JP7311833B2 - Secondary transfer device - Google Patents
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- JP7311833B2 JP7311833B2 JP2019087308A JP2019087308A JP7311833B2 JP 7311833 B2 JP7311833 B2 JP 7311833B2 JP 2019087308 A JP2019087308 A JP 2019087308A JP 2019087308 A JP2019087308 A JP 2019087308A JP 7311833 B2 JP7311833 B2 JP 7311833B2
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Description
本発明は、中間転写ベルト上に一次転写されたトナー像を用紙に二次転写する二次転写装置に係り、特に、用紙の先後端が二次転写位置を通る際の衝撃を緩和することのできる二次転写装置に関する。 The present invention relates to a secondary transfer device that secondarily transfers a toner image that has been primarily transferred onto an intermediate transfer belt onto a sheet of paper, and in particular, it is capable of alleviating the impact when the leading and trailing edges of the sheet of paper pass through the secondary transfer position. It relates to a secondary transfer device capable of
多くの電子写真方式の画像形成装置では、複数のローラに巻き掛けられて周回する無端環状で所定幅の中間転写ベルトの外周面に沿って、それぞれ一の色成分のトナー像を形成するイエロ（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（Ｋ）、等の色別の像形成ユニットを配列する構成が採られる。そして、これらの像形成ユニットによって各色のトナー像を中間転写ベルト上に順次重ね合わせることでフルカラーのカラートナー像を中間転写ベルト上に形成し、これを用紙に二次転写するようになっている。 In many electrophotographic image forming apparatuses, yellow (yellow) toner images of one color component are formed along the outer peripheral surface of an endless annular intermediate transfer belt having a predetermined width that is wound around a plurality of rollers. Y), magenta (M), cyan (C), black (K), and the like are arranged in image forming units for each color. These image forming units sequentially superimpose the toner images of each color on the intermediate transfer belt to form a full-color toner image on the intermediate transfer belt, which is then secondarily transferred onto paper. .
二次転写位置では、中間転写ベルトを、その内側から支持するローラと、外側からバネ等に付勢されて押圧する二次転写ローラとの間に挟み込んで転写ニップを形成する。搬送されてきた用紙が転写ニップ（中間転写ベルトの外周面と二次転写ローラとの間）を通る際に中間転写ベルト上のトナー像が用紙に転写される。 At the secondary transfer position, a transfer nip is formed by sandwiching the intermediate transfer belt between a roller that supports the intermediate transfer belt from the inside and a secondary transfer roller that presses the intermediate transfer belt from the outside by being biased by a spring or the like. The toner image on the intermediate transfer belt is transferred to the paper when the conveyed paper passes through a transfer nip (between the outer peripheral surface of the intermediate transfer belt and the secondary transfer roller).
転写ニップに厚紙の先端が進入するときや後端が抜け出るときには負荷が大きく変化するので、中間転写ベルトの周回速度が変動したり振動が発生したりして、画像にスジやムラが生じる場合がある。 When the leading edge of the cardboard enters the transfer nip or the trailing edge of the cardboard leaves the transfer nip, the load changes significantly, so the rotation speed of the intermediate transfer belt fluctuates or vibration occurs, which may cause streaks or unevenness in the image. be.
この問題に対応するために、用紙の先端および後端が転写ニップを通る際にニップ圧を一時的に減圧することが行われる。たとえば、下記特許文献１に開示の装置では、中間転写ベルトを挟んで二次転写ローラと対向配置されたローラの軸の同軸上にカムを設け、該カムの凸部を、二次転写ローラの軸に設けた当接体に当接させることで、二次転写ローラとこれに対向するローラとの軸間距離を広げてニップ圧を一時的に減圧している。 To address this problem, the nip pressure is temporarily reduced as the leading and trailing edges of the paper pass through the transfer nip. For example, in the apparatus disclosed in Patent Document 1 below, a cam is provided coaxially with the shaft of a roller opposed to the secondary transfer roller with an intermediate transfer belt interposed therebetween, and the convex portion of the cam is aligned with the secondary transfer roller. By contacting the contact member provided on the shaft, the distance between the shafts of the secondary transfer roller and the roller facing thereto is widened to temporarily reduce the nip pressure.
また、下記特許文献２に開示された装置では、モータの駆動力を伝達機構で二次転写ローラに伝えて、二次転写ローラを中間転写ベルトに向けて押圧すると共に、このモータのトルクを制御することで、一時的な減圧を行っている。この装置の伝達機構は、略水平方向に長い第１レバーおよび第２レバーで構成され、第１レバーは一端が軸支され（支点）、中ほどで二次転写ローラを軸支し（作用点）、他端は第２レバーの先端に設けられたスライド穴（第２レバーの作用点）に軸支されている。第２レバーは中ほどよりやや先端寄りの位置が支点となって軸支され、他端はモータからの力を受ける力点となっている。 Further, in the apparatus disclosed in Patent Document 2 below, the driving force of the motor is transmitted to the secondary transfer roller by a transmission mechanism to press the secondary transfer roller toward the intermediate transfer belt, and the torque of this motor is controlled. By doing so, temporary decompression is performed. The transmission mechanism of this device is composed of a first lever and a second lever that are elongated in a substantially horizontal direction. ), and the other end is pivotally supported in a slide hole (action point of the second lever) provided at the tip of the second lever. The second lever is pivotally supported at a position a little closer to the tip than the middle, and the other end serves as a power point for receiving force from the motor.
具体的には、第２レバーの他端は扇状に広がっており、ここにモータの軸に設けられたギアと噛み合う歯列が円弧状に列設されている。第１レバーと第２レバーはリンク機構となっており、モータの軸の回転角度に応じて第２レバーが揺動すると二次転写ローラが上下に変位するようになっている。モータを駆動して二次転写ローラを中間転写ベルトに押圧させて転写ニップを形成する。二次転写ローラが中間転写ベルトから押し戻される力とモータのトルクとが釣り合った状態で二次転写ローラは静止し、用紙の先後端が転写ニップを通るときにモータのトルクを一時的に弱めることでニップ圧を減圧するようになっている。 Specifically, the other end of the second lever spreads in a fan shape, and a row of teeth meshing with a gear provided on the shaft of the motor is arranged in an arc shape. The first lever and the second lever form a link mechanism, and when the second lever swings according to the rotation angle of the shaft of the motor, the secondary transfer roller is vertically displaced. A motor is driven to press the secondary transfer roller against the intermediate transfer belt to form a transfer nip. The secondary transfer roller stands still in a state in which the force pushing the secondary transfer roller back from the intermediate transfer belt and the torque of the motor are balanced, and the torque of the motor is temporarily weakened when the leading and trailing edges of the paper pass through the transfer nip. to reduce the nip pressure.
特許文献１に開示の装置では、中間転写ベルトを挟んで二次転写ローラと対向するローラの軸の同軸上にカムやその駆動部を設けるので、二次転写ローラの軸長方向に装置構成が大きくなってしまう。 In the device disclosed in Japanese Patent Application Laid-Open No. 2002-200010, since the cam and its driving section are provided coaxially with the shaft of the roller facing the secondary transfer roller with the intermediate transfer belt interposed therebetween, the device configuration is arranged in the axial direction of the secondary transfer roller. It gets bigger.
また、特許文献２に開示の装置では、圧着機構（第１レバー）の支点と作用点（二次転写ローラの位置）の外側に、減圧機構(第２レバー)の作用点が配置されており、二次転写ローラの軸に垂直な断面における装置面積が大きくなってしまう。 Further, in the device disclosed in Patent Document 2, the point of action of the decompression mechanism (second lever) is arranged outside the fulcrum and point of action (position of the secondary transfer roller) of the pressing mechanism (first lever). , the device area in the cross section perpendicular to the axis of the secondary transfer roller becomes large.
本発明は、上記の問題を解決しようとするものであり、用紙の先後端が転写ニップを通る際のニップ圧を一時的に減圧する機能を備えつつ小型化を図ることのできる二次転写装置を提供することを目的としている。 SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and is a secondary transfer device capable of miniaturization while having a function of temporarily reducing the nip pressure when the leading and trailing edges of a sheet of paper pass through a transfer nip. is intended to provide
かかる目的を達成するための本発明の要旨とするところは、次の各項の発明に存する。 The gist of the present invention for achieving this object lies in the following inventions.
［１］複数のローラに巻き掛けられて周回する無端環状で所定幅の中間転写ベルトの外周面に一次転写されたトナー像を所定の二次転写位置で用紙に二次転写する二次転写装置であって、
前記二次転写位置で前記中間転写ベルトをその内周面に当接する対向ローラとの間に挟んで押圧する押圧位置と、前記中間転写ベルトの外周面から離隔された離隔位置とに二次転写ローラを変位させる圧着解除機構と、
前記圧着解除機構を駆動する第１駆動部と、
前記押圧位置にされた前記二次転写ローラが前記中間転写ベルトを前記対向ローラとの間に挟んで押圧するニップ圧を、用紙の先端および後端が前記二次転写ローラと前記中間転写ベルトの間を通る際に一時的に減圧する高速減圧機構と、
前記高速減圧機構を駆動する第２駆動部と、
を有すると共に、
前記圧着解除機構および前記高速減圧機構を、前記二次転写ローラの軸方向に投影した場合の投影像が重なるように配置し、
前記圧着解除機構は、前記二次転写ローラの軸と同方向であって前記第１駆動部によって駆動される回転軸に支持された圧着カムと、前記圧着カムに当接して揺動することで前記二次転写ローラを前記押圧位置と前記離隔位置に変位させる圧着アームを有し、
前記高速減圧機構は、前記二次転写ローラの軸と同方向であって前記第２駆動部によって駆動される回転軸に支持された減圧カムと、前記減圧カムに当接して揺動することで前記押圧位置にある前記二次転写ローラの軸を前記ニップ圧が弱まる方向へ変位させる減圧アームを有し、
前記圧着カムと前記減圧カムの前記投影像が重なり、
前記圧着カムの回転軸と、前記減圧カムの回転軸が同軸にされており、
前記圧着アームと前記圧着カムを、前記二次転写ローラの軸方向の両端に分かれた２箇所にそれぞれ設け、これらの内側に前記減圧カムを配置した
ことを特徴とする二次転写装置。
[1] A secondary transfer device that secondarily transfers a toner image that has been primarily transferred onto the outer peripheral surface of an endless annular intermediate transfer belt that is wound around a plurality of rollers and has a predetermined width onto a sheet of paper at a predetermined secondary transfer position. and
Secondary transfer to a pressing position where the intermediate transfer belt is sandwiched and pressed between an opposing roller that abuts on the inner peripheral surface of the intermediate transfer belt at the secondary transfer position, and a separation position that is separated from the outer peripheral surface of the intermediate transfer belt. a pressure release mechanism that displaces the roller;
a first drive unit that drives the pressure release mechanism;
The nip pressure at which the secondary transfer roller placed in the pressing position presses the intermediate transfer belt between itself and the opposing roller is applied to the leading edge and the trailing edge of the sheet by the pressure between the secondary transfer roller and the intermediate transfer belt. A high-speed decompression mechanism that temporarily decompresses when passing through,
a second drive unit that drives the high-speed decompression mechanism;
and
arranging the pressure release mechanism and the high-speed decompression mechanism so that projected images when projected in the axial direction of the secondary transfer roller overlap;
The pressure release mechanism includes a pressure cam supported by a rotation shaft driven by the first driving section in the same direction as the shaft of the secondary transfer roller, and swinging in contact with the pressure cam. a pressing arm that displaces the secondary transfer roller between the pressing position and the separating position;
The high-speed decompression mechanism includes a decompression cam supported by a rotating shaft driven by the second driving section in the same direction as the shaft of the secondary transfer roller, and swinging in contact with the decompression cam. a decompression arm that displaces the shaft of the secondary transfer roller at the pressing position in a direction in which the nip pressure is weakened;
the projection images of the pressure cam and the decompression cam overlap,
the rotary shaft of the pressure cam and the rotary shaft of the decompression cam are coaxial,
A secondary transfer device according to claim 1, wherein the pressing arm and the pressing cam are provided at two locations separated from each other in the axial direction of the secondary transfer roller, and the decompression cam is disposed inside them.
上記発明では、圧着解除機構と高速減圧機構を、二次転写ローラの軸方向に投影した場合の投影像が重なるように配置することで、二次転写ローラの軸に垂直な断面において二次転写装置の占める面積を小さくすることができる。 In the above invention, the pressure release mechanism and the high-speed decompression mechanism are arranged so that the projected images when projected in the axial direction of the secondary transfer roller overlap each other. The area occupied by the device can be reduced.
上記発明では、構成部品の中で比較的サイズの大きい圧着カムと減圧カムをそれらの投影像が重なるように配置することで、二次転写ローラの軸に垂直な断面における二次転写装置の面積を小さくする。また上記発明では、圧着カムの外側に減圧カムを配置する場合に比べて、二次転写ローラの軸方向における二次転写装置のサイズが小型化される。 In the above invention, by arranging the compression cam and the decompression cam, which are relatively large in size among the components, so that their projection images overlap, the area of the secondary transfer device in the cross section perpendicular to the axis of the secondary transfer roller is reduced. to be smaller. Also, in the above invention, the size of the secondary transfer device in the axial direction of the secondary transfer roller is reduced compared to the case where the decompression cam is arranged outside the pressure cam.
上記発明では、圧着カムの回転軸と減圧カムの回転軸を同軸とすることでカム同士の重なりを最大化すると共に、カムの制御における位置精度を高めることができる。 In the above invention, the rotation axis of the compression cam and the rotation axis of the decompression cam are coaxial, thereby maximizing the overlap between the cams and increasing the positional accuracy in controlling the cams.
［２］前記圧着カムの最大径が、前記減圧カムの最小径より小さい
ことを特徴とする［１］に記載の二次転写装置。
[ 2 ] The secondary transfer device according to [ 1 ], wherein the maximum diameter of the pressure cam is smaller than the minimum diameter of the decompression cam.
上記発明では、圧着カムの位置に係らず、減圧カムによる減圧動作を行うことができる。 In the above invention, the pressure reducing operation can be performed by the pressure reducing cam regardless of the position of the pressure cam.
［３］前記圧着カムの最小径が、前記減圧カムの最大径より大きい
ことを特徴とする［１］に記載の二次転写装置。
[ 3 ] The secondary transfer device according to [ 1 ], wherein the minimum diameter of the pressure cam is larger than the maximum diameter of the decompression cam.
上記発明では、減圧カムの位置に係らず、圧着カムによる圧着動作を行うことができる。 In the above invention, it is possible to perform the crimping operation by the crimping cam regardless of the position of the decompression cam.
［４］前記二次転写ローラの軸方向の両端に分かれた２箇所に前記減圧アームを設けると共にこれらの減圧アームの力点となる箇所同士を連結部材で接続し、
前記減圧カムを、前記二次転写ローラの軸方向の中心部に配置し、
前記減圧カムに前記連結部材が当接して前記減圧アームが揺動する
ことを特徴とする［１］に記載の二次転写装置。
[ 4 ] The decompression arms are provided at two locations on both ends of the secondary transfer roller in the axial direction, and the decompression arms are connected to each other by connecting members,
disposing the decompression cam at the center in the axial direction of the secondary transfer roller;
The secondary transfer device according to [1], wherein the decompression arm swings when the connection member contacts the decompression cam.
上記発明では、両端の減圧アームを同期させて減圧動作を行うことができる。 In the above invention, the decompression arms at both ends can be synchronized to perform the decompression operation.
［５］前記二次転写ローラの軸方向の両端に分かれた２箇所に前記減圧アームを設けると共にこれらの減圧アームの力点となる箇所同士を連結部材で接続し、
前記圧着カムの内側近傍にそれぞれ前記減圧カムを配置し、
各減圧カムに前記連結部材が当接して前記減圧アームが揺動する
ことを特徴とする［１］に記載の二次転写装置。
[ 5 ] The decompression arms are provided at two locations on both ends of the secondary transfer roller in the axial direction, and the decompression arms are connected to each other by connecting members,
arranging the decompression cams in the vicinity of the inner sides of the crimping cams;
The secondary transfer device according to [1], wherein the decompression arm swings when the connection member abuts on each decompression cam.
上記発明では、連結部材の撓みの影響を低減することができる。 In the above invention, the influence of bending of the connecting member can be reduced.
［６］前記圧着カムの内側近傍にそれぞれ前記減圧カムを配置し、
該２つの前記減圧カムの内側に、前記第２駆動部および前記減圧カムの角度位置を検出する位置検出手段を配置した
ことを特徴とする［１］または［５］に記載の二次転写装置。
[ 6 ] Arranging the decompression cams near the inside of the compression cams,
The secondary transfer device according to [1] or [5], characterized in that position detection means for detecting the angular positions of the second driving section and the decompression cam is arranged inside the two decompression cams. .
上記発明では、二次転写ローラの軸方向における二次転写装置のサイズを小さくすることができる。 In the above invention, the size of the secondary transfer device in the axial direction of the secondary transfer roller can be reduced.
［７］前記減圧アームは、回転体で前記減圧カムに当接する
ことを特徴とする［１］に記載の二次転写装置。
[ 7 ] The secondary transfer device according to [1] , wherein the decompression arm is a rotating body that contacts the decompression cam.
上記発明では、摩擦が軽減されて、減圧カムの寿命を延ばすことができる。 In the above invention, friction is reduced and the life of the decompression cam can be extended.
［８］前記減圧アームが前記減圧カムからの力を受ける力点と、前記減圧アームが前記ニップ圧の弱まる方向への力を与える作用点との間に、前記減圧アームの回転支点がある
ことを特徴とする［１］に記載の二次転写装置。
[ 8 ] The rotation fulcrum of the decompression arm is between the force point where the decompression arm receives force from the decompression cam and the point of action where the decompression arm applies force in the direction of weakening the nip pressure. The secondary transfer device according to [1] .
上記発明では、減圧アームの力点に力を加える方向と、減圧アームの作用点が力を与える方向が逆方向なので、配置の自由度が高まる。 In the above invention, the direction in which force is applied to the force point of the decompression arm is opposite to the direction in which force is applied by the action point of the decompression arm, so the degree of freedom in arrangement is increased.
［９］前記減圧アームの前記力点から前記回転支点までの距離より、前記回転支点から前記作用点までの距離が長い
ことを特徴とする［８］に記載の二次転写装置。
[ 9 ] The secondary transfer device according to [ 8 ], wherein the distance from the rotation fulcrum to the action point is longer than the distance from the force point of the decompression arm to the rotation fulcrum.
［１０］前記第１駆動部と前記第２駆動部を、前記二次転写ローラの軸方向に投影した場合の投影像が重なるように配置した、
ことを特徴とする［１］に記載の二次転写装置。
[ 10 ] The first drive unit and the second drive unit are arranged so that the projected images when projected in the axial direction of the secondary transfer roller overlap,
The secondary transfer device according to [1], characterized by:
上記発明では、二次転写装置の二次転写ローラの軸方向における断面積の削減に繋がる。 In the above invention, the cross-sectional area in the axial direction of the secondary transfer roller of the secondary transfer device can be reduced.
［１１］前記圧着アームは、バネと前記減圧アームをこの順に介して前記二次転写ローラを前記押圧位置に向けて押し動かし、
前記高速減圧機構は、前記減圧アームで前記バネを前記圧着アーム側へ押し戻して前記減圧を行う
ことを特徴とする［１］に記載の二次転写装置。
[ 11 ] The pressing arm presses and moves the secondary transfer roller toward the pressing position via a spring and the decompression arm in this order;
The secondary transfer device according to [1] , wherein the high-speed decompression mechanism performs the decompression by pushing the spring back toward the pressure arm with the decompression arm.
上記発明では、圧着アームを押圧位置に維持したまま、減圧動作を行うことができるので、一時的な減圧動作を、減圧アームの少ないストロークで高速・円滑に行うことができる。 In the above invention, the decompression operation can be performed while the crimping arm is maintained at the pressing position, so the temporary decompression operation can be performed quickly and smoothly with a short stroke of the decompression arm.
［１２］前記減圧カムは、減圧状態が形成される領域として、外周に斜面部と平面部とを有し、
減圧を維持する時間の長短に応じて、斜面部と平面部を使い分ける
ことを特徴とする［１］に記載の二次転写装置。
[ 12 ] The decompression cam has a sloped portion and a flat portion on its outer periphery as a region in which a decompressed state is formed,
The secondary transfer device according to [1] , wherein the sloped portion and the flat portion are selectively used according to the length of time for which the reduced pressure is maintained.
上記発明では、減圧状態を長く形成する場合に平面部を使えば、カムの回転を停止させて減圧状態を維持することが容易になる。 In the above invention, if the flat portion is used when the reduced pressure state is to be formed for a long time, it becomes easy to stop the rotation of the cam and maintain the reduced pressure state.
［１３］前記二次転写ローラは、二次転写ユニットに設けられ、
前記圧着解除機構および前記高速減圧機構は、前記二次転写ユニットを変位させる
ことを特徴とする［１］乃至［１２］のいずれか１つに記載の二次転写装置。
[ 13 ] The secondary transfer roller is provided in a secondary transfer unit,
The secondary transfer device according to any one of [1] to [ 13 ], wherein the pressure release mechanism and the high-speed decompression mechanism displace the secondary transfer unit.
上記発明では、二次転写ローラを変位させるために力を加える場所を二次転写ユニットのフレーム等に設定できるので配置の自由度が高まる。また、メンテナンス性等が向上する。 In the above invention, the place where the force is applied to displace the secondary transfer roller can be set on the frame of the secondary transfer unit or the like, so the degree of freedom of arrangement is increased. In addition, maintainability and the like are improved.
［１４］前記圧着解除機構および前記高速減圧機構を、前記二次転写ユニットの下方に設けた
ことを特徴とする［１３］に記載の二次転写装置。
[ 14 ] The secondary transfer device according to [ 13 ], wherein the pressure release mechanism and the high-speed decompression mechanism are provided below the secondary transfer unit.
上記発明では、二次転写装置を含む画像形成装置全体の小型化に貢献する。 The above invention contributes to miniaturization of the entire image forming apparatus including the secondary transfer device.
［１５］前記圧着カムを軸方向へ移動させて、前記圧着カムと前記圧着アーム側との係合が解除されることにより、前記押圧の状態を解除する
ことを特徴とする［１］に記載の二次転写装置。
[ 15 ] The pressing state is released by moving the pressing cam in the axial direction to release the engagement between the pressing cam and the pressing arm. secondary transfer device.
上記発明では、回転軸を軸方向に移動させることで、カムと圧着アーム側との係合が解除される。 In the above invention, the engagement between the cam and the crimping arm is released by axially moving the rotating shaft.
［１６］前記減圧カムを軸方向へ移動させて、前記減圧カムと前記減圧アームとの係合が解除されることにより、前記減圧の状態を解除する
ことを特徴とする［１］に記載の二次転写装置。
[ 16 ] The decompression state is released by moving the decompression cam in the axial direction to release the engagement between the decompression cam and the decompression arm. Secondary transfer device.
上記発明では、回転軸を軸方向に移動させることで、減圧カムと減圧アームとの係合が解除される。 In the above invention, the engagement between the decompression cam and the decompression arm is released by axially moving the rotating shaft.
本発明に係る二次転写装置によれば、用紙の先後端が転写ニップを通る際のニップ圧を一時的に減圧する機能を備えつつ装置の小型化を図ることができる。 According to the secondary transfer device of the present invention, it is possible to reduce the size of the device while providing the function of temporarily reducing the nip pressure when the leading and trailing edges of the paper pass through the transfer nip.
以下、図面に基づき本発明の実施の形態を説明する。 BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below based on the drawings.
図１は、本発明の実施の形態に係る二次転写装置を含む画像形成装置１０の概略構成を示している。画像形成装置１０は、原稿を光学的に読み取って得た画像を記録紙等の記録材上に画像形成して出力するコピー機能、外部から入力された印刷データに基づいてラスタライズした画像を記録紙上に画像形成して出力する印刷機能などを備えた、所謂、複合機である。記録材は記録紙に限定されず、フィルムや布なでもよい。以後、記録材を記録紙として説明する。 FIG. 1 shows a schematic configuration of an image forming apparatus 10 including a secondary transfer device according to an embodiment of the invention. The image forming apparatus 10 has a copy function for forming an image obtained by optically reading a document on a recording material such as recording paper and outputting the image, and an image rasterized based on print data input from the outside on the recording paper. It is a so-called multi-function device that has a printing function for forming and outputting an image on a printer. The recording material is not limited to recording paper, and may be film or cloth. Hereinafter, the recording material will be described as recording paper.
画像形成装置１０は、原稿を光学的に読み取るスキャナ部１１、ユーザ操作の受け付けおよび各種情報を表示する操作パネル１２、装置全体の動作の制御や画像処理を行う制御回路部１３、記録材上に未定着のトナー像を形成する画像形成部２０、未定着のトナー像を記録紙に定着させる定着装置１５、画像形成に使用される記録紙を多数枚収容可能な給紙トレイ１４、給紙トレイ１４から繰り出された用紙を搬送する搬送部１６などを備えて構成される。 The image forming apparatus 10 includes a scanner unit 11 that optically reads a document, an operation panel 12 that accepts user operations and displays various information, a control circuit unit 13 that controls the operation of the entire apparatus and performs image processing, and a recording material. An image forming unit 20 for forming an unfixed toner image, a fixing device 15 for fixing an unfixed toner image on recording paper, a paper feed tray 14 capable of accommodating a large number of recording papers used for image formation, and a paper feed tray. 14 is provided with a transport unit 16 for transporting the paper fed out from the transport unit 14 and the like.
画像形成部２０は、電子写真方式によりトナー像を形成する。画像形成部２０は、複数のローラに巻き掛け渡された無端環状で所定幅の中間転写ベルト２１と、中間転写ベルト２１の外周面に、それぞれ一の色成分のトナー像を形成(一次転写)するイエロ（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（Ｋ）、の色別の像形成ユニット２２Ｙ、２２Ｍ、２２Ｃ、２２Ｋと、中間転写ベルトの外周面に形成されたトナー像を記録紙に二次転写する二次転写装置３０を有する。なお、色別の像形成ユニット２２Ｙ、２２Ｍ、２２Ｃ、２２Ｋを総称して像形成ユニット２２とする。 The image forming section 20 forms a toner image by electrophotography. The image forming unit 20 forms an endless annular intermediate transfer belt 21 having a predetermined width wound around a plurality of rollers, and forms a toner image of one color component on each of the outer peripheral surfaces of the intermediate transfer belt 21 (primary transfer). Image forming units 22Y, 22M, 22C, and 22K for yellow (Y), magenta (M), cyan (C), and black (K), and toner images formed on the outer peripheral surface of the intermediate transfer belt. It has a secondary transfer device 30 for secondary transfer onto recording paper. The image forming units 22Y, 22M, 22C, and 22K for each color are collectively referred to as the image forming unit 22. FIG.
像形成ユニット２２Ｙ、２２Ｍ、２２Ｃ、２２Ｋは、使用されるトナーの色は異なるが互いに構造は同一である。像形成ユニット２２Ｙ、２２Ｍ、２２Ｃ、２２Ｋは、表面に静電潜像が形成される静電潜像担持体としての円筒状の感光体ドラム２４を有し、その周囲に帯電装置、現像装置、転写装置、感光体クリーニング装置などを配置して備える。またレーザ素子であるレーザーダイオード（ＬＤ）、ポリゴンミラー、各種レンズおよびミラー等で構成されたプリントヘッド２６を備えている。 The image forming units 22Y, 22M, 22C, and 22K use different colors of toner, but have the same structure. The image forming units 22Y, 22M, 22C, and 22K each have a cylindrical photosensitive drum 24 as an electrostatic latent image bearing member on which an electrostatic latent image is formed. A transfer device, a photoreceptor cleaning device, etc. are arranged and provided. It also has a print head 26 composed of a laser diode (LD), which is a laser element, a polygon mirror, various lenses, mirrors, and the like.
各像形成ユニット２２Ｙ、２２Ｍ、２２Ｃ、２２Ｋにおいて、感光体ドラム２４は図示省略の駆動部に駆動されて一定方向に回転し、帯電装置は感光体ドラム２４を一様に帯電させ、プリントヘッド２６は対応する色の画像データに基づく駆動信号に応じてオン／オフ制御されたレーザービームで感光体ドラム２４を走査して感光体ドラム２４の表面上に静電潜像を形成する。 In each of the image forming units 22Y, 22M, 22C, and 22K, the photoreceptor drum 24 is driven by a drive unit (not shown) to rotate in a fixed direction, and the charging device uniformly charges the photoreceptor drum 24, and the print head 26 scans the photosensitive drum 24 with a laser beam that is on/off controlled in accordance with a driving signal based on the image data of the corresponding color to form an electrostatic latent image on the surface of the photosensitive drum 24 .
現像装置は、感光体ドラム２４の表面上の静電潜像をトナーで現像して顕像化する現像工程を行う。感光体ドラム２４の表面上に形成されたトナー像は、中間転写ベルト２１と接触する箇所で中間転写ベルト２１に転写(一次転写)される。感光体クリーニング装置は、転写後に感光体ドラム２４の表面上に残留するトナーをブレード等で擦って除去し回収する。 The developing device performs a developing process of developing the electrostatic latent image on the surface of the photoreceptor drum 24 with toner to make it visible. The toner image formed on the surface of the photoreceptor drum 24 is transferred (primary transfer) onto the intermediate transfer belt 21 at a location where it contacts the intermediate transfer belt 21 . The photoreceptor cleaning device removes and collects the toner remaining on the surface of the photoreceptor drum 24 after transfer by rubbing with a blade or the like.
複数のローラに巻き掛けされた中間転写ベルト２１は、図示省略の駆動部に駆動されて図中の矢印Ａ方向に周回する。周回の過程で、各色の像形成ユニット２２Ｙ、２２Ｍ、２２Ｃ、２２Ｋの感光体ドラム２４上に形成されたトナー像が中間転写ベルト２１上に順次転写されて重ね合わされることでフルカラーのカラー画像が中間転写ベルト２１上に合成される。このトナー像は、二次転写位置Ｄに配置された二次転写装置３０によって、中間転写ベルト２１から記録紙上に転写(二次転写)される。また、二次転写後に中間転写ベルト２１に残ったトナーは二次転写位置Ｄの下流に設けられたクリーニング装置２７によって中間転写ベルト２１上から除去される。 The intermediate transfer belt 21 wound around a plurality of rollers is driven by a drive unit (not shown) to rotate in the direction of arrow A in the drawing. In the course of rotation, the toner images formed on the photosensitive drums 24 of the image forming units 22Y, 22M, 22C, and 22K for each color are sequentially transferred onto the intermediate transfer belt 21 and superimposed to form a full-color image. The images are synthesized on the intermediate transfer belt 21 . This toner image is transferred (secondary transfer) from the intermediate transfer belt 21 onto the recording paper by the secondary transfer device 30 arranged at the secondary transfer position D. FIG. Further, the toner remaining on the intermediate transfer belt 21 after the secondary transfer is removed from the intermediate transfer belt 21 by a cleaning device 27 provided downstream of the secondary transfer position D. FIG.
定着装置１５は、記録紙の搬送路の途中であって二次転写位置Ｄの下流に設けられており、二次転写位置Ｄで記録紙の表面上に転写されたトナー像を該記録紙に加圧、加熱して定着させる。 The fixing device 15 is provided downstream of the secondary transfer position D in the middle of the conveying path of the recording paper, and applies the toner image transferred onto the surface of the recording paper at the secondary transfer position D onto the recording paper. Apply pressure and heat to fix.
搬送部１６は、給紙トレイ１４から繰り出した記録紙を、二次転写位置Ｄおよび定着装置１５を通過させて排紙トレイ１７まで搬送する機能を果たす。搬送部１６は、搬送経路を形成する搬送ローラやガイドのほか、搬送ローラを駆動するモータなどで構成される。なお、図示省略するが、搬送部１６は、定着装置１５を出た記録紙を、表裏を反転させて、再び、二次転写位置Ｄの上流の搬送経路に送り出す両面印刷用の用紙反転機構を備えている。 The transport unit 16 has a function of transporting the recording paper drawn out from the paper feed tray 14 through the secondary transfer position D and the fixing device 15 to the paper discharge tray 17 . The transport unit 16 includes transport rollers and guides that form a transport path, a motor that drives the transport rollers, and the like. Although not shown, the conveying unit 16 has a sheet reversing mechanism for double-sided printing, which reverses the front and back of the recording paper discharged from the fixing device 15 and feeds it again to the conveying path upstream of the secondary transfer position D. I have.
制御回路部１３は、ＣＰＵ（Central Processing Unit）、ＲＯＭ（Read Only Memory）、ＲＡＭ（Random Access Memory）、などを主要部として構成される。ＣＰＵがＲＯＭに格納されたプログラムに従って処理を実行することで画像形成装置１０としての各機能が実現される。制御回路部１３は、搬送部１６や画像形成部２０、二次転写装置３０等の動作を制御する。 The control circuit unit 13 is mainly composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. Each function of the image forming apparatus 10 is realized by the CPU executing processes according to programs stored in the ROM. The control circuit portion 13 controls operations of the conveying portion 16, the image forming portion 20, the secondary transfer device 30, and the like.
図２は、二次転写装置３０の左側面図（図１において、定着装置１５側から見た二次転写装置３０を見た図）であり、図３は図２のA-A断面に対応する図であり、図４は図２のB-B断面に対応する図である。また、図５は、二次転写装置３０の分解斜視図である。図６～図８は、二次転写装置３０の機械構成の主要部を抜き出してその動作の概要を示す図である。 2 is a left side view of the secondary transfer device 30 (a view of the secondary transfer device 30 as seen from the fixing device 15 side in FIG. 1), and FIG. 3 is a view corresponding to the AA section of FIG. , and FIG. 4 is a view corresponding to the B-B cross section of FIG. 5 is an exploded perspective view of the secondary transfer device 30. FIG. 6 to 8 are diagrams extracting the main parts of the mechanical configuration of the secondary transfer device 30 and showing the outline of its operation.
二次転写装置３０は、中間転写ベルト２１の幅方向を軸方向とする二次転写ローラ４１を二次転写位置Ｄにおいて中間転写ベルト２１の外周面に押し当てることで、中間転写ベルト２１が巻き掛けられた複数のローラの内の該二次転写ローラ４１と対向する箇所に配置されたローラ（対向ローラ２８）との間に中間転写ベルト２１を挟み込んで転写ニップを形成する。以後、中間転写ベルト２１の幅方向（二次転写ローラ４１の軸方向）を「前奥方向」とする。また、前奥方向の端部側となる相対位置を「外側」、前奥方向の中央寄りとなる相対位置を「内側」と呼ぶものとする。 The secondary transfer device 30 presses a secondary transfer roller 41 whose axial direction is the width direction of the intermediate transfer belt 21 against the outer circumferential surface of the intermediate transfer belt 21 at the secondary transfer position D, thereby winding the intermediate transfer belt 21 . The intermediate transfer belt 21 is sandwiched between the intermediate transfer belt 21 and a roller (facing roller 28 ) arranged at a position facing the secondary transfer roller 41 among the plurality of rollers, thereby forming a transfer nip. Hereinafter, the width direction of the intermediate transfer belt 21 (the axial direction of the secondary transfer roller 41) will be referred to as the "front-back direction". Also, the relative position on the end side in the front-back direction is called "outside", and the relative position near the center in the front-back direction is called "inner side".
二次転写ローラ４１は、図３、図５に示すように、二次転写ユニット４０に組み込まれている。二次転写ユニット４０は、枠部材４２に二次転写ローラ４１を回動自在に軸支すると共に用紙を転写ニップへ案内するガイド板４３等を枠部材４２に取り付けて構成される。 The secondary transfer roller 41 is incorporated in the secondary transfer unit 40 as shown in FIGS. The secondary transfer unit 40 has a frame member 42 on which a secondary transfer roller 41 is rotatably supported, and a guide plate 43 for guiding a sheet to a transfer nip and the like are attached to the frame member 42 .
二次転写装置３０は、上記の二次転写ユニット４０と、二次転写ローラ４１が中間転写ベルト２１に圧着して転写ニップを形成する押圧位置と二次転写ローラ４１が中間転写ベルト２１から離れた離隔位置とに変位するように二次転写ユニット４０を変位させる圧着解除部(圧着解除機構)５０と、圧着解除部５０を駆動するモータやギア等からなる第１駆動部５２と、押圧位置にされた二次転写ローラ４１が中間転写ベルト２１を対向ローラ２８との間に挟んで押圧するニップ圧を、用紙の先端および後端が二次転写箇所Ｄ（二次転写ローラ４１と中間転写ベルト２１の間）を通る際に一時的に減圧する高速減圧部（高速減圧機構）７０と、高速減圧部７０を駆動するモータ等からなる第２駆動部７２をフレーム部材３２に取り付けて構成される(図５参照)。 The secondary transfer device 30 includes the secondary transfer unit 40 , a pressing position where the secondary transfer roller 41 is pressed against the intermediate transfer belt 21 to form a transfer nip, and a secondary transfer roller 41 separated from the intermediate transfer belt 21 . A press release portion (press release mechanism) 50 for displacing the secondary transfer unit 40 so as to displace it to the separated position, a first drive portion 52 including a motor, gears, etc. for driving the press release portion 50, and a pressing position. The nip pressure at which the secondary transfer roller 41 presses the intermediate transfer belt 21 between itself and the counter roller 28 is applied to the secondary transfer location D (the secondary transfer roller 41 and the intermediate transfer belt 21). A high-speed depressurizing section (high-speed depressurizing mechanism) 70 that temporarily depressurizes when passing through the belt 21) and a second driving section 72 including a motor or the like for driving the high-speed depressurizing section 70 are attached to the frame member 32. (See Figure 5).
図２、図５に示すように、フレーム部材３２は、二次転写装置３０の前奥方向に長い長方形平板状の底板部３２ａと、底板部３２ａの前奥方向の両端近傍から互いに向き合って立設された一対の支持板３２ｂを有する。対向するそれぞれの支持板３２ｂは、下部が底板部３２ａにネジ止めされており、上部は下部に比べて幅細の形状にされている。各支持板３２ｂの上端近傍には、二次転写ユニット４０を揺動可能に支持する所定長のユニット支持軸３４が前奥方向の外側へ突出して設けられている。 As shown in FIGS. 2 and 5, the frame member 32 includes a bottom plate portion 32a in the shape of a rectangular flat plate elongated in the front and rear direction of the secondary transfer device 30, and a bottom plate portion 32a facing each other from near both ends in the front and rear direction of the bottom plate portion 32a. It has a pair of supporting plates 32b provided. Each supporting plate 32b facing each other has its lower portion screwed to the bottom plate portion 32a, and its upper portion is narrower than its lower portion. In the vicinity of the upper end of each support plate 32b, a unit support shaft 34 having a predetermined length for swingably supporting the secondary transfer unit 40 is provided so as to protrude outward in the front-rear direction.
二次転写ユニット４０は前奥方向の両端を上記のユニット支持軸３４に軸支され、該ユニット支持軸３４を中心に揺動することで、ユニット支持軸３４から用紙搬送方向の下流側へ所定距離離れた位置に軸心を有する二次転写ローラ４１が押圧位置と離脱位置とに変位する。 The secondary transfer unit 40 is pivotally supported by the unit support shafts 34 at both ends in the front and back direction, and swings around the unit support shafts 34 to move from the unit support shaft 34 to a predetermined downstream side in the paper transport direction. The secondary transfer roller 41 having its axis at a distance is displaced between the pressing position and the releasing position.
圧着解除部５０は、二次転写ローラ４１の軸と同方向であって第１駆動部５２によって駆動される回転軸５３に支持されて回転する圧着カム５４と、圧着カム５４に当接して揺動することで二次転写ユニット４０を押圧位置と離隔位置に変位させる圧着アーム５５を有する。圧着カム５４および圧着アーム５５は、各支持板３２ｂに対応して、前奥方向の両端にそれぞれ設けてある。 The pressure release portion 50 includes a pressure cam 54 that rotates while being supported by a rotating shaft 53 driven by a first driving portion 52 in the same direction as the shaft of the secondary transfer roller 41 , and a pressure cam 54 that contacts and swings. It has a pressing arm 55 that moves to displace the secondary transfer unit 40 between the pressing position and the separating position. The compression cam 54 and the compression arm 55 are provided at both ends in the front-rear direction corresponding to each support plate 32b.
圧着アーム５５は、一端部の回転支点５５ａが、ユニット支持軸３４のやや下方において支持板３２ｂに取り付けられた支持軸３６(図２、図３、図５参照)に軸支されて揺動可能となっている。圧着アーム５５の回転支点５５ａを軸支する支持軸３６の軸方向は二次転写ローラ４１の軸と同方向である。 A rotation fulcrum 55a at one end of the crimping arm 55 is rotatably supported by a support shaft 36 (see FIGS. 2, 3 and 5) attached to the support plate 32b slightly below the unit support shaft 34. It has become. The axial direction of the support shaft 36 that supports the rotation fulcrum 55 a of the pressing arm 55 is the same as that of the secondary transfer roller 41 .
図３、図６等に示されるように、回転軸５３は、圧着アーム５５の回転支点５５ａの真下よりやや用紙搬送方向の上流側へシフトした位置で支持板３２ｂに回動可能に支持されている。 As shown in FIGS. 3 and 6, the rotary shaft 53 is rotatably supported by the support plate 32b at a position slightly shifted to the upstream side in the paper transport direction from directly below the rotary fulcrum 55a of the crimping arm 55. there is
圧着アーム５５は、一端部(上端部)に前述の回転支点５５ａを有し、他端部(下端部)に圧着カム５４に当接して力点となる当接ローラ５５ｂ(突き当て部材)を有すると共に、途中で側方（用紙搬送方向の上流側）に突出した作用腕５５ｃを備えている(図３、図６参照)。 The pressing arm 55 has the above-mentioned rotation fulcrum 55a at one end (upper end), and has a contact roller 55b (abutting member) at the other end (lower end) that comes into contact with the pressing cam 54 and serves as a point of force. At the same time, a working arm 55c protruding sideways (upstream in the paper conveying direction) is provided in the middle (see FIGS. 3 and 6).
圧着アーム５５の作用腕５５ｃの先端近傍の上面には、螺旋状に上向きに延びるバネ５６が取り付けてあり、このバネ５６の上端は、後述する減圧アーム７５の先端部の下面に接合されている。圧着アーム５５は、作用腕５５ｃの先端近傍のバネ５６の取り付けられた箇所が作用点となっており、転写ニップを形成する際に、バネ５６および減圧アーム７５を介して二次転写ユニット４０の背面を、対向ローラ２８に向けて押圧する。 A spring 56 extending spirally upward is attached to the upper surface near the tip of the working arm 55c of the crimping arm 55, and the upper end of the spring 56 is joined to the lower surface of the tip of the decompression arm 75, which will be described later. . The pressing arm 55 has an action point near the tip of the working arm 55c where the spring 56 is attached. The back surface is pressed against the opposing roller 28 .
圧着解除部５０は、二次転写ローラ４１の軸方向(前奥方向)の両端に分けて配置した２つの圧着カム５４を同位相に備えており、両端部の各圧着アーム５５を用いて、二次転写ユニット４０の背面を、前奥方向の両端部において同時に同じ様に押圧し、また押圧を解除する。 The pressure release unit 50 has two pressure cams 54 arranged separately at both ends in the axial direction (front and back direction) of the secondary transfer roller 41 at the same phase. The rear surface of the secondary transfer unit 40 is similarly pressed at both ends in the front and back direction at the same time, and the pressure is released.
高速減圧部７０は、二次転写ローラ４１の軸と同方向であって第２駆動部７２によって駆動される回転軸７３に取り着けられて回転する減圧カム７４と、減圧カム７４に当接して揺動することで押圧位置にある二次転写ユニット４０をニップ圧が弱まる方向へ変位させる減圧アーム７５を有する。回転軸７３は筒状であり、圧着解除部５０の回転軸５３に外嵌され、回転軸５３と同軸にされている。 The high-speed decompression unit 70 is in contact with the decompression cam 74 , which rotates while being attached to a rotating shaft 73 driven by the second driving unit 72 in the same direction as the shaft of the secondary transfer roller 41 . It has a decompression arm 75 that swings to displace the secondary transfer unit 40 from the pressing position in a direction in which the nip pressure is weakened. The rotating shaft 73 has a cylindrical shape, is fitted onto the rotating shaft 53 of the crimping release portion 50 , and is coaxial with the rotating shaft 53 .
減圧カム７４は、外周のうち、ニップ圧を弱めた減圧状態が形成される領域として、斜面部７４ａと平面部７４ｂを有する(図７参照)。高速減圧部７０の制御においては、減圧を維持する時間の長短に応じてこれらの領域が使い分けされる。 The decompression cam 74 has a slope portion 74a and a plane portion 74b as regions in which a decompressed state in which the nip pressure is weakened is formed (see FIG. 7). In the control of the high-speed depressurizing section 70, these regions are selectively used according to the length of time for which the depressurization is maintained.
同軸にされた減圧カム７４と圧着カム５４は、二次転写ローラ４１の軸方向に投影した投影像が最大限に重なる位置関係となっている。また、圧着カム５４の最大径は減圧カム７４の最小径より小さくされている。 The coaxial decompression cam 74 and pressure cam 54 have a positional relationship in which projected images projected in the axial direction of the secondary transfer roller 41 are superimposed to the maximum extent. Also, the maximum diameter of the pressure cam 54 is smaller than the minimum diameter of the decompression cam 74 .
図２、図５等に示されるように、減圧アーム７５は、前奥方向の両端にある２つの圧着アーム５５のそれぞれに対応して設けてある。減圧アーム７５の一端部は、二次転写ユニット４０の背面を中間転写ベルト２１に向けて押圧する押圧部７５ａとなっており(図３等参照)、該押圧部７５ａの背面には前述のバネ５６の上端が当接している。バネ５６の上端が当接している箇所は、減圧動作において減圧アーム７５の作用点７５ｂとなる。 As shown in FIGS. 2, 5, etc., the decompression arms 75 are provided corresponding to the two crimping arms 55 located at both ends in the front-rear direction. One end of the decompression arm 75 serves as a pressing portion 75a that presses the back surface of the secondary transfer unit 40 toward the intermediate transfer belt 21 (see FIG. 3, etc.). 56 are in contact with each other. The point with which the upper end of the spring 56 abuts becomes the action point 75b of the decompression arm 75 during the decompression operation.
減圧アーム７５の他端は減圧カム７４からの力を受ける力点７５ｄとなっている。ここでは、圧着アーム５５に対応させて前奥方向の両端に分けて設けられた２つの減圧アーム７５の端部の力点７５ｄ同士を、前奥方向に長い減圧軸７７(連結部材)で接続してあり、この減圧軸７７には、該減圧軸７７を軸として自在に回動する前奥方向に長い円筒状の回転体７８が外嵌されている。 The other end of the decompression arm 75 serves as a power point 75 d that receives force from the decompression cam 74 . Here, pressure points 75d at the ends of two decompression arms 75, which are provided separately at both ends in the front and back direction so as to correspond to the crimping arm 55, are connected by a decompression shaft 77 (connecting member) that is long in the front and back direction. A cylindrical rotating body 78 elongated in the front-rear direction is fitted around the decompression shaft 77 so as to freely rotate about the decompression shaft 77 .
回転体７８が減圧カム７４に当接することで減圧アーム７５が揺動するようになっている。減圧カム７４に突き当たる部材を回転体７８とすることで減圧カム７４との摩擦が軽減され、減圧カム７４の耐久性が向上する。なお、回転体７８を設けずに、減圧軸７７が減圧カム７４に当接する構成でもよい。 When the rotor 78 abuts against the decompression cam 74, the decompression arm 75 swings. Friction with the decompression cam 74 is reduced by using the rotating body 78 as the member that abuts the decompression cam 74 , and the durability of the decompression cam 74 is improved. Alternatively, the decompression shaft 77 may contact the decompression cam 74 without providing the rotor 78 .
減圧アーム７５の回転支点７５ｃは、減圧アーム７５の長手方向の中央よりやや減圧軸７７の接続された端部寄りの箇所にある。また該回転支点７５ｃは、圧着アーム５５の回転支点５５ａと同軸となるように支持板３２ｂに軸支されている。減圧アーム７５においては、減圧カム７４からの力を受ける力点７５ｄ（減圧軸７７の接続された箇所）と回転支点７５ｃまでの距離より、回転支点７５ｃから減圧動作時の作用点７５ｂ（バネ５６が背面に当接している箇所）までの距離が長くされている。これにより、小型化および第２駆動部７２の小型化・低コスト化を図ることができる。 The rotation fulcrum 75c of the decompression arm 75 is located slightly closer to the end to which the decompression shaft 77 is connected than the center of the decompression arm 75 in the longitudinal direction. The rotation fulcrum 75c is supported by the support plate 32b so as to be coaxial with the rotation fulcrum 55a of the crimping arm 55. As shown in FIG. In the decompression arm 75, the distance between the force point 75d (the point where the decompression shaft 77 is connected) that receives the force from the decompression cam 74 and the rotation fulcrum 75c is determined from the rotation fulcrum 75c to the action point 75b (the spring 56 is applied at the time of the decompression operation). The distance to the point in contact with the back surface) is increased. Accordingly, miniaturization and miniaturization and cost reduction of the second driving unit 72 can be achieved.
また、圧着アーム５５の回転支点５５ａと圧着カム５４の間に、減圧アーム７５の力点（減圧軸７７の回転体７８）、すなわち、減圧カム７４に当接する箇所が位置するようになっている。これにより、高速減圧機構７０の主要部が圧着解除部５０に内包される配置となり、装置が小型化される。 Also, the point of force of the decompression arm 75 (the rotating body 78 of the decompression shaft 77), that is, the point of contact with the decompression cam 74, is located between the rotation fulcrum 55a of the compression arm 55 and the compression cam . As a result, the main part of the high-speed decompression mechanism 70 is placed inside the pressure release part 50, and the device is miniaturized.
図２に示すように、減圧カム７４は、前奥方向の両端に分けて配置された２つの圧着カム５４の内側近傍となるようにそれぞれ配置されている。また、減圧カム７４の回転軸７３を回転させる第２駆動部７２(モータ等)および減圧カム７４の角度位置を検出する位置検知センサ７６は、２つの減圧カム７４の内側に配置されている。 As shown in FIG. 2, the decompression cams 74 are arranged in the vicinity of the inner sides of the two pressure cams 54 which are arranged separately at both ends in the front-rear direction. A second drive unit 72 (such as a motor) that rotates the rotary shaft 73 of the decompression cam 74 and a position detection sensor 76 that detects the angular position of the decompression cam 74 are arranged inside the two decompression cams 74 .
圧着カム５４が取り付けられた回転軸５３を回転させる第１駆動部５２(モータ等)は、二次転写装置３０の前奥方向の一方の端部に取り付けられている。具体的には、圧着カム５４や圧着アーム５５より外側となる位置に取り付けられている。 A first drive unit 52 (such as a motor) that rotates the rotation shaft 53 to which the pressure cam 54 is attached is attached to one end of the secondary transfer device 30 in the front-rear direction. Specifically, it is attached at a position outside the crimping cam 54 and the crimping arm 55 .
また、図９に示すように、第１駆動部５２と第２駆動部７２は、二次転写ローラ４１の軸方向に投影した場合の投影像が重なるように配置されている。 Further, as shown in FIG. 9, the first driving section 52 and the second driving section 72 are arranged so that the projected images when projected in the axial direction of the secondary transfer roller 41 overlap each other.
また、画像形成装置１０では、二次転写装置３０の圧着解除部５０および高速減圧機構７０は、二次転写位置Ｄに対して中間転写ベルト２１の反対側に配置されている。図１、図３等に示すように、二次転写装置３０（圧着解除部５０、高速減圧機構７０）は、二次転写位置Ｄの下方にあり、中間転写ベルト２１は二次転写位置Ｄの上方にあり、圧着解除部５０、高速減圧機構７０は二次転写位置Ｄに対して中間転写ベルト２１の反対側に位置している。 Further, in the image forming apparatus 10 , the pressure release unit 50 and the high-speed decompression mechanism 70 of the secondary transfer device 30 are arranged on the opposite side of the intermediate transfer belt 21 with respect to the secondary transfer position D. As shown in FIGS. 1, 3, etc., the secondary transfer device 30 (pressure release unit 50, high-speed decompression mechanism 70) is located below the secondary transfer position D, and the intermediate transfer belt 21 is located below the secondary transfer position D. The pressure release unit 50 and the high-speed decompression mechanism 70 are located above the intermediate transfer belt 21 with respect to the secondary transfer position D. As shown in FIG.
次に、二次転写装置３０の動作について説明する。 Next, the operation of the secondary transfer device 30 will be described.
図６は、二次転写ユニット４０が離隔位置にある状態を示している。図７は、二次転写ユニット４０が押圧位置にある状態(圧着状態)を示している。図８は、高速減圧部７０が動作してニップ圧を減圧した状態を示している。 FIG. 6 shows a state where the secondary transfer unit 40 is at the separated position. FIG. 7 shows a state (pressing state) in which the secondary transfer unit 40 is at the pressing position. FIG. 8 shows a state in which the high-speed pressure reducing section 70 operates to reduce the nip pressure.
二次転写装置３０は、第１駆動部５２で圧着解除部５０の回転軸５３を回転させると、回転軸５３に取り付けられた圧着カム５４が回転し、この圧着カム５４に下端の当接ローラ５５ｂが当接された圧着アーム５５が圧着カム５４の角度位置に応じて回転支点５５ａを中心に揺動する。 In the secondary transfer device 30, when the rotating shaft 53 of the pressing release portion 50 is rotated by the first driving portion 52, the pressing cam 54 attached to the rotating shaft 53 rotates. The crimping arm 55 with the contact 55b swings about the rotation fulcrum 55a in accordance with the angular position of the crimping cam 54. As shown in FIG.
二次転写ユニット４０を離隔位置から押圧位置へ変位させるとき、圧着アーム５５は、図６に示す位置から右方向(時計回り)に回転し、作用腕５５ｃの先端近傍の作用点で、バネ５６および減圧アーム７５をこの順に介して、二次転写ユニット４０を中間転写ベルト２１に向けて押圧する。図７は、高速減圧部７０による減圧が作用していない状態であり、減圧カム７４は、減圧アーム７５の力点（減圧軸７７の回転体７８）に当接しない角度位置になっている。従って、この状態では減圧アーム７５は減圧カム７４から力を受けず、圧着解除部５０の圧着動作に従って変位する。 When the secondary transfer unit 40 is displaced from the separated position to the pressing position, the pressing arm 55 rotates rightward (clockwise) from the position shown in FIG. and the decompression arm 75 in this order, the secondary transfer unit 40 is pressed toward the intermediate transfer belt 21 . FIG. 7 shows a state in which the high-speed decompression unit 70 does not depressurize, and the decompression cam 74 is at an angular position where it does not contact the force point of the decompression arm 75 (the rotating body 78 of the decompression shaft 77). Accordingly, in this state, the decompression arm 75 does not receive force from the decompression cam 74 and is displaced according to the crimping operation of the crimp release portion 50 .
図７に示す位置に圧着解除部５０の圧着カム５４を保持した状態で、高速減圧部７０の減圧カム７４を所定の角度位置に回転させると、図８に示すように、減圧カム７４が減圧アーム７５の力点（減圧軸７７の回転体７８）に当接して、減圧アーム７５は回転支点７５ｃを中心に反時計方向へ僅かに回転し、回転支点を挟んで力点７５ｄの反対側の端部にある作用点７５ｂでバネ５６を介して圧着アーム５５を押し戻す位置に変位する。 When the decompression cam 74 of the high-speed decompression section 70 is rotated to a predetermined angular position while the decompression cam 54 of the decompression release section 50 is held at the position shown in FIG. Abutting against the point of force of the arm 75 (rotating body 78 of the decompression shaft 77), the decompression arm 75 slightly rotates counterclockwise about the rotation fulcrum 75c, and the end opposite to the point of force 75d across the rotation fulcrum. The pressure arm 55 is displaced to the position where the pressure arm 55 is pushed back via the spring 56 at the action point 75b at .
すなわち、減圧アーム７５は、圧着アーム５５がバネ５６を介して二次転写ユニット４０へ及ぼす押圧力を遮ることで、ニップ圧を減圧する。このとき、対向ローラ２８と二次転写ローラ４１との軸間距離は、非接触時の対向ローラ２８の半径と二次転写ローラ４１の半径の合計よりある程度短くなっており、ニップ圧は、二次転写ローラ４１や対向ローラ２８の外周部材が持つ弾性によって生じている。 That is, the decompression arm 75 reduces the nip pressure by interrupting the pressing force exerted by the compression arm 55 on the secondary transfer unit 40 via the spring 56 . At this time, the axial distance between the opposing roller 28 and the secondary transfer roller 41 is somewhat shorter than the sum of the radius of the opposing roller 28 and the radius of the secondary transfer roller 41 in the non-contact state, and the nip pressure is This is caused by the elasticity of the peripheral members of the next transfer roller 41 and the opposing roller 28 .
このように、本発明に係る二次転写装置３０は、二次転写ユニット４０を押圧位置に変位させる圧着解除部５０とは別の機構である高速減圧部７０によって減圧状態を一時的に形成するので、一時的な減圧状態を的確なタイミングで容易かつ円滑に形成することができる。 As described above, the secondary transfer device 30 according to the present invention temporarily creates a decompressed state by the high-speed depressurizing section 70, which is a mechanism different from the press release section 50 that displaces the secondary transfer unit 40 to the pressing position. Therefore, a temporary reduced pressure state can be easily and smoothly formed at an appropriate timing.
すなわち、圧着動作は、圧着アーム５５がバネ５６および減圧アーム７５を介して二次転写ユニット４０を押圧することによって行い、減圧動作は減圧アーム７５を、バネ５６を圧着アーム５５側へ押し戻すように変位させて行うので、圧着解除部５０が圧着アーム５５を離隔位置方向に向けて少し変位させることで減圧するような仕組みに比べて、適切な減圧の程度を容易に得ることができる。また、減圧動作における減圧アーム７５の動作ストロークが小さくて済むので、減圧および減圧の解除の動作を高速に行うことができる。 That is, the pressing operation is performed by the pressing arm 55 pressing the secondary transfer unit 40 via the spring 56 and the decompressing arm 75 , and the depressurizing operation is performed by pushing the decompressing arm 75 back toward the pressing arm 55 side. Since the pressure is displaced, an appropriate degree of pressure reduction can be easily obtained compared to a mechanism in which the pressure is reduced by slightly displacing the pressure contact arm 55 toward the separated position. In addition, since the operation stroke of the pressure reducing arm 75 in the pressure reducing operation is small, the pressure reducing and pressure releasing operations can be performed at high speed.
制御回路部１３は、用紙の先端および後端が二次転写位置Ｄを通る際に圧着(ニップ圧)が一時的に減圧されるように高速減圧部７０の第２駆動部７２を制御する。具体的には、二次転写位置Ｄの用紙搬送方向のやや上流に用紙の先端・後端を検出するセンサを設けておき、このセンサが用紙の先後端を検出したタイミングを基準にして、該用紙の先端および後端が二次転写位置Ｄを通る時刻の前後所定期間だけ減圧状態となるように減圧カム７４の角度位置を第２駆動部７２によって制御する。 The control circuit unit 13 controls the second driving unit 72 of the high-speed pressure reducing unit 70 so that the pressure (nip pressure) is temporarily reduced when the leading edge and the trailing edge of the sheet pass through the secondary transfer position D. Specifically, a sensor for detecting the leading edge and the trailing edge of the sheet is provided slightly upstream of the secondary transfer position D in the sheet conveying direction, and the sensor detects the leading edge and the trailing edge of the sheet as a reference. The angular position of the decompression cam 74 is controlled by the second drive section 72 so that the pressure is reduced for a predetermined period before and after the leading edge and the trailing edge of the sheet pass through the secondary transfer position D. FIG.
減圧カム７４には、減圧状態が形成される領域として、外周に斜面部７４ａと平面部７４ｂが設けてあり、制御回路部１３は、高速減圧部７０の制御においては、減圧を維持する時間の長短に応じてこれらの領域を使い分ける。 The decompression cam 74 is provided with a sloped portion 74a and a flat portion 74b on the outer circumference as regions in which a decompressed state is formed. These areas are used according to their merits and demerits.
詳細には、制御回路部１３は、減圧状態を一定時間以上維持す場合は、減圧カム７４の平面部７４ｂが減圧アーム７５の力点（減圧軸７７の回転体７８）に当接するように減圧カム７４の角度位置を設定して減圧状態を形成し、その位置で第２駆動部７２を停止させて、減圧状態を維持する。 Specifically, when the reduced pressure state is to be maintained for a certain period of time or more, the control circuit unit 13 controls the pressure reduction cam so that the plane portion 74b of the pressure reduction cam 74 contacts the pressure point of the pressure reduction arm 75 (rotating body 78 of the pressure reduction shaft 77). The angular position of 74 is set to form a reduced pressure state, and the second drive section 72 is stopped at that position to maintain the reduced pressure state.
一方、減圧状態を維持する時間が一定時間未満の短時間ならば、制御回路部１３は、減圧アーム７５の力点（減圧軸７７の回転体７８）が減圧カム７４の斜面部７４ａを利用して減圧状態を形成する。具体的には、第２駆動部７２を駆動したまま（減圧カム７４を回転させたまま）で減圧状態が必要時間発生する角度範囲に渡って連続的に斜面部７４ａを形成しておき、制御回路部１３は、必要時間の減圧状態を、第２駆動部７２を駆動して減圧カム７４の回転を維持したまま形成する。 On the other hand, if the decompressed state is maintained for a short period of time less than the predetermined time, the control circuit unit 13 causes the force point of the decompressing arm 75 (the rotating body 78 of the decompressing shaft 77) to move through the slope portion 74a of the decompressing cam 74. Create a vacuum. Specifically, the slope portion 74a is continuously formed over an angle range in which the decompression state occurs for the required time while the second driving portion 72 is being driven (while the decompression cam 74 is being rotated). The circuit unit 13 drives the second driving unit 72 to create a decompression state for the required time while maintaining the rotation of the decompression cam 74 .
たとえば、図７にように平面部７４ｂの両側に斜面部７４ａを設けた場合には、減圧カム７４の回転を継続することで、回転体７８が減圧カム７４の斜面部７４ａ、平面部７４ｂ、斜面部７４ａを順に当接し、その間、継続的に減圧状態が形成される。回転体７８が一方の斜面部７４ａから平面部７４ｂに当接する角度位置となった時に減圧カム７４の回転を一時停止させれば、一時停止させている間、減圧状態を延長することができる。 For example, when slope portions 74a are provided on both sides of a plane portion 74b as shown in FIG. The inclined surfaces 74a are successively brought into contact with each other, and a decompressed state is continuously formed in the meantime. If the rotation of the decompression cam 74 is temporarily stopped when the rotating body 78 reaches the angular position where it abuts on the plane portion 74b from one of the slope portions 74a, the decompression state can be extended while the decompression cam 74 is temporarily stopped.
減圧カム７４に平面部７４ｂを設けたことにより、一定時間以上の減圧状態をモータの励磁を止めて形成できるので、電力消費の低減、モータの小型化・低電力化を図ることができる。また、減圧状態を短時間形成して解除する場合には、減圧カム７４を回転させ続ければよいので、第２駆動部７２の制御が容易になる。 By providing the flat portion 74b on the decompression cam 74, the decompression state for a certain time or more can be formed by stopping the excitation of the motor, so power consumption can be reduced, and the size and power consumption of the motor can be reduced. Further, when the depressurized state is formed for a short period of time and released, the depressurizing cam 74 can be kept rotating, so the control of the second driving section 72 is facilitated.
また、圧着カム５４を保持する回転軸５３と減圧カム７４を保持する回転軸７３を同軸としたので、これらのカムの角度位置を制御する際の位置精度が向上する。 Further, since the rotating shaft 53 that holds the pressure cam 54 and the rotating shaft 73 that holds the decompression cam 74 are coaxial, the positional accuracy is improved when controlling the angular positions of these cams.
二次転写装置３０は以下の構成により小型化されている。まず、圧着解除部５０と高速減圧部７０を二次転写ローラ４１の軸方向に投影した場合の投影像が重なるように配置してある。より詳細には、圧着カム５４と減圧カム７４を、二次転写ローラ４１の軸方向に投影した場合の投影像が一部または全部重なる配置となっている。これにより、二次転写ローラ４１の軸に垂直な断面における二次転写装置３０の面積が小さくなる。 The secondary transfer device 30 is miniaturized by the following configuration. First, the press releasing portion 50 and the high-speed depressurizing portion 70 are arranged so that projected images when projected in the axial direction of the secondary transfer roller 41 overlap each other. More specifically, the projection images of the pressing cam 54 and the decompression cam 74 when projected in the axial direction of the secondary transfer roller 41 overlap partially or wholly. This reduces the area of the secondary transfer device 30 in the cross section perpendicular to the axis of the secondary transfer roller 41 .
本実施の形態では、圧着カム５４の回転軸５３と減圧カム７４の回転軸７３を同軸とすることで、これらのカムの重なりが最も大きくなっている。 In the present embodiment, the rotation shaft 53 of the pressure cam 54 and the rotation shaft 73 of the decompression cam 74 are made coaxial, so that the overlap between these cams is maximized.
また、図９に示すように、第１駆動部５２と第２駆動部７２についても、二次転写ローラ４１の軸方向に投影した場合の投影像が重なる配置となっており、二次転写ローラ４１の軸に垂直な断面における二次転写装置３０の面積の低減を図っている。 Further, as shown in FIG. 9, the first driving section 52 and the second driving section 72 are also arranged such that the projected images when projected in the axial direction of the secondary transfer roller 41 overlap each other. The area of the secondary transfer device 30 in the cross section perpendicular to the axis of 41 is intended to be reduced.
また、圧着解除部５０および高速減圧部７０を二次転写位置に対して中間転写ベルトの反対側に配置することで、これらを中間転写ベルトの内側に設ける場合に比べて、中間転写ベルトの周回ルートを小さくでき、二次転写装置を含む画像形成装置のサイズの小型化が可能になる。さらにまた、圧着解除部５０および高速減圧部７０を、二次転写ユニット４０の下方に設けることで、二次転写装置３０を含めた画像形成部２０全体の小型化を図っている。 In addition, by arranging the pressure releasing unit 50 and the high-speed pressure reducing unit 70 on the opposite side of the intermediate transfer belt with respect to the secondary transfer position, the rotation of the intermediate transfer belt is reduced compared to the case where they are provided inside the intermediate transfer belt. The route can be made smaller, and the size of the image forming apparatus including the secondary transfer device can be reduced. Furthermore, by disposing the pressure releasing section 50 and the high-speed pressure reducing section 70 below the secondary transfer unit 40, the size of the entire image forming section 20 including the secondary transfer device 30 is reduced.
さらに図２に示すように、圧着アーム５５および圧着カム５４を、前奥方向（二次転写ローラ４１の軸方向）の両端に分かれた２箇所に設け、これらの内側に減圧カム７４を配置したので、減圧カム７４を圧着カム５４の外側に設ける場合に比べて、前奥方向における装置の小型化を図ることができる。図２に示す構成では、減圧カム７４を、前奥方向に離して、各圧着カム５４の内側近傍の２箇所に設けたので、減圧アーム７５の近くで、減圧のための力を減圧軸７７の回転体７８に与えることができ、減圧軸７７の撓みを低減することができる。 Further, as shown in FIG. 2, the pressing arm 55 and the pressing cam 54 are provided at two locations separated at both ends in the front-rear direction (the axial direction of the secondary transfer roller 41), and the decompression cam 74 is placed inside them. Therefore, compared to the case where the decompression cam 74 is provided outside the pressure cam 54, it is possible to reduce the size of the device in the front-rear direction. In the configuration shown in FIG. 2, the decompression cams 74 are spaced apart in the front and back direction and provided at two locations near the inner side of each pressure cam 54 . can be applied to the rotating body 78, and the deflection of the pressure reducing shaft 77 can be reduced.
なお、図１０に示すように、減圧カム７４を、前奥方向の両端に分けて設けられた２つの圧着カム５４の内側であって、前奥方向の中心に１つのみ配置するように構成してもよい。図２のように前奥方向に分かれた２箇所に減圧カム７４を設ける場合、カムの形状や位相ズレ等により、それらの減圧動作に差が生じるおそれがあるが、前奥方向の中心の１箇所にのみ減圧カム７４を設ける構成では上記の差の影響を受けずに、両端の減圧アーム７５を同期させて減圧動作を行うことができる。 In addition, as shown in FIG. 10, only one decompression cam 74 is arranged inside the two crimping cams 54 provided separately at both ends in the front-rear direction and at the center in the front-rear direction. You may When the decompression cams 74 are provided at two locations separated in the front and back direction as shown in FIG. In the configuration in which the decompression cams 74 are provided only at the locations, the decompression arms 75 at both ends can be synchronized to perform the decompression operation without being affected by the above difference.
また、図２のように、前奥方向の両端に分けて２つの減圧カム７４を配置する場合に、それらの内側に、第２駆動部７２や減圧カム７４の角度位置を検出する位置検知センサ７６を配置することで、二次転写装置３０の前奥方向のサイズが小型化される。なお、図１０に示すように減圧カム７４が１つの構成においても、前奥方向の両端に分かれた２つの圧着カム５４の内側に、第２駆動部７２や位置検知センサ７６を配置することで二次転写装置３０の前奥方向のサイズが小型化される。 As shown in FIG. 2, when two decompression cams 74 are arranged at both ends in the front-rear direction, a position detection sensor for detecting the angular positions of the second drive unit 72 and the decompression cam 74 is installed inside them. By arranging 76, the size of the secondary transfer device 30 in the front-rear direction is reduced. As shown in FIG. 10, even in a configuration in which one decompression cam 74 is provided, by arranging the second drive unit 72 and the position detection sensor 76 inside the two compression cams 54 separated at both ends in the front-rear direction, The front-back direction size of the secondary transfer device 30 is reduced.
また、減圧アーム７５が減圧カム７４からの力を受ける力点（減圧軸７７の接続箇所）と、減圧アーム７５の作用点（バネ５６の先端が当接する箇所）との間に、減圧アーム７５の回転支点７５ｃが設けてあるので、減圧アーム７５の作用点が減圧のためにバネ５６に力を与える方向と、減圧時に減圧アーム７５の力点が押圧される方向が逆となり、配置の自由度が高まり、小型化に寄与する配置を選択することができる。 In addition, the force of the decompression arm 75 is located between the force point (the connection point of the decompression shaft 77) where the decompression arm 75 receives the force from the decompression cam 74 and the action point of the decompression arm 75 (the point where the tip of the spring 56 abuts). Since the rotation fulcrum 75c is provided, the direction in which the action point of the decompression arm 75 exerts force on the spring 56 for decompression is opposite to the direction in which the force point of the decompression arm 75 is pressed during decompression, thereby increasing the degree of freedom of arrangement. It is possible to select an arrangement that increases the size and contributes to miniaturization.
また、二次転写ローラ４１を二次転写ユニット４０に組み込んでユニット化したので、小型化、メンテナンス性の向上、高速減圧部７０の交換性などが向上する。また、二次転写ローラ４１を変位させるための力を加える場所を二次転写ユニット４０の枠部材４２の任意の箇所等に設定できるので、各部の配置の自由度が高まる。 In addition, since the secondary transfer roller 41 is incorporated into the secondary transfer unit 40 to form a unit, it is possible to reduce the size, improve maintainability, and improve the replaceability of the high-speed decompression unit 70 . In addition, since the position to which the force for displacing the secondary transfer roller 41 is applied can be set to an arbitrary position of the frame member 42 of the secondary transfer unit 40, the degree of freedom in arranging each part is increased.
また、圧着カム５４と減圧カム７４の関係は、同軸とした上で、圧着カム５４の最大径が、減圧カム７４の最小径より小さくされている。これにより、圧着カム５４の位置に係らず減圧カム７４による減圧動作を実施することができる。なお、圧着カム５４の最小径が減圧カム７４の最大径より大きい構成とすれば、減圧カム７４の位置に係らず、圧着カム５４による圧着動作を実施することができる。 In addition, the compression cam 54 and the decompression cam 74 are coaxial, and the maximum diameter of the compression cam 54 is smaller than the minimum diameter of the decompression cam 74 . Thereby, the decompression operation by the decompression cam 74 can be performed regardless of the position of the pressure cam 54 . If the minimum diameter of the compression cam 54 is larger than the maximum diameter of the decompression cam 74 , the compression cam 54 can perform the compression operation regardless of the position of the decompression cam 74 .
このほか、圧着カム５４の回転軸５３は図示省略のロック機構を解除すると軸方向への移動が可能となり、該移動により圧着カム５４と圧着アーム５５側の当接ローラ５５ｂが位置ズレしてこれらの係合が解除されるようになっている。図１１（ａ）はロック機構によりロックされた通常使用状態を、図１１（ｂ）はロック機構を解除して回転軸５３およびこれと同軸の回転軸７３を同時に移動させて上記の係合が解除された状態を示している。図１１の場合、圧着カム５４と圧着アーム５５の当接ローラ５５ｂとが位置ズレしてこれらの係合が解除されることによって圧着アーム５５が図６に示すような離隔位置となり、これに伴って減圧アーム７５も変位して減圧軸７７の回転体７８と減圧カム７４とが離隔して係合が同時に解除される。 In addition, when a lock mechanism (not shown) is released, the rotating shaft 53 of the pressing cam 54 can be moved in the axial direction. is disengaged. FIG. 11(a) shows the state of normal use locked by the locking mechanism, and FIG. 11(b) shows the lock mechanism being released and the rotating shaft 53 and the coaxial rotating shaft 73 being moved at the same time. It shows the released state. In the case of FIG. 11, the pressure cam 54 and the contact roller 55b of the pressure arm 55 are displaced and disengaged, so that the pressure arm 55 is moved to the separated position as shown in FIG. As a result, the decompression arm 75 is also displaced, and the rotor 78 of the decompression shaft 77 and the decompression cam 74 are separated from each other, and the engagement is released at the same time.
たとえば、何らかのトラブルで圧着状態もしくは減圧状態で二次転写装置３０が停止したような場合に、ロック機構を解除して回転軸５３、７３を移動させることで、圧着状態や減圧状態を解除することができ、用紙の取り除きなどを円滑に行うことができる。 For example, when the secondary transfer device 30 is stopped in a press-fit state or a depressurized state due to some trouble, the lock mechanism is released and the rotation shafts 53 and 73 are moved to release the press-fit state or the depressurized state. This makes it possible to smoothly perform operations such as paper removal.
なお、高速減圧部７０についても、回転軸７３の前奥方向の移動がロック機構によって規制された通常使用状態で減圧カム７４と減圧軸７７の回転体７８とが係合し、ロック機構を解除して回転軸７３を前奥方向に移動させると減圧軸７７の回転体７８と減圧カム７４とが位置ズレして係合が解除されるように構成してもよい。たとえば、通常使用状態で減圧カム７４に対応する位置となる部分だけ回転体７８の径を他の部分より太くする等すればよい。 In the high-speed decompression unit 70 as well, the lock mechanism is released when the decompression cam 74 and the rotating body 78 of the decompression shaft 77 engage with each other in the normal use state in which the movement of the rotating shaft 73 in the front-rear direction is restricted by the lock mechanism. Then, when the rotating shaft 73 is moved in the front-to-rear direction, the rotor 78 of the decompression shaft 77 and the decompression cam 74 are displaced from each other and disengaged from each other. For example, the diameter of the rotor 78 may be made thicker than the other portions only in the portion corresponding to the decompression cam 74 in normal use.
以上、本発明の実施の形態を図面によって説明してきたが、具体的な構成は実施の形態に示したものに限られるものではなく、本発明の要旨を逸脱しない範囲における変更や追加があっても本発明に含まれる。 Although the embodiments of the present invention have been described above with reference to the drawings, the specific configurations are not limited to those shown in the embodiments, and modifications and additions may be made without departing from the scope of the present invention. is also included in the present invention.
たとえば、二次転写ローラ４１は、二次転写ユニット４０に組み込まれずともよく、圧着解除部５０は二次転写ローラ４１の軸を押圧するようにしてもよい。 For example, the secondary transfer roller 41 may not be incorporated in the secondary transfer unit 40 , and the pressure releasing section 50 may press the shaft of the secondary transfer roller 41 .
実施の形態では、圧着アーム５５がバネ５６および減圧アーム７５を介して二次転写ユニット４０を押圧し、減圧時に減圧アーム７５でバネ５６を押し戻す構成としたが、たとえば、圧着アーム５５はバネ５６を介して二次転写ユニット４０を押圧し、減圧アーム７５は二次転写ユニット４０の両端等に設けたフックに係合して二次転写ユニット４０に離隔位置へ向かう方向に力を加えるといった構成でもよい。バネ５６の形状は実施の形態に例示したものに限定されず、板バネ等であってもよく、必要な弾性を備える弾性体としてもよい。 In the embodiment, the pressure arm 55 presses the secondary transfer unit 40 via the spring 56 and the pressure reducing arm 75, and the spring 56 is pushed back by the pressure pressure arm 75 when the pressure is reduced. , and the decompression arms 75 are engaged with hooks provided at both ends of the secondary transfer unit 40 to apply force to the secondary transfer unit 40 in the direction toward the separated position. It's okay. The shape of the spring 56 is not limited to those exemplified in the embodiments, and may be a plate spring or the like, or may be an elastic body having necessary elasticity.
１０…画像形成装置
１２…操作パネル
１３…制御回路部
１４…給紙トレイ
１５…定着装置
１６…搬送部
２０…画像形成部
２１…中間転写ベルト
２２…像形成ユニット
２４…感光体ドラム
２６…プリントヘッド
２７…クリーニング装置
２８…対向ローラ
３０…二次転写装置
３２…フレーム部材
３２ａ…底板部
３２ｂ…支持板
３４…ユニット支持軸
３６…支持軸
４０…二次転写ユニット
４１…二次転写ローラ
４２…枠部材
４３…ガイド板
５０…圧着解除部
５２…第１駆動部
５３…回転軸
５４…圧着カム
５５…圧着アーム
５５ａ…回転支点
５５ｂ…当接ローラ
５５ｃ…作用腕
５６…バネ
７０…高速減圧機構
７２…第２駆動部
７３…回転軸
７４…減圧カム
７４ａ…斜面部
７４ｂ…平面部
７５…減圧アーム
７５ａ…押圧部
７５ｂ…減圧アームの減圧動作時の作用点
７５ｃ…回転支点
７５ｄ…減圧アームの力点（減圧軸７７の接続箇所）
７６…位置検知センサ
７７…減圧軸
７８…回転体
Ｄ…二次転写位置
Ａ…中間転写ベルトの周回方向
DESCRIPTION OF SYMBOLS 10... Image forming apparatus 12... Operation panel 13... Control circuit part 14... Paper feed tray 15... Fixing device 16... Conveying part 20... Image forming part 21... Intermediate transfer belt 22... Image forming unit 24... Photoreceptor drum 26... Print Head 27 Cleaning device 28 Counter roller 30 Secondary transfer device 32 Frame member 32a Bottom plate 32b Support plate 34 Unit support shaft 36 Support shaft 40 Secondary transfer unit 41 Secondary transfer roller 42 Frame member 43 Guide plate 50 Crimp releasing part 52 First driving part 53 Rotating shaft 54 Crimp cam 55 Crimp arm 55a Rotational fulcrum 55b Contact roller 55c Acting arm 56 Spring 70 High-speed decompression mechanism 72 Second driving section 73 Rotating shaft 74 Decompression cam 74a Slanted surface 74b Flat surface 75 Decompression arm 75a Pressing section 75b Decompression arm action point during decompression operation 75c Rotation fulcrum 75d Decompression arm Power point (connection point of decompression shaft 77)
76 Position detection sensor 77 Decompression shaft 78 Rotating body D Secondary transfer position A Circulation direction of intermediate transfer belt
Claims (16)
前記二次転写位置で前記中間転写ベルトをその内周面に当接する対向ローラとの間に挟んで押圧する押圧位置と、前記中間転写ベルトの外周面から離隔された離隔位置とに二次転写ローラを変位させる圧着解除機構と、
前記圧着解除機構を駆動する第１駆動部と、
前記押圧位置にされた前記二次転写ローラが前記中間転写ベルトを前記対向ローラとの間に挟んで押圧するニップ圧を、用紙の先端および後端が前記二次転写ローラと前記中間転写ベルトの間を通る際に一時的に減圧する高速減圧機構と、
前記高速減圧機構を駆動する第２駆動部と、
を有すると共に、
前記圧着解除機構および前記高速減圧機構を、前記二次転写ローラの軸方向に投影した場合の投影像が重なるように配置し、
前記圧着解除機構は、前記二次転写ローラの軸と同方向であって前記第１駆動部によって駆動される回転軸に支持された圧着カムと、前記圧着カムに当接して揺動することで前記二次転写ローラを前記押圧位置と前記離隔位置に変位させる圧着アームを有し、
前記高速減圧機構は、前記二次転写ローラの軸と同方向であって前記第２駆動部によって駆動される回転軸に支持された減圧カムと、前記減圧カムに当接して揺動することで前記押圧位置にある前記二次転写ローラの軸を前記ニップ圧が弱まる方向へ変位させる減圧アームを有し、
前記圧着カムと前記減圧カムの前記投影像が重なり、
前記圧着カムの回転軸と、前記減圧カムの回転軸が同軸にされており、
前記圧着アームと前記圧着カムを、前記二次転写ローラの軸方向の両端に分かれた２箇所にそれぞれ設け、これらの内側に前記減圧カムを配置した
ことを特徴とする二次転写装置。 A secondary transfer device that secondarily transfers a toner image that has been primarily transferred onto the outer peripheral surface of an endless annular intermediate transfer belt that is wound around a plurality of rollers and has a predetermined width onto a sheet at a predetermined secondary transfer position. ,
Secondary transfer to a pressing position where the intermediate transfer belt is sandwiched and pressed between an opposing roller that abuts on the inner peripheral surface of the intermediate transfer belt at the secondary transfer position, and a separation position that is separated from the outer peripheral surface of the intermediate transfer belt. a pressure release mechanism that displaces the roller;
a first drive unit that drives the pressure release mechanism;
The nip pressure at which the secondary transfer roller placed in the pressing position presses the intermediate transfer belt between itself and the opposing roller is applied to the leading edge and the trailing edge of the sheet by the pressure between the secondary transfer roller and the intermediate transfer belt. A high-speed decompression mechanism that temporarily decompresses when passing through,
a second drive unit that drives the high-speed decompression mechanism;
and
arranging the pressure release mechanism and the high-speed decompression mechanism so that projected images when projected in the axial direction of the secondary transfer roller overlap;
The pressure release mechanism includes a pressure cam supported by a rotation shaft driven by the first driving section in the same direction as the shaft of the secondary transfer roller, and swinging in contact with the pressure cam. a pressing arm that displaces the secondary transfer roller between the pressing position and the separating position;
The high-speed decompression mechanism includes a decompression cam supported by a rotating shaft driven by the second driving section in the same direction as the shaft of the secondary transfer roller, and swinging in contact with the decompression cam. a decompression arm that displaces the shaft of the secondary transfer roller at the pressing position in a direction in which the nip pressure is weakened;
the projection images of the pressure cam and the decompression cam overlap,
the rotary shaft of the pressure cam and the rotary shaft of the decompression cam are coaxial,
A secondary transfer device according to claim 1, wherein the pressing arm and the pressing cam are provided at two locations separated from each other in the axial direction of the secondary transfer roller, and the decompression cam is disposed inside them.
ことを特徴とする請求項１に記載の二次転写装置。 The secondary transfer device according to claim 1 , wherein the maximum diameter of the pressure cam is smaller than the minimum diameter of the decompression cam.
ことを特徴とする請求項１に記載の二次転写装置。 2. The secondary transfer device according to claim 1 , wherein a minimum diameter of said pressure cam is larger than a maximum diameter of said decompression cam.
前記減圧カムを、前記二次転写ローラの軸方向の中心部に配置し、
前記減圧カムに前記連結部材が当接して前記減圧アームが揺動する
ことを特徴とする請求項１に記載の二次転写装置。 The decompression arms are provided at two locations on both ends of the secondary transfer roller in the axial direction, and the decompression arms are connected to each other by connecting members,
disposing the decompression cam at the center in the axial direction of the secondary transfer roller;
2. The secondary transfer device according to claim 1, wherein the decompression arm swings when the connecting member contacts the decompression cam.
前記圧着カムの内側近傍にそれぞれ前記減圧カムを配置し、
各減圧カムに前記連結部材が当接して前記減圧アームが揺動する
ことを特徴とする請求項１に記載の二次転写装置。 The decompression arms are provided at two locations on both ends of the secondary transfer roller in the axial direction, and the decompression arms are connected to each other by connecting members,
arranging the decompression cams in the vicinity of the inner sides of the crimping cams;
2. The secondary transfer device according to claim 1, wherein the connecting member abuts against each decompression cam so that the decompression arm swings.
該２つの前記減圧カムの内側に、前記第２駆動部および前記減圧カムの角度位置を検出する位置検出手段を配置した
ことを特徴とする請求項１または５に記載の二次転写装置。 arranging the decompression cams in the vicinity of the inner sides of the crimping cams;
6. The secondary transfer device according to claim 1, further comprising position detection means for detecting the angular positions of the second drive section and the decompression cams, inside the two decompression cams.
ことを特徴とする請求項１に記載の二次転写装置。 2. The secondary transfer device according to claim 1 , wherein the decompression arm is a rotating body that abuts on the decompression cam.
ことを特徴とする請求項１に記載の二次転写装置。 A rotational fulcrum of the decompression arm is provided between a force point where the decompression arm receives force from the decompression cam and a point of action where the decompression arm applies force in a direction in which the nip pressure weakens. The secondary transfer device according to claim 1 .
ことを特徴とする請求項８に記載の二次転写装置。 9. The secondary transfer device according to claim 8 , wherein the distance from the rotation fulcrum to the action point is longer than the distance from the force point of the decompression arm to the rotation fulcrum.
ことを特徴とする請求項１に記載の二次転写装置。 wherein the first driving unit and the second driving unit are arranged so that projected images when projected in the axial direction of the secondary transfer roller are superimposed;
2. The secondary transfer device according to claim 1 , wherein:
前記高速減圧機構は、前記減圧アームで前記バネを前記圧着アーム側へ押し戻して前記減圧を行う
ことを特徴とする請求項１に記載の二次転写装置。 the pressing arm presses and moves the secondary transfer roller toward the pressing position via a spring and the decompressing arm in this order;
2. The secondary transfer device according to claim 1 , wherein the high-speed decompression mechanism performs the decompression by pushing the spring back toward the pressure arm with the decompression arm.
減圧を維持する時間の長短に応じて、斜面部と平面部を使い分ける
ことを特徴とする請求項１に記載の二次転写装置。 The decompression cam has a sloped portion and a flat portion on its outer periphery as a region in which a decompressed state is formed,
2. The secondary transfer device according to claim 1 , wherein the sloped portion and the flat portion are selectively used according to the length of time for which the reduced pressure is maintained.
前記圧着解除機構および前記高速減圧機構は、前記二次転写ユニットを変位させる
ことを特徴とする請求項１乃至１２のいずれか１つに記載の二次転写装置。 The secondary transfer roller is provided in a secondary transfer unit,
The secondary transfer device according to any one of claims 1 to 12 , wherein the pressure release mechanism and the high-speed decompression mechanism displace the secondary transfer unit.
ことを特徴とする請求項１３に記載の二次転写装置。 14. The secondary transfer device according to claim 13 , wherein the pressure release mechanism and the high-speed decompression mechanism are provided below the secondary transfer unit.
ことを特徴とする請求項１に記載の二次転写装置。 The secondary according to claim 1, wherein the pressing state is released by moving the pressing cam in the axial direction to release the engagement between the pressing cam and the pressing arm side. transcription device.
ことを特徴とする請求項１に記載の二次転写装置。 2. The secondary transfer according to claim 1, wherein the decompression state is released by moving the decompression cam in the axial direction to release the engagement between the decompression cam and the decompression arm. Device.
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