Hitachi Metals, Ltd.

Kazunori Tabaru

Katsunori Iwasaki

Motoharu Shimizu

Toshio Kumakura

Michihisa Shimizu

Takafumi Aoyama

Noriyuki Noda

The magnet powder-resin compound particles substantially composed of rare earth magnet powder and a binder resin are in such a round shape that a ratio of the longitudinal size a to the transverse size b (a/b) is more than 1.00 and 3 or less, and that an average particle size defined by (a/b)/2 is 50-300 &#x3bc;m. They are produced by charging a mixture of rare earth magnet powder and a binder resin into an extruder equipped with nozzle orifices each having a diameter of 300 &#x3bc;m or less; extruding the mixture while blending under pressure though the nozzle orifices to form substantially cylindrical, fine pellets; and rounding the pellets by rotation.

Magnet powder-resin compound particles, method for producing such compound particles and resin-bonded rare earth magnets formed therefrom

The magnet powder-resin compound particles substantially composed of rare earth magnet powder and a binder resin are in such a round shape that a ratio of the longitudinal size a to the transverse size b (a/b) is more than 1.00 and 3 or less, and that an average particle size defined by (a/b)/2 is 50-300 &mgr;m. They are produced by charging a mixture of rare earth magnet powder and a binder resin into an extruder equipped with nozzle orifices each having a diameter of 300 &mgr;m or less; extruding the mixture while blending under pressure though the nozzle orifices to form substantially cylindrical, fine pellets; and rounding the pellets by rotation.

Anisotropic rare-earth permanent magnets characterized in that an aggregate of a plurality of blocks, to each of which anisotropy is imparted, is formed using powders of magnetic material containing rare-earth elements, and the adjoining blocks are powder-metallurgically bonded together under pressure into one piece; a method of making anisotropic rare-earth permanent magnets by molding anisotropic blocks by magnetic-field molding, arranging, aggregating and sealing a plurality of blocks in a bag, and cold hydrostatic pressing the aggregate of blocks in the absence of magnetic field; and a suitable metal mold for magnetic-field molding anisotropic permanent magnets of a relatively large size.

Anisotropic rare-earth permanent magnets and method for making same, and

There is disclosed a rare earth permanent magnet composed of a sintered product consisting of R and M where R represents at least one rare earth, and M represents Co or a combination of Co and at least one kind selected from the group consisting of Fe, Ni and Cu, the sintered product being of such a composition that a RM.sub.5 phase and a R.sub.2 M.sub.7 phase occur in the sintered product. The sintered product contains 63 to 65 wt. % of M, and the sintered product has a coercive force iHc of not less than 13,000 Oe. The permanent magnet can have a disk-shape, a ring-shape or a cylindrical shape. A method of heat treatment of the permanent magnet is also disclosed.

Rare earth permanent magnet, method of heat treatment of same, and

A highly oriented rare earth based permanent magnet satisfies the relationship a.gtoreq.b&gt;c where a is the longer side or major axis of the magnet, b is the shorter or minor axis of the magnet, and c is the thickness of the magnet, and that has a flat shape which is magnetized in the direction of thickness c, with the direction of magnetization being inclined at an angle of no more than 3 degrees with respect to the line normal to the plane defined by a and b. The magnet is produced by loading an alloy powder as the starting material into a mold having a cavity that satisfies the relationship A.gtoreq.B&gt;C where A is the longer side or major axis of the cavity, B is the shorter side or minor axis of the cavity, and C is the depth of the cavity; exerting a compressive force of at least 0.4 tons/cm.sup.2 in a direction substantially perpendicular to the plane defined by A and C while applying a magnetic field in a direction substantially perpendicular to the plane defined by A and B, thereby effecting in-field molding so as to obtain a preform; and performing cold isostatic pressing at a pressure higher than that employed in the preforming step.

Highly oriented permanent magnet and process for producing the same

Metal mold for molding anisotropic permanent magnets

The invention involves a method for making one component or single component toner compositions for developing electrophotographic images. A binding component is mixed with magnetic particles, pulverized, then carbon black is mixed with the powder and fixed to the surface of the particles. Compositions having a measured resistivity of 4.3.times.10.sup.3 to 4.3.times.10.sup.6 ohm-cm at a D.C. field of below 20 volts/cm under substantially no-load conditions are selected for use.

Preparation method of magnetic toner

A ferrite magnet and a method of producing same, wherein a mixture of magnetoplumbite type ferrite particles contained as its principal constituent and at least one of a mixing medium, an organic binder and a minute particular additive which is added with water or methyl alcohol is subjected to extrusion compacting to form compacts. The formed compacts are each subjected to at least drying, sintering, orienting and magnetizing, to produce cylindrical ferrite magnets having a plurality of magnetic poles on the surface. To impart anisotropy to the magnets, at least one pulse magnetic field may be applied on the surface of each compact formed by extrusion compacting, and the oriented compact may be magnetized in the same direction as the direction in which the anisotropy has been imparted.

Growing community of inventors

Saitama, Japan

Kazunori Tabaru