JP2016095376A

JP2016095376A - Transfer device and image forming apparatus

Info

Publication number: JP2016095376A
Application number: JP2014230908A
Authority: JP
Inventors: 須賀　智昭; Tomoaki Suga; 智昭須賀; 春樹永田; Haruki Nagata
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2014-11-13
Filing date: 2014-11-13
Publication date: 2016-05-26
Anticipated expiration: 2034-11-13
Also published as: CN105607447B; CN105607447A; JP6436383B2

Abstract

PROBLEM TO BE SOLVED: To provide a transfer device that can suppress the occurrence of shock jitter in changing the amount of separation between an image carrier and a contact member between a first interval and a second interval, and an image forming apparatus.SOLUTION: There is provided a transfer device including a contact member that forms a transfer nip sandwiching a recording medium with an image carrier, and contact/separation means having a rotatable cam member that contacts or separates the image carrier from the contact member, where the cam member includes a first peripheral part 401 that is in contact with an opposing member provided on the image carrier side and has the amount of separation between the image carrier and contact member being a first interval, a second peripheral part 402 that is not in contact with the opposing member while the image carrier is in contact with the contact member, and a third peripheral part 403 that is located between the first peripheral part and second peripheral part in a cam member rotation direction, in contact with the opposing member, and has the amount of separation being a second interval smaller than the first interval.SELECTED DRAWING: Figure 1

Description

本発明は、転写装置及び画像形成装置に関するものである。 The present invention relates to a transfer device and an image forming apparatus.

従来、画像形成装置の転写装置として、像担持体とニップ形成部材とで形成した転写ニップに挟み込んだ記録媒体に、像担持体上からトナー像を転写するものが知られている。 2. Description of the Related Art Conventionally, as a transfer device of an image forming apparatus, an apparatus that transfers a toner image from an image carrier onto a recording medium sandwiched between transfer nips formed by an image carrier and a nip forming member is known.

特許文献１に記載の画像形成装置には、前記転写装置として、感光体から中間転写ベルトに一次転写されトナー像を、記録媒体である用紙に二次転写する二次転写装置が設けられている。この二次転写装置は、中間転写ベルトおもて面に接する二次転写ローラと、二次転写ローラと対向し中間転写ベルト裏面に接する二次転写対向ローラとを有する。また、前記二次転写装置は、中間転写ベルトと二次転写ローラとを接離させる回転カムを有する接離機構を備えている。前記回転カムは、高さが異なる２つの凸部と、各凸部の間を繋ぎこれらよりも小径な２つの小径部とを周縁に有しており、二次転写対向ローラと同軸上に設けられている。 The image forming apparatus described in Patent Document 1 includes a secondary transfer device that primarily transfers a toner image, which is primarily transferred from a photosensitive member to an intermediate transfer belt, onto a sheet that is a recording medium, as the transfer device. . The secondary transfer device includes a secondary transfer roller that contacts the front surface of the intermediate transfer belt, and a secondary transfer counter roller that faces the secondary transfer roller and contacts the back surface of the intermediate transfer belt. Further, the secondary transfer device includes a contact / separation mechanism having a rotating cam that contacts and separates the intermediate transfer belt and the secondary transfer roller. The rotating cam has two convex portions having different heights and two small diameter portions connecting the convex portions and having a smaller diameter than these at the periphery, and is provided coaxially with the secondary transfer counter roller. It has been.

前記二次転写装置では、用紙が二次転写ニップへ進入するのに先立って回転カムを駆動し、厚紙では高いほうの凸部を薄紙では低いほうの凸部を二次転写ローラの軸上の空転コロに突き当てて、付勢バネの付勢力に抗して二次転写ローラを押し下げる。これにより、二次転写ローラを中間転写ベルトから離間させ紙厚に応じた所定離間量の隙間を形成し、二次転写ニップへの用紙進入時のショックジターを低減できる。また、用紙の先端を前記隙間に進入させた直後に、回転カムを駆動して小径部を空転コロに対向させる。小径部と空転コロとが対向する状態では、小径部と空転コロとが非接触となるので、付勢バネの付勢力によって二次転写ローラが中間転写ベルトに押し付けられ、二次転写ニップで十分な転写圧を発揮させて転写不良の発生を抑える。また、用紙が二次転写ニップから抜けるときにも、回転カムを駆動し紙厚に応じた凸部を空転コロに突き当てて、中間転写ベルトと二次転写ローラとを離間させ、二次転写ニップを用紙が抜けるときのショックジターを低減できる。 In the secondary transfer device, the rotary cam is driven prior to the sheet entering the secondary transfer nip, and the higher convex portion for the thick paper and the lower convex portion for the thin paper on the axis of the secondary transfer roller. The secondary transfer roller is pushed down against the idling roller against the urging force of the urging spring. As a result, the secondary transfer roller is separated from the intermediate transfer belt to form a gap having a predetermined separation amount corresponding to the paper thickness, and shock jitter at the time of entering the paper into the secondary transfer nip can be reduced. In addition, immediately after the leading edge of the paper enters the gap, the rotary cam is driven so that the small diameter portion faces the idling roller. When the small diameter portion and the idling roller face each other, the small diameter portion and the idling roller are not in contact with each other. Therefore, the secondary transfer roller is pressed against the intermediate transfer belt by the urging force of the urging spring, and the secondary transfer nip is sufficient. To prevent the occurrence of transfer failure by exerting a proper transfer pressure. Also, when the paper comes out of the secondary transfer nip, the rotary cam is driven to abut the convex portion according to the paper thickness against the idling roller, and the intermediate transfer belt and the secondary transfer roller are separated to perform secondary transfer. Shock jitter can be reduced when the paper comes out of the nip.

一般に、複数枚の用紙に連続して画像を形成する連続印刷を行うときには、同じ厚さの用紙だけを用いて連続印刷が行われることが多いが、異なる厚さの用紙を用いて連続印刷を行う場合も有り得る。この場合、先行する用紙と後行する用紙とで厚さが異なるときに、先行する用紙が二次転写ニップを抜けた後、先行する用紙と後行する用紙との紙間領域が二次転写ニップを通過している間に、後行する用紙の厚さに応じた前記離間量に変更することになる。 In general, when performing continuous printing in which images are continuously formed on a plurality of sheets, continuous printing is often performed using only sheets of the same thickness, but continuous printing is performed using sheets of different thicknesses. It is possible to do this. In this case, when the preceding sheet and the following sheet have different thicknesses, the area between the preceding sheet and the following sheet is subjected to the secondary transfer after the preceding sheet passes through the secondary transfer nip. While passing through the nip, the separation amount is changed according to the thickness of the following paper.

しかしながら、前記二次転写装置では、空転コロと高いほうの凸部とが突き当たる姿勢と、空転コロと低いほうの凸部とが突き当たる姿勢とを、回転カムを回転させて変更する途中に小径部と空転コロとが対向する姿勢となる。そのため、二次転写ローラと中間転写ベルトとが離間した状態から二次転写ローラと中間転写ベルトとが一旦接触した後、再度、二次転写ローラと中間転写ベルトとが離間した状態になる。そして、二次転写ローラと中間転写ベルトとが一旦接触したときに、感光体から中間転写ベルトにトナー像の一次転写が行われていると、接触時の衝撃による中間転写ベルトの突発的な速度変動によって、ショックジターが発生してしまう。 However, in the secondary transfer device, the small-diameter portion is changed while the rotating cam is rotated to change the posture in which the idling roller and the higher convex portion abut and the posture in which the idling roller and the lower convex portion abut. And the idling roller face each other. For this reason, after the secondary transfer roller and the intermediate transfer belt are once in contact with each other from the state where the secondary transfer roller and the intermediate transfer belt are separated from each other, the secondary transfer roller and the intermediate transfer belt are again separated from each other. When the secondary transfer roller and the intermediate transfer belt come into contact with each other and the primary transfer of the toner image from the photosensitive member to the intermediate transfer belt is performed, the sudden transfer speed of the intermediate transfer belt due to the impact at the time of contact Shock jitter occurs due to fluctuations.

上記課題を解決するために、本発明は、像担持体との間で記録媒体を挟み込む転写ニップを形成する接触部材と、前記像担持体と前記接触部材とを接離させる回転可能なカム部材を有する接離手段とを備えた転写装置において、前記カム部材は、前記像担持体側に設けられた対向部材と当たり前記像担持体と前記接触部材との離間量が第一間隔となる第一周縁部と、該対向部材と当たらず該像担持体と該接触部材とが接触する第二周縁部と、カム部材回転方向で該第一周縁部と該第二周縁部との間に位置し、該対向部材と当たり該離間量が該第一間隔よりも小さな第二間隔となる第三周縁部とを有することを特徴とする。 In order to solve the above problems, the present invention provides a contact member that forms a transfer nip that sandwiches a recording medium with an image carrier, and a rotatable cam member that contacts and separates the image carrier and the contact member. In the transfer device including the contact / separation means, the cam member comes into contact with a facing member provided on the image carrier side, and a separation amount between the image carrier and the contact member is a first interval. A peripheral edge, a second peripheral edge where the image carrier and the contact member do not come into contact with the opposing member, and a position between the first peripheral edge and the second peripheral edge in the cam member rotation direction; In addition, the counter member and the third peripheral portion having a second distance in which the distance is smaller than the first distance.

以上、本発明によれば、像担持体と接触部材との離間量を第一間隔と第二間隔とで変えるときに、ショックジターが発生するのを抑制できるという優れた効果がある。 As described above, according to the present invention, when the distance between the image carrier and the contact member is changed between the first interval and the second interval, it is possible to suppress the occurrence of shock jitter.

実施形態に係る二次転写ギャップ補正カムのカム線図。FIG. 4 is a cam diagram of a secondary transfer gap correction cam according to the embodiment. 実施形態に係る画像形成装置の正面概略図。1 is a schematic front view of an image forming apparatus according to an embodiment. 実施形態に係る実施例の転写部の正面概略図。The front schematic of the transfer part of the Example which concerns on embodiment. 実施形態に係る実施例の転写部の正面概略図。The front schematic of the transfer part of the Example which concerns on embodiment. 二次転写ニップの周囲構成を示す拡大断面図。FIG. 3 is an enlarged cross-sectional view showing a configuration around a secondary transfer nip. 二次転写ニップの周囲構成を示す斜視図。FIG. 3 is a perspective view showing a configuration around a secondary transfer nip. 実施形態に係る二次転写ギャップ補正カムのカム線図。FIG. 4 is a cam diagram of a secondary transfer gap correction cam according to the embodiment. 実施形態に係る接触動作と離間動作と準備動作とのタイミングチャート。The timing chart of contact operation, separation operation, and preparation operation concerning an embodiment.

図２において、レーザープリンタ等の画像形成装置は、画像情報に基づいて光書込装置１０１より出射された光ビームによって回転駆動する感光体１０２に潜像を形成する。形成された潜像は現像装置１０３によってトナー像に顕像される。多色画像形成装置では主にブラック、マゼンタ、シアン、イエロー色用の感光体１０２によって、それぞれの色のトナー像が形成される。前記各色のトナー像は一次転写装置１０４によって感光体１０２同様に駆動する中間転写ベルト２１上に順次転写され、多色トナー像を中間転写ベルト２１上に形成する。中間転写ベルト２１上の多色トナー像は二次転写装置１０６で、供給搬送装置１０７によって搬送されてきた記録媒体である用紙Ｐに転写される。画像が転写された用紙Ｐは定着装置１０９によって熱定着され排出される。 In FIG. 2, an image forming apparatus such as a laser printer forms a latent image on a photosensitive member 102 that is rotationally driven by a light beam emitted from an optical writing device 101 based on image information. The formed latent image is visualized as a toner image by the developing device 103. In the multicolor image forming apparatus, toner images of respective colors are formed mainly by the photoconductors 102 for black, magenta, cyan, and yellow colors. The toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 21 that is driven in the same manner as the photoconductor 102 by the primary transfer device 104, thereby forming a multicolor toner image on the intermediate transfer belt 21. The multi-color toner image on the intermediate transfer belt 21 is transferred by the secondary transfer device 106 to the paper P that is a recording medium conveyed by the supply conveyance device 107. The sheet P on which the image is transferred is thermally fixed by the fixing device 109 and discharged.

ここで、二次転写装置１０６の二次転写部に用紙Ｐが突入する時に、搬送方向の衝突力や、用紙Ｐの厚みを乗り越える時の反力による衝撃で、中間転写ベルト２１の駆動速度に変動が生じることがある。中間転写ベルト２１の駆動速度に変動があると、一次転写装置１０４では感光体１０２と中間転写ベルト２１との相対速度も変動してしまうため転写ブレが生じて、搬送方向に垂直な横すじ画像となってしまう。駆動速度の変動だけでなく衝撃振動が一次転写装置１０４の一次転写部に伝搬しても、転写ブレや転写率変動が生じて、搬送方向に垂直な横すじ画像となってしまう。二次転写装置１０６の二次転写部から用紙Ｐが抜ける時も、用紙Ｐの厚みがなくなる瞬間の衝撃で、一次転写装置１０４の一次転写部で転写ブレや転写率変動が生じて、搬送方向に垂直な横すじ画像が発生することがある。 Here, when the paper P enters the secondary transfer portion of the secondary transfer device 106, the driving speed of the intermediate transfer belt 21 is increased by the impact of the collision force in the transport direction and the reaction force when the thickness of the paper P is exceeded. Variations may occur. If the drive speed of the intermediate transfer belt 21 varies, the relative speed between the photosensitive member 102 and the intermediate transfer belt 21 also varies in the primary transfer device 104, causing transfer blur and a horizontal stripe image perpendicular to the transport direction. End up. Even if impact vibration propagates to the primary transfer portion of the primary transfer device 104 in addition to fluctuations in drive speed, transfer blur and transfer rate fluctuations occur, resulting in a horizontal stripe image perpendicular to the transport direction. Even when the paper P is removed from the secondary transfer unit of the secondary transfer device 106, transfer shocks and transfer rate fluctuations occur in the primary transfer unit of the primary transfer device 104 due to the impact at the moment when the thickness of the paper P disappears, and the conveyance direction A horizontal stripe image perpendicular to the image may be generated.

図３、図４において、中間転写ベルト２１はベルト形状で二次転写部では弾性体の二次転写対向ローラ２４によって張られている。ローラユニット保持体４０は回転軸４１を中心に回転可能に設けられており、転写圧スプリング４５によって中間転写ベルト２１に押圧されている。ローラユニット保持体４０とともに押圧された二次転写ローラ３０によって二次転写対向ローラ２４は、転写圧スプリング４５の押圧力によって押しつぶされ、二次転写ニップＮを形成する。二次転写ローラ３０と同軸上には、軸方向両端にそれぞれ玉軸受３４と玉軸受３５（図４参照）が設けられており、二次転写対向ローラ２４には玉軸受３４，３５の対向する位置に、二次転写ギャップ補正カム５０，５１が設けられている。 3 and 4, the intermediate transfer belt 21 has a belt shape and is stretched by an elastic secondary transfer counter roller 24 in the secondary transfer portion. The roller unit holder 40 is rotatably provided around a rotation shaft 41 and is pressed against the intermediate transfer belt 21 by a transfer pressure spring 45. The secondary transfer counter roller 24 is crushed by the pressing force of the transfer pressure spring 45 by the secondary transfer roller 30 pressed together with the roller unit holder 40, thereby forming a secondary transfer nip N. On the same axis as the secondary transfer roller 30, ball bearings 34 and ball bearings 35 (see FIG. 4) are provided at both ends in the axial direction, respectively, and the ball bearings 34 and 35 are opposed to the secondary transfer counter roller 24. Secondary transfer gap correction cams 50 and 51 are provided at the positions.

二次転写ギャップ補正カム５０は回転中心から外形までの半径が回転角によって変化する形状となっている。図３に示すように、二次転写ギャップ補正カム５０の半径最小の位置が玉軸受に向いているときには、二次転写ギャップ補正カム５０と玉軸受３４とは離れており、二次転写ローラ３０と中間転写ベルト２１とが所定の押圧力で接触された状態となっている。図４に示すように、二次転写ギャップ補正カム５０の半径が最大の位置が玉軸受３４に向いているときには、二次転写ギャップ補正カム５０が玉軸受３４と接触し、二次転写ローラ３０と中間転写ベルト２１とは離間した状態となる。 The secondary transfer gap correction cam 50 has a shape in which the radius from the rotation center to the outer shape changes depending on the rotation angle. As shown in FIG. 3, when the radius minimum position of the secondary transfer gap correction cam 50 faces the ball bearing, the secondary transfer gap correction cam 50 and the ball bearing 34 are separated from each other, and the secondary transfer roller 30. And the intermediate transfer belt 21 are in contact with each other with a predetermined pressing force. As shown in FIG. 4, when the position where the radius of the secondary transfer gap correction cam 50 is maximum is directed to the ball bearing 34, the secondary transfer gap correction cam 50 comes into contact with the ball bearing 34 and the secondary transfer roller 30. And the intermediate transfer belt 21 are separated from each other.

図５は、二次転写ニップの周囲構成を示す拡大断面図である。また、図６は、二次転写ニップの周囲構成を示す斜視図である。これらの図において、二次転写ローラ３０は、ローラ部３１と、これの軸線方向の両端面からそれぞれ突出して回転軸線方向に延在する軸部材３２，３３と、後述する玉軸受３４，３５とを有している。また、ローラ部３１は、円筒状の中空芯金３１ａと、これの周面に固定された弾性材料からなる弾性層３１ｂと、これの周面に固定された表面層３１ｃとを具備している。 FIG. 5 is an enlarged cross-sectional view showing a configuration around the secondary transfer nip. FIG. 6 is a perspective view showing a configuration around the secondary transfer nip. In these drawings, the secondary transfer roller 30 includes a roller portion 31, shaft members 32 and 33 projecting from both axial end surfaces thereof and extending in the rotational axis direction, and ball bearings 34 and 35 to be described later. have. The roller unit 31 includes a cylindrical hollow core 31a, an elastic layer 31b made of an elastic material fixed to the peripheral surface thereof, and a surface layer 31c fixed to the peripheral surface thereof. .

中空芯金３１ａを構成する金属としては、ステンレス、アルミニウムなどを例示することができるが、これらの材料に限定されるものではない。弾性層３１ｂについては、ＪＩＳ−Ａ硬度で７０［°］以下にすることが望ましい。しかし、ローラ部３１には、クリーニングブレード３９を当接させていることから、弾性層３１ｂが柔らかすぎると様々な不具合を引き起こしてしまう。よって、弾性層３１ｂについては、ＪＩＳ−Ａ硬度で４０［°］以上にすることが望ましい。ある程度の導電性を発揮するエピクロルヒドリンゴムにより、ＪＩＳ−Ａ硬度で５０［°］程度の弾性層３１ｂを形成している。 Examples of the metal constituting the hollow core 31a include stainless steel and aluminum, but are not limited to these materials. The elastic layer 31b is preferably 70 [°] or less in terms of JIS-A hardness. However, since the cleaning blade 39 is in contact with the roller portion 31, various problems are caused if the elastic layer 31b is too soft. Therefore, it is desirable that the elastic layer 31b has a JIS-A hardness of 40 [°] or more. An elastic layer 31b having a JIS-A hardness of about 50 [°] is formed of epichlorohydrin rubber exhibiting a certain degree of conductivity.

導電性を発揮するゴム材料として、前述した導電性のエピクロルヒドリンゴムの代わりに、カーボンを分散せしめたＥＰＤＭやＳｉゴム、イオン導電機能を有するＮＢＲ、ウレタンゴムなどを使用してもよい。ゴム材料の多くがトナーに対して良好な化学的親和性を発揮したり、比較的大きな摩擦係数を発揮したりすることから、ゴムからなる弾性層３１ｂの表面には、表面層３１ｃを被覆している。これにより、ローラ部３１表面に対するトナー付着を抑えたり、ブレードとの摺擦負荷を低減したりしている。表面層３１ｃの材料としては、低摩擦係数で且つ良好なトナー離型性を発揮するフッ素樹脂系樹脂にカーボンやイオン導電剤などの抵抗調整材を含有させたものが好適である。 As a rubber material exhibiting conductivity, EPDM or Si rubber in which carbon is dispersed, NBR having an ionic conductivity function, urethane rubber, or the like may be used instead of the above-described conductive epichlorohydrin rubber. Since many rubber materials exhibit good chemical affinity for the toner or exhibit a relatively large coefficient of friction, the surface of the elastic layer 31b made of rubber is covered with the surface layer 31c. ing. As a result, toner adhesion to the surface of the roller unit 31 is suppressed, and the frictional load with the blade is reduced. As a material for the surface layer 31c, a material in which a resistance adjusting material such as carbon or an ionic conductive agent is contained in a fluororesin resin that exhibits a low coefficient of friction and good toner releasability is suitable.

二次転写ローラ３０は、中間転写ベルト２１と接触しながら回転する際に、ベルトと微小な線速差をもつことがある。この線速差によってベルトをスリップさせないように、表面層３１ｃとしては、摩擦係数を０．３以下に調整している。中間転写ベルト２１については、各色の画像を色ズレなく重ねて転写する狙いから、一定速度で駆動することが求められるため、二次転写ローラ３０の表面層３１ｃの表面摩擦抵抗を低くすることは重要である。 When the secondary transfer roller 30 rotates while being in contact with the intermediate transfer belt 21, it may have a slight linear velocity difference from the belt. The friction coefficient of the surface layer 31c is adjusted to 0.3 or less so that the belt does not slip due to this linear speed difference. The intermediate transfer belt 21 is required to be driven at a constant speed in order to transfer the images of each color in a superimposed manner without color misregistration. Therefore, the surface friction resistance of the surface layer 31c of the secondary transfer roller 30 can be reduced. is important.

二次転写ローラ３０は、二次転写対向ローラ２４に掛け回されている中間転写ベルト２１に向けて付勢されている。中間転写ベルト２１を掛け回している二次転写対向ローラ２４は、円柱状の本体部であるローラ部２４ｂと、ローラ部２４ｂの回転中心箇所に対して回転軸線方向に貫通しつつ、ローラ部２４ｂを自らの表面上で空転させる貫通軸部材２４ａとを有している。貫通軸部材２４ａは、金属からなり、その周面上でローラ部２４ｂを自在に空転させる。本体部としてのローラ部２４ｂは、ドラム状の中空芯金２４ｃと、これの周面上に固定された弾性材料からなる弾性層２４ｄと、中空芯金２４ｃの軸線方向両端にそれぞれ圧入された玉軸受２４ｅとを具備している。玉軸受２４ｅが中空芯金２４ｃを支えながら、中空芯金２４ｃとともに貫通軸部材２４ａ上で回転する。弾性層２４ｄは、中空芯金２４ｃの外周面に圧入されている。 The secondary transfer roller 30 is biased toward the intermediate transfer belt 21 that is wound around the secondary transfer counter roller 24. The secondary transfer counter roller 24 that is wound around the intermediate transfer belt 21 passes through the roller portion 24b, which is a cylindrical main body portion, and the rotation center portion of the roller portion 24b in the rotation axis direction, while passing through the roller portion 24b. And a through shaft member 24a that idles on its surface. The penetrating shaft member 24a is made of metal, and freely rotates the roller portion 24b freely on its peripheral surface. The roller part 24b as the main body part is composed of a drum-shaped hollow cored bar 24c, an elastic layer 24d made of an elastic material fixed on the peripheral surface of the drum-shaped hollow cored bar 24c, and balls press-fitted to both ends in the axial direction of the hollow cored bar 24c. And a bearing 24e. The ball bearing 24e rotates on the penetrating shaft member 24a together with the hollow core bar 24c while supporting the hollow core bar 24c. The elastic layer 24d is press-fitted into the outer peripheral surface of the hollow cored bar 24c.

貫通軸部材２４ａは、中間転写ベルト２１を張架する転写ユニットの側板２８に固定された軸受５２と、側板２９に固定された軸受５３とにより、回転自在に支持されている。但し、プリントジョブ時における殆どの時間は、回転駆動されずに停止している。そして、中間転写ベルト２１の無端移動に伴って連れ回ろうとするローラ部２４ｂを、自らの周面上で自在に空転させる。 The through shaft member 24 a is rotatably supported by a bearing 52 fixed to the side plate 28 of the transfer unit that stretches the intermediate transfer belt 21 and a bearing 53 fixed to the side plate 29. However, most of the time during the print job is stopped without being driven to rotate. Then, the roller portion 24b that is to be rotated along with the endless movement of the intermediate transfer belt 21 is freely idled on its own peripheral surface.

中空芯金２４ｃの周面上に固定された弾性層２４ｄは、７．５［ＬｏｇΩ］以上の抵抗を発揮するように、イオン導電剤の添加によって抵抗値が調整された導電性ゴム材料から構成されている。弾性層２４ｄの電気抵抗を所定の範囲に調整しているのは、次の理由による。すなわち、Ａ５サイズなどといった、ローラ軸線方向のサイズが比較的小さな記録シートを使用する際に、二次転写ニップ内において、記録シートの介在なしにベルトとローラとが直接接触している箇所に転写電流を集中させてしまうのを防止する狙いからである。弾性層２４ｄの電気抵抗を、記録シートの抵抗よりも大きな値にすることで、そのような転写電流の集中を抑えることが可能になる。 The elastic layer 24d fixed on the peripheral surface of the hollow core metal 24c is composed of a conductive rubber material whose resistance value is adjusted by adding an ionic conductive agent so as to exhibit a resistance of 7.5 [LogΩ] or more. Has been. The reason why the electric resistance of the elastic layer 24d is adjusted within a predetermined range is as follows. That is, when using a recording sheet having a relatively small size in the roller axial direction, such as A5 size, transfer is performed in the secondary transfer nip to a portion where the belt and the roller are in direct contact without any recording sheet. This is because the aim is to prevent the current from being concentrated. By setting the electric resistance of the elastic layer 24d to a value larger than the resistance of the recording sheet, it is possible to suppress such transfer current concentration.

また、弾性層２４ｄを構成する導電性ゴム材料としては、Ａｓｋｅｒ−Ｃ硬度で４０［°］程度の弾性を発揮するように、発泡ゴムを用いている。このような発泡ゴムで弾性層２４ｄを構成することで、二次転写ニップ内で弾性層２４ｄを厚み方向に柔軟に変形させて、シート搬送方向にある程度の広さを有する二次転写ニップを形成することができる。 In addition, as the conductive rubber material constituting the elastic layer 24d, foamed rubber is used so as to exhibit elasticity of about 40 [°] in Asker-C hardness. By forming the elastic layer 24d with such foamed rubber, the elastic layer 24d is flexibly deformed in the thickness direction in the secondary transfer nip to form a secondary transfer nip having a certain size in the sheet conveying direction. can do.

なお、本複写機では、既に述べたように、二次転写ローラ３０にクリーニングブレード３９を当接させる都合上、二次転写ローラ３０のローラ部の材料として、弾性に富む材料を使用することが困難である。そこで、二次転写ローラ３０の代わりに、二次転写対向ローラ２４のローラ部２４ｂを弾性変形させるようにしている。 In this copying machine, as described above, for the convenience of bringing the cleaning blade 39 into contact with the secondary transfer roller 30, it is possible to use a material having high elasticity as the material of the roller portion of the secondary transfer roller 30. Have difficulty. Therefore, instead of the secondary transfer roller 30, the roller portion 24b of the secondary transfer counter roller 24 is elastically deformed.

二次転写対向ローラ２４の貫通軸部材２４ａにおいて、長手方向の全領域のうち、ローラ部２４ｂの中に位置していない両端部領域に、二次転写ギャップ補正カム５０，５１を固定して設けている。具体的には、貫通軸部材２４ａの長手方向の一端部領域には、二次転写ギャップ補正カム５０を固定している。二次転写ギャップ補正カム５０は、回転カム部５０ａと、真円形のコロ部５０ｂとを軸線方向に並べて一体形成したものである。コロ部５０ｂに貫通させたネジ８０を貫通軸部材２４ａに螺合させることで、二次転写ギャップ補正カム５０を貫通軸部材２４ａに固定している。また、貫通軸部材２４ａの長手方向の他端部領域には、二次転写ギャップ補正カム５０と同様の構成の二次転写ギャップ補正カム５１を固定している。 In the penetrating shaft member 24a of the secondary transfer counter roller 24, the secondary transfer gap correction cams 50 and 51 are fixedly provided in both end regions that are not located in the roller portion 24b in the entire longitudinal region. ing. Specifically, a secondary transfer gap correction cam 50 is fixed to one end region in the longitudinal direction of the through shaft member 24a. The secondary transfer gap correction cam 50 is formed by integrally forming a rotating cam portion 50a and a true circular roller portion 50b in the axial direction. The secondary transfer gap correction cam 50 is fixed to the penetrating shaft member 24a by screwing the screw 80 penetrating the roller portion 50b into the penetrating shaft member 24a. Further, a secondary transfer gap correction cam 51 having the same configuration as that of the secondary transfer gap correction cam 50 is fixed to the other end portion region in the longitudinal direction of the through shaft member 24a.

貫通軸部材２４ａの軸線方向における二次転写ギャップ補正カム５１よりも外側の領域には、駆動受入ギヤ５４を固定している。また、この駆動受入ギヤ５４の更に外側には、被検知円盤５９を固定している。 A drive receiving gear 54 is fixed to a region outside the secondary transfer gap correction cam 51 in the axial direction of the penetrating shaft member 24a. In addition, a detected disk 59 is fixed on the further outside of the drive receiving gear 54.

一方、転写ユニットの側板２９には、カム駆動モータ５８を固定するとともに、入出力ギヤユニットを回転自在に固定している。入出力ギヤユニットは、カム駆動モータ５８のモータギヤ５７に噛み合って駆動力を受け入れる入力ギヤ部５５と、貫通軸部材２４ａに固定された駆動受入ギヤ５４に対し噛み合って駆動力を伝達する出力ギヤ部５６とを、軸線方向に並べて一体形成したものである。カム駆動モータ５８を駆動することにより、貫通軸部材２４ａを回転させることが可能である。この際、貫通軸部材２４ａを回転させても、ローラ部２４ｂについては貫通軸部材２４ａ上で自在に空転させることが可能であるので、ベルトによるローラ部２４ｂの連れ回りを阻害することはない。 On the other hand, a cam drive motor 58 is fixed to the side plate 29 of the transfer unit, and an input / output gear unit is rotatably fixed. The input / output gear unit meshes with the motor gear 57 of the cam drive motor 58 to receive the driving force, and the output gear unit meshes with the drive receiving gear 54 fixed to the through shaft member 24a to transmit the driving force. 56 are integrally formed side by side in the axial direction. By driving the cam drive motor 58, the through shaft member 24a can be rotated. At this time, even if the through-shaft member 24a is rotated, the roller portion 24b can be freely idled on the through-shaft member 24a, so that the rotation of the roller portion 24b by the belt is not hindered.

貫通軸部材２４ａが所定の回転角度位置で回転を停止させると、二次転写ギャップ補正カム５０及び二次転写ギャップ補正カム５１の凸部が二次転写ローラ３０と突き当たり、二次転写ローラ３０を転写圧スプリング４５の付勢力に抗して押し返す。これにより、二次転写ローラ３０を二次転写対向ローラ２４ひいては中間転写ベルト２１から遠ざける方向に移動させることで、二次転写対向ローラ２４と二次転写ローラ３０との軸間距離を調整する。 When the penetrating shaft member 24a stops rotating at a predetermined rotational angle position, the convex portions of the secondary transfer gap correction cam 50 and the secondary transfer gap correction cam 51 abut against the secondary transfer roller 30 and cause the secondary transfer roller 30 to move. Push back against the urging force of the transfer pressure spring 45. Thus, the distance between the secondary transfer counter roller 24 and the secondary transfer roller 30 is adjusted by moving the secondary transfer roller 30 in a direction away from the secondary transfer counter roller 24 and thus the intermediate transfer belt 21.

かかる構成では、二次転写ギャップ補正カム５０、二次転写ギャップ補正カム５１、カム駆動モータ５８、各種ギヤ、上述したローラユニット保持体などにより、二次転写対向ローラ２４と二次転写ローラ３０との軸間距離を調整する距離調整手段が構成されている。そして、回転可能な支持回転体としての二次転写対向ローラ２４は、その円柱状のローラ部２４ｂに対して貫通せしめた貫通軸部材２４ａ上で、ローラ部２４ｂを自在に空転させる。貫通軸部材２４ａが回転すれば、貫通軸部材２４ａの軸線方向両端部にそれぞれ固定された二次転写ギャップ補正カム５０，５１が一体となって回転する。そのため、貫通軸部材２４ａに駆動を伝達するための駆動伝達機構を軸線方向の一端側に設けるだけで、両端側の回転カムをそれぞれ回転させることが可能である。よって、両端側にそれぞれ駆動伝達機構を設ける必要があった従来に比べて、距離調整手段のレイアウト自由度を向上させることができる。 In such a configuration, the secondary transfer opposing roller 24 and the secondary transfer roller 30 are constituted by the secondary transfer gap correction cam 50, the secondary transfer gap correction cam 51, the cam drive motor 58, various gears, the roller unit holder described above, and the like. A distance adjusting means for adjusting the inter-axis distance is configured. Then, the secondary transfer counter roller 24 as a rotatable support rotating body freely idles the roller portion 24b on the penetrating shaft member 24a passed through the cylindrical roller portion 24b. When the penetrating shaft member 24a rotates, the secondary transfer gap correction cams 50 and 51 fixed to both ends in the axial direction of the penetrating shaft member 24a rotate together. Therefore, it is possible to rotate the rotary cams on both ends only by providing a drive transmission mechanism for transmitting the drive to the penetrating shaft member 24a on one end in the axial direction. Therefore, the layout freedom of the distance adjusting means can be improved as compared with the conventional case where it is necessary to provide drive transmission mechanisms on both ends.

本複写機では、二次転写ローラ３０の中空芯金３１ａを接地している一方で、二次転写対向ローラ２４の中空芯金２４ｃに対してトナーと同極性の二次転写バイアスを印加する。これにより、二次転写ニップ内に、トナーを二次転写対向ローラ２４側から二次転写ローラ３０側に向けて静電移動させる二次転写電界を、両ローラ間に形成する。 In this copying machine, the hollow cored bar 31a of the secondary transfer roller 30 is grounded, while a secondary transfer bias having the same polarity as the toner is applied to the hollow cored bar 24c of the secondary transfer counter roller 24. As a result, a secondary transfer electric field for electrostatically moving the toner from the secondary transfer counter roller 24 side toward the secondary transfer roller 30 side is formed between both rollers in the secondary transfer nip.

二次転写対向ローラ２４の金属製の貫通軸部材２４ａを回転自在に受けている軸受５２は、導電性のすべり軸受けからなる。この導電性の軸受５２には、二次転写バイアスを出力する高圧電源６１が接続されている。高圧電源６１から出力される二次転写バイアスは、導電性の軸受５２を介して二次転写対向ローラ２４に導かれる。そして、二次転写対向ローラ２４内では、金属製の貫通軸部材２４ａと、金属製の玉軸受２４ｅと、金属製の中空芯金２４ｃと、導電性の弾性層２４ｄとを順に伝わっていく。 The bearing 52 that rotatably receives the metal through shaft member 24a of the secondary transfer counter roller 24 is composed of a conductive sliding bearing. A high voltage power supply 61 that outputs a secondary transfer bias is connected to the conductive bearing 52. The secondary transfer bias output from the high-voltage power supply 61 is guided to the secondary transfer counter roller 24 via the conductive bearing 52. In the secondary transfer counter roller 24, a metal penetrating shaft member 24a, a metal ball bearing 24e, a metal hollow cored bar 24c, and a conductive elastic layer 24d are sequentially transmitted.

貫通軸部材２４ａの一端に固定された被検知円盤５９は、貫通軸部材２４ａの回転方向における所定の位置において軸線方向に立ち上がる被検部５９ａを有している。一方、カム駆動モータ５８を支持しているモータブラケットには、光学センサ６０が固定されている。貫通軸部材２４ａが回転する過程において、貫通軸部材２４ａが所定の回転角度位置に位置すると、被検知円盤５９の被検部５９ａが、光学センサ６０の発光素子と受光素子との間に入り込んで両者間の光路を遮断する。光学センサ６０の受光素子は、発光素子からの光を受光すると受光信号を上述の制御部に送信する。制御部は、受光素子からの受光信号が途絶えたタイミングや、そのタイミングからのカム駆動モータ５８の駆動量に基づいて、貫通軸部材２４ａに固定された二次転写ギャップ補正カム５０，５１の凸部の回転角度位置を把握する。 The detected disk 59 fixed to one end of the penetrating shaft member 24a has a test portion 59a that rises in the axial direction at a predetermined position in the rotation direction of the penetrating shaft member 24a. On the other hand, an optical sensor 60 is fixed to the motor bracket that supports the cam drive motor 58. In the process of rotating the through shaft member 24a, when the through shaft member 24a is positioned at a predetermined rotational angle position, the test portion 59a of the detected disk 59 enters between the light emitting element and the light receiving element of the optical sensor 60. The optical path between the two is blocked. When the light receiving element of the optical sensor 60 receives light from the light emitting element, it transmits a light reception signal to the above-described control unit. Based on the timing at which the light receiving signal from the light receiving element is interrupted and the driving amount of the cam drive motor 58 from that timing, the control unit projects the convexities of the secondary transfer gap correction cams 50 and 51 fixed to the through shaft member 24a. The rotation angle position of the part is grasped.

上述したように、二次転写ギャップ補正カム５０，５１は、所定の回転角度位置で二次転写ローラ３０に突き当たって、二次転写ローラ３０を転写圧スプリング４５の付勢力に抗して二次転写対向ローラ２４から遠ざける方向に押し返す。以下、この押し返しを「押し下げ」という。このときの押し返し量（以下、押し下げ量という）は、二次転写ギャップ補正カム５０，５１の凸部の突出量によって決まる。なお、二次転写ローラ３０の押し下げ量が大きくなるほど、二次転写対向ローラ２４と二次転写ローラ３０との軸間距離が大きくなる。 As described above, the secondary transfer gap correction cams 50 and 51 abut against the secondary transfer roller 30 at a predetermined rotational angle position, and the secondary transfer roller 30 resists the urging force of the transfer pressure spring 45 to perform the secondary transfer. Push back in the direction away from the transfer counter roller 24. Hereinafter, this pushing back is referred to as “pressing down”. The amount of pushing back at this time (hereinafter referred to as the amount of pushing down) is determined by the amount of protrusion of the convex portions of the secondary transfer gap correction cams 50 and 51. Note that the greater the amount by which the secondary transfer roller 30 is pushed down, the greater the interaxial distance between the secondary transfer opposing roller 24 and the secondary transfer roller 30.

二次転写ローラ３０において、ローラ部３１と一体になって回転する軸部材３２には、玉軸受３４が空転可能に設けられている。この玉軸受３４は、外径がローラ部３１よりも少し大きなドーナッツ円盤状の形状をしている。そして、それ自体が玉軸受としての機能を有しており、軸部材３２の周面上で空転することができる。二次転写ローラ３０の軸部材３３には、玉軸受３４と同様の構成の玉軸受３５が空転可能に設けられている。 In the secondary transfer roller 30, a ball bearing 34 is provided on the shaft member 32 that rotates integrally with the roller portion 31 so as to be idle. The ball bearing 34 has a donut disk shape whose outer diameter is slightly larger than that of the roller portion 31. And it has a function as a ball bearing itself, and can idle on the peripheral surface of the shaft member 32. A ball bearing 35 having the same configuration as the ball bearing 34 is provided on the shaft member 33 of the secondary transfer roller 30 so as to be idled.

貫通軸部材２４ａの一端側に固定された二次転写ギャップ補正カム５０は、所定の回転角度位置において、バネ付勢方向に二次転写ローラ３０に連動する連動体としての玉軸受３４における被突き当て面に突き当たる。このとき同時に、貫通軸部材２４ａの他端側に固定された二次転写ギャップ補正カム５１が、連動体としての玉軸受３５における被突き当て面に突き当たる。二次転写対向ローラ２４の二次転写ギャップ補正カム５０，５１に突き当てられた玉軸受３４，３５は、その突き当てに伴って回転を阻止されるが、それによって二次転写ローラ３０の回転が妨げられることはない。 The secondary transfer gap correction cam 50 fixed to one end of the penetrating shaft member 24a is struck by a ball bearing 34 as an interlocking body interlocking with the secondary transfer roller 30 in the spring biasing direction at a predetermined rotational angle position. It hits the surface. At the same time, the secondary transfer gap correction cam 51 fixed to the other end side of the penetrating shaft member 24a hits the abutted surface of the ball bearing 35 as the interlocking member. The ball bearings 34 and 35 that are abutted against the secondary transfer gap correction cams 50 and 51 of the secondary transfer counter roller 24 are prevented from rotating along with the abutment, thereby causing the rotation of the secondary transfer roller 30 to rotate. Will not be disturbed.

玉軸受３４，３５が回転を停止しても、二次転写ローラ３０の軸部材３２，３３は、玉軸受３４，３５から独立して自在に回転することができるからである。二次転写ギャップ補正カム５０，５１の突き当てに伴って玉軸受３４，３５の回転を停止させることで、両者の摺擦の発生を回避するとともに、摺擦によるベルト駆動モータや二次転写ローラ３０の駆動モータのトルク上昇の発生を回避することもできる。 This is because even if the ball bearings 34 and 35 stop rotating, the shaft members 32 and 33 of the secondary transfer roller 30 can freely rotate independently of the ball bearings 34 and 35. By stopping the rotation of the ball bearings 34 and 35 in accordance with the abutment of the secondary transfer gap correction cams 50 and 51, the occurrence of friction between them is avoided, and a belt drive motor or secondary transfer roller due to friction is avoided. It is also possible to avoid an increase in the torque of 30 drive motors.

制御部は、次のような強制移動処理を実施するようになっている。すなわち、用紙Ｐの先端を二次転写ニップに進入させる前のタイミングである進入前タイミングで、カム駆動モータ５８の駆動により、二次転写ギャップ補正カム５０，５１を所定の回転角度位置まで回転させる。そして、二次転写ローラ３０を中間転写ベルト２１から遠ざける方向に強制移動させる処理である。この強制移動処理により。二次転写ニップに記録シートを進入させる時に発生してしまう中間転写ベルト２１に対する急激な負荷上昇を抑えて、ショックジターの発生を抑えることができる。なお、進入前タイミングとしては、記録シートをレジストローラ対９５によって二次転写ニップに向けて送り出し始めたタイミングを採用している。 The control unit is configured to perform the following forced movement process. That is, the secondary transfer gap correction cams 50 and 51 are rotated to a predetermined rotational angle position by driving the cam drive motor 58 at a pre-entry timing that is a timing before the leading edge of the paper P enters the secondary transfer nip. . The secondary transfer roller 30 is forcibly moved in a direction away from the intermediate transfer belt 21. By this forced movement process. It is possible to suppress the occurrence of shock jitter by suppressing a sudden load increase on the intermediate transfer belt 21 that occurs when the recording sheet enters the secondary transfer nip. As the pre-entry timing, the timing at which the recording sheet starts to be fed toward the secondary transfer nip by the registration roller pair 95 is employed.

また、制御部は、次のような増圧処理を実施するようになっている。即ち、記録シートの先端を中間転写ベルト２１と二次転写ローラ３０との間に進入させた直後のタイミングである進入直後タイミングで、二次転写ギャップ補正カム５０，５１を、上述した所定の回転角度位置とは異なる回転角度位置まで回転させる。これにより、記録シートに対する転写圧を増大させる処理である。このような増圧処理により、シート進入直後において、進入前タイミングのときよりも転写圧を増大させることで、転写処理中に十分な転写圧を得て、転写不良の発生を抑えることができる。 Moreover, the control part implements the following pressure increase processing. That is, the secondary transfer gap correction cams 50 and 51 are rotated at the predetermined rotation described above at a timing immediately after the leading edge of the recording sheet is immediately after the leading edge of the recording sheet is moved between the intermediate transfer belt 21 and the secondary transfer roller 30. Rotate to a rotational angular position different from the angular position. This is a process for increasing the transfer pressure on the recording sheet. By such a pressure increasing process, the transfer pressure is increased immediately after entering the sheet as compared with the pre-entry timing, so that a sufficient transfer pressure can be obtained during the transfer process and the occurrence of transfer defects can be suppressed.

強制移動処理については、上述した進入前タイミングに加えて、記録シートの後端が中間転写ベルト２１と二次転写ローラ３０との間をすり抜ける直前のタイミングである排出直前タイミングでも実施するようになっている。排出直前タイミングで強制移動処理を実施すると、シート後端がすり抜ける際の中間転写ベルト２１に対する急激な負荷低下を抑えることが可能になるので、その急激な負荷低下に起因する画像濃度ムラの発生を抑えることができる。なお、以下、排出直前タイミングで実施する強制移動処理のことを、特に、減圧処理という。 In addition to the above-described pre-entry timing, the forced movement process is also performed at a timing immediately before discharge, which is a timing immediately before the trailing edge of the recording sheet passes between the intermediate transfer belt 21 and the secondary transfer roller 30. ing. If the forcible movement process is performed at the timing immediately before the discharge, it is possible to suppress a rapid load drop on the intermediate transfer belt 21 when the trailing edge of the sheet slips through, so that occurrence of image density unevenness due to the sudden load drop is prevented. Can be suppressed. Hereinafter, the forced movement process performed at the timing immediately before the discharge is particularly referred to as a decompression process.

図１及び図７に、本実施形態における二次転写ギャップ補正カム５０のカム線図を示す。ここで、二次転写ギャップ補正カム５０の半径が最大で玉軸受３４と接触し二次転写ギャップＧの量が最大となる位置を第一停留位置４０１とした。また、二次転写ギャップ補正カム５０の半径が最小で二次転写ニップＮの圧力が最大となる位置を第二停留位置４０２とした。また、第一停留位置４０１と第二停留位置４０２とは、第一傾斜部４１１によって滑らかにつながる形状とした。第一停留位置４０１から第一傾斜部４１１とは逆側に向う第二傾斜部４１２は、第一傾斜部４１１よりも傾斜勾配を小さくした（緩やかにした）。また、第二傾斜部４１２の途中に第三停留位置４０３を設定した。 1 and 7 are cam diagrams of the secondary transfer gap correction cam 50 in the present embodiment. Here, the position where the radius of the secondary transfer gap correction cam 50 is the maximum and is in contact with the ball bearing 34 and the amount of the secondary transfer gap G is the maximum is defined as the first stop position 401. A position where the radius of the secondary transfer gap correction cam 50 is minimum and the pressure of the secondary transfer nip N is maximum is set as a second stop position 402. In addition, the first stop position 401 and the second stop position 402 have a shape that is smoothly connected by the first inclined portion 411. The second inclined portion 412 facing from the first stop position 401 to the opposite side of the first inclined portion 411 has a smaller inclined slope than the first inclined portion 411. A third stop position 403 is set in the middle of the second inclined portion 412.

第一停留位置４０１での転写ギャップ量は、搬送される用紙Ｐの最大の厚みよりも大きく設定している。そして、用紙Ｐが二次転写部に突入する瞬間には、用紙Ｐの厚みよりも０．１［ｍｍ］ほど広めの転写ギャップ量になるように、第一停留位置４０１からの回転開始タイミングを調整している。用紙Ｐが二次転写部に突入してから、画像が二次転写部に進入するまでの数ミリ秒の間に、二次転写ギャップ補正カム５０が第一傾斜部４１１を介して第二停留位置４０２に回転移動し、画像の転写に必要な転写圧となるニップ状態を得る第一接触動作を用意した。 The transfer gap amount at the first stop position 401 is set to be larger than the maximum thickness of the sheet P to be conveyed. Then, at the moment when the paper P enters the secondary transfer portion, the rotation start timing from the first stop position 401 is set so that the transfer gap amount is 0.1 mm larger than the thickness of the paper P. It is adjusted. The secondary transfer gap correction cam 50 is stopped by the second inclined portion 411 through the first inclined portion 411 during a few milliseconds from when the sheet P enters the secondary transfer portion until the image enters the secondary transfer portion. A first contact operation for rotating to the position 402 and obtaining a nip state that provides a transfer pressure necessary for image transfer was prepared.

用紙Ｐが厚ければ、転写ギャップ量がゼロになるときの衝撃力を用紙Ｐが吸収するが、用紙Ｐが薄い場合には前記衝撃力を用紙Ｐで吸収しにくくなる。そのため、二次転写部で発生した衝撃が、中間転写ベルト２１を伝って一次転写装置１０４の位置まで伝搬し、感光体１０２から中間転写ベルト２１に転写される画像が伸び縮みする。その結果、中間転写ベルト２１から用紙Ｐに転写された画像に、用紙搬送方向と垂直な横すじ画像が発生してしまう。 If the sheet P is thick, the sheet P absorbs an impact force when the transfer gap amount becomes zero. However, if the sheet P is thin, the sheet P hardly absorbs the impact force. For this reason, the impact generated in the secondary transfer portion propagates through the intermediate transfer belt 21 to the position of the primary transfer device 104, and the image transferred from the photosensitive member 102 to the intermediate transfer belt 21 expands and contracts. As a result, a horizontal streak image perpendicular to the paper conveyance direction is generated in the image transferred from the intermediate transfer belt 21 to the paper P.

一方で、用紙Ｐが薄い場合には、第一停留位置４０１での転写ギャップ量よりも狭いギャップ量で用紙Ｐを二次転写部に突入させても問題とならない。また、用紙Ｐが二次転写部に突入する時の転写ギャップ量が狭ければ、ギャップ量を狭くする速度を緩やかにしても画像が二次転写部に進入するまでに、転写に必要なニップ状態まで移動できる。そのため、本実施形態では用紙Ｐが薄い場合に、二次転写ギャップ補正カム５０を第二傾斜部４１２を通る回転方向で動作するようにした。 On the other hand, when the paper P is thin, there is no problem even if the paper P enters the secondary transfer portion with a gap amount narrower than the transfer gap amount at the first stop position 401. In addition, if the transfer gap amount when the sheet P enters the secondary transfer portion is narrow, the nip necessary for transfer before the image enters the secondary transfer portion even if the speed of narrowing the gap amount is reduced. You can move to the state. Therefore, in this embodiment, when the paper P is thin, the secondary transfer gap correction cam 50 is operated in the rotational direction passing through the second inclined portion 412.

しかし、この場合には、第一停留位置４０１から二次転写ギャップ補正カム５０の回転を開始すると、用紙Ｐが二次転写ニップに突入するまでの時間を必要としてしまい、先行する用紙Ｐと後続の用紙Ｐとの隙間を広くする必要が生じる。そこで、二次転写ギャップ補正カム５０の第二傾斜部４１２の途中に第三停留位置４０３を設け、第二傾斜部４１２を通過する回転動作のときには、第三停留位置４０３から二次転写ギャップ補正カム５０の回転を開始するようにした。そして、第三停留位置４０３から第二傾斜部４１２を介して第二停留位置４０２に二次転写ギャップ補正カム５０が回転し、画像の転写に必要な転写圧となるニップ状態を得る第二接触動作を用意した。 However, in this case, when the rotation of the secondary transfer gap correction cam 50 is started from the first stop position 401, it takes time until the sheet P enters the secondary transfer nip, and the preceding sheet P and the succeeding sheet P follow. It is necessary to widen the gap with the paper P. Therefore, the third stop position 403 is provided in the middle of the second inclined portion 412 of the secondary transfer gap correction cam 50, and the secondary transfer gap correction is performed from the third stop position 403 during the rotation operation passing through the second inclined portion 412. The rotation of the cam 50 is started. Then, the secondary transfer gap correction cam 50 rotates from the third stop position 403 to the second stop position 402 via the second inclined portion 412 to obtain a nip state that provides a transfer pressure necessary for image transfer. Prepared the action.

本実施形態の画像形成装置においては、用紙Ｐの種類によって第一接触動作と第二接触動作とを選択可能としており、厚みが厚い用紙Ｐでは第一接触動作を行い、厚みが薄い用紙Ｐでは第二接触動作を行うように設定している。なお、この設定は、使用者も容易に変更可能であり、使用者の好みに合わせて選択可能である。例えば、用紙Ｐとしてコート紙を用いる場合、紙のコシが強いためショックジターが発生し易いことから、用紙Ｐが二次転写部に突入するときには第三停留位置４０３とし第二接触動作を行う。 In the image forming apparatus according to the present embodiment, the first contact operation and the second contact operation can be selected depending on the type of the paper P, the first contact operation is performed on the thick paper P, and the thin paper P is selected. The second contact operation is set to be performed. This setting can be easily changed by the user and can be selected according to the user's preference. For example, when coated paper is used as the paper P, the paper is stiff, and shock jitter is likely to occur. Therefore, when the paper P enters the secondary transfer portion, the second stop operation is performed at the third stop position 403.

また、二次転写ギャップ補正カム５０の第一停留位置または第三停留位置からの回転開始タイミングも調整可能としており、第一接触動作または第二接触動作の中でも、様々な用紙Ｐの厚みに対応して適切なギャップ量を設定できるようにしている。用紙Ｐが薄くなるほど回転開始タイミングを早くすれば、図１における用紙突入の位置が第一停留位置４０１または第三停留位置４０３から遠ざかるので、用紙Ｐが二次転写部に突入する時にはギャップ量を用紙Ｐが薄くなった分、狭く設定できる。この設定は、使用者も容易に変更可能であり、用紙Ｐの保管環境や製造ばらつきなどによって、同じ種類の用紙Ｐでも厚みが変わったときなどに、使用者の好みに合わせて調整可能としている。さらに、この設定は、用紙Ｐの種類ごとに設定できるようにし、同じ種類の用紙Ｐでは同じ動作をするように設定できるようにしている。 In addition, the rotation start timing of the secondary transfer gap correction cam 50 from the first stop position or the third stop position can also be adjusted, and it can cope with various thicknesses of the paper P in the first contact operation or the second contact operation. Thus, an appropriate gap amount can be set. If the rotation start timing is advanced as the paper P becomes thinner, the paper entry position in FIG. 1 moves away from the first stop position 401 or the third stop position 403. Therefore, when the paper P enters the secondary transfer portion, the gap amount is set. As the paper P becomes thinner, it can be set narrower. This setting can be easily changed by the user, and can be adjusted to the user's preference when the thickness of the same type of paper P changes due to the storage environment of the paper P or manufacturing variations. . Further, this setting can be set for each type of paper P, and can be set to perform the same operation on the same type of paper P.

用紙Ｐが二次転写部から抜けるときには、第二停留位置４０２から第一傾斜部４１１を通って第一停留位置４０１に二次転写ギャップ補正カム５０を回転移動させる第一離間動作を行う。また、用紙Ｐが薄い場合には、第二停留位置４０２から第二傾斜部４１２を通って第三停留位置４０３に二次転写ギャップ補正カム５０を回転移動させる第二離間動作を行うようにしている。 When the paper P is removed from the secondary transfer portion, a first separation operation is performed in which the secondary transfer gap correction cam 50 is rotationally moved from the second stop position 402 to the first stop position 401 through the first inclined portion 411. When the paper P is thin, a second separation operation is performed in which the secondary transfer gap correction cam 50 is rotationally moved from the second stop position 402 to the third stop position 403 through the second inclined portion 412. Yes.

接触動作同様に、用紙Ｐの種類によって第一離間動作と第二離間動作とを選択可能としており、厚みが厚い用紙Ｐでは第一離間動作を行い、厚みが薄い用紙Ｐでは第二離間動作を行うように設定している。なお、この設定は、使用者も容易に変更可能であり、使用者の好みに合わせて選択可能である。また、二次転写ギャップ補正カム５０の第二停留位置からの回転開始タイミングも調整可能としており、第一離間動作または第二離間動作の中でも、様々な用紙Ｐの厚みに対応して適切なギャップ量を設定できるようにしている。用紙Ｐが薄くなるほど回転開始タイミングを遅くすれば、図７における用紙抜けの位置が第二停留位置４０２に近づくので、用紙Ｐが二次転写部を抜ける時にはギャップ量は用紙Ｐが薄くなった分、狭く設定できる。この設定は、使用者も容易に変更可能であり、用紙Ｐの保管環境や製造ばらつきなどによって、同じ種類の用紙Ｐでも厚みが変わったときなどに、使用者の好みに合わせて調整可能としている。さらに、この設定は、用紙Ｐの種類ごとに設定できるようにし、同じ種類の用紙Ｐでは同じ動作をするように設定できるようにしている。 Similar to the contact operation, the first separation operation and the second separation operation can be selected depending on the type of the paper P, the first separation operation is performed on the thick paper P, and the second separation operation is performed on the thin paper P. Set to do. This setting can be easily changed by the user and can be selected according to the user's preference. Further, the rotation start timing of the secondary transfer gap correction cam 50 from the second stop position can also be adjusted, and an appropriate gap corresponding to the thickness of various sheets P can be obtained during the first separation operation or the second separation operation. The amount can be set. If the rotation start timing is delayed as the paper P becomes thinner, the paper removal position in FIG. 7 approaches the second stop position 402. Therefore, when the paper P passes through the secondary transfer portion, the gap amount is the amount that the paper P becomes thinner. Can be set narrowly. This setting can be easily changed by the user, and can be adjusted to the user's preference when the thickness of the same type of paper P changes due to the storage environment of the paper P or manufacturing variations. . Further, this setting can be set for each type of paper P, and can be set to perform the same operation on the same type of paper P.

また、本実施形態では、図８に示すタイミングチャートにあるように、用紙Ｐが二次転写部から抜けてから、次の連続して供給搬送される用紙Ｐが二次転写ニップに突入するまでに、第一準備動作か第二準備動作を実行することができる。第一準備動作は、第一停留位置４０１から第二傾斜部４１２を介して第三停留位置４０３に、二次転写ギャップ補正カム５０を回転移動させる動作である。第二準備動作は、第三停留位置４０３から第二傾斜部４１２を介して第一停留位置４０１に二次転写ギャップ補正カム５０を回転移動させる動作である。これにより、用紙Ｐの種類が交互に供給搬送される動作においても、用紙Ｐの種類ごとに最適な接触動作と離間動作とを設定することができる。また、第一停留位置４０１と第三停留位置４０３との２つの停留位置を往来するにあたって、少なくとも第三停留位置４０３のギャップ量よりもギャップ量が狭くなることはない。そのため、連続して搬送される用紙Ｐと用紙Ｐとの間での動作によって、中間転写ベルト２１に加わる余計な外力で生じる横すじ画像を起こさずに、前述した準備動作を実行することができる。 Further, in the present embodiment, as shown in the timing chart shown in FIG. 8, from the time when the paper P is removed from the secondary transfer unit, until the next paper P to be continuously fed and fed enters the secondary transfer nip. In addition, the first preparation operation or the second preparation operation can be executed. The first preparation operation is an operation of rotating the secondary transfer gap correction cam 50 from the first stop position 401 to the third stop position 403 via the second inclined portion 412. The second preparatory operation is an operation of rotating the secondary transfer gap correction cam 50 from the third stop position 403 to the first stop position 401 via the second inclined portion 412. Thereby, even in the operation in which the types of the paper P are alternately supplied and conveyed, it is possible to set the optimum contact operation and separation operation for each type of the paper P. Further, when the two stop positions of the first stop position 401 and the third stop position 403 are moved, the gap amount is not narrower than at least the gap amount of the third stop position 403. Therefore, the above-described preparation operation can be executed without causing a horizontal streak image generated by an extra external force applied to the intermediate transfer belt 21 due to the operation between the paper P and the paper P that are continuously conveyed. .

以上に説明したものは一例であり、本発明は、次の態様毎に特有の効果を奏する。
（態様Ａ）
中間転写ベルト２１などの像担持体との間で用紙Ｐなどの記録媒体を挟み込む転写ニップを形成する二次転写ローラ３０などの接触部材と、像担持体と接触部材とを接離させる回転可能な二次転写ギャップ補正カム５０などのカム部材と当該カム部材と対向する玉軸受３４などの対向部材とを有する接離手段とを備えた二次転写装置１０６などの転写装置において、カム部材は、像担持体側に設けられた対向部材と当たり像担持体と接触部材との離間量が第一間隔となる第一停留位置４０１などの第一周縁部と、対向部材と当たらず像担持体と接触部材とが接触する第二停留位置４０２などの第二周縁部と、カム部材回転方向で第一周縁部と第二周縁部との間に位置し、対向部材と当たり離間量が第一間隔よりも小さな第二間隔となる第三停留位置４０３などの第三周縁部とを有する。
（態様Ａ）においては、対向部材と第二周縁部とが対向する姿勢をとることなく、対向部材と第一周縁部とが対向する姿勢と、対向部材と第三周縁部とが対向する姿勢との間でカム部材の姿勢を変更することが可能である。これにより、離間した状態の像担持体と接触部材とを一旦接触させることなく、像担持体と接触部材との離間量を、第一間隔から第二間隔または第二間隔から第一間隔へ切り換えることができる。よって、像担持体と接触部材との離間量を第一間隔と第二間隔とで切り換えるときに、像担持体と接触部材とが接触することで生じる衝撃による像担持体の突発的な速度変動によって、ショックジターが発生してしまうのを抑制することができる。
（態様Ｂ）
（態様Ａ）において、前記カム部材は正逆転可能であり、前記カム部材の周縁に、前記第一周縁部と第二周縁部とをつなぐ第一傾斜部４１１などの第一傾斜部と、前記第一周縁部に対してカム部材回転方向で第一傾斜部側とは反対側に位置し第一周縁部と第二周縁部とをつなぎ第一傾斜部よりも傾斜勾配が小さい第二傾斜部４１２などの第二傾斜部とを有しており、第二傾斜部の途中に前記第三周縁部を設けた。これによれば、上記実施形態について説明したように、簡単な制御と１つの凸部で、複数のギャップ量の停留状態と、複数のギャップ速度を設定できるので、安価、かつ短期間で転写部のギャップ制御を最適化した転写装置を得ることができる。
（態様Ｃ）
（態様Ｂ）において、記録媒体が前記転写ニップに突入するタイミングに合わせて、前記第一周縁部から前記第一傾斜部を介して前記第二周縁部に前記カム部材が回転し、前記像担持体と前記接触部材とで記録媒体を挟み込む第一接触動作と、前記第三周縁部から前記第二傾斜部を介して前記第二周縁部に前記カム部材が回転し、前記像担持体と前記接触部材とで記録媒体を挟み込む第二接触動作とを有する。これによれば、上記実施形態について説明したように、記録媒体が転写ニップに突入する時に、二種類の接触動作から最適動作を選択することができる。
（態様Ｄ）
（態様Ｃ）において、前記第一接触動作と前記第二接触動作とが、記録媒体の種類に応じて選択可能である。これによれば、上記実施形態について説明したように、記録媒体の種類に応じて、二種類の接触動作から最適な動作を選択することができる。
（態様Ｅ）
（態様Ｂ）、（態様Ｃ）または（態様Ｄ）において、記録媒体が前記転写ニップから抜けるタイミングに合わせて、前記第二周縁部から前記第一傾斜部を介して前記第一周縁部に前記カム部材が回転し、前記像担持体と前記接触部材とが離間する第一離間動作と、前記第二周縁部から前記第二傾斜部を介して前記第三周縁部に前記カム部材が回転し、前記像担持体と前記接触部材とが離間する第二離間動作とを有する。これによれば、上記実施形態について説明したように、記録媒体が転写ニップから抜ける時に、二種類の離間動作から最適動作を選択することができる。
（態様Ｆ）
（態様Ｅ）において、前記第一離間動作と前記第二離間動作とが、記録媒体の種類に応じて選択可能である。これによれば、上記実施形態について説明したように、記録媒体の種類に応じて、二種類の離間動作から最適な動作を選択することができる。
（態様Ｇ）
（態様Ｂ）、（態様Ｃ）、（態様Ｄ）、（態様Ｅ）または（態様Ｆ）において、記録媒体が前記転写ニップから抜けてから、次に連続して供給搬送される記録媒体が前記転写ニップに突入するタイミングまでに、前記第一周縁部から前記第二傾斜部を介して前記第三周縁部に前記カム部材を回転する第一準備動作と、前記第三周縁部から前記第二傾斜部を介して前記第一周縁部に前記カム部材を回転する第二準備動作とを有する。これによれば、上記実施形態について説明したように、不必要にギャップ量を狭めることなく、記録媒体が転写ニップから抜ける時の周縁部と、突入する時の周縁部を異なる周縁部に設定することができる。
（態様Ｈ）
（態様Ｂ）、（態様Ｃ）、（態様Ｄ）、（態様Ｅ）、（態様Ｆ）または（態様Ｇ）において、前記第一周縁部または第三周縁部からの第一カム回転開始タイミングが、記録媒体が前記転写ニップに突入するタイミングに対して選択可変である。これによれば、上記実施形態について説明したように、様々な記録媒体の厚みやコシなどに応じて、接触動作における記録媒体の突入時ギャップ量を最適なギャップ量に調整することができる。
（態様Ｉ）
（態様Ｈ）において、前記カム回転開始タイミングが、記録媒体の種類に応じて選択可変である。これによれば、上記実施形態について説明したように、記録媒体の種類ごとに、接触動作における記録媒体の突入時ギャップ量を最適なギャップ量に調整することができる。
（態様Ｊ）
（態様Ｂ）、（態様Ｃ）、（態様Ｄ）、（態様Ｅ）、（態様Ｆ）、（態様Ｇ）、（態様Ｈ）または（態様Ｉ）において、前記第二周縁部からの第二カム回転開始タイミングが、記録媒体が前記転写ニップから抜けるタイミングに対して選択可変である。これによれば、上記実施形態について説明したように、様々な記録媒体の厚みやコシなどに応じて、離間動作における記録媒体の抜け時ギャップ量を最適なギャップ量に調整することができる。
（態様Ｋ）
（態様Ｊ）において、前記第二カム回転開始タイミングが、記録媒体の種類に応じて選択可変である。これによれば、上記実施形態について説明したように、記録媒体の種類ごとに、離間動作における記録媒体の抜け時ギャップ量を最適なギャップ量に調整することができる。
（態様Ｌ）
像担持体との間で記録媒体を挟み込む転写ニップを形成する接触部材と、前記像担持体と前記接触部材とを接離させる回転可能なカム部材を有する接離手段とを備えた転写装置において、前記カム部材は、正逆転可能であり、像担持体側に設けられた対向部材と当たり前記像担持体と前記接触部材との離間量が第一間隔となる第一周縁部と、対向部材と当たらず像担持体と接触部材とが接触する第二周縁部と、カム部材回転方向で第一周縁部と第二周縁部との間に位置し、対向部材と当たり離間量が第一間隔よりも小さな第二間隔となる第三周縁部と、対向部材と当たりカム部材回転方向で第一周縁部と第三周縁部とを、像担持体と接触部材とを接触させない周面で繋ぐ第四周縁部とを有する。これによれば、上記実施形態について説明したように、像担持体と接触部材との離間量を第一間隔と第二間隔とで変えるときに、ショックジターが発生するのを抑制できる。
（態様Ｍ）
像担持体の表面に形成した画像を、転写手段を用いて記録媒体へ転写することにより記録媒体上に画像を形成する画像形成装置において、前記転写手段として、（態様Ａ）、（態様Ｂ）、（態様Ｃ）、（態様Ｄ）、（態様Ｅ）、（態様Ｆ）、（態様Ｇ）、（態様Ｈ）、（態様Ｉ）、（態様Ｊ）、（態様Ｋ）または（態様Ｌ）に記載の転写装置を用いる。これによれば、上記実施形態について説明したように、記録媒体の転写部の突入や抜けの衝撃による画像乱れが発生しない画像形成装置を得ることができる。 What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A contact member such as a secondary transfer roller 30 that forms a transfer nip for sandwiching a recording medium such as paper P between the image carrier such as the intermediate transfer belt 21 and the image carrier and the contact member are rotatable. In a transfer device such as a secondary transfer device 106 having a cam member such as a secondary transfer gap correction cam 50 and a contacting / separating means having a facing member such as a ball bearing 34 facing the cam member, A first peripheral edge portion such as a first stop position 401 where the distance between the facing member provided on the image carrier side and the contact image carrier and the contact member is a first interval; It is located between the second peripheral edge such as the second stop position 402 where the contact member comes into contact and the first peripheral edge and the second peripheral edge in the cam member rotation direction. Third stop with a smaller second interval And a third peripheral unit such as position 403.
In (Aspect A), without facing the facing member and the second peripheral edge, the facing member and the first peripheral edge are opposed to each other, and the facing member and the third peripheral edge are opposed to each other. It is possible to change the posture of the cam member. As a result, the distance between the image carrier and the contact member is switched from the first interval to the second interval or from the second interval to the first interval without once bringing the image carrier and the contact member in contact with each other into contact with each other. be able to. Therefore, when the amount of separation between the image carrier and the contact member is switched between the first interval and the second interval, sudden speed fluctuation of the image carrier due to an impact caused by contact between the image carrier and the contact member Therefore, it is possible to suppress the occurrence of shock jitter.
(Aspect B)
In (Aspect A), the cam member is capable of forward and reverse rotation, and a first inclined portion such as a first inclined portion 411 that connects the first peripheral portion and the second peripheral portion to the periphery of the cam member; A second inclined portion that is located on the opposite side of the first inclined portion in the cam member rotation direction with respect to the first peripheral portion, connects the first peripheral portion and the second peripheral portion, and has a smaller inclination gradient than the first inclined portion. 412 and the like, and the third peripheral edge portion is provided in the middle of the second inclined portion. According to this, as described in the above embodiment, since a plurality of gap amounts can be set and a plurality of gap speeds can be set with simple control and a single convex portion, the transfer portion can be inexpensively and in a short period of time. A transfer device with optimized gap control can be obtained.
(Aspect C)
In (Aspect B), the cam member rotates from the first peripheral edge portion to the second peripheral edge portion through the first inclined portion in accordance with the timing when the recording medium enters the transfer nip, and the image carrier A first contact operation for sandwiching a recording medium between the body and the contact member, and the cam member is rotated from the third peripheral portion to the second peripheral portion via the second inclined portion, and the image carrier and the And a second contact operation of sandwiching the recording medium with the contact member. According to this, as described in the above embodiment, the optimum operation can be selected from the two types of contact operations when the recording medium enters the transfer nip.
(Aspect D)
In (Aspect C), the first contact operation and the second contact operation can be selected according to the type of the recording medium. According to this, as described in the above embodiment, an optimum operation can be selected from two types of contact operations according to the type of the recording medium.
(Aspect E)
In (Aspect B), (Aspect C), or (Aspect D), the recording medium is moved from the second peripheral edge portion to the first peripheral edge portion via the first inclined portion in accordance with the timing of removal from the transfer nip. When the cam member rotates and the image carrier and the contact member are separated from each other, the cam member rotates from the second peripheral portion to the third peripheral portion via the second inclined portion. And a second separating operation for separating the image carrier and the contact member. According to this, as described in the above embodiment, when the recording medium comes out of the transfer nip, the optimum operation can be selected from two types of separation operations.
(Aspect F)
In (Aspect E), the first separation operation and the second separation operation can be selected according to the type of the recording medium. According to this, as described in the above embodiment, the optimum operation can be selected from the two types of separation operations according to the type of the recording medium.
(Aspect G)
In (Aspect B), (Aspect C), (Aspect D), (Aspect E), or (Aspect F), the recording medium that is continuously fed and transported after the recording medium leaves the transfer nip is A first preparatory operation for rotating the cam member from the first peripheral edge portion to the third peripheral edge portion via the second inclined portion by the time of entering the transfer nip, and from the third peripheral edge portion to the second And a second preparatory operation for rotating the cam member on the first peripheral edge via an inclined portion. According to this, as described in the above embodiment, the peripheral edge when the recording medium comes out of the transfer nip and the peripheral edge when entering the recording medium are set to different peripheral edges without unnecessarily narrowing the gap amount. be able to.
(Aspect H)
In (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F) or (Aspect G), the first cam rotation start timing from the first peripheral edge or the third peripheral edge is The recording medium can be selected and varied with respect to the timing at which the recording medium enters the transfer nip. According to this, as described in the above embodiment, the amount of gap at the time of entry of the recording medium in the contact operation can be adjusted to an optimum gap amount according to the thickness and stiffness of various recording media.
(Aspect I)
In (Aspect H), the cam rotation start timing is variable in accordance with the type of the recording medium. According to this, as described in the above embodiment, the gap amount at the time of entry of the recording medium in the contact operation can be adjusted to an optimum gap amount for each type of recording medium.
(Aspect J)
In (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F), (Aspect G), (Aspect H) or (Aspect I), the second from the second peripheral portion. The cam rotation start timing is selectively variable with respect to the timing at which the recording medium comes out of the transfer nip. According to this, as described in the above embodiment, the gap amount when the recording medium is detached in the separation operation can be adjusted to the optimum gap amount according to the thickness and stiffness of various recording media.
(Aspect K)
In (Aspect J), the second cam rotation start timing is selectable according to the type of the recording medium. According to this, as described in the above embodiment, the gap amount when the recording medium is detached in the separation operation can be adjusted to the optimum gap amount for each type of recording medium.
(Aspect L)
A transfer apparatus comprising: a contact member that forms a transfer nip that sandwiches a recording medium with an image carrier; and contact / separation means having a rotatable cam member that makes the image carrier and the contact member contact and separate. The cam member is capable of forward and reverse rotation, a counter member provided on the side of the image carrier, a first peripheral portion where a distance between the image carrier and the contact member is a first interval, a counter member, Positioned between the first peripheral edge and the second peripheral edge in the cam member rotation direction, the contact member and the image carrier and the contact member not contacting each other, and the opposing member and the contact separation amount from the first interval The fourth peripheral edge connecting the first peripheral edge and the third peripheral edge in the rotational direction of the cam member and the opposing member with a peripheral surface that does not contact the image carrier and the contact member. And a peripheral portion. According to this, as described in the above embodiment, it is possible to suppress the occurrence of shock jitter when the distance between the image carrier and the contact member is changed between the first interval and the second interval.
(Aspect M)
In an image forming apparatus that forms an image on a recording medium by transferring an image formed on the surface of the image carrier onto the recording medium using a transfer unit, the transfer unit includes (Aspect A) and (Aspect B). (Aspect C), (Aspect D), (Aspect E), (Aspect F), (Aspect G), (Aspect H), (Aspect I), (Aspect J), (Aspect K) or (Aspect L) Is used. According to this, as described in the above embodiment, it is possible to obtain an image forming apparatus that does not cause image disturbance due to the impact of the entry or removal of the transfer portion of the recording medium.

２１中間転写ベルト
２４二次転写対向ローラ
２４ａ貫通軸部材
２４ｂローラ部
２４ｃ中空芯金
２４ｄ弾性層
２８側板
２９側板
３０二次転写ローラ
３１ローラ部
３１ａ中空芯金
３１ｂ弾性層
３１ｃ表面層
３２軸部材
３３軸部材
３４玉軸受
３５玉軸受
３９クリーニングブレード
４０ローラユニット保持体
４１回転軸
４５転写圧スプリング
５０二次転写ギャップ補正カム
５０ａ回転カム部
５０ｂコロ部
５１二次転写ギャップ補正カム
５２軸受
５３軸受
５４駆動受入ギヤ
５５入力ギヤ部
５６出力ギヤ部
５７モータギヤ
５８カム駆動モータ
５９被検知円盤
５９ａ被検部
６０光学センサ
６１高圧電源
８０ネジ
９５レジストローラ対
１０１光書込装置
１０２感光体
１０３現像装置
１０４一次転写装置
１０６二次転写装置
１０７供給搬送装置
１０９定着装置
４０１第一停留位置
４０２第二停留位置
４０３第三停留位置
４１１第一傾斜部
４１２第二傾斜部 21 Intermediate transfer belt 24 Secondary transfer counter roller 24a Through shaft member 24b Roller portion 24c Hollow core metal 24d Elastic layer 28 Side plate 29 Side plate 30 Secondary transfer roller 31 Roller portion 31a Hollow core metal 31b Elastic layer 31c Surface layer 32 Shaft member 33 Shaft member 34 Ball bearing 35 Ball bearing 39 Cleaning blade 40 Roller unit holder 41 Rotating shaft 45 Transfer pressure spring 50 Secondary transfer gap correction cam 50a Rotating cam portion 50b Roller portion 51 Secondary transfer gap correction cam 52 Bearing 53 Bearing 54 Drive Receiving gear 55 Input gear portion 56 Output gear portion 57 Motor gear 58 Cam drive motor 59 Detected disk 59a Detected portion 60 Optical sensor 61 High voltage power supply 80 Screw 95 Registration roller pair 101 Optical writing device 102 Photoconductor 103 Developing device 104 Primary transfer Location 106 secondary transfer device 107 supplies transport device 109 fixing device 401 first station positions 402 second dwell position 403 the third stopping position 411 first inclined portion 412 second inclined portion

特開２０１０−２０４２５９号公報JP 2010-204259 A

Claims

A contact member that forms a transfer nip that sandwiches the recording medium with the image carrier;
In a transfer apparatus comprising a contacting / separating means having a rotatable cam member that contacts and separates the image carrier and the contact member,
The cam member comes into contact with a counter member provided on the image carrier side, a first peripheral edge where the distance between the image carrier and the contact member is a first interval, and the cam member does not hit the counter member. A second peripheral edge where the body and the contact member are in contact with each other and the first peripheral edge and the second peripheral edge in the cam member rotating direction, and the contact member and the second peripheral edge are in contact with each other. A transfer apparatus comprising a third peripheral edge portion having a second interval smaller than the interval.

The transfer device according to claim 1,
The cam member can be rotated forward and backward,
A first inclined portion connecting the first peripheral edge portion and the second peripheral edge portion to the periphery of the cam member; and on the opposite side to the first inclined portion side in the cam member rotation direction with respect to the first peripheral edge portion. A second inclined portion that is positioned and connects the first peripheral portion and the second peripheral portion and has a smaller inclination than the first inclined portion, and the third peripheral portion is located in the middle of the second inclined portion. A transfer device comprising a portion.

The transfer device according to claim 2,
In accordance with the timing when the recording medium enters the transfer nip,
A first contact operation in which the cam member rotates from the first peripheral portion to the second peripheral portion via the first inclined portion, and the recording medium is sandwiched between the image carrier and the contact member;
The cam member rotates from the third peripheral edge portion to the second peripheral edge portion via the second inclined portion, and has a second contact operation of sandwiching a recording medium between the image carrier and the contact member. Characteristic transfer device.

The transfer device according to claim 3, wherein
The transfer device, wherein the first contact operation and the second contact operation can be selected according to the type of recording medium.

The transfer device according to claim 2, 3 or 4,
In accordance with the timing when the recording medium comes out of the transfer nip,
A first separating operation in which the cam member rotates from the second peripheral portion to the first peripheral portion via the first inclined portion, and the image carrier and the contact member are separated from each other;
The cam member rotates from the second peripheral portion to the third peripheral portion via the second inclined portion, and has a second separating operation in which the image carrier and the contact member are separated from each other. Transfer device.

The transfer device according to claim 5, wherein
The transfer device, wherein the first separation operation and the second separation operation can be selected according to the type of the recording medium.

The transfer apparatus according to claim 2, 3, 4, 5 or 6.
After the recording medium exits from the transfer nip, until the timing when the recording medium continuously fed and conveyed next enters the transfer nip.
A first preparatory operation for rotating the cam member from the first peripheral edge to the third peripheral edge via the second inclined part;
And a second preparatory operation for rotating the cam member from the third peripheral portion to the first peripheral portion via the second inclined portion.

The transfer device according to claim 2, 3, 4, 5, 6 or 7,
The transfer device, wherein the first cam rotation start timing from the first peripheral portion or the third peripheral portion is selectively variable with respect to the timing at which the recording medium enters the transfer nip.

The transfer device according to claim 8, wherein
2. A transfer apparatus according to claim 1, wherein the cam rotation start timing is selectable and variable according to the type of recording medium.

The transfer apparatus according to claim 2, 3, 4, 5, 6, 7, 8, or 9.
2. A transfer apparatus according to claim 1, wherein the second cam rotation start timing from the second peripheral edge portion is selectively variable with respect to the timing at which the recording medium comes out of the transfer nip.

The transfer device according to claim 10, wherein
The transfer device, wherein the second cam rotation start timing is selectable and variable according to the type of the recording medium.

A contact member that forms a transfer nip that sandwiches the recording medium with the image carrier;
In a transfer apparatus comprising a contacting / separating means having a rotatable cam member that contacts and separates the image carrier and the contact member,
The cam member is capable of forward and reverse rotation, a counter member provided on the image carrier side, a first peripheral portion where a distance between the image carrier and the contact member is a first interval, and the counter member And the second peripheral edge where the image carrier and the contact member contact each other, and is positioned between the first peripheral edge and the second peripheral edge in the cam member rotation direction, A third peripheral edge having a second distance that is smaller than the first distance, a counter member and the cam member rotating direction, the first peripheral edge and the third peripheral edge, and the image carrier. A transfer device comprising: a fourth peripheral edge portion connected by a peripheral surface that does not contact the contact member.

In an image forming apparatus for forming an image on a recording medium by transferring the image formed on the surface of the image carrier to the recording medium using a transfer unit,
13. An image forming apparatus using the transfer device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 as the transfer unit.