Patents by Inventor Sei Kakinuma

Sei Kakinuma has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Semiconductor magnetoresistance device, making method and magnetic sensor
    Patent number: 6335675
    Abstract: A semiconductor magnetoresistance device having plural pairs of opposed short-circuiting electrodes (13) on the opposed surfaces of a semiconductor magneto-sensitive layer (12) shows a great resistance change relative to a magnetic flux density.
    Type: Grant
    Filed: March 17, 2000
    Date of Patent: January 1, 2002
    Assignee: TDK Corporation
    Inventors: Sei Kakinuma, Masaichi Miyano, Katsuya Iwai
  • BALUN transformer core material, BALUN transformer core and BALUN transformer
    Patent number: 6114940
    Abstract: There is disclosed a BALUN transformer core material which has no magnetic permeability, contains a non-magnetic material and is not influenced by the frequency property of the magnetic permeability even in a high-frequency band. A BALUN transformer core which is obtained by pressing and sintering the BALUN transformer core material has no magnetic permeability and has a high specific resistance. A BALUN transformer which is obtained by applying a winding to the BALUN transformer core is a high-property BALUN transformer which can be operated in a high-frequency band of 600 MHz or more.
    Type: Grant
    Filed: June 10, 1998
    Date of Patent: September 5, 2000
    Assignee: TDK Corporation
    Inventors: Sei Kakinuma, Kouki Sato, Masahiro Onizuka, Ko Ito
  • Core for inductance elements and its production method
    Patent number: 5966065
    Abstract: A core for inductance elements is formed of a sintered body of .alpha.-ferric oxide. The core has a flexural strength of at least 6 kgf/mm.sup.2 as measured by a three-point bending method, a specific resistance of at least 10.sup.6 .OMEGA..multidot.cm, a Vickers hardness of 800 to 1,500, and an iron content of 75 to 99.9 wt %, calculated as Fe.sub.2 O.sub.3. The core is produced by granulating, and forming a ferric iron powder, and holding a formed body for sintering at 950 to 1,500.degree. C. for 5 min. to 5 hours in an atmospheric environment.
    Type: Grant
    Filed: June 20, 1997
    Date of Patent: October 12, 1999
    Assignee: TDK Corporation
    Inventors: Masahiro Onizuka, Koh Itoh, Sei Kakinuma
  • Ferrite magnetic material, and ferrite core
    Patent number: 5906768
    Abstract: A ferrite core of the invention is useful for reducing the power loss of Ni--Cu--Zn ferrites, and so for particle accelerators, and power transformers. This core comprises a ferrite magnetic material containing as major components 47 to 50 mol % of iron oxide calculated as Fe.sub.2 O.sub.3, 10 to 25 mol % of nickel oxide calculated as NiO, 2 to 15 mol % of copper oxide calculated as CuO and 15 to 35 mol % of zinc oxide calculated as ZnO, and further containing as subordinate components 0.05 to 1.5 wt % of cobalt oxide calculated as CoO, 0.05 to 0.8 wt % of tungsten oxide calculated as WO.sub.3 and 0.03 to 0.5 wt % of bismuth oxide calculated as Bi.sub.2 O.sub.3, all based on the major components. Consequently, there is achieved a ferrite core having a power loss at 100.degree. C. of up to 210 kW/m.sup.3, and a power loss at 25.degree. C. of up to 140 kW/m.sup.3, as measured at f.multidot.Bm product=25 kTHz (f=1 to 10 MHz).
    Type: Grant
    Filed: April 4, 1997
    Date of Patent: May 25, 1999
    Assignee: TDK Corporation
    Inventors: Sei Kakinuma, Yutaka Saito, Kensuke Ara