Hitachi, Ltd.

Brother Kogyo Kabushiki-kaisha

Ricoh Printing Systems, Ltd.

Nobuaki Fukasawa

Akira Sasaki

Hiroyuki Tadokoro

Isamu Terashima

Satoshi Narita

Kazuyoshi Matsuo

Hideyuki Haragakiuchi

Akira Shimizu

Takeshi Kato

Masahiko Saito

Kazuhiro Wakamatsu

Shintaro Yamada

Masashi Yamamoto

Akira Shimada

Takashi Ohmiya

Akiyoshi Hakoyama

Michio Sumiyoshi

Yoshio Ohuchi

Tatsunari Sato

Yuuichi Takano

Shinichi Hosaka

Kiminori Takada

Masashi Okuhama

Katuyoshi Onose

An image forming apparatus is provided that may prevent wasteful image forming in a state in which the loss or partial loss can occur of an image portion. If the length of the supplied sheet in the transport direction is shorter than a regular size by a predetermined value or more, then the laser exposing operation based on the received image data of the second or subsequent pages is stopped.

Image forming apparatus

An image forming apparatus is able to form steady test-pattern toner images for calibration of reflection density detection characteristics with ample toner. The operation consists of forming a test-pattern toner image for calibration of the reflection density detection characteristics, which is formed of a plurality of toner images of different colors aside from a reference test-pattern toner image for controlling image forming conditions, detecting the detection characteristics of a reflection density sensor from the result of detection of the quantity of toner attached to the test-pattern toner image for calibration of the reflection density detection characteristics, and calibrating the output characteristics of the reflection density sensor.

Image forming apparatus and method of detecting the detection characteristics of a reflection density sensor

The rotating speed of a photosensitive body is reduced for preventing deterioration thereof due to ozone in an electrophotographic device which comprises the photosensitive body, a charger which uniformly charges the surface of the photosensitive body, and a motor control unit which performs drive control for a motor which drives the photosensitive body. The motor control unit provides a plurality of speed levels including a first speed level for rotating the photosensitive body during printing and another speed level for rotating the photosensitive body at a reduced speed lower than the speed used during printing. The speed is changed-over between the plurality of speed levels depending on the operating condition. Thereby, deterioration of the photosensitive body due to ozone generated from the charger is prevented, and additional deterioration of the photosensitive body due to rotation thereof other than during a printing operation is also prevented.

Electrophotographic device

An electrophotographic image forming apparatus is capable of restriction or elimination of the occurrence of a density fluctuation, such as a lateral stripe, and thereby can enhance the image quality. The electrophotographic image forming apparatus includes a photosensitive body, exposure device for forming an electrostatic latent image on the photosensitive body, at least two developers for developing the electrostatic image in mutually distinct colors for respectively forming toner images of mutually distinct colors, a transfer device for transferring the toner images of mutually distinct colors on a printing medium in an overlapping manner, and a fixing device for fixing the toner images transferred onto the printing medium. When one of the developers is maintained inoperative, that developer is forcedly operated for a reset operation thereof.

Electrophotographic image forming apparatus

A double-surface printing apparatus, which is small-sized and has a simple construction to make it impossible to take out a sheet, of which one surface has been subjected to printing, from outside. The apparatus includes a paper discharge tray, to which sheets having been subjected to printing are discharged; a sheet reversing mechanism including a reversal/temporary storage unit for guiding a sheet in a direction different from a discharge direction toward the paper discharge tray, once exposing the sheet outside of the apparatus, and rotating conveying rollers in an opposite direction to thereby reverse the sheet; and a protective cover, which covers the sheet conveyed to the reversal/temporary storage unit so that a sheet, of which one-surface has been subjected to printing, cannot be taken out from outside.

Double-surface printing apparatus

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 color printer has means for setting toner image forming areas in the paper sheet convey direction in respect of respective colors, means for detecting a reference position on a photosensitive belt, and image formation start position setting means responsive to the reference position to set a toner image (electrostatic latent image) formation start position in the rotation direction of the photosensitive belt. When the paper sheet length is longer than the outer peripheral length of an intermediate transfer member, the image formation start position setting means sets, for colors other than the final color, a printing area which is shorter than the outer peripheral length of the intermediate transfer member and sets, for the final color, a printing area which begins immediately after a seam position of the photosensitive belt and conforms to the paper sheet length. Through the above setting, when toner images of two colors are superposed to print a color image, the printing area of the final color can be set to a desired range in the paper sheet length direction regardless of the outer peripheral length of the intermediate transfer member, thereby improving the printing speed and preventing degradation of quality.

Color image control apparatus having photosensitive body and

An apparatus for transferring toner images which is capable of executing optimum discharging control even where the environment, the material of the paper, and the kind of paper may be changed. First, the load current is detected when the transferring roller 11 is pressed to a transferring drum 6. The detected load current is converted to a characteristics detecting signal S6 at a signal converting section 109. An environment is selected on the basis of the characteristics detecting signal S6. Next, the load current flowing to the transferring roller 11 is detected when an AC discharger 14 is stopped. The detected load current is converted to characteristics detecting signal S6 at the signal converting section 109. A voltage control signal is selected based on the converted characteristics detecting signal S6, the environmental information, and the paper kind. A power source for discharging 22 is controlled by the selected voltage control signal so that the transferring becomes optimum. Accordingly, even if the kind of paper and environment is changed, optimum transferring and high transferring efficiency can be maintained.

Toner transferring device

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 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.

In a serial thermal transfer printer or serial thermal printer comprising; a thermal head having a plurality of heat elements arrayed in a line; and means for selectively energizing and driving the plurality of heat elements in synchronous relation with the relative movement between the thermal head and the ink ribbon or heat sensitive paper, wherein when printing dots are successively positioned in the direction of the relative movement between the thermal head and the ink ribbon or heat sensitive paper, printing timing of the last dot is set ahead so as to be earlier than normal printing timing. When the previous printing data is '1' (recording) and the subsequent printing data is '0' (not recording), the position of the present printed dot is shifted toward the previous printed dot to compress the entire width in case of two or more successive dots. Since the printing head is traveling continuously during printing, the position of the present printed dot can be shifted toward the previous printed dot by advancing the printing timing. If the previous printing data is '0' and subsequent printing data is '1', it is apparent that a similar effect can be obtained by setting the printing timing backward so as to shift the position of the present printed dot toward the subsequent printed dot.

Growing community of inventors

Hitachi, Japan

Nobuaki Fukasawa