Patents by Inventor Yoshinori Fujikawa

Yoshinori Fujikawa 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).

  • Publication number: 20220199301
    Abstract: To provide an R-T-B based permanent magnet in which the residual magnet flux density and the coercivity are improved. Provided is an R-T-B based permanent magnet including a rare-earth element R, and transition metal elements T and B. The R-T-B based permanent magnet includes at least Nd as R, the R-T-B based permanent magnet includes at least Fe among Fe and Co as T, the R-T-B based permanent magnet includes a plurality of main phase grains containing a crystal of R2T14B, and a two-grain boundary located between two main phase grains adjacent in an axis-of-easy-magnetization direction, the thickness of the two-grain boundary is 3 nm or less, and the two-grain boundary is crystalline, and is non-oriented.
    Type: Application
    Filed: December 17, 2021
    Publication date: June 23, 2022
    Applicant: TDK Corporation
    Inventors: Kenichi SUZUKI, Yoshinori FUJIKAWA
  • Patent number: 11361888
    Abstract: One embodiment of the present invention is that in samarium-iron-nitrogen magnet powder, a non-magnetic phase is formed on a surface of the samarium-iron-nitrogen magnet phase, and an arithmetic mean roughness Ra of the surface is 3.5 nm or less.
    Type: Grant
    Filed: May 29, 2018
    Date of Patent: June 14, 2022
    Assignees: National Institute of Advanced Industrial Science and Technology, TDK Corporation
    Inventors: Shusuke Okada, Kenta Takagi, Yasushi Enokido, Yoshinori Fujikawa, Ryuji Hashimoto
  • Publication number: 20220148772
    Abstract: An R-T-B-based permanent magnet having improved magnetic properties contains R that represents at least one rare earth element essentially including Nd or Pr, T that represents at least one iron-group element essentially including Fe, B that represents boron, and M that represents at least one element selected from Ga, Al, Cu and Si. The R-T-B-based permanent magnet includes main-phase grains which include R2T14B crystals and two-grain grain boundaries each of which exists between adjacent two of the main-phase grains. The average thickness of the two-grain grain boundaries is 5 to 50 nm inclusive. The area ratio of an R6T13M compound in an arbitrary cross section is 0.50% or less (including 0%).
    Type: Application
    Filed: March 10, 2020
    Publication date: May 12, 2022
    Applicant: TDK CORPORATION
    Inventor: Yoshinori FUJIKAWA
  • Patent number: 11152142
    Abstract: An R-T-B based permanent magnet excellent in magnetic properties relatively reduces the amount of a heavy rare earth element used. An R-T-B based permanent magnet, wherein R represents a rare earth element, T an iron group element and B boron, includes main phase grains including an R2T14B crystal phase and grain boundaries formed between main phase grains. Grain boundaries include R—O—C—N concentrated parts where concentrations of R, O, C and N are all higher than those in main phase grains. C/R(S)>C/R(C) is satisfied in which C/R(S) represents a C/R ratio (atomic ratio) in R—O—C—N concentrated parts present in a surface of a R-T-B based permanent magnet and C/R(C) represents a C/R ratio (atomic ratio) in the R—O—C—N concentrated parts present in the center of a R-T-B based permanent magnet, and a heavy rare earth element RH is included in the R-T-B based permanent magnet.
    Type: Grant
    Filed: March 28, 2019
    Date of Patent: October 19, 2021
    Assignee: TDK CORPORATION
    Inventors: Yuki Nagamine, Masashi Miwa, Yoshinori Fujikawa
  • Patent number: 10991493
    Abstract: A rare earth magnet includes main phase grains having an R2T14B type crystal structure. The main phase grains include Ga. A concentration ratio A (A=?Ga/?Ga) of the main phase grains is 1.20 or more, where ?Ga and ?Ga are respectively a highest concentration of Ga and a lowest concentration of Ga in one main phase grain.
    Type: Grant
    Filed: March 25, 2016
    Date of Patent: April 27, 2021
    Assignee: TDK CORPORATION
    Inventors: Wakako Okawa, Syota Goto, Yoshinori Fujikawa
  • Patent number: 10984929
    Abstract: A rare earth magnet includes main phase grains having an R2T14B type crystal structure. The main phase grains include C. A concentration ratio A1 (A1=?C/?C) of the main phase grains is 1.50 or more, where ?C and ?C are respectively a highest concentration of C and a lowest concentration of C in one main phase grain.
    Type: Grant
    Filed: March 25, 2016
    Date of Patent: April 20, 2021
    Assignee: TDK CORPORATION
    Inventors: Wakako Okawa, Syota Goto, Yoshinori Fujikawa
  • Patent number: 10748686
    Abstract: An R-T-B based sintered magnet including a plural number of main phase particles having an R2T14B type crystal structure. R is at least one rare earth element essentially including heavy rare earth elements RH, T is at least one transition metal element essentially including Fe or Fe and Co, and B is boron. At least one of the main phase particles is a reverse core-shell main phase particle including a core part and a shell part, in which CRC/CRS>1.0 is satisfied when a total RH concentration (at %) in the core part is defined as CRC and a total RH concentration (at %) in the shell part is defined as CRS. An existence ratio of the reverse core-shell main phase particles is larger in a surface layer part of the magnet than in a central part of the magnet.
    Type: Grant
    Filed: March 29, 2018
    Date of Patent: August 18, 2020
    Assignee: TDK CORPORATION
    Inventors: Yoshinori Fujikawa, Masashi Miwa
  • Patent number: 10748685
    Abstract: An R-T-B based sintered magnet including main phase particles having an R2T14B type crystal structure. R is at least one rare earth element essentially including a heavy rare-earth element RH. T is at least one transition metal element essentially including Fe or Fe and Co. B is boron. At least one of the main phase particles includes low RH crystal phases inside the main phase particle. The low RH crystal phases include the R2T14B type crystal structure, wherein an RH concentration in the low RH crystal phases is relatively lower than the RH concentration in the whole main phase particles. The R-T-B based sintered magnet may satisfy rs?rc?20% when an existence ratio of the main phase particles including the low RH crystal phases in a magnet surface layer part is rs (%) and the same in a magnet central part is rc (%).
    Type: Grant
    Filed: March 29, 2018
    Date of Patent: August 18, 2020
    Assignee: TDK CORPORATION
    Inventors: Yoshinori Fujikawa, Masashi Miwa
  • Patent number: 10734143
    Abstract: An R-T-B based sintered magnet including a main phase particle comprising an R2T14B type crystal structure. R is at least one rare earth element, T is at least one transition metal element essentially including Fe or Fe and Co, and B is boron. The R-T-B based sintered magnet includes a magnet surface layer part and a magnet central part existing inside the magnet surface layer part. A crystal orientation degree of the main phase particle in the magnet surface layer part having a magnetic pole surface is lower than the crystal orientation degree of the main phase particle in the magnet central part.
    Type: Grant
    Filed: March 29, 2018
    Date of Patent: August 4, 2020
    Assignee: TDK CORPORATION
    Inventors: Yoshinori Fujikawa, Masashi Miwa
  • Patent number: 10726980
    Abstract: A rare earth magnet includes main phase grains having an R2T14B type crystal structure. The main phase grains include B. A concentration ratio A (A=?B/?B) of the main phase grains is 1.05 or more, where ?B and ?B are respectively a highest concentration of B and a lowest concentration of B in one main phase grain.
    Type: Grant
    Filed: March 25, 2016
    Date of Patent: July 28, 2020
    Assignee: TDK CORPORATION
    Inventors: Wakako Okawa, Syota Goto, Yoshinori Fujikawa
  • Publication number: 20200118722
    Abstract: One embodiment of the present invention is that in samarium-iron-nitrogen magnet powder, a non-magnetic phase is formed on a surface of the samarium-iron-nitrogen magnet phase, and an arithmetic mean roughness Ra of the surface is 3.5 nm or less.
    Type: Application
    Filed: May 29, 2018
    Publication date: April 16, 2020
    Applicants: National Institute of Advanced Industrial Science and Technology, TDK Corporation
    Inventors: Shusuke OKADA, Kenta TAKAGI, Yasushi ENOKIDO, Yoshinori FUJIKAWA, Ryuji HASHIMOTO
  • Patent number: 10546672
    Abstract: The present invention provides a rare earth based magnet that inhibits the high temperature demagnetization rate even when less or no heavy rare earth elements such as Dy, Tb and the like are used. The rare earth based magnet according to the present invention includes R2T14B main phase crystal grains and grain boundary phases between adjacent main phase crystal grains. In any cross-section of the rare earth based magnet, when evaluating the circular degree of the main phase crystal grains with Wadell's Roundness A, the shape of the main phase crystal grains is controlled such that the Roundness A becomes 0.24 or more.
    Type: Grant
    Filed: March 28, 2014
    Date of Patent: January 28, 2020
    Assignee: TDK CORPORATION
    Inventors: Eiji Kato, Yoshinori Fujikawa, Taeko Tsubokura, Chikara Ishizaka, Katsuo Sato
  • Patent number: 10453595
    Abstract: A rare earth permanent magnet includes a main phase composed of a main phase particle and a grain boundary present among a plurality of the main phase particles. The grain boundary includes a region whose electric resistance is higher than that of the main phase.
    Type: Grant
    Filed: February 27, 2017
    Date of Patent: October 22, 2019
    Assignee: TDK CORPORATION
    Inventors: Tetsuya Hidaka, Yuki Nagamine, Yoshinori Fujikawa
  • Publication number: 20190304638
    Abstract: An R-T-B based permanent magnet excellent in magnetic properties relatively reduces the amount of a heavy rare earth element used. An R-T-B based permanent magnet, wherein R represents a rare earth element, T an iron group element and B boron, includes main phase grains including an R2T14B crystal phase and grain boundaries formed between main phase grains. Grain boundaries include R-O-C-N concentrated parts where concentrations of R, O, C and N are all higher than those in main phase grains. C/R(S)>C/R(C) is satisfied in which C/R(S) represents a C/R ratio (atomic ratio) in R-O-C-N concentrated parts present in a surface of a R-T-B based permanent magnet and C/R(C) represents a C/R ratio (atomic ratio) in the R-O-C-N concentrated parts present in the center of a R-T-B based permanent magnet, and a heavy rare earth element RH is included in the R-T-B based permanent magnet.
    Type: Application
    Filed: March 28, 2019
    Publication date: October 3, 2019
    Applicant: TDK CORPORATION
    Inventors: Yuki NAGAMINE, Masashi MIWA, Yoshinori FUJIKAWA
  • Publication number: 20190304640
    Abstract: An R-T-B based permanent magnet, excellent in magnetic properties relatively reducing amount of heavy rare earth element used, wherein R represents rare earth element, T iron group element and B boron, includes main phase grains including R2T14B crystal phase and grain boundaries between main phase grains. Grain boundaries include R—O—C—N concentrated parts where concentrations of R, O, C and N are all higher than in main phase grains. O/R(S)>O/R(C) wherein O/R(S) represents O/R ratio (atomic ratio) in R—O—C—N concentrated parts in a surface of an R-T-B based permanent magnet and O/R(C) represents O/R ratio (atomic ratio) in R—O—C—N concentrated parts in a center of an R-T-B based permanent magnet. A heavy rare earth element RH is in a surface of an R-T-B based permanent magnet as R. R—O—C—N concentrated parts in a surface of an R-T-B based permanent magnet have RH/R ratio (atomic ratio) of 0.2 or less.
    Type: Application
    Filed: March 28, 2019
    Publication date: October 3, 2019
    Applicant: TDK CORPORATION
    Inventors: Yuki NAGAMINE, Masashi MIWA, Yoshinori FUJIKAWA
  • Patent number: 10256016
    Abstract: The present invention provides a rare earth based magnet in which the demagnetization rate at a high temperature can be inhibited even if the amount of heavy rare earth element(s) such as Dy and Tb is evidently decreased compared to the past or no such heavy rare earth element is used. The rare earth based magnet of the present invention is a sintered magnet which comprises R2T14B crystal grains as the main phases and the crystal boundary phases among the R2T14B crystal grains. The microstructure of the sintered body is controlled by including crystal boundary phases containing at least R, T and M in the crystal boundary phases, wherein the relative atomic ratios of R, T and M are as follows, i.e., 25 to 35% for R, 60 to 70% for T and 2 to 10% for M.
    Type: Grant
    Filed: December 22, 2014
    Date of Patent: April 9, 2019
    Assignee: TDK CORPORATION
    Inventors: Yoshinori Fujikawa, Yuki Nagamine, Wakako Okawa, Chikara Ishizaka, Eiji Kato, Katsuo Sato
  • Patent number: 10242777
    Abstract: Provided is a sintered magnet that is an R-T-B based sintered magnet having a region having a concentration of at least one heavy rare earth element decreasing from the surface toward the inside, in which the at least one heavy rare earth element includes at least either of Tb or Dy, R includes Nd, T includes Fe, Co, and Cu, there is a grain boundary phase containing at least either of Tb or Dy and Nd between two main phase particles, and a value obtained by subtracting a half value width of a concentration distribution curve of Cu from a half value width of a concentration distribution curve of Tb or Dy in a part including the grain boundary phase is from 10 to 20 nm.
    Type: Grant
    Filed: January 31, 2017
    Date of Patent: March 26, 2019
    Assignee: TDK Corporation
    Inventors: Makoto Iwasaki, Tetsuya Hidaka, Takuma Hayakawa, Ayato Kakoki, Yoshinori Fujikawa, Syota Goto, Haruna Nakajima, Takeshi Masuda, Chikara Ishizaka
  • Publication number: 20190074114
    Abstract: Provided is a sintered magnet that is an R-T-B based sintered magnet having a region having a concentration of at least one heavy rare earth element decreasing from the surface toward the inside, in which the at least one heavy rare earth element includes at least either of Tb or Dy, R includes Nd, T includes Fe, Co, and Cu, there is a grain boundary phase containing at least either of Tb or Dy and Nd between two main phase particles, and a value obtained by subtracting a half value width of a concentration distribution curve of Cu from a half value width of a concentration distribution curve of Tb or Dy in a part including the grain boundary phase is from 10 to 20 nm.
    Type: Application
    Filed: November 6, 2018
    Publication date: March 7, 2019
    Applicant: TDK Corporation
    Inventors: Makoto IWASAKI, Tetsuya HIDAKA, Takuma HAYAKAWA, Ayato KAKOKI, Yoshinori FUJIKAWA, Syota GOTO, Haruna NAKAJIMA, Takeshi MASUDA, Chikara ISHIZAKA
  • Patent number: 10109402
    Abstract: The present invention provides a rare earth based magnet that inhibits the high temperature demagnetization rate even when less or no heavy rare earth elements such as Dy, Tb and the like than before are used. The rare earth based magnet according to the present invention is a sintered magnet which includes R2T14B crystal grains as main phase and grain boundary phases between the R2T14B crystal grains. When the grain boundary phase surrounded by three or more main phase crystal grains is regarded as the grain boundary multi-point, the microstructure of the sintered body is controlled so that the ratio of the grain boundary triple-point surrounded by three main phase crystal grains in all grain boundary multi-points to be specified value or less.
    Type: Grant
    Filed: July 16, 2014
    Date of Patent: October 23, 2018
    Assignee: TDK CORPORATION
    Inventors: Eiji Kato, Yoshinori Fujikawa, Taeko Tsubokura, Chikara Ishizaka, Katsuo Sato
  • Publication number: 20180301257
    Abstract: An R-T-B based sintered magnet including a main phase particle comprising an R2T14B type crystal structure. R is at least one rare earth element, T is at least one transition metal element essentially including Fe or Fe and Co, and B is boron. The R-T-B based sintered magnet includes a magnet surface layer part and a magnet central part existing inside the magnet surface layer part. A crystal orientation degree of the main phase particle in the magnet surface layer part having a magnetic pole surface is lower than the crystal orientation degree of the main phase particle in the magnet central part.
    Type: Application
    Filed: March 29, 2018
    Publication date: October 18, 2018
    Applicant: TDK CORPORATION
    Inventors: Yoshinori FUJIKAWA, Masashi MIWA