JP2001296760A - Color image forming device - Google Patents

Color image forming device

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Publication number
JP2001296760A
JP2001296760A JP2000113760A JP2000113760A JP2001296760A JP 2001296760 A JP2001296760 A JP 2001296760A JP 2000113760 A JP2000113760 A JP 2000113760A JP 2000113760 A JP2000113760 A JP 2000113760A JP 2001296760 A JP2001296760 A JP 2001296760A
Authority
JP
Japan
Prior art keywords
intermediate transfer
transfer belt
image forming
photosensitive drum
roller
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP2000113760A
Other languages
Japanese (ja)
Other versions
JP4395981B2 (en
Inventor
Kazunori Kanekura
和紀 金倉
Yuzo Kawano
裕三 川野
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Panasonic Holdings Corp
Original Assignee
Matsushita Electric Industrial Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
Priority to JP2000113760A priority Critical patent/JP4395981B2/en
Publication of JP2001296760A publication Critical patent/JP2001296760A/en
Application granted granted Critical
Publication of JP4395981B2 publication Critical patent/JP4395981B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Color Electrophotography (AREA)

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device capable of excellently transferring a toner image to an intermediate transfer belt without requiring an elevator roller by optimizing the array of primary transfer rollers. SOLUTION: This device is equipped with plural primary transfer rollers 10a, 10b, 10c and 10d arranged in the loop of the intermediate transfer belt 7 and moved up and down so as to respectively press the belt 7 toward photoreceptor drums 2a to 5a side. The rollers 10a to 10d are set in such a way that the rollers 10a to 10d are positionally deviated from the drums 2a to 5a so as not to form a nip between the rollers 10a to 10d and the corresponding drums 2a to 5a and two rollers 10a and 10d are arranged to include the group of the array of the drums 2a to 5a and drive the belt 7 to come into contact with the drums 2a to 5a by its elevating action.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【0001】[0001]

【発明の属する技術分野】本発明は、中間転写ベルトを
介して用紙にカラー画像を転写する構成としたカラー画
像形成装置に関する。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus configured to transfer a color image to a sheet via an intermediate transfer belt.

【0002】[0002]

【従来の技術】画像のカラー化に伴って、一連の画像形
成プロセスが展開される像担持体を複数備えておき、シ
アン像、マゼンタ像、イエロー像、好ましくはブラック
像の各色像をそれぞれの像担持体に形成し、各像担持体
の転写位置にてシート材に各色像を重ね合わせて転写す
ることによりフルカラー画像を形成するタンデム方式の
画像形成装置も従来から数多く提案されている。
2. Description of the Related Art A plurality of image carriers on which a series of image forming processes are developed in accordance with colorization of an image are provided, and each color image of a cyan image, a magenta image, a yellow image, and preferably a black image is formed. Many tandem-type image forming apparatuses that form a full-color image by forming images on an image carrier and superimposing and transferring each color image onto a sheet material at a transfer position of each image carrier have been proposed.

【0003】このようなタンデム方式のカラー画像形成
装置は、たとえば本願出願人が先に提案して出願した特
願平11−88768号や特願平11−9298号に記
載されているように、一列上に配列したイエロー,マゼ
ンタ,シアン,ブラックのトナー画像形成ユニットに沿
って走行する閉ループの中間転写ベルトを備えたもので
ある。そして、この中間転写ベルトに各画像形成装置に
感光体ドラム上のトナー像を転写し、このトナー像を用
紙に転写した後に定着器によって定着させるというのが
基本的な構成である。図4(a)は昇降ローラを備える
従来の技術の要部の概略図であって、一次転写ローラ及
び昇降ローラが下降しているときの概略図、(b)は昇
降ローラを備える従来の技術の要部の概略図であって、
一次転写ローラ及び昇降ローラが上昇して中間転写ベル
トを感光体ベルトに接触させているときの概略図を示
す。
Such a tandem type color image forming apparatus is disclosed in, for example, Japanese Patent Application Nos. 11-88768 and 11-9298 filed by the present applicant. It is provided with a closed-loop intermediate transfer belt that runs along the yellow, magenta, cyan, and black toner image forming units arranged in a line. The basic configuration is such that a toner image on a photosensitive drum is transferred to each image forming apparatus on the intermediate transfer belt, and the toner image is transferred onto a sheet and then fixed by a fixing device. FIG. 4A is a schematic view of a main part of a conventional technique provided with an elevating roller, and is a schematic view when a primary transfer roller and an elevating roller are lowered, and FIG. FIG.
FIG. 4 is a schematic diagram when the primary transfer roller and the elevating roller are raised to bring the intermediate transfer belt into contact with the photosensitive belt.

【0004】図4において、中間転写ベルト51は駆動
ローラ52と被動ローラ53との間に巻回され、各色の
画像形成ユニットの感光体ドラム54a,54b,54
c,54dに対応させた近傍の位置には、転写のための
バックアップとして一次転写ローラ55a,55b,5
5c,55dを中間転写ベルト51のループ内で上下に
移動可能に配置している。一方、中間転写ベルト51に
担持されたトナー像を用紙に転写するため、中間転写ベ
ルト51のループ内に被動ローラ53とともに用紙を押
し付けてニップして中間転写ベルト51上のトナー像を
用紙に転写するための押圧ローラ(図示せず)が配置さ
れる。更に、中間転写ベルト51のループ内には、トナ
ー像転写の際に中間転写ベルト51に適切な張力を与え
るためのテンションローラ56が配置される。
In FIG. 4, an intermediate transfer belt 51 is wound between a driving roller 52 and a driven roller 53, and the photosensitive drums 54a, 54b, 54 of the image forming units of each color.
The primary transfer rollers 55a, 55b, and 5 are provided as backups for transfer at positions near the positions corresponding to c and d.
5c and 55d are arranged so as to be able to move up and down within the loop of the intermediate transfer belt 51. On the other hand, in order to transfer the toner image carried on the intermediate transfer belt 51 to the sheet, the sheet is pressed and nipped with the driven roller 53 into the loop of the intermediate transfer belt 51 to transfer the toner image on the intermediate transfer belt 51 to the sheet. A pressing roller (not shown) is provided for the operation. Further, in the loop of the intermediate transfer belt 51, a tension roller 56 for applying an appropriate tension to the intermediate transfer belt 51 when transferring the toner image is arranged.

【0005】印字されない期間では、一次転写ローラ5
5a〜55dは同図の(a)に示す下降位置にあり、テ
ンションローラ56による中間転写ベルト51に対する
テンション付与もない。一方、印字モードになると、テ
ンションローラ56の移動によって中間転写ベルト51
にテンションが付与された後、一次転写ローラ55a〜
55bが上昇し、中間転写ベルト51を感光体ドラム5
4a〜54dに接触させる。
In a period in which no printing is performed, the primary transfer roller 5
5a to 55d are at the lowered position shown in FIG. 7A, and there is no tension applied to the intermediate transfer belt 51 by the tension roller 56. On the other hand, in the print mode, the movement of the tension roller 56 causes the intermediate transfer belt 51 to move.
After the tension is applied to the primary transfer rollers 55a to 55a,
55b rises, and the intermediate transfer belt 51 is moved to the photosensitive drum 5
4a to 54d.

【0006】ここで、一次転写ローラ55a〜55dの
軸の周りにスポンジ等の弾性体を設けたものでは、感光
体ドラム54a〜54dの真下に配置しても中間転写ベ
ルト51を適正にニップできるので、中間転写ベルト5
1へのトナー像の転写も最適に行なわれる。これに対
し、コストダウンのために一次転写ローラ55a〜55
dを金属の丸棒とした場合では、感光体ドラム54a〜
54dの周面も硬いため、両方の軸線位置と姿勢を高精
度で配置しないと中間転写ベルト51のニップ不良を生
じる。そこで、図示のように、感光体ドラム54a〜5
4dに対して一次転写ローラ55a〜55dを少し中間
転写ベルト51の走行方向の下流側にずらし、同図
(b)のように中間転写ベルト51の弾性を利用して感
光体ドラム54a〜54dに接触させることが有効とな
る。すなわち、感光体ドラム54a〜54dと一次転写
ローラ55a〜55dとによるニップではなく、中間転
写ベルト51を一次転写ローラ55a〜55dで上に突
き上げ、これにより弾性的に中間転写ベルト51を感光
体ドラム54a〜54dに接触させることができる。し
たがって、一次転写ローラ55a〜55dをコストが安
い金属の丸棒のものとしても良好なトナー像の転写が可
能となる。
Here, if an elastic body such as a sponge is provided around the axis of the primary transfer rollers 55a to 55d, the intermediate transfer belt 51 can be properly nipped even if it is disposed immediately below the photosensitive drums 54a to 54d. So the intermediate transfer belt 5
The transfer of the toner image to No. 1 is also performed optimally. On the other hand, the primary transfer rollers 55a to 55
When d is a metal round bar, the photosensitive drums 54a to 54a
Since the peripheral surface of 54d is also hard, unless the two axial positions and postures are arranged with high precision, a nip defect of the intermediate transfer belt 51 occurs. Therefore, as shown in FIG.
The primary transfer rollers 55a to 55d are slightly shifted to the downstream side in the running direction of the intermediate transfer belt 51 with respect to the photosensitive drums 54a to 54d by using the elasticity of the intermediate transfer belt 51 as shown in FIG. Contacting is effective. That is, the intermediate transfer belt 51 is pushed up by the primary transfer rollers 55a to 55d, not elastically by the nip of the photosensitive drums 54a to 54d and the primary transfer rollers 55a to 55d. 54a to 54d. Therefore, even if the primary transfer rollers 55a to 55d are made of a low-cost metal round bar, it is possible to transfer a good toner image.

【0007】[0007]

【発明が解決しようとする課題】ところが、左端の感光
体ドラム54aに対応する一次転写ローラ55aは右側
に偏っているので、この一次転写ローラ55aが上昇し
ても中間転写ベルト51を感光体ドラム54aに接触さ
せる力は不安定となる。このため、一次転写ローラ55
aと同時に上下動作する昇降ローラ57を備え、同図の
(b)のように感光体ドラム54aに対してこの昇降ロ
ーラ57による押し付けを利用して、中間転写ベルト5
1を感光体ドラム54aに安定させて接触させることが
必要となる。
However, since the primary transfer roller 55a corresponding to the photosensitive drum 54a at the left end is skewed to the right, even if the primary transfer roller 55a is raised, the intermediate transfer belt 51 is moved to the photosensitive drum. The force of contact with 54a becomes unstable. For this reason, the primary transfer roller 55
a lifting roller 57 that moves up and down simultaneously with the intermediate transfer belt 5 using the pressing by the lifting roller 57 against the photosensitive drum 54a as shown in FIG.
1 needs to be stably brought into contact with the photosensitive drum 54a.

【0008】このように、従来では金属棒を用いた一次
転写ローラ55a〜55dを用いる場合、これらの一次
転写ローラ55a〜55dを感光体ドラム54a〜54
dとずらした配置としなければならず、中間転写ベルト
51へのトナー像の転写を補償するめに昇降ローラ57
を付帯する必要がある。このため、昇降ローラ57だけ
でなくその昇降駆動機構を別に備えることになり、部品
点数が増加するほか中間転写ベルト51も長くなってし
まい、コスト面での障害が大きい。
As described above, conventionally, when the primary transfer rollers 55a to 55d using a metal rod are used, these primary transfer rollers 55a to 55d are connected to the photosensitive drums 54a to 54d.
d, and the lifting roller 57 is used to compensate for the transfer of the toner image to the intermediate transfer belt 51.
Must be attached. For this reason, not only the elevating roller 57 but also the elevating drive mechanism are separately provided, so that the number of components increases and the intermediate transfer belt 51 becomes longer, which is a great obstacle in terms of cost.

【0009】本発明は、一次転写ローラの配列を最適化
することによって、昇降ローラを必要とせず良好な中間
転写ベルトへのトナー像の転写ができるカラー画像形成
装置を提供することを目的とする。
SUMMARY OF THE INVENTION It is an object of the present invention to provide a color image forming apparatus which can transfer a toner image onto an intermediate transfer belt without the need for an elevating roller by optimizing the arrangement of primary transfer rollers. .

【0010】[0010]

【課題を解決するための手段】本発明は、トナー像を担
持する感光体ドラムを含んで複数配列されそれぞれトナ
ー色の異なる画像を形成する画像形成ユニットと、前記
感光体ドラムに接触可能に配置され前記トナー像が転写
されるエンドレスの中間転写ベルトと、前記中間転写ベ
ルトのループ内に配置され前記感光体ドラムと所定の電
位差を有し前記感光体ドラム上の前記トナー像を前記中
間転写ベルトに転写させる複数の一次転写ローラと、前
記中間転写ベルトのループ内に配置され当該中間転写ベ
ルト上のトナー像を記録媒体に転写する二次転写ローラ
とを備えたタンデム方式のカラー画像形成装置におい
て、前記一次ローラの上昇動作のみによって前記中間転
写ベルトを前記感光体ドラムに接触可能としたことを特
徴とする。
According to the present invention, there is provided an image forming unit which includes a plurality of photosensitive drums for carrying a toner image and forms images having different toner colors, and is arranged so as to be capable of contacting the photosensitive drum. And an endless intermediate transfer belt to which the toner image is transferred, and the intermediate transfer belt, which is disposed in a loop of the intermediate transfer belt and has a predetermined potential difference from the photosensitive drum and has a predetermined potential difference. Tandem-type color image forming apparatus, comprising: a plurality of primary transfer rollers for transferring a toner image onto a recording medium; and a plurality of primary transfer rollers for transferring the toner image on the intermediate transfer belt to a recording medium. The intermediate transfer belt can be brought into contact with the photosensitive drum only by the raising operation of the primary roller.

【0011】本発明によれば、一次転写ローラの配列を
最適化することによって、昇降ローラを必要とせず良好
な中間転写ベルトへのトナー像の転写ができるカラー画
像形成装置を得ることができる。
According to the present invention, by optimizing the arrangement of the primary transfer rollers, it is possible to obtain a color image forming apparatus capable of transferring a toner image onto an intermediate transfer belt without requiring a lifting roller.

【0012】[0012]

【発明の実施の形態】請求項1に記載の発明は、トナー
像を担持する感光体ドラムを含んで複数配列されそれぞ
れトナー色の異なる画像を形成する画像形成ユニット
と、感光体ドラムに接触可能に配置されトナー像が転写
されるエンドレスの中間転写ベルトと、中間転写ベルト
のループ内に配置され感光体ドラムと所定の電位差を有
し感光体ドラム上のトナー像を中間転写ベルトに転写さ
せる複数の一次転写ローラと、中間転写ベルトのループ
内に配置され当該中間転写ベルト上のトナー像を記録媒
体に転写する二次転写ローラとを備えたタンデム方式の
カラー画像形成装置において、一次ローラの上昇動作の
みによって中間転写ベルトを感光体ドラムに接触可能と
したことを特徴とするカラー画像形成装置であり、昇降
ローラによる中間転写ベルトの押し上げが不要となり、
部品点数を削減し中間転写ベルトの長さを短縮できると
いう作用を有する。
According to the first aspect of the present invention, there is provided an image forming unit which includes a plurality of photosensitive drums carrying a toner image and which forms images having different toner colors, and is capable of contacting the photosensitive drum. And an endless intermediate transfer belt to which the toner image is transferred, and a plurality of transfer rollers which are arranged in a loop of the intermediate transfer belt and have a predetermined potential difference from the photosensitive drum and transfer the toner image on the photosensitive drum to the intermediate transfer belt. In a tandem-type color image forming apparatus including a primary transfer roller, and a secondary transfer roller disposed in a loop of the intermediate transfer belt and transferring a toner image on the intermediate transfer belt to a recording medium, the primary roller is raised. A color image forming apparatus characterized in that the intermediate transfer belt can be brought into contact with the photosensitive drum only by an operation, The push-up of the belt is not required,
This has the effect of reducing the number of components and shortening the length of the intermediate transfer belt.

【0013】請求項2に記載の発明は、中間転写ベルト
の移動方向最上流にある感光体ドラムに対向した一次転
写ローラを感光体ドラムに対し上流側に、中間転写ベル
トの移動方向最下流にある感光体ドラムに対向した一次
転写ローラを感光体ドラムに対し下流側に配置したこと
を特徴とする請求項1記載のカラー画像形成装置であ
り、感光体ドラムの外側に一次転写ローラを配置するこ
とで感光体ドラムと中間転写ベルトとの間の安定した接
触が維持でき、感光体ドラムから中間転写ベルトへの良
好なトナー像の転写ができるという作用を有する。
According to a second aspect of the present invention, the primary transfer roller facing the photosensitive drum which is the most upstream in the moving direction of the intermediate transfer belt is located upstream of the photosensitive drum and the most downstream in the moving direction of the intermediate transfer belt. 2. The color image forming apparatus according to claim 1, wherein a primary transfer roller facing a certain photosensitive drum is disposed downstream of the photosensitive drum. Thereby, stable contact between the photosensitive drum and the intermediate transfer belt can be maintained, and an effect that a good toner image can be transferred from the photosensitive drum to the intermediate transfer belt can be obtained.

【0014】請求項3に記載の発明は、一次転写ローラ
の配列数を感光体ドラムの配列数よりも少なくしたこと
を特徴とする請求項1記載のカラー画像形成装置であ
り、一次転写ローラの本数が少なくなるので低価格化が
図れるという作用を有する。
According to a third aspect of the present invention, in the color image forming apparatus according to the first aspect, the number of primary transfer rollers is smaller than the number of photosensitive drums. Since the number is reduced, the price can be reduced.

【0015】請求項4に記載の発明は、感光体ドラムの
配列数が4個で、一次転写ローラを中間転写ベルトの移
動方向最上流にある感光体ドラムの上流側、感光体ドラ
ムの配列の2個目と3個目の中間、中間転写ベルトの移
動方向最下流にある感光体ドラムの下流側の3個配列す
ることを特徴とする請求項3記載のカラー画像形成装置
であり、4個の感光体ドラムに対し感光体ドラムの数よ
り少ない3個の一次転写ローラで感光体ドラムと一次転
写ローラの距離をそれぞれ同じにすることができ、感光
体ドラムと中間転写ベルトとを安定して接触維持できる
ので、部品点数の削減と同時に、良好な感光体ドラムか
ら中間転写ベルトへのトナー像の転写ができるという作
用を有する。
According to a fourth aspect of the present invention, the number of photosensitive drums arranged is four, and the primary transfer roller is arranged upstream of the photosensitive drum located at the uppermost stream in the moving direction of the intermediate transfer belt. 4. The color image forming apparatus according to claim 3, wherein three photosensitive drums are arranged on the downstream side in the moving direction of the intermediate transfer belt between the second and third intermediate transfer belts. The distance between the photosensitive drum and the primary transfer roller can be made the same with three primary transfer rollers, which is smaller than the number of photosensitive drums, with respect to the photosensitive drum. Since the contact can be maintained, the toner image can be transferred from the photosensitive drum to the intermediate transfer belt satisfactorily while reducing the number of components.

【0016】請求項5に記載の発明は、画像形成ユニッ
トをそれぞれイエロー,マゼンタ,シアン,ブラックの
4色のトナー画像形成用として配列し、一次転写ローラ
と、イエローの画像形成ユニットの感光体ドラムの上流
側との相対位置のみが、他の画像形成ユニットの相対位
置と異なることを特徴とする請求項2記載のカラー画像
形成装置であり、転写条件の異なる色を人間にとって最
も認識性の低いイエローとすることで、目視による画像
品質の低下を最小限にできるとともに、一次転写ローラ
の本数を少なくできるので低価格化が図れるという作用
を有する。
According to a fifth aspect of the present invention, the image forming units are arranged for forming toner images of four colors of yellow, magenta, cyan, and black, respectively, and a primary transfer roller and a photosensitive drum of the yellow image forming unit are arranged. 3. The color image forming apparatus according to claim 2, wherein only the relative position with respect to the upstream side of the image forming unit is different from the relative position of the other image forming units. By using yellow, it is possible to minimize the deterioration of image quality by visual observation, and to reduce the number of primary transfer rollers, so that the price can be reduced.

【0017】以下、本発明の実施の形態を図面に基づい
て説明する。
An embodiment of the present invention will be described below with reference to the drawings.

【0018】図1は本発明の一実施の形態によるカラー
画像形成装置の要部の構成を示す概略縦断面図である。
FIG. 1 is a schematic longitudinal sectional view showing the structure of a main part of a color image forming apparatus according to an embodiment of the present invention.

【0019】図1において、カラー画像形成装置の本体
1内にイエロー(Y),マゼンタ(M),シアン
(C),ブラック(K)の各色のトナー像をそれぞれ形
成するための画像形成ユニット2,3,4,5が順に配
置され、これらの画像形成ユニット2〜5のそれぞれに
対応して露光器6a,6b,6c,6dを備えている。
画像形成ユニット2〜5は、露光器6a〜6dからのレ
ーザビームの照射によってその周面に静電潜像を形成す
る像担持体としての感光体ドラム2a,3a,4a,5
aと、トナータンクから供給されるトナーを感光体ドラ
ム2a〜5aに付着させて静電潜像をトナー像として顕
像化する現像ローラ2b,3b,4b,5b等を備えた
ものである。
In FIG. 1, an image forming unit 2 for forming toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K) in a main body 1 of a color image forming apparatus. , 3, 4, and 5 are arranged in order, and are provided with exposure units 6a, 6b, 6c, and 6d corresponding to the image forming units 2 to 5, respectively.
The image forming units 2 to 5 are photosensitive drums 2 a, 3 a, 4 a, 5 serving as image carriers that form an electrostatic latent image on a peripheral surface thereof by irradiation of laser beams from the exposure units 6 a to 6 d.
a, and developing rollers 2b, 3b, 4b, 5b, etc. for adhering the toner supplied from the toner tank to the photosensitive drums 2a to 5a to visualize the electrostatic latent image as a toner image.

【0020】配列された画像形成ユニット2〜5の下側
には中間転写ベルト7が矢印方向に走行可能に配置され
ている。この中間転写ベルト7は、駆動ローラ8,テン
ションローラ9、各感光体ドラム2a〜5aに対応させ
て配置した4個の一次転写ローラ10a,10b,10
c,10dと、用紙に転写するための二次転写ローラ1
1を巡って矢印方向に周回駆動される。
Below the arranged image forming units 2 to 5, an intermediate transfer belt 7 is arranged so as to be able to run in the direction of the arrow. The intermediate transfer belt 7 includes a drive roller 8, a tension roller 9, and four primary transfer rollers 10a, 10b, 10 arranged corresponding to the respective photosensitive drums 2a to 5a.
c, 10d, and a secondary transfer roller 1 for transferring to paper
1 is driven to rotate in the direction of the arrow.

【0021】中間転写ベルト7の下側には用紙トレイ1
2が配置され、この用紙トレイ12から繰り出される用
紙Pは二次転写ローラ11と対向して配置した押圧ロー
ラ13との間にニップされ、中間転写ベルト7に形成さ
れたカラー画像が用紙Pに転写される。そして、用紙P
は定着器14に供給されてトナー像を定着した後に排紙
される。
A sheet tray 1 is provided below the intermediate transfer belt 7.
2, the paper P fed out from the paper tray 12 is nipped between the secondary transfer roller 11 and a pressing roller 13 arranged opposite thereto, and the color image formed on the intermediate transfer belt 7 is transferred to the paper P. Transcribed. And the paper P
Is supplied to the fixing device 14 and is discharged after fixing the toner image.

【0022】中間転写ベルト7の表面には、画像形成ユ
ニット2〜5の感光体ドラム2a〜5aと一次転写ロー
ラ10a〜10dのニップ力によってイエロー,マゼン
タ,シアン,ブラックのトナー像が付着し、カラー画像
が形成される。そして、中間転写ベルト7上のカラー画
像は二次転写ローラ11と押圧ローラ13との間のニッ
プ力によって用紙Pに転写される。
Yellow, magenta, cyan and black toner images adhere to the surface of the intermediate transfer belt 7 by the nip force of the photosensitive drums 2a to 5a of the image forming units 2 to 5 and the primary transfer rollers 10a to 10d. A color image is formed. Then, the color image on the intermediate transfer belt 7 is transferred to the sheet P by a nip force between the secondary transfer roller 11 and the pressing roller 13.

【0023】一次転写ローラ10a〜10dは上下に移
動し、テンションローラ9は中間転写ベルト7に張力を
負荷したり弛めたりする方向に移動する。このような一
次転写ローラ10a〜10d及びテンションローラ9の
移動は、中間転写ベルト7の寿命を長くすることをひと
つの目的としたものである。すなわち、印字動作のとき
には、図示のように、一次転写ローラ10a〜10d上
に移動して感光体ドラム2a〜5aとの間に中間転写ベ
ルト7をニップし、テンションローラ9は右斜め下に移
動して中間転写ベルト7に張力を与える。そして、非印
字期間では、一次転写ローラ10a〜10dは下降する
とともに、テンションローラ9は左斜め上に移動して中
間転写ベルト7の張力を弛める。このように操作するこ
とで、非印字期間における中間転写ベルト7への負荷を
低減して寿命を長くする。また、押圧ローラ13も印字
期間では図示のように中間転写ベルト7に接触するが、
非印字期間では左側に移動して離れ、停止している中間
転写ベルト7への局部的な押圧力負荷を零にして寿命を
長くする。
The primary transfer rollers 10a to 10d move up and down, and the tension roller 9 moves in a direction of applying or loosening tension to the intermediate transfer belt 7. The movement of the primary transfer rollers 10a to 10d and the tension roller 9 has one purpose of extending the life of the intermediate transfer belt 7. That is, at the time of a printing operation, as shown in the drawing, the intermediate transfer belt 7 is moved over the primary transfer rollers 10a to 10d to nip the intermediate transfer belt 7 with the photosensitive drums 2a to 5a, and the tension roller 9 is moved diagonally to the lower right. Then, tension is applied to the intermediate transfer belt 7. In the non-printing period, the primary transfer rollers 10a to 10d move down, and the tension roller 9 moves diagonally to the upper left to loosen the tension of the intermediate transfer belt 7. By performing such operations, the load on the intermediate transfer belt 7 during the non-printing period is reduced, and the life is extended. The pressing roller 13 also contacts the intermediate transfer belt 7 as shown in the drawing during the printing period.
During the non-printing period, the local pressing force applied to the intermediate transfer belt 7 that has moved to the left and moved away and stopped is reduced to zero to extend the life.

【0024】図2(a)は一次転写ローラの上下動作と
中間転写ベルトの挙動を示す要部の概略図であって、一
次転写ローラが下降しているときの概略図、(b)は一
次転写ローラの上下動作と中間転写ベルトの挙動を示す
要部の概略図であって、一次転写ローラが上昇して中間
転写ベルトを感光体ドラムに接触させているときの概略
図をそれぞれ示す。
FIG. 2A is a schematic view of a main part showing the vertical movement of the primary transfer roller and the behavior of the intermediate transfer belt. FIG. 2B is a schematic view when the primary transfer roller is lowered, and FIG. FIGS. 4A and 4B are schematic views of a main part showing a vertical movement of a transfer roller and a behavior of an intermediate transfer belt, and respectively show schematic views when a primary transfer roller is raised and an intermediate transfer belt is in contact with a photosensitive drum.

【0025】本発明において一次転写ローラ10a〜1
0dは安価に得られる金属丸棒を利用したもので、前述
したように、感光体ドラム2a〜5aと中間転写ベルト
7を安定して接触させるために、各一次転写ローラ10
a〜10dは感光体ドラム2a〜5aと直接ニップを形
成するのではなく少しずれた位置に配置されている。す
なわち、中間転写ベルト7の走行方向に観て上流に位置
する感光体ドラム2aに対して一次転写ローラ10aは
少し上流側に位置し、その他の感光体ドラム3a〜5a
に対応する一次転写ローラ10b〜10dはそれぞれ少
し下流側に位置している。
In the present invention, the primary transfer rollers 10a to 10a
0d uses a metal round bar obtained at a low cost. As described above, in order to stably contact the photosensitive drums 2a to 5a and the intermediate transfer belt 7, each primary transfer roller 10d is used.
a to 10d do not directly form a nip with the photosensitive drums 2a to 5a, but are arranged at positions slightly shifted. That is, the primary transfer roller 10a is located slightly upstream with respect to the photosensitive drum 2a located upstream in the running direction of the intermediate transfer belt 7, and the other photosensitive drums 3a to 5a
Are respectively located slightly downstream.

【0026】このような構成において、図2の(a)の
状態から一次転写ローラ10a〜10dを上に移動させ
ると、同図の(b)のように一次転写ローラ10a〜1
0dが中間転写ベルト7を押し上げて感光体ドラム2a
〜5aに接触させる。このとき、上流側の感光体ドラム
2aに対応する一次転写ローラ10aが少し上流に外れ
ているので、感光体ドラム2aに対しては2個の一次転
写ローラ10a,10bによる押し付けにより中間転写
ベルト7が接触する。すなわち、一次転写ローラ10a
は従来の技術の昇降ローラと同様の機能を果たし、中間
転写ベルト7を安定して全ての感光体ドラム2a〜5a
に接触させることができ、安定したトナー像の転写が可
能となる。
In such a configuration, when the primary transfer rollers 10a to 10d are moved upward from the state of FIG. 2A, the primary transfer rollers 10a to 10d are moved as shown in FIG.
0d pushes up the intermediate transfer belt 7 and the photosensitive drum 2a
5a. At this time, since the primary transfer roller 10a corresponding to the photosensitive drum 2a on the upstream side is slightly shifted upstream, the intermediate transfer belt 7 is pressed against the photosensitive drum 2a by the two primary transfer rollers 10a and 10b. Contact. That is, the primary transfer roller 10a
Performs the same function as the conventional elevating roller, and stably moves the intermediate transfer belt 7 to all the photosensitive drums 2a to 5a.
, And stable toner image transfer becomes possible.

【0027】図3(a)は3本の一次転写ローラを備え
る例の要部の概略図であって、一次転写ローラが下降し
ているときの概略図、(b)は3本の一次転写ローラを
備える例の要部の概略図であって、一次転写ローラが上
昇して中間転写ベルトを感光体ベルトに接触させている
ときの概略図をそれぞれ示す。
FIG. 3A is a schematic view of a main part of an example having three primary transfer rollers, and is a schematic view when the primary transfer roller is lowered, and FIG. 3B is a schematic view of three primary transfer rollers. FIGS. 3A and 3B are schematic diagrams of main parts of an example including a roller, respectively, when a primary transfer roller is raised and an intermediate transfer belt is brought into contact with a photosensitive belt.

【0028】中間転写ベルト7の走行ループの形態は図
2の例と全く同様であり、一次転写ローラ10a,10
dの配置位置も同じである。本実施の形態では、これら
の一次転写ローラ10a,10dに加えて感光体ドラム
3a,4aの間のほぼ中間の位置に一次転写ローラ10
eを備えている。
The configuration of the running loop of the intermediate transfer belt 7 is exactly the same as the example of FIG. 2, and the primary transfer rollers 10a, 10a
The same applies to the arrangement position of d. In this embodiment, in addition to the primary transfer rollers 10a and 10d, the primary transfer roller 10 is located at a substantially intermediate position between the photosensitive drums 3a and 4a.
e.

【0029】この構成においても、一次転写ローラ10
a,10d,10eを上昇させると、同図の(b)に示
すように中間転写ベルト7が各感光体ドラム2a〜5a
に接触する。すなわち、上流側の感光体ドラム2a,3
aに対しては一次転写ローラ10a,10eの持ち上げ
によって中間転写ベルト7が接触させられ、下流側の感
光体ドラム4a,5aに対しては一次転写ローラ10
e,10dの持ち上げによって中間転写ベルト7が接触
させられる。このように、3本の一次転写ローラ10
a,10d,10eだけでも、従来のように昇降ローラ
を必要とすることなく中間転写ベルト7を安定して各感
光体ドラム2a〜5aに接触させることができ、良好な
トナー像の転写が可能となる。
Also in this configuration, the primary transfer roller 10
When a, 10d, and 10e are raised, the intermediate transfer belt 7 moves the photosensitive drums 2a to 5a as shown in FIG.
Contact That is, the upstream photosensitive drums 2a, 3
The intermediate transfer belt 7 is brought into contact with the photosensitive drums 4a and 5a on the downstream side by lifting the primary transfer rollers 10a and 10e.
The intermediate transfer belt 7 is brought into contact by the lifting of e and 10d. Thus, the three primary transfer rollers 10
The intermediate transfer belt 7 can be stably brought into contact with each of the photosensitive drums 2a to 5a without the need for the elevating roller as in the related art using only a, 10d, and 10e, so that a good toner image can be transferred. Becomes

【0030】さらに、図3において、一次転写ローラ1
0eを取り除いて2本の一次転写ローラ10a,10d
の上昇動作によっても中間転写ベルト7を各感光体ドラ
ム2a〜5aに接触させることができる。すなわち、感
光体ドラム2a〜5aの配列の全体を含むような位置に
一次転写ローラ10a,10dを配置することで、テン
ションローラ9によって中間転写ベルト7に適切な張力
を与えてさえおけば、これらの一次転写ローラ10a,
10dだけでも中間転写ベルト7を各感光体ドラム2a
〜5aに適切に接触させることができる。
Further, in FIG. 3, the primary transfer roller 1
0e, and removes the two primary transfer rollers 10a and 10d.
The intermediate transfer belt 7 can be brought into contact with each of the photosensitive drums 2a to 5a also by the ascent operation. That is, by arranging the primary transfer rollers 10a and 10d at positions including the entire arrangement of the photosensitive drums 2a to 5a, as long as the tension roller 9 applies an appropriate tension to the intermediate transfer belt 7, Primary transfer roller 10a,
10d alone, the intermediate transfer belt 7 is connected to each photosensitive drum 2a.
~ 5a can be appropriately contacted.

【0031】以上のように、最も上流側の感光体ドラム
2aよりも少し上流側に一次転写ローラ10aを配置
し、最も下流側の感光体ドラム5aよりも少し下流側に
一次転写ローラ10dを配置するという条件であれば、
これらの一次転写ローラ10a,10dの間に任意数の
一次転写ローラを配置しても感光体ドラム2a〜5aか
ら中間転写ベルト7への良好なトナー像の転写が可能と
なる。
As described above, the primary transfer roller 10a is disposed slightly upstream of the most upstream photosensitive drum 2a, and the primary transfer roller 10d is disposed slightly downstream of the most downstream photosensitive drum 5a. If the condition is
Even if an arbitrary number of primary transfer rollers are arranged between these primary transfer rollers 10a and 10d, it is possible to transfer a good toner image from the photosensitive drums 2a to 5a to the intermediate transfer belt 7.

【0032】[0032]

【発明の効果】本発明によれば、一次転写ローラを利用
して中間転写ベルトを全ての画像形成ユニットの感光体
ドラムに接触させてトナー像を印字させることができ、
従来のように昇降ローラを必要とせずしかも中間転写ベ
ルトを短くできるので、安価な製品が得られる。また、
一次転写ローラは感光体ドラムと直にニップを形成しな
いようにずれた位置に配置されるので、一次転写ローラ
として金属丸棒等を用いることができ更に安価な製品と
することができる。
According to the present invention, a toner image can be printed by bringing the intermediate transfer belt into contact with the photosensitive drums of all the image forming units using the primary transfer roller.
Unlike the conventional case, the intermediate transfer belt can be shortened without the need for the elevating roller, so that an inexpensive product can be obtained. Also,
Since the primary transfer roller is arranged at a position shifted so as not to form a nip directly with the photosensitive drum, a metal round bar or the like can be used as the primary transfer roller, so that a more inexpensive product can be obtained.

【図面の簡単な説明】[Brief description of the drawings]

【図1】本発明の一実施の形態によるカラー画像形成装
置の要部の構成を示す断面図
FIG. 1 is a cross-sectional view showing a configuration of a main part of a color image forming apparatus according to an embodiment of the present invention.

【図2】(a)一次転写ローラの上下動作と中間転写ベ
ルトの挙動を示す要部の概略図であって、一次転写ロー
ラが下降しているときの概略図 (b)一次転写ローラの上下動作と中間転写ベルトの挙
動を示す要部の概略図であって、一次転写ローラが上昇
して中間転写ベルトを感光体ドラムに接触させていると
きの概略図
FIG. 2A is a schematic view of a main part showing a vertical transfer operation of a primary transfer roller and a behavior of an intermediate transfer belt, and is a schematic view when the primary transfer roller is lowered. FIG. FIG. 4 is a schematic view of a main part showing an operation and a behavior of the intermediate transfer belt, and is a schematic view when a primary transfer roller is raised and the intermediate transfer belt is in contact with a photosensitive drum.

【図3】(a)3本の一次転写ローラを備える例の要部
の概略図であって、一次転写ローラが下降しているとき
の概略図 (b)3本の一次転写ローラを備える例の要部の概略図
であって、一次転写ローラが上昇して中間転写ベルトを
感光体ベルトに接触させているときの概略図
FIG. 3A is a schematic view of a main part of an example including three primary transfer rollers, and is a schematic view when the primary transfer roller is lowered. FIG. 3B is an example of including three primary transfer rollers. FIG. 4 is a schematic view of a main part of the image forming apparatus, schematically showing a state in which a primary transfer roller is raised and an intermediate transfer belt is brought into contact with a photosensitive belt

【図4】(a)昇降ローラを備える従来の技術の要部の
概略図であって、一次転写ローラ及び昇降ローラが下降
しているときの概略図 (b)昇降ローラを備える従来の技術の要部の概略図で
あって、一次転写ローラ及び昇降ローラが上昇して中間
転写ベルトを感光体ベルトに接触させているときの概略
FIG. 4A is a schematic view of a main part of a conventional technique including an elevating roller, and is a schematic view when a primary transfer roller and an elevating roller are lowered. FIG. 4B is a schematic view of a conventional technique including an elevating roller. FIG. 4 is a schematic diagram of a main part, when the primary transfer roller and the elevating roller are raised and the intermediate transfer belt is in contact with the photosensitive belt.

【符号の説明】[Explanation of symbols]

1 本体 2,3,4,5 画像形成ユニット 2a,3a,4a,5a 感光体ドラム 2b,3b,4b,5b 現像ローラ 6a,6b,6c,6d 露光器 7 中間転写ベルト 8 駆動ローラ 9 テンションローラ 10a,10b,10c,10d,10e 一次転写ロ
ーラ 11 二次転写ローラ 12 用紙トレイ 13 押圧ローラ 14 定着器 P 用紙
DESCRIPTION OF SYMBOLS 1 Main body 2,3,4,5 Image forming unit 2a, 3a, 4a, 5a Photoconductor drum 2b, 3b, 4b, 5b Developing roller 6a, 6b, 6c, 6d Exposure device 7 Intermediate transfer belt 8 Drive roller 9 Tension roller 10a, 10b, 10c, 10d, 10e Primary transfer roller 11 Secondary transfer roller 12 Paper tray 13 Press roller 14 Fixer P Paper

Claims (5)

【特許請求の範囲】[Claims] 【請求項1】トナー像を担持する感光体ドラムを含んで
複数配列されそれぞれトナー色の異なる画像を形成する
画像形成ユニットと、前記感光体ドラムに接触可能に配
置され前記トナー像が転写されるエンドレスの中間転写
ベルトと、前記中間転写ベルトのループ内に配置され前
記感光体ドラムと所定の電位差を有し前記感光体ドラム
上の前記トナー像を前記中間転写ベルトに転写させる複
数の一次転写ローラと、前記中間転写ベルトのループ内
に配置され当該中間転写ベルト上のトナー像を記録媒体
に転写する二次転写ローラとを備えたタンデム方式のカ
ラー画像形成装置において、前記一次ローラの上昇動作
のみによって前記中間転写ベルトを前記感光体ドラムに
接触可能としたことを特徴とするカラー画像形成装置。
An image forming unit that includes a plurality of photosensitive drums that carry a toner image and forms images of different toner colors, and is arranged so as to be in contact with the photosensitive drum and transfers the toner image. An endless intermediate transfer belt, and a plurality of primary transfer rollers disposed in a loop of the intermediate transfer belt and having a predetermined potential difference from the photosensitive drum and transferring the toner image on the photosensitive drum to the intermediate transfer belt And a secondary transfer roller disposed in a loop of the intermediate transfer belt and transferring the toner image on the intermediate transfer belt to a recording medium, wherein only the raising operation of the primary roller is performed. A color image forming apparatus, wherein the intermediate transfer belt can be brought into contact with the photosensitive drum.
【請求項2】前記中間転写ベルトの移動方向最上流にあ
る前記感光体ドラムに対向した前記一次転写ローラを前
記感光体ドラムに対し上流側に、前記中間転写ベルトの
移動方向最下流にある前記感光体ドラムに対向した前記
一次転写ローラを前記感光体ドラムに対し下流側に配置
したことを特徴とする請求項1記載のカラー画像形成装
置。
2. The image forming apparatus according to claim 1, wherein the primary transfer roller facing the photosensitive drum, which is the most upstream in the moving direction of the intermediate transfer belt, is located on the upstream side with respect to the photosensitive drum, and is located on the most downstream side in the moving direction of the intermediate transfer belt. 2. The color image forming apparatus according to claim 1, wherein the primary transfer roller facing the photosensitive drum is disposed downstream of the photosensitive drum.
【請求項3】前記一次転写ローラの配列数を前記感光体
ドラムの配列数よりも少なくしたことを特徴とする請求
項1記載のカラー画像形成装置。
3. The color image forming apparatus according to claim 1, wherein the number of said primary transfer rollers is smaller than the number of said photosensitive drums.
【請求項4】前記感光体ドラムの配列数が4個で、前記
一次転写ローラを前記中間転写ベルトの移動方向最上流
にある前記感光体ドラムの上流側、前記感光体ドラムの
配列の2個目と3個目の中間、前記中間転写ベルトの移
動方向最下流にある前記感光体ドラムの下流側の3個配
列することを特徴とする請求項3記載のカラー画像形成
装置。
4. The photosensitive drums are arranged in a number of four, and the primary transfer roller is arranged upstream of the photosensitive drum at the most upstream in the moving direction of the intermediate transfer belt, and two of the photosensitive drums are arranged. 4. The color image forming apparatus according to claim 3, wherein three of the photosensitive drums are arranged in the middle of the third and the third drums at the downstream side in the moving direction of the intermediate transfer belt.
【請求項5】前記画像形成ユニットをそれぞれイエロ
ー,マゼンタ,シアン,ブラックの4色のトナー画像形
成用として配列し、前記一次転写ローラと、前記イエロ
ーの画像形成ユニットの感光体ドラムの上流側との相対
位置のみが、他の画像形成ユニットの相対位置と異なる
ことを特徴とする請求項2記載のカラー画像形成装置。
5. The image forming units are arranged for forming toner images of four colors of yellow, magenta, cyan, and black, respectively, and the primary transfer roller and an upstream side of a photosensitive drum of the yellow image forming unit are arranged. 3. The color image forming apparatus according to claim 2, wherein only the relative position of the image forming unit differs from the relative positions of the other image forming units.
JP2000113760A 2000-04-14 2000-04-14 Color image forming apparatus Expired - Fee Related JP4395981B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2000113760A JP4395981B2 (en) 2000-04-14 2000-04-14 Color image forming apparatus

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006189614A (en) * 2005-01-06 2006-07-20 Fuji Xerox Co Ltd Image forming apparatus
US7813682B2 (en) 2005-03-11 2010-10-12 Brother Kogyo Kabushiki Kaisha Image forming apparatus that smoothly conveys transfer medium while suppressing pre-transfer
JP2011133719A (en) * 2009-12-25 2011-07-07 Canon Inc Electrophotographic image forming apparatus
US8175479B2 (en) 2006-11-21 2012-05-08 Ricoh Company, Ltd. Transfer device and image forming apparatus having first and second transfer nips and first and second contacting members which apply transfer biases
US8588666B2 (en) 2010-05-24 2013-11-19 Casio Electronics Manufacturing Co., Ltd. Image forming apparatus with a movable primary transfer roller

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006189614A (en) * 2005-01-06 2006-07-20 Fuji Xerox Co Ltd Image forming apparatus
JP4649991B2 (en) * 2005-01-06 2011-03-16 富士ゼロックス株式会社 Image forming apparatus
US7813682B2 (en) 2005-03-11 2010-10-12 Brother Kogyo Kabushiki Kaisha Image forming apparatus that smoothly conveys transfer medium while suppressing pre-transfer
US8175479B2 (en) 2006-11-21 2012-05-08 Ricoh Company, Ltd. Transfer device and image forming apparatus having first and second transfer nips and first and second contacting members which apply transfer biases
JP2011133719A (en) * 2009-12-25 2011-07-07 Canon Inc Electrophotographic image forming apparatus
US8588666B2 (en) 2010-05-24 2013-11-19 Casio Electronics Manufacturing Co., Ltd. Image forming apparatus with a movable primary transfer roller

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