Hitachi, Ltd.

Hitachi Koki Co., Ltd.

Ricoh Printing Systems, Ltd.

Hitcahi, Ltd.

Takao Kumasaka

Yuzuru Simazaki

Teruaki Mitsuya

Nobuyoshi Hoshi

Shigetaka Fujiwara

Yasuro Hori

Tatsuo Igawa

Isamu Komatsu

Youji Hirose

Kunio Satoh

Yasuo Takuma

Shinichi Nishino

Tomio Sugaya

Masato Yamada

Noboru Tokuyasu

Shinya Kobayashi

Susumu Tateyama

Takao Umeda

Toru Miyasaka

Masayasu Anzai

Yukio Otome

Hisao Okada

Kiyohiko Tanno

Seiji Maruo

Yasuo Kikuchi

Atsushi Onose

Akira Terakado

Masaru Higaki

Ikuo Shimokobe

Shigetaka Fumiwara

Kunio Fukuchi

Susumu Edo

Shigetaka Fujiware

A multi-beam image recording device is capable of recording high-quality high-resolution images without positional errors by exposing test patterns for measuring positional errors of beam spots of each laser beam in main and subsidiary scanning directions, calculating the positional errors of beam spots using a correcting device, controlling the quantity of exposure according to the result of calculation, and thus correcting the positional errors in main and subsidiary scanning directions.

Image recording device and an image recording system

A multi-color image forming apparatus is capable of decreasing the amount of ozone generation which occurs during the formation of a multi-color image. For this purpose, a charged latent image having a tri-level electric potential is formed on a positive charging photoconductor by a charging means and an exposing means. A first color toner having one of a positive polarity and a negative polarity is caused to adhere onto one of the charged latent images having the highest electric potential level at a first developing unit of the apparatus, and a second color toner having the other polarity is caused to adhere onto the other of charged latent images having the lowest electric potential at a second developing unit of the apparatus. After that, the polarity of the toner having the negative polarity is reversed using a positive corona produced by a pre-transfer charging means to unify both polarities of the two color toners, and then both toners having the unified polarity are s transferred onto a sheet of paper.

Multi-color image forming apparatus having arrangements for reducing

By employing a developer using ferrite system carriers, a developing process can be carried out using a low brushing force by a magnetic portion having the same polarity in a developing unit in a developing roller. A relationship between a circumferential speed Up (mm/sec) of a photoconductor, a ratio K of a circumferential speed of a developing sleeve of the developing roller to the circumferential speed of the photoconductor, and a developing potential difference .DELTA.V (V) is set to 1.5.ltoreq.(K.times..DELTA.V/Up).ltoreq.2.1.

Developing apparatus and picture image forming apparatus

In a developing apparatus, a developing roller has a toner layer formed on a surface thereof, which toner layer is brought into contact with a photoconductor. A magnetic conveying roller having a magnet body is arranged rotatively close to the photoconductor. A regulating plate is provided at an outer periphery of the conveying roller.

Developing apparatus and color electrophotographic apparatus using the

An image formation method for forming an image of a plurality of colors through a charging step, an image exposing step, a developing step and a transferring step, wherein the image exposing step is made up of a first image exposing step and a second image exposing step, the developing step of at least one color is carried out after the first image exposing step, and in the subsequent second image exposing step, the toner image area formed by the developing step is exposed and charge latent images for forming toner images of the rest of the colors are formed while a potential of the toner image area is selectively shifted.

Image formation method and image formation apparatus

A developing apparatus in which a stationary multipole permanent magnet is placed in a sleeve and in which development is performed by bringing a developer, which contains at least carrier and toner particles and is held on the periphery of a sleeve by use of the magnetic force of the multipole permanent magnet, into contact with a photo-conductive body owing to the rotation of the sleeve. For securing image density and for preventing the deposition of carrier onto the photo-conductive body, two magnetic pieces, each of which is arranged lengthwise in the direction of the axis thereof and which have the same polarity, are placed in a region in the multipole permanent magnet which faces the photo-conductive body in such a manner as to adjoin in the circumferential direction of said permanent magnet. This results in generation of the distribution of a magnetic field which has two peaks of magnetic force. The position at which the second one of the two peaks of the magnetic force is formed, downstream in the direction of rotation of the sleeve, is set at the nearest point between the photo-conductive body and the sleeve. Thereby, even when development is performed by bringing the developer into light contact with the photo-conductive body, the image density can be secured. Further, the carrier can be prevented from depositing on the photo-conductive body.

Developing apparatus for an electrophotographic machine

In a developing apparatus in which a developer containing magnetic particles is carried on a developer carrier to form a magnetic brush and a latent image on a latent image carrier opposing the developer carrier is developed by the magnetic brush, the magnetic brush bristle height and the developing gap are controlled to keep density of a first color image and density of a second and the ensuing color images in color development at predetermined values or more, thereby maintaining quality of printed images stably. There are also provided method and apparatus of measuring the bristle height of the magnetic brush of the developing apparatus, which bristle height is a parameter indispensable for control of the above developing condition, under the dynamic condition that the developing roller rotates.

Magnetic brush with bristle height equal to developing gap

Each of a charging process on and after a second time is carried out by a charging means having a controlling electrode. The relationship between a controlling potential (Vg) applied to the controlling electrode of each charming means, the target surface potential (Vo) of a non-image portion of a surface of a photosensitive body and the direct current component potential (Vdc) of a developing bias potential in each developing process is satisfied by the formula, which is .vertline.Vo.vertline.&gt;.vertline.Vdc.vertline..gtoreq..vertline.Vg.vertlin e.. Thereby the corona current ia supplied to flow sufficiently, it can rise the surface potential of a toner image portion of the surface of the photosensitive body after the re-charming without the excessive rise of the surface potential of the non-image portion of the photosensitive body. The surface potential of the toner image portion of the photosensitive body after the re-charging becomes to higher than the direct component potential (Vdc) of the developing bias potential, it can prevent from mixing the toners having other color.

Method of multi-color recording using electro-photography process and

An image recording apparatus including a photosensitive medium. A voltage is applied between the photosensitive medium and a developing sleeve of a developing unit, and a current flowing between the photosensitive medium and the developing sleeve is measured to be converted into a pulse waveform which is then compared by a predetermined reference value. On the basis of the result of the comparison, a gap is determined between the photosensitive medium and the developing unit, which is then advanced or retracted toward or from the photosensitive medium in accordance with the determined gap. Owing to the recording method carried out by the image recording apparatus, the gap can be selectively determined by observing the current waveform pattern of the current flowing between the photosensitive medium and the developing sleeve while decreasing gradually the gap therebetween, whereby a relation between the gap and height of a magnetic brush can definitely be established. Since the gap can be set within a range from a value representing an initial contact state in which the magnetic brush starts to contact with the photosensitive medium to a value representing a wholly contact state in which the whole magnetic brush contacts with the photosensitive medium with the aid of a current curve of the current flowing between the photosensitive medium and the developing sleeve, a contacting force of the magnetic brush bearing on the photosensitive medium can be weakened.

Image recording method including determining a gap between a

An electrophotographic recording apparatus is provided having a reduced overall size. The space around a photosensitive member required for the developing unit to be located is minimized, more particularly, it i minimized in the lengthwise directional space. In the electrophotographic recording apparatus having a photosensitive member which moves at a predetermined speed; an exposure device for exposing the photosensitive member; a developing unit for developing an electrostatic latent image obtained by the exposure; and a transferring device for transferring a developed visible image to a recording paper sheet or the like, the developing unit is composed of developing devices, a plurality of supporting members for supporting the developing devices and an element for rotating the supporting members. The supporting members can be rotated while making a portion adjacent to a widthwise directional end of the photosensitive member to be a supporting point in a range from a state where the surface of the photosensitive member and the surface of a developing roll of each developing device run parallel to each other to a state where they are positioned substantially perpendicular to each other.

Electrophotographic recording apparatus having a plurality of developing

A transfer apparatus for electrophotography is disclosed in which the resistance values of a transfer belt and the recording paper are measured, and the current value applied to a device for charging a member is set on the basis of the electrical resistance values. The charging device of the transfer belt is adapted to be taken up and reeled out and to circulate along a track. This configuration assures a stable transfer characteristic against the secular environmental variations of the component elements, lengthens the intervals of replacement of the charged member, and hence increases the mechanical life of the transfer apparatus and the electrophotographic apparatus using the same.

Corona deterioration and moisture compensation for transfer unit in an

A fixing apparatus comprises; a conveyor belt device for conveying a recording medium on which toner images are developed, having two non-perforated conveyor belts and a plurality of perforated conveyor belts arranged between the two non-perforated conveyor belts; a radiant heating device arranged above the conveyor belt device, for heating the recording medium situated on the conveyor belt means by a flash and for fusing and fixing the toner images on the recording medium; and a suction device arranged in an area that is directly illuminated by the flash from the radiant heating means, below the plurality of perforated conveyor belts, so as to be completely covered by the plurality of perforated belts; and further includes at least one of features of; a cleaning device arranged outside of the area that is directly illuminated by the flash from the radiant heating means, for eliminating foreign matters on outer surfaces of the plurality of perforated conveyor belts; a tension adjusting device arranged outside of the area that is directly illuminated by the flash from the radiant heating means, for adjusting tension force of each of the conveyor belts; a gathering device arranged inside of the area that is directly illuminated by the flash from the radiant heating device below the suction means, for gathering the foreign matters dropped from the recording medium; and the plurality of perforated conveyor belts each having a bright color.

Radiant heat fixing apparatus

In a multi-color LBP (laser beam printer) or a full-color LBP, two image producing elements each composed of charge-exposure-develop devices are arranged around one drum, and each of the image producing elements includes a developer capable of color changing for achieving a color change developing in every one revolution. In this way, it is made possible to practice a multicolor printing or a full-color printing in two rotations of one photosensitive drum. This printer has a higher printing speed and a smaller size of the apparatus in comparison with that of a one drum four rotation system and that of a one drum one rotation system, respectively. Further, the system includes several features common to two-color LBP printing art, making it possible to conveniently utilize the latter printing art.

Multi-color electrophotograph apparatus

An electrophotographic image transfer member of bias-roller transfer type is capable of pressing a recording medium into contact with a toner image. The image transfer member has a rotatable supporting member, an elastic member provided around the supporting member, and a conductive resin layer formed on the surface of the elastic member. An electrical path is formed to enable supply of a bias voltage to the conductive resin layer. An image transfer device has the image transfer member and a cleaner capable of removing toner from the image transfer member upon frictional contact therewith. An electrophotographic apparatus has an image transfer member for bringing the recording medium into pressure contact with the toner image and for applying the bias voltage, and a mechanism for bringing the image transfer member towards and away from the photosensitive member in response to a signal indicative of execution of one of several basic steps of the electrophotographic process.

Electrophotographic image transfer member, electrophotographic image

Disclosed is an electrical power supply for use, for example, for a flash fusing device in an electrophotographic recording apparatus, in which a DC high voltage is generated from a low voltage of an AC power supply so that the high voltage DC energy is momentarily consumed or discharged. The electrical power supply is configured in a manner so that, in order to make unnecessary a charging capacitor and a current limiting resistor for preventing rectifier elements from being damaged, at least some of the rectifier elements are constituted by rectifying control elements such as thyristors or transistors and a control signal is given to those rectifying control elements so as to make the rectifying control elements be in an isolated state. By use of such a configuration, the electrical power supply can be reduced in size as well as in power loss. The effect can be fully exhibited not only in a fusing apparatus employing the electrical power supply but in a recording apparatus employing such a fusing apparatus.

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Takahagi, Japan

Takao Kumasaka