Hitachi Koki Co., Ltd.

Ricoh Company, Ltd.

Katsuhiro Akinaga

Yasuo Kikuchi

Tomio Sugaya

Koutarou Yamada

Tomonari Hokkyoh

Hiroaki Maeda

Takashi Suzuki

Yasuyuki Tsuji

Yosuke Saito

Motoji Kurobane

Masaaki Akutsu

Hirobumi Ouchi

Kaoru Kataoka

Hirofumi Ouchi

A developing device in an image forming apparatus includes: a first developer carrier that rotates in a same direction as a rotating direction of an image carrier of the image forming apparatus so as to supply developer to the image carrier; and a second developer carrier that rotates in a direction opposite to the rotating direction of the image carrier so as to supply the developer to the image carrier. The developing device simultaneously performs a refreshing operation of performing replacement of the developer and a filming removal operation of causing the image carrier to rotate idle while forming an image for use in the refreshing operation and causing the first and second developer carriers to rotate in their respective rotating directions.

Image forming apparatus and image forming method

The disclosed image forming apparatus includes a rotatable image holding body configured to hold an electrostatic latent image on a surface of the image holding body, a developing device including a forward rotation developing roller rotatable in a same rotational direction as that of the rotatable image holding body and a reverse rotation developing roller rotatable in a reverse rotational direction to that of the rotatable image holding body, which supply a two-component developer to the surface of the image holding body to form a toner image corresponding to the electrostatic latent image, and a control unit configured to control rotation of the image holding body, the forward rotation developing roller, and the reverse rotation developing roller to supply the two-component developer. The control unit controls the rotation of the image holding body to start after a predetermined time period from starting the rotation of the forward rotation developing roller and the reverse rotation developing roller.

Image forming apparatus including counter-rotating developing rollers and controlling method

An electrophotographing method using a corona charging device having areas with and without a grid. Prior to at least a second exposure step, a charging step is effected using both areas relative to the grid. A voltage applied to the grid in the second charging is lower than that in the first charging, and lower than a potential of a non-image region of the photosensitive body.

Electrophotographing method using carona charging device having areas

In an image printer performing multi-color printing, two magnetic poles having the same polarity are provided adjacent to each other in a position facing the printing body of the second developing agent holding body provided in the second developing unit, and development is performed under a condition satisfying the following formulas;

Image printer

A method of preventing colors from being mixed in a two-color image forming apparatus. The surface of a photoreceptor is uniformly charged. A first latent electrostatic image formed on the photoreceptor surface is developed with a one-component developer so as to form a first toner image. A second latent electrostatic image formed on the photoreceptor surface is developed with a two-component developer so as to form a second toner image. The first and second toner images are simultaneously transferred onto a recording medium. In a preferred embodiment, the one-component developer is a magnetic toner, while the two-component developer is the combination of a nonmagnetic toner and a magnetic carrier. The magnetic toner and the magnetic carrier are preferably powder made of substantially the same materials.

Method of preventing colors from being mixed for a two-color image

An apparatus for printing on opposite surfaces of a strip of printing paper using two electrophotographic printing units wherein each printing operation is of high quality and thermal damage to the printing is minimized. The apparatus includes a first electrophotographic printing unit for printing on the front surface of the printing paper, a buffer unit for temporarily holding the printing paper discharged outside of the first electrophotographic printing unit, a turn unit for turning over the printing paper, and a second electrophotographic printing unit for printing the reverse surface of the printing paper. A toner having a low melting temperature is employed for each of the first and second electrophotographic printing units so that developing treatment is conducted only with the aid of a heat roll but without any use of a preheating plate. A back-up roll adapted to cooperate with the heat roll is coated with a tetrafluoroethylene-based synthetic resin. The second electrophotographic printing unit is provided with a paper presser for squeezing the printing paper against a photosensitive drum only within the printing width range. A retract mechanism is operatively connected to the paper presser.

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Ibaraki, Japan

Katsuhiro Akinaga