Hitachi, Ltd.

Hitachi Koki Co., Ltd.

Isamu Terashima

Hiroyuki Tadokoro

Akira Sasaki

Nobuaki Fukasawa

Masahiko Saito

Kazuhiro Wakamatsu

Toru Miyasaka

Masayasu Anzai

Tadashi Okano

Mitsuo Suzuki

Katsumi Kumada

Tetsuro Akasaki

Kazushige Oonishi

Shoji Takeya

Michio Sumiyoshi

Hideyuki Haragakiuchi

Susumu Saito

Takeshi Kato

Kimio Tatsuno

Junichi Matsuno

Masashi Yamamoto

Akira Shimada

Masaru Nakano

Tomoji Kitagishi

Syoji Sagae

Masayoshi Sunada

Shoichi Ito

Yoshifumi Homma

Mitsugu Asano

Shoji Ukei

Tomio Hayano

Shigeru Uchida

Kazuyoshi Matsuo

Yoshifumi Ono

Toshio Twubaki

Eiiji Senba

Masashi Okuhama

Katuyoshi Onose

An image forming apparatus in which a distance along a photosensitive belt from a cleaning unit to an exposing position is set to be shorter than a distance from the rear end of a print image to the front end of the following print image, so that a latent image is not formed by an exposing unit when a joint of the photosensitive belt passes the cleaning unit.

Image forming apparatus with reduced latent image vibration caused by photosensitive belt joint

A toner bearing body unit is constituted as one assembled unit including a toner bearing body for holding toners supplied from a toner supply roller of a housing main body at an outer peripheral surface thereof, a toner layer thickness regulating member for electrically charging the toners by applying pressure toward the outer peripheral surface of the toner bearing body and for forming a toner thin layer on the toner bearing body, and a holding member for holding the toner bearing body and the toner layer thickness regulating member. The toner bearing body unit is constituted to be directly attachable to and detachable from an outer side of the housing main body of a developing apparatus. Accordingly, an uniform toner thin layer having a predetermined thickness can be formed stably on the toner bearing body during a long period of use, and the developing apparatus reconstructed so that replacement of the components thereof can be carried out easily. Further a developing apparatus having a good recycling performance can be provided.

Developing apparatus and image forming apparatus having the same

A developing apparatus includes toner powder in the form of fine colored powder, a toner carrier, and a frictional controlling member for contacting under a pressure with the toner carrier under pressure to frictionally charge the toner powder and form a thin toner layer on the toner carrier. The toner carrier on which the thin toner layer is formed is rotated so as to transport the thin toner layer to an opposing location on a toner image carrier on which an electrostatic latent image is formed to convert the electrostatic latent image into a visible image. The developing apparatus includes a toner supply roller disposed in rotating contact with the toner carrier at a side of the toner carrier, the frictional controlling member being provided at a position in contact with the toner carrier downstream of the toner supply roller; and a rotatable toner scraping member is provided in a neighboring relationship below the toner supply roller and the frictional controlling member.

Image forming apparatus having improved toner carrier arrangement

An electrophotographic imaging apparatus includes a toner image holding body, a transcription unit for transcribing the toner image on the toner image holding body onto a recording medium, and a conveyor for conveying a recording medium toward the toner image holding body and transcription unit. A judging device will judge whether printing is of a first page or not and if it is decided that printing is to be performed on a first page, a first measuring device will measure the electrical characteristic of the toner image holding body prior to the feeding of a recording medium and a transcription voltage will be set depending of this measured result. Thereafter, the recording medium will be conveyed toward the transcription unit where the electrical characteristics of the non-printing region on the recording medium will be measured via a second measuring device and the transcription voltage will be further adjusted. If it is judged that the recording sheet is not the first sheet, only the second measuring and adjusting will be performed. In this manner, transcribing of a toner image can always be performed regardless of the kind of paper being used and/or changes in the environment (temperature, humidity) and a high transcribing efficiency can be attained.

Electro-photographic apparatus having transfer bias control

A developing magnet roller is provided on a developing frame, and a developing agent accommodating cartridge and a toner accommodating cartridge member are fitted detachably into the developing frame. The toner accommodating cartridge member is fitted detachably into the developing agent accommodating cartridge. A developing agent is recovered in the developing agent accommodating cartridge. The developing agent and the developing agent accommodating cartridge are exchanged together from a developing apparatus. The new developing agent accommodated in the exchanged new developing agent accommodating cartridge is circulated by the developing magnet roller. The exchange for the developing agent in the developing apparatus can be realized without the lowering of the developing performance.

Developing apparatus having developing agent accommodating cartridge and

An intermediate transcription drum is supported so as to be driven in contacting relationship with a photosensitive belt. The rotating speed of the photosensitive belt driving motor is controlled by a control unit such that one rotation cycle of the intermediate transcription drum becomes a given cycle. An adjustment of the speed control data for the photosensitive belt driving motor is performed in the interval between electrostatic latent image forming. Thereby, a speed difference between the photosensitive belt and the intermediate transcription drum does not occur, and a plurality of the toner images can be transferred and accurately superposed onto the outer surface of the intermediate transcription drum.

Color printer with transfer and superposition of different color toner

The disclosure is concerned with an electrophotographic apparatus comprising a toner image supporting member on which a toner image developed on an electrostatic latent image is formed, transferring means for transferring the toner image on said toner image supporting member to a recording medium, conveying means for bringing the recording medium into contact with the image supporting member, a fixing roller and a compression roller in contact with each other to fix the toner image on the recording medium, heating means disposed inside at least one of the fixing roller and the compression roller, wherein there are provided temperature detection means for detecting the surface temperature of the fixing roller and state detection means for detecting the state of the fixing apparatus before starting of the fixing apparatus.

Electrophotographic apparatus and electrophotographic method

A color electrophtographic printer has: a photosensitive drum on which electrostatic latent images are formed according to print data separated by colors; a plurality of developing units each including a developing powder container accommodating a two component developing powder formed by mixing carriers and toners, an apparatus for agitating the developing powder, and a unit for supplying the toners in the developing powder container; a unit for selecting one of the plurality of developing units according to color to be developed and for activating the same to develope the corresponding electrostatic latent image formed on the photosensitive drum; and a control unit for controlling the respective operations. A control unit is further provided for counting colored print data dots contained in print data for respective colors and for additionally activating the developing powder agitating prior to a subsequent developing operation for any of the developing units which have experienced developing of the electrostatic latent images formed with colored print data dots in excess of a predetermined count.

Color electrophotographic device with developer stirring

A developing magnet roller is provided on a developing frame and a developing agent accommodating cartridge is fitted detachably into the developing frame. A toner accommodating cartridge unit is fitted detachably in the developing agent accommodating cartridge. A developing agent is recovered in the developing agent accommodating cartridge. The developing agent and the developing agent accommodating cartridge are exchanged together from a developing apparatus. The new developing agent accommodated in the exchanged new developing agent accommodating cartridge is circulated by the developing magnet roller. The exchange for the developing agent in the developing apparatus can be realized without the lowering of the developing performance.

A color electrophtographic printer has a photosensitive drum on which electrostatic latent images are formed according to print data separated by colors; a plurality of developing units each including a developing powder container accommodating a two component developing powder formed by mixing carriers and toners, an apparatus for agitating the developing powder, and a unit for supplying the toners in the developing powder container; a unit for selecting one of the plurality of developing units according to color to be developed and for activating the same to develope the corresponding electrostatic latent image formed on the photosensitive drum; and a control unit for controlling the respective operations. A control unit is further provided for counting colored print data dots contained in print data for respective colors and for additionally activating the developing powder agitating prior to a subsequent developing operation for any of the developing units which have exprienced developing of the electrostatic latent images formed with colored print data dots in excess of a predetermined count.

A color electrophotographic device includes, a color toner image producing device which produces a color toner image on a rotatable photo sensitive drum by forming four toner images thereon; an image transferring device which transfers the color toner image on the photo sensitive drum onto a recording medium; a fixing means which fixes the color toner image on the recording medium; a transferring device which transfers the recording medium; a recording medium selecting and feeding device which selects one of an ordinary paper and a transparent sheet to serve as the recording medium and feeds the selected one to the transferring device; and a control device which controls the operations of the devices referred to above and includes a first and a second control function which are rendered operative when the transparent sheet is selected as the recording medium, wherein the first control function causes the photo sensitive drum to perform one idle rotation before the image transferring device beings to transfer the color toner image carried on the photo sensitive drum onto the recording medium; and wherein the second control function causes the transferring device to reduce the transferring speed for the transparent sheet to a speed lower than that for the ordinary paper only during the operations of the image transferring device and the fixing means and the transferring speed reduction is accomplished after the last toner image has been formed on the photo sensitive drum and during the idle rotation thereof.

Color electrophotographic device and method

In an electrophotographic recording apparatus, toner images of different colors formed on a photosensitive belt are transferred in overlapping fashion to an intermediate transfer drum to form a color toner image and the color toner image is transferred to a secondary recording medium by means of a transfer unit and then fixed. The intermediate transfer drum includes an electrically conductive drum substrate and a dielectric layer whose resistance is adjusted to a predetermined range, and the drum substrate is connected to earth potential so that setting of an electric field for toner image transfer from the photosensitive belt may not interfere with setting of an electric field for toner image transfer by the transfer unit. Efficiencies of transfer at the two transfer sections can be improved to provide a color image of high quality and the apparatus can be reduced in size.

Electrophotographic recording apparatus

An outer peripheral length of an intermediate transfer drum of a color laser beam printer is constituted in which a number of a beam detection signal obtained by one rotation of the transfer drum is formed as an integral number of a face number of a polygon mirror. A passing-through detection means detects the passing-through of a specified position mark on a photosensitive body belt and is provided on the photosensitive body drum at predetermined position. An image data requirement signal generating means controls a generating timing of an image data requirement signal for forming a toner image by the passing-through detection signal. A scanning line at a raster direction based on the beam detection signal after the transfer drum has rotated at one rotation returns and overlapped on a scanning line position formed on the first beam detection signal as a standard. A plural toner images having a different color each are formed on the transfer drum without color offset.

Color image electrophotographic apparatus having photosensitive body and

Each of color toner images is formed on a photo-sensitive drum using a plural development units. An exposure process and a development process for a color image information are carried out repeatedly corresponding to a respective hue of the image information. The toner images of n colors are transferred to the drum by contacting a recording paper to the drum. A record mode is selected in accordance with a length in a peripheral direction of the drum of the image information against a peripheral length of the drum. When the length of the image information is longer than the peripheral length of the drum, N times transfer processes are selected as the record mode. Then the length of the image information is divided into N areas. The image information of n colors existing in every divided area is formed dividedly on the drum. The color image is recorded on a full length of the paper. Besides, when the length of the image information is shorter than the peripheral length of the drum, one time transfer process is selected as the record mode.

Color image electrophotographic apparatus for printing long-size copy

A developing apparatus operates to develop an electrostatic latent image by using developer which is a mixture of carrier particles and toner particles. Upon detecting a fall in the toner concentration in the developer, a toner supply device supplies stored toner particles to the developer. The supplied toner particles are mixed, by stirring, with the developer by a stirring device. The toner supply device includes a supply roller covered by a short texture or a porous elastic material having a predetermined high resistivity in contact with a circulation current of developer, and a bias power source which applies a bias voltage between the supply roller and the circulation current of developer such that the supply roller and the supplied toner particles have the same voltage polarity.

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Hitachi, Japan

Isamu Terashima