Ricoh Company, Ltd.

Mieko Kakegawa

Noriyuki Kamiya

Tsuyoshi Imamura

Kyohta Koetsuka

Sumio Kamoi

Makoto Nakamura

Kenzo Tatsumi

Masayuki Ohsawa

Yoshiyuki Takano

Hiroya Abe

Tadaaki Hattori

Takashi Innami

Rei Suzuki

Kenji Narita

Toshihiro Atsumi

Takahiro Yasunaga

Masayuki Takeshita

Sumio Kamio

Kyota Koetsuka

The long magnet includes a magnet block made of a mixture of rare earth magnetic powder, thermoplastic resin particles, fluidity additive, pigment, wax and charge control agent, and a reinforcing member to reinforce the magnet block. At least part of the reinforcing member is arranged inside of the magnet block.

Long magnet, production method thereof, magnet roller and image forming device

A development magnet roller for use in a development roller of an electrophotographic image forming apparatus is provided. The development magnet roller has a development pole to form a magnetic field causing a developer born on a surface of the development roller including the development magnet roller to rise in a form of a series of ears in a development area of the image forming apparatus where the development roller opposes an image bearing member, and in a magnetic flux density distribution in a normal line direction of the development pole, a peak magnetic flux density is 120 mT or greater, a zero gauss region width is 70&#xb0; or greater, and a half-value region width is 40&#xb0; or smaller.

Development magnet roller, development device, process cartridge and image forming apparatus

A developing roller includes a developing sleeve having a nonmagnetic material, and a magnet roll provided inside the developing sleeve and formed by dispersing a magnetic powder in a polymer compound. A portion of the magnet roll corresponding to a developing pole of the magnet roll is equipped with a main-pole molded magnet whose magnetic force per unit of volume is greater than that of the magnet roll. A magnetic pole adjacent to the developing pole of the magnet roll downstream in the developer conveyance direction has a peak magnetic flux density on the developing sleeve greater than that of the developing pole, and has a half value width, which is the width of the magnetic pole at which a magnetic flux density of one-half the peak magnetic flux density is exhibited, greater than that of the developing pole.

Developing roller, developing apparatus, process cartridge, and image formation apparatus

In a developing device for an image forming apparatus of the present invention, use is made of a magnetic molding produced by compression-molding a magnet compound material in a magnetic field. The magnet compound material contains, in addition to magnetic powder and fine, thermoplastic resin grains that are major components, at least one of a pigment and a charge control agent.

Image forming apparatus and developing device therefor

A developing device for developing a latent image formed on an image carrier of the present invention includes a rotatable, nonmagnetic developer carrier, and a magnetic field generating member for generating a magnetic field in a developing zone where the developer carrier faces the image carrier. The magnetic field generated causes a developer deposited on the developer carrier to rise in the form of a magnet brush. A magnetic pole for development is located upstream of a position where the developer carrier and image carrier are closest to each other in a direction of rotation. A magnetic force, as measured on the surface of the developer carrier, increases from the position of the magnetic pole toward a position where the magnet brush finally leaves the image carrier.

Developing device and process cartridge with predetermined magnetic force for an image forming apparatus

A developer carrier for an SLIC developing system includes a developing sleeve and a magnetic roll having a plurality of magnetic poles. A narrow development nip is formed by narrowing the width of a development pole forming a magnet brush and by narrowing a developer rising region in a developing region where a flux density attenuation ratio of the development pole is 40% or more. A half-value width of the flux density of the development pole is 22&#xb0; or less and the flux density variation rate is 4.0 mT/Deg or more in a circumferential direction in a part where the flux density in at least half of that of a downstream side of a developer carrying direction from a peak magnetic force position of the development pole is 90% or less.

Developing device and an image forming apparatus including the same

A developing roller of the present invention is made up of a nonmagnetic sleeve and a magnet roller disposed in the sleeve. The magnet roller includes a cylindrical magnet produced by molding a mixture of magnetic powder and a high polymer, and a single rare-earth magnet block mounted on the magnet at a position corresponding to a main magnetic pole for development. The cylindrical magnet is magnetized such that magnetic poles adjoining the main magnetic pole are opposite in polarity to the main pole. The main pole and each pole adjoining it make an angle of 45&deg; or less therebetween.

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Kanagawa, Japan

Mieko Kakegawa