Ricoh Company, Ltd.

Junji Kurokawa

Kazuo Nojima

Toshio Nakahara

Masako Chiba

Hiroshi Yamada

Mitsuo Hasebe

Setsuo Soga

Masumi Ikesue

Masaaki Ogura

Norimasa Sohmiya

Hideo Yamazaki

Itsuo Ikeda

Takeshi Tabuchi

Yukio Noguchi

Tetsuo Sakurai

Hiromi Demizu

Nachio Seko

Tsukasa Adachi

Masaji Ito

Hiroshi Hirose

Kiyotaka Ohta

Toshiaki Hayasaka

Shozo Shimomura

Norimasa Soumiya

Hiroshi Mano

Minolu Fukuda

Seiichi Miyagawa

Masaki Sekizawa

Hiroki Takeda

Hajime Hariu

An electrophotographic image forming apparatus using a charge roller for uniformly charging the surface of a photoconductive element, or image carrier, during image formation, and a charging device having the charge roller. The charging efficiency is enhanced, and a uniform charge distribution is set up by the application of a DC voltage only. This suppresses the increase in the cost of an apparatus, the increase in power source cost, and the generation of a great amount of ozone. As a result, a charging member and a photoconductive element are prevented from being deteriorated while environmental pollution is eliminated.

Image forming apparatus and charging device thereof

An electrostatic charging roller having at least two layers; namely an elastic layer and a surface layer covering a surface of the elastic layer; wherein the surface layer contains low structure acetylene with a particle diameter of 44 to 60 m.mu. to improve uniformity in electrification by the electrostatic charging roller having a surface layer in which conductive particles and non-adhesive resin are dispersed therein. Also dependency of the electrostatic charging roller on humidity is suppressed to a lower level, which makes smaller fluctuation of the electrifying characteristics caused by changes in environmental conditions.

Electrostatic charging roller

In a charging device included in an image forming apparatus for charging an image carrier uniformly, a charge roller has an elastic layer and a surface layer. The elastic layer is made of a substance having a medium electric resistance and having no conductive particles dispersed therein. The surface layer is made of a non-adhering substance having a greater non-adhering property than the substance constituting the elastic layer.

Charge roller for an image forming apparatus

Image forming apparatus which maintains a temperature of a charge roller

In the roller charging apparatus according to the present invention, the charging roller includes a layer of an epichlorohydrin rubber, so that it is possible to eliminate electric nonuniformity of a conductive elastic layer and to be charged by loading only a DC voltage. The charging roller also may have a surface layer formed of polyamide resin or fluorine resin. In addition durability can be improved by setting the roller hardness of the charging roller to 42 (measured by a JISA hardness meter) or more. Further, a roller diameter D.sub.r of the charging roller and drum diameter D.sub.d of the photosensitive drum may satisfy the relation of D.sub.d /D.sub.r .gtoreq.4. A cleaner can also be provided for removing foreign materials, such as toner, from the charging roller, and the cleaner may have a rubber hardness less than that of the charging roller.

Roller charging apparatus and image forming apparatus using the same

There is provided by the present invention an electrifying roller having a roller layer having at least two layers of an elastic layer provided on a peripheral surface of core metal and a surface layer covering the elastic layer, wherein a slope (.DELTA.I/.DELTA.V) of the V-I characteristics of the roller layer is 1 or less, the electrifying roller is rotated in contact with the light-sensing drum, a voltage is loaded from a power supply unit to the core metal of the electrifying roller, and a surface of the light-sensing drum is electrified to a surface potential (Vs).

Electrifying roller, roller electrifying apparatus using the same, and

A charge roller rotatable in contact with a photoconductive element in the form of a drum or a belt and applied with a voltage for charging the element, and an image forming apparatus using the same. The surface of the charge roller is ground in order to remove toner particles and other impurities firmly deposited thereon, as needed. The charge roller is capable of uniformly charging the photoconductive element at all times.

Charge roller and image forming apparatus using the same

An image forming apparatus including a charge roller for providing a charge to a photoconductive member. The charge roller includes a metallic core with a conductive elastic layer covering the metallic core and a surface layer covering the elastic layer. The conductive elastic layer is preferably formed of an epichlorohydrein rubber or a urethane rubber. In addition, the conductive elastic layer and surface layer preferably have thickness and roughness characteristics as discussed herein.

Charge rollers having improved layer structure and/or surface

A device for controlling the application of a bias for development in electrophotographic image forming equipment which forms a latent image on a photoconductive element and develops it by a magnetic brush formed by a dry two-component developer on a developing sleeve to which the bias is applied. A detector is located between the optics and the developing unit for detecting the passage of opposite ends of a charged area of the photoconductive element one by one. The bias is turned on and then turned off, each later than the detection of a particular edge of the charged area by a period of time in which the edge travels from a sensing position to a developing position. The bias applied to the developing sleeve is turned on at the time when the leading edge of the actually charged area of the photoconductive element arrives at the developing position, and it is turned off at the time when the trailing edge of such an area passes the developing position. Voltage is applied to the developing sleeve stepwise such that at least one of the rise and fall of the bias potential occurs in two or more steps.

Bias application control device for image forming equipment

A continuous plural page copying method for a copier determines the size and lengthwise direction of a document which is laid on a glass platen, and produces magnifications on the basis of a relationship between one half of the size of the document in the lengthwise direction and the size of the papers selected. Consecutive pages of the document are reproduced continuously with no regard to the orientation of the document on the glass platen relative to the scanning direction of a scanner. The method reproduces an image on a paper while desirably matching it to the size of the paper.

Continuous plural page copying method for a copier

An electrophotographic color image forming process wherein three light beams each representing image information of one of three primary colors or yellow, magenta and cyan of a color document to be recorded obtained by color separation are projected against an electrophotographic photosensitive member to form electrostatic latent images which are developed by toners of the three different colors, respectively, and printed by transfer-printing, to record a color image. The image information of three colors is simultaneously written to a surface of the photosensitive member as three scanning lines either by successively writing a plurality of sets of three scanning lines each representing image information of one color or by writing image information of different colors of the same set separately in three different zones, so that the scanning lines representing image information of different colors form a repeating series of three stripes of different colors. The electrostatic latent images formed on the scanning lines are excited in positions immediately before developing sections of respective colors and developed by the toners of respective colors to produce toner images of different color which are printed by transfer-printing on a transfer-printing sheet.

Color image forming method

The present invention provides a developing method for electrophotography which is developed to perform the development by electrically insulating the developing electrode from the support of the photosensitive material, together with apparatuses suitable for practicing said method. This developing method is applicable to both the wet inversion development and the magnetic brush inversion development, and produces a negative-positive image having a satisfactory reproducibility particularly with respect to the solid image area thereof.

Inversion developing method for electrophotography and relevant

The apparatus comprises a projection optical system and a copying system. The projection optical system can project an image of an original either onto a screen or to an exposing position of the copying system by switching between two positions. The copying system comprises a plurality of chargers providing different charging conditions in accordance with the types and sizes of copy sheets, by utilizing a change-over switch. A plurality of switches adapted for use with copy sheets of different lengths are arranged along the path of movement of a sheet of paper and, when the switch corresponding to the particular length of copy sheet desired is actuated, the movement of the sheet of paper is stopped, so that the central portion of the copy sheet can be brought into alignment with the optical axis for exposing at all times regardless of the difference in the length of copy sheets. Apparatus can interchangeably mount either a pressing plate assembly for manually feeding one original after another or an automatic feed device which can automatically feed one by one a plurality of originals to the exposing position of the copying system and to eject the same therefrom. By switching between the charging conditions of the chargers, it is possible to produce a positive duplicate of an original irrespective of whether the original is negative or positive. The pressing plate assembly and automatic feed device comprise carriers for effecting moving in X-and Y-directions which are interchangeable, so that it is possible to select a carrier which best suits the size of an original and the amount of movement of the original. The projection optical system comprises a blind coupled to a reflector so as to prevent light from the screen from reaching the exposing position of the copying system, the reflecting surface automatically facing downwardly when the power source is turned off.

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Yokohama, Japan

Junji Kurokawa