Minebea Company, Limited

Minebea Mitsumi Inc.

Osamu Yamada

Osamu Kobayashi

Kiyoshi Ito

Fumitoshi Yamashita

Yukio Suzuki

Koji Honda

Shunji Kawasaki

Shiho Ohya

Mayuka Shirai

Akihiro Yamane

A motor includes poles P having a remanence Mr of 0.9 T or more, a coercivity HcJ of 0.80 MA/m or more, and a maximum energy product (BH)of 150 kJ/mor more, which sets a center point Pc of the magnetic poles in a circumferential direction on a rotor outer circumferential surface to a maximum thickness t, wherein when a line connecting the Pc and a rotational axis center Rc is Pc-Rc, a straight line connecting an arbitrary point Px in the circumferential direction on the rotor outer circumferential surface and the Rc is Px-Rc, an apex angle of the lines Pc-Rc and Px-Rc is &#x3b8;, a number of pole pairs is Pn, a circumferential direction magnetic pole end is Pe, and a magnetic pole end biasing distance &#x394;Lof the circumferential direction magnetic pole ends Pe is &#x3b1;&#xd7;t(&#x3b1; is a coefficient).

Inner rotor-type permanent magnet motor with annular magnetic poles

Anisotropic rare earth-iron based resin bonded magnet comprises: [1] a continuous phase including: (1) a spherical SmFeNbased magnetic material covered with epoxy oligomer where its average particle size is 1 to 10 &#x3bc;m, its average aspect ratio ARis 0.8 or more, and mechanical milling is not applied after Sm&#x2014;Fe alloy is nitrided; (2) a linear polymer with active hydrogen group reacting to the oligomer; and (3) additive; and [2] a discontinuous phase being an NdFeB based magnetic material coated with the epoxy oligomer where its average particle size is 50 to 150 &#x3bc;m, and its average aspect ratio ARis 0.65 or more, further satisfying: [3] the air-gap ratio of a granular compound on the phases is 5% or less; and [4] a composition where crosslinking agent with 10 &#x3bc;m or less is adhered on the granular compound is formed at 50 MPa or less.

Anisotropic rare earth-iron based resin bonded magnet

A bead type noise filter according to the present invention is constituted by a magnetic coreformed of Mn&#x2014;Zn ferrite having its resistivity increased so as to improve a high frequency characteristic, and having its permittivity lowered, and thereby can successfully suppress radiation noises without distorting the waveform of transmission signals. The magnetic coreconstituting the bead type noise filter is formed of a high resistivity soft magnetic material, is shaped cylindrical, and has at least one through-holeso as to form a closed magnetic path, and the bead type noise filter is attached on a signal linesuch that the signal lineis inserted through the through-hole. The soft magnetic material has a real part of complex relative permittivity ranging from 1,000 up to 20,000 at 1 kHz and 50 or lower at 1 MHz, and has a resistivity of 150 &#x3a9;m or higher.

Bead type noise filter

An Mn&#x2014;Zn ferrite includes base components of 44.0 to 49.8 mol % FeO, 4.0 to 26.5 mol % ZnO, at least one of 0.1 to 4.0 mol % TiOand SnO, 0.5 mol % or less MnO, and the remainder consisting of MnO, and contains 0.20 (0.20 excluded) to 1.00 mass % CaO as additive. Since the Mn&#x2014;Zn ferrite contains less than 50 mol % FeOand a limited amount (0.5 mol % or less) of MnO, an abnormal grain growth does not occur even if CaO content is more than 0.20 mass %, and a high electrical resistance can be gained. And, since an appropriate amount of TiOand/or SnOis contained, an initial permeability is kept adequately high, whereby an excellent soft magnetism can be achieved in a high frequency band such as 1 MHz.

Mn&#x2014;Zn ferrite containing less than 50 mol% Fe2O3

An Mn&#x2014;Zn ferrite includes base components of 44.0 to 49.8 mol % FeO, 4.0 to 26.5 mol % ZnO, 0.8 mol % or less MnO, and the remainder consisting of MnO, and contains 0.20 (0.20 excluded) to 1.00 mass % CaO as additive. Since the Mn&#x2014;Zn ferrite contains less than 50.0 mol % FeOand a limited amount (0.8 mol % or less) of MnO, an abnormal grain growth does not occur even if CaO content is more than 0.20 mass %, and a high electrical resistance can be gained thereby realizing an excellent soft magnetism in a high frequency band such as 1 MHz.

[object Object]

In an inductor comprising an open magnetic path formed by a soft magnetic material and a winding provided around the open magnetic path, the soft magnetic material has its relative complex dielectric constant varying according to a frequency. In the soft magnetic material, the imaginary part of the relative complex dielectric constant is greater than the real part thereof in a high-frequency band equal higher than the frequency of the electric signal flowing in the winding. Specifically, the soft magnetic material has a resistivity of 150 &OHgr;m, has a real part of the relative complex dielectric constant, ranging from 1,000 to 20,000 at 1 kHz and 50 or less at 1 MHz, and the imaginary part is greater than the real part at 1 MHz.

Inductor

The present invention provides a production process of a Mn&mdash;Zn ferrite that enables wastes of sintered cores to be recycled without serious difficulties in sintering. The production process comprises recycling a powder obtained by milling a sintered Mn&mdash;Zn ferrite, thereby obtaining a sintered core having a component composition including 44.0 to 49.8 mol % Fe O , 4.0 to 26.5 mol % ZnO, 1.0 to 3.0 mol % CoO, 0.02 to 1.00 mol % Mn O and a remainder MnO.

Production process of MN-Zn ferrite

A production process of a Mn&mdash;Zn ferrite enables wastes of sintered cores to be recycled without serious difficulties in sintering. The production process includes recycling a powder obtained by milling a sintered Mn&mdash;Zn ferrite, thereby obtaining a sintered core having a component composition including 44.0 to 49.8 mol % Fe O , 4.0 to 26.5 mol % ZnO, 0.02 to 1.00 mol % Mn O and a remainder MnO.

Production process of Mn-Zn ferrite

The present invention provides a Mn&mdash;Zn ferrite having an electrical resistivity exceeding 1 &OHgr;m order and having a high initial permeability of 3000 or more at 100 kHz and 100 or more at 10 MHz. The main components of the Mn&mdash;Zn ferrite are 44.0 to 49.8 mol % Fe O , 15.0 to 26.5 mol % ZnO, 0.02 to 1.00 mol % Mn O and the remainder MnO. The Mn&mdash;Zn ferrite is enabled to be used in a wide frequency region from 100 kHz to 10 MHz by limiting Fe O content to less than 50 mol % that is the stoichiometric composition and inhibiting formation of Mn O .

Mn-Zn ferrite and production process thereof

The present invention provides a Mn&mdash;Zn ferrite having an electrical resistivity exceeding 1 &OHgr;m order and a low core loss in a high frequency region exceeding 1 MHz. A basic component composition of the Mn&mdash;Zn ferrite includes 44.0 to 49.8 mol % of Fe O , 6.0 to 15.0 mol % of ZnO (15.0 mol % is excluded), 0.1 to 3.0 mol % of CoO, 0.02 to 1.20 mol % of Mn O , and the remainder of MnO. The Mn&mdash;Zn ferrite achieves desired purposes by controlling Fe O content to a range less than 50 mol % that is the stoichiometric composition, adding a proper amount of CoO, restraining amount of Mn O formation to 1.20 mol % or less, and further setting their average grain sizes to less than 10 &mgr;m.

The present invention provides a Mn&mdash;Zn ferrite having an electrical resistivity exceeding 1 &OHgr;m order and having a low core loss in a high frequency region exceeding 1 MHz. The basic component composition of the Mn&mdash;Zn ferrite includes 44.0 to 49.8 mol % Fe O , 6.0 to 15.0 mol % ZnO (15.0 mol % is excluded), 0.1 to 4.0 mol % at least one of TiO and SnO , and remainder MnO, wherein desired results are obtained by limiting Fe O content to less than 50 mol % that is the stoichiometric composition and adding a proper amount of TiO or SnO and further controlling its average grain size to less than 10 &mgr;m.

This invention provides a Mn&mdash;Zn ferrite which has a high electrical resistance and can sufficiently satisfy the use in a high frequency region exceeding 1 MHz. This invention further provides a production process of the Mn&mdash;Zn ferrite in which mixed powder whose components are adjusted so as to have a basic component composition containing 44.0 to 50.0 mol% Fe O , 4.0 to 26.5 mol % ZnO, 0.1 to 8.0 mol % one or two from TiO and SnO and the remainder consisting of MnO, and further to contain 0.01 to 2.00 mass % one or more of CoO, NiO, and MgO as additive is pressed, then sintered and cooled in the air or in an atmosphere containing some amount of oxygen.

The present invention provides a Mn&mdash;Zn ferrite having an electrical resistivity exceeding 1 &OHgr;m order and having a high initial permeability of 4000 or more at 100 kHz and 100 or more at 10 MHz. The main components of the Mn&mdash;Zn ferrite include 44.0 to 49.8 mol % Fe O , 15.0 to 26.5 mol % ZnO, 0.1 to 3.0 mol % CoO, 0.02 to 1.00 mol % Mn O , and the remainder MnO. The Mn&mdash;Zn ferrite can be used in a wide frequency region of 100 kHz to 10 MHz by limiting Fe O content to a range of less than 50 mol %, that is the stoichiometric composition, inhibiting formation of Mn O and adding a proper amount of CoO.

A process for producing Mn&mdash;Zn ferrite having large electrical resistance and being durable to the use in high frequency region exceeding 1 MHz easily and at low cost is disclosed. The process comprises pressing a mixed powder comprising a composition of 44.0 to 50.0 mol % of Fe O , 4.0 to 26.5 mol % of ZnO, 0.1 to 8.0 mol % of at least one member selected from the group consisting of TiO and SnO , and the remainder being MnO, and if desired 0.1 to 16.0 mol % of CuO, sintering the resulting green compact in the air or an atmosphere containing an appropriate amount of oxygen, and then cooling the green compact, thereby securing the estimated high initial permeability even in a high frequency region of 1 MHz or more.

Process for producing Mn-Zn ferrite

A process for producing Mn&mdash;Zn ferrite is disclosed, which enables regeneration and reuse of scraps of a sintered product. The process comprises reusing a powder obtained by milling the sintered product of Mn&mdash;Zn ferrite, subjecting the powder to a component adjustment so as to have a composition of 44.0 to 50.0 mol % of Fe,O,, 4.0 to 26.5 mol % of ZnO, 0.1 to 8.0 mol % of at least one member selected from the group consisting of TiO,and SnO,, and the remainder being MnO, and optionally 0.1 to 16.0 mol % of CuO, pressing the resulting mixed powder after the component adjustment, and then sintered a green compact.

Growing community of inventors

Iwata-gun, Japan

Osamu Yamada