JP2001201954A - Image forming device and image forming method - Google Patents

Image forming device and image forming method

Info

Publication number
JP2001201954A
JP2001201954A JP2000011884A JP2000011884A JP2001201954A JP 2001201954 A JP2001201954 A JP 2001201954A JP 2000011884 A JP2000011884 A JP 2000011884A JP 2000011884 A JP2000011884 A JP 2000011884A JP 2001201954 A JP2001201954 A JP 2001201954A
Authority
JP
Japan
Prior art keywords
image forming
intermediate transfer
image
bias
forming apparatus
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.)
Pending
Application number
JP2000011884A
Other languages
Japanese (ja)
Inventor
Kazuchika Saeki
和親 佐伯
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.)
Ricoh Co Ltd
Original Assignee
Ricoh 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 Ricoh Co Ltd filed Critical Ricoh Co Ltd
Priority to JP2000011884A priority Critical patent/JP2001201954A/en
Publication of JP2001201954A publication Critical patent/JP2001201954A/en
Pending legal-status Critical Current

Links

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of forming a high-quality image having no horizontal band in terms of halftone by removing the charge of an intermediate transfer belt more surely than in the case of removing the charge of the belt while brining a grounded conductive member into contact therewith. SOLUTION: This image forming device using the intermediate transfer belt 10 is provided with a secondary transfer bias roller 14 arranged to come into contact with and is separated from the belt 10 and functioning also as a charge removing member for charge removing the belt 10, a contact and separating mechanism 16 making the roller 14 contact with/separated from the belt 10, and a high voltage power source 100 applying charge removing bias for removing the electrified charge of the belt 10 electrified during image forming operation to the roller 14.

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、複写機、プリンタ
ー、FAXなどの画像形成装置及び該装置に採用される
画像形成方法に係り、詳しくは、像担持体上にトナー像
を形成し、該像担持体上のトナー像を中間転写体に一次
転写し、該中間転写体上のトナー像を更に転写材に二次
転写する画像形成方法及びその装置に関するものであ
る。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile and the like, and an image forming method employed in the apparatus. More specifically, the present invention relates to a method for forming a toner image on an image bearing member. The present invention relates to an image forming method and an image forming apparatus for primary-transferring a toner image on an image carrier to an intermediate transfer body and further secondary-transferring the toner image on the intermediate transfer body to a transfer material.

【0002】[0002]

【従来の技術】従来、この種の画像形成装置として、像
担持体としての感光体上に形成されたトナー像を転写材
に転写し、その後転写材上の該トナー画像を定着器によ
って加熱圧着を行い定着するものが知られている。ま
た、フルカラー画像を形成する装置としては転写材を転
写ドラムなどの転写材担持体に保持させた状態で、感光
体に現像されたイエロー、マゼンタ、シアン、ブラック
の各色を転写材に順次転写し、その後転写材担持体から
剥離させた転写材を定着器によって加熱圧着を行い定着
するものが知られている。一方、感光体上のトナー像を
転写材担持体上の転写材に転写するのではなく、例えば
特開平5−11562号公報に開示されているように、
一旦中間転写体上に重ねあわせた4色のトナー像を転写
材に一括転写した後、定着器によって定着する画像形成
装置もある。この中間転写体を用いた画像形成装置にお
いては、転写材を転写材担持体に保持させる必要が無い
ため、薄紙(40g/m)や厚紙(200g/m)、
はがき、封筒などさまざまな種類の転写材が使用可能で
あり、転写材汎用性が高いという利点を有する。この中
間転写体としては、中間転写ドラムまたは中間転写ベル
トが一般的に用いられる。
2. Description of the Related Art Conventionally, as an image forming apparatus of this type, a toner image formed on a photoreceptor as an image carrier is transferred to a transfer material, and then the toner image on the transfer material is heated and pressed by a fixing device. Is known. In addition, as a device for forming a full-color image, while the transfer material is held on a transfer material carrier such as a transfer drum, each color of yellow, magenta, cyan, and black developed on the photoconductor is sequentially transferred to the transfer material. Then, a transfer material peeled off from the transfer material carrier is heated and pressed by a fixing device to fix the transfer material. On the other hand, instead of transferring the toner image on the photoreceptor to the transfer material on the transfer material carrier, for example, as disclosed in JP-A-5-11562,
There is also an image forming apparatus in which four color toner images once superimposed on an intermediate transfer body are collectively transferred to a transfer material and then fixed by a fixing device. In the image forming apparatus using the intermediate transfer body, it is not necessary to hold the transfer material on the transfer material carrier, and therefore, the thin paper (40 g / m 2 ), the thick paper (200 g / m 2 ),
Various types of transfer materials such as postcards and envelopes can be used, and there is an advantage that the transfer material has high versatility. As the intermediate transfer member, an intermediate transfer drum or an intermediate transfer belt is generally used.

【0003】[0003]

【発明が解決しようとする課題】ところが、上記従来装
置のように中間転写体を用いた画像形成装置には次のよ
うな問題点があった。上記中間転写体を用いた画像形成
時において、中間転写体は感光体や転写材との摺擦や剥
離工程が繰り返されるうえ、感光体から中間転写体へト
ナー像を転移させる一次転写工程と、さらに中間転写体
に転移保持されたトナー像を転写材へ転移させる二次転
写工程において高電圧が印加される。したがって、中間
転写体は剥離帯電、摩擦帯電および高電圧印加による電
荷注入などでその表面は帯電してしまう。特に上記中間
転写体の表面側から高電圧を印加する二次転写部での電
荷注入は、中間転写体表面の帯電に対する影響が極めて
大きい。また、感光体の露光された部分にトナー現像を
行なう反転現像では、感光体の表面電位と同極性に帯電
するトナーを用いるため、上記二次転写工程ではトナー
と逆極性、すなわち感光体表面電位とは逆極性となるバ
イアスを印加することから、中間転写体表面は感光体表
面電位とは逆極性に帯電することになる。
However, an image forming apparatus using an intermediate transfer member as in the above-mentioned conventional apparatus has the following problems. At the time of image formation using the intermediate transfer body, the intermediate transfer body is repeatedly subjected to a rubbing and peeling step with a photoconductor and a transfer material, and a primary transfer step of transferring a toner image from the photoconductor to the intermediate transfer body, Further, a high voltage is applied in a secondary transfer step of transferring the toner image transferred and held on the intermediate transfer member to a transfer material. Therefore, the surface of the intermediate transfer member is charged by peeling charging, friction charging, charge injection by applying a high voltage, and the like. In particular, the charge injection at the secondary transfer portion where a high voltage is applied from the surface side of the intermediate transfer member has a very large effect on the charging of the surface of the intermediate transfer member. Further, in the reversal development in which toner development is performed on an exposed portion of the photoconductor, a toner charged to the same polarity as the surface potential of the photoconductor is used. Is applied, the surface of the intermediate transfer member is charged to a polarity opposite to the surface potential of the photoreceptor.

【0004】以上のように画像形成動作時に中間転写体
の帯電が発生すると、画像形成が終了し装置の動作が停
止したときに、感光体と中間転写体が接触している部位
において、感光体表面電位と逆極性に帯電した中間転写
体表面から感光体表面に対し電荷注入が行われる。この
ため、一定時間以上装置停止状態にて放置された場合、
感光体にメモリー効果が発生し、次の画像形成時の全面
ハーフトーン画像上における感光体と中間転写体の接触
部に相当する部分で濃度が高くなる現象(以下、この現
象を「ハーフトーン上横帯」という。)が発生してしま
う。なお、ここでいう「メモリー効果」とは、感光体に
感光体表面電位と逆極性の電荷注入が行われた場合、次
の画像形成時にはその部分の表面電位が十分に上がら
ず、ひどい場合には地肌部かぶりとなることをいう。
As described above, when the intermediate transfer member is charged during the image forming operation, when the image formation is completed and the operation of the apparatus is stopped, the photosensitive member is brought into contact with the intermediate transfer member at a portion where the intermediate transfer member is in contact. Charge injection is performed from the surface of the intermediate transfer member charged to a polarity opposite to the surface potential to the surface of the photosensitive member. For this reason, if the device is left idle for a certain period of time,
A phenomenon in which a memory effect occurs on the photoreceptor and a density is increased in a portion corresponding to a contact portion between the photoreceptor and the intermediate transfer body on the entire halftone image at the time of the next image formation (hereinafter, this phenomenon is referred to as “halftone This is called "horizontal band"). Note that the "memory effect" here means that when charge injection of a polarity opposite to the surface potential of the photoreceptor is performed on the photoreceptor, the surface potential of that portion is not sufficiently increased at the time of the next image formation and is severe. Means that the skin is covered.

【0005】なお、上記中間転写体の帯電を防止するこ
とができる装置として、特開平4−271379号公報
には、中間転写体の表面および裏面に、接地した導電性
ブラシ等の導電性部材を接触対向するように配設した画
像形成装置が記載されている。また、特開平8−114
994号公報には、中間転写体の端部における非画像領
域に導電性の除電ブラシを当接させ、転写時には電気的
に非接地、除電時には電気的に接地とすることで、中間
転写体の除電を行なうようにした画像形成層位置が記載
されている。しかしながら、上記公報に記載されている
ように中間転写体の表面に上記接地した導電性部材を接
触させて該中間転写体の除電を行う構成では、該中間転
写体表面の帯電電荷を十分に逃がすことができず、該中
間転写体を確実に除電できないおそれがあった。
Japanese Patent Application Laid-Open No. Hei 4-271379 discloses a device capable of preventing the charging of the intermediate transfer member, which includes a conductive member such as a grounded conductive brush on the front and back surfaces of the intermediate transfer member. An image forming apparatus disposed so as to be in contact with and facing is described. Also, JP-A-8-114
No. 994 discloses that a conductive neutralizing brush is brought into contact with a non-image area at an end portion of an intermediate transfer body, and is electrically grounded at the time of transfer and electrically grounded at the time of neutralization. It describes the position of the image forming layer where static elimination is performed. However, as described in the above publication, in the configuration in which the grounded conductive member is brought into contact with the surface of the intermediate transfer body to remove the charge of the intermediate transfer body, the charge on the surface of the intermediate transfer body is sufficiently released. As a result, the intermediate transfer member may not be reliably discharged.

【0006】本発明は以上の問題点に鑑みなされたもの
であり、その目的は、接地した導電性部材を接触させて
除電する場合に比してより確実に中間転写体の除電を行
い、ハーフトーン上横帯のない高品質の画像を形成する
ことができる画像形成装置及び画像形成方法を提供する
ことである。
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to perform more reliable static electricity removal of an intermediate transfer member as compared with a case where a grounded conductive member is contacted to remove electricity. An object of the present invention is to provide an image forming apparatus and an image forming method capable of forming a high-quality image without a horizontal band on a tone.

【0007】[0007]

【課題を解決するための手段】上記目的を達成するため
に、請求項1の発明は、像担持体と、該像担持体上にト
ナー像を形成するトナー像形成手段と、該像担持体上の
トナー像が転写される中間転写体と、該像担持体上のト
ナー像を該中間転写体に一次転写する一次転写手段と、
該中間転写体上のトナー像を転写材に二次転写する二次
転写手段とを備えた画像形成装置において、上記中間転
写体に対して接離可能に配置された該中間転写体を除電
するための除電部材と、該中間転写体に対して該除電部
材を接離させる接離手段と、画像形成動作時に帯電した
該中間転写体の帯電電荷を除去するための除電用バイア
スを該除電部材に印加する除電用バイアス印加手段とを
設けたことを特徴とするものである。この画像形成装置
では、除電用バイアス印加手段により、画像形成動作時
に帯電した中間転写体の帯電電荷を除去するための除電
用バイアスを、中間転写体に対して接離可能に配置され
た除電部材に印加する。中間転写体の表面にトナー像を
担持している画像形成時には、該中間転写体上のトナー
像を乱さないように該除電部材を接離手段で該中間転写
体から離間させる。そして、中間転写体を除電するとき
は、該除電用バイアスを印加した除電部材を接離手段で
該中間転写体に接触させる。この除電用バイアスを印加
した除電部材の接触により、該中間転写体の帯電電荷が
積極的に中和されるため、接地した導電性部材を接触さ
せて除電する場合に比してより確実に中間転写体の除電
を行うことができる。
According to one aspect of the present invention, there is provided an image carrier, a toner image forming means for forming a toner image on the image carrier, and an image carrier. An intermediate transfer member on which the upper toner image is transferred, and a primary transfer unit that primarily transfers the toner image on the image carrier to the intermediate transfer member;
In an image forming apparatus provided with a secondary transfer means for secondary-transferring the toner image on the intermediate transfer member to a transfer material, the intermediate transfer member disposed so as to be able to contact and separate from the intermediate transfer member is neutralized. A charging / discharging member for moving the charging / discharging member to and away from the intermediate transfer member, and a biasing / removing member for removing a charge of the intermediate transfer member charged during an image forming operation. And a bias applying means for removing static electricity. In this image forming apparatus, the charge removing bias for removing the charge of the intermediate transfer member charged during the image forming operation is provided by the charge removing bias applying unit, and the charge removing member is disposed so as to be able to contact and separate from the intermediate transfer member. Is applied. When forming an image carrying a toner image on the surface of the intermediate transfer member, the charge removing member is separated from the intermediate transfer member by the contact / separation means so as not to disturb the toner image on the intermediate transfer member. Then, when the intermediate transfer body is to be neutralized, the neutralization member to which the bias for neutralization has been applied is brought into contact with the intermediate transfer body by a contacting / separating means. Since the charge of the intermediate transfer member is positively neutralized by the contact of the charge removing member to which the charge removing bias is applied, the intermediate charge can be more reliably made as compared with a case where the charge is removed by contacting the grounded conductive member. The transfer member can be neutralized.

【0008】請求項2の発明は、請求項1の画像形成装
置において、上記除電用バイアスが印加された上記除電
部材が接触する上記中間転写体の表面上の領域が、画像
形成動作終了時に上記像担持体が接触していた領域を含
むことを特徴とするものである。この画像形成装置で
は、画像形成動作終了時に上記像担持体が接触していた
上記帯電が発生しやすい領域に、除電用バイアスを印加
した除電部材を接触させるため、該領域の除電を確実に
行うことができる。
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the area on the surface of the intermediate transfer member with which the neutralization member to which the neutralization bias is applied comes into contact when the image forming operation is completed. It is characterized by including an area where the image carrier has been in contact. In this image forming apparatus, the charge removal member to which the charge is easily applied, which has been in contact with the image carrier at the end of the image forming operation, is brought into contact with the charge removing member to which the charge removing bias is applied. be able to.

【0009】請求項3の発明は、上記トナー像形成手段
を、上記像担持体の表面を一様帯電する帯電手段と、該
像担持体の一様帯電された表面を露光して潜像を形成す
る露光手段と、該像担持体上の潜像を現像してトナー像
を形成する現像手段とを用いて構成した請求項1の画像
形成装置であって、上記除電手段で除電された後の上記
中間転写体の表面電位の絶対値をVT2とし、上記帯電
手段で一様帯電された上記像担持体の表面電位の絶対値
をVH1としたとき、VT2≦0.5×VH1を満足す
ることを特徴とするものである。この画像形成装置で
は、上記VT2≦0.5×VH1を満足するように中間
転写体を除電することにより、上記一様帯電された像担
持体の表面電位が互いに異なる複数の条件下において
も、画像形成が終了し装置の動作が停止したときに、前
述の「ハーフトーン上横帯」という現象が発生するよう
な中間転写体から像担持体への電荷注入が発生しないよ
うにする。
According to a third aspect of the present invention, the toner image forming means includes a charging means for uniformly charging the surface of the image bearing member, and a latent image formed by exposing the uniformly charged surface of the image bearing member. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus includes: an exposing unit that forms the toner image; and a developing unit that develops the latent image on the image carrier to form a toner image. When the absolute value of the surface potential of the intermediate transfer member is V T2 and the absolute value of the surface potential of the image carrier uniformly charged by the charging means is V H1 , V T2 ≦ 0.5 × V H1 is satisfied. In this image forming apparatus, the intermediate transfer member is neutralized so as to satisfy the above-mentioned V T2 ≦ 0.5 × V H1 , so that the surface potential of the uniformly charged image carrier under a plurality of conditions different from each other. Also, when the image formation is completed and the operation of the apparatus is stopped, the charge injection from the intermediate transfer member to the image carrier, which causes the phenomenon of the above-described "halftone upper horizontal band", is prevented.

【0010】請求項4の発明は、請求項1の画像形成装
置において、画像形成条件に基づいて上記除電部材に印
加する除電用バイアスを変更するように、上記除電用バ
イアス印加手段を制御する制御手段を設けたことを特徴
とするものである。この画像形成装置では、画像形成条
件に基づいて上記除電部材に印加する除電用バイアスを
変更することにより、画像形成条件が変わる場合でも上
記中間転写体の除電を確実に行うことが可能となる。
According to a fourth aspect of the present invention, in the image forming apparatus of the first aspect, a control is provided for controlling the bias applying means for static elimination so as to change the bias for static elimination applied to the neutralizing member based on image forming conditions. A means is provided. In this image forming apparatus, by changing the bias for static elimination applied to the static elimination member based on the image forming conditions, even when the image forming conditions change, static elimination of the intermediate transfer body can be reliably performed.

【0011】請求項5の発明は、請求項4の画像形成装
置において、上記画像形成動作時の条件が、転写材の種
類、装置内の温度及び湿度、並びに上記中間転写体への
トナー像の重ね合わせ数の少なくとも一つであることを
特徴とするものである。この画像形成装置では、上記転
写材の種類等に基づいて上記除電部材に印加する除電用
バイアスを変更することにより、転写材の種類等によっ
て中間転写体の帯電電位が変わる場合でも上記中間転写
体の除電を確実に行うことが可能となる。
According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the conditions at the time of the image forming operation include a kind of a transfer material, a temperature and a humidity in the apparatus, and a toner image on the intermediate transfer body. The number of superpositions is at least one. In this image forming apparatus, by changing the charge removing bias applied to the charge removing member based on the type of the transfer material, the intermediate transfer body is changed even when the charging potential of the intermediate transfer body changes depending on the type of the transfer material. Can be reliably performed.

【0012】なお、本請求項5の発明において、上記
「転写材の種類」には、普通紙、厚紙、OHPシート等
の違いによる種類のほか、画像形成を既に経験している
か否かの違いによる転写材の種類も含まれる。例えば、
転写材の両面に画像を形成する場合の最初の面(表面)
に画像を形成するときの転写材と、2番目の面(裏面に
画像を形成するときの転写材とは、別種類の転写材とな
る。
In the invention of claim 5, the "type of transfer material" includes not only the type of plain paper, thick paper, OHP sheet, etc., but also the difference of whether image formation has already been experienced. The type of transfer material is also included. For example,
The first side (front side) when images are formed on both sides of the transfer material
The transfer material for forming an image on the second surface and the transfer material for forming an image on the second surface (the back surface) are different types of transfer materials.

【0013】請求項6の発明は、上記二次転写手段を、
上記転写材を介して上記中間転写体に接離可能に配設さ
れた二次転写部材と、該二次転写部材に二次転写用バイ
アスを印加する二次転写用バイアス印加手段とを用いて
構成した請求項1の画像形成装置であって、上記除電部
材として上記二次転写部材を兼用し、上記除電用バイア
ス印加手段として上記二次転写用バイアス印加手段を兼
用し、画像形成動作終了後の非画像形成時に、該二次転
写部材を上記中間転写体に接触させるとともに、該二次
転写部材に印加する電圧を上記二次転写用バイアスから
上記除電用バイアスに切り替えるように、上記離接手段
及び該二次転写用バイアス印加手段を制御する制御手段
を設けたことを特徴とするものである。この画像形成装
置では、上記離接手段を制御手段で制御することによ
り、画像形成動作終了後の非画像形成時に、上記除電部
材として兼用した二次転写部材を中間転写体に接触させ
る。更に、上記除電用バイアス印加手段として兼用した
二次転写用バイアス印加手段を制御手段で制御すること
により、該二次転写部材に印加する電圧を二次転写用バ
イアスから除電用バイアスに切り替える。
According to a sixth aspect of the present invention, the secondary transfer means includes:
A secondary transfer member disposed so as to be able to contact and separate from the intermediate transfer body via the transfer material, and a secondary transfer bias applying unit for applying a secondary transfer bias to the secondary transfer member. 2. The image forming apparatus according to claim 1, wherein the secondary transfer member is also used as the charge removing member, and the secondary transfer bias applying unit is also used as the charge removing bias applying unit. The non-image forming step, the secondary transfer member is brought into contact with the intermediate transfer member, and the voltage applied to the secondary transfer member is switched from the secondary transfer bias to the charge eliminating bias so that the contact and disconnection are performed. Means and control means for controlling said secondary transfer bias applying means. In this image forming apparatus, the secondary transfer member also serving as the charge removing member is brought into contact with the intermediate transfer member during non-image formation after the end of the image forming operation by controlling the separation / contact means by the control means. Further, the voltage applied to the secondary transfer member is switched from the secondary transfer bias to the charge eliminating bias by controlling the secondary transfer bias applying means also serving as the charge eliminating bias applying means by the control means.

【0014】請求項7の発明は、請求項6の画像形成装
置において、上記二次転写部材が、上記除電用バイアス
が印加される芯金部上に弾性体からなる表面部を有する
ローラ状部材であり、該芯金部と上記中間転写体に接触
する接触部との間の抵抗値が、10〜1010Ωであ
ることを特徴とするものである。ここで、上記抵抗値
は、導電性の金属板上に上記ローラ状部材を設置し、該
ローラ状部材の芯金部両端に片側4.9N(両側で合計
9.8N)の荷重を掛けた状態で、該芯金部と該金属板
との間に1000Vの電圧を印加したときに流れる電流
値から算出したものである。この画像形成装置では、上
記二次転写部材としてのローラ状部材の上記抵抗値が1
Ω以上であるので、中間転写体上のトナー像の重ね
合わせの有無や重ね合わせるトナー像の数が異なって
も、最適な二次転写電流を得るための二次転写バイアス
の範囲が大きくずれない。したがって、上記トナー像の
重ね合わせの数が多い場合に合わせて二次転写バイアス
を設定しても、トナー像の重ね合わせがないときに二次
転写電流が過剰になって転写効率が低下してしまう事態
が発生しにくくなる。更に、上記ローラ部材の上記抵抗
値が1010Ω以下であるので、良好な転写性を得るた
めの二次転写バイアスが過剰に高くなるのを抑制するこ
とができる。
According to a seventh aspect of the present invention, in the image forming apparatus of the sixth aspect, the secondary transfer member has a roller-shaped member having a surface portion made of an elastic body on a cored bar to which the bias for static elimination is applied. And a resistance value between the core metal portion and the contact portion that comes into contact with the intermediate transfer member is 10 5 to 10 10 Ω. Here, the resistance value is such that the roller-shaped member is placed on a conductive metal plate, and a load of 4.9 N on one side (9.8 N on both sides) is applied to both ends of the core of the roller-shaped member. In this state, it is calculated from a current value flowing when a voltage of 1000 V is applied between the metal core and the metal plate. In this image forming apparatus, the resistance value of the roller-shaped member as the secondary transfer member is 1
Since at 0 5 Omega above, even if the number of toner images superimposed and whether superposition of the toner images on the intermediate transfer body are different, the range of the secondary transfer bias for optimum secondary transfer current is large It does not slip. Therefore, even if the secondary transfer bias is set in accordance with the case where the number of superimposed toner images is large, the secondary transfer current becomes excessive when the superimposition of the toner images is not performed, and the transfer efficiency is reduced. It is less likely that the situation will occur. Furthermore, since the resistance value of the roller member is 10 10 Ω or less, it is possible to suppress an excessive increase in the secondary transfer bias for obtaining good transferability.

【0015】請求項8の発明は、請求項6の画像形成装
置において、上記二次転写部材が、上記中間転写体に対
向する導電性対向ローラを含む複数の支持ローラに支持
された弾性体からなるベルト状部材であり、該ベルト状
部材の該導電性対向ローラに接触する接触部と該中間転
写体に接触する接触部との間の抵抗値が、10〜10
10Ωであることを特徴とするものである。ここで、上
記抵抗値は、導電性の金属板上に上記ベルト状部材を介
して導電性ローラを設置し、該導電性ローラの両端に片
側4.9N(両側で合計9.8N)の荷重を掛けた状態
で、該導電性ローラと該金属板との間に1000Vの電
圧を印加したときに流れる電流値から算出したものであ
る。この画像形成装置では、上記二次転写部材としての
ベルト状部材の上記抵抗値が10Ω以上であるので、
上記トナー像の重ね合わせの数が多い場合に合わせて二
次転写バイアスを設定しても、トナー像の重ね合わせが
ないときに二次転写電流が過剰になって転写効率が低下
してしまう事態が発生しにくくなる。更に、上記ベルト
状部材の上記抵抗値が1010Ω以下であるので、良好
な転写性を得るための二次転写バイアスが過剰に高くな
るのを抑制することができる。
According to an eighth aspect of the present invention, in the image forming apparatus of the sixth aspect, the secondary transfer member is formed of an elastic body supported by a plurality of support rollers including a conductive opposed roller facing the intermediate transfer member. comprising a belt-shaped member, the resistance value between the contact portion in contact with the contact portion and the intermediate transfer member in contact with the conductive face roller of the belt-like member, 105 to
The characteristic is 10 Ω. Here, the resistance value is determined by placing a conductive roller on a conductive metal plate via the belt-shaped member and applying a load of 4.9 N on one side (9.8 N in total on both sides) to both ends of the conductive roller. Is calculated from the value of a current flowing when a voltage of 1000 V is applied between the conductive roller and the metal plate in a state in which is applied. In this image forming apparatus, since the resistance value of the belt-shaped member as the secondary transfer member is 10 5 Ω or more,
Even if the secondary transfer bias is set in accordance with the case where the number of superimposed toner images is large, the secondary transfer current becomes excessive and the transfer efficiency is reduced when there is no superimposition of toner images. Is less likely to occur. Further, since the resistance value of the belt-shaped member is 10 10 Ω or less, it is possible to suppress an excessive increase in the secondary transfer bias for obtaining good transferability.

【0016】請求項9の発明は、請求項1の画像形成装
置において、上記中間転写体の体積抵抗率が10〜1
12Ωcm且つ表面抵抗率が10〜1015Ω/□
であることを特徴とするものである。この画像形成装置
では、上記中間転写体の体積抵抗率が10Ωcm以上
且つ表面抵抗率が10Ω/□以上であるので、像担持
体から中間転写体へのトナー像の転写時に該中間転写体
の表面に沿って転写電流が流れるのを抑制することがで
きる。更に、上記中間転写体の体積抵抗率が1012Ω
cm以下且つ表面抵抗率が1015Ω/□以下であるの
で、像担持体から中間転写体へのトナー像の転写に必要
な一次転写バイアスを低く抑えるとともに、画像形成動
作時に帯電する該中間転写体の帯電電位を低く抑えるこ
とができる。
According to a ninth aspect of the present invention, in the image forming apparatus of the first aspect, the intermediate transfer body has a volume resistivity of 10 8 to 1.
0 12 Ωcm and surface resistivity of 10 8 to 10 15 Ω / □
It is characterized by being. In this image forming apparatus, since the volume resistivity of the intermediate transfer member is 10 8 Ωcm or more and the surface resistivity is 10 8 Ω / □ or more, the intermediate transfer member can transfer the toner image from the image carrier to the intermediate transfer member. It is possible to suppress the transfer current from flowing along the surface of the transfer body. Further, the volume resistivity of the intermediate transfer member is 10 12 Ω.
cm or less and the surface resistivity is 10 15 Ω / □ or less, so that the primary transfer bias necessary for transferring the toner image from the image carrier to the intermediate transfer member is kept low, and the intermediate transfer is charged during the image forming operation. The charge potential of the body can be kept low.

【0017】請求項10の発明は、請求項1の画像形成
装置において、上記除電用バイアスが、画像形成動作時
に帯電した上記中間転写体の帯電電位とは逆極性の直流
電圧であることを特徴とするものである。この画像形成
装置では、交流電源に比してより簡易に構成することが
できる直流電源で、上記所定の直流電圧を除電部材に印
加することにより、中間転写体の帯電電荷を積極的に中
和し、接地した導電性部材を接触させて除電する場合に
比してより確実に中間転写体の除電を行うことができ
る。
According to a tenth aspect of the present invention, in the image forming apparatus of the first aspect, the charge removing bias is a DC voltage having a polarity opposite to a charging potential of the intermediate transfer member charged during an image forming operation. It is assumed that. In this image forming apparatus, a DC power supply that can be configured more simply than an AC power supply applies the above-described predetermined DC voltage to the neutralizing member, thereby positively neutralizing the charged charges of the intermediate transfer body. In addition, static elimination of the intermediate transfer member can be performed more reliably than in a case where static elimination is performed by contacting a grounded conductive member.

【0018】請求項11の発明は、請求項1の画像形成
装置において、上記除電用バイアスが定電流制御された
交流電圧であり、該交流電圧の周波数[Hz]の値が、
画像形成装置のプロセス速度[mm/sec]の5倍以
上の値を有することを特徴とするものである。この画像
形成装置では、交流電圧からなる除電用バイアスを上記
除電部材に印加することにより、中間転写体の帯電電荷
を積極的に中和し、接地した導電性部材を接触させて除
電する場合に比してより確実に中間転写体の除電を行う
ことができる。しかも、該交流電圧が定電流制御され且
つ該交流電圧の周波数[Hz]の値が画像形成装置のプ
ロセス速度[mm/sec]の5倍以上の値であること
により、除電時の中間転写体上の電位変動のピッチが短
くなるので、該中間転写体の除電ムラを抑制することが
できる。
According to an eleventh aspect of the present invention, in the image forming apparatus of the first aspect, the charge eliminating bias is an AC voltage controlled by a constant current, and the value of the frequency [Hz] of the AC voltage is:
It has a value that is at least five times the process speed [mm / sec] of the image forming apparatus. In this image forming apparatus, when a bias for static elimination composed of an AC voltage is applied to the neutralizing member to positively neutralize the charge on the intermediate transfer member and contact the grounded conductive member for static elimination, The charge removal of the intermediate transfer member can be more reliably performed. In addition, since the AC voltage is controlled at a constant current, and the value of the frequency [Hz] of the AC voltage is five times or more the process speed [mm / sec] of the image forming apparatus, the intermediate transfer member at the time of static elimination is removed. Since the pitch of the above-mentioned potential fluctuation becomes short, it is possible to suppress the charge removal unevenness of the intermediate transfer body.

【0019】請求項12の発明は、請求項1の画像形成
装置において、上記除電用バイアスが、画像形成動作時
に帯電した上記中間転写体の帯電電位とは逆極性の直流
電圧と、定電流制御された交流電圧とを重畳したもので
あり、該交流電圧の周波数[Hz]の値が、画像形成装
置のプロセス速度[mm/sec]の5倍以上の値であ
ることを特徴とするものである。この画像形成装置で
は、交流電圧と上記所定極性の直流電圧とを重畳させた
除電用バイアスを上記除電部材に印加することにより、
中間転写体の帯電電荷を積極的に中和し、接地した導電
性部材を接触させて除電する場合に比してより確実に中
間転写体の除電を行うことができる。しかも、該交流電
圧が定電流制御され且つ該交流電圧の周波数[Hz]の
値が画像形成装置のプロセス速度[mm/sec]の5
倍以上の値であることにより、除電時の中間転写体上の
電位変動のピッチが短くなるので、該中間転写体の除電
ムラを抑制することができる。
According to a twelfth aspect of the present invention, in the image forming apparatus of the first aspect, the discharging bias is a DC voltage having a polarity opposite to a charging potential of the intermediate transfer member charged during an image forming operation, and a constant current control. Wherein the value of the frequency [Hz] of the AC voltage is at least five times the process speed [mm / sec] of the image forming apparatus. is there. In this image forming apparatus, by applying to the static elimination member a static elimination bias in which an AC voltage and the DC voltage having the predetermined polarity are superimposed,
The charge on the intermediate transfer member can be more positively neutralized, and the charge on the intermediate transfer member can be more reliably removed than when the grounded conductive member is contacted to remove the charge. In addition, the AC voltage is controlled at a constant current, and the value of the frequency [Hz] of the AC voltage is set to 5 times the process speed [mm / sec] of the image forming apparatus.
When the value is twice or more, the pitch of the potential change on the intermediate transfer member during the charge elimination is shortened, so that the charge elimination unevenness of the intermediate transfer member can be suppressed.

【0020】請求項13の発明は、像担持体上にトナー
像を形成し、該像担持体上のトナー像を中間転写体に一
次転写し、該中間転写体上のトナー像を更に転写材に二
次転写する画像形成方法において、画像形成動作後の非
画像形成時に、該画像形成動作時に帯電した上記中間転
写体の帯電電位とは逆極性の電荷を該中間転写体に付与
して該中間転写体を除電することを特徴とするものであ
る。この画像形成方法では、画像形成動作後の非画像形
成時に、該画像形成動作時に帯電した中間転写体の帯電
電位とは逆極性の電荷を該中間転写体に付与することに
より、該中間転写体の帯電電荷を積極的に中和し、接地
した導電性部材を接触させて除電する場合に比してより
確実に中間転写体の除電を行うことができる。
According to a thirteenth aspect of the present invention, a toner image is formed on an image carrier, the toner image on the image carrier is primarily transferred to an intermediate transfer member, and the toner image on the intermediate transfer member is further transferred to a transfer material. In the image forming method for secondary transfer, during non-image formation after the image forming operation, a charge having a polarity opposite to the charging potential of the intermediate transfer body charged during the image forming operation is applied to the intermediate transfer body to form the image. It is characterized in that the intermediate transfer member is neutralized. In this image forming method, during the non-image formation after the image forming operation, the intermediate transfer body is provided with a charge having a polarity opposite to the charging potential of the intermediate transfer body charged during the image forming operation, The neutralized charge of the intermediate transfer member can be more reliably removed as compared with the case where the charged charge is positively neutralized and the grounded conductive member is brought into contact with the charge to remove the charge.

【0021】[0021]

【発明の実施の形態】以下、本発明をカラー画像形成装
置に適用した実施形態について説明する。図1は本実施
形態に係るカラー画像形成装置の概略構成図である。図
1において、矢印の方向に回転する像担持体としてのド
ラム形状の感光体1の回りには、感光体クリーニングユ
ニット2、感光体を一様帯電する帯電手段としての帯電
器4、画像情報に応じて感光体1に光を照射する露光手
段としての露光ユニット5、感光体1上の静電潜像を現
像する現像手段、中間転写体としての中間転写ベルト1
0、などが配置されている。感光体1上にトナー像を形
成するトナー像形成手段は、上記帯電器4、上記露光手
段、上記現像手段などにより構成されている。
DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a color image forming apparatus will be described below. FIG. 1 is a schematic configuration diagram of a color image forming apparatus according to the present embodiment. In FIG. 1, a photoconductor cleaning unit 2, a charging device 4 as a charging unit for uniformly charging the photoconductor, a charging device 4 as a charging unit, and image information are provided around a drum-shaped photoconductor 1 as an image carrier that rotates in the direction of the arrow. Exposure unit 5 as an exposure means for irradiating light to photoreceptor 1 in accordance therewith, developing means for developing an electrostatic latent image on photoreceptor 1, intermediate transfer belt 1 as an intermediate transfer body
0, etc. are arranged. A toner image forming means for forming a toner image on the photoreceptor 1 includes the charger 4, the exposing means, the developing means, and the like.

【0022】上記現像手段は、イエロー現像器6、マゼ
ンタ現像器7、シアン現像器8、ブラック現像器9の4
個の現像器から構成される。フルカラー画像形成時はイ
エロー現像器6、マゼンタ現像器7、シアン現像器8、
ブラック現像器9の順でトナー像(可視像)を形成し、
各色のトナー像が中間転写ベルト10に順次重ね転写さ
れることでフルカラー画像が形成される。トナー像が中
間転写ベルト10に転写された後の感光体1の表面は、
感光体クリーニングユニット2のブレード3でクリーニ
ングされる。
The developing means includes a yellow developing device 6, a magenta developing device 7, a cyan developing device 8, and a black developing device 9.
It consists of developing units. When forming a full-color image, a yellow developing device 6, a magenta developing device 7, a cyan developing device 8,
A toner image (visible image) is formed in the order of the black developing device 9,
A full-color image is formed by sequentially superimposing and transferring the toner images of each color onto the intermediate transfer belt 10. The surface of the photoconductor 1 after the toner image is transferred to the intermediate transfer belt 10 is
The cleaning is performed by the blade 3 of the photoconductor cleaning unit 2.

【0023】上記中間転写ベルト10は、駆動ローラ1
3、ベルト転写バイアスローラ11、および従動ローラ
12a,12bにより張架されており、図示しない駆動
モータによって駆動されるようになっている。中間転写
ベルト10はPVDF(フッ化ビニルデン)、ETFE
(エチレン−四フッ化エチレン共重合体)、PI(ポリ
イミド)、PC(ポリカーボネート)等にカーボンブラ
ック等の導電性材料を分散させ、その体積抵抗率が10
〜1012Ωcm、かつ表面抵抗率が10〜10
15Ωcmの範囲となるよう調整されている。ここで、
上記体積抵抗率および表面抵抗率の測定は高抵抗抵抗率
計(三菱化学社製:ハイレスタIP)にHRSプローブ
(内側電極直径5.9mm、リング電極内径11mm)
を接続し、中間転写ベルト10の表裏に100V(表面
抵抗率は500V)の電圧を印加して10秒後の値を用
いた。中間転写ベルト10の体積抵抗率および表面抵抗
率が上記上限値を超えると、転写に必要な転写バイアス
が高くなるため、電源コストの増大を招く。また、中間
転写ベルト10の帯電電位が高くなるため除電工程を複
数回繰り返す必要が生じ、画像形成動作全体の時間が長
くなる、機械寿命が短くなるといった弊害をもたらす。
一方、中間転写ベルト10の体積抵抗率および表面抵抗
率が上記下限値を下回ると、帯電電位の減衰が早くなる
ため除電には有利となるが、転写時の電流が面方向に流
れるためトナー飛び散りが発生してしまう。
The intermediate transfer belt 10 includes a driving roller 1
3, it is stretched by a belt transfer bias roller 11, and driven rollers 12a, 12b, and is driven by a drive motor (not shown). The intermediate transfer belt 10 is made of PVDF (vinyl fluoride), ETFE
(Ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate) and the like, and a conductive material such as carbon black is dispersed.
8 to 10 12 Ωcm and a surface resistivity of 10 8 to 10
It is adjusted to be in the range of 15 Ωcm. here,
The volume resistivity and the surface resistivity were measured by using a high resistivity meter (manufactured by Mitsubishi Chemical Corporation: Hiresta IP) with an HRS probe (inner electrode diameter 5.9 mm, ring electrode inner diameter 11 mm).
Was connected, and a voltage of 100 V (surface resistivity: 500 V) was applied to the front and back of the intermediate transfer belt 10 and the value after 10 seconds was used. If the volume resistivity and the surface resistivity of the intermediate transfer belt 10 exceed the above upper limits, the transfer bias required for the transfer increases, which causes an increase in power supply cost. In addition, since the charging potential of the intermediate transfer belt 10 becomes high, it is necessary to repeat the charge elimination process a plurality of times, which causes a problem that the entire time of the image forming operation becomes long and the mechanical life becomes short.
On the other hand, if the volume resistivity and the surface resistivity of the intermediate transfer belt 10 are below the lower limits, the charge potential is rapidly attenuated, which is advantageous for static elimination. However, since the current at the time of transfer flows in the surface direction, toner scattering occurs. Will occur.

【0024】また、上記中間転写ベルト10の表面に
は、必要に応じて離型層をコートしてもよい。このコー
トに用いる材料としては、ETFE(エチレン−四フッ
化エチレン共重合体)、PTFE(ポリ四フッ化エチレ
ン)、PVDF(フッ化ビニルデン)、PEA(パ−フ
ルオロアルコキシフッ素樹脂)、FEP(四フッ化エチ
レン−六フッ化プロピレン共重合体)、PVF(フッ化
ビニル)等のフッ素樹脂が使用できるが、これらに限定
されるものではない。
The surface of the intermediate transfer belt 10 may be coated with a release layer if necessary. Materials used for this coating include ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinyldene fluoride), PEA (perfluoroalkoxy fluororesin), and FEP (four A fluororesin such as a fluoroethylene-propylene hexafluoride copolymer) or PVF (vinyl fluoride) can be used, but is not limited thereto.

【0025】上記中間転写ベルト10に接離可能なベル
トクリーニングユニット19は、クリーニングブレード
18、および該クリーニングブレード18を中間転写ベ
ルト10に対して接離させる接離機構26などで構成さ
れており、1色目のイエロー画像をベルト転写したあと
の、2、3、4色目をベルト転写している間は、上記接
離機構26によって中間転写ベルト10の表面から離間
させられる。上記接離機構26は、クリーニングブレー
ド18が感光体1の表面に当接するようにクリーニング
ユニット19を付勢する図示しない付勢手段と、クリー
ニングユニット19の揺動する底面部に当接した状態で
後述の制御部200で回転駆動される偏心カムを用いて
構成されている。また、中間転写ベルト10の外周面の
幅方向端部にはベルト位置検出マーク23が設けられて
おり、マークセンサ24によって該マーク23が検出さ
れたタイミングで各色の画像形成プロセスを開始するこ
とにより、各色画像の正確な色重ねが可能となる。
The belt cleaning unit 19 which can be brought into contact with and separated from the intermediate transfer belt 10 comprises a cleaning blade 18 and a contact / separation mechanism 26 for bringing the cleaning blade 18 into and out of contact with the intermediate transfer belt 10. After the first color yellow image is transferred to the belt, the second, third, and fourth colors are separated from the surface of the intermediate transfer belt 10 by the contact / separation mechanism 26 during the belt transfer. The contact / separation mechanism 26 includes an urging unit (not shown) that urges the cleaning unit 19 so that the cleaning blade 18 comes into contact with the surface of the photoconductor 1, and a state in which the cleaning blade 18 comes into contact with the swinging bottom surface of the cleaning unit 19. It is configured using an eccentric cam rotationally driven by a control unit 200 described later. Further, a belt position detection mark 23 is provided at an end in the width direction of the outer peripheral surface of the intermediate transfer belt 10, and an image forming process of each color is started at the timing when the mark 23 is detected by the mark sensor 24. Thus, accurate color superposition of each color image can be achieved.

【0026】二次転写ユニット15は、二次転写バイア
スローラ14、および該二次転写バイアスローラ14を
中間転写ベルト10に対して接離させる接離機構16な
どで構成されている。接離機構16は、二次転写バイア
スローラ14が中間転写ベルト10から離間するように
二次転写ユニット15を付勢する付勢手段としてのバネ
部材と、二次転写ユニット15の揺動する底面部に当接
した状態で後述の制御部200で回転駆動される偏心カ
ムとを用いて構成されている。二次転写バイアスローラ
14はSUS等の金属製芯金上に、導電性材料によって
10〜10 Ωの抵抗値に調整されたウレタン等の
弾性体を被覆することで構成されている。なお、上記二
次転写バイアスローラ14の抵抗値測定は、導電性の金
属製板に二次転写バイアスローラ14を設置し、芯金両
端部に片側4.9N(両側で合計9.8N)の荷重を掛
けた状態にて、芯金と上記金属製板との間に1000V
の電圧を印加したときに流れる電流値から算出した。こ
こで、上記二次転写バイアスローラ14の抵抗値が上記
上限値1010Ωを超えると電流が流れ難くなるため、
必要な転写性を得る為にはより高電圧を印加しなければ
ならなくなり、電源コストの増大を招く。また、高電圧
を印加するため二次転写ニップ前後の空隙にて放電が起
こる為、ハーフトーン画像上に放電による白ポチ抜けが
発生する。逆に、二次転写バイアスローラ14の抵抗値
が上記下限値10Ωを下回ると同一画像上に存在する
複数色画像部(例えば3色重ね像)と単色画像部との転
写性が両立できなくなる。これは、二次転写バイアスロ
ーラ14の抵抗値が低いため、比較的低電圧で単色画像
部を転写するのに十分な電流が流れるが、複数色画像部
を転写するには単色画像部に最適な電圧よりも高い電圧
値が必要となるためである。複数色画像部を転写できる
電圧に設定すると単色画像では転写電流が過剰となり転
写効率の低減を招いてしまう。
The secondary transfer unit 15 includes a secondary transfer bias roller 14 and a contact / separation mechanism 16 for bringing the secondary transfer bias roller 14 into and out of contact with the intermediate transfer belt 10. The contact / separation mechanism 16 includes a spring member as an urging unit for urging the secondary transfer unit 15 so that the secondary transfer bias roller 14 is separated from the intermediate transfer belt 10, and a swinging bottom surface of the secondary transfer unit 15. It is configured using an eccentric cam that is rotationally driven by a control unit 200 described below in a state of contact with the unit. The secondary transfer bias roller 14 on the metal core, such as SUS, is constituted by coating an elastic body such as urethane, which is adjusted to a resistance value of 10 5 ~10 1 0 Ω by a conductive material. The resistance value of the secondary transfer bias roller 14 was measured by installing the secondary transfer bias roller 14 on a conductive metal plate and placing 4.9 N on one side at both ends of the metal core (a total of 9.8 N on both sides). With a load applied, 1000 V between the metal core and the metal plate
Was calculated from the value of the current flowing when the voltage was applied. Here, if the resistance value of the secondary transfer bias roller 14 exceeds the upper limit value of 10 10 Ω, current hardly flows,
In order to obtain the necessary transferability, a higher voltage must be applied, resulting in an increase in power supply cost. In addition, since a high voltage is applied, discharge occurs in a gap before and after the secondary transfer nip, so that white spots occur due to the discharge on the halftone image. Conversely, if the resistance value of the secondary transfer bias roller 14 falls below the lower limit of 10 5 Ω, transferability between a multi-color image portion (for example, a three-color superimposed image) and a single-color image portion existing on the same image can be compatible. Disappears. This is because the resistance value of the secondary transfer bias roller 14 is low, so that a sufficient current flows to transfer a single-color image portion at a relatively low voltage, but it is most suitable for a single-color image portion to transfer a multi-color image portion. This is because a voltage value higher than the required voltage is required. If the voltage is set such that the multicolor image portion can be transferred, the transfer current becomes excessive in the case of a single-color image, and the transfer efficiency is reduced.

【0027】また、上記二次転写バイアスローラ14は
図示しない駆動ギヤによって駆動力が与えられており、
その周速は中間転写ベルト10の周速に対して、略同一
となるよう調整されている。また、上記二次転写バイア
スローラ14は通常中間転写ベルト10の表面から離間
しているが、中間転写ベルト10の表面に形成された4
色の重ね画像を転写材としての転写紙22に一括転写す
るときにタイミングを取って接離手段としての接離機構
16で押圧され、二次転写バイアス印加手段としての高
圧電源100により、二次転写バイアスローラ14に二
次転写バイアスを印加することにより、中間転写ベルト
10から転写紙22への転写を行う。ここで、図示しな
い温湿度センサーから得られる装置内の温湿度情報、転
写紙22の種類の情報(例えば普通紙かOHPシートかの
情報)、単色モードか複数色モードかの情報、両面印字
の場合の第一面印字時か第二面印字時かの情報等から、
所定のバイアスが選択される。
A driving force is applied to the secondary transfer bias roller 14 by a driving gear (not shown).
The peripheral speed is adjusted to be substantially the same as the peripheral speed of the intermediate transfer belt 10. The secondary transfer bias roller 14 is usually separated from the surface of the intermediate transfer belt 10, but the secondary transfer bias roller 14 is formed on the surface of the intermediate transfer belt 10.
When the color superimposed images are collectively transferred onto the transfer paper 22 as the transfer material, the images are pressed by the contact / separation mechanism 16 as the contact / separation means at a time, and the secondary power is applied by the high voltage power supply 100 as the secondary transfer bias applying means. The transfer from the intermediate transfer belt 10 to the transfer paper 22 is performed by applying a secondary transfer bias to the transfer bias roller 14. Here, temperature and humidity information in the apparatus obtained from a temperature and humidity sensor (not shown), information on the type of transfer paper 22 (for example, information on plain paper or OHP sheet), information on single-color mode or multi-color mode, and information on double-sided printing From the information on whether the first side printing or the second side printing in the case, etc.,
A predetermined bias is selected.

【0028】なお、上記高圧電源100は、図2に示す
ように、極性の異なる直流のバイアスを発生するバイア
ス発生部102と極性を切り替えるバイアス極性切替部
101とから構成されている。この高圧電源100のバ
イアス極性切替部101は、装置本体側に設けられたC
PUやI/Oインターフェースなどからなる制御手段と
しての制御部200に接続され、制御される。
As shown in FIG. 2, the high-voltage power supply 100 includes a bias generator 102 for generating DC biases having different polarities and a bias polarity switching unit 101 for switching the polarity. The bias polarity switching unit 101 of the high-voltage power supply 100 is connected to a C
It is connected to and controlled by a control unit 200 as a control means including a PU and an I / O interface.

【0029】上記構成のカラー画像形成装置において、
上記転写紙22は給紙ローラ25、レジストローラ21
によって、中間転写ベルト10上の4色重ね画像の先端
部が二次転写位置に到達するタイミングに合わせて給紙
される。転写紙22に転写された4色重ね画像は定着手
段17で定着された後、排紙される。複数色のカラー連
続プリント時には、転写紙22の後端が二次転写バイア
スローラ14を十分通過するタイミングで二次転写バイ
アスがオフされ、その後次ページの中間転写ベルト10
上トナーを付着させないために、接離機構16によって
中間転写ベルト10より離間される。また、単枚プリン
トあるいは連続プリント時の最終ページ終了時には二次
転写バイアスローラ14を中間転写ベルト10の表面か
ら離間させず、二次転写バイアスとは逆極性のクリーニ
ングバイアス(本実施形態では−1kV)を一定時間
(本実施形態では二次転写バイアスローラの4回転に相
当する時間)印加する。さらに続けて二次転写バイアス
と同極性のバイアス(本実施形態では1kV)を一定時
間(本実施形態では二次転写バイアスローラの2回転に
相当する時間)印加することで、二次転写バイアスロー
ラ14の表面に付着したトナーを中間転写ベルト10に
転移させ、二次転写バイアスローラ14表面に付着した
トナーのクリーニングを行なう。二次転写バイアスロー
ラ14から中間転写ベルト10に転移させられたトナー
は、ベルトクリーニングユニット19によって中間転写
ベルト10から回収される。
In the above-structured color image forming apparatus,
The transfer paper 22 includes a paper feed roller 25 and a registration roller 21.
As a result, the leading end of the four-color superimposed image on the intermediate transfer belt 10 is fed at the timing when it reaches the secondary transfer position. The four-color superimposed image transferred to the transfer paper 22 is fixed by the fixing unit 17 and then discharged. At the time of continuous printing of a plurality of colors, the secondary transfer bias is turned off at the timing when the rear end of the transfer paper 22 sufficiently passes through the secondary transfer bias roller 14, and then the intermediate transfer belt 10 of the next page is turned off.
In order to prevent the upper toner from adhering, the toner is separated from the intermediate transfer belt 10 by the contact and separation mechanism 16. Further, at the end of the last page in single-sheet printing or continuous printing, the secondary transfer bias roller 14 is not separated from the surface of the intermediate transfer belt 10, and a cleaning bias having a polarity opposite to that of the secondary transfer bias (-1 kV in the present embodiment). ) Is applied for a predetermined time (in this embodiment, a time corresponding to four rotations of the secondary transfer bias roller). Subsequently, a bias having the same polarity as the secondary transfer bias (1 kV in the present embodiment) is applied for a predetermined time (a time corresponding to two rotations of the secondary transfer bias roller in the present embodiment), whereby the secondary transfer bias roller is applied. The toner attached to the surface of the secondary transfer roller 14 is transferred to the intermediate transfer belt 10, and the toner attached to the surface of the secondary transfer bias roller 14 is cleaned. The toner transferred from the secondary transfer bias roller 14 to the intermediate transfer belt 10 is collected from the intermediate transfer belt 10 by the belt cleaning unit 19.

【0030】図3は、上記構成のカラー画像形成装置に
おいて、画像形成動作終了後、装置停止状態にて一時間
以上放置し、その後再び画像形成動作を開始した直後の
上記露光手段による露光前の感光体1の表面電位を測定
したものである。図中のV は感光体1と中間転写ベ
ルト10との非接触部の表面電位であり、VH2が感光
体1と中間転写ベルト10との接触部の表面電位に相当
する。この図3からも分かるように、上記接触部の表面
電位VH2が、上記非接触部に比べ、下がっている。こ
れは、画像形成動作中に帯電した中間転写ベルト10の
帯電電荷が感光体1に電荷注入されたことによると考え
られる。
FIG. 3 shows the color image forming apparatus having the above-described structure, after the image forming operation is completed, left for one hour or more in a stopped state of the apparatus, and then immediately before starting the image forming operation again before the exposure by the exposure means. The surface potential of the photoconductor 1 was measured. V H 1 in the figure is the surface potential of the non-contact portion between the photosensitive member 1 and the intermediate transfer belt 10, V H2 is equivalent to the surface potential of the contact portion between the photosensitive member 1 and the intermediate transfer belt 10. As can be seen from FIG. 3, the surface potential V H2 of the contact portion is lower than that of the non-contact portion. It is considered that this is because the charged charge of the intermediate transfer belt 10 charged during the image forming operation was injected into the photosensitive member 1.

【0031】図4は、前述した図3の状態にある感光体
1にハーフトーン画像を露光した後の感光体1の表面電
位の状態を示すものである。ハーフトーン画像に相当す
る表面電位VH1′に比べ、感光体1と中間転写ベルト
10との接触部ではVH2′となっており、電位差が生
じている。この状態において画像形成を行なうと、図5
に示すように、ハーフトーン画像上において、感光体1
と中間転写ベルト10との接触部にて「ハーフトーン上
横帯」が発生した。
FIG. 4 shows a state of the surface potential of the photoconductor 1 after the halftone image is exposed on the photoconductor 1 in the state of FIG. 3 described above. Compared to the surface potential V H1 ′ corresponding to the halftone image, the contact portion between the photoconductor 1 and the intermediate transfer belt 10 is V H2 ′, and a potential difference is generated. When image formation is performed in this state, FIG.
As shown in FIG.
A "halftone upper horizontal band" occurred at a contact portion between the belt and the intermediate transfer belt 10.

【0032】図6は、普通紙、複数色モード、第一面印
字での条件にて、二次転写バイアスローラ14に印加す
る二次転写バイアス(本実施形態では定電流制御)の電
流値ITRと、画像形成動作停止時における感光体1と
中間転写ベルト10との接触部近傍の中間転写ベルト1
0の帯電電位VT1との関係を、各温湿度環境別(L/
L、N/N、H/H)に示したものである。ここで、
「L/L」は10°C、15%、「N/N」は23°
C、65%、「H/H」は30°C、90%の温湿度条
件を示している。この図6から理解できるように、二次
転写ローラ14に印加する二次転写バイアスの電流値I
TRが高ければ高いほど、また温湿度は低温低湿である
ほど中間転写ベルト10の帯電電位は高くなる。
FIG. 6 shows the current value I of the secondary transfer bias (constant current control in this embodiment) applied to the secondary transfer bias roller 14 under the conditions of plain paper, multi-color mode, and first-side printing. TR , the intermediate transfer belt 1 near the contact portion between the photoconductor 1 and the intermediate transfer belt 10 when the image forming operation is stopped.
The relationship between the charging potential VT1 of 0 and the temperature / humidity environment (L /
L, N / N, H / H). here,
“L / L” is 10 ° C, 15%, “N / N” is 23 °
C, 65%, and “H / H” indicate temperature and humidity conditions of 30 ° C. and 90%. As can be understood from FIG. 6, the current value I of the secondary transfer bias applied to the secondary transfer roller 14
The higher the TR, the lower the temperature and humidity, and the lower the temperature and humidity, the higher the charging potential of the intermediate transfer belt 10.

【0033】図7は、温湿度条件を上記「N/N」に固
定して他の画像形成条件を変化させた場合における、二
次転写ローラ14に印加する二次転写バイアスの電流値
と、画像形成動作停止時における感光体1と中間
転写ベルト10との接触部近傍の中間転写ベルト10帯
電電位VT1との関係を示したものである。この図7か
ら理解できるように、単色モードよりも複数色モードの
方が、二次転写の回数が多くしかもトナー像の重ね合わ
せに応じて二次転写バイアスの大きさを大きくしている
ため、中間転写ベルト10の帯電電位VT1は高くな
る。また、両面印字における第一面印字時よりも第二面
印字時の方が、1度定着工程を通過して乾燥していると
ともにトナーを既に担持しているため、中間転写ベルト
10の帯電電位VT1は高くなる。さらに、普通紙より
もOHPシートの方が、抵抗率が高いため、中間転写ベル
ト10の帯電電位VT1は高くなる。したがって、前述
した各画像形成条件(温湿度、転写紙の種類、単色モー
ドか複数色モードか、両面印字における第一面印字か第
二面印字か)の情報を画像形成時にあらかじめ認識して
おくことで、特別な帯電電位測定手段を具備しなくて
も、中間転写ベルト10の帯電電位VT1を予測するこ
とが可能となる。これらの画像形成条件に基づいて、中
間転写ベルト10の除電のときに二次転写バイアスロー
ラに印加する2次転写バイアスを制御することにより、
該画像形成条件が変わった場合でも、中間転写ベルト1
0を確実に除電することができる。
[0033] Figure 7, in the case of changing the other image forming conditions temperature and humidity conditions is fixed to the "N / N", the current value of the secondary transfer bias applied to the secondary transfer roller 14 I T and R, shows the relationship between the intermediate transfer belt 10 charged potential V T1 of the contact portion near the photosensitive member 1 and the intermediate transfer belt 10 during image forming operation is stopped. As can be understood from FIG. 7, in the multi-color mode, the number of times of the secondary transfer is larger than in the single-color mode, and the magnitude of the secondary transfer bias is increased in accordance with the superposition of the toner images. The charging potential VT1 of the intermediate transfer belt 10 increases. Further, in the double-sided printing, the second-side printing is dried once after passing through the fixing process and has already carried the toner, and therefore, the charged potential of the intermediate transfer belt 10 is higher in the second-side printing than in the first-side printing. VT1 will be high. Furthermore, since the OHP sheet has a higher resistivity than plain paper, the charging potential VT1 of the intermediate transfer belt 10 is higher. Therefore, information on the above-described image forming conditions (temperature and humidity, type of transfer paper, single-color mode or multiple-color mode, first-side printing or second-side printing in double-sided printing) is recognized in advance during image formation. This makes it possible to predict the charging potential VT1 of the intermediate transfer belt 10 without providing any special charging potential measuring means. By controlling the secondary transfer bias applied to the secondary transfer bias roller at the time of neutralization of the intermediate transfer belt 10 based on these image forming conditions,
Even if the image forming conditions change, the intermediate transfer belt 1
0 can be reliably eliminated.

【0034】図8は、除電後の中間転写ベルト10の帯
電電位VT2と上記「ハーフトーン上横帯」との関係を
示すグラフである。図8中の斜線部がハーフトーン上横
帯未発生領域であり、中間転写ベルト10の帯電電位V
T2と感光体1の表面電位V H1との関係が不等式V
T2≦0.5×VH1を満足する領域である。
FIG. 8 shows the belt of the intermediate transfer belt 10 after the charge is removed.
Electric potential VT2And the relationship between the above "halftone upper horizontal band"
It is a graph shown. The shaded area in FIG.
This is an area where no belt is generated, and the charged potential V of the intermediate transfer belt 10 is
T2And surface potential V of photoconductor 1 H1Is the inequality V
T2≦ 0.5 × VH1Is an area that satisfies

【0035】図9は、中間転写ベルト10の帯電電位V
T1と、二次転写バイアスローラ14への除電用バイア
スVTRと、除電後の中間転写ベルト10の帯電電位V
T2との関係を示したものである。なお、本実施形態で
は除電時の印加バイアスV としてDCバイアスを用
いた。前述した各条件の情報から得られた中間転写ベル
ト10の帯電電位の予測値を、図9のVT1に当てはめ
ることによって、二次転写バイアスローラ14への除電
用バイアス値VTRおよび除電後の中間転写ベルト10
の帯電電位VT2とが求められる。
FIG. 9 shows the charged potential V of the intermediate transfer belt 10.
And T1, and the charge removing bias V TR to the secondary transfer bias roller 14, the charge potential of the intermediate transfer belt 10 after neutralization V
It shows the relationship with T2 . Incidentally, a DC bias as the bias applied V T R during neutralization in this embodiment. The predicted value of the charging potential of the intermediate transfer belt 10 obtained from the information of the conditions described above, by fitting the V T1 in FIG. 9, charge removing bias value V TR, and after neutralization of the secondary transfer bias roller 14 Intermediate transfer belt 10
And the charge potential V T2 is required.

【0036】図10は、二次転写バイアスローラ14へ
の除電用バイアスVTRの印加タイミングを示すタイミ
ングチャートである。最終ページ終了後、二次転写バイ
アスローラ14を中間転写ベルト10面から離間させ
ず、二次転写バイアスとは逆極性のクリーニングバイア
スおよび、二次転写バイアスと同極性のバイアスをそれ
ぞれ所定の時間印加し、二次転写バイアスローラ14の
クリーニングを行なった後、二次転写バイアスローラ1
4への印加バイアスを除電用バイアスVTRに切り替
え、少なくとも装置停止時に中間転写ベルト10が感光
体1と接触している範囲を除電したのち、メインモータ
ーが停止するようにした。このように制御することで、
特別に除電手段を設けること無く、画像形成動作終了
後、一定時間以上放置しても上記「ハーフトーン上横
帯」の発生しない良好な画像が得られた。
[0036] FIG. 10 is a timing chart showing application timing of charge removing bias V TR to the secondary transfer bias roller 14. After the last page is completed, the secondary transfer bias roller 14 is not separated from the surface of the intermediate transfer belt 10 and a cleaning bias having a polarity opposite to the secondary transfer bias and a bias having the same polarity as the secondary transfer bias are applied for a predetermined time. After the secondary transfer bias roller 14 is cleaned, the secondary transfer bias roller 1
The bias applied to the 4 switches to charge removing bias V TR, After neutralization the range in which the intermediate transfer belt 10 is in contact with the photosensitive member 1 at least stopping the apparatus, the main motor is to stop. By controlling in this way,
A good image free of the above-mentioned "halftone upper horizontal band" was obtained even after leaving the image forming operation for a certain period of time after the completion of the image forming operation, without providing any special charge removing means.

【0037】なお、上記実施形態では、二次転写バイア
スローラ14のクリーニングをバイアス印加によって行
なっているが、図11に示すように二次転写バイアスロ
ーラ14の表面にクリーニングブレード30を当接し、
該二次転写バイアスローラ14の表面のクリーニングを
行なうようにしてもよい。図12は、上記クリーニング
ブレード30を用いる場合の二次転写バイアスローラ1
4への除電用バイアスVTRの印加タイミングを示すタ
イミングチャートである。最終ページ終了後、二次転写
バイアスローラ14を中間転写ベルト10の表面から離
間させず、二次転写バイアスローラ14への印加バイア
スを除電用バイアスVTRに切り替え、少なくとも装置
停止時に中間転写ベルト10が感光体1と接触している
範囲を除電したのち、メインモーターが停止するように
した。このように制御することで、特別に除電手段を設
けること無く、画像形成動作終了後、一定時間以上放置
しても上記「ハーフトーン上横帯」の発生しない良好な
画像が得られた。
In the above-described embodiment, the cleaning of the secondary transfer bias roller 14 is performed by applying a bias. However, as shown in FIG. 11, the cleaning blade 30 is brought into contact with the surface of the secondary transfer bias roller 14,
The surface of the secondary transfer bias roller 14 may be cleaned. FIG. 12 shows the secondary transfer bias roller 1 when the cleaning blade 30 is used.
It is a timing chart showing application timing of charge removing bias V TR to 4. After completion of the final page, without separating the secondary transfer bias roller 14 from the surface of the intermediate transfer belt 10, switching the bias applied to the secondary transfer bias roller 14 to the charge removing bias V TR, the intermediate transfer belt 10 at least stopping the apparatus After the charge was removed from the area in contact with the photoreceptor 1, the main motor was stopped. By controlling in this way, a good image free of the above-mentioned "halftone upper horizontal band" was obtained even after leaving the image forming operation for a certain period of time after the completion of the image forming operation without specially providing a static eliminator.

【0038】また、上記実施形態では、除電用バイアス
TRとしてDCバイアス(直流電圧)を用いている
が、DCバイアス(直流電圧)とACバイアス(交流電
圧)とを重畳させたものを用いてもよい。この場合、重
畳させるACバイアスは定電流で制御され、その周波数
[Hz]は画像形成装置のプロセス速度[mm/se
c]の5倍以上、好ましくはプロセス速度の7倍以上と
した。これは、周波数がプロセス速度の5倍を下回る
と、除電効果にピッチムラが起こるため、上記「ハーフ
トーン上横帯」がわずかに発生してしまうためである。
このように制御することで、特別に除電手段を設けるこ
と無く、画像形成動作終了後、一定時間以上放置しても
ハーフトーン上横帯の発生しない良好な画像が得られ
た。
[0038] In the above embodiment uses a DC bias (DC voltage) as charge removing bias V TR, with those obtained by superimposing the DC bias (DC voltage) and AC bias (AC voltage) Is also good. In this case, the AC bias to be superimposed is controlled by a constant current, and the frequency [Hz] is the process speed [mm / sec] of the image forming apparatus.
c] or more, and preferably 7 times or more the process speed. This is because when the frequency is lower than 5 times the process speed, pitch unevenness occurs in the static elimination effect, so that the above "halftone upper horizontal band" is slightly generated.
By performing such control, a good image in which no horizontal band occurs on the halftone even when the image forming operation is completed for a certain period of time or longer after the image forming operation is completed can be obtained without providing any static eliminator.

【0039】また、上記除電用バイアスVTRとして、
ACバイアス(交流電圧)を用いてもよい。この場合、
上記ACバイアス(交流電圧)は定電流で制御され、そ
の周波数[Hz=cycle/sec]は画像形成装置
のプロセス速度[mm/sec]の5倍以上、好ましく
はプロセス速度の7倍以上とした。これは、周波数がプ
ロセス速度の5倍を下回ると、除電効果にピッチムラ
(例えば1mmあたり4周期の電位変動ムラ)が起こる
ため、人間の目に目立つ画像ムラ(ハーフトーン上横
帯)がわずかに発生してしまうためである。このように
制御することで、特別に除電手段を設けること無く、画
像形成動作終了後、一定時間以上放置してもハーフトー
ン上横帯の発生しない良好な画像が得られた。
[0039] In addition, as the charge removing bias V TR,
An AC bias (AC voltage) may be used. in this case,
The AC bias (AC voltage) is controlled by a constant current, and the frequency [Hz = cycle / sec] is set to 5 times or more, preferably 7 times or more the process speed [mm / sec] of the image forming apparatus. . This is because, when the frequency is lower than 5 times the process speed, pitch unevenness (for example, potential fluctuation unevenness of 4 cycles per 1 mm) occurs in the static elimination effect, so that image unevenness (horizontal band on the halftone) noticeable to human eyes is slightly increased. This is because it occurs. By performing such control, a good image in which no horizontal band occurs on the halftone even when the image forming operation is completed for a certain period of time or longer after the image forming operation is completed can be obtained without providing any static eliminator.

【0040】また、上記実施形態では二次転写部材とし
てローラ形状の二次転写バイアスローラ14を用いてい
るが、該ローラ14の代わりに、図13に示すような複
数の支持ローラ32、33に掛け渡されたベルト形状の
二次転写ベルト31を用いてもよい。この構成の場合、
二次転写バイアスは、二次転写ベルト31を介して上記
従動ローラ12bに圧接対向する対向ローラ34から印
加される。この構成によれば、転写紙22の搬送性が良
好で、特別に除電手段を設けること無く、画像形成動作
終了後、一定時間以上放置してもハーフトーン上横帯の
発生しない良好な画像が得られた。
In the above-described embodiment, the roller-shaped secondary transfer bias roller 14 is used as the secondary transfer member. Instead of the roller 14, a plurality of support rollers 32 and 33 as shown in FIG. A secondary transfer belt 31 having a belt shape that has been stretched may be used. In this configuration,
The secondary transfer bias is applied from an opposing roller 34 that is in pressure contact with the driven roller 12b via the secondary transfer belt 31. According to this configuration, it is possible to obtain a good image in which the transfer property of the transfer paper 22 is good, and no horizontal band is generated even when the image forming operation is left for a certain period of time after completion of the image forming operation. Obtained.

【0041】また、上記実施形態では、像担持体として
感光体ドラムを用いた場合について説明したが、本発明
はこれに限定されるものではなく、感光体ベルト等、全
ての像担持体に適用可能である。また、上記実施形態で
は、中間転写体として中間転写ベルトを用いて説明した
が、本発明はこれに限定されるものではなく、中間転写
ドラム、高抵抗フィルム等の中間転写体等、全ての中間
転写体に適用可能である。さらに、二次転写バイアスを
定電流制御としたが、定電圧制御としても良い。さら
に、転写手段として転写ローラおよび転写ベルトを用い
たが、回転型転写ブラシなどの回転型接触転写方式はも
ちろんのこと、転写ブラシ、転写ブレード、転写プレー
トなどの接触転写方式を用いた画像形成装置であれば、
本発明を適用可能である。
In the above embodiment, the case where a photosensitive drum is used as an image carrier has been described. However, the present invention is not limited to this, and is applicable to all image carriers such as a photosensitive belt. It is possible. Further, in the above embodiment, the description has been made using the intermediate transfer belt as the intermediate transfer body. However, the present invention is not limited to this, and all intermediate transfer members such as an intermediate transfer drum, an intermediate transfer body such as a high-resistance film, etc. Applicable to transcripts. Further, the secondary transfer bias is controlled by the constant current, but may be controlled by the constant voltage. Further, a transfer roller and a transfer belt are used as transfer means, but an image forming apparatus using a contact transfer method such as a transfer brush, a transfer blade, and a transfer plate, as well as a rotary contact transfer method such as a rotary transfer brush. If,
The present invention is applicable.

【0042】[0042]

【発明の効果】請求項1乃至13の発明によれば、画像
形成時に帯電した中間転写体の帯電電荷を積極的に中和
することにより、接地した導電性部材を接触させて除電
する場合に比してより確実に中間転写体の除電を行うこ
とができるという効果がある。
According to the first to thirteenth aspects of the present invention, the charge is neutralized positively on the intermediate transfer member during image formation, so that the grounded conductive member is brought into contact with the intermediate transfer member to eliminate the charge. As a result, there is an effect that the charge removal of the intermediate transfer member can be performed more reliably.

【0043】特に、請求項2の発明によれば、画像形成
動作終了時に上記像担持体が接触していた上記帯電が発
生しやすい領域の除電を確実に行うことができるという
効果がある。
In particular, according to the second aspect of the present invention, there is an effect that static electricity can be reliably removed from an area where the image carrier is in contact with the image carrier when the image forming operation is completed.

【0044】また特に、請求項3の発明によれば、一様
帯電された像担持体の表面電位が互いに異なる条件下に
おいても、「ハーフトーン上横帯」という現象を防止で
きるという効果がある。
In particular, according to the third aspect of the invention, there is an effect that the phenomenon of "horizontal band on halftone" can be prevented even under the condition that the surface potentials of uniformly charged image carriers are different from each other. .

【0045】また特に、請求項4及び5の発明によれ
ば、画像形成条件が変わる場合でも上記中間転写体の除
電を確実に行うことが可能となるという効果がる。
In particular, according to the fourth and fifth aspects of the present invention, there is an effect that even when the image forming conditions are changed, it is possible to reliably perform the charge elimination of the intermediate transfer body.

【0046】また特に、請求項5の発明によれば、転写
材の種類、装置内の温度及び湿度、並びに上記中間転写
体へのトナー像の重ね合わせ数の少なくとも一つによっ
て中間転写体の帯電電位が変わる場合でも上記中間転写
体の除電を確実に行うことが可能となるという効果があ
る。
In particular, according to the fifth aspect of the present invention, the charging of the intermediate transfer member is performed by at least one of the type of the transfer material, the temperature and humidity in the apparatus, and the number of superimposed toner images on the intermediate transfer member. Even when the potential changes, there is an effect that the neutralization of the intermediate transfer member can be reliably performed.

【0047】また特に、請求項6の発明によれば、除電
部材及び除電用バイアス印加手段として二次転写部材及
び二次転写用バイアス印加手段を兼用できるので、除電
部材及び除電用バイアス印加手段を個別に設けることな
く、中間転写体を確実に除電できるという効果がある。
In particular, according to the invention of claim 6, since the secondary transfer member and the secondary transfer bias applying means can be used as the charge eliminating member and the bias applying means for charge eliminating, the charge eliminating member and the bias applying means for charge eliminating can be used. There is an effect that static electricity can be reliably removed from the intermediate transfer member without providing them separately.

【0048】また特に、請求項7及び8の発明によれ
ば、中間転写体へのトナー像の重ね合わせの数が多い場
合に合わせて二次転写バイアスを設定しても、トナー像
の重ね合わせがないときの転写効率の低下を防止でき
る。しかも、良好な転写性を得るための二次転写バイア
スが過剰に高くなるのを抑制し、二次転写バイアス印加
手段のコスト上昇を抑えるとともに、二次転写ニップ前
後の空隙における放電の発生を抑え、ハーフトーン画像
上に放電による「白ポチ抜け」という画像異常を防止す
ることができるという効果がある。
In particular, according to the seventh and eighth aspects of the present invention, even when the secondary transfer bias is set in accordance with the case where the number of superimposed toner images on the intermediate transfer member is large, the superimposition of the toner images can be performed. The transfer efficiency can be prevented from lowering when there is no image. Moreover, the secondary transfer bias for obtaining good transferability is suppressed from becoming excessively high, the cost of the secondary transfer bias applying unit is suppressed from increasing, and the generation of discharge in the gap before and after the secondary transfer nip is suppressed. In addition, there is an effect that an image abnormality such as "white spot missing" due to electric discharge can be prevented on a halftone image.

【0049】また特に、請求項9の発明によれば、像担
持体から中間転写体へのトナー像の転写時に該中間転写
体の表面に沿って転写電流が流れるのを抑制し、該表面
に沿った転写電流によるトナーの飛び散りを防止するこ
とができる。しかも、像担持体から中間転写体へのトナ
ー像の転写に必要な一次転写バイアスを低く抑え、一次
転写バイアス印加手段のコスト上昇を抑えることができ
るとともに、画像形成動作時に帯電する該中間転写体の
帯電電位を低く抑え、該中間転写体の除電を容易にする
ことができるという効果がある。
According to the ninth aspect of the present invention, the transfer of a transfer current along the surface of the intermediate transfer member during transfer of the toner image from the image bearing member to the intermediate transfer member is suppressed. The scattering of the toner due to the transfer current along the direction can be prevented. In addition, the primary transfer bias required for transferring the toner image from the image carrier to the intermediate transfer body can be suppressed low, the cost of the primary transfer bias applying unit can be suppressed, and the intermediate transfer body charged during the image forming operation can be suppressed. Has an effect that the charge potential of the intermediate transfer member can be suppressed to be low, and the neutralization of the intermediate transfer member can be easily performed.

【0050】また特に、請求項10の発明によれば、交
流電源に比してより簡易に構成することができる直流電
源で、中間転写体の除電を確実に行うことができるとい
う効果がる。
In particular, according to the tenth aspect of the present invention, there is an effect that the static electricity removal of the intermediate transfer member can be reliably performed with a DC power supply that can be more simply configured than an AC power supply.

【0051】また特に、請求項11及び12の発明によ
れば、中間転写体の除電ムラを抑制することができると
いう効果がある。
In particular, according to the eleventh and twelfth aspects of the present invention, there is an effect that it is possible to suppress the charge removal unevenness of the intermediate transfer member.

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

【図1】本発明の実施形態に係るカラー画像形成装置の
概略構成図。
FIG. 1 is a schematic configuration diagram of a color image forming apparatus according to an embodiment of the present invention.

【図2】同カラー画像形成装置の2次転写バイアス用の
高圧電源の概略構成図。
FIG. 2 is a schematic configuration diagram of a high-voltage power supply for a secondary transfer bias of the color image forming apparatus.

【図3】同カラー画像形成装置を停止状態で一時間以上
放置した後、再び画像形成動作を開始した直後におけ
る、露光前の感光体表面電位の測定結果を示すグラフ。
FIG. 3 is a graph showing a measurement result of a photoconductor surface potential before exposure immediately after the image forming operation is started again after the color image forming apparatus is left in a stopped state for one hour or more.

【図4】図3の状態にある感光体にハーフトーン画像を
露光した後の感光体表面電位の測定結果を示すグラフ。
FIG. 4 is a graph showing a measurement result of a photoconductor surface potential after exposing a halftone image to the photoconductor in the state of FIG. 3;

【図5】転写紙に形成されたハーフトーン画像における
「ハーフトーン上横帯」の説明図。
FIG. 5 is an explanatory diagram of “halftone upper horizontal band” in a halftone image formed on transfer paper.

【図6】二次転写バイアスの電流値ITRと中間転写ベ
ルトの帯電電位VT1との関係を示すグラフ。
Figure 6 is a graph showing the relationship between the charge potential V T1 of the current I TR and the intermediate transfer belt of the secondary transfer bias.

【図7】二次転写バイアスの電流値ITRと中間転写ベ
ルトの帯電電位VT1との関係を示すグラフ。
Figure 7 is a graph showing a relationship between the charge potential V T1 of the current I TR and the intermediate transfer belt of the secondary transfer bias.

【図8】感光体表面電位VH1と中間転写ベルトの除電
後帯電電位VT2との関係を示すグラフ。
8 is a graph showing the relationship between neutralizing the charged potential V T2 of the photosensitive member surface potential V H1 and the intermediate transfer belt.

【図9】二次転写バイアスの電流値ITRと中間転写ベ
ルトの帯電電位VT1及び除電後帯電電位VT2との関
係を示すグラフ。
9 is a graph showing the relationship between the charge potential V T1 and neutralizing the charged potential V T2 of the current value I TR and the intermediate transfer belt of the secondary transfer bias.

【図10】二次転写バイアスローラへの除電用バイアス
TRの印加タイミングを示すタイミングチャート。
Figure 10 is a timing chart showing application timing of charge removing bias V TR to the secondary transfer bias roller.

【図11】変形例に係る二次転写バイアスローラのクリ
ーニングを説明するための説明図。
FIG. 11 is an explanatory diagram for explaining cleaning of a secondary transfer bias roller according to a modification.

【図12】同変形例における二次転写バイアスローラへ
の除電用バイアスVTRの印加タイミングを示すタイミ
ングチャート。
Figure 12 is a timing chart showing application timing of charge removing bias V TR to the secondary transfer bias roller in the modification.

【図13】同変形例における二次転写バイアスローラへ
の除電用バイアスVTRの印加タイミングを示すタイミ
ングチャート。
Figure 13 is a timing chart showing application timing of charge removing bias V TR to the secondary transfer bias roller in the modification.

【符号の説明】[Explanation of symbols]

1 感光体 4 帯電器 5 露光ユニット 6 イエロー現像器 7 マゼンタ現像器 8 シアン現像器 9 ブラック現像器 10 中間転写ベルト 11 ベルト転写バイアスローラ 14 二次転写バイアスローラ 15 二次転写ユニット 16 接離機構 100 高圧電源 101 バイアス極性切替部101 102 バイアス発生部 200 制御部 REFERENCE SIGNS LIST 1 photoconductor 4 charging device 5 exposure unit 6 yellow developing device 7 magenta developing device 8 cyan developing device 9 black developing device 10 intermediate transfer belt 11 belt transfer bias roller 14 secondary transfer bias roller 15 secondary transfer unit 16 contact / separation mechanism 100 High voltage power supply 101 Bias polarity switching unit 101 102 Bias generation unit 200 Control unit

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 FI テーマコート゛(参考) G03G 21/14 G03G 21/00 372 Fターム(参考) 2H027 DA11 DA14 DC02 DE01 DE07 DE09 EA03 EA08 EA10 EB04 EC06 EC09 ED15 ED24 ED26 JA19 JC03 JC11 2H030 AD02 AD17 BB02 BB23 BB32 BB42 BB46 BB54 2H032 AA05 AA15 BA02 BA05 BA09 BA12 BA13 BA23 BA29 CA02 CA12 CA14 CA15 ──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. 7 Identification symbol FI Theme coat ゛ (Reference) G03G 21/14 G03G 21/00 372 F term (Reference) 2H027 DA11 DA14 DC02 DE01 DE07 DE09 EA03 EA08 EA10 EB04 EC06 EC09 ED15 ED24 ED26 JA19 JC03 JC11 2H030 AD02 AD17 BB02 BB23 BB32 BB42 BB46 BB54 2H032 AA05 AA15 BA02 BA05 BA09 BA12 BA13 BA23 BA29 CA02 CA12 CA14 CA15

Claims (13)

【特許請求の範囲】[Claims] 【請求項1】像担持体と、該像担持体上にトナー像を形
成するトナー像形成手段と、該像担持体上のトナー像が
転写される中間転写体と、該像担持体上のトナー像を該
中間転写体に一次転写する一次転写手段と、該中間転写
体上のトナー像を転写材に二次転写する二次転写手段と
を備えた画像形成装置において、 上記中間転写体に対して接離可能に配置された該中間転
写体を除電するための除電部材と、 該中間転写体に対して該除電部材を接離させる接離手段
と、 画像形成動作時に帯電した該中間転写体の帯電電荷を除
去するための除電用バイアスを該除電部材に印加する除
電用バイアス印加手段とを設けたことを特徴とする画像
形成装置。
An image carrier, a toner image forming means for forming a toner image on the image carrier, an intermediate transfer member to which a toner image on the image carrier is transferred, and An image forming apparatus comprising: primary transfer means for primary-transferring a toner image to the intermediate transfer member; and secondary transfer means for secondary-transferring the toner image on the intermediate transfer member to a transfer material. A static elimination member for static elimination of the intermediate transfer member disposed so as to be capable of contacting and separating from the intermediate transfer member; contacting and separating means for contacting and separating the static elimination member from and to the intermediate transfer member; and the intermediate transfer charged during an image forming operation. An image forming apparatus comprising: a charge removing bias applying unit that applies a charge removing bias for removing a charge on a body to the charge removing member.
【請求項2】請求項1の画像形成装置において、 上記除電用バイアスが印加された上記除電部材が接触す
る上記中間転写体の表面上の領域が、画像形成動作終了
時に上記像担持体が接触していた領域を含むことを特徴
とする画像形成装置。
2. An image forming apparatus according to claim 1, wherein an area on the surface of said intermediate transfer member which contacts said charge removing member to which said charge removing bias is applied contacts said image carrier at the end of image forming operation. An image forming apparatus comprising:
【請求項3】上記トナー像形成手段を、上記像担持体の
表面を一様帯電する帯電手段と、該像担持体の一様帯電
された表面を露光して潜像を形成する露光手段と、該像
担持体上の潜像を現像してトナー像を形成する現像手段
とを用いて構成した請求項1の画像形成装置であって、 上記除電手段で除電された後の上記中間転写体の表面電
位の絶対値をVT2とし、上記帯電手段で一様帯電され
た上記像担持体の表面電位の絶対値をVH1としたと
き、 VT2≦0.5×VH1 を満足することを特徴とする画像形成装置。
A charging unit for uniformly charging the surface of the image carrier; and an exposing unit for exposing the uniformly charged surface of the image carrier to form a latent image. 2. An image forming apparatus according to claim 1, wherein said intermediate transfer body after being discharged by said discharging means is constituted by using developing means for developing a latent image on said image carrier to form a toner image. and the absolute value of the surface potential and V T2, when the absolute value of the surface potential of the uniformly charged the image carrier by the charging means is a V H1, satisfies the V T2 ≦ 0.5 × V H1 An image forming apparatus comprising:
【請求項4】請求項1の画像形成装置において、 画像形成条件に基づいて上記除電部材に印加する除電用
バイアスを変更するように、上記除電用バイアス印加手
段を制御する制御手段を設けたことを特徴とする画像形
成装置。
4. The image forming apparatus according to claim 1, further comprising control means for controlling said biasing means for applying static electricity so as to change a bias for applying static electricity to said electricity removing member based on image forming conditions. An image forming apparatus comprising:
【請求項5】請求項4の画像形成装置において、 上記画像形成動作時の条件が、転写材の種類、装置内の
温度及び湿度、並びに上記中間転写体へのトナー像の重
ね合わせ数の少なくとも一つであることを特徴とする画
像形成装置。
5. The image forming apparatus according to claim 4, wherein the conditions at the time of the image forming operation include at least a kind of a transfer material, a temperature and a humidity in the apparatus, and a number of superimposed toner images on the intermediate transfer body. An image forming apparatus, wherein the number is one.
【請求項6】上記二次転写手段を、上記転写材を介して
上記中間転写体に接離可能に配設された二次転写部材
と、該二次転写部材に二次転写用バイアスを印加する二
次転写用バイアス印加手段とを用いて構成した請求項1
の画像形成装置であって、 上記除電部材として上記二次転写部材を兼用し、 上記除電用バイアス印加手段として上記二次転写用バイ
アス印加手段を兼用し、 画像形成動作終了後の非画像形成時に、該二次転写部材
を上記中間転写体に接触させるとともに、該二次転写部
材に印加する電圧を上記二次転写用バイアスから上記除
電用バイアスに切り替えるように、上記離接手段及び該
二次転写用バイアス印加手段を制御する制御手段を設け
たことを特徴とする画像形成装置。
6. A secondary transfer member disposed so as to be capable of coming into contact with and separating from the intermediate transfer member via the transfer material, and applying a secondary transfer bias to the secondary transfer member. And a bias applying means for secondary transfer.
The image forming apparatus according to claim 1, wherein the secondary transfer member is also used as the charge removing member, and the secondary transfer bias applying unit is also used as the charge removing bias applying unit, at the time of non-image formation after the end of the image forming operation. Contacting the secondary transfer member with the intermediate transfer member, and switching the voltage applied to the secondary transfer member from the secondary transfer bias to the charge eliminating bias by using the separation / contact means and the secondary An image forming apparatus comprising a control unit for controlling a transfer bias applying unit.
【請求項7】請求項6の画像形成装置において、 上記二次転写部材が、上記除電用バイアスが印加される
芯金部上に弾性体からなる表面部を有するローラ状部材
であり、 該芯金部と上記中間転写体に接触する接触部との間の抵
抗値が、10〜10 10Ωであることを特徴とする画
像形成装置。
7. The image forming apparatus according to claim 6, wherein said secondary transfer member is applied with said bias for static elimination.
Roller-shaped member having a surface portion made of an elastic body on a cored bar
A resistance between the cored bar and a contact portion that comes into contact with the intermediate transfer member.
The resistance value is 105-10 10Image characterized by being Ω
Image forming device.
【請求項8】請求項6の画像形成装置において、 上記二次転写部材が、上記中間転写体に対向する導電性
対向ローラを含む複数の支持ローラに支持された弾性体
からなるベルト状部材であり、 該ベルト状部材の該導電性対向ローラに接触する接触部
と該中間転写体に接触する接触部との間の抵抗値が、1
〜1010Ωであることを特徴とする画像形成装
置。
8. The image forming apparatus according to claim 6, wherein the secondary transfer member is a belt-shaped member made of an elastic body supported by a plurality of support rollers including a conductive opposing roller facing the intermediate transfer member. A resistance value between a contact portion of the belt-shaped member that contacts the conductive opposing roller and a contact portion that contacts the intermediate transfer member is 1
An image forming apparatus, wherein the resistance is from 0 5 to 10 10 Ω.
【請求項9】請求項1の画像形成装置において、 上記中間転写体の体積抵抗率が10〜1012Ω・c
m且つ表面抵抗率が10〜1015Ω/□であること
を特徴とする画像形成装置。
9. An image forming apparatus according to claim 1, wherein said intermediate transfer body has a volume resistivity of 10 8 to 10 12 Ω · c.
m and a surface resistivity of 10 8 to 10 15 Ω / □.
【請求項10】請求項1の画像形成装置において、 上記除電用バイアスが、画像形成動作時に帯電した上記
中間転写体の帯電電位とは逆極性の直流電圧であること
を特徴とする画像形成装置。
10. An image forming apparatus according to claim 1, wherein said bias for discharging is a DC voltage having a polarity opposite to a charging potential of said intermediate transfer member charged during an image forming operation. .
【請求項11】請求項1の画像形成装置において、 上記除電用バイアスが定電流制御された交流電圧であ
り、 該交流電圧の周波数[Hz]の値が、画像形成装置のプ
ロセス速度[mm/sec]の5倍以上の値を有するこ
とを特徴とする画像形成装置。
11. The image forming apparatus according to claim 1, wherein the charge eliminating bias is an AC voltage controlled by a constant current, and a value of a frequency [Hz] of the AC voltage is a process speed [mm / mm] of the image forming apparatus. [sec] of the image forming apparatus.
【請求項12】請求項1の画像形成装置において、 上記除電用バイアスが、画像形成動作時に帯電した上記
中間転写体の帯電電位とは逆極性の直流電圧と、定電流
制御された交流電圧とを重畳したものであり、 該交流電圧の周波数[Hz]の値が、画像形成装置のプ
ロセス速度[mm/sec]の5倍以上の値であること
を特徴とする画像形成装置。
12. An image forming apparatus according to claim 1, wherein said bias for discharging is a DC voltage having a polarity opposite to a charging potential of said intermediate transfer member charged during an image forming operation, and an AC voltage controlled at a constant current. Wherein the value of the frequency [Hz] of the AC voltage is at least five times the process speed [mm / sec] of the image forming apparatus.
【請求項13】像担持体上にトナー像を形成し、該像担
持体上のトナー像を中間転写体に一次転写し、該中間転
写体上のトナー像を更に転写材に二次転写する画像形成
方法において、 画像形成動作後の非画像形成時に、該画像形成動作時に
帯電した上記中間転写体の帯電電位とは逆極性の電荷を
該中間転写体に付与して該中間転写体を除電することを
特徴とする画像形成方法。
13. A toner image is formed on an image carrier, the toner image on the image carrier is primarily transferred to an intermediate transfer member, and the toner image on the intermediate transfer member is further secondary-transferred to a transfer material. In the image forming method, during non-image formation after the image forming operation, a charge having a polarity opposite to the charging potential of the intermediate transfer body charged during the image forming operation is applied to the intermediate transfer body to remove the charge of the intermediate transfer body. An image forming method.
JP2000011884A 2000-01-20 2000-01-20 Image forming device and image forming method Pending JP2001201954A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
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Application Number Priority Date Filing Date Title
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Country Link
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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004198943A (en) * 2002-12-20 2004-07-15 Ricoh Co Ltd Image forming apparatus
US7412176B2 (en) 2003-11-26 2008-08-12 Samsung Electronics Co., Ltd. Method of processing an error of an image forming apparatus
JP2009128641A (en) * 2007-11-22 2009-06-11 Canon Inc Image forming apparatus
US7773928B2 (en) 2006-05-08 2010-08-10 Ricoh Company, Limited Transfer-separation device and image forming apparatus
US8014701B2 (en) 2007-12-17 2011-09-06 Ricoh Company, Ltd. Contacting and separating mechanism and image forming apparatus
JP2013029797A (en) * 2011-06-22 2013-02-07 Ricoh Co Ltd Image forming device
US9274461B2 (en) 2013-04-17 2016-03-01 Ricoh Company, Ltd. Transfer device and image forming apparatus incorporating same

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004198943A (en) * 2002-12-20 2004-07-15 Ricoh Co Ltd Image forming apparatus
US7412176B2 (en) 2003-11-26 2008-08-12 Samsung Electronics Co., Ltd. Method of processing an error of an image forming apparatus
US7773928B2 (en) 2006-05-08 2010-08-10 Ricoh Company, Limited Transfer-separation device and image forming apparatus
JP2009128641A (en) * 2007-11-22 2009-06-11 Canon Inc Image forming apparatus
US8014701B2 (en) 2007-12-17 2011-09-06 Ricoh Company, Ltd. Contacting and separating mechanism and image forming apparatus
JP2013029797A (en) * 2011-06-22 2013-02-07 Ricoh Co Ltd Image forming device
US9274461B2 (en) 2013-04-17 2016-03-01 Ricoh Company, Ltd. Transfer device and image forming apparatus incorporating same

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