Hitachi Koki Co., Ltd.

Hitachi, Ltd.

Masayasu Anzai

Takao Umeda

Nobuyoshi Hoshi

Katsuya Kawai

Koji Kato

Yasuo Takuma

Tsuneaki Kawanishi

Kazuyoshi Tokunaga

Katsuhiko Suzuki

Takashi Suzuki

Yoshitaka Fujinuma

Hiroyuki Mabuchi

Yasuo Kikuchi

Isamu Komatsu

Shinichi Nishino

Teruaki Mitsuya

Isamu Terashima

Hisao Okada

Kiyohiko Tanno

Masato Miwa

Ryoji Kojima

Tadahiro Kaneko

Tomonari Hokkyo

Yoshihiro Gunji

Yosuke Saito

Toshimitsu Harada

Michio Yokosuka

Susumu Akimaru

Kozi Kato

Akio Mukoh

Hirosada Morishita

Yukio Otome

Tatsuo Igawa

Akira Shimada

Takao Kumasaka

Yasuyuki Tsuji

Toshitaka Ogawa

Masayuki Ainoya

Masaharu Tadauchi

Akio Tsujita

Youji Hirose

Koji Doi

Tsutomu Nakagawa

Yuichiro Suzuki

Youichi Takeuchi

Hideo Hirane

Hiroyoshi Matsumoto

Koutaro Yamada

Hisayoshi Kato

Sadaki Maeda

Shin'ya Kobayashi

Akira Takizawa

Masami Yamaki

Yousuke Saito

Shinji Asai

Kunio Fukuchi

Shin-ichi Nishino

Hiroshi Yonezawa

Tomonari Hokkyou

Toshio Twubaki

In a developing system containing a combination of forward-rotating and a backward-rotating developing rollers, a steady quantity of developing agent should be supplied to the developing rollers for high-quality printed images. This requirement can be satisfied by placing a doctor blade between an intersection point, where a line connecting the central axis of one of the developing rollers and its polarity reversing position meets a line connecting the central axis of the other of the developing rollers and its polarity reversing position, and the developing roller pair. Further, the doctor blade should be located on the upstream side of the developing agent flow relative to the central axes of the backward-rotating developing roller and the forward rotating developing roller with its rightmost side (upstream side) in parallel with the line connecting the central axes of the developing rollers, and the doctor gap (on the side of the developing roller to which the developing agent is supplied) should be greater than a minimum gap (doctor gap) between one end of the doctor blade and the surface of the developing roller to which the developing agent is first supplied.

Developing system having a plurality of developing rollers with opposing magnets of same polarity

An electrostatic recording apparatus including: an image carrier including an organic photoconductive photoreceptor having an abrasion-resisting outermost periphery; an exposing unit which exposes the image carrier to form an electrostatic latent image thereon; a developing unit which contains a toner and develops the electrostatic latent image with the toner to form a toner image; a transferring unit which transfers the toner image thus formed onto a recording medium; and a fixing unit which fixes the transferred toner image on said recording medium, wherein the toner contained in said developing unit includes an electrically conductive fine powder attached to the surface thereof.

Electrostatic recording apparatus

In an image forming apparatus, the absolute value (.vertline.VBH-VM.vertline.) of the potential difference between a first development bias electric potential (VBH) and an intermediate electric potential (VM) is set to be smaller (.vertline.VBH-VM.vertline.&lt;.vertline.VBL-VM.vertline.) than the absolute value (.vertline.VBL-VM.vertline.) of the potential difference between a second development bias electric potential (VBL) and the intermediate electric potential (VM).

Electrostatic image forming apparatus

A fixing system for fixing toner images onto an image printing system such that the image printing medium bearing the toner images on the obverse side and the reverse sides thereof is passed through a nip area between a pair of fixing rollers. In the nip area, a rotation speed of a first fixing roller, which comes into contact with a not-yet fixed toner image, which is formed on the obverse side of the image printing medium, is set to be substantially equal to a rotation speed of a second fixing roller, which comes in contact with a not-yet fixed toner image, formed on the reverse side of the image printing medium. This is accomplished by setting the diameters of the various layers of the first fixing roller to be equal to that of the second fixing roller. When the image printing medium is moved through the nip area by the fixing rollers, a moving speed of the upper side of the image printing medium is equal to that of the lower side thereof. Thus, stresses on the image printing medium are not caused, and no character blur takes place.

Apparatus for printing on both sides of an image printing medium by one

A uniform image is obtained by matching the sliding friction force, the moving speed and the developing agent in a developing region of two developing rollers and an electric characteristic of a photosensitive body used for image development. Two developing rollers rotating in directions opposite to each other are used, the moving direction of the first developing roller being opposite to the moving direction of the photosensitive body, and a circumferential speed ratio of a circumferential speed of the first developing roller to a circumferential speed of the photosensitive body is within a rage of 0.5 to 2.5; and the moving direction of the second developing roller is equal to the moving direction of the photosensitive body, and a circumferential speed ratio of a circumferential speed of the second developing roller to a circumferential speed of the photosensitive body is within a range of 1.5 to 3.5. A ratio of the sliding friction force between a magnetic brush for developing agent and the photosensitive body formed in the first developing roller and the sliding friction force between a magnetic brush for developing agent and the photosensitive body formed in the second developing roller is within a range of 0.9 to 2.1.

Electrophotographic apparatus

A predetermined mathematical formula, which defines an occurrence degree of an image defect where the toner layer is thinned or no toner image is formed, is set up, which is valid for a developing device including a reverse turn developer carrier and a forward turn developer carrier. A difference between the total sum A of the values by the above formula showing the occurrence degree of the image defect on the forward turn developing roller and the total sum B of the values by the above formula showing the occurrence degree on the reverse turn developing roller, i.e., (A-B), is selected within a range of -0.56 to +0.5.

Developing device

A dielectric belt 24 is retracted from a photoreceptor 2 before printing, and electrophotographic processes including a process of forming an electrostatic latent image, a developing process and a cleaning process except for a transferring process are repeated. During the repetition of the electrophotographic processes, a surface electric potential in the background of the photoreceptor 2 is measured by the electric potential sensor 10. Alternatively, a quantity of toner adhering to the background of the photoreceptor 2 is measured by the toner sensor 37 and the toner electric charge sensor 36. When the measured values are lower than the reference values, it is judged that no fringe image is generated in the recording condition, and the printing operation is carried out.

Color image forming apparatus and color image forming method thereof

In an electrostatic both-side printing system, a first image forming unit is provided upstream of an image printing medium when viewed in the transporting direction of the image printing medium, and a second image forming unit is provided downstream of the image printing medium. A medium transporting path for transporting the image printing medium is formed between the first and the second image forming units. A first transferring unit, located facing the first image forming unit with the medium transporting path intervening therebetween, for applying no charge onto the rear side of the image printing medium, which does not face the first image forming unit. A second transferring unit being located facing the second image forming unit with the image printing medium with the medium transporting path intervening therebetween, in a state that the second transferring unit is apart from a first toner image formed on the image printing medium by the first image forming unit. In the both-side printing system thus constructed, the first and the second image forming units, and the first and the second transferring units cooperate to form first and second toner images on both sides of the image printing medium, the first and the second toner images being opposite in polarity.

Apparatus for printing images on both sides of an image printing medium

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

A toner for recording electrostatic image having a volume-average particle diameter of from 6 to 10 .mu.m, which exhibits a compression stress of from 50 to 500 kgf/cm.sup.2 at the middle temperature between room temperature and the glass transition temperature of the toner, and a compression stress of from 0.2 to 10 kgf/cm.sup.2 at the middle temperature intermediate between the glass transition temperature and the softening temperature of the toner.

Toner for recording electrostatic image and electrostatic recording

In an image forming apparatus forming an electrostatic latent image on a surface of a photosensitive body by exposing the charged photosensitive body, developing the latent image using a toner to form a toner image, transferring the toner image to a image holding body, and erasing the remaining charge on the surface of the photosensitive body after completion of the transferring, the photosensitive body is formed of a base material consisting of As.sub.2 Se.sub.3 or a-Si, and wherein the wavelength .lambda..sub.0 of the writing light used for the exposure is limited to a wavelength not larger than 780 nm, the wavelength .lambda..sub.1 of charge erasing light used for the charge erasing is limited to a wavelength smaller than 680 nm, and the time T.sub.1 from completion of the exposure to initiation of the development is limited within the range of 70 milliseconds to 300 milliseconds.

Image forming apparatus having a photosensitive body formed of a base

An electrostatic recording control method wherein there are provided a single surface potential sensor between a first and second developer units, a detector for detecting the characteristic of a factor influencing the dark attenuation characteristic of the sensitive body, comprising the steps of: irradiating the surface of a charged sensitive body with the test pattern having prescribed exposure energy by an exposure system to form a test electrostatic image on the photosensitive body; passing the test electrostatic latent image with the developing function of the first developer unit stopping to measure the surface potential of the test electrostatic latent image by the sensor; changing the control setting potential at a position where the sensor is set according to the output from the detector; comparing the potential measured by the passing step with the control setting potential changed by the changing step to control one of the voltage to be applied to the latent image forming charger and the exposure energy for forming the test pattern so that the measurement potential is a control setting potential; forming a test electrostatic latent image on the photosensitive body after the comparing step; applying a prescribed bias to the first developer unit to form the first toner image corresponding to the test electrostatic latent image; and measuring the surface potential of the first toner image to set the bias voltage of the second developer unit according to the value measured.

Electrostatic recording control method and electrostatic recording

The present invention provides a development apparatus capable of improving the development pole of a plurality of development rolls and the rotation speed thereof, thus obtaining stable printing quality. A first development roll rotatable in the opposite direction to the moving direction of photosensitive body is disposed in the upstream of it, whereas a group of second development rolls are disposed in the down stream, which development rolls are rotatable in the same direction as the moving direction of photoconductive body and have magnets of the same polarity. The first development roll and the photoconductive body define a peripheral speed ratio ranging from 0.5 to 1.5, while allowing the second development roll and the photoconductive body to define a peripheral speed ratio ranging from 0.6 to 1.5. A development control member is provided between the first development roll and the group of second development rolls. A toner density detector is provided in the downstream of the last one of the group of second development rolls which is disposed in the most significant downstream. A cross mixer and a carrier member are also provided under the first development roll and the group of second development rolls.

Development apparatus having a plurality of rolls rotated at particular

A bias cleaning system has an electrically conductive brush roller for collecting toner which has to adhered a transfer belt by scrubbing the toner off the transfer belt under a condition in which a direct current voltage of the opposite polarity to the charge of the toner is applied to the brush roller. A corona charger is also provided for decreasing the amount of charge on the toner on the transfer belt in a region of the belt up-stream of the electrically conductive brush roller in the moving direction of the transfer belt.

Bias cleaning system and electrostatic printing apparatus therewith and

An imaging apparatus such that residual toner on a transfer/conveyer mechanism such as a transfer belt and an intermediate transfer material is effectively removable. High-tension voltage opposite in magnetic polarity (plus) to the charged toner and a photosensitive drum is applied to a discharger 15 provided ahead of a drive member 12 for driving a transfer belt 6. The residual toner on the transfer belt 6 is removed by a brush 21, and the residual foreign substances come in contact with the photosensitive drum 1 and move onto the photosensitive drum 1 before a printing operation is started. The foreign substances are then removed by a photosensitive drum cleaner.

Imaging apparatus and method for cleaning transfer/conveyer means

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Ibaraki, Japan

Masayasu Anzai