Hitachi Metals, Ltd.

Fuji Xerox Co., Ltd.

Ryuji Gotoh

Yoshinori Kobayashi

Hiroshi Iwasaki

Takashi Takami

Naoki Mochi

Masumi Asanae

Takashi Fuchiwaki

Fumio Kimura

Yoshikazu Okamoto

A method for producing a sintered ferrite magnet having an M-type ferrite structure and represented by: CaRBaFeCo, (by atomic ratio), where 0.3&#x2266;1&#x2212;x&#x2212;y&#x2266;0.65, 0.2&#x2266;x&#x2266;0.65, 0.001&#x2266;y&#x2266;0.2, 0.03&#x2266;z&#x2266;0.65, 4&#x2266;n&#x2266;7, and 1&#x2212;x&#x2212;y&#x3e;y. The method includes mixing a Ca compound, an R element compound, a Ba compound, an iron compound and a Co compound as starting materials; calcining the starting materials to obtain calcined bodies; pulverizing the calcined bodies to obtain a calcined powder; providing recycled materials having an M-type ferrite structure and being represented by the above formula; pulverizing the recycled materials to obtain a recycled material powder; mixing the recycled material powder with the calcined powder to form a moldable material; molding the moldable material to obtain green bodies; and sintering the green bodies to obtain the sintered ferrite magnet.

Rotating machine, bonded magnet, magnet roll, and method for producing sintered ferrite magnet

A rotating machine comprising a sintered ferrite magnet having an M-type ferrite structure, comprising Ca, an R element that is at least one of rare earth elements and indispensably includes La, Ba, Fe and Co as indispensable elements, and having a composition represented by the formula: CaRBaFeCo, wherein (1&#x2212;x&#x2212;y), x, y, z and n represent the contents of Ca, the R element, Ba and Co, and a molar ratio, meeting 0.3&#x2266;1&#x2212;x&#x2212;y&#x2266;0.65, 0.2&#x2266;x&#x2266;0.65, 0.001&#x2266;y&#x2266;0.2, 0.03&#x2266;z&#x2266;0.65, 4&#x2266;n&#x2266;7, and 1&#x2212;x&#x2212;y&#x3e;y; a bonded magnet comprising ferrite powder having the above composition and a binder, and a magnet roll, at least one magnetic pole portion of which is made of the above bonded magnet.

A developing roll includes a tubular sleeve driven for turn, and a magnet roll fixedly supported. An intensively magnetized block, shaped like U in cross section, is buried in the magnet roll at a location thereof where the magnet roll faces the latent electrostatic image bearing member. In this case, one side of the intensively magnetized block having a groove formed therein is directed toward the axis of the magnet roll, while the other side thereof is flush with the outer surface of the magnet roll. A material of the intensively magnetized block is more intensively magnetized, by its nature, than a material of the magnet roll. The intensively magnetized block is magnetized to form a single magnetic pole or a developing magnetic pole.

Developing unit

In a method of developing a electrostatic charge pattern in which a magnetic brush is formed by supplying a developer consisting of a magnetic carrier and a magnetic toner onto a non-magnetic sleeve disposed so as to face an image carrier surface and incorporating a magnetic field producing member, the magnetic toner contains 25 to 60% by weight of a magnetic powder and the coercive force of the magnetic toner is not greater than 60 Oe. Preferably, the coercive force of the magnetic toner is not smaller than 15 Oe. The magnetic toner is composed, of, for example, styrene.sub.n -butylacrylate copolymer, magnetite and a charge control agent.

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Gunma, Japan

Ryuji Gotoh