JP2004067336A - Sheet carrying device and image forming device equipped with this sheet carrying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet carrying device and an image forming device capable of preventing wrinkles on a sheet by preventing generation of flexure occurring during carrying the sheet. <P>SOLUTION: A paper feeding roller 12 gives a carrying force from one surface side of the sheet S, and paper feeding separation roller 13 supports the sheet S from another surface side, and gives a slidable resistance force in an opposite direction to the carrying force when a carrying resistance is large. The sheet S reaches a first carrying roller pair 15 and second carrying roller pair 16, 17, and loses the carrying force and gives the carrying resistance force to the sheet S in the opposite direction to the carrying force. The second carrying roller pair 16, 17 arranged in both sides of the first carrying roller pair 15 and the first carrying roller 15 arranged on the downstream side of the carrying direction of the paper feeding roller 12, give the carrying force to the sheet S, but the carrying force given to the sheet S of the first carrying roller pair 15 is larger than the carrying force given to the sheet S of the second carrying roller pair 16, 17. <P>COPYRIGHT: (C)2004,JPO

Description

【００６７】
この通紙性能の実験では、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外径Ｄ２を１５．９５ｍｍとし、第１搬送駆動ローラ１５ａのローラ本体２０ａの外径Ｄ１をＤ１＝Ｄ２＋ΔＤとした。また、この通紙性能の実験では、薄手のシート、普通のシートおよび厚手のシートを用いた。ここで、薄手のシートは坪量が５２ｇ／ｍ^２以上８０ｇ／ｍ^２以下の範囲のシートであり、普通のシートは坪量が８１ｇ／ｍ^２以上１０５ｇ／ｍ^２以下の範囲シートであり、厚手のシートは坪量が１０６ｇ／ｍ^２以上３００ｇ／ｍ^２以下の範囲のシートである。また本実験でのシートは、紙から成るシートを用い、紙の目の方向と搬送方向とを平行にして搬送される。
【００６８】
表１では、搬送中のシート状態を、シワ寄りの状態は×で表し、シワ寄りの原因になると思われる撓みの発生した状態は△で表し、第１搬送ローラ対１５のみで搬送される状態は□で表し、シワ寄りの原因になると思われる撓みの発生のない状態は○で表す。
【００６９】
前記外径Ｄ１，Ｄ２の差ΔＤ（＝Ｄ１−Ｄ２）を０ｍｍとし、薄手のシート、普通のシートおよび厚手のシートをそれぞれ搬送させた結果、普通のシートおよび厚手のシートは、撓みの発生のない状態で良好に搬送されたが、薄手のシートには、撓みが発生し、搬送に伴って異常音が発生して、シワ寄りの状態で搬送された。
【００７０】
前記外径Ｄ１，Ｄ２の差ΔＤ（＝Ｄ１−Ｄ２）を０．１５ｍｍとし、薄手のシート、普通のシートおよび厚手のシートをそれぞれ搬送させた結果、普通のシートおよび厚手のシートは撓みの発生のない状態で良好に搬送されたが、薄手のシートは、前記外径Ｄ１，Ｄ２の差ΔＤ（＝Ｄ１−Ｄ２）を０ｍｍとして搬送されたときと比べると、撓みは軽減したが、やはり撓みが発生した状態で搬送された。
【００７１】
前記外径Ｄ１，Ｄ２の差ΔＤ（＝Ｄ１−Ｄ２）を０．２５ｍｍ，０．３５ｍｍとし、薄手のシート、普通のシートおよび厚手のシートをそれぞれ搬送させた結果、薄手のシート、普通のシートおよび厚手のシートは、いずれもシワ寄りの原因になる撓みの発生のない状態で良好に搬送された。
【００７２】
前記外径Ｄ１，Ｄ２の差ΔＤ（＝Ｄ１−Ｄ２）を０．４５ｍｍとし、薄手のシート、普通のシートおよび厚手のシートをそれぞれ搬送させた結果、薄手のシート、普通のシートおよび厚手のシートは、いずれも第１搬送ローラ対１５のみで搬送される状態となり、搬送方向に対してまれに斜めに搬送された。
【００７３】
表１に示す実験結果から、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外径Ｄ２が１５．９３ｍｍであって、前記外径Ｄ１，Ｄ２の差ΔＤ（＝Ｄ１−Ｄ２）が、０．２５ｍｍ〜０．３５ｍｍであるとき、薄手のシート、普通のシートおよび厚手のシートのいずれであっても撓みの発生を防ぎ、シワ寄りのない状態でシートを良好に搬送できることがわかる。
【００７４】
前述の実験において、前記Ｄ１，Ｄ２の差ΔＤ（＝Ｄ１−Ｄ２）が０．２５ｍｍであるとき、第１搬送ローラ対１５の搬送力は１０００ｇｆ〜１１５０ｇｆであり、第２搬送ローラ対１６，１７の搬送力５５０ｇｆ〜６５０ｇｆであり、分離部１４によって生じる前記搬送力とは逆むきの搬送抵抗力は４５０ｇｆ〜５５０ｇｆである。
【００７５】
また、本実施の形態のシート搬送装置１１における通紙性能の他の実験結果によって、シート搬送装置１１は、前述の実験と同様に、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ．２２ａの外径Ｄ２を１５．９５ｍｍとし、前記Ｄ１，Ｄ２の差ΔＤ（＝Ｄ１−Ｄ２）が０．２５ｍｍ〜０．３５ｍｍであるとき、坪量が５２ｇ／ｍ^２以上３００ｇ／ｍ^２以下の範囲のシートをシワ寄りの原因となる撓みの発生のない状態で良好に搬送できることがわかった。
【００７６】
前述のような本実施の形態のシート搬送装置１１によれば、分離部１４に備えられた給紙ローラ１２のローラ本体１２ａは、給紙部３１から給紙されたシートＳの一表面側から搬送力を与え、同時に、分離部１４に備えられた給紙分離ローラ１３のローラ本体１３ａは、前記シートＳの他表面側から、従動回転することによって前記搬送力とは逆向きの回転抵抗力または回転を停止することによって前記搬送力とは逆向きの摺動抵抗力を与える。このようにして給紙ローラ１２および給紙分離ローラ１３を備えた分離部１４は、第１搬送ローラ対１５および第２搬送ローラ対１６，１７に前記シートＳを搬送する。また、前記給紙ローラ１２のローラ本体１２ａは、前記シートＳが第１搬送ローラ対１５および第２搬送ローラ対１６，１７に到達した後、シートＳに与える搬送力を失い、第１搬送ローラ対１５および第２搬送ローラ対１６，１７によって搬送されるシートＳによって従動回転する。すなわち、分離部１４の給紙ローラ１２および給紙分離ローラ１３とは、第１搬送ローラ対１５および第２搬送ローラ対１６，１７に到達されたシートＳに対して前記搬送力とは逆向きの搬送抵抗力を与える。
【００７７】
第１搬送駆動ローラ１５ａおよび第２搬送駆動ローラ１６ａ，１７ａは、それぞれローラ本体２０ａ，２１ａ，２２ａを有し、第１搬送駆動ローラ１５ａのローラ本体２０ａの外径Ｄ１が、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外径Ｄ２よりも大きく（Ｄ１＞Ｄ２）選ばれる。また、第１搬送駆動ローラ１５ａと第２搬送駆動ローラ１６ａ，１７ａとは、同一の回転軸である搬送ローラ軸２３ａを有する。
【００７８】
この搬送ローラ軸によって第１搬送駆動ローラ１５ａのローラ本体２０ａおよび第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａを同一の角速度で回転させる。これによって第１搬送駆動ローラ１５ａのローラ本体２０ａの外周面の周速が、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外周面の周速よりも大きくなる。
【００７９】
したがって、第１搬送駆動ローラ１５ａのローラ本体２０ａの外周面の周速が、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外周面の周速よりも大きくなるので、第１搬送駆動ローラ１５ａのローラ本体２０ａの搬送力を第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの搬送力よりも大きくなる。すなわち、分離部１４から搬送されたシートＳに対して、前記第１搬送ローラ対１５は、第２搬送ローラ対１６，１７よりも大きな搬送力をシートＳに与え、レジスト部３４に搬送する。
【００８０】
このような分離部１４、第１搬送ローラ対１５および第２搬送ローラ対１６，１７を備えたシート搬送装置１１において、分離部１４から搬送されたシートＳが第１搬送ローラ対１５および第２搬送ローラ対１６，１７に到達し、前記シートＳが分離部１４から離間するまでの間、前記シートＳは、第１搬送ローラ対１５、第２搬送ローラ対１６，１７および分離部１４と当接した状態となる。このとき、前記シートＳは、第１搬送ローラ対１５および第２搬送ローラ対１６，１７から搬送力を受け、同時に、分離部１４から前記搬送力とは逆向きの搬送抵抗力を受けるが、第１搬送ローラ対１５のシートＳに与える搬送力が、第２搬送ローラ対１６，１７のシートＳに与える搬送力よりも大きいので、前記搬送抵抗力によって、搬送経路に垂直な幅方向に関して、第１搬送ローラ対１５の位置するシートＳ部分が搬送経路に垂直な幅方向に関して、第２搬送ローラ対１６，１７の位置するシートＳ部分に比べ、遅れて搬送されるのを防ぐことができる。
【００８１】
したがって、シートＳに生じるシワ寄りの原因である撓みの発生を防ぎ、シートＳをシワ寄りのない状態で搬送することができる。
【００８２】
前述の実施の形態では、シート検出器４４として、接触式のアクチュエータ４４ａを備えたフォトセンサを用いたが、接触式のアクチュエータ４４ａを備えたリードセンサまたは非接触式のフォトセンサを用いてもよい。
【００８３】
また、シートＳは、紙から成る印刷用紙を用いたが、オーバーヘッドプロジェクタ（Ｏｖｅｒ　Ｈｅａｄ　Ｐｒｏｊｅｃｔｏｒ；略称ＯＨＰ）シートなどのプラスチックシートを用いてもよい。
【００８４】
さらに、分離部１４の有する支持体として給紙分離ローラ１３を用いたが、ローラタイプのものではなく、パッドタイプのものを用いてもよい。
【００８５】
本発明の実施の他の形態では、前述の図１〜図５の実施の形態において、第１搬送駆動ローラ１５ａのローラ本体２０ａの外径Ｄ１と第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外径Ｄ２とを等しく（Ｄ１＝Ｄ２）し、第１搬送駆動ローラ１５ａのローラ本体２０ａの外周面の摩擦係数を第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外周面の摩擦係数より大きくする。その他の構成は前述の実施の形態と同様である。
【００８６】
このような構成によれば、第１搬送駆動ローラ１５ａのローラ本体２０ａの外周面の摩擦係数が第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外周面の摩擦係数よりも大きいので、第１搬送駆動ローラ１５ａのローラ本体２０ａの外周面がシートに与える摩擦力が、第２搬送ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外周面がシートに与える摩擦力よりも大きくなる。したがって搬送するシートに対して第１搬送ローラ対１５の空回りが第２搬送ローラ対１６，１７の空回りよりも防止されるので、第１搬送ローラ対１５の搬送力を、第２搬送ローラ対１６，１７の搬送力よりも大きくすることができる。
【００８７】
本発明の実施のさらに他の形態では、前述の図１〜図５の実施の形態において、第１搬送駆動ローラ１５ａのローラ本体２０ａの外径Ｄ１と第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外径Ｄ２とを等しく（Ｄ１＝Ｄ２）し、第１搬送駆動ローラ１５ａのローラ本体２０ａの硬度を、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの硬度より低くする。その他の構成は前述の実施の各形態と同様である。
【００８８】
このような構成によれば、第１搬送駆動ローラ１５ａのローラ本体２０ａの硬度が第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの硬度よりも低いので、第１搬送駆動ローラ１５ａのローラ本体２０ａのシートへの接触面積が第２搬送駆動ローラ１６ａ，１７ａのシートへの接触面積よりも大きくなる。したがって搬送するシートに対して第１搬送ローラ対１５の空回りが第２搬送ローラ対１６，１７の空回りよりも防止されるので、第１搬送ローラ対１５の搬送力を、第２搬送ローラ対１６，１７の搬送力よりも大きくすることができる。
【００８９】
本発明の実施のさらに他の形態では、前述の図１〜図５の実施の形態において、第１搬送駆動ローラ１５ａのローラ本体２０ａの外径Ｄ１を第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外径Ｄ２より大きく（Ｄ１＞Ｄ２）するとともに、第１搬送駆動ローラ１５ａのローラ本体２０ａの外周面の摩擦係数を第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外周面の摩擦係数より大きくする。その他の構成は前述の実施の各形態と同様である。
【００９０】
このような構成によれば、第１搬送ローラ対１５の搬送力を、第２搬送ローラ対１６，１７の搬送力よりも、より確実に大きくすることができる。
【００９１】
本発明の実施のさらに他の形態では、前述の図１〜図５の実施の形態において、第１搬送駆動ローラ１５ａのローラ本体２０ａの外径Ｄ１を第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外径Ｄ２より大きく（Ｄ１＞Ｄ２）するとともに、第１搬送駆動ローラ１５ａのローラ本体２０ａの硬度を、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの硬度より低くする。その他の構成は前述の実施の各形態と同様である。
【００９２】
このような構成によれば、第１搬送ローラ対１５の搬送力を、第２搬送ローラ対１６，１７の搬送力よりも、より確実に大きくすることができる。
【００９３】
本発明の実施のさらに他の形態では、前述の図１〜図５の実施の形態において、第１搬送駆動ローラ１５ａのローラ本体２０ａの外径Ｄ１と第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外径Ｄ２とを等しく（Ｄ１＝Ｄ２）し、第１搬送駆動ローラ１５ａのローラ本体２０ａの外周面の摩擦係数を第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外周面の摩擦係数より大きくするとともに、第１搬送駆動ローラ１５ａのローラ本体２０ａの硬度を、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの硬度より低くする。その他の構成は前述の実施の各形態と同様である。
【００９４】
このような構成によれば、第１搬送ローラ対１５の搬送力を、第２搬送ローラ対１６，１７の搬送力よりも、より確実に大きくすることができる。
【００９５】
本発明の実施のさらに他の形態では、前述の図１〜図５の実施の形態において、第１搬送駆動ローラ１５ａのローラ本体２０ａの外径Ｄ１を第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外径Ｄ２より大きく（Ｄ１＞Ｄ２）するとともに、第１搬送駆動ローラ１５ａのローラ本体２０ａの外周面の摩擦係数を第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外周面の摩擦係数より大きくし、さらに、第１搬送駆動ローラ１５ａのローラ本体２０ａの硬度を、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの硬度より低くする。その他の構成は前述の実施の各形態と同様である。
【００９６】
このような構成によれば、第１搬送ローラ対１５の搬送力を、第２搬送ローラ対１６，１７の搬送力よりも、より確実に大きくすることができる。
【００９７】
本発明の実施のさらに他の形態では、前述の図１〜図５の実施の形態において、第１搬送駆動ローラ１５ａのローラ本体２０ａの外径Ｄ１と第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外径Ｄ２とを等しく（Ｄ１＝Ｄ２）し、第１搬送従動ローラ１５ｂのローラ本体２４ａの外径ｄ１を第２搬送従動ローラ１６ｂ，１７ｂのローラ本体２５ａ，２６ａの外径ｄ２より大きく（ｄ１＞ｄ２）する。その他の構成は前述の実施の各形態と同様である。
【００９８】
このような構成によれば、第１搬送従動ローラ１５ｂのローラ本体２４ａの外径ｄ１が第２搬送従動ローラ１６ｂ，１７ｂのローラ本体２５ａ，２６ａの外径ｄ２よりも大きい（ｄ１＞ｄ２）ので、第１搬送駆動ローラ１５ａのローラ本体２０ａと第１搬送従動ローラ１５ｂのローラ本体２４ａとの挟持力が、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａと第２搬送従動ローラ１６ｂ，１７ｂのローラ本体２５ａ，２６ａとの挟持力よりも大きくなる。したがって搬送するシートに対して第１搬送ローラ対１５の空回りが第２搬送ローラ対１６，１７の空回りよりも防止されるので、第１搬送ローラ対１５の搬送力を、第２搬送ローラ対１６，１７の搬送力よりも大きくすることができる。
【００９９】
本発明の実施のさらに他の形態では、前述の図１〜図５の実施の形態において、第１搬送駆動ローラ１５ａのローラ本体２０ａの外径Ｄ１と第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａの外径Ｄ２とを等しく（Ｄ１＝Ｄ２）し、第１搬送従動ローラ１５ｂのローラ軸２４ｂを第２搬送従動ローラ１６ｂ，１７ｂのローラ軸２５ｂ，２６ｂよりも搬送ローラ軸２３の近くに配置する。その他の構成は前述の実施の各形態と同様である。
【０１００】
このような構成によれば、第１搬送従動ローラ１５ｂのローラ軸２４ｂが、第２搬送従動ローラ１６ｂ，１７ｂのローラ軸２５ｂ，２６ｂよりも搬送ローラ軸２３の近くに配置されることによって、第１搬送駆動ローラ１５ａのローラ本体２０ａが第１搬送従動ローラ１５ｂのローラ本体２４ａを押し付ける力が、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２５ａ，２６ａが第２搬送従動ローラ１６ｂ，１７ｂのローラ本体２４ａを押し付ける力よりも大きくなる。これによって、第１搬送駆動ローラ１５ａのローラ本体２０ａと第１搬送従動ローラ１５ｂのローラ本体２４ａとの挟持力が、第２搬送駆動ローラ１６ａ，１７ａのローラ本体２１ａ，２２ａと第２搬送従動ローラ１６ｂ，１７ｂのローラ本体２５ａ，２６ａとの挟持力よりも大きくなる。したがって搬送するシートに対して第１搬送ローラ対１５の空回りが第２搬送ローラ対１６，１７の空回りよりも防止されるので、第１搬送ローラ対１５の搬送力を、第２搬送ローラ対１６，１７の搬送力よりも大きくすることができる。
【０１０１】
本発明の実施のさらに他の形態では、前述した実施の各形態において、第１搬送駆動ローラ１５ａおよび第２搬送駆動ローラ１６ａ，１７ａは、３個のローラ本体２０ａ，２１ａ２２ａに分割され構成されているが、分割されない軸線方向に長い１個のローラ本体で構成されてもよく、また、３個以上に分割されて構成されてもよい。
【０１０２】
本発明の実施のさらに他の形態では、前述した実施の各形態において、各ローラ本体１２ａ，１３ａ，２０ａ，２１ａ，２２ａ，２４ａ，２５ａ，２６ａの材料として、エチレンプロピレンジエン共重合ゴム（Ｅｔｈｙｌｅｎｅ　Ｐｒｏｐｙｌｅｎｅ　Ｄｉｅｎｅ
Ｍｏｎｏｍｅｒ；略称ＥＰＤＭ）を用いたが、クロロプレンゴム（Ｃｈｌｏｒｏｐｒｅｎｅ　Ｒｕｂｂｅｒ；略称ＣＲ）またはウレタンゴム（Ｕｒｅｔｈａｎｅ；略称Ｕ）などを用いてもよい。
【０１０３】
図６は、本発明の実施のさらに他の形態の画像形成装置１００を簡略化して示す断面図である。画像形成装置１００は、複写機、プリンタおよびファクシミリ装置としての機能を有するデジタル複合機であり、スキャナ部１０１、レーザ記録部１５０および後処理部２００を有している。また、画像形成装置１００は、図１〜図５の実施の形態のシート搬送装置１１およびレジスト部３４を有している。
【０１０４】
スキャナ部１０１は、原稿画像を読み取るものであり、透明ガラスから成る原稿載置台１０２、両面自動原稿送り装置１０３および原稿読取部１０４を有している。
【０１０５】
両面自動原稿送り装置（Ｒｅｖｅｒｓｉｎｇ　Ａｕｔｏｍａｔｉｃ　Ｄｏｃｕｍｅｎｔ　Ｆｅｅｄｅｒ；略称ＲＡＤＦ）１０３は、予め定められた原稿トレイにセットされた原稿を、１枚毎に透明ガラスから成る原稿載置台１０２に搬送するとともに、読み取り後の原稿を排出トレイに搬出する機能を有している。また、両面自動原稿送り装置１０３は、読み取り後の原稿を裏返し、再び原稿載置台１０２に搬送することもできる。これによって、スキャナ部１０１では、原稿における両面の画像を読み取れるようになっている。
【０１０６】
原稿読取部（Ｓｃａｎｎｅｒ　Ｕｎｉｔ；略称ＳＵ）１０４は、原稿載置台１０２の下部に配置され、原稿載置台１０２上の原稿画像を１ライン毎に読み取るものである。原稿読取部１０４は、第１走査ユニット１０５、第２走査ユニット１０６、光学レンズ１０７および光電変換素子（Ｃｈａｒｇｅ　Ｃｏｕｐｌｅｄ　Ｄｅｖｉｃｅ；略称：ＣＣＤ）ラインセンサ１０８を有している。以後、「光電変換素子ラインセンサ１０８」をＣＣＤラインセンサ１０８と呼ぶ。
【０１０７】
第１走査ユニット１０５は、光源１０９と、原稿の反射光を第２走査ユニット１０６に導く第１反射ミラー１１０とを有し、原稿載置台１０２に沿って図６の左側から右側に一定速度Ｖで移動しながら原稿を露光する。
【０１０８】
第２走査ユニット１０６は、第１走査ユニット１０５の第１反射ミラー１１０からの光を光学レンズ１０７およびＣＣＤラインセンサ１０８に導く第２反射ミラー１１１と第３反射ミラー１１２とを有し、第１走査ユニット１０５に追随してＶ／２の速度で移動する。
【０１０９】
光学レンズ１０７は、第２走査ユニット１０６からの反射光を、ＣＣＤラインセンサ１０８上で結像させるものである。ＣＣＤラインセンサ１０８は、光学レンズ１０７からの光をアナログの電気信号に変換するものである。なお、この電気信号は、図示しない画像処理部によってデジタルの画像データに変換され、図示しないメモリに記憶される。画像データは、画像処理部からの出力指令に応答して、後述するレーザ記録部１５０に出力される。
【０１１０】
また、原稿読取部１０４は、両面自動原稿送り装置１０３によって自動搬送される原稿の画像を、第１走査ユニット１０５および第２走査ユニット１０６を予め定められた露光位置に固定させた状態で読み取ることもできる。
【０１１１】
レーザ記録部１５０は、スキャナ部１０１および外部から出力される画像データに基づいてシートに画像を形成するものであり、レーザ書き込みユニット
（Ｌａｓｅｒ　Ｓｃａｎｎｉｎｇ　Ｕｎｉｔ；略称ＬＳＵ）１５１、電子写真プロセス部１５２、シート搬送装置１１およびレジスト部３４を有している。
【０１１２】
レーザ書き込みユニット１５１は、スキャナ部１０１および外部から得られた画像データに基づいて、後述する感光体ドラム１５３にレーザ光を照射して静電潜像を形成する半導体レーザ光源、半導体レーザ光源から照射されたレーザ光を等角速度偏向するポリゴンミラー、および等角速度で偏向されたレーザ光を感光体ドラム１５３上において等角速度で偏向されるように補正するｆ−θレンズなどを有している
電子写真プロセス部１５２は、感光体ドラム１５３を有しており、感光体ドラム１５３上の静電潜像を現像してトナー像を形成し、シートにトナー像を転写するものである。また、電子写真プロセス部１５２は、感光体ドラム１５３の周囲に設けられる帯電器１５４、現像機１５５、転写器１５６、クリーニング器１５７および除電気１５８などを有している。
【０１１３】
帯電器１５４は、感光体ドラム１５３を予め定められた電位に帯電させるものである。現像器１５５は、感光体ドラム１５３上の静電潜像をトナーによって現像し、トナー像を形成するものである。転写器１５６は、感光体ドラム１５３上のトナー像をシートに転写するものである。クリーニング器１５７は、転写後に残留したトナーなどを感光体ドラム１５３から除去するものである。
【０１１４】
シート搬送装置１１は、電子写真プロセス部１５２にシートを搬送するレジスト部３４にシートを搬送するとともに、シートに転写された画像を定着させ、シートを外部に排出するものであり、前述の図１〜図５の実施の形態のピックアップ部３３、分離部１４、第１搬送ローラ対１５および第２搬送ローラ対１６，１７を有している。また、シート搬送装置１１は、これらに加えて、給紙カセット１５９、手差し給紙装置１６０、定着器１６１、再供給経路１６２、排出ローラ１６３および両面複写ユニット１６４を有している。
【０１１５】
給紙カセット１５９は、画像形成装置１００の下部に設けられ、シートを収納し、ピックアップ部３３にシートを給紙するものである。手差し給紙装置１６０は、ピックアップ部３３に手差しによってシートを給紙する装置である。定着器１６１は、シートを加熱圧着することによって、シートに転写されたトナー像を定着させる。再供給経路１６２は、シートの一表面側へのトナー像の転写だけでなく、トナー像を転写されたシートの他表面側に対してトナー像を転写する場合に、シートの他表面側にトナー像が形成されるようにシートを裏返して後述する両面複写ユニット１６４にシートを供給する経路である。両面複写ユニット１６４は、両面複写用トレイを有し、トナー像が定着したシートを一時的に収納し、トナー像が形成されたシートの他表面側にトナー像を形成するためにピックアップ部３３にシートを再供給するためのものである。なお、両面複写ユニット１６４を給紙カセット１５９と交換することも可能である。排出ローラ１６３は、定着器１６１から排出されたシートを後述する後処理装置２００あるいは再供給経路１６２に供給する搬送ローラ対である。
【０１１６】
後処理装置２００は、固定トレイ２０１および上昇トレイ２０２を有し、排出ローラ１６２を通過したシートに対して、ステープル処理などの後処理を施して、固定トレイ２０１または上昇トレイ２０２に選択的にシートを排出するものである。
【０１１７】
前述の図１〜図５の実施の形態のシート搬送装置１１およびレジスト部３４を備えた画像形成装置１００によれば、前記分離部１４、前記第１搬送ローラ対１５および前記第２搬送ローラ対１６，１７を備えているので、シワ寄りのない状態でシートを電子写真プロセス部１５２に搬送することができる。したがって、シワ寄りのない状態の良好な印刷物を得ることができる。
【０１１８】
本発明の実施のさらに他の形態では、前述の図１〜図５の実施の形態のシート搬送装置１１およびレジスト部３４を備えた画像形成装置１００のシート搬送装置１１に代えて、前述の実施の他の各形態のシート搬送装置のいずれか１つを備えてもよい。
【０１１９】
前述の実施の形態では、レーザ書き込みユニット（Ｌａｓｅｒ　Ｓｃａｎｎｉｎｇ　Ｕｎｉｔ；略称ＬＳＵ）１５１を用いたが、発光ダイオード（Ｌｉｇｈｔ　Ｅｍｉｔｔｉｎｇ　Ｄｉｏｄｅ；略称ＬＥＤ）およびエレクトロルミネセント（Ｅｌｅｃｔｒｏｌｕｍｉｎｅｓｃｅｎｔ；略称ＥＬ）などの発光素子アレイを用いた固体走査型の光書き込みヘッドユニットを用いてもよい。
【０１２０】
本発明の実施のさらに他の形成では、前述した実施の各形態のシート搬送装置において、レジスト部３４を含んでシート搬送装置を構成してもよい。
【０１２１】
【発明の効果】
本発明によれば、分離部から搬送されたシートが第１搬送ローラ部および第２搬送ローラ部に到達し、前記シートが分離部から離間するまでの間、前記シートは、第１搬送ローラ部、第２搬送ローラ部および分離部と当接した状態となる。このとき、前記シートは、第１搬送ローラ部および第２搬送ローラ部から搬送力を受け、同時に、給紙ローラが搬送力を失うことによって分離部から前記搬送力とは逆向きの搬送抵抗力を受けるが、第１搬送ローラ部のシートに与える搬送力が第２搬送ローラ部のシートに与える搬送力よりも大きいので、前記搬送抵抗力によって、搬送経路に垂直な幅方向に関して、第１搬送ローラ部の位置するシート部分が、搬送経路に垂直な幅方向に関して、第２搬送ローラ部の位置するシート部分に比べ、遅れて搬送されるのを防ぐことができる。
【０１２２】
したがって、シートに生じるシワ寄りの原因である撓みの発生を防ぎ、シートをシワ寄りのない状態で搬送することができる。
【０１２３】
また本発明によれば、第１搬送ローラ部の少なくとも前記駆動されるローラの外周面の周速が、第２搬送ローラ部の少なくとも前記駆動されるローラの外周面の周速よりも大きいので、前記第１搬送ローラ部の搬送力を第２搬送ローラ部の搬送力よりも大きくすることができる。
【０１２４】
さらに本発明によれば、第１搬送ローラ部と第２搬送ローラ部とが同一の角速度で回転し、第１搬送ローラ部の少なくとも前記駆動されるローラの外径が、第２搬送ローラ部の少なくとも前記駆動されるローラの外径よりも大きいので、第１搬送ローラ部の前記駆動されるローラの外周面の周速を、第２搬送ローラ部の前記駆動されるローラの外周面の周速より大きくすることができる。
【０１２５】
さらに本発明によれば、第１搬送ローラ部の少なくとも前記駆動されるローラの外周面の摩擦係数が第２搬送ローラ部の少なくとも前記駆動されるローラの外周面の摩擦係数よりも大きいので、第１搬送ローラ部の前記駆動されるローラの外周面がシートに与える摩擦力が、第２搬送ローラ部の前記駆動されるローラの外周面がシートに与える摩擦力よりも大きくなる。したがって搬送するシートに対して第１搬送ローラ部の前記駆動されるローラの空回りが第２搬送ローラ部の前記駆動されるローラの空回りよりも防止されるので、第１搬送ローラ部の搬送力を第２搬送ローラ部の搬送力よりも大きくすることができる。
【０１２６】
さらに本発明によれば、第１搬送ローラ部の少なくとも前記駆動されるローラの硬度が第２搬送ローラ部の少なくとも前記駆動されるローラの硬度よりも低いので、第１搬送ローラ部の前記駆動されるローラのシートへの接触面積が第２搬送ローラ部の前記駆動されるローラのシートへの接触面積よりも大きくなる。したがって搬送するシートに対して第１搬送ローラ部の前記駆動されるローラの空回りが第２搬送ローラ部の前記駆動されるローラの空回りよりも防止されるので、第１搬送ローラ部の搬送力を第２搬送ローラ部の搬送力よりも大きくすることができる。
【０１２７】
さらに本発明によれば、前記分離部、前記第１搬送ローラ部および前記第２搬送ローラ部を有するシート搬送装置を備えているので、シワ寄りのない状態で印刷部にシートを搬送することができる。したがって、シワ寄りのない状態の良好な印刷物を得ることができる。
【図面の簡単な説明】
【図１】本発明の実施の一形態のシート搬送装置１１を簡略化して示す斜視図である。
【図２】シート搬送装置１１およびレジスト部３４を簡略化して示す断面図である。
【図３】シート搬送装置１１およびレジスト部３４の電気的および機械的な構成を示すブロック図である。
【図４】シート搬送装置１１およびレジスト部３４の動作を説明するためのフローチャートである。
【図５】シート搬送装置１１およびレジスト部３４の動作を説明するためのタイムチャートである。
【図６】本発明の実施のさらに他の形態の画像形成装置１００を簡略化して示す断面図である。
【図７】従来の技術のシート搬送装置１を示す簡略化した平面図である。
【符号の説明】
１１　シート搬送装置
１２　給紙ローラ
１２ａ　給紙ローラ１２のローラ本体
１２ｂ　給紙ローラ１２のローラ軸
１３　給紙分離ローラ
１３ａ　給紙分離ローラ１３のローラ本体
１３ｂ　給紙分離ローラ１３のローラ軸
１４　分離部
１５　第１搬送ローラ対
１５ａ　第１搬送駆動ローラ
１５ｂ　第１搬送従動ローラ
１６，１７　第２搬送ローラ対
１６ａ，１７ａ　第２搬送駆動ローラ
１６ｂ，１７ｂ　第２搬送従動ローラ
１８　給紙ローラクラッチ
１９　トルクリミッタ
２０ａ　第１搬送駆動ローラ１５ａのローラ本体
２０ｂ　第１搬送駆動ローラ１５ａのローラ軸
２１ａ，２２ａ　第２搬送駆動ローラ１６ａ，１７ａのローラ本体
２１ｂ，２２ｂ　第２搬送駆動ローラ１６ａ，１７ａのローラ軸
２３　搬送ローラ軸
２３ａ　搬送ローラクラッチ
２４ａ　第１搬送従動ローラ１５ｂのローラ本体
２４ｂ　第１搬送従動ローラ１５ｂのローラ軸
２５ａ，２６ａ　第２搬送従動ローラ１６ｂ，１７ｂのローラ本体
２５ｂ，２６ｂ　第２搬送従動ローラ１６ｂ，１７ｂのローラ軸
３１　給紙部
１００　画像形成装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is provided in an image forming apparatus having a printing function such as a copying machine, a printer, and a facsimile apparatus, and takes out a sheet from a sheet feeding unit and conveys the sheet to a printing unit, and an image forming apparatus including the sheet conveying device. Equipment related.
[0002]
[Prior art]
FIG. 7 is a simplified plan view showing the sheet conveying apparatus 1 of the related art. 2. Description of the Related Art In an image forming apparatus having a printing function such as a copying machine, a printer, and a facsimile machine, a paper feed cassette for storing a sheet 6 as printing paper used for printing is provided at a lower portion of a main body, for example. . When printing is performed, the sheet 6 in the sheet cassette is taken out of the sheet cassette and fed to the printing unit by the sheet conveying device 1.
[0003]
The sheet conveying apparatus 1 is configured to be able to satisfactorily convey frequently used fixed sheets, but may use special sheets other than the fixed sheets. In particular, when a special size sheet such as a small size sheet, a thick sheet such as a postcard, and a thin sheet are used, the sheet feeding cassette may not be used in some cases. Further, even when the sheet cassette can be used, the fixed sheets in the sheet cassette need to be replaced with special sheets, and the fixed sheets must be returned to the sheet cassette after printing. As described above, in order to eliminate the need to replace the sheets in the sheet cassette from the fixed sheets to the special sheets, some image forming apparatuses include a manual sheet feed tray in addition to the sheet cassette.
[0004]
The manual paper feed tray exposes a sheet mounting surface to the outside, and is attached to a paper feed port provided near the printing unit. If this manual sheet feed tray is used, it is possible to feed a special sheet directly to the printing unit without replacing a fixed sheet in the sheet feed cassette with a special sheet.
[0005]
Further, in recent years, applications of the image forming apparatus have been expanded, and the types of sheets used have been increasing. As a result, many image forming apparatuses are provided with a sheet feeding device in which a plurality of sheet feeding cassettes are stacked in a multi-stage manner, and a part of the sheet feeding cassette can be dedicated to special sheets.
[0006]
Sheets 6 are stacked on the above-described sheet feeding cassette and the manual sheet feeding tray, and the stacked sheets 6 are conveyed one by one to the printing unit by the sheet conveying device 1. In such a sheet conveying apparatus 1, a separating section 2 and a conveying roller section 4 are provided.
[0007]
The separation unit 2 is arranged at the most upstream side in the conveyance direction B on the conveyance path and in the width direction perpendicular to the conveyance path, that is, at the center in the left-right direction in FIG. 7, and includes a separation roller pair 3 including a driving roller and a driven roller. have. The driven roller is provided with a torque limiter. When a plurality of sheets, for example, two sheets, simultaneously enter between the driving roller and the driven roller and the torque of the driven roller is increased, the torque limiter stops rotation of the driven roller and stops the rotation. Thus, the sheet that is in contact with the driving roller receives the conveyance force from the driving roller, and the sheet that is in contact with the driven roller receives a sliding resistance force opposite to the conveyance force from the driven roller. In this way, only the sheet that is in contact with the drive roller is conveyed downstream of the separation unit 2 in the conveyance direction indicated by the arrow B, so that double feeding can be prevented. In addition, the separation unit 2 may include a fixed separation pad instead of the driven roller.
[0008]
The transport roller unit 4 is provided downstream of the separation unit 2 in the transport direction B, and has one pair of transport rollers 4a at the center in the width direction perpendicular to the transport path and two pairs of transport rollers at both sides of the pair. It has a pair of rollers 4b and 4c. In some cases, the transport roller unit 4 is configured by an integral roller that is longer in the axial direction than each roller of the separation unit 2. The transport roller unit 4 applies a transport force to the sheet 6 transported from the separation unit 2 and transports the sheet 6 downstream of the transport roller unit 4 in the transport direction B.
[0009]
In the separation unit 2 and the conveyance roller unit 4 of such a sheet conveyance device 1, the driving roller of the separation unit 2 gives a conveyance force for conveying the sheet 6 to the conveyance roller unit 4. Upon or after reaching, the rotation of the driving roller by the driving force of the driving source is stopped. The driving roller stopped rotating by the driving force is driven to rotate by the sheet 6 conveyed by the conveying roller unit 4. That is, the separating unit 2 applies a conveyance resistance force opposite to the conveyance force to the sheet 6 that has reached the conveyance roller unit 4.
[0010]
Therefore, the sheet 6 receives the conveying force from the conveying roller unit 4 from when the leading end portion of the sheet 6 reaches the conveying roller unit 4 to when the rear end portion of the sheet 6 separates from the separating unit 2. However, it receives a conveyance resistance force from the separation unit 2 in a direction opposite to the conveyance force.
[0011]
[Problems to be solved by the invention]
In the above-described sheet conveying device 1, the central portion in the width direction perpendicular to the conveying path of the sheet 6 is conveyed later than the both sides in the width direction perpendicular to the conveying path of the sheet 6 by the conveying resistance force received from the separation unit 2. As a result, the regions 5a and 5b between the pair of conveying rollers 4b and 4c on both sides of the sheet 6 and the pair of rollers 3 of the separation unit 2 are bent, causing wrinkles. In particular, the bending of the regions 5a and 5b as described above occurs remarkably when a sheet having a low stiffness is used or when the sheet 6 is conveyed in a direction parallel to the fiber direction of the sheet 6. This bending causes the sheet 6 to be wrinkled, and the sheet 6 is conveyed to the printing unit in a wrinkled state, so that a good printed matter cannot be obtained.
[0012]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet conveying apparatus and an image forming apparatus capable of preventing a sheet from wrinkling by preventing a sheet from bending when the sheet is conveyed.
[0013]
[Means for Solving the Problems]
The present invention provides a sheet feeding roller that applies a conveying force to a sheet fed from a sheet feeding unit from one surface side, and supports the sheet from the other surface side, and when the conveying resistance increases, the conveying force is A separating portion having a support that gives a sliding resistance force in the opposite direction,
A first transport roller unit that is provided downstream of the paper feed roller in the transport direction, has a first transport roller pair that vertically forms a pair with respect to a transport path through which the sheet passes, and has at least one roller driven; When,
A second transport roller pair, which is provided on both sides in the width direction perpendicular to the transport path with respect to the first transport roller unit, forms a pair vertically with respect to the transport path, and has at least one roller driven by a second transport roller pair; And a transport roller section,
The separation unit loses the conveyance force to the sheet when or after the sheet reaches the first conveyance roller unit and the second conveyance roller unit,
The first transporting roller unit has a transporting force greater than a transporting force to the sheet by the second transporting roller unit.
[0014]
According to the present invention, the sheet feeding roller provided in the separation unit applies a conveying force from one surface side of the sheet fed from the sheet feeding unit, and at the same time, the support provided in the separation unit includes the sheet Is supported from the other surface side, and when the transport resistance increases, a sliding resistance force opposite to the transport force is applied. In this way, the separation unit including the paper feed roller and the support conveys the sheet to the first conveyance roller unit and the second conveyance roller unit.
[0015]
The first transport roller and the second transport roller apply a transport force to the sheet transported from the separation unit, but the first transport roller has a lower transport force than the second transport roller. Also have a large conveying force.
[0016]
The sheet feeding roller of the separation unit loses the conveying force to the sheet when the sheet reaches the first conveyance roller unit and the second conveyance roller unit or after the sheet reaches the first conveyance roller unit and the second conveyance roller unit. The sheet is rotated by the sheet conveyed by the conveying roller section.
[0017]
In such a sheet conveyance device, the sheet conveyed from the separation unit reaches the first conveyance roller unit and the second conveyance roller unit, and the sheet is kept in the first position until the sheet is separated from the separation unit. The state is in contact with the transport roller unit, the second transport roller unit, and the separation unit. At this time, the sheet receives the conveyance force from the first conveyance roller unit and the second conveyance roller unit, and at the same time, receives the conveyance resistance force opposite to the conveyance force by the separation unit. Since the conveying force applied to the sheet is greater than the conveying force applied to the sheet by the second conveying roller unit, the sheet resistance at which the first conveying roller unit is positioned in the width direction perpendicular to the conveying path is conveyed by the conveying resistance force. In the width direction perpendicular to the path, it is possible to prevent the sheet from being conveyed later than the sheet portion where the second conveying roller portion is located.
[0018]
Therefore, it is possible to prevent the sheet from being bent, which is a cause of wrinkling, and to convey the sheet without wrinkling.
[0019]
Further, according to the present invention, the peripheral speed of at least the outer peripheral surface of the driven roller of the first transport roller unit is made larger than the peripheral speed of at least the outer peripheral surface of the driven roller of the second transport roller unit. Thus, the conveying force of the first conveying roller unit is made larger than the conveying force of the second conveying roller unit.
[0020]
According to the present invention, the peripheral speed of at least the outer peripheral surface of the driven roller of the first transport roller portion is higher than the peripheral speed of at least the outer peripheral surface of the driven roller of the second transport roller portion. The transport force of the first transport roller unit can be made larger than the transport force of the second transport roller unit.
[0021]
Also, in the present invention, the first transport roller unit and the second transport roller unit rotate at the same angular velocity, and the outer diameter of at least the driven roller of the first transport roller unit is set to the second transport roller unit. By making the outer diameter of at least the driven roller of the roller unit larger, the conveying force of the first conveying roller unit is made larger than the conveying force of the second conveying roller unit.
[0022]
According to the present invention, the first transport roller unit and the second transport roller unit rotate at the same angular velocity, and the outer diameter of at least the driven roller of the first transport roller unit is at least the second transport roller unit. Since the outer diameter of the driven roller is greater than the outer diameter of the driven roller, the peripheral speed of the outer peripheral surface of the driven roller of the first transport roller unit is set to be larger than the outer peripheral surface of the driven roller of the second transport roller unit. Can be larger.
[0023]
Further, in the invention, it is preferable that a friction coefficient of at least an outer peripheral surface of the driven roller of the first transport roller unit is larger than a friction coefficient of at least an outer peripheral surface of the driven roller of the second transport roller unit. Thus, the conveying force of the first conveying roller unit is made larger than the conveying force of the second conveying roller unit.
[0024]
According to the present invention, the friction coefficient of at least the outer peripheral surface of the driven roller of the first transport roller portion is larger than the friction coefficient of at least the outer peripheral surface of the driven roller of the second transport roller portion. The frictional force applied to the sheet by the outer peripheral surface of the driven roller of the transport roller unit is larger than the frictional force applied to the sheet by the outer peripheral surface of the driven roller of the second transport roller unit. Therefore, the idle rotation of the driven roller of the first transport roller unit is prevented more than the idle rotation of the driven roller of the second transport roller unit with respect to the sheet to be transported, so that the transport force of the first transport roller unit is reduced. It can be made larger than the conveying force of the second conveying roller section.
[0025]
In addition, the present invention may be configured such that the hardness of at least the driven roller of the first transport roller unit is lower than the hardness of at least the driven roller of the second transport roller unit. Is made larger than the conveying force of the second conveying roller unit.
[0026]
According to the present invention, since the hardness of at least the driven roller of the first transport roller unit is lower than the hardness of at least the driven roller of the second transport roller unit, the first transport roller unit is driven. The contact area of the roller with the sheet is larger than the contact area of the driven roller of the second transport roller unit with the sheet. Therefore, the idle rotation of the driven roller of the first transport roller unit is prevented more than the idle rotation of the driven roller of the second transport roller unit with respect to the sheet to be transported, so that the transport force of the first transport roller unit is reduced. It can be made larger than the conveying force of the second conveying roller section.
[0027]
According to another aspect of the present invention, there is provided an image forming apparatus including the sheet conveying device.
[0028]
According to the present invention, since the sheet conveying apparatus including the separating unit, the first conveying roller unit, and the second conveying roller unit is provided, the sheet can be conveyed to the printing unit without wrinkling. . Therefore, a good printed matter without wrinkles can be obtained.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a simplified perspective view showing a sheet conveying apparatus 11 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a simplified sheet conveying apparatus 11 and a resist unit 34. The sheet conveying device 11 of the present embodiment applies a conveying force to the sheet S fed from the sheet feeding unit 31 in the direction of the arrow A from one surface side facing upward in FIG. The sheet feeding roller 12 and the sheet S are supported from the other surface side facing downward in FIG. 2, and when the conveyance resistance is increased, the sheet S is a support that provides a sliding resistance force in a direction opposite to the conveyance force. A separation unit 14 having a paper separation roller 13 and disposed at the center in the width direction perpendicular to the paper surface of FIG. 1 of the conveyance path of the sheet S conveyed in the conveyance direction A; A first conveying roller pair 15 provided on the downstream side in the direction A and vertically forming a pair with respect to the conveying path through which the sheet S passes, and provided on both sides in the width direction perpendicular to the conveying path with respect to the first conveying roller pair 15 And a second pair vertically And a feed roller pair 16, 17.
[0030]
The paper feed roller 12 has a roller body 12a rotatably held around a rotation axis parallel to the width direction perpendicular to the conveyance path, and a roller shaft 12b provided coaxially with the roller body 12a. The paper feed roller 12 is provided with a paper feed roller clutch 18 for transmitting and blocking a driving force from a drive motor 51 shown in FIG. 3 to be described later to the roller main body 12a. The paper feed separation roller 13 has a roller main body 13a rotatably held around a rotation axis parallel to the axis of the paper feed roller 12, and a roller shaft 13b provided coaxially with the roller main body 13a. The paper feed separation roller 13 is provided with a torque limiter 19 for stopping the rotation of the roller body 13a of the paper feed separation roller 13 and stopping the rotation when a torque higher than a predetermined torque as the conveyance resistance acts. . Further, the paper feed roller 12 and the paper feed separation roller 13 form a pair so as to sandwich the sheet S and resiliently come into contact with each other at a central portion in the width direction perpendicular to the conveyance path. Be placed.
[0031]
The first transport roller pair 15 has a first transport drive roller 15a and a first transport driven roller 15b. The first transport drive roller 15a has a roller body 20a rotatably held around a rotation axis parallel to the axis of the paper feed roller 12, and a roller shaft 20b provided coaxially with the roller body 20a.
[0032]
The first transport driven roller 15b has a roller body 24a rotatably held around a rotation axis parallel to the axis of the paper feed roller 12, and a roller shaft 24b provided coaxially with the roller body 24a. Further, the first transport drive roller 15a and the first transport driven roller 15b make a pair vertically and resiliently come into contact with each other so as to pinch the sheet S, and the width direction perpendicular to the transport path. It is located in the center.
[0033]
The second transport roller pair 16, 17 includes second transport drive rollers 16a, 17a and second transport driven rollers 16b, 17b. The second transport drive rollers 16a and 17a are composed of roller bodies 21a and 22a rotatably held around a rotation axis parallel to the axis of the paper feed roller 12, and a roller shaft provided coaxially with the roller bodies 21a and 22a. 21b and 22b.
[0034]
The second transport driven rollers 16b and 17b are composed of roller bodies 25a and 26a rotatably held around a rotation axis parallel to the axis of the paper feed roller 12, and a roller shaft provided coaxially with the roller bodies 25a and 26a. 25b and 26b. The second transport driving rollers 16a, 17a and the second transport driven rollers 16b, 17b form a pair up and down so as to sandwich the sheet S and resiliently come into contact with each other. It is arranged on both sides of the pair 15.
[0035]
The first transport drive roller 15a and the second transport drive rollers 16a, 17a have the same rotation axis, and the roller shaft 20b of the first transport drive roller 15a and the second transport drive roller 16a, 17a The roller shafts 21b and 22b form a continuous roller shaft. The roller shaft 20b of the first transport drive roller 15a and the roller shafts 21b and 22b of the second transport drive rollers 16a and 17a are connected to form a transport roller shaft 23. In addition, a driving force from a driving motor 51 shown in FIG. 3 described later is transmitted to the transport roller shaft 23 to the roller body 20a of the first transport driving roller 15a and the roller bodies 21a and 22a of the second transport driving rollers 16a and 17a. A transfer roller clutch 23a shown in FIG.
[0036]
The roller body 20a of the first transport drive roller 15a and the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a are arranged so as to come into contact with the lower surface of the sheet S facing downward in FIG. Further, in the present embodiment, the first transport driven roller 15b and the second transport driven rollers 16b, 17b have a rotation axis on a common straight line.
[0037]
Each of the above-mentioned roller bodies 12a, 13a, 20a, 21a, 22a, 24a, 25a, 26a has a cylindrical outer peripheral surface and is made of, for example, ethylene propylene diene copolymer rubber (Ethylene Propylene Diene Monomer; abbreviated EPDM). It is made of a flexible and resilient material.
[0038]
The outer diameter D1 of the roller body 20a of the first transport drive roller 15a is selected to be larger than the outer diameter D2 of the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a by ΔD (D1 = D2 + ΔD). The difference ΔD (= D1−D2) between these outer diameters D1 and D2 is selected to be 0.25 mm to 0.35 mm, and the outer diameter D2 of the roller main bodies 21a and 22a of the second transport drive rollers 16a and 17a is For example, 15.93 mm is selected. The outer diameter d1 of the roller body 24a of the first transport driven roller 15b and the outer diameter d2 of the roller bodies 25a and 26a of the second transport driven rollers 16b and 17b are equal (d1 = d2).
[0039]
The first transport roller pair 15 and the second transport roller pairs 16 and 17 are located at a position where the paper feed roller 12 and the paper feed separation roller 13 sandwich the sheet S from a position where the first transport roller pair 15 sandwiches the sheet S. The distance parallel to the conveyance path to the position where the second conveyance roller pair 16 and 17 sandwiches the sheet S is arranged at a position where the length of the short side of the predetermined minimum size sheet S is shorter.
[0040]
Further, the sheet conveying apparatus 11 of the present embodiment is configured to include a sheet feeding unit 31 provided at the most upstream side of the conveying path in the conveying direction, and a pickup unit 33 provided above the sheet feeding unit 31. . A registration unit 34 is provided downstream of the first transport roller pair 15 and the second transport roller pairs 16 and 17 in the transport direction A.
[0041]
The sheet feeding unit 31 is for stacking and storing the conveyed sheets S. Here, the sheet S is realized by printing paper. The paper feed unit 31 includes a paper feed cassette 159 and a manual paper feed device 160 shown in FIG.
[0042]
The pickup unit 33 takes out the sheets S one by one from the sheets 32 stacked in the sheet feeding unit 31 and feeds the sheets S to the separation unit 14. The pickup unit 33 includes an electromagnetic solenoid 35, a lever 36, an arm 37, and a pickup roller. 38, a belt 39 and a spring 40. The pickup roller 38 includes a roller body 38a rotatably held around a rotation axis parallel to the axis of the paper feed roller 12 by one end of the arm 37, and a roller shaft 38b provided coaxially with the roller body 38a. Have.
[0043]
The other end of the arm 37 is held by the roller shaft 12 b of the paper feed roller 12 so as to be angularly displaceable about the axis of the paper feed roller 12. The belt 39 is wound around a pulley (not shown) provided on the roller shaft 12 b of the paper feed roller 12 and a pulley (not shown) provided on the roller shaft 38 b of the pickup roller 38, and is stretched. Is transmitted to and blocked from the roller shaft 38b of the pickup roller 38, and the roller body 38a of the pickup roller 38 is rotated and stopped.
[0044]
The intermediate portion of the lever 36 is held so as to be angularly displaceable about an angular displacement axis parallel to the axis of the paper feed roller 12. One end of the lever 36 is held by an intermediate portion of the arm 37 so as to be angularly displaceable about an angular displacement axis parallel to the axis of the paper feed roller 12.
[0045]
The electromagnetic solenoid 35 has a movable iron core 35a, and the movable iron core 35a is provided so as to be able to move forward or backward in the transport direction. The tip of the movable iron core 35 a is connected to the other end of the lever 36.
[0046]
When the pickup unit 33 is in a sheet feeding state in which the sheet S is fed to the separation unit 14, the roller body 38 a of the pickup roller 38 comes into contact with the uppermost sheet S stacked on the sheet feeding unit 31, and The sheet S can be angularly displaced between a sheet feeding position P1 at which the sheets S can be taken out one by one and a retracted position P2 retracted above the sheet feeding position P1. Further, one end of the tension spring 40 is fixed to a fixing position of an unillustrated body and the other end is fixed to an intermediate portion of the arm 37 so that the pickup roller 38 is stably disposed at the retreat position P2. The arm 37 is spring-biased upward.
[0047]
When the movable iron core 35a of the electromagnetic solenoid 35 is retracted, the lever 36 is angularly displaced, and the arm 37 is turned around the axis of the paper feed roller 12 against the spring force of the spring 40. Then, the roller body 38a of the pickup roller 38 comes into contact with the uppermost sheet S of the sheet feeding section 31 after being displaced from the retreat position P2 to the sheet feeding position P1. When the roller shaft 12b of the paper feed roller 12 is driven to rotate, the roller main body 38a of the pickup roller 38 rotates the roller shaft 12b of the paper feed roller 12 via a pulley and a belt 39 (not shown). The rotation is transmitted to the roller shaft 38b of 38.
[0048]
The registration unit 34 makes the leading end of the sheet S parallel to the width direction perpendicular to the conveyance path, temporarily stops the sheet S, and feeds the sheet S to the printing unit at an appropriate timing. And a sheet detector 44 for detecting the detected sheet S and providing a detection result to a control unit 52 shown in FIG. The sheet detector 44 is realized by, for example, a photo sensor including a contact type actuator 44a.
[0049]
The registration roller pair 41 has registration rollers 42 and 43. The registration rollers 42 and 43 include roller bodies 42a and 43a rotatably held around a rotation axis parallel to the axis of the paper feed roller 12, and roller shafts 42b and 43b provided coaxially with the roller bodies 42a and 43a. A registration roller clutch for transmitting and blocking a driving force from a driving motor 51 shown in FIG. 3 to be described later to a roller shaft 43b of the registration roller 43 which contacts the other surface side of the sheet S facing downward in FIG. 45 is provided. The sheet detector 44 is provided close to the registration roller pair 41 on the upstream side in the transport direction.
[0050]
The registration roller pair 42 is configured to convey the sheet from the position where the first conveyance roller pair 15 nips the sheet S and the position where the second conveyance roller pair nips the sheet S to the position where the registration roller pair 42 nips the sheet S. The sheet S is arranged at a position where the distance parallel to the path is smaller than the length of the short side of the sheet S of the minimum size determined in advance.
[0051]
FIG. 3 is a block diagram illustrating an electrical and mechanical configuration of the sheet conveying device 11 and the registration unit 34. The control unit 52 controls ON / OFF of the drive motor 51, the electromagnetic solenoid 35, the paper feed roller clutch 18, the transport roller clutch 23a, and the registration roller clutch 45. The drive motor 51 is controlled so as to start driving in an ON state and stop driving in an OFF state. The paper feed roller clutch 18, the transport roller clutch 23a, and the registration roller clutch 45 receive a driving force from the drive motor 51 in the on state, rotate the respective roller bodies 12a, 20a, 21a, 22a, 43a, respectively, and turn off the roller bodies. To control the driving force from the driving motor 51 to be cut off. The electromagnetic solenoid 35 is controlled so that the movable iron core 35a moves forward in the on state, and retracts the movable iron core 35a in the off state.
[0052]
The sheet detector 44 is connected to the control unit 52, detects the position of the sheet being conveyed, and gives the detection result to the control unit 52. The control unit 52 controls ON / OFF of the registration roller clutch 45 based on the detection result of the sheet detector 44 and the input instruction of the user.
[0053]
FIG. 4 is a flowchart for explaining the operation of the sheet conveying device 11 and the registration unit 34, and FIG. 5 is a time chart for explaining the operation of the sheet conveying device 11 and the registration unit 34. First, in step s1, the sheet conveying device 11 enters the sheet feeding state and proceeds to step 2. Next, in step s2, the drive motor 51, the electromagnetic solenoid 35, the paper feed roller clutch 18, and the transport roller clutch 23a are turned on. When the drive motor 51, the electromagnetic solenoid 35, and the paper feed roller clutch 18 are turned on, the roller body 38a of the pickup roller 38 rotates around the axis on the uppermost sheet S stacked on the paper feed unit 31. The sheet S comes into contact with the sheet and is conveyed toward the separation unit 14.
[0054]
Next, in step s3, when the number of the sheets S conveyed to the separation unit 14 is one, the sheets S are nipped by the paper feed roller 12 and the paper The paper feed roller 12 receives a transport force in the transport direction from the roller main body 12a of the paper feed roller 12 that rotates around the axis by the rotational driving force from the roller, and is transported toward the first transport roller pair 15 and the second transport roller pairs 16 and 17. At this time, the roller main body 13a of the sheet separation roller 13 is rotated by the conveyance of the sheet S.
[0055]
When the number of sheets S conveyed to the separation unit 14 is plural, for example, two first sheets S1 and second sheets S2 shown in FIG. Immediately after being nipped, a torque higher than a predetermined value acts on a torque limiter 19 provided on the paper separating roller 13, and the roller body 13 a of the paper separating roller 13 is stopped from rotating and stopped. . At this time, the first sheet S1 in contact with the roller main body 12a of the paper feed roller 12 receives a conveying force in the conveying direction by the rotation of the roller main body 12a of the paper feed roller 12, and the first conveying roller pair 15 and the second The sheet is conveyed toward the pair of conveying rollers 16 and 17. The second sheet S2 that is in contact with the roller body 13a of the sheet separation roller 13 receives a sliding resistance force opposite to the conveying force from the roller body 13a of the sheet separation roller 13 whose rotation has been stopped. Therefore, the first sheet S1 is conveyed toward the first conveying roller pair 15 and the second conveying roller pairs 16 and 17, and the second sheet S2 is moved on the roller main body 13a of the sheet separating roller 13 by the sliding resistance. , It is possible to prevent a plurality of sheets S from being conveyed.
[0056]
Next, in step s4, the leading end of the sheet S conveyed from the separation unit 14 is pinched by the first pair of conveying rollers 15, and simultaneously, by the second pair of conveying rollers 16, 17. At this time, in order to further prevent the plurality of sheets S from being conveyed, the first conveyance roller is provided by a sensor (not shown) provided downstream of the first conveyance roller pair 15 and the second conveyance roller pairs 16 and 17 in the conveyance direction. The leading edge of the sheet S that has reached the roller pair 15 and the second transport roller pairs 16 and 17 is detected, and thereafter, the paper feed roller clutch 18 and the electromagnetic solenoid 35 are turned off. As a result, the paper feed roller 12 loses the rotational driving force. At this time, the sheet S has its rear end sandwiched between the paper feed roller 12 and the paper feed separation roller 13, and its leading end sandwiched by the first transport roller pair 15. , 17.
[0057]
In such a state, the roller body 20a of the first transport drive roller 15a and the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a are rotated by the rotational driving force from the transport roller clutch 23a provided on the transport roller shaft 23a. Rotates at the same angular velocity to apply a conveying force to the sheet S conveyed from the separation unit 14, but the outer diameter D1 of the roller main body 20a of the first conveying driving roller 15a is changed to the roller main body of the second conveying driving rollers 16a and 17a. Since the outer diameter D2 of the first transport drive roller 15a is larger than the outer diameter D2 of the first transport drive roller 15a (D1> D2), the peripheral speed of the outer peripheral surface of the roller body 20a of the first transport drive roller 15a is lower than that of the second transport drive roller 16a, 17a. , 22a are larger than the peripheral speed of the outer peripheral surface.
[0058]
Therefore, the second conveying roller pair 16, 17 applies a conveying force in the conveying direction to the sheet S conveyed from the separation unit by the rotation of the roller main bodies 21a, 22a of the second conveying drive rollers 16a, 17a. At the same time, the first transport roller pair 15 gives a greater transport force in the transport direction than the second transport drive roller pair 16 and 17 due to the rotation of the roller body 20a of the first transport drive roller 15a.
[0059]
At this time, in the separation section 14, when the rotation of the paper feed separation roller 13 is not stopped by the torque limiter 19, the roller body 12a of the paper feed roller 12 and the roller body 13a of the paper feed separation roller 13 The sheet S conveyed by the conveying roller pair 15 and the second conveying roller pairs 16 and 17 is driven to rotate. Alternatively, when the rotation of the paper feed separation roller 13 is stopped by the torque limiter 19, the roller body 12 a of the paper feed roller 12 moves the sheet S transported by the first transport roller pair 15 and the second transport roller pairs 16 and 17. It is driven to rotate.
[0060]
Accordingly, the separation unit 14 is driven by the rotation of the roller main body 12a of the paper feed roller 12 and the roller main body 13a of the paper feed separation roller 13 with respect to the sheet S, or by the rotation of the roller main body 12a of the paper feed roller 12. When the roller body 13a rotates and the roller main body 13a of the paper feed separation roller 13 stops rotating, a conveyance resistance force in a direction opposite to the conveyance force is applied.
[0061]
As described above, after the leading end portion of the sheet S is nipped by the first conveying roller pair 15 and simultaneously nipped by the second conveying roller pairs 16 and 17, the rear end portion of the sheet S is Until the sheet S is separated from the roller main body 13a of the sheet separation roller 13, the sheet S receives a conveyance resistance force opposite to the conveyance force by the sheet supply roller 12 and the sheet separation roller 13, Since the conveying force received by the sheet S by the first conveying roller pair 15 is larger than the conveying force received by the sheet S by the second conveying roller pair 16 and 17, the first conveying roller is moved in the width direction perpendicular to the conveying path. The sheet S portion where the pair 15 is located can be prevented from being transported later in the width direction perpendicular to the transport path than the sheet S portion where the second transport roller pairs 16 and 17 are located. . That is, since it is possible to prevent the central portion in the width direction of the sheet S from being sent and conveyed as compared with both side portions in the width direction of the sheet S, it is possible to prevent the occurrence of the bending which is a cause of the wrinkling of the sheet S. it can.
[0062]
Next, in step s5, the position of the sheet S conveyed from the first conveying roller pair 15 and the second conveying roller pairs 16 and 17 to the registration roller pair 41 is detected by the sheet detector 44. Thereafter, the leading end of the sheet S is brought into contact with the pair of registration rollers 41 to make the axes of the registration rollers 42 and 43 parallel to the leading end of the sheet S. The clutch 23a is turned off, the rotation of the roller body 20a of the first transport drive roller 15a and the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a is temporarily stopped, and the sheet S is held.
[0063]
Next, in step s6, the registration roller clutch 45 is turned on at an appropriate timing based on the detection result of the sheet detector 44 and the input instruction of the user by the control unit 52.
[0064]
Next, in step s7, the sheet S is conveyed to the printing unit by the roller body 43a of the registration roller 43, which is held between the registration roller pair 41 and rotated around the axis by the rotation driving force from the registration roller clutch 45. I do. Here, the printing unit is an electrophotographic processing unit 152 shown in FIG. 6 described later provided in the image forming apparatus.
[0065]
Table 1 is a table showing experimental results of paper passing performance in the sheet conveying device 11 according to the present embodiment.
[0066]
[Table 1]

[0067]
In this paper-passing performance experiment, the outer diameter D2 of the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a was 15.95 mm, and the outer diameter D1 of the roller body 20a of the first transport drive roller 15a was D1 = D2 + ΔD. And In the experiment on the paper passing performance, a thin sheet, a normal sheet and a thick sheet were used. Here, the thin sheet has a basis weight of 52 g / m. ² 80 g / m or more ² Sheets in the following range, with normal sheets having a basis weight of 81 g / m ² More than 105g / m ² The following range sheets, the thick sheet has a basis weight of 106 g / m ² More than 300g / m ² Sheets in the following range. The sheet in this experiment is a sheet made of paper, and is conveyed with the direction of the eyes of the paper and the conveying direction parallel.
[0068]
In Table 1, the state of the sheet being conveyed is represented by x for a wrinkled state, and is indicated by と for a bent state which is considered to cause wrinkling, and the sheet is conveyed only by the first conveying roller pair 15. Is indicated by □, and a state in which no bending which may cause wrinkles is generated is indicated by ○.
[0069]
Assuming that the difference ΔD (= D1−D2) between the outer diameters D1 and D2 is 0 mm and the thin sheet, the ordinary sheet, and the thick sheet are respectively conveyed, the ordinary sheet and the thick sheet are not bent. Although the sheet was satisfactorily conveyed in the absence state, the thin sheet was bent, and an abnormal sound was generated along with the conveyance, and the sheet was conveyed in a wrinkled state.
[0070]
The difference ΔD (= D1−D2) between the outer diameters D1 and D2 is set to 0.15 mm, and the thin sheet, the ordinary sheet, and the thick sheet are respectively conveyed. As a result, the ordinary sheet and the thick sheet are bent. Although the thin sheet was conveyed satisfactorily, the bending of the thin sheet was reduced as compared with the case where the sheet was conveyed with the difference ΔD (= D1−D2) between the outer diameters D1 and D2 being 0 mm. Was transported in a state in which
[0071]
The difference ΔD (= D1−D2) between the outer diameters D1 and D2 is set to 0.25 mm and 0.35 mm, and a thin sheet, a normal sheet, and a thick sheet are respectively conveyed. Both the thick sheet and the thick sheet were satisfactorily conveyed in a state in which no warping causing wrinkling occurred.
[0072]
The difference ΔD (= D1−D2) between the outer diameters D1 and D2 is set to 0.45 mm, and as a result of transporting a thin sheet, a normal sheet, and a thick sheet, respectively, a thin sheet, a normal sheet, and a thick sheet are conveyed. Were transported only by the first transport roller pair 15, and were rarely transported obliquely to the transport direction.
[0073]
From the experimental results shown in Table 1, the outer diameter D2 of the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a is 15.93 mm, and the difference ΔD (= D1−D2) between the outer diameters D1 and D2 is , 0.25 mm to 0.35 mm, it can be seen that any of a thin sheet, a normal sheet and a thick sheet can be prevented from bending and can be conveyed favorably without wrinkles.
[0074]
In the above-described experiment, when the difference ΔD between D1 and D2 (= D1−D2) is 0.25 mm, the conveying force of the first conveying roller pair 15 is 1000 gf to 1150 gf, and the second conveying roller pair 16 and 17 is used. 550 gf to 650 gf, and the conveyance resistance generated by the separation unit 14 in the opposite direction to the conveyance force is 450 gf to 550 gf.
[0075]
Further, according to another experiment result of the sheet passing performance in the sheet conveying device 11 of the present embodiment, the sheet conveying device 11 has the roller main bodies 21a. When the outer diameter D2 of 22a is 15.95 mm and the difference ΔD (= D1−D2) between D1 and D2 is 0.25 mm to 0.35 mm, the basis weight is 52 g / m. ² More than 300g / m ² It has been found that the following range of sheets can be satisfactorily conveyed in a state in which there is no warping that causes wrinkling.
[0076]
According to the sheet conveying apparatus 11 of the present embodiment as described above, the roller main body 12a of the sheet feeding roller 12 provided in the separation unit 14 is configured such that the roller S is fed from one surface side of the sheet S fed from the sheet feeding unit 31. At the same time, the roller body 13a of the sheet feeding / separating roller 13 provided in the separation unit 14 is rotated from the other surface side of the sheet S by a driven rotation, so that a rotation resistance force in a direction opposite to the conveying force is given. Alternatively, by stopping the rotation, a sliding resistance force in a direction opposite to the conveying force is applied. In this manner, the separation unit 14 including the paper feed roller 12 and the paper feed separation roller 13 conveys the sheet S to the first conveyance roller pair 15 and the second conveyance roller pairs 16 and 17. Further, after the sheet S reaches the first pair of conveying rollers 15 and the pair of second conveying rollers 16 and 17, the roller body 12 a of the sheet feeding roller 12 loses the conveying force applied to the sheet S, and the first conveying roller The rotation is driven by the sheet S conveyed by the pair 15 and the second conveying roller pairs 16 and 17. That is, the sheet feed roller 12 and the sheet feed separation roller 13 of the separation unit 14 face the sheet S that has reached the first conveyance roller pair 15 and the second conveyance roller pair 16 and 17 in a direction opposite to the conveyance force. Gives the transport resistance.
[0077]
The first transport drive roller 15a and the second transport drive rollers 16a, 17a have roller bodies 20a, 21a, 22a, respectively, and the outer diameter D1 of the roller body 20a of the first transport drive roller 15a is the second transport drive roller. The outer diameters D2 of the roller bodies 21a and 22a of 16a and 17a are selected to be larger (D1> D2). Further, the first transport drive roller 15a and the second transport drive rollers 16a and 17a have a transport roller shaft 23a that is the same rotation axis.
[0078]
The roller body 20a of the first transport drive roller 15a and the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a are rotated at the same angular velocity by the transport roller shaft. As a result, the peripheral speed of the outer peripheral surface of the roller main body 20a of the first transport driving roller 15a becomes higher than the peripheral speed of the outer peripheral surfaces of the roller main bodies 21a and 22a of the second transport driving rollers 16a and 17a.
[0079]
Accordingly, the peripheral speed of the outer peripheral surface of the roller main body 20a of the first transport driving roller 15a is higher than the peripheral speed of the outer peripheral surface of the roller main bodies 21a and 22a of the second transport driving rollers 16a and 17a. The conveying force of the roller body 20a of the roller 15a becomes larger than the conveying force of the roller bodies 21a and 22a of the second conveyance driving rollers 16a and 17a. That is, the first transport roller pair 15 applies a greater transport force to the sheet S than the second transport roller pairs 16 and 17 with respect to the sheet S transported from the separation unit 14, and transports the sheet S to the registration unit 34.
[0080]
In the sheet conveying apparatus 11 including the separating unit 14, the first conveying roller pair 15, and the second conveying roller pairs 16, 17, the sheet S conveyed from the separating unit 14 is separated by the first conveying roller pair 15 and the second conveying roller pair 15. The sheet S contacts the first pair of conveying rollers 15, the second pair of conveying rollers 16 and 17, and the separating unit 14 until the sheet S reaches the pair of conveying rollers 16 and 17 and separates from the separating unit 14. It will be in contact. At this time, the sheet S receives a conveying force from the first conveying roller pair 15 and the second conveying roller pairs 16 and 17 and, at the same time, receives a conveying resistance force from the separating unit 14 in a direction opposite to the conveying force. Since the conveyance force applied to the sheet S by the first conveyance roller pair 15 is larger than the conveyance force applied to the sheet S by the second conveyance roller pair 16 and 17, the conveyance resistance causes the conveyance direction to vary in the width direction perpendicular to the conveyance path. It is possible to prevent the sheet S portion where the first transport roller pair 15 is located from being transported later in the width direction perpendicular to the transport path than the sheet S portion where the second transport roller pair 16 and 17 is located. .
[0081]
Therefore, it is possible to prevent the sheet S from being bent, which is a cause of wrinkling, and to convey the sheet S without wrinkling.
[0082]
In the above-described embodiment, a photo sensor including the contact type actuator 44a is used as the sheet detector 44, but a lead sensor including the contact type actuator 44a or a non-contact type photo sensor may be used. .
[0083]
Further, although the printing paper made of paper is used as the sheet S, a plastic sheet such as an overhead projector (Overhead Projector: OHP) sheet may be used.
[0084]
Further, although the sheet feed separation roller 13 is used as a support of the separation unit 14, a pad type may be used instead of a roller type.
[0085]
In another embodiment of the present invention, the outer diameter D1 of the roller body 20a of the first transport drive roller 15a and the roller body 21a of the second transport drive rollers 16a, 17a in the embodiment of FIGS. , 22a equal to the outer diameter D2 (D1 = D2), and the friction coefficient of the outer peripheral surface of the roller main body 20a of the first transport driving roller 15a is reduced to the outer peripheral surface of the roller main bodies 21a, 22a of the second transport driving rollers 16a, 17a. Larger than the coefficient of friction. Other configurations are the same as those of the above-described embodiment.
[0086]
According to such a configuration, the friction coefficient of the outer peripheral surface of the roller main body 20a of the first transport driving roller 15a is larger than the friction coefficient of the outer peripheral surface of the roller main bodies 21a and 22a of the second transport driving rollers 16a and 17a. The frictional force applied to the sheet by the outer peripheral surface of the roller main body 20a of the first transport drive roller 15a is larger than the frictional force applied to the sheet by the outer peripheral surfaces of the roller main bodies 21a and 22a of the second transport rollers 16a and 17a. Therefore, the idle rotation of the first transport roller pair 15 with respect to the sheet to be transported is prevented more than the idle rotation of the second transport roller pairs 16 and 17, so that the transport force of the first transport roller pair 15 is reduced. , 17.
[0087]
In still another embodiment of the present invention, the outer diameter D1 of the roller body 20a of the first transport drive roller 15a and the roller body of the second transport drive rollers 16a and 17a in the above-described embodiment of FIGS. The outer diameters D2 of the first transport drive rollers 15a are made equal to the outer diameter D2 of the first transport drive rollers 15a, and the hardness of the roller bodies 20a of the second transport drive rollers 16a, 17a is made lower than the hardness of the roller bodies 21a, 22a of the second transport drive rollers 16a, 17a. . Other configurations are the same as those of the above-described embodiments.
[0088]
According to such a configuration, the hardness of the roller body 20a of the first transport drive roller 15a is lower than the hardness of the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a. The contact area of the main body 20a with the sheet is larger than the contact area of the second transport drive rollers 16a and 17a with the sheet. Therefore, the idle rotation of the first transport roller pair 15 with respect to the sheet to be transported is prevented more than the idle rotation of the second transport roller pairs 16 and 17, so that the transport force of the first transport roller pair 15 is reduced. , 17.
[0089]
In still another embodiment of the present invention, the outer diameter D1 of the roller body 20a of the first transport driving roller 15a is changed to the roller body of the second transport driving rollers 16a and 17a in the embodiment of FIGS. The outer diameter of the first transport drive roller 15a is larger than the outer diameter D2 of the first transport drive roller 15a (D1> D2), and the friction coefficient of the outer peripheral surface of the roller body 20a of the first transport drive roller 15a is reduced. Be larger than the friction coefficient of the surface. Other configurations are the same as those of the above-described embodiments.
[0090]
According to such a configuration, the transport force of the first transport roller pair 15 can be more reliably increased than the transport force of the second transport roller pairs 16 and 17.
[0091]
In still another embodiment of the present invention, the outer diameter D1 of the roller body 20a of the first transport driving roller 15a is changed to the roller body of the second transport driving rollers 16a and 17a in the embodiment of FIGS. The outer diameter D2 of the first transport drive roller 15a is made larger than the outer diameter D2 of the first transport drive roller 15a (D1> D2), and the hardness of the roller body 20a of the second transport drive roller 16a, 17a is made lower. . Other configurations are the same as those of the above-described embodiments.
[0092]
According to such a configuration, the transport force of the first transport roller pair 15 can be more reliably increased than the transport force of the second transport roller pairs 16 and 17.
[0093]
In still another embodiment of the present invention, the outer diameter D1 of the roller body 20a of the first transport drive roller 15a and the roller body of the second transport drive rollers 16a and 17a in the above-described embodiment of FIGS. The outer diameters D2 of the first transport drive rollers 15a are made equal (D1 = D2), and the friction coefficient of the outer peripheral surface of the roller body 20a of the first transport drive roller 15a is reduced to the outer circumference of the roller bodies 21a, 22a of the second transport drive rollers 16a, 17a. The hardness of the roller body 20a of the first transport drive roller 15a is made lower than the hardness of the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a, while the friction coefficient is made larger than the surface friction coefficient. Other configurations are the same as those of the above-described embodiments.
[0094]
According to such a configuration, the transport force of the first transport roller pair 15 can be more reliably increased than the transport force of the second transport roller pairs 16 and 17.
[0095]
In still another embodiment of the present invention, the outer diameter D1 of the roller body 20a of the first transport driving roller 15a is changed to the roller body of the second transport driving rollers 16a and 17a in the embodiment of FIGS. The outer diameter of the first transport drive roller 15a is larger than the outer diameter D2 of the first transport drive roller 15a (D1> D2), and the friction coefficient of the outer peripheral surface of the roller body 20a of the first transport drive roller 15a is reduced. The hardness of the roller body 20a of the first transport drive roller 15a is set lower than the hardness of the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a. Other configurations are the same as those of the above-described embodiments.
[0096]
According to such a configuration, the transport force of the first transport roller pair 15 can be more reliably increased than the transport force of the second transport roller pairs 16 and 17.
[0097]
In still another embodiment of the present invention, the outer diameter D1 of the roller body 20a of the first transport drive roller 15a and the roller body of the second transport drive rollers 16a and 17a in the above-described embodiment of FIGS. The outer diameter D2 of the first transport driven roller 15b is set equal to the outer diameter D2 of the first transport driven roller 15b (D1 = D2), and the outer diameter d1 of the roller main bodies 25a and 26a of the second transport driven rollers 16b and 17b is set. It is larger (d1> d2). Other configurations are the same as those of the above-described embodiments.
[0098]
According to such a configuration, the outer diameter d1 of the roller body 24a of the first transport driven roller 15b is larger than the outer diameter d2 of the roller bodies 25a and 26a of the second transport driven rollers 16b and 17b (d1> d2). The pinching force between the roller body 20a of the first transport drive roller 15a and the roller body 24a of the first transport driven roller 15b is increased by the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a and the second transport driven roller 16b. 17b is larger than the pinching force between the roller bodies 25a and 26a. Therefore, the idle rotation of the first transport roller pair 15 with respect to the sheet to be transported is prevented more than the idle rotation of the second transport roller pairs 16 and 17, so that the transport force of the first transport roller pair 15 is reduced. , 17.
[0099]
In still another embodiment of the present invention, the outer diameter D1 of the roller body 20a of the first transport drive roller 15a and the roller body of the second transport drive rollers 16a and 17a in the above-described embodiment of FIGS. The outer diameter D2 of the first conveying driven roller 15b is made equal to the outer diameter D2 of the first conveying driven roller 15b (D1 = D2), and the roller shaft 24b of the first conveying driven roller 15b is closer to the conveying roller shaft 23 than the roller shafts 25b and 26b of the second conveying driven rollers 16b and 17b. To place. Other configurations are the same as those of the above-described embodiments.
[0100]
According to such a configuration, the roller shaft 24b of the first transport driven roller 15b is disposed closer to the transport roller shaft 23 than the roller shafts 25b and 26b of the second transport driven rollers 16b and 17b, so that the The force by which the roller body 20a of the first transport driving roller 15a presses the roller body 24a of the first transport driven roller 15b is changed by the roller bodies 25a and 26a of the second transport driven rollers 16a and 17a being the rollers of the second transport driven rollers 16b and 17b. The force is greater than the force pressing the main body 24a. As a result, the pinching force between the roller body 20a of the first transport drive roller 15a and the roller body 24a of the first transport driven roller 15b is increased by the roller bodies 21a and 22a of the second transport drive rollers 16a and 17a and the second transport driven roller. The pinching force of the roller bodies 16b and 17b with the roller bodies 25a and 26a is larger. Therefore, the idle rotation of the first transport roller pair 15 with respect to the sheet to be transported is prevented more than the idle rotation of the second transport roller pairs 16 and 17, so that the transport force of the first transport roller pair 15 is reduced. , 17.
[0101]
In still another embodiment of the present invention, in each of the above-described embodiments, the first transport drive roller 15a and the second transport drive rollers 16a and 17a are divided into three roller bodies 20a and 21a22a. However, it may be constituted by one roller body which is not divided and is long in the axial direction, or may be constituted by being divided into three or more.
[0102]
In still another embodiment of the present invention, in each of the above-described embodiments, the material of each of the roller bodies 12a, 13a, 20a, 21a, 22a, 24a, 25a, 26a is ethylene propylene diene copolymer rubber (Ethylene Propylene). Diene
Although Monomer (abbreviation: EPDM) was used, chloroprene rubber (abbreviation: CR) or urethane rubber (Urethane: abbreviation U) or the like may be used.
[0103]
FIG. 6 is a simplified cross-sectional view showing an image forming apparatus 100 according to still another embodiment of the present invention. The image forming apparatus 100 is a digital multifunction peripheral having functions as a copier, a printer, and a facsimile machine, and includes a scanner unit 101, a laser recording unit 150, and a post-processing unit 200. Further, the image forming apparatus 100 includes the sheet conveying device 11 and the registration unit 34 of the embodiment shown in FIGS.
[0104]
The scanner unit 101 reads a document image, and includes a document table 102 made of transparent glass, a double-sided automatic document feeder 103, and a document reading unit 104.
[0105]
A double-sided automatic document feeder (Reversing Automatic Document Feeder; abbreviated as RADF) 103 conveys a document set on a predetermined document tray to a document mounting table 102 made of transparent glass one by one, and reads the document after reading. It has a function to carry out a document to a discharge tray. The double-sided automatic document feeder 103 can also turn over the read document and transport it to the document table 102 again. As a result, the scanner unit 101 can read images on both sides of a document.
[0106]
A document reading unit (Scanner Unit; abbreviated as SU) 104 is disposed below the document table 102 and reads a document image on the document table 102 line by line. The document reading unit 104 includes a first scanning unit 105, a second scanning unit 106, an optical lens 107, and a photoelectric conversion element (Charge Coupled Device; abbreviated as CCD) line sensor 108. Hereinafter, the "photoelectric conversion element line sensor 108" is referred to as the CCD line sensor 108.
[0107]
The first scanning unit 105 has a light source 109 and a first reflecting mirror 110 for guiding the reflected light of the document to the second scanning unit 106. The first scanning unit 105 moves along the document table 102 from the left to the right in FIG. Expose the original while moving with.
[0108]
The second scanning unit 106 includes a second reflecting mirror 111 and a third reflecting mirror 112 that guide light from the first reflecting mirror 110 of the first scanning unit 105 to the optical lens 107 and the CCD line sensor 108. It moves at a speed of V / 2 following the scanning unit 105.
[0109]
The optical lens 107 forms an image of the reflected light from the second scanning unit 106 on the CCD line sensor 108. The CCD line sensor 108 converts light from the optical lens 107 into an analog electric signal. This electric signal is converted into digital image data by an image processing unit (not shown) and stored in a memory (not shown). The image data is output to a laser recording unit 150 described below in response to an output command from the image processing unit.
[0110]
The document reading unit 104 reads an image of a document automatically conveyed by the duplex automatic document feeder 103 in a state where the first scanning unit 105 and the second scanning unit 106 are fixed at predetermined exposure positions. You can also.
[0111]
The laser recording unit 150 forms an image on a sheet based on image data output from the scanner unit 101 and the outside.
(Laser Scanning Unit; abbreviated LSU) 151, an electrophotographic processing unit 152, a sheet conveying device 11, and a registration unit 34.
[0112]
The laser writing unit 151 irradiates a photosensitive drum 153, which will be described later, with a laser beam to form an electrostatic latent image based on image data obtained from the scanner unit 101 and the outside. A polygon mirror that deflects the obtained laser light at an equal angular velocity, and an f-θ lens that corrects the laser light deflected at an equal angular velocity on the photoconductor drum 153 so that it is deflected at an equal angular velocity.
The electrophotographic process unit 152 has a photosensitive drum 153, develops an electrostatic latent image on the photosensitive drum 153 to form a toner image, and transfers the toner image to a sheet. The electrophotographic process unit 152 includes a charger 154, a developing device 155, a transfer device 156, a cleaning device 157, and a static eliminator 158 provided around the photoconductor drum 153.
[0113]
The charger 154 charges the photosensitive drum 153 to a predetermined potential. The developing device 155 develops the electrostatic latent image on the photosensitive drum 153 with toner to form a toner image. The transfer unit 156 transfers the toner image on the photosensitive drum 153 to a sheet. The cleaning device 157 removes toner and the like remaining after the transfer from the photosensitive drum 153.
[0114]
The sheet conveying device 11 conveys the sheet to the registration unit 34 that conveys the sheet to the electrophotographic process unit 152, fixes the image transferred to the sheet, and discharges the sheet to the outside. 5 has the pickup unit 33, the separating unit 14, the first pair of conveying rollers 15, and the pair of second conveying rollers 16 and 17 in the embodiment of FIG. In addition, the sheet conveying device 11 has a sheet feeding cassette 159, a manual sheet feeding device 160, a fixing device 161, a re-supply path 162, a discharge roller 163, and a duplex copying unit 164 in addition to the above components.
[0115]
The paper feed cassette 159 is provided below the image forming apparatus 100, stores sheets, and feeds the sheets to the pickup unit 33. The manual sheet feeding device 160 is a device that manually feeds a sheet to the pickup unit 33. The fixing device 161 fixes the toner image transferred to the sheet by heating and pressing the sheet. The re-supply path 162 is used not only for transferring the toner image to one surface of the sheet, but also for transferring the toner image to the other surface of the sheet on which the toner image has been transferred. This is a path for feeding the sheet to a duplex copying unit 164 described later by turning over the sheet so that an image is formed. The two-sided copying unit 164 has a two-sided copying tray, temporarily stores the sheet on which the toner image is fixed, and sends the sheet to the pickup unit 33 to form a toner image on the other surface of the sheet on which the toner image is formed. It is for re-feeding the sheet. Note that the double-sided copying unit 164 can be replaced with the sheet feeding cassette 159. The discharge roller 163 is a pair of conveying rollers that supplies the sheet discharged from the fixing device 161 to the post-processing device 200 or the re-supply path 162 described later.
[0116]
The post-processing device 200 has a fixed tray 201 and a lifting tray 202, and performs post-processing such as stapling on a sheet that has passed through the discharge roller 162, and selectively places a sheet on the fixed tray 201 or the lifting tray 202. Is to be discharged.
[0117]
According to the image forming apparatus 100 including the sheet conveying device 11 and the registration unit 34 according to the embodiment of FIGS. 1 to 5 described above, the separating unit 14, the first conveying roller pair 15, and the second conveying roller pair Since the sheet 16 is provided, the sheet can be conveyed to the electrophotographic processing unit 152 without wrinkles. Therefore, a good printed matter without wrinkles can be obtained.
[0118]
In still another embodiment of the present invention, the sheet conveying device 11 of the embodiment of FIGS. 1 to 5 and the sheet conveying device 11 of the image forming apparatus 100 including the registration unit 34 are replaced with the above-described embodiment. And any one of the other types of sheet conveying devices.
[0119]
In the above embodiment, the laser writing unit (Laser Scanning Unit; abbreviated LSU) 151 is used. However, a light emitting element array such as a light emitting diode (Light Emitting Diode; abbreviated LED) and an electroluminescent (Electroluminescent); The used solid scanning type optical writing head unit may be used.
[0120]
In still another embodiment of the present invention, in the sheet conveying apparatus of each of the above-described embodiments, the sheet conveying apparatus may be configured to include the registration unit 34.
[0121]
【The invention's effect】
According to the present invention, the sheet conveyed from the separation unit reaches the first conveyance roller unit and the second conveyance roller unit, and the sheet is separated from the first conveyance roller unit until the sheet is separated from the separation unit. , Comes into contact with the second transport roller unit and the separation unit. At this time, the sheet receives the conveying force from the first conveying roller portion and the second conveying roller portion, and at the same time, the sheet feeding roller loses the conveying force, so that the conveying resistance from the separating portion is opposite to the conveying force. However, since the conveying force applied to the sheet by the first conveying roller unit is greater than the conveying force applied to the sheet by the second conveying roller unit, the first conveying roller unit generates the first conveying roller in the width direction perpendicular to the conveying path by the conveying resistance force. The sheet portion where the roller portion is located can be prevented from being transported later in the width direction perpendicular to the transport path than the sheet portion where the second transport roller portion is located.
[0122]
Therefore, it is possible to prevent the sheet from being bent, which is a cause of wrinkling, and to convey the sheet without wrinkling.
[0123]
According to the present invention, the peripheral speed of at least the outer peripheral surface of the driven roller of the first transport roller portion is higher than the peripheral speed of at least the outer peripheral surface of the driven roller of the second transport roller portion. The conveying force of the first conveying roller unit can be made larger than the conveying force of the second conveying roller unit.
[0124]
Further, according to the present invention, the first transport roller unit and the second transport roller unit rotate at the same angular velocity, and the outer diameter of at least the driven roller of the first transport roller unit is the second transport roller unit. Since it is at least larger than the outer diameter of the driven roller, the peripheral speed of the outer peripheral surface of the driven roller of the first transport roller unit is reduced by the peripheral speed of the outer peripheral surface of the driven roller of the second transport roller unit. Can be larger.
[0125]
Further, according to the present invention, the friction coefficient of at least the outer peripheral surface of the driven roller of the first transport roller portion is larger than the friction coefficient of at least the outer peripheral surface of the driven roller of the second transport roller portion. The frictional force applied to the sheet by the outer peripheral surface of the driven roller of the first transport roller unit is greater than the frictional force applied to the sheet by the outer peripheral surface of the driven roller of the second transport roller unit. Therefore, the idle rotation of the driven roller of the first transport roller unit is prevented more than the idle rotation of the driven roller of the second transport roller unit with respect to the sheet to be transported, so that the transport force of the first transport roller unit is reduced. It can be made larger than the conveying force of the second conveying roller section.
[0126]
Further, according to the present invention, the hardness of at least the driven roller of the first transport roller unit is lower than the hardness of at least the driven roller of the second transport roller unit. The contact area of the second roller with respect to the sheet is larger than the contact area of the second roller with the driven roller. Therefore, the idle rotation of the driven roller of the first transport roller unit is prevented more than the idle rotation of the driven roller of the second transport roller unit with respect to the sheet to be transported, so that the transport force of the first transport roller unit is reduced. It can be made larger than the conveying force of the second conveying roller section.
[0127]
Further, according to the present invention, since the sheet conveying apparatus having the separating section, the first conveying roller section and the second conveying roller section is provided, the sheet can be conveyed to the printing section without wrinkling. it can. Therefore, a good printed matter without wrinkles can be obtained.
[Brief description of the drawings]
FIG. 1 is a simplified perspective view showing a sheet conveying apparatus 11 according to an embodiment of the present invention.
FIG. 2 is a simplified cross-sectional view illustrating a sheet conveying device 11 and a registration unit 34.
FIG. 3 is a block diagram illustrating an electrical and mechanical configuration of a sheet conveying device 11 and a registration unit 34.
FIG. 4 is a flowchart for explaining operations of the sheet conveying device 11 and a registration unit 34;
FIG. 5 is a time chart for explaining operations of the sheet conveying device 11 and the registration unit 34.
FIG. 6 is a simplified cross-sectional view illustrating an image forming apparatus 100 according to still another embodiment of the invention.
FIG. 7 is a simplified plan view showing a conventional sheet conveying apparatus 1.
[Explanation of symbols]
11 Sheet conveying device
12 Paper feed roller
12a Roller body of paper feed roller 12
12b Roller shaft of paper feed roller 12
13 Paper feed separation roller
13a Roller body of paper feed separation roller 13
13b Roller shaft of paper separation roller 13
14 Separation unit
15 First transport roller pair
15a First transport drive roller
15b First transport driven roller
16, 17 Second transport roller pair
16a, 17a Second transport drive roller
16b, 17b Second transport driven roller
18 Paper feed roller clutch
19 Torque limiter
20a Roller body of first transport drive roller 15a
20b Roller shaft of first transport drive roller 15a
21a, 22a Roller body of second transport drive rollers 16a, 17a
21b, 22b Roller shafts of second transport drive rollers 16a, 17a
23 Transport roller shaft
23a Transport roller clutch
24a Roller body of first transport driven roller 15b
24b Roller shaft of first transport driven roller 15b
25a, 26a Roller body of second transport driven rollers 16b, 17b
25b, 26b Roller shafts of second transport driven rollers 16b, 17b
31 Paper feed unit
100 Image forming apparatus

Claims (6)

A sheet feeding roller for applying a conveying force to the sheet fed from the sheet feeding unit from one surface side, and supporting the sheet from the other surface side, and when the conveying resistance is increased, sliding in a direction opposite to the conveying force. A separation unit having a support that provides dynamic resistance;
A first transport roller unit that is provided downstream of the paper feed roller in the transport direction, has a first transport roller pair that vertically forms a pair with respect to a transport path through which the sheet passes, and has at least one roller driven; When,
A second transport roller pair, which is provided on both sides in the width direction perpendicular to the transport path with respect to the first transport roller unit, forms a pair vertically with respect to the transport path, and has at least one roller driven by a second transport roller pair; And a transport roller section,
The separation unit loses the conveyance force to the sheet when or after the sheet reaches the first conveyance roller unit and the second conveyance roller unit,
The sheet conveyance device according to claim 1, wherein the first conveyance roller has a conveyance force larger than a conveyance force to the sheet by the second conveyance roller. By making the peripheral speed of at least the outer peripheral surface of the driven roller of the first transport roller unit greater than the peripheral speed of at least the outer peripheral surface of the driven roller of the second transport roller unit, The sheet conveying device according to claim 1, wherein the conveying force of the conveying roller unit is larger than the conveying force of the second conveying roller unit. The first transport roller section and the second transport roller section rotate at the same angular velocity, and the outer diameter of at least the driven roller of the first transport roller section is at least the outer diameter of the second transport roller section. 3. The sheet conveying apparatus according to claim 2, wherein the conveying force of the first conveying roller unit is made larger than the conveying force of the second conveying roller unit by making the outer diameter of the driven roller larger. The first transport roller unit is configured to have a friction coefficient at least on an outer peripheral surface of the driven roller larger than at least an outer peripheral surface of the driven roller of the second transport roller unit. The sheet conveying device according to claim 1, wherein the conveying force of the conveying roller unit is larger than the conveying force of the second conveying roller unit. By setting the hardness of at least the driven roller of the first transport roller unit to be lower than the hardness of at least the driven roller of the second transport roller unit, the transport force of the first transport roller unit is reduced to the second. 2. The sheet conveying apparatus according to claim 1, wherein the conveying force is set to be larger than the conveying force of the two conveying rollers. An image forming apparatus comprising the sheet conveying device according to claim 1.

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