Hitachi Metals, Ltd.

Proterial, Ltd.

Satoru Tanaka

Tomoyuki Tada

Norikazu Koyuhara

Takeshi Tachibana

Yasuharu Miyoshi

Hiroki Yamamoto

Keiko Kikuchi

Shiro Murakami

Makoto Kadowaki

Yoshihito Yoshikawa

A coil device comprising a coil, and a ferrite core arranged in a hollow portion of the coil, and a resin covering them; the ferrite core being a Ni ferrite core having initial permeability &#x3bc;i of 450 or more at a frequency of 100 kHz and a temperature of 20&#xb0; C., and an average crystal grain size of 5-9 &#x3bc;m, both of temperature-dependent inductance change ratios TLa and TLb and stress-dependent inductance change ratios PLa and PLb being &#x2212;0.6% to +0.6%, and both of the sum of TLa and PLa and the sum of TLb and PLb being more than &#x2212;1.0% and less than +1.0%; and an antenna comprising it.

Coil device and antenna

A sintered Ni ferrite body having a composition comprising, calculated as oxide, 47.0-48.3% by mol of FeO, 14.5% or more and less than 25% by mol of ZnO, 8.2-10.0% by mol of CuO, and more than 0.6% and 2.5% or less by mol of CoO, the balance being NiO and inevitable impurities, and having an average crystal grain size of more than 2.5 &#x3bc;m and less than 5.5 &#x3bc;m.

Sintered Ni ferrite body, coil device, and method for producing sintered Ni ferrite body

A method for producing a MnZn ferrite core used at a frequency of 1 MHz or more and an exciting magnetic flux density of 75 mT or less, the MnZn ferrite comprising 53-56% by mol of Fe (calculated as FeO), and 3-9% by mol of Zn (calculated as ZnO), the balance being Mn (calculated as MnO), as main components, and 0.05-0.4 parts by mass of Co (calculated as CoO) as a sub-component, per 100 parts by mass in total of the main components (calculated as the oxides); comprising a step of molding a raw material powder for the MnZn ferrite to obtain a green body; a step of sintering the green body and cooling it to a temperature of lower than 150&#xb0; C. to obtain a sintered body of MnZn ferrite; and a step of conducting a heat treatment comprising heating the sintered body of MnZn ferrite to a temperature meeting Condition 1 of 200&#xb0; C. or higher, and Condition 2 of (Tc&#x2212;90)&#xb0; C. to (Tc+100)&#xb0; C., wherein Tc is a Curie temperature (&#xb0; C.) calculated from the percentages by mol of FeOand ZnO contained in the main components of the MnZn ferrite, keeping the sintered body at the above temperature for a predetermined period of time, and then cooling the sintered body from the keeping temperature at a speed of 50&#xb0; C./hour or less.

MnZn ferrite core and its production method

A method for producing MnZn-ferrite comprising Fe, Mn and Zn as main components, and at least Co, Si and Ca as sub-components, the main components in the MnZn-ferrite comprising 53-56% by mol (as FeO) of Fe, and 3-9% by mol (as ZnO) of Zn, the balance being Mn as MnO, comprising the step of sintering a green body to obtain MnZn-ferrite; the sintering comprising a temperature-elevating step, a high-temperature-keeping step, and a cooling step; the high-temperature-keeping step being conducted at a keeping temperature of higher than 1050&#xb0; C. and lower than 1150&#xb0; C. in an atmosphere having an oxygen concentration of 0.4-2% by volume; the oxygen concentration being in a range of 0.001-0.2% by volume during cooling from 900&#xb0; C. to 400&#xb0; C. in the cooling step; and the cooling speed between (Tc+70)&#xb0; C. and 100&#xb0; C. being 50&#xb0; C./hour or more, wherein Tc represents a Curie temperature (&#xb0; C.) calculated from % by mass of FeOand ZnO.

MnZn-ferrite and its production method

A method for analyzing the DC superposition characteristics of an inductance device using an electromagnetic field simulator, comprising a first step of determining an initial magnetization curve from initial magnetization to saturation magnetization, and pluralities of minor loops at different operating points, on a toroidal core made of the same magnetic material as that of the inductance device, and obtaining point-list data showing the relation between magnetic flux density or magnetic field strength and incremental permeability from the incremental permeability at each operating point; a second step of determining an operating point at a predetermined direct current on each element obtained by mesh-dividing an analysis model of the inductance device by an electromagnetic field simulator based on the initial magnetization curve of the core, allocating the incremental permeability to the operating point from the point-list data, and integrating the inductance of each element obtained from the incremental permeability to determine the inductance of the entire inductance device; and a third step of repeating the second step at different direct current levels to determine the DC superposition characteristics.

Method for analyzing DC superposition characteristics of inductance device, and electromagnetic field simulator

A multilayer inductor comprising a coil embedded in a magnetic portion, and a magnetic gap formed by a non-magnetic portion in part of a magnetic path, the magnetic portion being made of Ni ferrite, whose relative temperature coefficient &#x3b1;&#x3bc;of initial permeability at a frequency of 1 MHz is more than +10 ppm/&#xb0; C. and +40 ppm/&#xb0; C. or less between &#x2212;40&#xb0; C. and +80&#xb0; C., the non-magnetic portion being made of Zn ferrite containing more Zn than in the magnetic portion and having a Curie temperature Tc of &#x2212;50&#xb0; C. or lower, and the Zn content changing continuously in boundary regions between the non-magnetic portion and the magnetic portion, whereby the thickness of the magnetic gap changes with the temperature.

Multilayer inductor and power converter comprising it

Low-loss ferrite comprising 100% by mass of main components comprising 47.1-49.3% by mol of FeO, 20-26% by mol of ZnO, and 6-14% by mol of CuO, the balance being NiO, and 0.1-2% by mass (as SnO) of Sn and 0.05-2% by mass (as MnO) of Mn, and having an average crystal grain size of 0.5-3 &#x3bc;m.

Low-loss ferrite and electronic device formed by such ferrite

A low-loss ferrite comprising as main components 46.5-49.5% by mol of FeO, 17-26% by mol of ZnO, 4-12% by mol of CuO, and 0.2% or more and less than 1.2% by mol of CoO, the balance being NiO, and 0.03-1.4% by mass (as SnO) of Sn based on 100% by mass of the main components, and having an average crystal grain size of 0.7-2.5 &#x3bc;m, and an electronic device obtained by integrally sintering pluralities of layers of this low-loss ferrite and coil-shaped electrodes formed in the laminate.

A ferrite core for use in coupling transformers and distributing transformers in CATV equipments such as couplers, distributors and amplifiers, the ferrite core being made of a ferrite having a saturation magnetostriction |&#x3bb;| of 8&#xd7;10or less in an absolute value and an initial permeability &#x3bc;of 300 or more.

Growing community of inventors

Tottori, Japan

Satoru Tanaka