JP3453541B2 - Image forming device - Google Patents
Image forming deviceInfo
- Publication number
- JP3453541B2 JP3453541B2 JP35936899A JP35936899A JP3453541B2 JP 3453541 B2 JP3453541 B2 JP 3453541B2 JP 35936899 A JP35936899 A JP 35936899A JP 35936899 A JP35936899 A JP 35936899A JP 3453541 B2 JP3453541 B2 JP 3453541B2
- Authority
- JP
- Japan
- Prior art keywords
- recording material
- charge
- image forming
- forming apparatus
- material carrier
- 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.)
- Expired - Fee Related
Links
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- Electrostatic Charge, Transfer And Separation In Electrography (AREA)
- Color Electrophotography (AREA)
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、電子写真方式を用
いて記録材上に像を形成する画像形成装置、たとえば複
写機、プリンタ、ＦＡＸ等の画像形成装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image on a recording material by using an electrophotographic system, for example, an image forming apparatus such as a copying machine, a printer or a FAX.
【０００２】[0002]
【従来の技術】従来より、電子写真方式を用いた種々の
画像形成装置が提案または実施されてきている。たとえ
ば、感光ドラム上に形成されたトナー像を転写ドラムま
たは転写ベルトに担持搬送される記録材に順次重ねて転
写する方式のものがある。2. Description of the Related Art Conventionally, various image forming apparatuses using an electrophotographic system have been proposed or implemented. For example, there is a system in which a toner image formed on a photosensitive drum is sequentially superimposed and transferred onto a recording material carried and conveyed by a transfer drum or a transfer belt.
【０００３】転写ベルトを用いた画像形成装置の画像形
成プロセスについて簡単に説明すると、まず、感光ドラ
ムが回転し、その表面を帯電器によって一様に帯電す
る。つぎに原稿の１色目、たとえばマゼンタの画像信号
によって変調したレーザ光を感光ドラムに照射し、感光
ドラム上にマゼンタの静電潜像を形成する。その静電潜
像をマゼンタ現像器によって現像して、感光ドラム上に
１色目のマゼンタトナー像を形成する。The image forming process of the image forming apparatus using the transfer belt will be briefly described. First, the photosensitive drum rotates and its surface is uniformly charged by the charger. Next, the photosensitive drum is irradiated with laser light modulated by the image signal of the first color of the original, for example, magenta, to form a magenta electrostatic latent image on the photosensitive drum. The electrostatic latent image is developed by a magenta developing device to form a magenta toner image of the first color on the photosensitive drum.
【０００４】一方、給紙カセットに収納されている記録
材は、レジストローラ等によって転写ベルトへ搬送され
る。この記録材の搬送と同時に、吸着ローラを転写ベル
トの表面に押し付け、裏面側から吸着帯電器により吸着
帯電して、記録材を転写ベルト上に静電的に吸着する。
この転写ベルトは、感光ドラムと同期して回転してお
り、感光ドラム上に形成されたマゼンタトナー像が、転
写ベルトに担持された記録材に転写帯電器により転写さ
れる。転写ベルトはそのまま回転を続けて、つぎの２色
目のシアントナー像の転写に備える。On the other hand, the recording material stored in the paper feed cassette is conveyed to the transfer belt by a registration roller or the like. Simultaneously with the conveyance of the recording material, the adsorption roller is pressed against the surface of the transfer belt, and the recording material is electrostatically adsorbed from the back surface side by the adsorption charger to electrostatically adsorb the recording material on the transfer belt.
The transfer belt rotates in synchronization with the photosensitive drum, and the magenta toner image formed on the photosensitive drum is transferred to the recording material carried on the transfer belt by the transfer charger. The transfer belt continues to rotate in preparation for the transfer of the next cyan toner image of the second color.
【０００５】つぎに、感光ドラム上に２色目のシアント
ナー像を形成し、そのシアントナー像を転写ベルトに担
持された記録材にマゼンタトナー像の上から重ね合わせ
て転写する。同様な画像形成を工程を３色目、４色目の
イエローおよびブラックについて繰り返し、記録材上に
マゼンタ、シアン、イエロー、ブラックの４色のトナー
像を重ね合わせたフルカラー画像を得る。Next, a cyan toner image of the second color is formed on the photosensitive drum, and the cyan toner image is transferred onto the recording material carried on the transfer belt by superimposing it on the magenta toner image. The same image forming process is repeated for the third and fourth colors of yellow and black to obtain a full-color image in which four color toner images of magenta, cyan, yellow and black are superposed on the recording material.
【０００６】４色のトナー像が転写された記録材は転写
ベルトから分離され、定着器へ搬送される。定着器は、
トナー像と記録材とを定着ローラと加圧ローラにより加
熱および加圧して、各色のトナー像の混色および記録材
への定着を行い、フルカラーのプリント画像が形成さ
れ、記録材は機外へ排出される。The recording material on which the four color toner images have been transferred is separated from the transfer belt and conveyed to the fixing device. The fuser is
The toner image and the recording material are heated and pressed by the fixing roller and the pressure roller to mix the toner images of the respective colors and fix the toner image on the recording material, and a full-color print image is formed, and the recording material is discharged to the outside of the machine. To be done.
【０００７】[0007]
【発明が解決しようとする課題】上記の転写工程では、
像転写の安定性等の面から、転写帯電器に定電流電源を
接続し、転写電流を定電流制御することを行っている。
しかしながら、以下のような転写不良が発生することが
あった。In the above transfer process,
From the standpoint of stability of image transfer, a constant current power source is connected to the transfer charger to control the transfer current at a constant current.
However, the following transfer failure may occur.
【０００８】この画像形成装置では、使用可能な最大サ
イズ（記録材の搬送方向と直交する方向の長さ）よりも
小さいサイズの記録材にも画像形成することが可能にな
っている。ここで、記録材の体積抵抗率は、記録材の種
類や吸湿条件によって約２×１０7〜１０14Ωｃｍまで
変化する。In this image forming apparatus, it is possible to form an image on a recording material having a size smaller than the maximum usable size (length in the direction orthogonal to the conveying direction of the recording material). Here, the volume resistivity of the recording material changes to about 2 × 10 7 to 10 14 Ωcm depending on the type of the recording material and the moisture absorption condition.
【０００９】図１２に示すように、転写ベルト１３０に
より使用最大サイズの記録材Ｐを通紙して転写した場
合、転写帯電器２４からの転写電流をＩtr［μＡ］、記
録材の幅（転写ベルト１３０の移動方向と直交方向のス
ラスト方向の長さ）をχ［ｃｍ］、感光ドラム３の回転
速度、つまりプロセススピードをｖ「ｃｍ／ｓ］とする
と、図１３に示すように、Δｔ秒間に流れる転写電流は
Ｉtr×Δｔ、そのときの記録材の対象面積はｖ×Δｔ×
χであるから、記録材上の面電荷密度は、
Ｉtr×Δｔ／（χ×Δｔ×ｖ）＝Ｉtr／（χ・ｖ）［μ
Ｃ／ｃｍ2］
となる。As shown in FIG. 12, when the transfer belt 130 transfers the recording material P of the maximum size to be used for transfer, the transfer current from the transfer charger 24 is Itr [μA], the width of the recording material (transfer). Assuming that the length in the thrust direction orthogonal to the moving direction of the belt 130) is χ [cm] and the rotation speed of the photosensitive drum 3, that is, the process speed is v “cm / s”, as shown in FIG. The transfer current flowing in the recording medium is Itr × Δt, and the target area of the recording material at that time is v × Δt ×
Since it is χ, the surface charge density on the recording material is Itr × Δt / (χ × Δt × v) = Itr / (χ · v) [μ
C / cm 2 ].
【００１０】記録材は、常温低湿環境（たとえば２３
℃、５％ＲＨ）では、相対的に非常に高い体積抵抗率と
なるが、そのような場合でも定電流方式では、記録材の
幅が最大の最大サイズの記録材上の面電荷密度は変化し
ない。The recording material is a normal temperature and low humidity environment (for example, 23
At 5 ° C. and 5% RH), the volume resistivity is relatively very high, but even in such a case, the constant current method changes the surface charge density on the maximum size recording material with the maximum width. do not do.
【００１１】一方、記録材の幅が小さい小サイズの記録
材を通紙した場合、図１４に示すように、記録材Ｐの部
分に流れる電流をＩχ、記録材の両側の非通紙部に流れ
る電流をそれぞれにＩｗ、Ｉｚとし、記録材の幅をχ、
非通紙部の幅をそれぞれｗ、ｚとすると、本来ならば記
録材上および非通紙部の面電荷密度は、最大サイズの記
録材を通紙した場合と同じでなければならない（すなわ
ち、Ｉｗ／（ｗ・ｖ）＝Ｉχ／（χ・ｖ）＝Ｉｚ／（ｚ
・ｖ））のが、通紙部は記録材自体の抵抗が存在するの
で、非通紙部に比べてインピーダンスが高く、そのため
通紙部に流れる単位面積あたりの電流も非通紙部に比べ
て小さく、記録材上の面電荷密度も非通紙部に比べて小
さくなる。On the other hand, when a small-sized recording material having a small width is passed, as shown in FIG. 14, the current flowing in the portion of the recording material P is Iχ, and the non-sheet passing portion on both sides of the recording material is The flowing currents are Iw and Iz, respectively, and the width of the recording material is χ,
If the widths of the non-sheet passing portion are w and z, respectively, the surface charge densities on the recording material and on the non-sheet passing portion should be the same as when the recording material of the maximum size is passed (that is, Iw / (w · v) = Iχ / (χ · v) = Iz / (z
・ V)), but because the resistance of the recording material itself exists in the paper passing portion, the impedance is higher than in the non-paper passing portion, so the current per unit area flowing in the paper passing portion is also higher than in the non-paper passing portion. And the surface charge density on the recording material is smaller than that of the non-sheet passing portion.
【００１２】このため定電流方式では、記録材上の面電
荷密度は必要十分に達せず（すなわち、Ｉｗ／（ｗ・
ｖ）＝Ｉｚ／（ｚ・ｖ）＞Ｉχ／（χ・ｖ））、転写不
良を引き起こしてしまう。For this reason, in the constant current method, the surface charge density on the recording material does not reach the necessary and sufficient level (that is, Iw / (w.
v) = Iz / (z.v)> I.chi ./ (. chi.v)), causing a transfer failure.
【００１３】これは、たとえば乾燥して高抵抗になった
記録材などに転写する場合、あるいは高温高湿環境（た
とえば３０℃、８０％ＲＨ）下において転写ベルトが吸
湿し、低抵抗化した場合などに顕著に発生する。This is because, for example, when transferring to a recording material or the like which has become dry and has a high resistance, or when the transfer belt absorbs moisture under a high temperature and high humidity environment (for example, 30 ° C., 80% RH) and the resistance becomes low. Occurs remarkably.
【００１４】また、感光ドラムの非通紙部にあたる部分
の表面電位は、通常、現像時にトナーの付着を防止する
ために、図１５に示すように、感光ドラムの高電位部で
ある非画像部の電位（Ｖｄ）と同じ電位になっている。
そうすると、定電流方式の場合、小サイズ紙を通過させ
ると、電位差の大きい非通紙部に多くの電流が流れ、通
紙部に流れる電流が不足して転写不良を生じる。Further, the surface potential of the portion corresponding to the non-sheet passing portion of the photosensitive drum is usually a non-image portion which is a high potential portion of the photosensitive drum as shown in FIG. 15 in order to prevent toner from adhering during development. It has the same potential as the potential (Vd).
Then, in the case of the constant current method, when a small size sheet is passed, a large amount of current flows in the non-sheet passing portion having a large potential difference, and the current flowing in the sheet passing portion is insufficient, resulting in a transfer failure.
【００１５】そこで、逆に小サイズ紙の通紙時に十分な
電流が通紙部に流れるように転写バイアスを設定する
と、今度は、最大幅の記録材を通紙したときに過剰な電
流が流れ、トナーが逆帯電して転写不良となる。Therefore, conversely, if the transfer bias is set so that a sufficient current flows through the paper passing portion when a small size paper is passed, an excessive current will flow when the recording material of the maximum width is passed. However, the toner is reversely charged and the transfer becomes defective.
【００１６】本発明の目的は、像担持体から記録材担持
体に担持された記録材に像を転写する際に、転写不良が
発生するのを防止することができる画像形成装置を提供
することである。An object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of transfer failure when an image is transferred from an image carrier to a recording material carried on a recording material carrier. Is.
【００１７】本発明の他の目的は、以下の詳細な説明を
読むことにより明らかになるであろう。Other objects of the present invention will become apparent upon reading the following detailed description.
【００１８】[0018]
【課題を解決するための手段】上記目的は本発明に係る
画像形成装置にて達成される。要約すれば、本発明は、
像を担持する像担持体と、記録材を担持する記録材担持
体と、前記像担持体上の像を前記記録材担持体上に担持
された記録材に静電的に転写するために、前記録材担持
体の記録材を担持する側とは反対側の所定の極性の電荷
を付与する第１の電荷付与手段と、記録材が前記記録材
担持体に担持される前に、前記記録材担持体の記録材を
担持する側とは反対側に電荷を付与する第２の電荷付与
手段とを有する画像形成装置であって、記録材の搬送方
向と実質的に直交する方向において、前記記録材担持体
の前記第１の電荷付与手段により電荷が付与される領域
のうち、前記記録材担持体の記録材を担持する第１の領
域よりも外側の第２の領域の電荷量が、前記第１の領域
の電荷量に比べて前記所定の極性寄りに大きくなるよう
に、前記第２の電荷付与手段は前記記録材担持体に電荷
を付与することを特徴とする画像形成装置である。The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention is
An image carrier that carries an image, a recording material carrier that carries a recording material, and in order to electrostatically transfer the image on the image carrier to the recording material carried on the recording material carrier, First charge applying means for applying a charge of a predetermined polarity on the side of the pre-recording material carrier opposite to the side carrying the recording material, and the recording material before the recording material is carried on the recording material carrier. An image forming apparatus comprising: a second charge applying unit that applies an electric charge to a side of a material carrying body opposite to a side carrying a recording material, the image forming apparatus comprising: Of the area of the recording material carrier to which the electric charge is applied by the first electric charge applying means, the second area outside the first area of the recording material carrier, which carries the recording material, has a charge amount of The second electric potential is set so as to be larger toward the predetermined polarity than the electric charge amount of the first region. Applying means is an image forming apparatus characterized by imparting a charge to said recording material bearing member.
【００１９】本発明によれば、記録材の種類に応じて、
前記第２の電荷付与手段に印加する電圧を制御する制御
手段を有する。記録材の種類を検知する記録材検知手段
を有し、前記制御手段は、前記記録材検知手段による検
知結果に応じて前記第２の電荷付与手段に印加する電圧
を制御する。記録材の種類に応じて、前記第２の電荷付
与手段により前記記録材担持体に付与される電荷量を制
御する制御手段を有する。記録材の種類を検知する記録
材検知手段を有し、前記制御手段は、前記記録材検知手
段による検知結果に応じて前記第２の電荷付与手段によ
り前記記録材担持体に付与される電荷量を制御する。According to the present invention, depending on the type of recording material,
It has a control means which controls the voltage applied to the said 2nd electric charge provision means. A recording material detection unit that detects the type of recording material is provided, and the control unit controls the voltage applied to the second charge applying unit according to the detection result of the recording material detection unit. It has a control means for controlling the amount of charge applied to the recording material carrier by the second charge applying means according to the type of recording material. A recording material detection unit that detects the type of recording material is provided, and the control unit supplies the amount of electric charge applied to the recording material carrier by the second electric charge application unit according to the detection result of the recording material detection unit. To control.
【００２０】湿度に応じて、前記第２の電荷付与手段に
印加する電圧を制御する制御手段を有する。湿度を検知
する湿度検知手段を有し、前記制御手段は、前記湿度検
知手段による検知結果に応じて前記第２の電荷付与手段
に印加する電圧を制御する。温度および湿度に応じて、
前記第２の電荷付与手段に印加する電圧を制御する制御
手段を有する。温度および湿度を検知する温湿度検知手
段を有し、前記制御手段は、前記温湿度検知手段による
検知結果に応じて前記第２の電荷付与手段に印加する電
圧を制御する。There is provided control means for controlling the voltage applied to the second charge applying means in accordance with the humidity. The control means controls the voltage applied to the second charge applying means in accordance with the detection result of the humidity detecting means. Depending on temperature and humidity,
It has a control means which controls the voltage applied to the said 2nd electric charge provision means. The control means has a temperature / humidity detection means for detecting temperature and humidity, and the control means controls the voltage applied to the second charge applying means in accordance with the detection result of the temperature / humidity detection means.
【００２１】湿度に応じて、前記第２の電荷付与手段に
より前記記録材担持体に付与される電荷量を制御する制
御手段を有する。湿度を検知する湿度検知手段を有し、
前記制御手段は、前記湿度検知手段による検知結果に応
じて前記第２の電荷付与手段により前記記録材担持体に
付与される電荷量を制御する。温度および湿度に応じ
て、前記第２の電荷付与手段により前記記録材担持体に
付与される電荷量を制御する制御手段を有する。温度お
よび湿度を検知する温湿度検知手段を有し、前記制御手
段は、前記温湿度検知手段による検知結果に応じて前記
第２の電荷付与手段により前記記録材担持体に付与され
る電荷量を制御する。There is provided control means for controlling the amount of electric charge applied to the recording material carrier by the second electric charge applying means in accordance with the humidity. It has humidity detection means to detect humidity,
The control unit controls the amount of electric charge applied to the recording material carrier by the second electric charge applying unit according to the detection result of the humidity detecting unit. It has a control means for controlling the amount of electric charge applied to the recording material carrier by the second electric charge applying means according to temperature and humidity. The control means has a temperature / humidity detecting means for detecting temperature and humidity, and the control means controls the amount of electric charge applied to the recording material carrier by the second electric charge applying means in accordance with the detection result of the temperature / humidity detecting means. Control.
【００２２】前記記録材担持体の前記第１の領域に前記
第２の電荷付与手段により付与される電荷量はゼロであ
る。前記第２の電荷付与手段により前記記録材担持体の
前記第１の領域に付与される電荷の極性は、前記第１の
電荷付与手段により前記記録材担持体に付与される電荷
の極性とは逆極性である。前記第２の電荷付与手段によ
り前記記録材担持体の前記第２の領域に付与される電荷
の極性は、前記第１の電荷付与手段により前記記録材担
持体に付与される電荷の極性とは逆極性である。前記第
２の電荷付与手段により前記記録材担持体の前記第２の
領域に付与される電荷量の絶対値は、前記第２の電荷付
与手段により前記記録材担持体の前記第１の領域に付与
される電荷量の絶対値よりも小さい。The amount of charge applied to the first region of the recording material carrier by the second charge applying means is zero. The polarity of the charge applied to the first area of the recording material carrier by the second charge applying means is the polarity of the charge applied to the recording material carrier by the first charge applying means. It has opposite polarity. The polarity of the charge applied to the second area of the recording material carrier by the second charge applying means is the polarity of the charge applied to the recording material carrier by the first charge applying means. It has opposite polarity. The absolute value of the amount of charge applied to the second area of the recording material carrier by the second charge applying means is the same as the absolute value of the amount of charge applied to the first area of the recording material carrier by the second charge applying means. It is smaller than the absolute value of the applied charge amount.
【００２３】前記第２の電荷付与手段により前記記録材
担持体の前記第１の領域に付与される電荷の極性は、前
記第１の電荷付与手段により前記記録材担持体に付与さ
れる電荷の極性と同極性である。前記第２の電荷付与手
段により前記記録材担持体の前記第２の領域に付与され
る電荷の極性は、前記第１の電荷付与手段により前記記
録材担持体に付与される電荷の極性と同極性である。前
記第２の電荷付与手段により前記記録材担持体の前記第
２の領域に付与される電荷量の絶対値は、前記第２の電
荷付与手段により前記記録材担持体の前記第１の領域に
付与される電荷量の絶対値よりも大きい。前記第２の電
荷付与手段により前記記録材担持体の前記第２の領域に
付与される電荷の極性は、前記第１の電荷付与手段によ
り前記記録材担持体に付与される電荷の極性とは逆極性
である。The polarity of the charge applied to the first region of the recording material carrier by the second charge applying means is the polarity of the charge applied to the recording material carrier by the first charge applying means. It is the same polarity as the polarity. The polarity of the charge applied to the second area of the recording material carrier by the second charge applying means is the same as the polarity of the charge applied to the recording material carrier by the first charge applying means. It is polar. The absolute value of the amount of charge applied to the second area of the recording material carrier by the second charge applying means is the same as the absolute value of the amount of charge applied to the first area of the recording material carrier by the second charge applying means. It is larger than the absolute value of the amount of charge given. The polarity of the charge applied to the second area of the recording material carrier by the second charge applying means is the polarity of the charge applied to the recording material carrier by the first charge applying means. It has opposite polarity.
【００２４】前記第２の電荷付与手段は、前記記録材担
持体の記録材を担持する側に電荷を付与する第１の電荷
付与部材と、前記記録材担持体を介して前記第１の電荷
付与部材に対向するように設けられ、前記記録材担持体
の記録材を担持する側とは反対側に電荷を付与する第２
の電荷付与部材とを備える。記録材の搬送方向と実質的
に直交する方向において、前記第２の電荷付与手段によ
り前記記録材担持体に電荷を付与する領域は、記録材の
長さに応じて可変である。記録材の搬送方向と実質的に
直交する方向において、前記第２の電荷付与手段は、前
記記録材担持体の前記第２の領域にのみ電荷を付与す
る。前記像担持体の帯電極性は前記所定の極性とは逆極
性である。The second charge imparting means includes a first charge imparting member for imparting an electric charge to the recording material carrying side of the recording material carrying body, and the first electric charge through the recording material carrying body. A second member that is provided so as to face the applying member and applies an electric charge to the opposite side of the recording material carrying body from the side carrying the recording material.
Charge imparting member. An area in which the second charge applying unit applies an electric charge to the recording material carrier in a direction substantially orthogonal to the recording material conveyance direction is variable according to the length of the recording material. In the direction substantially orthogonal to the recording material conveyance direction, the second charge applying means applies charges only to the second region of the recording material carrier. The charging polarity of the image carrier is opposite to the predetermined polarity.
【００２５】前記記録材担持体の体積抵抗率は１０13〜
１０17Ωｃｍである。前記記録材担持体に担持された記
録材に複数色の像が順次重ねて転写される。前記像担持
体は複数色の像をそれぞれ担持するために複数設けら
れ、前記複数の像担持体から前記記録材担持体に担持さ
れた記録材に複数色の像が順次重ねて転写される。The volume resistivity of the recording material carrier is from 10 13 to
It is 10 17 Ωcm. Images of a plurality of colors are sequentially superimposed and transferred onto the recording material carried by the recording material carrier. A plurality of the image carriers are provided to respectively carry images of a plurality of colors, and the images of a plurality of colors are sequentially superposed and transferred from the plurality of image carriers to the recording material carried by the recording material carrier.
【００２６】[0026]
【発明の実施の形態】以下、本発明に係る実施例を図面
に則して更に詳しく説明する。BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described in more detail with reference to the drawings.
【００２７】実施例１
図１は、本発明が適用可能な画像形成装置を示す構成図
である。Embodiment 1 FIG. 1 is a block diagram showing an image forming apparatus to which the present invention can be applied.
【００２８】図１に示すように、装置内には、第１、第
２、第３、第４の画像形成部Ｐａ、Ｐｂ、Ｐｃ、Ｐｄが
並設され、各画像形成部Ｐａ〜Ｐｄで、潜像形成、現
像、転写のプロセスを経て各々異なった色のトナー像が
形成される。As shown in FIG. 1, first, second, third, and fourth image forming sections Pa, Pb, Pc, and Pd are arranged side by side in the apparatus, and each of the image forming sections Pa to Pd. The toner images of different colors are formed through the processes of latent image formation, development, and transfer.
【００２９】画像形成部Ｐａ、Ｐｂ、Ｐｃ、Ｐｄは、そ
れぞれ専用の像担持体、本例では電子写真感光ドラム３
ａ、３ｂ、３ｃ、３ｄを具備し、各感光ドラム３ａ、３
ｂ、３ｃ、３ｄ上に各色のトナー像が形成される。各感
光ドラム３ａ、３ｂ、３ｃ、３ｄに隣接して、記録材担
持体の転写ベルト１３０が設置され、感光ドラム３ａ、
３ｂ、３ｃ、３ｄ上に形成された各色のトナー像が、転
写ベルト１３０上に担持して搬送される記録材Ｐ上に重
ね合わせて転写される。The image forming sections Pa, Pb, Pc and Pd are respectively dedicated image carriers, in this example, the electrophotographic photosensitive drum 3.
a, 3b, 3c, 3d, and each photosensitive drum 3a, 3
Toner images of respective colors are formed on b, 3c, and 3d. A transfer belt 130 of a recording material carrier is installed adjacent to each of the photosensitive drums 3a, 3b, 3c, 3d.
The toner images of the respective colors formed on 3b, 3c, and 3d are superposed and transferred onto the recording material P carried on the transfer belt 130 and conveyed.
【００３０】各色のトナー像が転写された記録材Ｐは、
定着装置９で加熱および加圧によりトナー像を定着した
後、カラーの記録画像として装置外に排出される。The recording material P on which the toner images of the respective colors have been transferred is
After fixing the toner image by the fixing device 9 by heating and pressing, it is discharged outside the device as a color recorded image.
【００３１】各感光ドラム３ａ、３ｂ、３ｃ、３ｄの外
周には、それぞれ露光ランプ１１１ａ、１１１ｂ、１１
１ｃ、１１１ｄ、ドラム帯電器２ａ、２ｂ、２ｃ、２
ｄ、電位センサー１１３ａ、１１３ｂ、１１３ｃ、１１
３ｄ、現像器１ａ、１ｂ、１ｃ、１ｄ、転写帯電器２４
ａ、２４ｂ、２４ｃ、２４ｄ、およびクリーナ４ａ、４
ｂ、４ｃ、４ｄが設けられ、装置の上方にはさらに図示
しない光源装置およびポリゴンミラー１１７が設置され
ている。Exposure lamps 111a, 111b, 11 are provided on the outer circumferences of the photosensitive drums 3a, 3b, 3c, 3d, respectively.
1c, 111d, drum chargers 2a, 2b, 2c, 2
d, potential sensors 113a, 113b, 113c, 11
3d, developing devices 1a, 1b, 1c, 1d, transfer charger 24
a, 24b, 24c, 24d, and cleaners 4a, 4
b, 4c, and 4d are provided, and a light source device and a polygon mirror 117 (not shown) are installed above the device.
【００３２】光源装置から発せられたレーザー光をポリ
ゴンミラー１１７で回転して走査し、その走査光の光束
を反射ミラーによって偏向し、ｆθレンズにより各感光
ドラム３ａ、３ｂ、３ｃ、３ｄの母線方向に集光して露
光することにより、各感光ドラム３ａ、３ｂ、３ｃ、３
ｄ上に画像信号に応じた静電潜像が形成される。The laser light emitted from the light source device is rotated by the polygon mirror 117 for scanning, the light flux of the scanning light is deflected by the reflection mirror, and the fθ lens is used to generate the direction of the generatrix of the photosensitive drums 3a, 3b, 3c, 3d. By exposing the light to the photosensitive drums 3a, 3b, 3c, 3 by
An electrostatic latent image corresponding to the image signal is formed on d.
【００３３】現像器１ａ、１ｂ、１ｃ、１ｄには、現像
剤としてそれぞれ正規の帯電極性が負極性のシアン、マ
ゼンタ、イエロー、ブラックのトナーが、図示しない供
給装置により所定量充填されている。現像器１ａ、１
ｂ、１ｃ、１ｄは、それぞれ感光ドラム３ａ、３ｂ、３
ｃ、３ｄ上の潜像を現像して、シアントナー像、マゼン
タトナー像、イエロートナー像、ブラックトナー像とし
て可視化する。The developing devices 1a, 1b, 1c, and 1d are filled with a predetermined amount of cyan, magenta, yellow, and black toners each having a negative charging polarity as a developer by a supply device (not shown). Developer 1a, 1
b, 1c and 1d are photosensitive drums 3a, 3b and 3 respectively.
The latent images on c and 3d are developed and visualized as a cyan toner image, a magenta toner image, a yellow toner image, and a black toner image.
【００３４】記録材Ｐは、記録材カセット１０に収容さ
れている。記録材Ｐはそこから複数の搬送ローラおよび
レジストローラ１２を経て転写ベルト１３０上に供給さ
れ、転写ベルト１３０による搬送で感光ドラム３ａ、３
ｂ、３ｃ、３ｄと対向した転写部に順次送られる。The recording material P is contained in the recording material cassette 10. From there, the recording material P is supplied onto the transfer belt 130 via a plurality of conveying rollers and the registration rollers 12, and is conveyed by the transfer belt 130 to the photosensitive drums 3a, 3a.
b, 3c, and 3d are sequentially sent to the transfer section facing them.
【００３５】転写ベルト１３０は、ポリエチレンテレフ
タレート樹脂（ＰＥＴ）やポリフッ化ビニリデン樹脂、
ポリウレタン樹脂などの誘電体樹脂のシートからなって
おり、その両端部を互いに重ね合わせて接合し、エンド
レス形状にしたものか、あるいは継ぎ目を有しない（シ
ームレス）ベルトが用いられている。The transfer belt 130 is made of polyethylene terephthalate resin (PET), polyvinylidene fluoride resin,
It is composed of a sheet of a dielectric resin such as polyurethane resin, and both ends thereof are overlapped and joined to each other to form an endless shape, or a seamless belt (seamless) is used.
【００３６】さて、駆動ローラ１３によりこの転写ベル
ト１３０が回転し、所定の位置にあることが確認される
と、記録材Ｐがレジストローラ１２から転写ベルト１３
０に送り出され、第１画像形成部Ｐａの転写部へ向けて
搬送される。これと同時に画像書き出し信号がオンとな
り、それを基準としてあるタイミングで第１画像形成部
Ｐａの感光ドラム３ａに対し画像形成を行う。When it is confirmed that the transfer belt 130 is rotated by the driving roller 13 and is in a predetermined position, the recording material P is transferred from the registration roller 12 to the transfer belt 13.
0, and is conveyed toward the transfer portion of the first image forming portion Pa. At the same time, the image writing signal is turned on, and an image is formed on the photosensitive drum 3a of the first image forming portion Pa at a certain timing with reference to the signal.
【００３７】そして感光ドラム３ａの下側の転写部で転
写帯電器２４ａが電界または電荷を付与することによ
り、感光ドラム３ａ上に形成された第１色目のトナー像
が記録材Ｐ上に転写される。この転写により記録材Ｐは
転写ベルト１３０上に静電吸着力でしっかりと担持さ
れ、第２画像形成部Ｐｂ以降に搬送される。Then, the transfer charger 24a applies an electric field or an electric charge at the transfer portion below the photosensitive drum 3a, whereby the first color toner image formed on the photosensitive drum 3a is transferred onto the recording material P. It By this transfer, the recording material P is firmly carried on the transfer belt 130 by the electrostatic attraction force, and is conveyed to the second image forming portion Pb and thereafter.
【００３８】転写帯電器２４（２４ａ〜２４ｄ）には、
コロナ放電のような非接触帯電器、または導電性のブレ
ード、ローラ、ブラシのような転写部材を用いた接触帯
電器を用いることができる。非接触帯電器では、オゾン
が発生することや、空気を介して帯電するため大気の温
湿度環境変動に弱く、画像が安定して形成されない等の
問題がある。接触帯電器にはこのような問題がなく、オ
ゾンレス、温湿度環境変動に強い、高画質等のメリット
がある。本例では、転写帯電器２４に接触式の帯電器を
用いている。The transfer charger 24 (24a-24d) includes:
A non-contact charger such as corona discharge or a contact charger using a transfer member such as a conductive blade, roller or brush can be used. The non-contact charger has problems that ozone is generated and that it is charged via air, so that it is vulnerable to temperature and humidity environment changes in the atmosphere and images are not stably formed. The contact charger does not have such a problem, and has advantages such as ozone-less, resistance to temperature and humidity environment variations, and high image quality. In this example, a contact type charger is used as the transfer charger 24.
【００３９】第２〜第４画像形成部Ｐｂ〜Ｐｄでの画像
形成、転写も、第１画像形成部Ｐａと同様に行われる。
ついで４色のトナー像を転写された記録材Ｐは、転写ベ
ルト１３０の搬送方向下流部で分離帯電器３２により除
電して静電吸着力を減衰させることにより、転写ベルト
１３０の末端から離脱する。通常、駆動ローラ１３は安
定な分離を行うために接地されている。また分離帯電器
３２は、トナー像が未定着の状態で記録材Ｐを除電する
ので、非接触帯電器が用いられている。Image formation and transfer in the second to fourth image forming portions Pb to Pd are performed in the same manner as in the first image forming portion Pa.
Then, the recording material P to which the toner images of four colors have been transferred is removed from the end of the transfer belt 130 by removing the charge by the separation charging device 32 at the downstream portion of the transfer belt 130 in the transport direction to attenuate the electrostatic attraction force. . Usually, the drive roller 13 is grounded for stable separation. The separation charger 32 is a non-contact charger because it discharges the recording material P with the toner image unfixed.
【００４０】転写ベルト１３０から離脱した記録材Ｐ
は、搬送部６２により定着装置９へ搬送される。定着装
置９は、定着ローラ５１、加圧ローラ５２と、その各々
をクリーニングする耐熱性クリーニング部材５４、５５
と、ローラ５１、５２内に設置された加熱ヒータ５６、
５７と、定着ローラ５１にジメチルシリコーンオイル等
の離型剤オイルを塗布する塗布ローラ５０と、そのオイ
ル溜め５３と、加圧ローラ５２の表面の温度を検知して
定着温度を制御するサーミスタ５８とから構成されてい
る。The recording material P separated from the transfer belt 130
Is transported to the fixing device 9 by the transport unit 62. The fixing device 9 includes a fixing roller 51, a pressure roller 52, and heat resistant cleaning members 54 and 55 for cleaning each of them.
And a heater 56 installed in the rollers 51 and 52,
57, an application roller 50 for applying a release agent oil such as dimethyl silicone oil to the fixing roller 51, an oil sump 53 thereof, and a thermistor 58 for detecting the surface temperature of the pressure roller 52 and controlling the fixing temperature. It consists of
【００４１】４色のトナー像が転写された記録材Ｐは、
定着によりトナー像の混色および記録材Ｐへの固定が行
われ、フルカラーのコピー画像に形成され、排紙トレイ
６３に排出される。The recording material P on which the four color toner images have been transferred is
The toner images are mixed and fixed to the recording material P by fixing, and a full-color copy image is formed, and the copy image is discharged to the paper discharge tray 63.
【００４２】転写が終了した感光ドラム３ａ、３ｂ、３
ｃ、３ｄは、それぞのクリーナ４ａ、４ｂ、４ｃ、４ｄ
により転写残りトナーをクリーニング、除去され、引き
続きつぎの潜像の形成以下に備えられる。転写ベルト１
３０上に残留したトナーおよびその他の異物は、転写ベ
ルト１３０の表面にクリーニングウエブ（不織布）１９
を当接して、拭い取るようにしている。Photosensitive drums 3a, 3b, 3 for which transfer has been completed
c and 3d are cleaners 4a, 4b, 4c and 4d, respectively.
Thus, the transfer residual toner is cleaned and removed, and the preparation for the subsequent latent image formation is performed. Transfer belt 1
Toner and other foreign matter remaining on the cleaning belt 30 are transferred onto the surface of the transfer belt 130 by a cleaning web (nonwoven fabric) 19
Abutting against each other and wiping it off.
【００４３】以上のような構成の画像形成装置で用いら
れている転写ベルト１３０は、前述のように、ＰＥＴシ
ートやポリフッ化ビニリデンシート、ポリウレタンシー
ト等の誘電体シートであり、これらの体積抵抗は１０13
〜１０17Ωｃｍのものが好ましい。また転写帯電器２４
は、転写に寄与する電流（転写電流）が適正電流で一定
にすると画像が安定することが知られており、そこで、
記録材の種類（厚さ、材質等）や吸湿条件等により、体
積抵抗が変化した場合にも、一定電流が得られるよう
に、定電流電源を接続して定電流制御をすることが好ま
しく、この場合、転写電圧は数ｋＶ〜１０数ｋＶかか
る。The transfer belt 130 used in the image forming apparatus having the above structure is a dielectric sheet such as a PET sheet, a polyvinylidene fluoride sheet, a polyurethane sheet, etc., as described above, and their volume resistance is 10 13
It is preferably from 10 to 17 17 Ωcm. In addition, the transfer charger 24
Is known to stabilize the image when the current contributing to transfer (transfer current) is kept constant at an appropriate current.
It is preferable to connect a constant current power source and perform constant current control so that a constant current can be obtained even when the volume resistance changes due to the type of recording material (thickness, material, etc.) and moisture absorption conditions. In this case, the transfer voltage takes several kV to several kV.
【００４４】多重転写を行う画像形成装置では、各転写
段階で前の転写時よりも大きな転写電圧が必要になり、
特に最後（４色目）の転写時は、最初（１色目）の転写
時と比べかなり高い転写電圧になる。In the image forming apparatus for carrying out multiple transfer, a transfer voltage larger than that at the previous transfer is required at each transfer stage.
In particular, the transfer voltage for the last (fourth color) transfer is considerably higher than that for the first (first color) transfer.
【００４５】転写ベルト１３０の誘電体シート素材とし
ては、上述の他に、ポリアセタール、ポリアミド、ポリ
ビニルアルコール、ポリエーテルケトン、ポリスチレ
ン、ポリブチレンテレフタレート、ポリメチルペンテ
ン、ポリプロピレン、ポリエチレン、ポリフェニレンス
ルフィド、シリコーン樹脂、ポリアミドイミド、ポリカ
ーボネート、ポリフェニレンオキシド、ポリエーテルス
ルホン、ポリサルフォン、芳香族ポリエステル、ポリエ
ーテルイミド、芳香族ポリイミドなど、エンジニアリン
グプラスチックのフィルム形状シートを用いてもよく、
本実施例では、機械特性、電気的特性および難燃性等の
点から、ポリイミド樹脂を使用した。その体積抵抗率は
１０16Ωｃｍ、厚さは１００μｍで、シームレスタイプ
である。As the dielectric sheet material of the transfer belt 130, in addition to the above, polyacetal, polyamide, polyvinyl alcohol, polyether ketone, polystyrene, polybutylene terephthalate, polymethylpentene, polypropylene, polyethylene, polyphenylene sulfide, silicone resin, Polyamide imide, polycarbonate, polyphenylene oxide, polyether sulfone, polysulfone, aromatic polyester, polyetherimide, aromatic polyimide, such as engineering plastic film-shaped sheet may be used,
In this example, a polyimide resin was used in terms of mechanical properties, electrical properties, flame retardancy, and the like. It has a volume resistivity of 10 16 Ωcm and a thickness of 100 μm, and is a seamless type.
【００４６】転写ベルトを駆動する駆動手段と、記録材
の幅を検知する検知手段とを備え、プロセススピード
（転写ベルトの移動速度）は１００ｍｍ／秒である。A driving means for driving the transfer belt and a detecting means for detecting the width of the recording material are provided, and the process speed (moving speed of the transfer belt) is 100 mm / sec.
【００４７】接触式の転写帯電器２４（２４ａ〜２４
ｄ）は、記録材搬送方向に対して直交する方向（スラス
ト方向）に延びる板状導電性ゴム（ブレード）の転写部
材を有し、この転写部材は、転写ベルト１３０を介して
感光ドラム３（３ａ〜３ｄ）と接触するように押圧され
ている。この転写帯電器２４にトナーの正規の帯電極性
とは逆極性（本例ではプラス）の電圧が印加され、感光
ドラム３上のトナー像が記録材Ｐの表面に静電転写され
る。本実施例では、転写帯電器２４に流れる電流を定電
流制御し、転写電流を１０μＡとした。Contact type transfer charger 24 (24a-24)
(d) has a transfer member of a plate-shaped conductive rubber (blade) extending in a direction (thrust direction) orthogonal to the recording material conveyance direction, and this transfer member is provided on the photosensitive drum 3 (via the transfer belt 130). 3a to 3d) are pressed. A voltage having a polarity (plus in this example) opposite to the regular charging polarity of the toner is applied to the transfer charger 24, and the toner image on the photosensitive drum 3 is electrostatically transferred onto the surface of the recording material P. In this embodiment, the current flowing through the transfer charger 24 is controlled to a constant current, and the transfer current is set to 10 μA.
【００４８】分離帯電器３２は、転写ベルト１３０の最
下流上方、すなわち転写ベルト１３０の駆動ローラ１３
の上方に配置され、放電ワイヤーを備えている。放電ワ
イヤーはスラスト方向に張設されており、放電ワイヤー
の片側端部にスプリングを設けることにより、その張力
を保っている。放電ワイヤーへの給電は、装置本体側コ
ネクターより図示しない給電端子、給電ピンおよびスプ
リングを介して行われる。The separation charger 32 is located at the uppermost downstream side of the transfer belt 130, that is, the drive roller 13 of the transfer belt 130.
And is equipped with a discharge wire. The discharge wire is stretched in the thrust direction, and the tension is maintained by providing a spring at one end of the discharge wire. Power is supplied to the discharge wire from a connector on the apparatus main body side through a power supply terminal, a power supply pin, and a spring (not shown).
【００４９】また駆動ローラ１３は本体アースに接続さ
れ、放電ワイヤーの対向電極の機能を兼ねている。本実
施例では、最終段の画像形成部Ｐｄの転写帯電器２４ｄ
と分離帯電部との距離が５０ｍｍであり、分離帯電器３
２に１０ｋＶｐｐのＡＣ電圧を印加した。The drive roller 13 is connected to the earth of the main body and also functions as an opposite electrode of the discharge wire. In this embodiment, the transfer charger 24d of the image forming portion Pd at the final stage is used.
The distance between the separation charging unit and the separation charging unit is 50 mm.
An AC voltage of 10 kVpp was applied to 2.
【００５０】さて、上記のような電子写真方式の画像形
成装置では、転写帯電器２４の転写部材のスラスト方向
の長さは、通常、最大サイズの記録材をカバーできるよ
うに、最大サイズの記録材の幅（上記のスラスト方向と
同方向の長さ）より若干長めとされている。しかし、小
サイズの記録材を通紙する際、上記したように、記録材
の面電荷密度が不足となり、転写不良が生じてしまう。
以下に、この現象を詳細に説明する。In the electrophotographic image forming apparatus as described above, the length of the transfer member of the transfer charger 24 in the thrust direction is usually the maximum size recording so that the maximum size recording material can be covered. It is slightly longer than the width of the material (the length in the same direction as the thrust direction). However, when a small-sized recording material is passed, as described above, the surface charge density of the recording material becomes insufficient, resulting in defective transfer.
This phenomenon will be described in detail below.
【００５１】図２は、転写時の紙の面電荷密度と紙に転
写された画像濃度（反射濃度）との相関を示す。紙上面
電荷密度が上がるにつれて、紙上画像濃度も上がってい
るのが分かる。画像不良を起こさないようにするために
は、１．５５以上の反射濃度が必要であり、紙上電荷密
度は、図２から最低２４ｐＣ／ｃｍ2必要であることが
分かる。FIG. 2 shows the correlation between the surface charge density of paper at the time of transfer and the image density (reflection density) transferred to the paper. It can be seen that as the charge density on the upper surface of the paper increases, the image density on the paper also increases. It can be seen from FIG. 2 that the reflection density of 1.55 or more is necessary and the charge density on paper is at least 24 pC / cm 2 in order to prevent image defects.
【００５２】本実施例の構成で最大サイズの記録材を通
紙したときの紙上面電荷密度は、転写Ｉtr＝１０μＡ、
記録材のスラスト幅χ＝３０ｃｍ、プロセススピードｖ
＝１０ｃｍ／ｓであるので、前述した式から、
Ｉtr／（χ・ｖ）＝１０／（３０×１０）＝１／３０
［μＣ／ｃｍ2］
となり、これは、図２より、反射濃度１．５５以上を十
分に満たす電荷量であることが分かる。When the recording material of the maximum size is passed through the structure of this embodiment, the charge density on the paper surface is Transfer Itr = 10 μA,
Thrust width of recording material χ = 30 cm, process speed v
= 10 cm / s, from the above equation, Itr / (χ · v) = 10 / (30 × 10) = 1/30
It becomes [μC / cm 2 ], and it can be seen from FIG. 2 that this is the amount of electric charge that sufficiently satisfies the reflection density of 1.55 or more.
【００５３】しかし、小サイズの記録材に画像形成をす
る場合は、紙上面電荷密度が２４ｐＣ／ｃｍ2以下とな
って、濃度薄が生じることが実験的に明らかになってい
る。以下、この現象を計算によってさらに詳細に説明す
る。However, it has been experimentally clarified that when an image is formed on a recording material of a small size, the charge density on the upper surface of the paper becomes 24 pC / cm 2 or less and the density becomes low. Hereinafter, this phenomenon will be described in more detail by calculation.
【００５４】図３に、小サイズの記録材を通紙したとき
の転写部の断面を示す。図３において、感光ドラム：感
光層の膜厚ｔD［μｍ］、感光層の体積抵抗率ρD［Ωｃ
ｍ］、転写ベルト：厚さｔB［μｍ］、体積抵抗率ρ
B［Ωｃｍ］、記録材：厚さｔP［μｍ］、体積抵抗率ρ
P［Ωｃｍ］、スラスト幅χ［ｃｍ］、転写部材：スラ
スト幅ｙ［ｃｍ］の諸元を有している。プロセススピー
ド（転写ベルトの移動速度）をｖ［ｃｍ／ｓ］、ニップ
幅を１ｍｍとする。また、感光ドラムの周速はほぼプロ
セススピードと等しい構成となっている。図３は、便宜
上、小サイズ紙を片側基準としたが、中央基準でも何ら
問題はない。FIG. 3 shows a cross section of the transfer portion when a small-sized recording material is passed. In FIG. 3, photosensitive drum: photosensitive layer thickness t D [μm], photosensitive layer volume resistivity ρ D [Ωc
m], transfer belt: thickness t B [μm], volume resistivity ρ
B [Ωcm], recording material: thickness t P [μm], volume resistivity ρ
It has specifications of P [Ωcm], thrust width χ [cm], and transfer member: thrust width y [cm]. The process speed (moving speed of the transfer belt) is v [cm / s], and the nip width is 1 mm. The peripheral speed of the photosensitive drum is substantially equal to the process speed. In FIG. 3, for convenience, the small size paper is used as the one-sided reference, but the center reference has no problem.
【００５５】図３の転写部を等価回路で書くと、図４の
ようになる。図４において、ＲD 1は感光ドラム３のうち
記録材Ｐと接する部分の抵抗、ＲD 2は感光ドラム３のう
ち転写ベルト１３０と直接接する部分の抵抗、ＲPは記
録材Ｐの抵抗、ＲB 1は転写ベルト１３０のうち記録材Ｐ
と接する部分の抵抗、ＲB 2は転写ベルト１３０のうち感
光ドラム３と直接接する部分の抵抗である。The transfer portion of FIG. 3 can be written in an equivalent circuit as shown in FIG. In FIG. 4, R D 1 is the resistance of the portion of the photosensitive drum 3 in contact with the recording material P, R D 2 is the resistance of the portion of the photosensitive drum 3 in direct contact with the transfer belt 130, R P is the resistance of the recording material P, R B 1 is the recording material P of the transfer belt 130.
And R B 2 is the resistance of the portion of the transfer belt 130 in direct contact with the photosensitive drum 3.
【００５６】画像形成中、転写電流はＲD 1→ＲP→ＲB 1
というパスか、ＲD 2→ＲB 2というパスを流れる。記録材
を流れる電流は、これらのパスの比抵抗を求めることで
得られる。During image formation, the transfer current is R D 1 → R P → R B 1
Or a path of R D 2 → R B 2 . The current flowing through the recording material can be obtained by obtaining the specific resistance of these paths.
【００５７】そこで、それぞれの抵抗を求めるとつぎの
ようになる。Then, the respective resistances are obtained as follows.
【００５８】
感光ドラム：
ＲD 1＝ρD×（ｔD×１０-6×１０2）／（０．１×χ）
＝（ｔD／χ）・ρD・１０-3［Ω］ ・・・（１）
ＲD 2＝ρD×（ｔD・×１０-6×１０2）／｛０．１×（ｙ−χ）｝
＝｛ｔD／（ｙ−χ）｝・ρD・１０-3［Ω］ ・・・（２）
記録材：
ＲP＝ρP×（ｔP×１０-6×１０2）／（０．１×χ）
＝（ｔP／χ）・ρP・１０-3［Ω］ ・・・（３）
転写ベルト：
ＲB 1＝ρB×（ｔB×１０-6×１０2）／（０．１×χ）
＝（ｔB／χ）・ρB・１０-3［Ω］ ・・・（４）
ＲB 2＝ρB×（ｔB×１０-6×１０2）／｛０．１×（ｙ−χ）｝
＝｛ｔB／（ｙ−χ）｝・ρB・１０-3［Ω］ ・・・（５）
従って、通紙部と非通紙部との抵抗比から、それぞれに
流れる電流の比が式（６）のように求まる。Photosensitive drum: R D 1 = ρ D × (t D × 10 −6 × 10 2 ) / (0.1 × χ) = (t D / χ) · ρ D · 10 −3 [Ω] · ·· (1) R D 2 = ρ D × (t D · × 10 -6 × 10 2) / {0.1 × (y-χ)} = {t D / (y-χ)} · ρ D · 10 −3 [Ω] (2) Recording material: R P = ρ P × (t P × 10 −6 × 10 2 ) / (0.1 × χ) = (t P / χ) · ρ P · 10 −3 [Ω] (3) Transfer belt: R B 1 = ρ B × (t B × 10 −6 × 10 2 ) / (0.1 × χ) = (t B / χ) · ρ B · 10 -3 [Ω ] ··· (4) R B 2 = ρ B × (t B × 10 -6 × 10 2) / {0.1 × (y-χ)} = {t B / (Y−χ)} · ρ B · 10 −3 [Ω] (5) Therefore, from the resistance ratio between the paper passing portion and the non-paper passing portion, the ratio of the currents flowing through each is expressed by the equation (6). Is obtained.
【００５９】
電流比：
紙部：非紙部＝１／（ＲD 1＋ＲP＋ＲB 1）：１／（ＲD 2＋ＲB 2）
・・・（６）
これより、記録材に流れる電流は、転写電流をＩtrとす
ると、式（７）のようになる。[0059] Current ratio: Paper unit: Hikami unit = 1 / (R D 1 + R P + R B 1): 1 / (R D 2 + R B 2) ··· (6) From this, the current flowing through the recording material When the transfer current is Itr, is expressed by equation (7).
【００６０】
紙部電流＝Ｉtr×｛１／（ＲD 1＋ＲP＋ＲB 1）｝／
｛１／（ＲD 1＋ＲP＋ＲB 1）＋１／（ＲD 2＋ＲB 2）｝
＝｛（ＲD 2＋ＲB 2）／（ＲD 1＋ＲD 2＋ＲB 1＋ＲB 2＋ＲP）｝
×Ｉtr［μＡ］ ・・・（７）
これより、紙上面電荷密度は式（８）のように表すこと
ができる。Paper current = Itr × {1 / (R D 1 + R P + R B 1 )} / {1 / (R D 1 + R P + R B 1 ) + 1 / (R D 2 + R B 2 )} = { (R D 2 + R B 2 ) / (R D 1 + R D 2 + R B 1 + R B 2 + R P)} × Itr [μA] ··· (7) from which, on paper surface charge density formula (8) Can be expressed as
【００６１】
紙上面電荷密度＝｛（ＲD 2＋ＲB 2）／（ＲD 1＋ＲD 2＋ＲB 1＋ＲB 2＋ＲP）｝
×Ｉtr｛１／（ｖ・χ）｝［μＡ］ ・・・（８）
図５は、式（８）を用いて、紙幅χ［ｃｍ］を変化させ
たとき、紙上面電荷密度がどのように変わるかを示した
図である。他のパラメータの値を参考に示すと、ｔD＝
２０［μｍ］、ρD＝１０14［Ωｃｍ］、ｔB＝８０［μ
ｍ］、ρB＝１０ 13［Ωｃｍ］、ｔP＝１００［μｍ］、
ρP＝１０14［Ωｃｍ］、ｙ＝３０［ｃｍ］、ｖ＝１０
［ｃｍ／ｓ］、ニップ幅＝１ｍｍである。[0061]
Paper surface charge density = {(RD 2+ RB 2) / (RD 1+ RD 2+ RB 1+ RB 2+ RP)}
× Itr {1 / (v · χ)} [μA] (8)
FIG. 5 shows that the paper width χ [cm] is changed by using the equation (8).
Showed how the charge density on the paper surface changes when
It is a figure. When referring to the values of other parameters, tD=
20 [μm], ρD= 1014[Ωcm], tB= 80 [μ
m], ρB= 10 13[Ωcm], tP= 100 [μm],
ρP= 1014[Ωcm], y = 30 [cm], v = 10
[Cm / s], nip width = 1 mm.
【００６２】これを見ると、通紙する記録材の幅χが２
６．８ｃｍ以下になると、紙上面電荷密度が２４ｐＣ／
ｃｍ2以下となり、濃度薄となって転写不良が発生す
る。従って、幅χが２６．８ｃｍ以下、すなわち記録材
の幅が小さい葉書、縦送りＡ４用紙等に転写不良なく画
像形成を行うには、この条件下では不可能である。Looking at this, the width χ of the recording material passing through is 2
Below 6.8 cm, the charge density on the paper surface is 24 pC /
When the density is less than cm 2 , the density is low and transfer failure occurs. Therefore, under these conditions, it is impossible to form an image on a postcard, a longitudinal feed A4 paper or the like having a width χ of 26.8 cm or less, that is, a recording material having a small width, without transfer failure.
【００６３】そこで、本発明では、図６に示すように、
転写ベルト１３０の記録材が担持される通紙部となる領
域Ａに隣り合った非通紙部となる領域Ｂに対し、転写前
に予め電荷を蓄積（付与）しておくことにより、最大サ
イズ幅以下の記録材に画像形成する際の転写時に、記録
材に適切な電荷量を安定に供給して、良好な転写を行え
るようになった。以下、これについて詳述する。Therefore, in the present invention, as shown in FIG.
The maximum size can be obtained by preliminarily accumulating (giving) electric charges to a region B, which is a non-paper-passing part, adjacent to a region A, which is a paper-passing part on which the recording material is carried, of the transfer belt 130 before transfer. At the time of transfer when an image is formed on a recording material having a width equal to or less than a width, it becomes possible to stably supply an appropriate amount of charge to the recording material and perform good transfer. Hereinafter, this will be described in detail.
【００６４】転写ベルト１３０は誘電体により形成され
ているために、たとえば図７のような実験室的な電荷供
給装置３０を用い、その１対の電極３１ａ、３１ｂで転
写ベルト１３０の非通紙部を挟んで、一方の電極３１ａ
を取り付けた高圧電源３２により電圧を印加して、非通
紙部に電荷を供給すると、電流計３３でモニターした分
極電流Ｉと定電圧Ｖの印加時間ｔとの関係は、図８に示
すようになり、転写ベルト１３０の表裏面に蓄積された
電荷が多いほど、ベルトのインピーダンスは増大する。Since the transfer belt 130 is made of a dielectric material, for example, a laboratory charge supply device 30 as shown in FIG. 7 is used, and the pair of electrodes 31a and 31b prevents the transfer belt 130 from passing through. One electrode 31a with the portion sandwiched therebetween
When a voltage is applied by the high-voltage power supply 32 attached with a voltage to supply a charge to the non-sheet passing portion, the relationship between the polarization current I monitored by the ammeter 33 and the application time t of the constant voltage V is as shown in FIG. Therefore, the more the charges accumulated on the front and back surfaces of the transfer belt 130, the more the impedance of the belt increases.
【００６５】そこで、本実施例では、最大サイズの記録
材よりも幅が小さい記録材に画像形成する際、転写前の
転写ベルト１３０の非通紙部に予め電荷を蓄積し、電荷
蓄積による非通紙部のインピーダンス増大という現象を
利用して、転写不良を防ぐものである。本実施例では、
転写ベルト１３０に蓄積する電荷の極性は、ベルトの表
面（記録材担持側）で負（トナーの正規の帯電極性と同
極性）、裏面で正（トナーの正規の帯電極性とは逆極
性）である。Therefore, in this embodiment, when an image is formed on a recording material having a width smaller than the maximum size of the recording material, charges are accumulated in advance in the non-sheet passing portion of the transfer belt 130 before the transfer, and the charge is not accumulated. By utilizing the phenomenon that the impedance of the paper passing portion increases, the transfer failure is prevented. In this embodiment,
The polarity of the charge accumulated on the transfer belt 130 is negative on the front surface (recording material carrying side) of the belt (same polarity as the normal charging polarity of the toner) and positive on the back surface (reverse polarity of the normal charging polarity of the toner). is there.
【００６６】上記の電荷蓄積は、図４の等価回路でいう
と、ＲB 2（転写ベルトのうち感光ドラムと直接接する部
分の抵抗）の値を上げることと同値である。すなわち、
ＲB 2を上げることにより、通紙部と非通紙部との抵抗比
が縮まるため、通紙部に流れる単位面積あたりの電流
と、非通紙部に流れる単位面積あたりの電流の差が縮小
する。従って、図９に示すように、ＲB 2 の上昇につれ
て、紙上面電荷密度が上昇し、上述のような転写不良が
起きなくなることが分かる。In the equivalent circuit of FIG. 4, the above charge accumulation is equivalent to increasing the value of R B 2 (the resistance of the portion of the transfer belt that is in direct contact with the photosensitive drum). That is,
By increasing R B 2 , the resistance ratio between the paper passing portion and the non-paper passing portion is reduced, so that the difference between the current per unit area flowing through the paper passing portion and the current per unit area flowing through the non-paper passing portion is reduced. to shrink. Therefore, as shown in FIG. 9, it can be seen that as R B 2 increases, the charge density on the upper surface of the paper increases, and the above-described transfer failure does not occur.
【００６７】転写ベルト１３０の非通紙部の裏面に、転
写前に予め転写時と同極性の電荷を付与するには、第１
画像形成部Ｐａの転写位置の上流側に、たとえば図１０
に示すように、転写ベルト１３０の非通紙部を挟む２本
のローラ３４ａ、３４ｂを設けて、その下ローラ３４ｂ
を接地し、上ローラ３４ａに高圧電源３５からトナーの
正規の帯電極性と同極性の電圧を印加すればよい。To apply a charge of the same polarity as that at the time of transfer in advance to the back surface of the non-sheet passing portion of the transfer belt 130 before the transfer,
On the upstream side of the transfer position of the image forming portion Pa, for example, as shown in FIG.
2, two rollers 34a and 34b sandwiching the non-sheet passing portion of the transfer belt 130 are provided, and the lower roller 34b thereof is provided.
Is grounded, and a voltage having the same polarity as the normal charging polarity of toner may be applied to the upper roller 34a from the high voltage power supply 35.
【００６８】転写ベルト１３０に対する電荷供給を様々
な幅の記録材に対応して実施できるように、上ローラ３
４ａを、たとえば図１１に示すようなローラ３００とす
ることができる。本ローラ３００は、導電性の円筒をス
ラスト方向に切り欠き量が多くなるように切り欠いて、
ローラ３００のスラスト方向の長さを周方向で連続的に
変化するようにしている。The upper roller 3 is provided so that the charge can be supplied to the transfer belt 130 corresponding to recording materials of various widths.
4a may be a roller 300 as shown in FIG. 11, for example. The roller 300 is formed by cutting out a conductive cylinder in the thrust direction so that the cutout amount increases.
The length of the roller 300 in the thrust direction is continuously changed in the circumferential direction.
【００６９】このローラ３００は、その中心軸３０１を
図示しない取り付け部に枢着することにより、周方向に
回転可能とされ、中心軸３０１の一端に取り付けたギヤ
３０２と、これに歯合した駆動装置３０４側のギヤ３０
３を介して、駆動装置３０４の正逆転モータにより回転
される。その回転量は制御手段であるＣＰＵ３０５に制
御される。The roller 300 is rotatable in the circumferential direction by pivotally attaching the central shaft 301 to a mounting portion (not shown), and a gear 302 mounted on one end of the central shaft 301 and a driving gear meshed with the gear 302. Gear 30 on device 304 side
3 is rotated by the forward / reverse rotation motor of the drive device 304. The rotation amount is controlled by the CPU 305 which is a control means.
【００７０】手差し給紙部あるいはカセット給紙部にお
いて、常時記録材Ｐの紙幅が検知され、その紙幅情報が
ＣＰＵ３０５へ受け渡され、ＣＰＵ３０５は、紙幅情報
に従って駆動装置３０４のモータの回転角を制御し、駆
動装置３０４のモータが回転してローラ３００を所定角
度だけ回転し、転写ベルト１３０の非通紙部の幅に合っ
た長さのローラ３００の周面が転写ベルト１３０に向け
られ、当接される。In the manual paper feeding unit or the cassette paper feeding unit, the paper width of the recording material P is always detected, and the paper width information is transferred to the CPU 305. The CPU 305 controls the rotation angle of the motor of the drive unit 304 according to the paper width information. Then, the motor of the driving device 304 rotates to rotate the roller 300 by a predetermined angle, and the peripheral surface of the roller 300 having a length that matches the width of the non-sheet passing portion of the transfer belt 130 is directed toward the transfer belt 130. Contacted.
【００７１】このローラ３００は、小サイズの記録材へ
の画像形成時のみ転写ベルト１３０に当接し、それ以外
のときは転写ベルトから離間しておくのが好ましい。It is preferable that the roller 300 is in contact with the transfer belt 130 only when an image is formed on a recording material of a small size, and is separated from the transfer belt otherwise.
【００７２】転写ベルト１３０に予め蓄積した電荷は、
転写ベルト自体が除電工程に至るまで消滅しないことが
望ましく、そのためには帯電緩和時間の長い材料を選定
することが好ましい。従って、体積固有抵抗値の高い材
料、具体的には１．０×１０ 13〜１．０×１０17Ωｃｍ
の材料が好適である。The charges previously accumulated on the transfer belt 130 are
The transfer belt itself may not disappear until the static elimination process.
Desirable, for that purpose select a material with a long charge relaxation time
Preferably. Therefore, a material with a high volume resistivity
Fee, specifically 1.0 x 10 13~ 1.0 x 1017Ω cm
Are preferred.
【００７３】本実施例では、図１０に示した下ローラ３
４ｂを接地し、上ローラ３４ａまたは図１１のローラ３
００に負電圧を印加したが、その逆に、上ローラ３４
ａ、ローラ３００に正電圧を印加し、下ローラ３４ｂを
接地するようにしても何ら問題ない。In this embodiment, the lower roller 3 shown in FIG.
4b is grounded, and the upper roller 34a or the roller 3 in FIG.
00, a negative voltage was applied to the upper roller 34,
There is no problem even if a positive voltage is applied to the roller 300 and the lower roller 34b is grounded.
【００７４】記録材の紙幅（スラスト方向長さχ）の検
知は、機械式センサーや光学式センサーを用いて自動的
に判別するほか、操作者が操作部等から紙幅を入力する
ことにより検知に代えてもよい。The paper width (length in the thrust direction χ) of the recording material is detected automatically by using a mechanical sensor or an optical sensor, and the operator inputs the paper width from the operation unit or the like. You may change.
【００７５】また、以上では記録材担持体として転写ベ
ルトを示したが、転写ドラムであってもよい。像担持体
は、感光ドラムなどの電子写真感光体に限らず、静電記
録における誘電体であってもよい。Further, although the transfer belt is shown as the recording material carrier in the above, it may be a transfer drum. The image carrier is not limited to an electrophotographic photosensitive member such as a photosensitive drum, but may be a dielectric in electrostatic recording.
【００７６】現像器１（１ａ〜１ｄ）としては、いずれ
の方式の現像方法であってもよい。The developing device 1 (1a-1d) may be any type of developing method.
【００７７】一般に、現像方法は一成分現像法と二成分
現像法に大別され、一成分現像法は、非磁性トナーにつ
いてはブレード等で現像スリーブ上にコーティングし、
磁性トナーについては磁気力によって現像スリーブ上に
コーティングし、現像スリーブの回転により像担持体と
対向した現像部に搬送し、トナーを像担持体と非接触状
態で現像する一成分非接触現像法、像担持体と接触状態
で現像する一成分接触現像法があり、二成分現像法は、
トナー粒子と磁性キャリアを混合した二成分現像剤を使
用し、これを磁気力で現像スリーブ上にコーティング
し、現像スリーブにより現像部に搬送して、現像剤を像
担持体と非接触状態で現像する二成分非接触現像法と、
像担持体と接触状態で現像する二成分接触現像法とがあ
る。画像の高画質化や高安定性の面から、二成分接触現
像法が多く用いられる。Generally, the developing method is roughly classified into a one-component developing method and a two-component developing method. In the one-component developing method, a non-magnetic toner is coated on a developing sleeve with a blade or the like.
Magnetic toner is coated on a developing sleeve by magnetic force, and is conveyed to a developing unit facing the image carrier by the rotation of the developing sleeve, and the toner is developed in a non-contact state with the image carrier, the one-component non-contact developing method, There is a one-component contact developing method that develops in contact with the image carrier, and the two-component developing method is
Using a two-component developer in which toner particles and magnetic carrier are mixed, this is coated on the developing sleeve with magnetic force and conveyed to the developing section by the developing sleeve to develop the developer in a non-contact state with the image carrier. Two-component non-contact developing method,
There is a two-component contact developing method in which development is carried out in contact with the image carrier. The two-component contact developing method is often used from the viewpoint of high image quality and high stability.
【００７８】本実施例では、必要な紙上面電荷密度の値
を２４ｐＣ／ｃｍ2としたが、必要な紙上面電荷密度
は、たとえばトナーの持つ摩擦帯電電荷量（トリボ）や
トナーの種類、あるいは画像形成装置の設置環境等によ
って変化するため、これに限定されるものではない。In the present embodiment, the value of the required paper top surface charge density is set to 24 pC / cm 2 , but the required paper top surface charge density is, for example, the triboelectric charge amount (tribo) of the toner, the type of toner, or The present invention is not limited to this because it changes depending on the installation environment of the image forming apparatus.
【００７９】また、本実施例では、転写前に帯電する領
域を転写ベルト１３０の非通紙部のみとしたが、上述の
ように、転写不良が発生しないように帯電するのであれ
ば、転写前の帯電領域はこの限りでない。この場合、通
紙部よりも非通紙部に付与する電荷量を多くする。In this embodiment, the area to be charged before transfer is only the non-sheet passing portion of the transfer belt 130. However, as described above, if the area is charged so that the transfer failure does not occur, before transfer. The charged area of is not limited to this. In this case, the amount of electric charge applied to the non-sheet passing portion is made larger than that of the sheet passing portion.
【００８０】また、本発明によれば、画像形成装置は、
感光体上に順次トナー像を形成し、転写ドラム上に担持
した記録材に順次転写する転写ドラム方式でもよい。こ
の場合、転写ドラムを構成する転写シートの非通紙部の
領域に所望の帯電を施せばよい。Further, according to the present invention, the image forming apparatus is
A transfer drum system may also be used in which toner images are sequentially formed on a photoconductor and sequentially transferred to a recording material carried on a transfer drum. In this case, a desired charge may be applied to the non-sheet passing area of the transfer sheet that constitutes the transfer drum.
【００８１】１つあるいはそれ以上の感光ドラム上にト
ナー像を順次形成し、そのトナー像を中間転写体上に順
次一次転写した後、記録材に一括して二次転写する中間
転写方式であっても、二次転写部へ記録材を搬送するた
めに上述の記録材担持体を用いる場合は、本発明が適用
できる。This is an intermediate transfer system in which toner images are sequentially formed on one or more photosensitive drums, the toner images are sequentially primary-transferred onto an intermediate transfer member, and then secondary-transferred collectively onto a recording material. However, the present invention can be applied when the above-described recording material carrier is used to convey the recording material to the secondary transfer portion.
【００８２】転写帯電器に定電圧電源を接続して、転写
帯電器に印加する電圧を定電圧制御する場合において
も、本発明を適用することができる。The present invention can also be applied to the case where a constant voltage power source is connected to the transfer charger to control the voltage applied to the transfer charger by a constant voltage.
【００８３】また、１つの感光ドラムを設置し、この感
光ドラム上のトナー像（たとえばブラックトナー像）を
転写ベルトに担持搬送される記録材に転写する画像形成
装置（たとえば白黒画像形成装置）にも、本発明は適用
できる。An image forming apparatus (for example, a black and white image forming apparatus) that installs one photosensitive drum and transfers a toner image (for example, a black toner image) on the photosensitive drum onto a recording material carried and conveyed by a transfer belt is used. However, the present invention can be applied.
【００８４】実施例２
本実施例の構成は、実施例１とほぼ同様であるが、記録
材の種類および／または装置内の湿度（および温度）に
応じて、転写前に転写ベルト１３０を予め帯電する帯電
量を制御する点が異なる。Example 2 The configuration of this example is almost the same as that of Example 1, but the transfer belt 130 is preliminarily set before the transfer depending on the type of recording material and / or the humidity (and temperature) in the apparatus. The difference is that the amount of electrification is controlled.
【００８５】記録材としてＯＨＴ（オーバーヘッドプロ
ジェクター用透明樹脂シート）を用いる場合と、普通紙
を用いる場合とでは、同一環境（温湿度）であれば、転
写時、非通紙部へ流れる電流は異なり、相対的に体積抵
抗率の高い記録材（ＯＨＴ）を用いる場合、転写不良が
発生してしまうことがあった。When an OHT (transparent resin sheet for overhead projector) is used as a recording material and when plain paper is used, the current flowing to the non-sheet passing portion at the time of transfer is different under the same environment (temperature and humidity). When a recording material (OHT) having a relatively high volume resistivity is used, transfer failure may occur.
【００８６】そこで、本実施例においては、ローラ３４
ａ認可する電圧を記録材の種類に応じて、制御手段とし
てのＣＰＵにより制御することで、上記転写不良を防止
することができた。具体的には、記録材としてＯＨＴを
用いる場合の方を、記録材として普通紙を用いる場合よ
りも、ローラ３４ａに印加する電圧を大きくして、転写
ベルト１３０の非通紙部の帯電量を大きくした。Therefore, in the present embodiment, the roller 34
a. The transfer failure can be prevented by controlling the approved voltage according to the type of the recording material by the CPU as the control means. Specifically, in the case where OHT is used as the recording material, the voltage applied to the roller 34a is made larger than the case where plain paper is used as the recording material, and the charge amount of the non-sheet passing portion of the transfer belt 130 is increased. I made it bigger.
【００８７】また、同種の記録材であっても、環境によ
り記録材の体積抵抗率が相対的に高くなり（低湿環境で
顕著）、転写不良が発生してしまうことがあった。Further, even with the same kind of recording material, the volume resistivity of the recording material becomes relatively high depending on the environment (noticeable in a low humidity environment), and a transfer failure may occur.
【００８８】そこで、本実施例においては、上記記録材
の種類に応じた制御の他に、装置内の湿度（および温
度）に応じて、ローラ３４ａに印加する電圧をＣＰＵに
より制御することで、上記転写不良を防止することがで
きた。Therefore, in this embodiment, in addition to the control according to the type of the recording material, the voltage applied to the roller 34a is controlled by the CPU according to the humidity (and temperature) in the apparatus, The transfer failure could be prevented.
【００８９】以上の実施例１、２においては、記録材を
転写ベルトに担持させる前に、転写ベルトの非通紙部の
みにプラスの電荷を与えていたが、これに限られない。
たとえば、図１６（ａ）、（ｂ）、（ｃ）のように、転
写ベルト１３０を帯電させて転写不良を防止してもよ
い。In Examples 1 and 2 above, the positive charge was applied only to the non-sheet passing portion of the transfer belt before the recording material was carried on the transfer belt, but the present invention is not limited to this.
For example, as shown in FIGS. 16A, 16B, and 16C, the transfer belt 130 may be charged to prevent transfer failure.
【００９０】図１６においても、転写帯電器に印加され
る電圧の極性はプラス、すなわち転写帯電器から転写ベ
ルトに付与される電荷の極性はプラスである。つまり、
非通紙部に付与する電荷量を、通紙部に付与する電荷量
よりも、プラスの方向（転写帯電器から付与される電荷
の極性）に大きくすればよい。Also in FIG. 16, the polarity of the voltage applied to the transfer charger is positive, that is, the polarity of the charge applied from the transfer charger to the transfer belt is positive. That is,
The amount of charge applied to the non-sheet passing portion may be made larger than the amount of charge applied to the sheet passing portion in the positive direction (the polarity of the charge applied from the transfer charger).
【００９１】転写ベルト上の電荷量分布の求め方として
は、ＴＤＫ（株）製の表面電位センサ（ＥＦＳ−２２
Ｄ、ＥＦＳ−３１Ｄ）を用いて、転写ベルトの電位Ｖを
スラスト方向の各ポイントで測定し、予め分かっている
転写ベルトの静電容量Ｃから、各ポイントの電荷量が求
まる。As a method of obtaining the charge amount distribution on the transfer belt, a surface potential sensor (EFS-22 manufactured by TDK Corp.) is used.
D, EFS-31D), the potential V of the transfer belt is measured at each point in the thrust direction, and the charge amount at each point is obtained from the electrostatic capacitance C of the transfer belt which is known in advance.
【００９２】[0092]
【発明の効果】以上説明したように、本発明によれば、
記録材担持体の記録材搬送方向に関し、転写位置の上流
側に電荷付与手段を設置して、記録材担持体の記録材が
位置しない非通紙部の表裏面に転写時と同極性の電荷
を、記録材が転写位置に至る前に付与するようにしたの
で、接触式の転写手段により、記録材のサイズに関係な
く通紙部に転写電流を確保して、像担持体上の可視画像
を記録材に良好に転写でき、転写不良のない高品質な画
像を得ることができる。As described above, according to the present invention,
With respect to the recording material conveyance direction of the recording material carrier, a charge applying unit is installed on the upstream side of the transfer position, and the same polarity as that at the time of transfer is applied to the front and back surfaces of the non-sheet passing portion where the recording material of the recording material carrier is not located Is applied before the recording material reaches the transfer position, the contact-type transfer means secures a transfer current in the paper passing portion regardless of the size of the recording material, and a visible image on the image carrier is obtained. Can be satisfactorily transferred to a recording material, and a high-quality image without transfer defects can be obtained.
【図１】本発明が適用可能な画像形成装置を示す構成図
である。FIG. 1 is a configuration diagram showing an image forming apparatus to which the present invention is applicable.
【図２】紙上面電荷密度と画像濃度の関係を示す図であ
る。FIG. 2 is a diagram showing a relationship between a paper top surface charge density and an image density.
【図３】小サイズ紙転写時の転写部を示す断面図であ
る。FIG. 3 is a cross-sectional view showing a transfer portion at the time of transferring small size paper.
【図４】図３の転写部の等価回路を示す図である。FIG. 4 is a diagram showing an equivalent circuit of the transfer unit in FIG.
【図５】紙上面電荷密度と紙幅χとの関係を示す図であ
る。FIG. 5 is a diagram showing the relationship between the paper top surface charge density and the paper width χ.
【図６】本発明で転写前に行う転写ベルトの非通紙部へ
の転写時と同極性の電荷の供給を示す説明図である。FIG. 6 is an explanatory diagram showing supply of electric charges having the same polarity as during transfer to a non-sheet passing portion of a transfer belt before transfer according to the present invention.
【図７】本発明で行う転写前の非通紙部への電荷供給に
使用した実験室的な電荷供給装置を示す概念図である。FIG. 7 is a conceptual diagram showing a laboratory-like charge supply device used for supplying charges to a non-sheet passing portion before transfer performed in the present invention.
【図８】転写ベルトへの定電圧印加時間と電流との関係
を示す図である。FIG. 8 is a diagram showing a relationship between a constant voltage application time to a transfer belt and a current.
【図９】転写ベルトのうちの感光ドラムと直接接する部
分の抵抗ＲB 2と紙上電荷量との関係を示す図である。FIG. 9 is a diagram showing a relationship between a resistance R B 2 of a portion of the transfer belt which is in direct contact with the photosensitive drum and a charge amount on paper.
【図１０】本発明の一実施例における転写前の非通紙部
への電荷供給方法を示す説明図である。FIG. 10 is an explanatory diagram showing a method of supplying electric charges to a non-sheet passing portion before transfer in an embodiment of the present invention.
【図１１】本発明による電荷供給に使用するローラの好
ましい変形例を示す斜視図である。FIG. 11 is a perspective view showing a preferable modified example of the roller used for supplying electric charge according to the present invention.
【図１２】図１の画像形成装置の転写部を示す断面図で
ある。12 is a sectional view showing a transfer portion of the image forming apparatus of FIG.
【図１３】図１２の転写部による時間Δｔ秒間での転写
の記録材の対象面積を示す斜視図である。13 is a perspective view showing a target area of a recording material for transfer in a time Δt seconds by the transfer section of FIG.
【図１４】小サイズ紙転写時の転写部を示す断面図であ
る。FIG. 14 is a cross-sectional view showing a transfer portion at the time of transferring small size paper.
【図１５】感光ドラムの表面電位を示す図である。FIG. 15 is a diagram showing a surface potential of a photosensitive drum.
【図１６】本発明の変形例を示す図である。FIG. 16 is a diagram showing a modified example of the present invention.
３、３ａ〜３ｄ 感光ドラム ２４、２４ａ〜２４ｄ 転写帯電器 ３４ａ、３４ｂ ローラ ３５ 高圧電源 １３０ 転写ベルト ３００ ローラ Ｐ 記録材 3, 3a-3d photosensitive drum 24, 24a to 24d Transfer charger 34a, 34b rollers 35 high voltage power supply 130 transfer belt 300 rollers P recording material
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7，ＤＢ名) G03G 15/16 G03G 15/01 114 ─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. 7 , DB name) G03G 15/16 G03G 15/01 114
Claims (28)
する記録材担持体と、前記像担持体上の像を前記記録材
担持体上に担持された記録材に静電的に転写するため
に、前記録材担持体の記録材を担持する側とは反対側の
所定の極性の電荷を付与する第１の電荷付与手段と、記
録材が前記記録材担持体に担持される前に、前記記録材
担持体の記録材を担持する側とは反対側に電荷を付与す
る第２の電荷付与手段とを有する画像形成装置であっ
て、 記録材の搬送方向と実質的に直交する方向において、前
記記録材担持体の前記第１の電荷付与手段により電荷が
付与される領域のうち、前記記録材担持体の記録材を担
持する第１の領域よりも外側の第２の領域の電荷量が、
前記第１の領域の電荷量に比べて前記所定の極性寄りに
大きくなるように、前記第２の電荷付与手段は前記記録
材担持体に電荷を付与することを特徴とする画像形成装
置。1. An image carrier for carrying an image, a recording material carrier for carrying a recording material, and an image on the image carrier electrostatically on the recording material carried on the recording material carrier. For transfer, a first charge applying unit for applying an electric charge of a predetermined polarity on the side of the pre-recording material carrier opposite to the side carrying the recording material, and the recording material are carried on the recording material carrier. An image forming apparatus having a second charge applying unit for applying an electric charge to a side opposite to a side of the recording material carrying member carrying the recording material, the image forming apparatus being substantially orthogonal to a conveying direction of the recording material. A second area outside the first area of the recording material carrier, on which the recording material is carried, by the first charge applying means. Charge amount of
The image forming apparatus, wherein the second charge applying unit applies an electric charge to the recording material carrier so that the second charge applying unit increases the electric charge amount toward the predetermined polarity as compared with the electric charge amount in the first region.
付与手段に印加する電圧を制御する制御手段を有する請
求項１の画像形成装置。2. The image forming apparatus according to claim 1, further comprising a control unit that controls a voltage applied to the second charge applying unit according to the type of recording material.
を有し、前記制御手段は、前記記録材検知手段による検
知結果に応じて前記第２の電荷付与手段に印加する電圧
を制御する請求項２の画像形成装置。3. A recording material detection unit for detecting the type of recording material, wherein the control unit controls the voltage applied to the second charge applying unit according to the detection result of the recording material detection unit. The image forming apparatus according to claim 2.
付与手段により前記記録材担持体に付与される電荷量を
制御する制御手段を有する請求項１の画像形成装置。4. The image forming apparatus according to claim 1, further comprising a control unit that controls the amount of electric charge applied to the recording material carrier by the second electric charge applying unit according to the type of recording material.
を有し、前記制御手段は、前記記録材検知手段による検
知結果に応じて前記第２の電荷付与手段により前記記録
材担持体に付与される電荷量を制御する請求項４の画像
形成装置。5. A recording material detection means for detecting the type of recording material, wherein the control means causes the second charge applying means to apply the recording material to the recording material carrier in accordance with the detection result of the recording material detection means. The image forming apparatus according to claim 4, wherein the amount of applied charges is controlled.
に印加する電圧を制御する制御手段を有する請求項１の
画像形成装置。6. The image forming apparatus according to claim 1, further comprising a control unit that controls a voltage applied to the second charge applying unit according to humidity.
記制御手段は、前記湿度検知手段による検知結果に応じ
て前記第２の電荷付与手段に印加する電圧を制御する請
求項６の画像形成装置。7. The image according to claim 6, further comprising humidity detecting means for detecting humidity, wherein the control means controls a voltage applied to the second charge applying means in accordance with a detection result of the humidity detecting means. Forming equipment.
荷付与手段に印加する電圧を制御する制御手段を有する
請求項１の画像形成装置。8. The image forming apparatus according to claim 1, further comprising a control unit that controls a voltage applied to the second charge applying unit according to temperature and humidity.
段を有し、前記制御手段は、前記温湿度検知手段による
検知結果に応じて前記第２の電荷付与手段に印加する電
圧を制御する請求項８の画像形成装置。9. A temperature / humidity detecting means for detecting temperature and humidity is provided, and the control means controls a voltage applied to the second charge applying means in accordance with a detection result of the temperature / humidity detecting means. Item 8. The image forming apparatus according to item 8.
段により前記記録材担持体に付与される電荷量を制御す
る制御手段を有する請求項１の画像形成装置。10. The image forming apparatus according to claim 1, further comprising control means for controlling an amount of electric charge applied to the recording material carrier by the second electric charge applying means in accordance with humidity.
前記制御手段は、前記湿度検知手段による検知結果に応
じて前記第２の電荷付与手段により前記記録材担持体に
付与される電荷量を制御する請求項１０の画像形成装
置。11. A humidity detecting means for detecting humidity,
The image forming apparatus according to claim 10, wherein the control unit controls the amount of electric charge applied to the recording material carrier by the second electric charge applying unit according to a detection result of the humidity detecting unit.
電荷付与手段により前記記録材担持体に付与される電荷
量を制御する制御手段を有する請求項１の画像形成装
置。12. The image forming apparatus according to claim 1, further comprising control means for controlling an amount of electric charge applied to the recording material carrier by the second electric charge applying means in accordance with temperature and humidity.
手段を有し、前記制御手段は、前記温湿度検知手段によ
る検知結果に応じて前記第２の電荷付与手段により前記
記録材担持体に付与される電荷量を制御する請求項１２
の画像形成装置。13. A temperature / humidity detecting means for detecting temperature and humidity is provided, and the control means applies the second charge applying means to the recording material carrier according to a detection result of the temperature / humidity detecting means. 13. Controlling the amount of charge applied.
Image forming device.
前記第２の電荷付与手段により付与される電荷量はゼロ
である請求項１の画像形成装置。14. The image forming apparatus according to claim 1, wherein the charge amount applied to the first region of the recording material carrier by the second charge applying means is zero.
録材担持体の前記第１の領域に付与される電荷の極性
は、前記第１の電荷付与手段により前記記録材担持体に
付与される電荷の極性とは逆極性である請求項１の画像
形成装置。15. The polarity of the charges applied to the first region of the recording material carrier by the second charge applying device is applied to the recording material carrier by the first charge applying device. The image forming apparatus according to claim 1, wherein the polarity of the charges is opposite to that of the charges.
録材担持体の前記第２の領域に付与される電荷の極性
は、前記第１の電荷付与手段により前記記録材担持体に
付与される電荷の極性とは逆極性である請求項１５の画
像形成装置。16. The polarity of the charge applied to the second region of the recording material carrier by the second charge applying device is applied to the recording material carrier by the first charge applying device. The image forming apparatus according to claim 15, wherein the polarity of the charges is opposite to that of the charges.
録材担持体の前記第２の領域に付与される電荷量の絶対
値は、前記第２の電荷付与手段により前記記録材担持体
の前記第１の領域に付与される電荷量の絶対値よりも小
さい請求項１６の画像形成装置。17. The absolute value of the amount of charge applied to the second region of the recording material carrier by the second charge applying means is the absolute value of the charge amount of the recording material carrier by the second charge applying means. The image forming apparatus according to claim 16, wherein the amount of charge applied to the first region is smaller than the absolute value.
録材担持体の前記第１の領域に付与される電荷の極性
は、前記第１の電荷付与手段により前記記録材担持体に
付与される電荷の極性と同極性である請求項１の画像形
成装置。18. The polarity of the charge applied to the first region of the recording material carrier by the second charge applying means is applied to the recording material carrier by the first charge applying means. The image forming apparatus according to claim 1, which has the same polarity as the electric charge.
録材担持体の前記第２の領域に付与される電荷の極性
は、前記第１の電荷付与手段により前記記録材担持体に
付与される電荷の極性と同極性である請求項１８の画像
形成装置。19. The polarity of the charge applied to the second region of the recording material carrier by the second charge applying means is applied to the recording material carrier by the first charge applying means. 19. The image forming apparatus according to claim 18, which has the same polarity as the electric charge.
録材担持体の前記第２の領域に付与される電荷量の絶対
値は、前記第２の電荷付与手段により前記記録材担持体
の前記第１の領域に付与される電荷量の絶対値よりも大
きい請求項１９の画像形成装置。20. The absolute value of the amount of charge applied to the second area of the recording material carrier by the second charge applying means is the absolute value of the charge amount of the recording material carrier by the second charge applying means. 20. The image forming apparatus according to claim 19, wherein the image forming apparatus is larger than the absolute value of the amount of charge applied to the first area.
録材担持体の前記第２の領域に付与される電荷の極性
は、前記第１の電荷付与手段により前記記録材担持体に
付与される電荷の極性とは逆極性である請求項１８の画
像形成装置。21. The polarity of the charge applied to the second region of the recording material carrier by the second charge applying device is applied to the recording material carrier by the first charge applying device. The image forming apparatus according to claim 18, wherein the polarity of the charges is opposite to that of the charges.
材担持体の記録材を担持する側に電荷を付与する第１の
電荷付与部材と、前記記録材担持体を介して前記第１の
電荷付与部材に対向するように設けられ、前記記録材担
持体の記録材を担持する側とは反対側に電荷を付与する
第２の電荷付与部材とを備える請求項１の画像形成装
置。22. The second charge imparting means includes a first charge imparting member that imparts an electric charge to a side of the recording material carrying body that carries the recording material, and the first charge imparting member through the recording material carrying body. The image forming apparatus according to claim 1, further comprising a second charge applying member that is provided so as to face the charge applying member and that applies an electric charge to a side of the recording material carrier opposite to a side on which the recording material is carried.
方向において、前記第２の電荷付与手段により前記記録
材担持体に電荷を付与する領域は、記録材の長さに応じ
て可変である請求項１の画像形成装置。23. A region in which a charge is applied to the recording material carrier by the second charge applying means in a direction substantially orthogonal to the recording material conveying direction is variable according to the length of the recording material. The image forming apparatus according to claim 1.
方向において、前記第２の電荷付与手段は、前記記録材
担持体の前記第２の領域にのみ電荷を付与する請求項２
３の画像形成装置。24. The second electric charge applying means applies electric charges only to the second region of the recording material carrier in a direction substantially orthogonal to a recording material conveying direction.
3. The image forming apparatus of 3.
極性とは逆極性である請求項１の画像形成装置。25. The image forming apparatus according to claim 1, wherein the image carrier has a charging polarity opposite to the predetermined polarity.
13〜１０17Ωｃｍである請求項１の画像形成装置。26. The volume resistivity of the recording material carrier is 10
The image forming apparatus according to claim 1, which has a density of 13 to 10 17 Ωcm.
に複数色の像が順次重ねて転写される請求項１の画像形
成装置。27. The image forming apparatus according to claim 1, wherein images of a plurality of colors are sequentially transferred onto the recording material carried by the recording material carrying body in an overlapping manner.
担持するために複数設けられ、前記複数の像担持体から
前記記録材担持体に担持された記録材に複数色の像が順
次重ねて転写される請求項２７の画像形成装置。28. A plurality of the image carriers are provided to respectively carry images of a plurality of colors, and a plurality of images of a plurality of colors are sequentially superposed on the recording material carried by the recording material carrier from the plurality of image carriers. 28. The image forming apparatus according to claim 27, which is transferred by transfer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35936899A JP3453541B2 (en) | 1998-12-18 | 1999-12-17 | Image forming device |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10-376011 | 1998-12-18 | ||
| JP37601198 | 1998-12-18 | ||
| JP35936899A JP3453541B2 (en) | 1998-12-18 | 1999-12-17 | Image forming device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2000235310A JP2000235310A (en) | 2000-08-29 |
| JP3453541B2 true JP3453541B2 (en) | 2003-10-06 |
Family
ID=26580959
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP35936899A Expired - Fee Related JP3453541B2 (en) | 1998-12-18 | 1999-12-17 | Image forming device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3453541B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP6082688B2 (en) * | 2013-12-02 | 2017-02-15 | 京セラドキュメントソリューションズ株式会社 | Image forming apparatus |
| JP5999846B2 (en) * | 2013-12-16 | 2016-09-28 | 京セラドキュメントソリューションズ株式会社 | Image forming apparatus |
-
1999
- 1999-12-17 JP JP35936899A patent/JP3453541B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP2000235310A (en) | 2000-08-29 |
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