transfer material.
[0031]
In the figure, a document image placed on an image reading device SC disposed above an image forming apparatus main body GH is scanned and exposed by an optical system, read by a line image sensor CCD, and photoelectrically converted by the line image sensor CCD. The processed analog signal is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit, and then sends an image data signal to an exposure optical system 3 as image writing means.
[0032]
Further, in the figure, four sets of processes for forming an image for each color of yellow (Y), magenta (M), cyan (C) and black (K) are provided on the peripheral portion of the intermediate transfer belt 6 as an intermediate transfer member. The units 100 are arranged in a vertical direction along the intermediate transfer belt 6 with respect to the rotation direction of the intermediate transfer belt 6 in the vertical direction indicated by the arrow in the figure as a unit for forming a color toner image, and Y, M, C, They are arranged in the order of K.
[0033]
Each of the four process units 100 has a common structure, and includes a photosensitive drum 1 serving as an image carrier, a charger 2 serving as a charging unit, an exposure optical system 3 serving as an image writing unit, and a developing unit. It comprises a developing device 4 as a means and a photoconductor cleaning device 190 as an image carrier cleaning means.
[0034]
The photoconductor drum 1 serving as an image carrier has a layer thickness (film thickness) as a photoconductor layer thickness on an outer periphery of a cylindrical base formed of a metal member such as aluminum having an outer diameter of about 40 to 100 mm. A photoconductive layer of an organic photoconductor layer (OPC) of about 20 to 40 μm is formed. The photoconductor drum 1 is rotated at a linear velocity of, for example, about 80 to 280 mm / s by a power from a driving source (not shown) in a direction indicated by an arrow with the conductive layer grounded.
[0035]
Around the photoreceptor drum 1, an image forming unit including a set of a charger 2 as a charging unit, an exposure optical system 3 as an image writing unit, and a developing unit 4 as a developing unit is indicated by an arrow in the figure. The photosensitive drum 1 is arranged in the rotation direction shown in FIG.
[0036]
The charger 2 as a charging unit is attached to the photosensitive drum 1 in a direction perpendicular to the moving direction of the photosensitive drum 1 (a direction perpendicular to the paper surface in the drawing) so as to face and be close to the photosensitive drum 1. The charger 2 includes a discharge wire serving as a corona discharge electrode for applying a predetermined potential to the organic photoconductor layer of the photoconductor drum 1, and performs a charging operation by corona discharge having the same polarity as the toner (in this embodiment, negative charging). To apply a uniform potential to the photosensitive drum 1.
[0037]
The exposure optical system 3, which is an image writing unit, rotationally scans a laser beam emitted from a semiconductor laser (LD) light source (not shown) in a main scanning direction by a rotating polygon mirror (no sign), and outputs an fθ lens (no sign). ), The exposure (image writing) is performed on the photosensitive drum 1 by an electric signal corresponding to the image signal via a reflection mirror (no sign) or the like, and the photosensitive layer on the surface of the photosensitive drum 1 corresponds to the original image. An electrostatic latent image is formed.
[0038]
The developing device 4 as a developing means is a two-component developer of each color of yellow (Y), magenta (M), cyan (C) or black (K) charged to the same polarity as the charging polarity of the photosensitive drum 1. A developing roller 4a is provided, which is a developer carrying member formed of a cylindrical non-magnetic stainless steel or aluminum material having a thickness of 0.5 to 1 mm and an outer diameter of 15 to 25 mm. The developing roller 4a is kept out of contact with the photoconductor drum 1 by a contact roller (not shown) with a predetermined gap, for example, 100 to 1000 μm, so that the developing roller 4a rotates in the forward direction with respect to the rotation direction of the photoconductor drum 1. During development, a photosensitive drum is applied by applying a DC bias voltage of the same polarity as the toner (in the present embodiment, a negative polarity) or a DC bias voltage that superimposes an AC voltage on the developing roller 4a during development. The reversal development is performed on the exposed portion on No. 1.
[0039]
As the intermediate transfer belt 6 as an intermediate transfer body, a semiconductive endless (seamless) resin belt member having a volume resistivity of about 1E + 7 to 1E + 9Ω · cm and a surface resistivity of about 1E + 10 to 1E + 12Ω / □ is used. For example, a semiconductive resin film substrate having a thickness of 0.05 to 0.5 mm in which a conductive material is dispersed in an engineering plastic such as modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, or nylon alloy It is. As the base of the intermediate transfer belt 6, a semiconductive rubber belt having a thickness of 0.5 to 2.0 mm in which a conductive material is dispersed in silicon rubber or urethane rubber or the like can also be used. The intermediate transfer belt 6 is wound around a plurality of roller members including a tension roller 6a, and is supported rotatably in a vertical manner. It is also possible to use a drum-shaped intermediate transfer member.
[0040]
The primary transfer roller 7 as a first transfer unit for each color is made of a roller-shaped conductive member using foamed rubber such as silicon or urethane, and a photosensitive drum for each color with the intermediate transfer belt 6 interposed therebetween. 1 and presses the back surface of the intermediate transfer belt 6 to form a transfer area with the photosensitive drum 1. A DC constant current having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to the primary transfer roller 7 by constant current control, and a toner image on the photosensitive drum 1 is formed by a transfer electric field formed in a transfer area. Is transferred onto the intermediate transfer belt 6.
[0041]
The image forming step (image forming process) will be described below.
When the image recording is started, the photosensitive drum driving motor (not shown) is started to rotate the Y photosensitive drum 1 in the direction shown by the arrow in the figure, and a potential is applied to the Y photosensitive drum 1 by the Y charger 2. . After a potential is applied to the Y photosensitive drum 1, exposure (image writing) is performed by a first color signal, that is, an electric signal corresponding to Y image data by the Y exposure optical system 3, and the Y photosensitive drum 1 is exposed. An electrostatic latent image corresponding to a yellow (Y) image is formed on the body drum 1. This latent image is reversely developed by the Y developing device 4, and a toner image composed of yellow (Y) toner is formed on the Y photosensitive drum 1. The Y toner image formed on the Y photosensitive drum 1 is transferred onto the intermediate transfer belt 6 by a primary transfer roller 7 as a primary transfer unit.
[0042]
Next, a potential is applied to the M photosensitive drum 1 by the M charger 2. After a potential is applied to the M photoconductor drum 1, exposure (image writing) is performed by the M exposure optical system 3 using a first color signal, that is, an electric signal corresponding to M image data, and the M photoconductor drum 1 is exposed. An electrostatic latent image corresponding to a magenta (M) image is formed on the body drum 1. This latent image is reversely developed by the M developing device 4 to form a toner image composed of yellow (M) toner on the M photosensitive drum 1. The M toner image formed on the M photosensitive drum 1 is transferred onto the intermediate transfer belt 6 by superimposing the Y toner image by a primary transfer roller 7 as a primary transfer unit.
[0043]
By the same process, the toner image formed of cyan (C) toner formed on the photosensitive drum 1 of C and the toner image formed of black (K) toner formed on the photosensitive drum 1 of K are formed. The superposed color toner images formed of the Y, M, C, and K toners are sequentially formed on the intermediate transfer belt 6 so as to be superimposed on the intermediate transfer belt 6.
[0044]
The toner remaining on the peripheral surface of each photoconductor drum 1 after the transfer is cleaned by a photoconductor cleaning device 190 as an image carrier cleaning unit.
[0045]
On the other hand, the recording paper P as a transfer material stored in the paper feed cassettes 20A, 20B, and 20C is fed by a feed roller 21 and a paper feed roller 22A provided in the paper feed cassettes 20A, 20B, and 20C, respectively. Via the rollers 22B, 22C, 22D and the registration roller 23, the toner is conveyed to a secondary transfer roller 7A as a secondary transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied, and the secondary transfer is performed. In the transfer area of the roller 7A, the superposed color toner images (color images) formed on the intermediate transfer belt 6 are collectively transferred onto the recording paper P.
[0046]
The recording paper P to which the color image has been transferred is subjected to a fixing process by a fixing device 17 (or a fixing device 17A) described in detail later, is sandwiched by discharge rollers 24, and is placed on a discharge tray 25 outside the apparatus. You.
[0047]
After the color image is transferred onto the recording paper P by the secondary transfer roller 7A as the secondary transfer means, the intermediate transfer belt 6 from which the recording paper P is separated by the curvature is used as the intermediate transfer body as the intermediate transfer body cleaning means. The residual toner is removed by the cleaning device 190a.
[0048]
At the time of double-sided image formation, a color image (color toner image) is formed on one surface (first surface (front surface)), and the recording paper P discharged from the fixing device 17 (or the fixing device 17A) is branched by the branching unit 26. The sheet is diverged from the sheet discharge path, passes through a lower circulating paper path 27A that constitutes a sheet feeder, and is turned over by a reverse feeder path 27B, which is a refeed mechanism (ADU mechanism). After passing through the transport section 27C, they meet at the paper feed roller 22D. The recording paper P that has been reversely conveyed (circularly reversed conveyance) is conveyed again to the secondary transfer roller 7A via the timing roller 23 (transfer material conveyance interval changing means described in detail later), and the other surface of the recording paper P A color image (color toner image) is collectively transferred onto the (second surface (back surface)). The recording paper P to which the color image has been transferred is subjected to a fixing process by the fixing device 17, is sandwiched by the discharge rollers 24, and is placed on a discharge tray 25 outside the apparatus.
[0049]
On the other hand, after the color image is transferred onto the recording paper P by the secondary transfer roller 7A, the residual toner is removed from the intermediate transfer belt 6 from which the recording paper P is separated by the curvature by the intermediate transfer body cleaning means 8A.
[0050]
In the description of the image forming apparatus, color image formation has been described, but the case of forming a monochrome image is also included in the present invention.
[0051]
According to FIG. 2, the fixing device 17 of the first example of the present invention uses a fixing belt 27 as an endless belt member, uses a stretching roller 17c as a first roller member, and uses a stretching roller 17c as a second roller member. A pressure roller 17b is used, and as a third roller member, for example, a heat generating roller 17a having a halogen lamp HLa as a heating member therein is used, and one side end in the rotation direction of the fixing belt 27 (in the rotation direction). On the downstream side, the fixing belt 27 is stretched by a stretching roller 17c on one of the inner peripheral surfaces of the fixing belt 27, and the other end of the fixing belt 27 in the rotational direction (on the upstream side in the rotational direction, the fixing belt The fixing belt 27 is stretched by the heat-generating roller 17a on the other side of the inner peripheral surface of the fixing belt 27, and a pressure roller 17b is provided to abut the stretching roller 17c with the fixing belt 27 interposed therebetween. A belt nip Na (a portion for performing the first fixing step) is formed between the fixing belt 27 and the pressure roller 17b, and the tension roller 17c and the pressure roller 17b are A fixing nip Nb (a part for performing the second fixing step) is formed between the recording paper P and the recording paper P described in FIG. 1 by applying heat and pressure through the belt nip Na and the fixing nip Nb. This is to fix the toner image (color toner image) on the first surface (top surface) or the toner image (color toner image) on the second surface (back surface) by circulating reversal conveyance (reverse paper passing).
[0052]
The fixing belt 27 has a heat resistance of about 70 to 120 mm in inner diameter and about 20 to 80 μm in thickness as a base, for example, a metal belt using a nickel electroformed belt, or a polyimide or polyamide having a thickness of about 40 to 150 μm. The outer (outer peripheral surface) of the resin belt is coated with an insulating silicon rubber having a thickness of about 100 to 300 μm, and the surface thereof is coated with a PFA (perfluoroalkoxy) having a thickness of about 30 to 50 μm as a release layer. Is used.
[0053]
The stretching roller 17c is made of, for example, a cylindrical metal pipe 171c having a thickness of about 2 to 5 mm using STKM (carbon steel pipe for machine structure), and a silicon material on the outer peripheral surface of the metal pipe 171c. An elastic layer 172c made of a silicon rubber member having a thickness (thickness) of 3 to 10 mm and a rubber hardness of about 25 to 30 Hs (JIS, A rubber hardness), and a thickness of about 15 to 30 μm on the surface of the elastic layer 172 c A release layer 173c using a PFA (perfluoroalkoxy) tube is formed as a softened soft roller having an outer diameter of about 30 to 50 mm.
[0054]
As the pressure roller 17b, for example, a cylindrical metal pipe 171b having a thickness of about 2 to 5 mm using STKM (carbon steel pipe for machine structure), and, for example, a silicon material is used on the outer peripheral surface of the metal pipe 171b. A rubber roller layer 172b made of a slightly hard rubber layer having a thickness (thickness) of 1 to 5 mm and a rubber hardness of 40 to 70 Hs (JIS, A rubber hardness), and a thickness of 15 mm on the surface of the rubber roller layer 172b. A release roller 173b covering a PFA (perfluoroalkoxy) tube of about 50 μm and a release roller 173b are formed. Further, a halogen lamp HLa as a heating member may be provided inside the pressure roller 17b as indicated by a dotted line to heat the fixing belt 27.
[0055]
The heat generating roller 17a having a halogen lamp HLa therein is made of, for example, an aluminum material, and has a cylindrical metal pipe 171a having a thickness of about 1 to 2 mm and a thickness of about 15 to 50 μm covering the outer peripheral surface of the metal pipe 171a. And a roller member having an outer diameter of about 40 to 60 mm on which a release layer 173a made of a PFA (perfluoroalkoxy) tube is formed.
[0056]
A belt nip portion Na formed between the fixing belt 27 and the pressure roller 17b, and a fixing nip portion Nb formed between the stretching roller 17c as a soft roller and the pressure roller 17b as a soft roller. The toner image (or color toner image) on the first surface (front surface) on the recording paper P or the toner image (color toner image) on the second surface (back surface) after being circulated and inverted and conveyed (reverse paper passing) is converted into a toner image (or The color toner image) is fixed.
[0057]
Further, a contact or non-contact temperature sensor TS1 is provided between the heat generating roller 17a and the fixing belt 27 to control the temperature of the heat generating roller 17a and the fixing belt 27.
[0058]
In the fixing device 17, as described at the beginning, the surface (first surface) that passes through the fixing device twice during the double-sided copying in the image forming apparatus described with reference to FIG. 1 is fixed only once. The glossiness is higher than the back surface (second surface) that does not pass through the fixing device, and the front surface (the surface that passes through the fixing device twice, the first surface) and the back surface (the surface that passes the fixing device only once, the second surface) Surface) differs in glossiness. In particular, when the sheets are stapled or the like, the glossiness differs between the left and right sides of the page, which is not preferable. As described above, the gloss difference between the front and back surfaces is generally in the range of 10 to 25 °.
[0059]
Means of the present invention for eliminating the difference in gloss between the front and back sides will be described below. Before that, referring to FIGS. 20 to 22, the difference in gloss between the front and back sides is eliminated by the means of the present invention. The assumption will be described.
[0060]
First, fixing by means (pressing means) for changing the pressure (pressing force = pressing pressure) for pressing the second roller member against the first roller member according to the present invention for eliminating the gloss difference between the front and back sides. Means for changing the fixing load in the fixing nip portion at the time or the pressure (pressing force = pressing pressure) for pressing the second roller member against the first roller member via the belt member (pressure changing means) Belt nip at the time of fixing by means (pressure changing means) for changing the fixing load at the belt nip portion at the time of fusing and the pressure (pressing force = pressing pressure) contacting the second roller member of the belt nip portion FIG. 20 shows the relationship between the fixing load and the glossiness at the portion, and the load dependency of the glossiness is, for example, assuming that the temperature of the fixing belt is 185 ° C., the temperature of the lower roller (pressure roller) is 140 ° C. 128g / m ² As shown in the figure, when the coated paper (brand name: NK art paper) is used, the larger the fixing load (pressing pressure (pressing force) during fixing) at the time of fixing, the more the belt nip or the fixing nip. The glossiness of the toner image after fixing is high. There is a correlation between the glossiness at the fixing nip or the belt nip and the pressing pressure (fixing load) at the time of fixing, and when the pressing pressure (pressing force) is increased, the gloss becomes high, and the pressing pressure (pressing force) Is small, the gloss is low.
[0061]
Means for changing the width of the belt member in the belt nip in the moving direction (time for passing the recording paper through the belt nip) (belt nip width changing means) according to the present invention for eliminating the gloss difference between the front and back sides And the width of the belt nip by moving the position of the second roller member of the present invention (the width of the belt nip of the recording paper). FIG. 21 shows the relationship between the paper passing time (width of the belt nip) of the recording paper at the time of fixing by means (moving means) for changing the printing time (transfer means) and the glossiness. ) As coated paper for PPC (Oji Paper's coated paper for PPC, basis weight 100 g / m2) ² ), The recording paper passing time of the fixing nip portion is 28 ms, the temperature of the fixing belt is about 200 ° C., and the temperature of the lower roller (pressure roller) is 170 ° C. (solid black circle); The change width of the glossiness when the temperature of the lower roller (pressure roller) is 140 ° C. (open circle) and when the temperature of the lower roller (pressure roller) is 110 ° C. (filled triangle) is as follows: As can be seen from the figures, in any case, the glossiness of the toner image after fixing becomes higher as the paper passing time (width of the belt nip) at the time of fixing becomes longer. There is a correlation between the glossiness at the time of fixing and the width of the belt nip portion. When the width of the belt nip portion is large, the gloss becomes high, and when the width of the belt nip portion is small, the gloss becomes low.
[0062]
As a result of suppressing the gloss difference between the front and back sides according to the present invention, as shown in FIG. 22, the first fixing of only the first side (front side) or only the second side (back side) of the toner image (toner image) on the recording paper. The gloss level at the time of the second fixing of the toner image (toner image) (the gloss level difference in the range of approximately 10 to 25 ° described in FIG. 23 or FIG. 24) is indicated by hatching in a white frame bar graph. In the hatched bar graph, for example, a front surface toner image (toner image) is formed as the first surface, and then the sheet is reversed (circulation reversal conveyance) to change the pressing force (pressing pressure) of the present invention shown in FIG. Means (pressing means or pressure changing means) or means (belt nip width changing means or moving means) for increasing the belt nip width (recording paper passing time) of the present invention shown in FIG. Using reversal conveyance (reversing paper passing) As shown in FIG. 22, the glossiness when the toner image (toner image) on the second side (rear side) on the recording paper is fixed at one time is indicated by a hatched bar graph. The image obtained by adding the glossiness at the time of the first fixing of only the first surface of the image (image) and the glossiness at the time of the second fixing of the toner image (toner image) is subjected to circulating reversal conveyance (reversal paper passing). The glossiness when the toner image (toner image) on the back surface of the first surface is fixed at one time is substantially equal to the glossiness. In the case of using the pressing force (pressing pressure) changing means at the time of fixing shown in FIG. 20, the first time is a low fixing pressure (the glossiness is low at this time), and the second time is a high fixing pressure, so that both sides are almost the same. Glossiness. In the case of using the means for changing the width of the belt nip portion (the time for passing the recording paper through the belt nip portion) in FIG. 21, the width of the belt nip portion is set to be small (the glossiness at this time is low) at the first time. At the second time, by increasing the width of the belt nip portion, both sides have the same glossiness.
[0063]
Next, each fixing method of the present invention for eliminating the difference in glossiness between the front and back sides will be described below with reference to FIGS. 3 to 10 and FIGS. 2 and 20 to 22 described above.
[0064]
According to FIG. 2 or FIG. 3, the fixing device 17 of the present invention has the configuration described with reference to FIG. 2, and presses as shown in FIG. 3 between the time of fixing the first surface and the time of fixing the second surface. The pressing force (pressing pressure) of the pressing roller 17b to the stretching roller 17c during fixing is changed by means.
[0065]
The pressing force of the pressing roller 17b at the time of fixing by the pressing means is changed by rotation of the eccentric cam HC1 provided below the spring receiver SPA1 at both ends. In response to the rotation of the eccentric cam drive motor Ma1, the eccentric shaft Ja1 provided on the eccentric cam HC1 is rotationally driven through the speed reduction mechanism GK1, and the eccentric cam HC1 at both ends is rotated. When the eccentric cams HC1 at both ends are rotated clockwise as shown by arrows in FIG. 3, the spring receivers SPA1 at both ends are lifted upward to move the position, and the pressing springs SPA1 at both ends are pressed by the pressing roller. The rotary shaft Jt1 at both ends of the roller 17b is pressed (pressed), and the pressure roller 17b is pressed (pressed) against the tension roller 17c via the fixing belt 27. At this time, at the time of fixing the second surface (rear surface) which has been subjected to the circulating reversal conveyance (reverse paper passing), the pressing force to the pressure roller 17b at the time of fixing by the pressing means is applied to the pressing at the time of fixing the first surface (front surface). By performing the operation in a short time so as to be greater than the pressing force applied to the pressing roller 17b by the means, as described with reference to FIG. 20, the fixing load (pressing pressure (pressing force) during fixing) during fixing is reduced. As the value is larger, the glossiness of the toner image after fixing becomes higher. As described with reference to FIG. 22, the glossiness at the time of the first and second fixings of the first side of the surface toner image (toner image) is added. In this case, the glossiness when the toner image (toner image) on the back surface of the second surface that has been subjected to the circulation reversal conveyance (reversal paper passing) is fixed at one time is substantially equal.
[0066]
As described above, since the fixing pressure (fixing load) at the time of fixing can be changed in a short time, the productivity does not decrease. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0067]
Further, according to FIGS. 2, 4 and 5, the fixing device 17 of the present invention has the configuration described with reference to FIG. 5, the position of the pressure roller 17b is changed to the position shown by the dashed line in FIG. 4, and the width of the fixing belt 27 in the belt nip portion Na in the moving direction at the time of fixing (the belt of the recording paper). Nip section passing time).
[0068]
The change of the width of the belt nip Na in the moving direction of the fixing belt 27 by the belt nip width changing means is performed by the rotation of the eccentric cam HC2 provided below the spring receivers SPA2 at both ends. In response to the rotation of the eccentric cam drive motor Ma2, the eccentric shaft Ja2 provided on the eccentric cam HC2 is rotationally driven through the speed reduction mechanism GK2, and the eccentric cam HC2 at both ends is rotated. When the eccentric cams HC2 at both ends are rotated clockwise as indicated by arrows in FIG. 5, the spring receivers SPA2 at both ends are lifted upward and moved to positions, and the pressing springs SPA2 at both ends are pressed by the pressing roller. The rotating shafts Jt at both ends of the roller 17b are pressed (pressed), the pressing roller 17b is pressed (pressed) against the stretching roller 17c via the fixing belt 27, and the fixing belt 27 in the belt nip Na is moved. The direction width is also changed.
[0069]
At the time of fixing the second surface (back surface) that has been subjected to the circulating reversal conveyance (reversing paper passing), the width in the moving direction of the fixing belt 27 of the belt nip Na by the belt nip width changing means (the paper nip passing time of the recording paper) is The width of the belt nip Na in the direction of movement of the fixing belt 27 by the pressure roller 17b at the time of fixing the first surface (front surface) is set to be larger than the width of the recording paper in the belt nip. As a result, the width of the fixing belt in the moving direction in the belt nip portion at the time of fixing is changed in a short time, and as described with reference to FIG. The longer the nip portion paper passing time), the higher the glossiness of the toner image after fixing becomes, and as described with reference to FIG. 22, the first time of the first side of the toner image (toner image) on the front surface and the circulation reversal conveyance ( The value obtained by adding the glossiness at the time of the second fixing performed by the reversal paper feeding is the glossiness obtained by fixing the toner image (toner image) on the back surface of the second surface that has been subjected to the circulating reversal conveyance (the reverse paper feeding) at one time. Is approximately equal to
[0070]
As described above, the width of the belt nip portion can be changed in a short time at the time of fixing, so that productivity does not decrease. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0071]
6 or 7, as shown in FIG. 6, the fixing device 17 is provided with an auxiliary roller HRa as an auxiliary roller member around which a fixing belt 27 for forming a belt nip Na is stretched. The belt nip width changing means as shown in FIG. 7 changes the width of the belt nip Na in the moving direction of the fixing belt 27.
[0072]
Changing the width of the belt nip Na in the moving direction of the fixing belt 27 by the belt nip width changing means is performed by rotating the eccentric cam HC3 provided below the spring receivers SPA3 at both ends. In response to the rotation of the eccentric cam drive motor Ma3, the eccentric shaft Ja3 provided on the eccentric cam HC3 is rotationally driven through the speed reduction mechanism GK3, and the eccentric cam HC3 at both ends is rotated. When the eccentric cams HC3 at both ends are rotated clockwise as indicated by arrows in FIG. 7, the spring receivers SPA3 at both ends are moved downward by being pushed down, and the pressing springs SPA3 at both ends are moved by the auxiliary rollers. The rotation shaft Jt2 at both ends of HRa is pressed (pressed), and the auxiliary roller HRa moves to the position indicated by the dotted line in FIG. Thus, the amount of the fixing belt 27 wound around the pressure roller 17b, that is, the width of the belt nip Na in the moving direction of the fixing belt 27 is changed.
[0073]
At the time of fixing the second surface (back surface) that has been subjected to the circulating reversal conveyance (reversing paper passing), the width in the moving direction of the fixing belt 27 of the belt nip Na by the belt nip width changing means (the paper nip passing time of the recording paper) is The width of the belt nip portion Na on the first surface (front surface) in the direction of movement of the fixing belt 27 (paper passing time of the recording paper in the belt nip portion) is made larger. As a result, the width of the fixing belt in the moving direction in the belt nip portion at the time of fixing is changed in a short time, and as described with reference to FIG. The longer the nip portion paper passing time), the higher the glossiness of the toner image after fixing becomes, and as described in FIG. 22, the first and second fixing of the first side of the toner image (toner image) on the front surface The sum of the gloss and the gloss at the time is substantially equal to the gloss when the toner image (toner image) on the back surface of the second surface that has been subjected to the reversal conveyance (reverse paper feeding) is fixed at one time.
[0074]
As described above, the width of the belt nip portion can be changed in a short time at the time of fixing, so that productivity does not decrease. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0075]
According to FIG. 8, the fixing device 17 of the present invention has the configuration described with reference to FIG. 2, and the pressure changing means as shown in FIG. 8 is used for fixing the first surface and fixing the second surface. This changes the pressure (pressing force = pressing pressure) at which the belt nip Na comes into contact with the pressure roller 17b during fixing.
[0076]
The change of the pressure at which the belt nip Na comes into contact with the pressure roller 17b at the time of fixing by the pressure changing means is provided on the pressing spring SPa4 provided between the holding member HG and the spring receiver SPA4 and on the holding member HG. This is performed by rotation of the eccentric cam HC4. In response to the rotation of the eccentric cam drive motor Ma4, the eccentric shaft Ja4 provided on the eccentric cam HC4 is rotationally driven through the speed reduction mechanism GK4, and the eccentric cam HC4 is rotated. When the eccentric cam HC4 is rotated in the clockwise direction indicated by the arrow in FIG. 8, the spring receiver SPA4 is pushed down and moved to the position, and the pressing spring SPA4 presses (presses) the spring receiver SPA4, The auxiliary pressure pad HP is pressed (pressed) to the pressure roller 17 b via the fixing belt 27. At the time of fixing the second surface (reverse surface) that has been subjected to the circulating reversal conveyance (reversing paper passing), the pressure (pressing force = pressing pressure) contacting the pressure roller 17 b of the belt nip Na by the pressure changing means is applied to the first surface. The pressure is changed so as to be larger than the pressure (pressing force = pressing pressure) of the belt nip Na contacting the pressing roller 17b by the pressure changing means at the time of (front) fixing. Thereby, the pressing force applied to the belt nip Na during the fixing is changed in a short time, and the fixing load during the fixing (the pressing pressure (the pressing force) during the fixing) as described in FIG. Is larger, the glossiness of the toner image after fixing becomes higher. As described with reference to FIG. 22, the glossiness at the time of the first and second fixing of the first side of the toner image (toner image) on the surface is different. The added value becomes substantially equal to the glossiness when the toner image (toner image) on the back surface of the second surface subjected to the circulation reversal conveyance (reversal paper passing) is fixed at one time.
[0077]
As described above, the pressing force (fixing load) of the belt nip at the time of fixing can be changed in a short time, so that productivity does not decrease. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0078]
Further, as shown in FIG. 9, a fixing plate KPa, which is a fixing member facing the pressure roller 17b across the belt nip Na, is provided inside the fixing belt 27 in the fixing device 17, and for example, the belt nip shown in FIG. Using the pressing spring SPA2 described as the width changing means and the spring receiver SPA2 as the pressing spring fixing member, etc. as the pressure changing means, the pressing force of the pressing roller 17b on the fixing plate KPa at the belt nip Na is changed. This is performed by the pressure changing means, and as shown by the dashed line in the figure, the pressure roller 17b is pushed up from the lower side to the upper side, and the pressure roller 17b is pressed (pressed) against the fixing plate KPa via the fixing belt 27. You may. At this time, at the time of fixing the second surface (reverse surface) that has been subjected to the circulating reversal conveyance (reversing paper passing), the pressure (pressing force = pressing pressure) that comes into contact with the belt nip Na of the pressing roller 17b by the pressure changing unit is The pressure at the time of fixing by the pressure changing means is set to be larger than the pressure (pressing force = pressing pressure) of the pressure roller 17b contacting the belt nip Na by the pressure changing means at the time of fixing the first surface (front surface). The pressing force (pressing pressure) of the pressure roller 17b against the fixing belt 27 is changed in a short time. Thereby, the pressing force applied to the belt nip Na during the fixing is changed in a short time, and the fixing load during the fixing (the pressing pressure (the pressing force) during the fixing) as described in FIG. Is larger, the glossiness of the toner image after fixing becomes higher. As described with reference to FIG. 22, the glossiness at the time of the first and second fixing of the first side of the toner image (toner image) on the surface is different. The added value becomes substantially equal to the glossiness when the toner image (toner image) on the back surface of the second surface subjected to the circulation reversal conveyance (reversal paper passing) is fixed at one time.
[0079]
As described above, the pressing force (fixing load) of the belt nip at the time of fixing can be changed in a short time, so that productivity does not decrease. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0080]
According to FIG. 10 or FIG. 11, as shown in FIG. 10, the fixing device 17 is provided with a tension auxiliary roller TRa facing the pressure roller 17b across the belt nip Na, inside the fixing belt 27. As shown in FIG. 11, a pressing spring SPa5 and a spring receiver SPA5 as a pressing spring fixing member are used as pressure changing means, and the pressing force (pressing force) of the tension assist roller TRa to the pressing roller 17b during fixing is used by the pressure changing means. Pressure).
[0081]
The change of the pressing force of the tension assist roller TRa at the time of fixing by the pressure changing means is performed by the rotation of the eccentric cam HC5 provided below the spring supports SPA5 at both ends. In response to the rotation of the eccentric cam drive motor Ma5, the eccentric shaft Ja5 provided on the eccentric cam HC5 is rotationally driven through the speed reduction mechanism GK5, and the eccentric cam HC5 at both ends is rotated. When the eccentric cams HC5 at both ends are rotated clockwise as indicated by the arrows in FIG. 11, the spring receivers SPA5 at both ends are pushed down to move the position, and the pressing springs SPA5 at both ends are assisted in tension. The rotation axis Jt4 at both ends of the roller TRa is pressed (pressed), and the tension assist roller TRa is pressed (pressed) to the pressure roller 17b via the fixing belt 27.
[0082]
The pressing force of the tension assisting roller TRa on the pressure roller 17b at the belt nip Na is changed by the pressure changing means, and the tension assisting roller TRa is pushed down obliquely downward as shown by a dashed line in FIG. Alternatively, the tension assist roller TRa may be pressed (pressed) against the pressure roller 17b via the fixing belt 27. At this time, at the time of fixing the second surface (back surface) that has been subjected to the circulating reversal conveyance (reversing paper passing), the pressure (pressing force = pressing pressure) that comes into contact with the belt nip Na of the tension assist roller TRa by the pressure changing unit is The tension at the time of fixing by the pressure changing unit is set so as to be larger than the pressure (pressing force = pressing pressure) of the tension assisting roller TRa contacting the belt nip Na by the pressure changing unit at the time of fixing the first surface (front surface). The pressing force (pressing pressure) of the auxiliary roller TRa on the fixing belt 27 is changed in a short time. Thereby, the pressing force applied to the belt nip Na during fixing is changed in a short time, and as described with reference to FIG. 20, the fixing load (fixing pressure (pressing force) during fixing) is fixed. ) Is larger, the glossiness of the toner image after fixing becomes higher, and as described with reference to FIG. 22, the glossiness at the time of the first and second fixings of the first side of the toner image (toner image) on the surface is different. Is substantially equal to the glossiness when the toner image (toner image) on the back surface of the second surface that has been subjected to the circulation reversal conveyance (reversal paper passing) is fixed at one time.
[0083]
In the above description, the pressing force (pressing pressure) at the time of fixing to the fixing belt 27 is changed by moving the heat generating roller 17a to the right position shown by the one-dot chain line in FIG. And the width of the belt nip portion Na can be increased. Alternatively, the tension roller 17c may be moved leftward to increase the width of the belt nip Na.
[0084]
As described above, the pressing force (fixing load) of the belt nip at the time of fixing can be changed in a short time, so that productivity does not decrease. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0085]
According to FIG. 12, a fixing device 17A according to a second example of the present invention uses a heating roller 17d as a first roller member, and uses a heating roller 17d as a second roller member in the fixing device 17 according to the first example of FIG. A pressure roller 17b used as a second roller member, for example, a halogen lamp HLa as a heating member is provided inside the heating roller 17d, and a fixing nip portion is provided between the heating roller 17d and the pressure roller 17b. By forming Nb and applying heat and pressure through the fixing nip portion Nb, the toner image (or color toner image) on the first surface (front surface) on the recording paper P described in FIG. (Reverse sheet passing) to fix the toner image (color toner image) on the second surface (back surface). At this time, a halogen lamp HLa as a heating member may be provided inside the pressure roller 17b.
[0086]
A heating roller 17d having a halogen lamp HLa provided therein is made of, for example, a metal pipe 171d as a cylindrical core having a wall thickness of about 2 to 5 mm using STKM (carbon steel pipe for machine structure), and a metal pipe 171d of the metal pipe 171d. An elastic layer 172d made of a silicon rubber member having a thickness (wall thickness) of 5 to 15 mm and a rubber hardness of about 25 to 30 Hs (JIS, A rubber hardness) using, for example, a silicon material on the outer peripheral surface; A release layer 173d using a PFA (perfluoroalkoxy) tube having a thickness of about 15 to 30 μm on the surface of 172d is formed as a softening soft roller having an outer diameter of about 40 to 60 mm.
[0087]
As described with reference to FIG. 2, as the pressure roller 17 b, for example, a metal pipe 171 b as a cylindrical metal core having a thickness of about 2 to 5 mm using STKM (carbon steel pipe for machine structure), For example, a silicon material is used on the outer peripheral surface of the pipe 171b, and a thin (thickness) 1 to 5 mm thick rubber layer having a rubber hardness of 40 Hs to 70 Hs (JIS, A rubber hardness) is used as an elastic layer made of a somewhat hard rubber member. Rubber roller layer 172b, and a release layer 173b formed by coating a surface of the rubber roller layer 172b with a PFA (perfluoroalkoxy) tube having a thickness of about 15 to 50 μm. It is configured as a roller.
[0088]
The toner image (or color toner image) on the first surface (front surface) on the recording paper P or the circulation reversal is formed by the fixing nip portion Nb formed between the heating roller 17d as a soft roller and the pressing roller 17b as a soft roller. The toner image (color toner image) on the second surface (back surface) is conveyed (reversed paper passing), and the toner image (or color toner image) is fixed.
[0089]
Further, a contact or non-contact temperature sensor TS1 is provided on the heating roller 17d to control the temperature of the heating roller 17d and the fixing belt 27.
[0090]
Also in the fixing device 17A, as described at the beginning, at the time of double-sided copying in the image forming apparatus described with reference to FIG. The glossiness is higher than the back surface (second surface) that does not pass through the fixing device, and the front surface (the surface that passes through the fixing device twice, the first surface) and the back surface (the surface that passes the fixing device only once, the second surface) Surface) differs in glossiness. In particular, when the sheets are stapled or the like, the glossiness differs between the left and right sides of the page, which is not preferable. As described above, the gloss difference between the front and back surfaces is generally in the range of 10 to 25 °.
[0091]
The premise that the difference in gloss between the front and back surfaces is eliminated by the present invention in the fixing device 17A of the second example is the same as described above with reference to FIGS. A fixing method of the present invention for eliminating the difference in glossiness between the front and back sides in the fixing device 17A of the second example will be described below with reference to FIG. 12, and FIGS. 3 and 20 to 22 described above.
[0092]
According to FIG. 12 or FIG. 3 described above, the fixing device 17A of the present invention has the configuration described in FIG. 12, and is different from FIG. 3 when fixing the first surface and fixing the second surface. As described above, the pressing means changes the pressing force (pressing pressure) of the pressing roller 17b to the heating roller 17d during fixing.
[0093]
The change of the pressing force of the pressing roller 17b at the time of fixing by the pressing means is the same as that described with reference to FIG. At the time of fixing the second surface (back surface) that has been subjected to the circulating reversal conveyance (reverse paper passing), the pressing force applied to the pressure roller 17b at the time of fixing by the pressing device is applied by the pressing device at the time of fixing the first surface (front surface). The change is made in a short time so as to be larger than the pressing force applied to the pressure roller 17b. Accordingly, as described with reference to FIG. 20, the greater the fixing load (fixing pressure (pressing force) during fixing) at the time of fixing, the higher the glossiness of the toner image after fixing becomes. As described above, the toner image on the front surface (toner image) obtained by adding the glossiness at the time of the first and second fixings on the first surface is the toner image on the back surface of the second surface subjected to the reversal transport (reverse paper passing). (Toner image) is substantially equal to the glossiness when fixing is performed once.
[0094]
As described above, since the fixing pressure (fixing load) at the time of fixing can be changed in a short time, the productivity does not decrease. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0095]
Next, the first surface of the fixing device 17 of the first example according to the present invention described with reference to FIGS. 2 to 11 or the fixing device 17A of the second example according to the present invention described with reference to FIG. In addition to the fixing method for suppressing the gloss difference between the (front surface) and the second surface (back surface), the timing of changing the fixing load at the belt nip portion during fixing by the above-described pressing unit, pressure changing unit, and the like, The timing of changing the width of the belt nip portion by the belt nip width changing means, moving means, and the like will be described below with reference to FIGS. 13 to 19 and FIGS. 3, 5, 7, 11, 11, and 20 to 22 described above. explain. The change timing is a transfer material transport interval changing unit (timing roller 23 described with reference to FIG. 1) that changes the transfer material transport interval when transitioning from image formation on the first surface to image formation on the second surface. It is performed in.
[0096]
The fixing device of the present invention shown in FIG. 13 has the same configuration as the fixing device 17 of the first example described with reference to FIG. 2, and each member has the same structure and function as those described with reference to FIG. Is used.
[0097]
In the fixing device 17, as described at the beginning, the surface (first surface) that passes through the fixing device twice during the double-sided copying in the image forming apparatus described with reference to FIG. 1 is fixed only once. The glossiness is higher than the back surface (second surface) that does not pass through the fixing device, and the front surface (the surface that passes through the fixing device twice, the first surface) and the back surface (the surface that passes the fixing device only once, the second surface) Surface) differs in glossiness. In particular, when the sheets are stapled or the like, the glossiness differs between the left and right sides of the page, which is not preferable. As described above, the gloss difference between the front and back surfaces is generally in the range of 10 to 25 °.
[0098]
In the fixing device 17 of the first example, the premise that the gloss difference between the front and back sides according to the present invention is eliminated is the same as that described above with reference to FIGS. In the fixing device 17 of the first example, the transfer material transfer interval changing means for changing the transfer material transfer interval when shifting from the image formation on the first surface to the image formation on the second surface is shown in FIG. This is performed by using the timing roller 23 for feeding the recording paper P as the transfer material to the transfer area of the first transfer means as the transfer material conveyance interval changing means.
[0099]
According to FIG. 13 or FIG. 3, the fixing device 17 of the present invention has the configuration described with reference to FIG. 13, and from the image formation on the first surface (front surface) indicated by a dashed line in FIG. Of the recording sheet P as a transfer material on the first surface (front surface) and the second surface (rear surface) of the recording paper P that has been reversed and passed (circularly inverted and conveyed) at the time of transition to the image formation of The transfer material conveyance interval from the front end portion Pa is, for example, 15 ms, and only the first surface (front surface) (or only the second surface (back surface) (not shown)) indicated by a solid line in FIG. The timing roller 23 is controlled so as to be longer than the transfer material conveyance interval, for example, 10 ms, between the rear end Pb of the previous recording paper P and the front end Pa of the subsequent recording paper P, In the meantime, the spring receiver SPA1 as a pressing spring fixing member of the pressing means as shown in FIG. The roller 17b is pressed, by increasing the fixing nip Nb pressing force is intended to increase the back surface gloss.
[0100]
The movement of the spring receiver SPA1 as the pressing spring fixing member is performed by rotation of the eccentric cam HC1 provided below the spring receiver SPA1 at both ends. In response to the rotation of the eccentric cam drive motor Ma, the eccentric shaft Ja1 provided on the eccentric cam HC1 is rotationally driven through the speed reduction mechanism GK1, and the eccentric cam HC1 at both ends is rotated. When the eccentric cams HC1 at both ends are rotated clockwise as indicated by the arrows in FIG. 3, the spring receivers SPA1 at both ends are lifted upward and moved to positions. Accordingly, the pressing springs SPa1 at both ends press (press) the rotating shafts Jt at both ends of the pressing roller 17b, and press (press) the pressing roller 17b against the tension roller 17c via the fixing belt 27. Then, the pressing force of the fixing nip portion Nb increases. When shifting from the image formation on the first surface (front surface) to the image formation on the second surface (rear surface), the direction in which the pressing force of the pressing roller 17b against the tension roller 17c increases is set as the moving direction, and the spring receiver SPA1 is moved upward. Move to As a result, the fixing pressure (fixing load) at the time of fixing when changing from the image formation on the first surface (front surface) to the image formation on the second surface (back surface) is changed in a short time, and FIG. As described above, the larger the fixing load (fixing pressure (pressing force) during fixing) at the time of fixing is, the higher the glossiness of the toner image after fixing becomes, and as described in FIG. The toner image (toner image) obtained by adding the glossiness at the first time and the second fixing time of the first surface of the toner image (toner image) corresponds to the toner image (toner image) on the back surface of the second surface that has been subjected to the reversal conveyance (reverse paper feeding). It becomes almost equal to the glossiness at the time of fixing.
[0101]
As described above, since the fixing pressure (fixing load) at the time of fixing at the time of shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface) can be changed in a short time, the productivity is reduced. Does not occur. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0102]
According to FIGS. 13 and 14 or FIG. 5 described above, the fixing device 17 of the present invention has the configuration described in FIGS. A rear end portion of the recording sheet P as a transfer material on the first surface (front surface) at the time of transition from image formation on the first surface (front surface) to image formation on the second surface (back surface) indicated by a chain line in FIG. The transfer material conveyance interval between Pb and the leading end portion Pa of the second surface (back surface) of the recording paper P that has been reversely passed (circularly inverted and conveyed) is, for example, 15 ms, and the first surface (solid line in FIG. 14) is indicated by a solid line. When an image is continuously formed on only the front surface (or only the second surface (rear surface) (not shown)), the rear end Pb of the previous recording paper P and the front end Pa of the subsequent recording paper P The timing roller 23 is controlled so as to be longer than the transfer material conveyance interval between the transfer rollers, for example, 10 ms. During this time, the position of the pressure roller 17b is moved by a moving unit as shown in FIG. The width is increased, the paper passing time is lengthened, and the glossiness of the back surface is increased.
[0103]
The change in the movement of the position of the pressure roller 17b is performed by the rotation of the eccentric cam HC2 provided below the spring receiver SPA2 at both ends shown in FIG. In response to the rotation of the eccentric cam drive motor Ma2, the eccentric shaft Ja2 provided on the eccentric cam HC2 is rotationally driven through the speed reduction mechanism GK2, and the eccentric cam HC2 at both ends is rotated. When the eccentric cams HC2 at both ends are rotated clockwise as indicated by arrows in FIG. 5, the spring receivers SPA2 at both ends are lifted upward and moved to positions, and the pressing springs SPA2 at both ends are pressed by the pressing roller. The rotation shafts Jt1 at both ends of the roller 17b are pressed (pressed), and the pressure roller 17b is pressed (pressed) and moved to the stretching roller 17c via the fixing belt 27. At this time, when shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface), the width of the fixing belt 27 in the movement direction of the fixing belt 27 at the belt nip portion Na (the belt nip portion of the recording paper). The pressure roller 17b is moved upward with the direction in which the time increases. Thus, the width in the moving direction of the fixing belt in the belt nip portion at the time of fixing at the time of transition from image formation on the first surface (front surface) to image formation on the second surface (back surface) is changed in a short time. As described with reference to FIG. 21, the greater the width of the belt nip portion during fixing (the time required for passing the recording paper through the belt nip portion), the higher the glossiness of the toner image after fixing becomes. As described above, the sum of the glossiness at the time of the first fixing of the first side of the toner image (toner image) on the front surface and the second fixing by the circulation reversal conveyance (reversal paper passing) is obtained by the reversal conveyance (reversal conveyance). The glossiness when the toner image (toner image) on the back surface of the second surface (paper) is fixed at one time is substantially equal to the glossiness.
[0104]
As described above, the width of the belt nip portion can be changed in a short time at the time of fixing when the image formation on the first surface (front surface) is changed to the image formation on the second surface (back surface), so that the productivity is reduced. do not do. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0105]
According to FIG. 15 or FIG. 7 described above, the fixing device 17 of the present invention has the configuration described in FIG. 13 and FIG. A rear end portion of the recording sheet P as a transfer material on the first surface (front surface) when shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface) indicated by a chain line in FIG. The transfer material conveyance interval between Pb and the leading end portion Pa of the second surface (back surface) of the recording paper P that has been reversed and passed (circularly reversed and conveyed) is, for example, 15 ms, and the first surface (solid line in FIG. When an image is continuously formed on only the front surface (or only the second surface (rear surface) (not shown)), the rear end Pb of the previous recording paper P and the front end Pa of the subsequent recording paper P The timing roller 23 is controlled so as to be longer than the transfer material conveyance interval between the transfer rollers, for example, 10 ms, and the position of the auxiliary roller HRa is moved in the meantime to widen the width of the belt nip Na to reduce the paper passing time. It increases the glossiness of the back side.
[0106]
The change of the movement of the position of the auxiliary roller HRa is performed using, for example, the pressing spring SPa3 described with reference to FIG. 7 and the spring receiver SPA3 as a pressing spring fixing member, and the pressing spring SPa3 moves the both ends of the auxiliary roller HRa. The fixing roller 27 is pressed (pressed), and the auxiliary roller HRa presses (presses) and moves the fixing belt 27. At this time, when shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface), the width of the fixing belt 27 in the movement direction of the fixing belt 27 at the belt nip portion Na (the belt nip portion of the recording paper). The auxiliary roller HRa is moved to the lower left with the direction in which the time increases) as the movement direction. Thus, the width in the moving direction of the fixing belt in the belt nip portion at the time of fixing at the time of transition from image formation on the first surface (front surface) to image formation on the second surface (back surface) is changed in a short time. As described with reference to FIG. 21, the greater the width of the belt nip portion during fixing (the time required for passing the recording paper through the belt nip portion), the higher the glossiness of the toner image after fixing becomes. As described above, the sum of the glossiness at the time of the first fixing of the first side of the toner image (toner image) on the front surface and the second fixing by the circulation reversal conveyance (reversal paper passing) is obtained by the reversal conveyance (reversal conveyance). The glossiness when the toner image (toner image) on the back surface of the second surface (paper) is fixed at one time is substantially equal to the glossiness.
[0107]
As described above, the width of the belt nip portion can be changed in a short time at the time of fixing when the image formation on the first surface (front surface) is changed to the image formation on the second surface (back surface), so that the productivity is reduced. do not do. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0108]
According to FIG. 16 or FIG. 8 described above, the fixing device 17 of the present invention has the configuration described in FIG. 13 and FIG. A rear end portion of the recording sheet P as a transfer material on the first surface (front surface) when shifting from image formation on the first surface (front surface) to image formation on the second surface (back surface) indicated by a dashed line in FIG. The transfer material conveyance interval between Pb and the leading end portion Pa of the second surface (back surface) of the recording paper P that has been subjected to reverse passing (circulation reverse conveyance) is, for example, 15 ms, and the first surface (solid line in FIG. 16) When an image is continuously formed on only the front surface (or only the second surface (rear surface) (not shown)), the rear end Pb of the previous recording paper P and the front end Pa of the subsequent recording paper P The timing roller 23 is controlled so as to be longer than the transfer material conveyance interval between the transfer members, for example, 10 ms, and the position of the holding member HG is moved to press the fixing belt 27 in the meantime, thereby pressing the belt nip Na. To increase the glossiness of the back surface.
[0109]
The change in the movement of the position of the holding member HG is performed by the rotation of the pressing spring SPa4 provided between the holding member HG and the spring receiver SPA4 and the rotation of the eccentric cam HC4 provided above the holding member HG. In response to the rotation of the eccentric cam drive motor Ma, the eccentric shaft Ja4 provided on the eccentric cam HC4 is rotationally driven through the speed reduction mechanism GK, and the eccentric cam HC4 is rotated. When the eccentric cam HC4 is rotated clockwise as indicated by the arrow in FIG. 16, the spring receiver SPA4 is pushed down and moved to a position, and the pressing spring SPA4 presses (presses) the spring receiver SPA4, The auxiliary pressure pad HP is pressed (pressed) to the pressure roller 17 b via the fixing belt 27. At this time, when moving from the image formation on the first surface (front surface) to the image formation on the second surface (back surface), the direction in which the pressing force (pressing pressure) on the belt nip portion Na increases becomes the moving direction. The holding member HG is moved downward by rotating the lead cam HC4. Thereby, the fixing pressure (fixing load) of the belt nip portion at the time of fixing when shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface) is changed in a short time, and Also, as described in FIG. 20, the larger the fixing load (fixing pressure (pressing force) during fixing) at the time of fixing, the higher the glossiness of the toner image after fixing, and as shown in FIG. To the toner image (toner image) on the front side and the glossiness at the time of the first and second fixings on the first side are the same as the toner image (toner Image) is substantially equal to the glossiness when the image is fixed once.
[0110]
As described above, since the fixing pressure (fixing load) of the belt nip portion at the time of fixing when shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface) can be changed in a short time, production There is no drop in sex. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0111]
Further, according to FIG. 17 or FIG. 5 described above, the fixing device 17 of the present invention has the configuration described in FIG. 13 and FIG. A rear end portion of the recording paper P as a transfer material on the first surface (front surface) when shifting from image formation on the first surface (front surface) to image formation on the second surface (back surface) indicated by a chain line in FIG. The transfer material conveyance interval between Pb and the leading end portion Pa of the second surface (back surface) of the recording paper P that has been reversed and passed (circulated and reversed) is, for example, 15 ms, and the first surface (solid line in FIG. 17) When an image is continuously formed on only the front surface (or only the second surface (rear surface) (not shown)), the rear end Pb of the previous recording paper P and the front end Pa of the subsequent recording paper P The timing roller 23 is controlled so as to be longer than the transfer material conveyance interval, for example, 10 ms, and the position of the pressure roller 17b is moved during this time to press the fixing belt 27 against the fixing plate KPa, and the belt nip portion The pressing force of Na is increased to increase the glossiness of the back surface.
[0112]
The change in the movement of the position of the pressure roller 17b is performed using, for example, the pressing spring SPa2 described with reference to FIG. 5 and the spring receiver SPA2 as a pressing spring fixing member, and the pressing spring SPa2 is connected to both ends of the pressing roller 17b. The pressure roller 17b presses (presses) and moves the fixing belt 27 to the fixing plate KPa. At this time, when shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface), the width of the fixing belt 27 in the movement direction of the fixing belt 27 at the belt nip portion Na (the belt nip portion of the recording paper). The pressure roller 17b is moved upward with the direction in which the time (time) increases as the movement direction. As a result, the pressing force at the belt nip at the time of fixing when shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface) is changed in a short time, and FIG. 22, the larger the fixing load (fixing pressure (pressing pressure) during fixing) at the time of fixing, the higher the glossiness of the toner image after fixing, and as described in FIG. The toner image (toner image) obtained by adding the glossiness at the time of the first fixing of the first surface of the first side of the toner image and the second fixing by the circulation reversal conveyance (reversal paper passing) is added to the second surface of the toner reversal conveyance (reversal paper passing). The glossiness is substantially equal to the glossiness when the toner image (toner image) on the back surface is fixed once.
[0113]
As described above, the width of the belt nip portion can be changed in a short time at the time of fixing when the image formation on the first surface (front surface) is changed to the image formation on the second surface (back surface), so that the productivity is reduced. do not do. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0114]
Further, according to FIG. 18 or FIG. 11 described above, the fixing device 17 of the present invention has the configuration described in FIG. 13 and FIG. A rear end portion of the recording paper P as a transfer material on the first surface (front surface) when shifting from image formation on the first surface (front surface) to image formation on the second surface (back surface) indicated by a chain line in FIG. The transfer material conveyance interval between Pb and the leading end portion Pa of the second surface (back surface) of the recording paper P that has been reversed and passed (circularly reversed and conveyed) is, for example, 15 ms, and the first surface (solid line in FIG. 18) is indicated by a solid line. When an image is continuously formed on only the front surface (or only the second surface (rear surface) (not shown)), the rear end Pb of the previous recording paper P and the front end Pa of the subsequent recording paper P The timing roller 23 is controlled so as to be longer than the transfer material conveyance interval between the transfer rollers, for example, 10 ms, and during this time, the position of the tension assisting roller TRa is moved to increase the pressing force of the belt nip portion Na to increase the gloss of the back surface. It is to raise the degree.
[0115]
The change in the movement of the position of the tension assisting roller TRa is performed using, for example, the pressing spring SPa5 described with reference to FIG. 11 and the spring receiver SPA5 as a pressing spring fixing member, and the pressing spring SPa5 is connected to both ends of the tension assisting roller TRa. The portion is pressed (pressed), and the tension assist roller TRa presses (presses) and moves the fixing belt 27. At this time, when shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface), the width of the fixing belt 27 in the movement direction of the fixing belt 27 at the belt nip portion Na (the belt nip portion of the recording paper). The tension assisting roller TRa is moved to the lower right with the direction in which the time (time) increases becomes the moving direction. Thereby, the fixing pressure (fixing load) of the belt nip portion at the time of fixing when shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface) is changed in a short time, and Also, as described in FIG. 20, the larger the fixing load (fixing pressure (pressing force) during fixing) at the time of fixing, the higher the glossiness of the toner image after fixing, and as shown in FIG. To which the glossiness at the time of the first fixing of the first side of the toner image (toner image) on the front surface and the second fixing performed by the circulation reversal conveyance (reversal paper passing) is added to the circulation reversal conveyance (reversal paper passing). The glossiness when the toner image (toner image) on the back surface of the second surface is fixed at one time is substantially equal.
[0116]
In the above description, the change of the pressing force (pressing pressure) at the time of fixing the fixing belt 27 at the time of shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface) is described as the heating roller 17a. 18 can be moved to the rightward position shown by the one-dot chain line in FIG. 18 to widen the space between the stretching roller 17c and the heat generating roller 17a to increase the width of the belt nip Na. Alternatively, the tension roller 17c may be moved leftward to increase the width of the belt nip Na.
[0117]
As described above, the width of the belt nip portion can be changed in a short time at the time of fixing when the image formation on the first surface (front surface) is changed to the image formation on the second surface (back surface), so that the productivity is reduced. do not do. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0118]
According to FIG. 19, the fixing device 17A of the second example of the present invention has the same configuration as that described with reference to FIG.
[0119]
Also in the fixing device 17A, as described at the beginning, at the time of double-sided copying in the image forming apparatus described with reference to FIG. The glossiness is higher than the back surface (second surface) that does not pass through the fixing device, and the front surface (the surface that passes through the fixing device twice, the first surface) and the back surface (the surface that passes the fixing device only once, the second surface) Surface) differs in glossiness. In particular, when the sheets are stapled or the like, the glossiness differs between the left and right sides of the page, which is not preferable. As described above, the gloss difference between the front and back surfaces is generally in the range of 10 to 25 °.
[0120]
The premise that the difference in gloss between the front and back surfaces is eliminated by the present invention in the fixing device 17A of the second example is the same as described above with reference to FIGS. A fixing method of the present invention for eliminating the difference in glossiness between the front and back sides in the fixing device 17A of the second example will be described below with reference to FIG. 19 and FIGS. 3, 21 and 22 described above.
[0121]
According to FIG. 19 or FIGS. 3 and 12 described above, the fixing device 17A of the present invention has the configuration described with reference to FIG. 12, and from the image formation on the first surface (front surface) indicated by the one-dot chain line in FIG. At the time of transition to image formation on the front surface (back surface), the rear end portion Pb of the recording paper P as a transfer material on the first surface (front surface) and the second surface of the recording paper P that has been reversely passed (circularly inverted and conveyed) The transfer material transport interval between the front end portion Pa of the (back surface) and the front surface Pa is, for example, 15 ms, and only the first surface (front surface) (or only the second surface (back surface) (not shown)) indicated by a solid line in FIG. 19 is continuous. The timing roller 23 is set so that the transfer material transport interval between the rear end portion Pb of the previous recording sheet P and the front end portion Pa of the subsequent recording sheet P, for example, 10 ms, is longer than that when the image is formed. During this time, the position of the spring receiver SPA1 of the pressing means is moved, and the pressing roller 17b is pressed. And it is intended to increase the back surface gloss by increasing the pressing force of the fixing nip Nb.
[0122]
The change of the movement of the position by the pressing means is performed by using the pressing spring SPA1 shown in FIG. 3 and the spring receiver SPA1 as a pressing spring fixing member, and the pressing spring SPa1 presses both ends of the pressing roller 17b. Pressure) and presses (presses) the pressure roller 17b against the heating roller 17d. At this time, when moving from the image formation on the first surface (front surface) to the image formation on the second surface (back surface), the pressing roller 17b is moved upward with the direction in which the pressing force at the fixing nip Nb is increased as the moving direction. Move to As a result, the pressing force at the fixing nip at the time of shifting from the image formation on the first surface (front surface) to the image formation on the second surface (back surface) is changed in a short time, and also described in FIG. As described above, the larger the fixing load (fixing pressure (pressing force) during fixing) at the time of fixing, the higher the glossiness of the toner image after fixing, and as described in FIG. The sum of the glossiness at the time of the first fixing of the first surface of the (toner image) and the second fixing performed by the circulation reversal conveyance (reversal paper passing) is the toner on the back surface of the second surface subjected to the circulation reversal conveyance (reversal paper passing). The gloss is substantially equal to the gloss when the image (toner image) is fixed at one time.
[0123]
As described above, the width of the belt nip portion can be changed in a short time at the time of fixing when the image formation on the first surface (front surface) is changed to the image formation on the second surface (back surface), so that the productivity is reduced. do not do. Further, since the temperature can be set so as to obtain a sufficient fixing property, the fixing property does not decrease.
[0124]
【The invention's effect】
According to the present invention, the productivity is not reduced and the fixing property is prevented from being deteriorated. Thus, it is possible to provide an image forming apparatus having a fixing device in which the difference is suppressed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus using a fixing device according to the present invention.
FIG. 2 is a schematic sectional configuration diagram showing a first example of a fixing device according to the present invention.
FIG. 3 is a diagram illustrating a pressing unit used at the time of fixing the first surface and at the time of fixing the second surface.
FIG. 4 is a diagram illustrating a first example of changing a belt nip width used at the time of fixing the first surface and at the time of fixing the second surface in the fixing device of FIG. 2;
FIG. 5 is a diagram showing a belt nip width changing means used at the time of fixing the first surface (front surface) and the time of fixing the second surface (back surface).
FIG. 6 is a diagram illustrating a second example of changing the belt nip width used in fixing the first surface and fixing the second surface in the fixing device of FIG. 2;
FIG. 7 is a diagram illustrating a belt nip width changing unit used at the time of fixing the first surface (front surface) and the time of fixing the second surface (back surface).
FIG. 8 is a diagram showing a first example of a pressure changing unit used at the time of fixing the first surface and the time of fixing the second surface in the fixing device of FIG. 2;
FIG. 9 is a diagram illustrating a second example of a pressure changing unit used at the time of fixing the first surface and the time of fixing the second surface in the fixing device of FIG. 2;
FIG. 10 is a diagram illustrating a third example of a pressure changing unit used at the time of fixing the first surface and the time of fixing the second surface in the fixing device of FIG. 2;
FIG. 11 is a diagram showing pressure changing means used at the time of fixing the first surface (front surface) and at the time of fixing the second surface (back surface).
FIG. 12 is a schematic sectional configuration diagram showing a fixing device of a second example according to the invention.
FIG. 13 is a diagram illustrating a transfer material conveyance interval when the first example of the fixing device according to the present invention shifts from image formation on the first surface to image formation on the second surface.
14 is a diagram illustrating a first example of a belt nip width change used when the fixing device in FIG. 13 shifts from image formation on the first surface to image formation on the second surface.
FIG. 15 is a diagram illustrating a second example of changing the belt nip width used when shifting from image formation on the first surface to image formation on the second surface in the fixing device in FIG. 13;
16 is a diagram illustrating a first example of a pressure changing unit used when the fixing device in FIG. 13 shifts from image formation on the first surface to image formation on the second surface.
17 is a diagram illustrating a second example of a pressure changing unit used when the fixing device in FIG. 13 shifts from image formation on the first surface to image formation on the second surface.
FIG. 18 is a diagram illustrating a third example of a pressure changing unit used when the fixing device in FIG. 13 shifts from image formation on the first surface to image formation on the second surface.
FIG. 19 is a diagram illustrating a transfer material transport interval when a transition from image formation on the first surface to image formation on the second surface is performed in the fixing device of the second example according to the invention.
FIG. 20 is a diagram illustrating a relationship between a fixing load and glossiness.
FIG. 21 is a diagram illustrating a relationship between a paper passing time of a belt nip portion of recording paper and a glossiness.
FIG. 22 is a diagram showing a result of suppressing a gloss difference between front and back according to the present invention.
FIG. 23 is a diagram illustrating a change width of glossiness in fixing twice.
FIG. 24 is a diagram illustrating a gloss difference between front and back sides during duplex copying.
[Explanation of symbols]
1 Photoconductor drum
2 Charger
3 Exposure optical system
4 Developing device
6 Intermediate transfer belt
7 Primary transfer roller
7A secondary transfer roller
17 Fixing device
17a Heat roller
17b Pressure roller
17c tension roller
17d heating roller
27 Fixing belt
100 process units
HC1, HC2, HC3, HC4, HC5 Eccentric cam
HG holding member
HP auxiliary pressure pad
HLa halogen lamp
HRa auxiliary roller
KPa fixing plate
Na belt nip
Nb fixing nip
SPa1, SPa2, SPa3, SPa4, SPa5 Press spring
SPA1, SPA2, SPA3, SPA4, SPA5 Spring support
TRa tension assist roller
P Recording paper

Claims

An endless belt member,
A first roller member that stretches one of the inner peripheral surfaces of the belt member,
A second roller member abutting on the first roller member with the belt member interposed therebetween;
A third roller member provided in parallel with and separated from the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member of the belt member;
In an image forming apparatus having a fixing device for fixing a toner image on a transfer material,
The fixing device includes a pressing unit that presses the second roller member against the first roller member via the belt member,
After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. And fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material.
An image forming apparatus having a fixing device, wherein a pressing force applied to the second roller member by the pressing unit is changed between when the first surface is fixed and when the second surface is fixed.

The pressing force on the second roller member by the pressing means when fixing the second surface is greater than the pressing force on the second roller member by the pressing means when fixing the first surface. An image forming apparatus comprising the fixing device according to claim 1.

3. The fixing device according to claim 1, wherein the pressing unit includes a pressing spring and a pressing spring fixing member, and the pressing force is changed by moving a position of the pressing spring fixing member. Image forming device.

An endless belt member,
A first roller member that stretches one of the inner peripheral surfaces of the belt member,
A second roller member abutting on the first roller member with the belt member interposed therebetween;
A third roller member provided in parallel with and separated from the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member;
A fixing nip portion is formed between the first roller member and the second roller member with the belt member interposed therebetween, and a belt nip portion is formed between the belt member and the second roller member. Forming
An image forming apparatus having a fixing device for fixing a toner image on a transfer material by the fixing nip portion and the belt nip portion,
The fixing device includes a belt nip width changing unit that changes a width of the belt nip portion in a moving direction of the belt member,
After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. And fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material.
An image forming apparatus having a fixing device, wherein the width of the belt member in the moving direction by the belt nip width changing means is changed between when the first surface is fixed and when the second surface is fixed.

The width of the belt member in the movement direction of the belt nip portion by the belt nip width changing means at the time of fixing the second surface is equal to the width of the belt member of the belt nip portion by the belt nip width changing means at the time of fixing the first surface. The image forming apparatus having the fixing device according to claim 4, wherein the width of the fixing device is larger than the width in the moving direction.

6. The image forming apparatus according to claim 4, wherein the change of the width of the belt nip portion in the moving direction of the belt member is performed by moving the second roller member. 7.

The fixing device is provided with an auxiliary roller member around which the belt member for forming the belt nip portion is stretched, and the width of the belt nip portion in the moving direction of the belt member is changed by moving the position of the auxiliary roller member. An image forming apparatus having the fixing device according to claim 4.

An endless belt member,
A first roller member that stretches one of the inner peripheral surfaces of the belt member,
A second roller member abutting on the first roller member with the belt member interposed therebetween;
A third roller member provided in parallel with and separated from the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member;
A fixing nip portion is formed between the first roller member and the second roller member with the belt member interposed therebetween, and a belt nip portion is formed between the belt member and the second roller member. Forming
An image forming apparatus having a fixing device for fixing a toner image on a transfer material by the fixing nip portion and the belt nip portion,
The fixing device further includes a pressure changing unit that changes a pressure of the belt nip portion that contacts the second roller member;
After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. And fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material.
An image forming apparatus having a fixing device, wherein the pressure changing means changes the pressure of the belt nip portion in contact with the second roller member between the time of fixing the first surface and the time of fixing the second surface. .

The pressure at which the pressure changing means contacts the second roller member at the time of fixing the second surface is the second pressure of the belt nip at which the pressure changing means is fixed at the time of fixing the first surface. 9. An image forming apparatus having a fixing device according to claim 8, wherein the pressure is higher than a pressure at which the roller contacts the roller member.

The pressure changing unit includes a sliding member that slides on the inner surface of the belt member, and a sliding auxiliary member that presses the sliding member against the second roller member via the belt member. The image forming apparatus according to claim 8, wherein the change of the pressure by the change unit is performed by moving a position of the slide assist member.

Providing a fixing member facing the second roller member with the belt nip portion interposed therebetween, and changing the pressing force at the belt nip portion by changing the pressure on the fixing member of the second roller member. An image forming apparatus comprising the fixing device according to claim 8.

A pressure changing means for the second roller member comprising a pressing spring and a pressing spring fixing member is provided, and the change of the pressing force on the fixing member is changed by the second roller member by the pressure changing means of the second roller member. An image forming apparatus having a fixing device according to claim 11, wherein the fixing is performed by changing a pressure on a member.

The fixing device includes a tension auxiliary roller that applies tension to the belt member, and changes a pressure of the belt nip portion that contacts the second roller member by changing a tension of the belt member by moving the tension auxiliary roller. An image forming apparatus having the fixing device according to claim 8, wherein the fixing is performed by changing the image forming apparatus.

14. The image forming apparatus according to claim 13, wherein the first roller member or the third roller member also functions as the tension auxiliary roller.

A first roller member having a heating means and made of a metal core and an elastic layer, and a second roller member made of a metal core and an elastic layer provided opposite to the first roller member With
In an image forming apparatus having a fixing device for fixing a toner image on a transfer material,
The fixing device includes a pressing unit that presses the second roller member against the first roller member,
After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. And fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material.
An image forming apparatus having a fixing device, wherein a pressing force applied to the second roller member by the pressing unit is changed between when the first surface is fixed and when the second surface is fixed.

The pressing force on the second roller member by the pressing means when fixing the second surface is greater than the pressing force on the second roller member by the pressing means when fixing the first surface. An image forming apparatus comprising the fixing device according to claim 15.

17. The fixing device according to claim 15, wherein the pressing unit includes a pressing spring and a pressing spring fixing member, and the pressing force is changed by moving a position of the pressing spring fixing member. Image forming device.

An endless belt member,
A first roller member that stretches one of the inner peripheral surfaces of the belt member,
A second roller member abutting on the first roller member with the belt member interposed therebetween;
A third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member;
In an image forming apparatus having a fixing device for fixing a toner image on a transfer material,
The fixing device includes a pressing unit including a pressing spring that presses the second roller member against the first roller member and a pressing spring fixing member.
A transfer material transport interval changing means for changing the transfer material transport interval is provided,
After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. And fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material.
The transfer material transport interval when transitioning from the first surface image formation to the second surface image formation is longer than the transfer material transport interval when the first surface or the second surface is continuously image-formed. An image forming apparatus having a fixing device, wherein a pressing spring fixing member of the pressing means is moved during the operation.

19. The image forming apparatus according to claim 18, wherein the moving direction of the pressing spring fixing member is a direction in which the pressing force of the second roller member against the first roller member increases. .

An endless belt member,
A first roller member that stretches one of the inner peripheral surfaces of the belt member,
A second roller member abutting on the first roller member with the belt member interposed therebetween;
A third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member;
A fixing nip portion is formed between the first roller member and the second roller member with the belt member interposed therebetween, and a belt nip portion is formed between the belt member and the second roller member. Forming
An image forming apparatus having a fixing device for fixing a toner image on a transfer material by the fixing nip portion and the belt nip portion,
The fixing device includes a moving unit that moves a position of the second roller member,
A transfer material transport interval changing means for changing the transfer material transport interval is provided,
After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. And fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material.
The transfer material transport interval when shifting from the first surface image formation to the second surface image formation is longer than the transfer material transport interval when the first surface or the second surface is continuously image-formed. An image forming apparatus having a fixing device, wherein the position of the second roller member is moved by moving means of the fixing device.

21. The image forming apparatus according to claim 20, wherein the moving direction of the second roller member is a direction in which a width of the belt nip portion in the moving direction of the belt member is increased.

An endless belt member,
A first roller member that stretches one of the inner peripheral surfaces of the belt member,
A second roller member abutting on the first roller member with the belt member interposed therebetween;
A third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member;
A fixing nip portion is formed between the first roller member and the second roller member with the belt member interposed therebetween, and a belt nip portion is formed between the belt member and the second roller member. Forming
An image forming apparatus having a fixing device for fixing a toner image on a transfer material by the fixing nip portion and the belt nip portion,
In the fixing device, an auxiliary roller member around which a belt member for forming the belt nip portion is provided,
A transfer material transport interval changing means for changing the transfer material transport interval is provided,
After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. And fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material.
The transfer material transport interval when transitioning from the first surface image formation to the second surface image formation is longer than the transfer material transport interval when the first surface or the second surface is continuously image-formed. An image forming apparatus having a fixing device, wherein the auxiliary roller member of the fixing device is moved during the operation.

23. The image forming apparatus according to claim 22, wherein the moving direction of the auxiliary roller member is a direction in which the width of the belt nip portion in the moving direction of the belt member is increased.

An endless belt member,
A first roller member that stretches one of the inner peripheral surfaces of the belt member,
A second roller member abutting on the first roller member with the belt member interposed therebetween;
A third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member;
A fixing nip portion is formed between the first roller member and the second roller member with the belt member interposed therebetween, and a belt nip portion is formed between the belt member and the second roller member. Forming
An image forming apparatus having a fixing device for fixing a toner image on a transfer material by the fixing nip portion and the belt nip portion,
In the fixing device, a sliding member that slides on an inner surface of the belt member for changing a pressure that contacts a second roller member of the belt nip portion, and the sliding member is connected to the belt member through the belt member. A pressure assisting means comprising: a sliding auxiliary member for pressing against the second roller member;
A transfer material transport interval changing means for changing the transfer material transport interval is provided,
After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. And fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material.
The transfer material conveyance interval when shifting from the first surface image formation to the second surface image formation is set to be smaller than the transfer material conveyance interval when the first surface or the second surface is continuously image-formed. An image forming apparatus having a fixing device, wherein the sliding assist member of the pressure changing unit is moved during the operation.

The moving direction of the sliding assist member of the pressure changing means is a direction in which a pressure of the belt nip portion pressing the second roller member of the belt member is increased. An image forming apparatus having a fixing device.

An endless belt member,
A first roller member that stretches one of the inner peripheral surfaces of the belt member,
A second roller member abutting on the first roller member with the belt member interposed therebetween;
A third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member;
A fixing nip portion is formed between the first roller member and the second roller member with the belt member interposed therebetween, and a belt nip portion is formed between the belt member and the second roller member. Forming
An image forming apparatus having a fixing device for fixing a toner image on a transfer material by the fixing nip portion and the belt nip portion,
A fixing member facing the second roller member with the belt nip portion interposed therebetween;
And a pressure changing means for the second roller member comprising a pressing spring and a pressing spring fixing member is provided,
A transfer material transport interval changing means for changing the transfer material transport interval is provided,
After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. And fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material.
The transfer material conveyance interval when shifting from the first surface image formation to the second surface image formation is set to be smaller than the transfer material conveyance interval when the first surface or the second surface is continuously image-formed. An image forming apparatus having a fixing device, wherein the pressing spring fixing member of the pressure changing unit of the second roller member is moved during the operation.

27. The fixing device according to claim 26, wherein a moving direction of the pressing spring fixing member is a direction in which a pressure of the belt member pressing the second roller member at the belt nip is increased. Image forming device.

An endless belt member,
A first roller member that stretches one of the inner peripheral surfaces of the belt member,
A second roller member abutting on the first roller member with the belt member interposed therebetween;
A third roller member provided in parallel with the first roller member and provided with heating means for stretching the other of the inner peripheral surfaces of the belt member;
A fixing nip portion is formed between the first roller member and the second roller member with the belt member interposed therebetween, and a belt nip portion is formed between the belt member and the second roller member. Forming
An image forming apparatus having a fixing device for fixing a toner image on a transfer material by the fixing nip portion and the belt nip portion,
In the fixing device, while providing a tension auxiliary roller for applying tension to the belt member,
A transfer material transport interval changing means for changing the transfer material transport interval is provided,
After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. And fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material.
The transfer material conveyance interval when shifting from the first surface image formation to the second surface image formation is set to be smaller than the transfer material conveyance interval when the first surface or the second surface is continuously image-formed. An image forming apparatus having a fixing device, wherein the tension auxiliary roller of the fixing device is moved during the fixing.

29. The image forming apparatus according to claim 28, wherein the moving direction of the tension assisting roller is a direction in which the width of the belt nip portion in the moving direction of the belt member is increased.

30. The image forming apparatus having a fixing device according to claim 28, wherein the first roller member or the third roller member also functions as the tension auxiliary roller.

A first roller member having a heating means and made of a metal core and an elastic layer, and a second roller member made of a metal core and an elastic layer provided opposite to the first roller member With
In an image forming apparatus having a fixing device for fixing a toner image on a transfer material,
The fixing device includes a pressing unit that includes a pressing spring and a pressing spring fixing member and presses the second roller member against the first roller member.
A transfer material transport interval changing means for changing the transfer material transport interval is provided,
After forming an image on the first surface of the transfer material and fixing the toner image on the first surface of the transfer material through the fixing device, the transfer material having passed through the fixing device is circulated and conveyed to the second surface of the transfer material. And fixing the toner image on the second surface of the transfer material through the fixing device, and fixing the toner images on both the first surface and the second surface of the transfer material.
The transfer material conveyance interval when shifting from the first surface image formation to the second surface image formation is set to be smaller than the transfer material conveyance interval when the first surface or the second surface is continuously image-formed. An image forming apparatus having a fixing device, wherein the pressing spring fixing member of the pressing unit is moved during the operation.

32. The image forming apparatus according to claim 31, wherein a moving direction of the pressing spring fixing member is a direction in which a width of the belt nip portion in a moving direction of the belt member is increased.