Minebea Company, Limited

Kiyoshi Ito

Osamu Kobayashi

Osamu Yamada

Yukio Suzuki

Masashi Norizuki

Mayuka Shirai

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 electromagnetic wave absorber is formed of an Mn&#x2014;Zn ferrite including: a spinel primary phase which contains 40.0 to 49.9 mol % FeO, 4.0 to 26.5 mol % ZnO, and the remainder consisting of MnO; and a secondary phase which contains CaO as a base component. In the ferrite, the spinel primary phase accounts for 50.0 to 99.0% of the aggregate mass of the spinel primary phase and the secondary phase.

Electromagnetic wave absorber formed of Mn-Zn ferrite

An electromagnetic wave absorber is formed of an Mn&#x2014;Zn ferrite including: a spinel primary phase which contains 40.0 to 49.9 mol % FeO, 4.0 to 26.5 mol % ZnO, 0.1 to 4.0 mol % TiOand/or SnO, and the remainder consisting of MnO; and a secondary phase which contains CaO as a base component. In the ferrite, the mass of the spinel primary phase accounts for 50.0 to 99.0% of the aggregate mass of the spinel primary phase and the secondary phase.

A Mn&#x2014;Zn ferrite and a coil component are provided which obtains a low core loss in a frequency band above 1 MHz and even above 5 MHz and which can duly function in such a high frequency band. The Mn&#x2014;Zn contains as basic components 44.00 to 50.0 mol % Fe2O3 (50 mol % excluded), 4.0 to 26.5 mol % ZnO, and remainder MnO, and has a dielectric loss tan &#x3b4; of 0.3 or less at 1 kHz, and a complex relative permittivity &#x3b5; of 1,000 or less at 1 MHz, whereby a core loss decreases in the high frequency band.

Mn-Zn ferrite and coil component with magnetic core made of same

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 Mn&mdash;Zn ferrite of the present invention contains basic components of 44.0 to 50.0 mol % (50.0 mol % is excluded) Fe O , 4.0 to 26.5 mol % ZnO and the remainder MnO, and has a real part &egr;&prime; of complex relative permittivity of 20,000 or less at 1 kHz and 50 or less at 1 MHz, thereby maintaining initial permeability in a wide frequency band, showing a low stray capacitance with a coil provided, and ensuring an excellent impedance in a wide frequency band. And a coil using the Mn&mdash;Zn ferrite as a magnetic core is also provided.

Mn-Zn ferrite and coil component using same

A common mode choke coil is described that is capable of providing improved characteristics at high frequencies. A bobbin having a toroidal core is mounted on a base. One coil is wound around one half of the bobbin and another coil is wound around the other half thereof. Both ends of each of the coils are connected to corresponding terminals provided on the base. The one coil has its one end connected to one of the terminals, is wound around one half of the bobbin from one side of the bobbin, finishes above the bobbin, that is, at the inner circumference of a core, leads out toward the other terminal provided on the base travelling along the outer face of a plate vertically mounted on the other side of the bobbin, and is connected to the terminal. The same applies to the other coil.

Common mode choke coil

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.

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Iwata-gun, Japan

Kiyoshi Ito