JP2004219872A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, which uses a contact electrifying roller, in which bright and uniform images are obtained for a long period of time by removing soiling of the toner, external additives, etc., sticking to an electrifying roller and preventing the accumulation of the soiling, thereby electrifying a photoreceptor drum uniformly and stably for a long period of time. <P>SOLUTION: The toner is first applied (developed) from a developing device onto a photoreceptor drum and the electrifying roller 2 can be coated with the toner without using a bias because of the contact by rotation of the photoreceptor drum 1. The toner remaining after transfer and the soiling of the external additives remaining after the transfer are adsorbed to the applied toner and thereafter the toner is freshly transferred from the roller 2 to the photoreceptor drum 2 to clean the roller 2. Finally, the toner is stored into the developing roller or cleaner. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００７０】
故に、実施例１の接触帯電方式のローラ状帯電部材清掃の実行間隔を、過去１０回の画像形成時の平均湿度が５０％未満の場合は画像形成１０回毎に行い、平均湿度が５０％以上の場合は、画像形成５回毎に行うように設定する。その一例を表２に表しておく。
【００７１】
【表２】

【００７２】
即ち、以上のような帯電部材であるところの帯電ローラ２に蓄積した転写残トナーや転写残外添剤などの汚れを除去を行う実行間隔を環境湿度により変更することで、転写効率の低い環境下に於いては転写残トナーや転写残外添剤などの汚れの帯電ローラ２への早期の蓄積を防止し、転写効率の高い環境下に於いては、感光体ドラム１へのダメージを少しでも抑えることが出来ることとなる。何故なら、感光体ドラム１は帯電ローラ２や転写部材７によるバイアス印加により微小とは言え、ダメージを受けるものであるからである。
【００７３】
このようにして、長期に渡ってムラなく均一で安定した感光ドラム１への帯電を行い、表面電位を維持することにより、長期に渡って鮮明でムラのない画像を得ることができる画像形成装置を提供することが出来るのである。
【００７４】
（第３の実施例）
次に本発明の第３の実施例について説明する。
【００７５】
基本的な構成は実施例１、図１、図３と同様である。本実施例においては、画像形成に用いられる転写材の種類によって、実施例１の接触帯電方式のローラ状帯電部材清掃の実行間隔を変更する。
【００７６】
また、ユーザにより、使用される転写材を設定しておくことにする。
【００７７】
表２に様々な転写材による、転写効率を挙げる。今回実験に使用した画像形成装置においては、表面の粗い紙、厚みある紙（葉書を含む）、ＯＨＴ用紙において、転写効率が下がると言う結果を得た。
【００７８】
故に、表面の粗い紙、厚みある紙（葉書を含む）、ＯＨＴ用紙をユーザが選んだ時には、実施例１の接触帯電方式のローラ状帯電部材清掃の実行間隔を画像形成毎に行い、それ以外の転写材を用いる時には、画像形成５０回毎に行うように設定する。
【００７９】
即ち、以上のような帯電部材であるところの帯電ローラ２に蓄積した転写残トナーや転写残外添剤などの汚れを除去を行う実行間隔を用いられる転写材の種類により変更することで、転写効率の低い転写材を用いても転写残トナーや転写残外添剤などの汚れの帯電ローラ２への早期の蓄積を防止し、転写効率の高い転写材を用いている時に於いては、感光体ドラム１へのダメージを少しでも抑えることが出来ることとなる。何故なら、感光体ドラム１は帯電ローラ２や転写部材７によるバイアス印加により微小とは言え、ダメージを受けるものであるからである。
【００８０】
このようにして、長期に渡ってムラなく均一で安定した感光ドラム１への帯電を行い、表面電位を維持することにより、長期に渡って鮮明でムラのない画像を得ることができる画像形成装置を提供することが出来るのである。
【００８１】
（第４の実施例）
次に本発明の第４の実施例について説明する。
【００８２】
基本的な構成は実施例１、図１、図３と同様であるが、クリーナ９を有するかしないかの違いがあり、その形態は図４である。本実施例に於いては、クリーナ９が存在する。
【００８３】
画像形成の動作においても、感光ドラム１のトナー画像が転写材Ｐの表面に転写されるまでは同様である。また、感光ドラム１の表面から分離されて不図示の像定着手段に送られ、転写トナー画像が転写材Ｐ上に永久固着画像として定着され、プリントあるいはコピーとして機外へ排出されるのも同じである。
【００８４】
しかしながら、転写部通過後の感光ドラム１の表面は、クリーナ９によって残留現像剤やその他の付着物が除去されてクリーニングされ、さらに除電器（除電ランプ）１０によって除電されて初期化され、繰り返して作像に供される画像形成装置に於いても、状況によっては前述の問題を生じることがあり、改善の余地があった。
【００８５】
そこで本実施例における上記問題解決手段は、実施例１〜３と同様に、まずは転写残トナーや転写残外添剤の汚れが蓄積された帯電ローラ２にトナーを塗布し転写残トナーや転写残外添剤の汚れを吸着させ、改めて帯電ローラ２から感光ドラム１にトナーＴを転写し、更に現像装置５に回収するものであるが、クリーナ９が存在する為に、画像形成時のままでは帯電ローラ２にトナーを塗布することが出来ない。その為、本実施例は、実施例１〜３の画像形成装置にクリーナ９が存在するのもであり、同様の接触帯電方式のローラ状帯電部材清掃の実行する間に於いて、クリーナ９を感光ドラム１より離間させておくことにより、実現するものである。
【００８６】
このようにして、長期に渡ってムラなく均一で安定した感光ドラム１への帯電を行い、表面電位を維持することにより、長期に渡って鮮明でムラのない画像を得ることができる画像形成装置を提供することが出来るのである。
【００８７】
（第５の実施例）
次に本発明の第５の実施例について説明する。
【００８８】
基本的な構成は実施例４と同様で、図４のようにクリーナ９を有する画像形成装置である。
【００８９】
異なる所は、帯電ローラ２上にあった転写残トナー、外添剤等の汚れを吸着したトナーＴを、最終的に、現像スリーブ５ａ上に引き寄せ回収するのではなく、クリーナ９に収容すると言うことである。
【００９０】
その為には、実施例４におけるクリーナ９を感光ドラム１より離間させておく状態は、転写残トナーや転写残外添剤の汚れを吸着させる為のトナーを感光ドラム１上に塗布（現像）し、その感光ドラム１上の領域が、クリーナ９の対向位置を通り過ぎる間のみしなければならない。
【００９１】
しかしながら、トナーをクリーナ９で回収させる訳であるので、廃トナーを再利用する場合は、トナーの減り具合に問題はないが、廃トナーを再利用しない装置に於いては、実施例２、３を応用した本実施例では、実行間隔を大幅に大きくした方が良いのは言うまでも無い。
【００９２】
このようにして、長期に渡ってムラなく均一で安定した感光ドラム１への帯電を行い、表面電位を維持することにより、長期に渡って鮮明でムラのない画像を得ることができる画像形成装置を提供することが出来るのである。
【００９３】
【発明の効果】
以上述べたように、本発明は、クリーナを有する、有しない、どちらの画像形成装置に於いても、まずは転写残現像剤や転写残外添剤の汚れが蓄積された帯電手段であるところの帯電ローラに現像剤を塗布し転写残現像剤や転写残外添剤の汚れを吸着させ、改めて帯電ローラから潜像担持体であるところの感光ドラムに現像剤を転写し、帯電ローラを清掃すると言うものである。これには、帯電用バイアス電源に正負の２極性を持たせる必要もなく、安価に実現可能である。
【００９４】
実施例２においては、個々の画像形成装置の使用環境における汚れ量の違いを踏まえた動作を可能にした画像形成装置を提供できる。
【００９５】
また、実施例３においては、ユーザが利用する転写材の種類の違いを踏まえた動作を可能にした画像形成装置を提供できる。
【００９６】
また、帯電ローラを清掃する本発明の実行間隔を、環境や転写材の種類のより細かく設定することにより、むやみに感光ドラムへダメージを与えることを避けることが可能な画像形成装置を提供できる。
【００９７】
それは、つまり、長期に渡ってムラなく均一で安定した感光ドラムへの帯電を行い、表面電位を維持することにより、長期に渡って鮮明でムラのない画像を得ることができる画像形成装置を提供することが出来るのである。
【図面の簡単な説明】
【図１】本発明の第１、２、３の実施例に係るクリーナレス画像形成装置の基本構成を示した側面断面図である。
【図２】一般的な画像形成装置の基本構成を示した側面断面図である。
【図３】本発明の一実施例に係る動作を、時制を追って簡略的に表した図である。
【図４】本発明の第４、第５の実施例に係る画像形成装置の側面断面図である。
【符号の説明】
１ 感光ドラム
２ 帯電ローラ
３ 帯電バイアス用電源
５ 現像装置
５ａ 現像スリーブ
５ｂ 現像マグネット
６ 現像バイアス用電源
７ 転写ローラ
８ 転写バイアス用電源
９ クリーナ
Ｔ トナー（現像剤）
Ｐ 転写材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is applicable to an image forming apparatus such as an electrophotographic apparatus, and relates to a charging member for charging an image carrier surface such as a photoreceptor and a charging device for charging the image carrier by bringing the charging member into contact with the image carrier surface. .
[0002]
[Prior art]
Conventionally, as a device for charging a surface of an image carrier as a member to be charged such as a photoreceptor or a dielectric in a copying machine such as an electrophotographic or electrostatic recording type image forming apparatus, a laser printer, a facsimile, etc. Conventionally, corona discharge devices have been widely used, but they require a high-voltage power supply and have problems such as generation of a large amount of ozone. However, since they are non-contact, they are still used in many high-speed image forming devices. Used.
[0003]
However, low-speed and medium-speed image forming apparatuses, which occupy a large part of the market, have the advantages that they can be used with a low-voltage power supply and that the amount of generated ozone is small, as an environment-friendly charging means. The contact charging system that is used is often used. In this method, a charging member to which a voltage is applied is brought into contact with the surface of the image bearing member to charge the surface of the image bearing member.
[0004]
FIG. 2 is a schematic view of an example of the contact-type charging device.
[0005]
Reference numeral 1 denotes an image carrier, which is a rotating drum type electrophotographic photosensitive member (photosensitive drum). Around the photosensitive drum 1, a primary charging device 2 for uniformly charging the surface of the photosensitive drum 1 in order along its rotation direction, and an exposure unit 4 for forming an electrostatic latent image on the photosensitive drum 1 according to image information. A developing device 5 for forming a toner image by attaching a developer (toner) to the electrostatic latent image; and a roller-type contact-charging transfer device for transferring the toner image on the photosensitive drum 1 to the transfer material P. 7, a cleaner 9 for removing the residual toner on the photosensitive drum 1 after the transfer of the toner image, and a static eliminator (lamp) 10 for initializing the surface of the photosensitive drum 1 are provided. Some inexpensive image forming apparatuses do not include the static eliminator (lamp) 10 or the like. In addition, a cleaner-less image forming apparatus that does not use a cleaner 9 that removes residual toner on the photosensitive drum 1 after transferring a toner image by increasing transfer efficiency is adopted for an image forming apparatus that has been recently proposed. Some are.
[0006]
The above-described photosensitive drum 1 is a drum-type electrophotographic photosensitive drum having a basic configuration layer of a conductive base layer 1b made of aluminum, iron, or the like, and a photoconductive layer 1a made of, for example, an organic photoconductor covering the outer peripheral surface thereof. And is driven to rotate at a predetermined peripheral speed in the direction of arrow R1 in FIG. Note that the conductive base layer 1b is grounded.
[0007]
Reference numeral 2 denotes a charging member, which is a roller type in this example (hereinafter referred to as a charging roller). The charging roller 2 includes a conductive roller 2c such as a metal roller serving as a metal core, a conductive layer 2b formed on the outer peripheral surface, and a resistance layer 2a formed on the outer peripheral surface. The charging roller 2 has both ends of a cored bar 2c rotatably supported by a bearing member (not shown), and is arranged in parallel with the drum type photosensitive drum 1, and is pressed against the surface of the photosensitive drum 1 by pressing means (not shown). The photosensitive drum 1 is pressed with a predetermined pressing force, and is rotated by the rotation of the photosensitive drum 1.
[0008]
Reference numeral 3 denotes a bias application power supply for the charging roller 2. The power supply 3 is electrically connected to the metal core 2 c of the charging roller 2, and a predetermined bias is applied to the charging roller 2 by the power supply 3. As this bias, there has been conventionally proposed a bias applied by applying a DC voltage or superimposing a DC voltage on an AC voltage. In particular, in the latter method, since the AC component equalizes the unevenness of the surface potential of the photosensitive member due to charging, and converges to a predetermined voltage by the DC component, it is easy to obtain the uniformity of the surface potential. At this time, it is known that when the superimposed AC voltage is low, the leveling effect obtained is small.
[0009]
In any case, when the photosensitive drum 1 as an image carrier is driven to rotate, the outer peripheral surface of the photosensitive member is fixed to a predetermined position by a charging roller 2 as a charging member which is pressed against the photosensitive drum 1 and to which a bias voltage is applied. Charged to polarity and potential.
[0010]
After charging, image exposure according to the image content is performed, and an electrostatic latent image is formed. The latent image is visualized with a developer, and further transferred and fixed on paper. After the transfer, the developer remaining after the transfer is cleaned by scraping off the developer remaining after the transfer with a cleaning blade, and is initialized by exposing and discharging to prepare for the next image formation.
[0011]
Next, an image forming process of the image forming apparatus having the above configuration will be briefly described. After the surface of the photosensitive drum 1 is uniformly charged by a contact charging type charging roller 2, the surface of the photosensitive drum 1 is exposed to scanning light corresponding to image information from an exposure unit 4 such as a laser scanner, a slit exposure unit, or the like. An image is formed. This electrostatic latent image is developed by the toner stored in the developing container 5b of the developing device 5 and carried on the surface of the developing sleeve 5a in a layered manner, and becomes a toner image. The toner image on the photosensitive drum 1 is transferred by the operation of the transfer device 7 onto the surface of the transfer material P supplied to the transfer nip N between the photosensitive drum 1 and the transfer device 7 by a paper feed mechanism (not shown). You. Thereafter, the transfer material P is separated from the surface of the photosensitive drum 1 and sent to an image fixing unit (not shown), and the transferred toner image is fixed as a permanently fixed image on the transfer material P, and is discharged out of the apparatus as a print or a copy. You. On the other hand, the photosensitive drum 1 continues to rotate as it is, and the adhered matter such as residual toner adhered to the surface is removed by the cleaner 9, and the charge is removed by the charge eliminator 10 to be initialized, thereby preparing for the next image forming process. .
[0012]
In the cleaner-less image forming apparatus, by increasing the transfer efficiency, the residual toner on the photosensitive drum 1 after the transfer of the toner image is almost eliminated, and a very small amount of transfer is performed without using the cleaner 9 for removing the transfer residual toner. The residual toner is collected in a developing container by applying a bias opposite to that during development by a developing device.
[0013]
[Problems to be solved by the invention]
However, in the image forming apparatus of the contact charging roller type shown in the above-mentioned conventional example, contamination such as toner or external additives that have passed through the cleaner 9 adheres to the charging roller 2 due to long-term use. There is a problem that unevenness occurs. In the case of a cleaner-less image forming apparatus, dirt adheres to the charging roller 2 in a shorter period of time as compared with an image forming apparatus having a cleaner.
[0014]
The cause is considered as follows.
[0015]
In the image forming apparatus, the transfer residual toner remaining on the photosensitive drum 1 without being transferred to the transfer material P in the transfer process is collected by the cleaner 9 or by the developing device 5 in the case of the cleanerless image forming apparatus.
[0016]
However, toner, which is a developer, is externally added with an external additive for the purpose of controlling the charge amount of the toner and preventing the toner from being fused to the surface of the photosensitive drum 1. Due to the small particle size, there are cases where the particles pass through without being completely removed by the cleaner 9. Further, the toner also has a particle diameter that is widened, and a toner having a small particle diameter. Similarly, the toner may pass through without being completely removed by the cleaner 9. In the cleanerless image forming apparatus, the transfer residual toner and the transfer residual external additive pass directly through the charging roller 2. In this way, dirt such as transfer residual toner and transfer residual external additive adheres to the charging roller 2.
[0017]
By repeating such a process, dirt such as untransferred toner and untransferred external additives is accumulated on the charging roller 2, so that the photosensitive drum 1 cannot be charged to a normal surface potential. This causes poor charging and uneven charging.
[0018]
Further, there is a difference in the charge amount of the toner depending on the environment in which the image forming apparatus is installed, so that a difference in the transfer efficiency appears. Therefore, the amount of the transfer residual toner, the transfer residual external additive, and the like differs depending on the environment. Further, since the transfer efficiency usually differs depending on the type of the transfer material P used, this also causes a difference in the amount of the transfer residual toner and the transfer residual external additive. That is, depending on the environment in which the image forming apparatus is installed and the type of the transfer material P used therein, there is a difference in the speed at which dirt such as transfer residual toner and transfer residual external additive accumulates on the charging roller 2. And the period until the occurrence of uneven charging or the like is different.
[0019]
Conventionally, for the contamination of the charging roller 2 such as a transfer residual toner and a transfer residual external additive, means for directly contacting a cleaning member with the charging roller 2 and cleaning or collecting the same has been considered. In such a case, it has been impossible to clean the charging roller 2 for a long period of time due to a decrease in the cleaning member's cleaning or collecting ability. Periodically, it is possible to extend the period until the performance is reduced. However, even then, there is a problem that eventually the capacity may be insufficient and dirt may accumulate on the charging roller 2. Further, since the charging roller 2 is brought into contact with the charging roller 2, there is a problem that eventually the surface of the charging roller 2 itself is roughened to cause an image defect.
[0020]
Therefore, by applying a bias having a polarity opposite to that during normal image formation to the charging roller 2, the transfer residual external additive which tends to be charged to the polarity opposite to that of the toner and the normal transfer residual toner among the transfer residual toner A so-called reverse toner charged to the opposite polarity and attracted to the charging roller 2 is transferred to the photosensitive drum 1 and a charging roller cleaning unit for cleaning the charging roller 2 has been proposed and implemented. There remains a problem that minute dirt attached to the charging roller 2 cannot be completely cleaned. In addition, a power supply for applying a charging bias having a polarity opposite to that of a normal case tends to be expensive.
[0021]
(Object of the present invention)
Therefore, an object of the invention according to the present application has been made in view of the above-mentioned circumstances, and a contact charging system that charges a surface of a photosensitive drum to a predetermined potential by applying a bias to a charging roller that rotates in contact with the photosensitive drum. Means for removing dirt such as transfer residual toner and transfer residual additive accumulated on the charging roller, which is a charging member, and periodically or every different period depending on the environment in which the apparatus is installed and the type of transfer material. In addition, the removal prevents contamination such as residual toner and external additives from accumulating on the charging member, and uniformly and stably charges the photosensitive drum over a long period of time to maintain the surface potential. Accordingly, it is an object of the present invention to provide an image forming apparatus capable of obtaining a clear and uniform image for a long time.
[0022]
[Means for Solving the Problems]
The above object is achieved by an image forming apparatus having the following configuration according to the present invention.
[0023]
According to the first invention of the present application, the above object is achieved by supplying a bias from a power source to a latent image carrier and a roller-shaped charging member that rotates while being in contact with the image carrier. Charging means, charging means, image exposure means for exposing an image on the image bearing member to form an image, developing means for visualizing the image by applying a bias and a developer, and Transfer means for transferring the visualized developer image onto a transfer material, and after transferring the developer image onto the transfer material by the transfer means, cleaning the transfer residual developer on the image bearing member. In an image forming apparatus having no cleaning means for collecting and collecting
At any time other than the time of image formation, the developing unit applies the developer over the entire image area and the outer circumference of the roller-shaped charging member for at least one round of the image carrier, and further rotates the image carrier by rotating the image carrier. A developer is applied on the outer peripheral surface of the member, and thereafter, a bias is applied to the charging member, so that the transfer residual developer on the charging member, dirt due to an external additive, etc. and the developer are simultaneously coated on the image carrier. And a bias is applied to the developing unit so that the relationship between the potential of the image carrier and the developing unit is opposite to that during image formation, and the dirt and developer on the charging member are collected by the developing unit. This can be achieved by doing so.
[0024]
According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the image forming device is provided with an image area on the image carrier by the developing unit at any time other than the time of image formation. When applying the developer over the entire surface and one round or more around the outer circumference of the roller-shaped charging member, the surface potential on the image carrier is charged to a potential at which the developing material is developed by the roller-shaped charging member before that. Or a state in which an image is formed, the roller is charged by the roller-shaped charging member and the image is exposed to a black image by the image exposing means, and a bias for visualizing the image with a developer is applied to the developing means. Can be achieved.
[0025]
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the object is that the transfer unit uses a bias, and any other than a time of image formation is used. At the time, the developing means applies the developer on the entire surface of the image carrier and the outer circumference of the roller-shaped charging member for at least one round, and further rotates the image carrier on the outer peripheral surface of the roller-shaped charging member. When the developer is applied to the image forming apparatus, the bias polarity of the transfer unit may be set to a polarity opposite to that during image formation.
[0026]
According to the fourth invention of the present application, the above object is achieved by the image forming apparatus according to any one of the first to third inventions, wherein the developing unit performs the image forming at any time other than at the time of image formation. When applying the developer over the entire image area and one circumference of the outer circumference of the roller-shaped charging member on the image carrier, and further applying the developer on the outer circumference of the roller-shaped charging member by rotation of the image carrier, This can be achieved by setting the bias applied to the roller-shaped charging member to a bias having a polarity opposite to that of the developer.
[0027]
According to a fifth aspect of the present invention, the above object is achieved by the image forming apparatus according to any one of the first to fourth aspects, wherein the developing unit performs the image forming at any time other than the time of image formation. Applying the developer over the entire image area and one circumference of the outer circumference of the roller-shaped charging member to the image carrier, further applying the developer on the outer circumference of the charging member by rotation of the image carrier, and thereafter, It can also be achieved that the bias applied to the roller-shaped charging member when the stain on the roller-shaped charging member and the developer are simultaneously transferred onto the image carrier is a bias having the same polarity as the developer.
[0028]
According to a sixth aspect of the present invention, the above object is achieved by any one of the first to fifth aspects having a humidity detecting means for detecting a humidity of an environment in which the image forming apparatus is installed. In the image forming apparatus, the collection of the dirt due to the transfer residual developer or the external additive on the charging member to the developing unit at any time other than the time of image formation is performed at an arbitrary interval, and the interval is determined by detecting the humidity. This can be achieved by changing according to the value of the humidity detected by the means.
[0029]
According to a seventh aspect of the present invention, the above object is achieved by any one of the first to sixth aspects in which a user can set a type of a transfer material used in the image forming apparatus. In the image forming apparatus, the collection of dirt by the transfer residual developer or the external additive on the charging member to the developing unit at any time other than the time of image formation is performed at an arbitrary interval. Can be achieved by changing the type of transfer material set.
[0030]
According to an eighth aspect of the present invention, the above object is achieved by supplying a bias from a power source to a latent image carrier and a roller-shaped charging member that rotates while being in contact with the image carrier. Charging means, charging means, image exposure means for exposing an image on the image bearing member to form an image, developing means for visualizing the image by applying a bias and a developer, and A transfer unit for transferring the visualized developer image onto a transfer material, and after transferring the developer image onto the transfer material by the transfer unit, cleaning and collecting the untransferred developer on the image bearing member. An image forming apparatus comprising: a cleaning unit;
At any time other than the time of image formation, the developing unit applies the developer over the entire image area and the outer circumference of the roller-shaped charging member for at least one round of the image carrier, and further rotates the image carrier by rotating the image carrier. A developer is applied on the outer peripheral surface of the member, and thereafter, a bias is applied to the charging member, so that the transfer residual developer on the charging member, dirt due to an external additive, etc. and the developer are simultaneously coated on the image carrier. And a bias is applied to the developing unit so that the relationship between the potential of the image carrier and the developing unit is opposite to that during image formation, and the dirt and developer on the charging member are collected by the developing unit. This can be achieved by doing so.
[0031]
According to a ninth aspect of the present invention, the above object is achieved in the image forming apparatus according to the eighth aspect, wherein the image forming device is provided with an image area on the image carrier by the developing unit at any time other than the time of image formation. When applying the developer over the entire surface and one round or more around the outer circumference of the roller-shaped charging member, the surface potential on the image carrier is charged to a potential at which the developing material is developed by the roller-shaped charging member before that. Or a state in which an image is formed, the roller is charged by the roller-shaped charging member and the image is exposed to a black image by the image exposing means, and a bias for visualizing the image with a developer is applied to the developing means. Can be achieved.
[0032]
According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth or ninth aspect, the transfer means uses a bias, and the transfer means uses a bias other than at the time of image formation. At the time, the developing means applies the developer on the entire surface of the image carrier and the outer circumference of the roller-shaped charging member for at least one round, and further rotates the image carrier on the outer peripheral surface of the roller-shaped charging member. When the developer is applied to the image forming apparatus, the bias polarity of the transfer unit may be set to a polarity opposite to that during image formation.
[0033]
According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the eighth to tenth aspects, at any time other than at the time of image formation, the developing means When applying the developer over the entire image area and one circumference of the outer circumference of the roller-shaped charging member on the image carrier, and further applying the developer on the outer circumference of the roller-shaped charging member by rotation of the image carrier, This can be achieved by setting the bias applied to the roller-shaped charging member to a bias having a polarity opposite to that of the developer.
[0034]
According to a twelfth aspect of the present invention, the above object is achieved by the image forming apparatus according to any one of the eighth to eleventh aspects, wherein the developing unit executes Applying the developer over the entire image area and one circumference of the outer circumference of the roller-shaped charging member to the image carrier, further applying the developer on the outer circumference of the charging member by rotation of the image carrier, and thereafter, It can also be achieved that the bias applied to the roller-shaped charging member when the stain on the roller-shaped charging member and the developer are simultaneously transferred onto the image carrier is a bias having the same polarity as the developer.
[0035]
According to a thirteenth aspect of the present invention, the above object is attained by any one of the eighth to twelfth aspects having a humidity detecting means for detecting the humidity of the environment where the image forming apparatus is installed. In the image forming apparatus, the collection of the dirt due to the transfer residual developer or the external additive on the charging member to the developing unit at any time other than the time of image formation is performed at an arbitrary interval, and the interval is determined by detecting the humidity. This can be achieved by changing according to the value of the humidity detected by the means.
[0036]
According to a fourteenth aspect of the present invention, the above object is achieved by any one of the eighth to thirteenth aspects, wherein a user can set the type of transfer material used in the image forming apparatus. In the image forming apparatus, the collection of dirt by the transfer residual developer or the external additive on the charging member to the developing unit at any time other than the time of image formation is performed at an arbitrary interval. Can be achieved by changing the type of transfer material set.
[0037]
According to a fifteenth aspect of the present invention, the above object is achieved in the image forming apparatus according to any one of the eighth to fourteenth aspects, by transferring the visualized developer image onto the image bearing member. In the image forming apparatus having a cleaning unit for transferring and transferring the developer remaining on the image bearing member in contact with the image bearing member after transferring onto the transfer material by means,
At any time other than the time of image formation, the developing means applies the developer over the entire image area and at least one round of the outer circumference of the roller-shaped charging member to the image carrier, and further rotates the roller by rotating the image carrier. Applying a developer on the outer peripheral surface of the roller-shaped charging member, and then transferring a stain and the developer on the roller-shaped charging member onto the image carrier at the same time by applying a bias to the roller-shaped charging member, A bias is applied to the developing unit so that the potential relationship between the image carrier and the developing unit is opposite to that at the time of image formation, until the dirt and the developer on the roller-shaped charging member are collected by the developing unit. During this time, the cleaning means can be achieved by separating the cleaning means from the image bearing member.
[0038]
According to a sixteenth aspect of the present invention, the above object is achieved in the image forming apparatus according to any one of the eighth to fourteenth aspects, wherein the visualized developer image is transferred onto the image bearing member. In the image forming apparatus having a cleaning unit for transferring and transferring the developer remaining on the image bearing member in contact with the image bearing member after transferring onto the transfer material by means,
At any time other than the time of image formation, the developing unit applies a developer over the entire image area of the image carrier and one or more turns of the outer periphery of the roller-shaped charging member, and the applied developer is applied to the cleaning unit. While passing through the corresponding position, the cleaning means is separated from the image bearing member to allow the developer to pass therethrough and apply the developer on the outer peripheral surface of the roller-shaped charging member. By applying a bias to the member, the dirt and the developer on the roller-shaped charging member are simultaneously transferred onto the image carrier, and finally the dirt and the developer on the roller-shaped charging member are collected by the cleaning unit. This can be achieved.
[0039]
According to a seventeenth aspect of the present invention, the above object is achieved by supplying a bias from a power source to an image carrier and a roller-shaped charging member that rotates while contacting the image carrier. Charging means for charging the upper portion; image exposure means for forming an image by exposing the image bearing member to an image; developing means for visualizing the image by applying a bias and a developer; And a transfer unit for transferring the visualized developer image onto a transfer material, wherein the method for cleaning a roller-shaped charging member of the contact charging system according to any one of the first to sixteenth aspects is used. Can be achieved.
[0040]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to examples.
[0041]
(First embodiment)
An embodiment of the present invention will be described below with reference to FIGS.
[0042]
FIG. 1 is a schematic diagram of an image forming apparatus according to one embodiment. The image forming apparatus of the present embodiment is a transfer type laser beam printer or copier utilizing an electrophotographic process.
[0043]
Reference numeral 1 denotes a drum-type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an electrostatic latent image carrier, which is rotationally driven at a predetermined process speed in a clockwise direction indicated by an arrow m. The photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by the charging roller 2 during the rotation process. In this example, the photosensitive drum 1 is charged negatively.
[0044]
The charging roller 2 of the present embodiment is a contact charging roller, and rotates following the rotation of the photosensitive drum 1.
[0045]
Then, by applying a bias voltage obtained by superimposing a predetermined DC voltage on a predetermined AC voltage from the power supply 3, the peripheral surface of the rotary photosensitive drum 1 is charged to a predetermined polarity and potential by a contact charging method.
[0046]
Next, the charged surface is subjected to image exposure processing of the target image information by the image exposure means 4 such as a laser scanner, so that an electrostatic latent image of the target image information is formed on the surface of the photosensitive drum 1.
[0047]
The electrostatic latent image is developed by the toner T carried in a thin layer on the developing sleeve 5a of the developing device 5 to become a visible image (toner image). The developing sleeve 5a is controlled by a clutch (not shown) and rotates in an image area. The toner T is supplied to the photosensitive drum 1 by applying a predetermined bias voltage (AC voltage is superimposed on DC voltage; hereinafter, referred to as a developing bias) from the power supply 6.
[0048]
In the present embodiment, reversal development is performed using negatively charged toner T (negative toner).
[0049]
In the transfer section, which is a contact nip portion between the photosensitive drum 1 and the transfer member 7 brought into contact with the photosensitive drum 1, the transfer material P fed to the transfer section at a predetermined timing from the paper supply section side. Are sequentially transferred.
[0050]
The transfer member 7 in this embodiment is a contact charging transfer roller, which is pressed against the photosensitive drum 1 and rotates following the rotation of the photosensitive drum 1.
[0051]
The transfer material P is fed to the transfer section. When the leading end of the transfer material P enters the transfer portion, a predetermined transfer bias is applied to the transfer roller 7 from the power supply 8, and the back surface of the transfer material P with which the transfer roller 7 is in contact has a polarity opposite to that of the toner T. The toner image on the photosensitive drum 1 is transferred to the surface of the transfer material P by being charged by a charging method.
[0052]
The transfer material P to which the toner image has been transferred through the transfer unit is separated from the surface of the photosensitive drum 1 and sent to an image fixing unit (not shown), and the transferred toner image is fixed on the transfer material P as a permanently fixed image. Then, the prints or copies are discharged outside the machine.
[0053]
Since the cartridge type in which the photosensitive drum 1, the charging roller 2, and the developing device 5 are integrated is used up and has a comparatively short life, when the transfer efficiency is considerably improved, the contamination of the charging roller 2 may be reduced on the image. Since the cartridge exchange is completed before the above-mentioned situation occurs, a series of image formation is completed as described above, and thereafter, the image is initialized again by the charging roller 2 and repeatedly used for image formation.
[0054]
On the other hand, in an apparatus in which the charging roller 2 is used for a long period of time, even if the transfer residual toner (developer) and the transfer residual external additive are extremely small, image defects and charging unevenness occur due to accumulation. Therefore, even if the transfer efficiency is improved and improved, a recovery means for the transfer residual toner and the transfer residual external additive is used. It is, for example, as follows.
[0055]
Even after a series of image formation is completed, the charging process by the charging roller 2 is continued, and by applying a bias to the developing sleeve 5a of the developing device 5 with a polarity opposite to that of the image forming (developing), the transfer residual toner is And the transfer residual additive is attracted to the developing sleeve 5a side and collected. Thereafter, the image is repeatedly provided for image formation.
[0056]
The charging roller 2 and the transfer roller 7 of the contact charging type may be provided with gears and the like, and may be forcibly driven by driving means such as a motor.
[0057]
However, in the above-described image forming apparatus, the above-described problem may occur depending on circumstances, and there is room for improvement.
[0058]
Therefore, the problem solving means in the present embodiment is to first apply toner to the charging roller 2 in which dirt of the transfer residual toner and the transfer residual external additive is accumulated, and to adsorb the dirt of the transfer residual toner and the transfer residual external additive, The toner T is transferred from the charging roller 2 to the photosensitive drum 1 again, and is collected by the developing device 5. In the case where the transfer residual toner and the transfer residual external additive are adsorbed to the toner and are removed from the charging roller 2, even a particle having a small particle diameter is adsorbed to the toner. The cleaning performance of the charging roller is much higher than that of the application. Further, when the toner on which the dirt on the charging roller 2 is adsorbed is transferred to the drum, a charging bias having the same polarity as that during image formation may be used.
[0059]
As described above, in this embodiment, an example in which reversal development is performed using negatively charged toner T (negative toner) will be described. Hereinafter, the details will be described with reference to FIG. 3 according to the example.
[0060]
First, FIG. 3A shows a state before the problem solving means is executed. Then, at an arbitrary time other than the time of image formation, the photosensitive drum 1 is driven and rotated, and a negative bias of a predetermined value is applied to the developing sleeve 5a, which is a developing unit, as in the case of image formation. Thereby, the toner T is applied (developed) on the photosensitive drum 1 as shown in FIG. The application area is equal to or larger than the entire image area and one circumference of the outer circumference of the charging roller 2. Thereafter, the toner is conveyed to the transfer roller position, which is the transfer member 7. At this time, unlike during image formation, a bias having a polarity opposite to that for image transfer is applied, as shown in FIG. Through the toner T. Further, the rotation of the photosensitive drum 1 causes the toner T to be carried to a position where the photosensitive drum 1 and the charging roller 2 are in pressure contact with each other. The toner T is applied on the outer peripheral surface of the roller 2.
[0061]
However, not all of the toner T applied on the photosensitive drum 1 is transferred to the charging roller 2. Therefore, the portion of the toner T applied on the photosensitive drum 1 on the photosensitive drum 1 first is changed to the developing sleeve 5a. When the DC component is applied with a positive bias to the developing sleeve 5a at the point of time when the opposite position is reached, the potential relationship between the photosensitive drum 1 and the developing sleeve 5a becomes opposite to that during image formation, and the toner T becomes As shown in FIG. 3F, the developer is drawn onto the developing sleeve 5a and starts to be collected.
[0062]
After the toner T has been applied to the outer circumference of the charging roller 2 for one week or more, a bias having the same polarity as the negatively charged toner T is applied to the charging roller 2 so that the transfer residual toner on the charging roller 2 is And the toner T adsorbed by the toner and external additives are transferred onto the photosensitive drum 1 at the same time. This is also the state shown in FIG. Since the example given here is reversal development using negative toner, a negative bias having the same polarity as that of the toner T is applied to the charging roller 2 even during normal image formation. Bias is good. At this time, the transfer residual toner and the toner T adsorbing the dirt such as the external additive transferred onto the photosensitive drum 1 are negatively charged together with the photosensitive drum 1 by the bias for the transfer.
[0063]
Next, as the photosensitive drum 1 rotates, the toner T that has adsorbed dirt such as transfer residual toner and external additives is carried to a position facing the developing sleeve 5a. Even at that time, a positive bias having a DC component is applied to the developing sleeve 5a, and the potential relationship between the photosensitive drum 1 and the developing sleeve 5a is opposite to that during image formation. The toner T that has absorbed the remaining transfer residual toner and the stains such as the external additives is attracted to the developing sleeve 5a and collected as shown in FIG. At this time, since the photosensitive drum 1 is negatively charged, the potential of the developing sleeve 5a may be grounded (0 V). At this time, if an AC bias is applied in the same manner as during normal image formation, the toner T goes back and forth between the photosensitive drum 1 and the developing sleeve 5a, so that the toner T sticks on the photosensitive drum 1 persistently. The discharged toner T is also beaten out, and the toner T can be collected more reliably and efficiently. In this way, as shown in FIG. 3H, the transfer residual toner on the charging roller 2 and the dirt due to the external additive and the toner T adsorbing the dirt are collected by the developing device 5.
[0064]
In the present embodiment, when the contamination due to the transfer residual toner or the external additive on the charging roller 2 and the toner T adsorbing the same are collected in the developing device 5, a DC component positive bias is applied to the developing sleeve 5a. However, for that purpose, the developing bias power source 6 must have both positive and negative outputs. Therefore, at the time of FIGS. 3 (e) and 3 (f), the transfer residual toner T to the charging roller 2 is passed through as it is without applying the developing bias, and the photosensitive drum 1 is rotated once, and then the developing sleeve 5a is Can also be collected. This is because the photosensitive drum 1 is negatively charged from the time when the transfer residual toner on the charging roller 2, the dirt due to the external additive, and the like and the toner T adsorbed thereon are simultaneously transferred to the photosensitive drum 1, This is because even when the potential of the developing sleeve 5a is grounded (0 V), the potential relationship is opposite to that at the time of image formation, so that the developing sleeve 5a is attracted onto the developing sleeve 5a and collected. By doing so, the developing bias power supply 6 can be inexpensive.
[0065]
That is, by periodically removing dirt such as transfer residual toner and transfer residual additive accumulated on the charging roller 2 which is a charging member as described above, transfer residual toner and transfer residual external additive are removed. To prevent the accumulation of dirt on the charging member, uniformly and stably charge the photosensitive drum 1 for a long period of time, and maintain a surface potential, so that a clear and uniform image can be formed for a long period of time. An image forming apparatus that can be obtained can be provided.
[0066]
(Second embodiment)
Next, a second embodiment of the present invention will be described.
[0067]
The basic configuration is the same as in the first embodiment, FIGS. 1 and 3. In the present embodiment, the image forming apparatus is provided with a humidity detecting unit that detects the atmospheric humidity at the place where the image forming apparatus is installed at the start of each image formation, and can average the number of measurement times of the humidity. The execution interval of the cleaning of the contact charging type roller-shaped charging member of the first embodiment is changed according to the humidity.
[0068]
Table 1 shows the transfer efficiency under various environments. As is clear from the table, in the image forming apparatus used in the experiment, the higher the environmental humidity, the lower the transfer efficiency.
[0069]
[Table 1]

[0070]
Therefore, if the average humidity during the last ten image formations is less than 50%, the execution interval of the contact charging type roller-shaped charging member cleaning of Example 1 is performed every ten image formations, and the average humidity is 50%. In the above case, it is set so that the image formation is performed every five times. An example is shown in Table 2.
[0071]
[Table 2]

[0072]
That is, by changing the execution interval for removing dirt such as transfer residual toner and transfer residual additive accumulated on the charging roller 2 which is a charging member as described above, depending on the environmental humidity, an environment having low transfer efficiency can be obtained. In the lower part, the accumulation of dirt such as transfer residual toner and transfer residual external additive on the charging roller 2 is prevented at an early stage, and in an environment with high transfer efficiency, damage to the photosensitive drum 1 is slightly reduced. But it can be suppressed. The reason is that the photosensitive drum 1 is damaged by the bias application by the charging roller 2 and the transfer member 7 although it is minute.
[0073]
In this way, the photosensitive drum 1 is charged uniformly and stably without unevenness over a long period of time, and by maintaining the surface potential, an image forming apparatus capable of obtaining a clear and uniform image over a long period of time. Can be provided.
[0074]
(Third embodiment)
Next, a third embodiment of the present invention will be described.
[0075]
The basic configuration is the same as in the first embodiment, FIGS. 1 and 3. In the present embodiment, the execution interval of the cleaning of the contact charging type roller-shaped charging member of the first embodiment is changed depending on the type of the transfer material used for image formation.
[0076]
Further, a transfer material to be used is set by the user.
[0077]
Table 2 shows the transfer efficiencies of various transfer materials. In the image forming apparatus used in this experiment, the transfer efficiency was reduced on rough paper, thick paper (including postcards), and OHT paper.
[0078]
Therefore, when the user selects paper having a rough surface, thick paper (including postcards), or OHT paper, the execution interval of the roller-type charging member cleaning of the contact charging system of the first embodiment is performed for each image formation. When the transfer material is used, it is set so that the transfer is performed every 50 times of image formation.
[0079]
That is, the transfer interval is changed depending on the type of the transfer material used to remove the stain such as the transfer residual toner and the transfer residual external additive accumulated on the charging roller 2 which is the charging member as described above. Even if a transfer material having a low efficiency is used, it is possible to prevent the accumulation of dirt such as a transfer residual toner and a transfer residual external additive on the charging roller 2 at an early stage. Thus, the damage to the body drum 1 can be suppressed even a little. The reason is that the photosensitive drum 1 is damaged by the bias application by the charging roller 2 and the transfer member 7 although it is minute.
[0080]
In this way, the photosensitive drum 1 is charged uniformly and stably without unevenness over a long period of time, and by maintaining the surface potential, an image forming apparatus capable of obtaining a clear and uniform image over a long period of time. Can be provided.
[0081]
(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described.
[0082]
The basic configuration is the same as that of the first embodiment, FIGS. 1 and 3, but there is a difference as to whether or not the cleaner 9 is provided, and the embodiment is shown in FIG. In this embodiment, there is a cleaner 9.
[0083]
The same applies to the image forming operation until the toner image on the photosensitive drum 1 is transferred to the surface of the transfer material P. Further, the toner image is separated from the surface of the photosensitive drum 1 and sent to an image fixing unit (not shown), and the transferred toner image is fixed as a permanently fixed image on the transfer material P, and is discharged outside the machine as a print or a copy. It is.
[0084]
However, the surface of the photosensitive drum 1 after passing through the transfer section is cleaned by removing the residual developer and other deposits by the cleaner 9, and further, is discharged and initialized by the discharger (discharge lamp) 10. In the image forming apparatus used for image formation, the above-mentioned problem may occur depending on the situation, and there is room for improvement.
[0085]
Therefore, in the present embodiment, as in the first to third embodiments, first, toner is applied to the charging roller 2 in which dirt of the transfer residual toner and the transfer residual external additive is accumulated, and the transfer residual toner and the transfer residual toner are removed. The dirt of the external additive is adsorbed, the toner T is transferred from the charging roller 2 to the photosensitive drum 1 again, and is collected in the developing device 5. The toner cannot be applied to the charging roller 2. Therefore, in the present embodiment, the cleaner 9 is present in the image forming apparatuses of the first to third embodiments, and during the same cleaning of the roller charging member of the contact charging system, the cleaner 9 is removed. This is realized by keeping the photosensitive drum 1 away from the photosensitive drum 1.
[0086]
In this way, the photosensitive drum 1 is charged uniformly and stably without unevenness over a long period of time, and by maintaining the surface potential, an image forming apparatus capable of obtaining a clear and uniform image over a long period of time. Can be provided.
[0087]
(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described.
[0088]
The basic configuration is the same as that of the fourth embodiment, and is an image forming apparatus having a cleaner 9 as shown in FIG.
[0089]
The difference is that the transfer residual toner on the charging roller 2 and the toner T adsorbed with dirt such as external additives are finally collected on the cleaner 9 instead of being attracted and collected on the developing sleeve 5a. That is.
[0090]
To this end, the state in which the cleaner 9 is kept away from the photosensitive drum 1 in the fourth embodiment is that the toner for absorbing dirt of the transfer residual toner and the transfer residual external additive is applied to the photosensitive drum 1 (development). However, the operation must be performed only while the area on the photosensitive drum 1 passes the position facing the cleaner 9.
[0091]
However, since the toner is collected by the cleaner 9, when the waste toner is reused, there is no problem in the degree of reduction of the toner, but in an apparatus in which the waste toner is not reused, the second and third embodiments are used. It is needless to say that it is better to greatly increase the execution interval in the present embodiment to which is applied.
[0092]
In this way, the photosensitive drum 1 is charged uniformly and stably without unevenness over a long period of time, and by maintaining the surface potential, an image forming apparatus capable of obtaining a clear and uniform image over a long period of time. Can be provided.
[0093]
【The invention's effect】
As described above, the present invention, in either image forming apparatus having or not having a cleaner, is a charging means in which dirt of a transfer residual developer or a transfer residual additive is accumulated first. When the developer is applied to the charging roller to absorb the transfer residual developer and transfer residual external additives, the developer is transferred from the charging roller to the photosensitive drum, which is a latent image carrier, and the charging roller is cleaned. That's what it says. This does not require the charging bias power supply to have two positive and negative polarities, and can be realized at low cost.
[0094]
In the second embodiment, it is possible to provide an image forming apparatus capable of performing an operation based on a difference in the amount of dirt in a usage environment of each image forming apparatus.
[0095]
Further, in the third embodiment, it is possible to provide an image forming apparatus capable of performing an operation based on a difference in the type of transfer material used by a user.
[0096]
Further, by setting the execution interval of the present invention for cleaning the charging roller to be finer depending on the environment and the type of the transfer material, it is possible to provide an image forming apparatus capable of avoiding unnecessarily damaging the photosensitive drum.
[0097]
In other words, an image forming apparatus that can uniformly and stably charge the photosensitive drum without unevenness over a long period of time and maintain a surface potential to provide a clear and uniform image over a long period of time is provided. You can do it.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing a basic configuration of a cleanerless image forming apparatus according to first, second and third embodiments of the present invention.
FIG. 2 is a side sectional view illustrating a basic configuration of a general image forming apparatus.
FIG. 3 is a diagram schematically illustrating an operation according to an embodiment of the present invention, following a tense.
FIG. 4 is a side sectional view of an image forming apparatus according to fourth and fifth embodiments of the present invention.
[Explanation of symbols]
1 Photosensitive drum
2 Charging roller
3 Power supply for charging bias
5 Developing device
5a Developing sleeve
5b Developing magnet
6 Power supply for developing bias
7 Transfer roller
8 Power supply for transfer bias
9 Cleaner
T toner (developer)
P transfer material

Claims (17)

A latent image carrier, charging means for charging the image carrier by supplying a bias from a power source to a roller-shaped charging member which rotates in contact with the image carrier, and Image exposure means for forming an image by image exposure, developing means for visualizing the image by applying a bias and a developer, and transfer means for transferring the developer image visualized on the image bearing member onto a transfer material An image forming apparatus having no cleaning means for cleaning and collecting a transfer residual developer on the image bearing member after transferring the developer image onto a transfer material by the transfer means.
At any time other than the time of image formation, the developing unit applies the developer over the entire image area and the outer circumference of the roller-shaped charging member for at least one round of the image carrier, and further rotates the image carrier by rotating the image carrier. A developer is applied on the outer peripheral surface of the member, and thereafter, a bias is applied to the charging member, so that the transfer residual developer on the charging member, dirt due to an external additive, etc. and the developer are simultaneously coated on the image carrier. And a bias is applied to the developing unit so that the relationship between the potential of the image carrier and the developing unit is opposite to that during image formation, and the dirt and developer on the charging member are collected by the developing unit. An image forming apparatus, comprising: At any time other than the time of image formation, when the developing unit applies the developer over the entire image area and the outer circumference of the roller-shaped charging member for one or more rounds on the image carrier, the developer may be applied on the image carrier before that. Is charged by the roller-shaped charging member in a state where the developing material is charged by the roller-shaped charging member to a potential at which the developing material is developed, or a black image is exposed by the image exposing means in a state at the time of image formation. 2. The image forming apparatus according to claim 1, wherein a bias for visualizing the image with a developer is applied to the developing unit. The transfer unit uses a bias, and at any time other than the time of image formation, the developing unit applies the developer over the entire image area and at least one circumference of the outer circumference of the roller-shaped charging member to the image carrier. 2. The image forming apparatus according to claim 1, wherein when the developer is applied on the outer peripheral surface of the roller-shaped charging member by rotation of the image carrier, the bias polarity of the transfer unit is opposite to that during image formation. Or the image forming apparatus according to claim 2. At any time other than the time of image formation, the developing means applies the developer over the entire image area and at least one round of the outer circumference of the roller-shaped charging member to the image carrier, and further rotates the roller by rotating the image carrier. The bias applied to the roller-shaped charging member when applying a developer on the outer peripheral surface of the roller-shaped charging member is a bias having a polarity opposite to that of the developer. The image forming apparatus as described in the above. At any time other than the time of image formation, the developing unit applies the developer over the entire image area and the outer circumference of the roller-shaped charging member for at least one round of the image carrier, and further rotates the image carrier by rotating the image carrier. A bias is applied to the roller-shaped charging member when the developer is applied to the outer peripheral surface of the member, and then, when the dirt on the roller-shaped charging member and the developer are simultaneously transferred onto the image carrier, the bias applied to the roller-shaped charging member is The image forming apparatus according to claim 1, wherein the bias has the same polarity as that of the image forming apparatus. 6. The image forming apparatus according to claim 1, further comprising a humidity detecting unit configured to detect a humidity of an environment in which the image forming apparatus is installed. The image forming apparatus is characterized in that the collection of dirt by the transfer residual developer or the external additive to the developing means is at an arbitrary interval, and the interval is changed according to the value of the humidity detected by the humidity detecting means. . 7. The image forming apparatus according to claim 1, wherein a type of a transfer material used in the image forming apparatus can be set by a user. The image forming apparatus is characterized in that the collection of dirt by the transfer residual developer or the external additive to the developing means is at an arbitrary interval, and the interval is changed according to the type of the transfer material set by the user. A latent image carrier, charging means for charging the image carrier by supplying a bias from a power source to a roller-shaped charging member which rotates in contact with the image carrier, and Image exposure means for forming an image by image exposure, developing means for visualizing the image by applying a bias and a developer, and transfer means for transferring the developer image visualized on the image bearing member onto a transfer material An image forming apparatus comprising: a cleaning unit that cleans and collects a transfer residual developer on the image bearing member after transferring the developer image onto a transfer material by the transfer unit.
At any time other than the time of image formation, the developing unit applies the developer over the entire image area and the outer circumference of the roller-shaped charging member for at least one round of the image carrier, and further rotates the image carrier by rotating the image carrier. A developer is applied on the outer peripheral surface of the member, and thereafter, a bias is applied to the charging member, so that the transfer residual developer on the charging member, dirt due to an external additive, etc. and the developer are simultaneously coated on the image carrier. And a bias is applied to the developing unit so that the relationship between the potential of the image carrier and the developing unit is opposite to that during image formation, and the dirt and developer on the charging member are collected by the developing unit. An image forming apparatus, comprising: At any time other than the time of image formation, when the developing unit applies the developer over the entire image area and the outer circumference of the roller-shaped charging member for one or more rounds on the image carrier, the developer may be applied on the image carrier before that. Is charged by the roller-shaped charging member in a state where the developing material is charged by the roller-shaped charging member to a potential at which the developing material is developed, or a black image is exposed by the image exposing means in a state at the time of image formation. 9. An image forming apparatus according to claim 8, wherein a bias for visualizing said image with a developer is applied to said developing means. The transfer unit uses a bias, and at any time other than the time of image formation, the developing unit applies the developer over the entire image area and at least one circumference of the outer circumference of the roller-shaped charging member to the image carrier. 9. The method according to claim 8, wherein when the developer is applied on the outer peripheral surface of the roller-shaped charging member by rotating the image carrier, the bias polarity of the transfer unit is reverse to that during image formation. An image forming apparatus according to claim 9. At any time other than the time of image formation, the developing means applies the developer over the entire image area and at least one round of the outer circumference of the roller-shaped charging member to the image carrier, and further rotates the roller by rotating the image carrier. The bias applied to the roller-shaped charging member when applying the developer on the outer peripheral surface of the roller-shaped charging member is a bias having a polarity opposite to that of the developer. The image forming apparatus as described in the above. At any time other than the time of image formation, the developing unit applies the developer over the entire image area and the outer circumference of the roller-shaped charging member for at least one round of the image carrier, and further rotates the image carrier by rotating the image carrier. A bias is applied to the roller-shaped charging member when the developer is applied to the outer peripheral surface of the member, and then, when the dirt on the roller-shaped charging member and the developer are simultaneously transferred onto the image carrier, the bias applied to the roller-shaped charging member is The image forming apparatus according to claim 8, wherein the bias has the same polarity as that of the image forming apparatus. 13. The image forming apparatus according to claim 8, further comprising a humidity detecting unit configured to detect a humidity of an environment in which the image forming apparatus is installed. The image forming apparatus is characterized in that the collection of dirt by the transfer residual developer or the external additive to the developing means is at an arbitrary interval, and the interval is changed according to the value of the humidity detected by the humidity detecting means. . 14. The image forming apparatus according to claim 1, wherein the type of the transfer material used in the image forming apparatus can be set by a user. The image forming apparatus is characterized in that the collection of dirt by the transfer residual developer or the external additive to the developing means is at an arbitrary interval, and the interval is changed according to the type of the transfer material set by the user. Cleaning means for transferring the developer image visualized on the image bearing member onto a transfer material by a transfer means, and for cleaning and collecting the transfer residual developer on the image bearing member in contact with the image bearing member In the image forming apparatus having
At any time other than the time of image formation, the developing means applies the developer over the entire image area and at least one round of the outer circumference of the roller-shaped charging member to the image carrier, and further rotates the roller by rotating the image carrier. Applying a developer on the outer peripheral surface of the roller-shaped charging member, and then transferring a stain and the developer on the roller-shaped charging member onto the image carrier at the same time by applying a bias to the roller-shaped charging member, A bias is applied to the developing unit so that the potential relationship between the image carrier and the developing unit is opposite to that at the time of image formation, until the dirt and the developer on the roller-shaped charging member are collected by the developing unit. The image forming apparatus according to any one of claims 8 to 14, wherein the cleaning unit is separated from the image bearing member during the period. Cleaning means for transferring the developer image visualized on the image bearing member onto a transfer material by a transfer means, and for cleaning and collecting the transfer residual developer on the image bearing member in contact with the image bearing member In the image forming apparatus having
At any time other than the time of image formation, the developing unit applies a developer over the entire image area of the image carrier and one or more turns of the outer periphery of the roller-shaped charging member, and the applied developer is applied to the cleaning unit. While passing through the corresponding position, the cleaning means is separated from the image bearing member to allow the developer to pass therethrough and apply the developer on the outer peripheral surface of the roller-shaped charging member. By applying a bias to the member, the dirt and the developer on the roller-shaped charging member are simultaneously transferred onto the image carrier, and finally the dirt and the developer on the roller-shaped charging member are collected by the cleaning unit. The image forming apparatus according to any one of claims 8 to 14, wherein the image forming apparatus is configured to perform the operation. An image carrier; charging means for charging the image carrier by supplying a bias from a power source to a roller-shaped charging member rotating in contact with the image carrier; Image exposure means for exposing and forming an image, developing means for visualizing the image by applying a bias and a developer, and transfer means for transferring the developer image visualized on the image bearing member onto a transfer material. 17. The method for cleaning a roller-shaped charging member of a contact charging system according to claim 1, wherein the image forming apparatus includes the image forming apparatus.

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