Gm Global Technolgoy Operations, Inc.

David E Gay

Robert W Ward

Jon C Shain

Howard H-d Lee

Method of making pole segment for a Lundell-type AC generator rotor from a mixture of ferromagnetic particles and a fugitive binder where the teeth of the rotor are molded concurrently with the base of the rotor but from a mixture of particles which is different from the mixture used to mold the base. Thereafter the segment is fired to remove the binder and sinter the metal particles together.

AC generator rotor segment

Moldable ferromagnetic particles and method of making a magnetizable molding therefrom. The ferromagnetic particles are spray-coated with a slurry comprising insoluble thermoplastic particles suspended in a solution of a soluble polymer to produce a coating on the ferromagnetic particles which comprises a majority of the insoluble thermoplastic particles embedded in a lesser amount of a binder polymer. When compression molded, the insoluble thermoplastic particles form a continuous matrix for the ferromagnetic particles.

Moldable ferromagnetic particles and method

A mass of ferromagnetic particles having a lubricous shell comprising a plurality of organic lubricant particles embedded in a film of a thermoplastic binder.

Lubricous encapsulated ferromagnetic particles

End segments of a Lundell-type rotor for an AC generator, wherein the base and the teeth portions thereof are compaction molded separately and subsequently joined together and sintered.

Method of making an AC generator rotor segment

A method for stress relieving a compression molded magnetic body is provided for purposes of enhancing the magnetic permeability of the magnetic body. The method involves encapsulating ferromagnetic particles with a thermoplastic polymer coating selected from the group consisting of polybenzimidazole and polyimides having heat deflection temperatures of at least about 400.degree. C. which are capable of withstanding elevated temperatures for a duration which is sufficient to anneal the magnetic body formed from the coated metal particles. As a result, the stresses induced in the magnetic core by the compression molding process can be relieved without detriment to the mechanical properties and magnetic characteristics of the magnetic core.

Annealed polymer-bonded soft magnetic body

A mass of ferromagnetic particles moldable into stable, high strength, magnetic cores useful in thermally and chemically hostile environments comprising an iron core and a continuous layer of polyetherimide, polyethersulfone or polyamideimide spray coated onto the surface of each particle. A method of preheating and molding the particles is disclosed.

Composite iron material

A compression molded soft magnetic core comprising annealed soft ferromagnetic metal particles bonded together in a thermoplastic polymer matrix having a heat deflection temperature greater than about 400.degree. C. and selected from the group consisting of polybenzimidazole and polyimides.

A polymeric coating material is provided for coating powdered materials, and more particularly, for coating powdered metals which are compression molded to form magnetic cores. The preferred polymeric materials are polybenzimidazole, an aromatic polyamide such as polyphthalamide, and appropriate polyimides which, when properly applied to metal particles to form a magnetic core, are characterized as having a sufficiently high heat deflection temperature of at least about 270.degree. C., so as to prevent the degradation of the mechanical and magnetic properties of the magnetic core at exposure at elevated temperatures. Each of these preferred coating materials is characterized by excellent mechanical properties, chemical resistance and dielectric characteristics within this temperature range.

Encapsulated ferromagnetic particles suitable for high temperature use

Method of distributing and retaining insoluble additive particles uniformly throughout a mass of moldable metal particles. The additive particles are suspended in a solution of a polymeric binder and spray-coated onto the metal particles. When the solvent evaporates, the additives remain glued to the metal particles by the binder.

Method of adding particulate additives to metal particles

Oxidation-resistant, individually encapsulated neodymium-iron-boron permanent magnet particles are provided. The particles are individually coated with, preferably, three distinct organic layers and are useful for the subsequent formation of a molded permanent magnet article. The first coating is an antioxidant layer employed for the retardation of oxidation of the coated particle. The second intermediate layer consists of an appropriate thermosetting epoxy to provide the adhesion required during subsequent molding of the particles. The third and outermost layer consists of polystyrene and is employed to keep the particles free flowing, since the epoxy layer may be tacky after deposition, thereby hindering the free flowability of the particles. The coatings are applied sequentially using fluidized bed coating techniques. The encapsulated particles can then be molded and appropriately cured. In addition, the encapsulated particles exhibit enhanced oxidation resistance, including at elevated temperatures.

Encapsulated oxidation-resistant iron-neodymium-boron permanent magnet

A polymeric coating material is provided for coating powdered materials and, more particularly, for coating powdered metals formed into parts and sintered, such as to form magnetic cores. The thermoplastic material is polyphenylene oxide which, when properly applied to metal particles to form a magnetic core, is characterized by being sufficiently volatile so as to prevent the formation of contaminants or voids within the sintered article which would be detrimental to the physical properties of the sintered article. Moreover, polyphenylene oxide provides sufficient lubrication and adhesion between adjacent metal particles during an initial compaction process so as to sustain the desired shape of the molded article and maximize metal particle density without the use of additional lubricants, thereby preventing the formation of additional contaminants and/or voids within the resultant sintered article from these lubricants.

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Noblesville, IN, United States of America

David E Gay