Patents by Inventor Hirofumi Hojo

Hirofumi Hojo 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).

  • Patent number: 10923257
    Abstract: The present invention pertains to: a powder mixture for powder magnetic core obtained by mixing a lubricant, a solid lubricant, and a soft magnetic powder coated with an insulating coating, wherein a lubricant content is 0.1% by mass or more and 0.8% by mass and a solid lubricant content is 0.01% by mass or more and 0.2% by mass or less; and a powder magnetic core in which the powder mixture is used.
    Type: Grant
    Filed: April 27, 2016
    Date of Patent: February 16, 2021
    Assignee: Kobe Steel, Ltd.
    Inventors: Hiroyuki Mitani, Hirofumi Hojo, Yuji Taniguchi, Satomi Sato
  • Patent number: 10256019
    Abstract: An iron-based soft magnetic powder for dust core having a high magnetic flux density, maintaining high electric insulation even after annealing, and more excellent in the mechanical strength in which a coating film having a phosphate conversion coating film is formed on the surface thereof and the peak height for the absorption of hydroxyl groups formed at 3700 cm?1 to 2500 cm?1 is 0.04 or more being indicated by absorbance when the coating film is analyzed by infrared diffuse reflectance spectroscopy.
    Type: Grant
    Filed: August 5, 2015
    Date of Patent: April 9, 2019
    Assignee: KOBE STEEL, LTD.
    Inventors: Takeshi Ohwaki, Hiroyuki Mitani, Hirofumi Hojo, Kasumi Yanagisawa, Nobuaki Akagi
  • Publication number: 20180182520
    Abstract: The present invention pertains to: a powder mixture for powder magnetic core obtained by mixing a lubricant, a solid lubricant, and a soft magnetic powder coated with an insulating coating, wherein a lubricant content is 0.1% by mass or more and 0.8% by mass and a solid lubricant content is 0.01% by mass or more and 0.2% by mass or less; and a powder magnetic core in which the powder mixture is used.
    Type: Application
    Filed: April 27, 2016
    Publication date: June 28, 2018
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Hiroyuki MITANI, Hirofumi HOJO, Yuji TANIGUCHI, Satomi SATO
  • Patent number: 9922758
    Abstract: A powder for a powder magnetic core, being composed of iron-base soft magnetic powder particles which each have a phosphoric acid-based chemical conversion coating on the surface. In this powder, the maximum thickness of the phosphoric acid-based chemical conversion coating is 20 to 200 nm, and recessed portions are formed on the surface of the chemical conversion coating with the total area of openings of the recessed portions being 0.5 to 50% by area relative to the total area of the observation visual fields, as determined by observing ten or more parts of the surface of the phosphoric acid-based chemical conversion coating through a scanning electron microscope with a magnification of 10000× or more.
    Type: Grant
    Filed: July 9, 2013
    Date of Patent: March 20, 2018
    Assignee: Kobe Steel, Ltd.
    Inventors: Wataru Urushihara, Mikako Takeda, Mamoru Hosokawa, Hirofumi Hojo, Tomotsuna Kamijo
  • Patent number: 9589712
    Abstract: Disclosed is an iron-based soft magnetic powder obtained by preparing an iron-oxide-based soft magnetic powder through water atomization, and thermally reducing the iron-oxide-based soft magnetic powder. The iron-based soft magnetic powder has an average particle size of 100 ?m or more and has an interface density of more than 0 ?m?1 and less than or equal to 2.6×10?2 ?m?1, where the interface density is determined from a cross-sectional area (?m2) and a cross-sectional circumference (?m) of the iron-based soft magnetic powder. The iron-based soft magnetic powder obtained by preparing an iron-oxide-based soft magnetic powder through water atomization and thermally reducing the iron-oxide-based soft magnetic powder, when used for the production of a dust core, can give a dust core having a low coercive force. Also disclosed is a duct core having a low coercive force and exhibiting superior magnetic properties.
    Type: Grant
    Filed: December 10, 2012
    Date of Patent: March 7, 2017
    Assignee: Kobe Steel, Ltd.
    Inventors: Takeo Miyamura, Hiroyuki Mitani, Hirofumi Hojo
  • Patent number: 9583261
    Abstract: A powder magnetic core which exhibits a high compact density and a reduced iron loss can be obtained by compacting a soft magnetic powder in which the mass ratio of soft magnetic powder particles that pass through a filter having an opening of 75 ?m is 95 mass % or higher relative to the whole amount of the soft magnetic powder and which has a mean strain of less than 0.100%.
    Type: Grant
    Filed: August 26, 2013
    Date of Patent: February 28, 2017
    Assignee: Kobe Steel, Ltd.
    Inventors: Hiroyuki Mitani, Takeo Miyamura, Hirofumi Hojo, Tomotsuna Kamijo
  • Patent number: 9472328
    Abstract: Disclosed is an iron-based soft magnetic powder for dust core use, which includes an iron-based soft magnetic matrix powder and a phosphate conversion coating on a surface of the matrix powder. The phosphate conversion coating contains nickel element and has an aluminum content of equal to or less than that in the matrix powder. The iron-based soft magnetic powder has such excellent heat resistance as to maintain electrical insulation at satisfactory level even after subjected to a high-temperature heat treatment.
    Type: Grant
    Filed: June 15, 2012
    Date of Patent: October 18, 2016
    Assignee: Kobe Steel, Ltd.
    Inventors: Mamoru Hosokawa, Wataru Urushihara, Takeshi Ohwaki, Tomotsuna Kamijo, Hirofumi Hojo
  • Patent number: 9275779
    Abstract: Provided is an iron-based soft magnetic powder for dust core having a less coercive force, which is obtained by specifying the amount of inclusions in the iron-based powder for dust core, and at the same time, capable of decreasing the coercive force of a dust core produced using the iron-based soft magnetic powder. The iron-based soft magnetic powder for dust core is characterized by that when the cross-section of the iron-based soft magnetic powder particle is observed with a scanning electron microscope, the number of inclusions having an equivalent circle diameter from 0.1 to 3 ?m is 1×104 pieces/mm2 or less and the number of inclusions having an equivalent circle diameter exceeding 3 ?m is 10 pieces/mm2 or less.
    Type: Grant
    Filed: November 29, 2011
    Date of Patent: March 1, 2016
    Assignee: Kobe Steel, Ltd.
    Inventors: Hirofumi Hojo, Masamichi Chiba, Hiroyuki Mitani, Nobuaki Akagi, Tomotsuna Kamijo
  • Publication number: 20150340138
    Abstract: An iron-based soft magnetic powder for dust core having a high magnetic flux density, maintaining high electric insulation even after annealing, and more excellent in the mechanical strength in which a coating film having a phosphate conversion coating film is formed on the surface thereof and the peak height for the absorption of hydroxyl groups formed at 3700 cm?1 to 2500 cm?1 is 0.04 or more being indicated by absorbance when the coating film is analyzed by infrared diffuse reflectance spectroscopy.
    Type: Application
    Filed: August 5, 2015
    Publication date: November 26, 2015
    Applicant: KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.)
    Inventors: Takeshi OHWAKI, Hiroyuki MITANI, Hirofumi HOJO, Kasumi YANAGISAWA, Nobuaki AKAGI
  • Publication number: 20150228387
    Abstract: A powder for a powder magnetic core, being composed of iron-base soft magnetic powder particles which each have a phosphoric acid-based chemical conversion coating on the surface. In this powder, the maximum thickness of the phosphoric acid-based chemical conversion coating is 20 to 200 nm, and recessed portions are formed on the surface of the chemical conversion coating with the total area of openings of the recessed portions being 0.5 to 50% by area relative to the total area of the observation visual fields, as determined by observing ten or more parts of the surface of the phosphoric acid-based chemical conversion coating through a scanning electron microscope with a magnification of 10000× or more.
    Type: Application
    Filed: July 9, 2013
    Publication date: August 13, 2015
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Wataru Urushihara, Mikako Takeda, Mamoru Hosokawa, Hirofumi Hojo, Tomotsuna Kamijo
  • Publication number: 20150187493
    Abstract: A powder magnetic core which exhibits a high compact density and a reduced iron loss can be obtained by compacting a soft magnetic powder in which the mass ratio of soft magnetic powder particles that pass through a filter having an opening of 75 ?m is 95 mass % or higher relative to the whole amount of the soft magnetic powder and which has a mean strain of less than 0.100%.
    Type: Application
    Filed: August 26, 2013
    Publication date: July 2, 2015
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Hiroyuki Mitani, Takeo Miyamura, Hirofumi Hojo, Tomotsuna Kamijo
  • Patent number: 9071118
    Abstract: An axial motor includes a rotor arranged between a pair of stators with coils. In the rotor, a plurality of permanent magnets sandwiched between pairs of first magnetic materials and a plurality of second magnetic materials are alternately arranged in a rotation direction while gaps are provided therebetween. Since the permanent magnets are sandwiched by the first magnetic materials in the thus constructed axial motor, a field-weakening control can be performed. Since the second magnetic materials are provided, a reluctance torque can be generated. Further, since the gaps are provided, more magnetic fluxes generated from the permanent magnets can be caused to flow toward the coils. Therefore, the thus constructed axial motor can achieve a higher output, higher torque, higher efficiency, and miniaturization.
    Type: Grant
    Filed: June 17, 2010
    Date of Patent: June 30, 2015
    Assignees: NATIONAL UNIVERSITY CORPORATION HOKKAIDO UNIVERSITY, KABUSHIKI KAISHA KOBE SEIKO SHO
    Inventors: Masatsugu Takemoto, Hiroyuki Mitani, Hirofumi Hojo, Koji Inoue, Osamu Ozaki
  • Publication number: 20140183402
    Abstract: Disclosed is an iron-based soft magnetic powder for dust core use, which includes an iron-based soft magnetic matrix powder and a phosphate conversion coating on a surface of the matrix powder. The phosphate conversion coating contains nickel element and has an aluminum content of equal to or less than that in the matrix powder. The iron-based soft magnetic powder has such excellent heat resistance as to maintain electrical insulation at satisfactory level even after subjected to a high-temperature heat treatment.
    Type: Application
    Filed: June 15, 2012
    Publication date: July 3, 2014
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Mamoru Hosokawa, Wataru Urushihara, Takeshi Ohwaki, Tomotsuna Kamijo, Hirofumi Hojo
  • Publication number: 20140002219
    Abstract: This invention addresses the problem of providing an iron base soft magnetic powder for a powder magnetic core that does not use rare metals, that can maintain the electrical insulating properties between the iron powder particles even when subjected to high temperature thermal processing, and that has excellent thermal stability and mechanical strength. This invention also addresses the problem of providing a fabrication method for the iron base soft magnetic powder for the powder magnetic core, and providing the powder magnetic core. In this iron base soft magnetic powder for the powder magnetic core, a phosphatized coating film is formed on the surface of the iron base soft magnetic powder, and a silicon resin coating film is formed on the surface of the phosphatized coating film. The phosphatized coating film contains P, B, Mg, and Al.
    Type: Application
    Filed: March 11, 2011
    Publication date: January 2, 2014
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Hiroyuki Mitani, Takeshi Ohwaki, Hirofumi Hojo, Satoshi Nishida, Yuji Taniguchi
  • Patent number: 8614617
    Abstract: Provided is a reactor that enables high inductance to be generated with stability in a wide current range, while minimizing noise, processing cost, and eddy-current loss. The reactor (D1) has the ratio (t/W) of the width (W) to the thickness (t) of a conductive member that composes an air-core coil configured to be 1 or less, and preferably, 1/10 or less. Furthermore, the reactor also has the absolute value of a value ((L1?L2)/L3) that has had: the difference (L1?L2) between; the space interval (L1) between an inner wall face of a first core member (3) and an inner wall face of a second core member (4), at the innermost circumference position of the air-core coil (1); and the space (L2) between the inner wall face of the first core member (3) and the inner wall face of the second core member (4), at the outermost circumference position of the air-core coil (1); divided by an average value (L3); configured to be 1/50 or less.
    Type: Grant
    Filed: July 16, 2010
    Date of Patent: December 24, 2013
    Assignee: Kobe Steel, Ltd.
    Inventors: Hiroyuki Mitani, Kyoji Zaitsu, Kenichi Inoue, Osamu Ozaki, Hiroshi Hashimoto, Hirofumi Hojo, Koji Inoue, Eiichiro Yoshikawa, Naoya Fujiwara
  • Patent number: 8323422
    Abstract: Provided is a dust core excellent in flux density, iron loss, and mechanical strength. A production process of a dust core according to the invention includes a step of compacting a mixture obtained by mixing an iron-based soft magnetic powder for powder compact having a phosphate conversion coating film on the surface of an iron-based soft magnetic powder with a lubricant to obtain a powder compact, a heat treatment step of heating the resulting powder compact at 550° C. or more but not more than 650° C. in an inert atmosphere, and a heat treatment step of heating the heat-treated powder compact at 420° C. or more but not more than 530° C. in an oxidizing atmosphere.
    Type: Grant
    Filed: November 22, 2011
    Date of Patent: December 4, 2012
    Assignee: Kobe Steel, Ltd.
    Inventors: Takeshi Ohwaki, Hiroyuki Mitani, Hirofumi Hojo, Tomotsuna Kamijo
  • Publication number: 20120286909
    Abstract: A method produces a dust core by molding a mixture through compression molding to give a powder compact, the mixture containing an oxygen-source-releasable compound and an iron-based soft magnetic powder for powder compacts including an iron-based soft magnetic matrix powder and an insulating coating film present on the surface of the matrix powder; and heating the powder compact to oxidize at least the surface of the iron-based soft magnetic matrix powder by the action of the oxygen-source-releasable compound. The resulting dust core excels not only in mechanical strength but also in resistivity (insulation).
    Type: Application
    Filed: March 30, 2012
    Publication date: November 15, 2012
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Takeshi OHWAKI, Hiroyuki Mitani, Hirofumi Hojo, Tomotsuna Kamijo, Akihiko Tatsumi, Wataru Urushihara, Mikako Takeda, Mamoru Hosokawa
  • Publication number: 20120164453
    Abstract: Provided is an iron-based soft magnetic powder for dust core having a less coercive force, which is obtained by specifying the amount of inclusions in the iron-based powder for dust core, and at the same time, capable of decreasing the coercive force of a dust core produced using the iron-based soft magnetic powder. The iron-based soft magnetic powder for dust core is characterized by that when the cross-section of the iron-based soft magnetic powder particle is observed with a scanning electron microscope, the number of inclusions having an equivalent circle diameter from 0.1 to 3 ?m is 1×104 pieces/mm2 or less and the number of inclusions having an equivalent circle diameter exceeding 3 ?m is 10 pieces/mm2 or less.
    Type: Application
    Filed: November 29, 2011
    Publication date: June 28, 2012
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Hirofumi HOJO, Masamichi Chiba, Hiroyuki Mitani, Nobuaki Akagi, Tomotsuna Kamijo
  • Publication number: 20120154083
    Abstract: Provided is a dust core excellent in flux density, iron loss, and mechanical strength. A production process of a dust core according to the invention includes a step of compacting a mixture obtained by mixing an iron-based soft magnetic powder for powder compact having a phosphate conversion coating film on the surface of an iron-based soft magnetic powder with a lubricant to obtain a powder compact, a heat treatment step of heating the resulting powder compact at 550° C. or more but not more than 650° C. in an inert atmosphere, and a heat treatment step of heating the heat-treated powder compact at 420° C. or more but not more than 530° C. in an oxidizing atmosphere.
    Type: Application
    Filed: November 22, 2011
    Publication date: June 21, 2012
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Takeshi Ohwaki, Hiroyuki Mitani, Hirofumi Hojo, Tomotsuna Kamijo
  • Publication number: 20120104880
    Abstract: An axial motor includes a rotor arranged between a pair of stators with coils. In the rotor, a plurality of permanent magnets sandwiched between pairs of first magnetic materials and a plurality of second magnetic materials are alternately arranged in a rotation direction while gaps are provided therebetween. Since the permanent magnets are sandwiched by the first magnetic materials in the thus constructed axial motor, a field-weakening control can be performed. Since the second magnetic materials are provided, a reluctance torque can be generated. Further, since the gaps are provided, more magnetic fluxes generated from the permanent magnets can be caused to flow toward the coils. Therefore, the thus constructed axial motor can achieve a higher output, higher torque, higher efficiency, and miniaturization.
    Type: Application
    Filed: June 17, 2010
    Publication date: May 3, 2012
    Applicants: KABUSHIKI KAISHA KOBE SEIKO SHO, NATIL. UNIVERSITY CORPORATION HOKKAIDO UNIVERSITY
    Inventors: Masatsugu Takemoto, Hiroyuki Mitani, Hirofumi Hojo, Koji Inoue, Osamu Ozaki