Patents by Inventor Yoshitaka Murakawa

Yoshitaka Murakawa 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: 20210118598
    Abstract: A ferrite sintered magnet 100 comprises M-type ferrite crystal grains 4 and multiple-crystal grain boundaries 6b surrounded by three or more of the M-type ferrite crystal grains 4. The ferrite sintered magnet 100 contains at least Fe, Ca, B, and Si, and contains 0.005 to 0.9 mass % of B in terms of B2O3. The multiple-crystal grain boundaries 6b contain Si and Ca, and in a case where the molar ratio of Ca to Si in the multiple-crystal grain boundaries 6b is represented by (Ca/Si)G, the following formula is satisfied. 0.1<(Ca/Si)G<0.
    Type: Application
    Filed: October 14, 2020
    Publication date: April 22, 2021
    Applicant: TDK Corporation
    Inventors: Yoshitaka MURAKAWA, Hiroyuki MORITA, Masanori IKEDA, Shogo MUROYA, Tomokazu ISHIKURA
  • Publication number: 20210090768
    Abstract: The present invention provides a ferrite sintered magnet comprising ferrite crystal grains having a hexagonal structure, wherein the ferrite sintered magnet comprises metallic elements at an atomic ratio represented by formula (1). In formula (1), R is at least one element selected from the group consisting of Bi and rare-earth elements, and R comprises at least La. In formula (1), w, x, z and m satisfy formulae (2) to (5). The above-mentioned ferrite sintered magnet further has a coefficient of variation of a size of the crystal grains in a section parallel to a c axis of less than 45%. Ca1-w-xRwSrxFezCom??(1) 0.360?w=0.420??(2) 0.110?x?0.173??(3) 8.51?z?9.71??(4) 0.208?m?0.
    Type: Application
    Filed: September 21, 2020
    Publication date: March 25, 2021
    Applicant: TDK Corporation
    Inventors: Tomokazu ISHIKURA, Masanori IKEDA, Yoshitaka MURAKAWA, Hiroyuki MORITA, Shogo MUROYA
  • Publication number: 20200312496
    Abstract: A ferrite sintered magnet 100 comprises M-type ferrite crystal grains 4 having a hexagonal structure, two-crystal grain boundaries 6a formed between two of the M-type ferrite crystal grains 4, and multiple-crystal grain boundaries 6b surrounded by three or more of the M-type ferrite crystal grains 4. This ferrite sintered magnet 100 contains at least Fe, Ca, B, and Si, and contains B in an amount of 0.005 to 0.9 mass % in terms of B2O3, the two-crystal grain boundaries 6a and the multiple-crystal grain boundaries 6b contain Si and Ca, and in a cross-section parallel to a c-axis of the ferrite sintered magnet, when the number of multiple-crystal grain boundaries 6b having a maximum length of 0.49 to 5 ?m per cross-sectional area of 76 ?m2 is N, N is 7 or less.
    Type: Application
    Filed: March 23, 2020
    Publication date: October 1, 2020
    Applicant: TDK Corporation
    Inventors: Yoshitaka MURAKAWA, Shogo MUROYA, Hiroyuki MORITA, Masanori IKEDA
  • Publication number: 20200312495
    Abstract: A ferrite sintered magnet comprising an M type Sr ferrite having a hexagonal structure as a main phase, wherein the ferrite sintered magnet comprises La and Co, a content of B is 0.005 to 0.9% by mass in terms of B2O3, a content of Zn is 0.01 to 1.2% by mass in terms of ZnO, and the ferrite sintered magnet satisfies [La]/[Zn]?0.79 and [Co]/[Zn]?0.67 when an atomic concentration of La is represented by [La], an atomic concentration of Co is represented by [Co], and an atomic concentration of Zn is represented by [Zn].
    Type: Application
    Filed: March 20, 2020
    Publication date: October 1, 2020
    Applicant: TDK Corporation
    Inventors: Yoshitaka MURAKAWA, Shogo MUROYA, Hiroyuki MORITA, Masanori IKEDA
  • Publication number: 20200312497
    Abstract: This ferrite sintered magnet comprises ferrite phases having a magnetoplumbite type crystal structure. This magnet comprises an element R, an element M, Fe, Co, B, Mn and Cr, the element R is at least one element selected from rare earth elements including Y, the element M is at least one element selected from the group consisting of Ca, Sr and Ba, with Ca being an essential element, and when an atomic composition of metallic elements is represented by R1-xMxFem-yCoy, x, y and m satisfy formulae: 0.2?x?0.8??(1) 0.1?y?0.65??(2) 3?m<14??(3). Additionally, a content of B is 0.1 to 0.4% by mass in terms of B2O3, a content of Mn is 0.15 to 1.02% by mass in terms of MnO, and a content of Cr is 0.02 to 2.01% by mass in terms of Cr2O3.
    Type: Application
    Filed: March 20, 2020
    Publication date: October 1, 2020
    Applicant: TDK Corporation
    Inventors: Shogo MUROYA, Yoshitaka MURAKAWA, Hiroyuki MORITA, Masanori IKEDA
  • Publication number: 20200312493
    Abstract: A ferrite sintered magnet comprising an M type Sr ferrite having a hexagonal structure as a main phase, wherein the ferrite sintered magnet does not substantially comprise a rare earth element and Co, a content of B is 0.005 to 0.9% by mass in terms of B2O3, and a content of Zn is 0.01 to 1.2% by mass in terms of ZnO.
    Type: Application
    Filed: March 19, 2020
    Publication date: October 1, 2020
    Applicant: TDK Corporation
    Inventors: Yoshitaka MURAKAWA, Shogo MUROYA, Hiroyuki MORITA, Masanori IKEDA
  • Publication number: 20200312494
    Abstract: A ferrite sintered magnet 100 comprises M-type ferrite crystal grains 4 having a hexagonal crystal structure, two-crystal grain boundaries 6a formed between two of the M-type ferrite crystal grains 4, and multiple-crystal grain boundaries 6b surrounded by three or more of the M-type ferrite crystal grains 4. This ferrite sintered magnet 100 contains at least Fe, Ca, B, and Si, and contains B in an amount of 0.005 to 0.9 mass % in terms of B2O3, the two-crystal grain boundaries 6a and the multiple-crystal grain boundaries 6b contain Si and Ca, and in a cross-section parallel to a c-axis of the ferrite sintered magnet, when the number of multiple-crystal grain boundaries having a maximum length of 0.088 or more and less than 0.49 ?m per cross-sectional area of 76 ?m2 is P, P is 8 or more.
    Type: Application
    Filed: March 20, 2020
    Publication date: October 1, 2020
    Applicant: TDK Corporation
    Inventors: Yoshitaka MURAKAWA, Shogo MUROYA, Hiroyuki MORITA, Masanori IKEDA
  • Publication number: 20200255339
    Abstract: This ferrite sintered magnet comprises metallic elements at an atomic ratio represented by formula (1): Ca1-w-xRwSrxFezCom ??(1) in formula (1), R is at least one element selected from the group consisting of rare-earth elements and Bi, and R comprises at least La, in formula (1), w, x, z and m satisfy formulae (2) to (5): 0.360?w?0.420 ??(2) 0.110?x?0.173 ??(3) 8.51?z?9.71 ??(4) 0.208?m?0.269 ??(5), and in a section parallel to an axis of easy magnetization, when the number of total ferrite grains is N and the number of ferrite grains having a stacking fault is n, 0?n/N?0.20 is satisfied.
    Type: Application
    Filed: February 5, 2020
    Publication date: August 13, 2020
    Applicant: TDK Corporation
    Inventors: Masanori IKEDA, Hiroyuki MORITA, Yoshitaka MURAKAWA, Shogo MUROYA
  • Publication number: 20200251262
    Abstract: A ferrite sintered magnet comprises a plurality of main phase grains containing a ferrite having a hexagonal structure, wherein at least some of the main phase grains are core-shell structure grains each having a core and a shell covering the core; and wherein the minimum value of the content of La in the core is [La]c atom %; the minimum value of the content of Co in the core is [Co]c atom %; the maximum value of the content of La in the shell is [La]s atom %; the maximum value of the content of Co in the shell is [Co]s atom %; [La]c+[Co]c is 3.08 atom % or more and 4.44 atom % or less; and [La]s+[Co]s is 7.60 atom % or more and 9.89 atom % or less.
    Type: Application
    Filed: January 31, 2020
    Publication date: August 6, 2020
    Applicant: TDK Corporation
    Inventors: Hiroyuki MORITA, Masanori IKEDA, Yoshitaka MURAKAWA, Shogo MUROYA
  • Publication number: 20190304642
    Abstract: A ferrite sintered magnet comprising ferrite particles having a hexagonal structure is provided. The ferrite sintered magnet comprises metallic elements at an atomic ratio represented by formula (1). In formula (1), R is at least one element selected from the group consisting of rare-earth elements and Bi, and comprises at least La. In formula (1), w, x, z and m satisfy formulae (2) to (5). The above-mentioned ferrite sintered magnet comprises 0.037 to 0.181% by mass of B in terms of H3BO3. Ca1?w?xRwSrxFezCom ??(1) 0.360?w?0.420 ??(2) 0.110?x?0.173 ??(3) 8.51?z?9.71 ??(4) 0.208?m?0.
    Type: Application
    Filed: February 7, 2019
    Publication date: October 3, 2019
    Applicant: TDK Corporation
    Inventors: Masanori IKEDA, Hiroyuki MORITA, Yoshitaka MURAKAWA, Taku MURASE
  • Publication number: 20190304643
    Abstract: The present invention provides a ferrite sintered magnet comprising (1) main phase grains containing a ferrite having a hexagonal structure, (2) two-grain boundaries formed between two of the main phase grains, and (3) multi-grain boundaries surrounded by three or more of the main phase grains. The above ferrite sintered magnet comprises Ca, R, Sr, Fe and Co, with R being at least one element selected from the group consisting of rare earth elements and Bi, and comprising at least La. The number Nm of the above main phase grains and the number Ng of the above multi-grain boundaries in the cross section including the direction of the easy magnetization axis of the above ferrite sintered magnet satisfy the formula (1A): 50%?Nm/(Nm+Ng)?65%??(1A).
    Type: Application
    Filed: March 7, 2019
    Publication date: October 3, 2019
    Applicant: TDK Corporation
    Inventors: Hiroyuki MORITA, Masanori IKEDA, Yoshitaka MURAKAWA, Hiroyuki ONO, Taku MURASE
  • Publication number: 20190304641
    Abstract: There is provided a ferrite sintered magnet having a high residual magnetic flux density. A ferrite sintered magnet 2 includes a plurality of main phase particles 5 including ferrite having a hexagonal structure, the number of core-shell structured particles 5A having a core 7 and a shell 9 covering the core 7, among the main phase particles 5, is smaller than the number of the main phase particles 5 other than the core-shell structured particles 5A.
    Type: Application
    Filed: February 5, 2019
    Publication date: October 3, 2019
    Applicant: TDK Corporation
    Inventors: Hiroyuki MORITA, Masanori IKEDA, Yoshitaka MURAKAWA, Taku MURASE
  • Patent number: 9627112
    Abstract: A sintered ferrite magnet comprises a main phase of an M type Sr ferrite having a hexagonal crystal structure. An amount of Zn is 0.05 to 1.35 mass % in terms of ZnO and M1/M2 is 0.43 or less when an amount of a rare-earth element (R) is M1 in terms of mol and the amount of Zn is M2 in terms of mol.
    Type: Grant
    Filed: March 4, 2015
    Date of Patent: April 18, 2017
    Assignee: TDK CORPORATION
    Inventors: Yoshitaka Murakawa, Naoharu Tanigawa, Yoshihiko Minachi, Hitoshi Taguchi
  • Patent number: 9589713
    Abstract: A sintered ferrite magnet comprises a main phase of an M type Sr ferrite having a hexagonal crystal structure. An amount of Zn is 0.05 to 1.35 mass % in terms of ZnO, the sintered ferrite magnet does not substantially include a rare-earth element (R), and the following Formula (1) is satisfied, where a total amount of Sr, Ba and Ca is M3 in terms of mol, a total amount of Fe, Co, Mn, Zn, Cr and Al is M4 in terms of mol, and an amount of Si is M5 in terms of mol. 0.5?{M3?(M4/12)}/M5?4.8??(1).
    Type: Grant
    Filed: March 4, 2015
    Date of Patent: March 7, 2017
    Assignee: TDK CORPORATION
    Inventors: Yoshitaka Murakawa, Naoharu Tanigawa, Yoshihiko Minachi, Hitoshi Taguchi
  • Publication number: 20150255198
    Abstract: A sintered ferrite magnet comprises a main phase of an M type Sr ferrite having a hexagonal crystal structure. An amount of Zn is 0.05 to 1.35 mass % in terms of ZnO and M1/M2 is 0.43 or less when an amount of a rare-earth element (R) is M1 in terms of mol and the amount of Zn is M2 in terms of mol.
    Type: Application
    Filed: March 4, 2015
    Publication date: September 10, 2015
    Inventors: Yoshitaka MURAKAWA, Naoharu TANIGAWA, Yoshihiko MINACHI, Hitoshi TAGUCHI
  • Publication number: 20150255197
    Abstract: A sintered ferrite magnet comprises a main phase of an M type Sr ferrite having a hexagonal crystal structure. An amount of Zn is 0.05 to 1.35 mass % in terms of ZnO, the sintered ferrite magnet does not substantially include a rare-earth element (R), and the following Formula (1) is satisfied, where a total amount of Sr, Ba and Ca is M3 in terms of mol, a total amount of Fe, Co, Mn, Zn, Cr and Al is M4 in terms of mol, and an amount of Si is M5 in terms of mol. 0.5?{M3?(M4/12)}/M5?4.
    Type: Application
    Filed: March 4, 2015
    Publication date: September 10, 2015
    Inventors: Yoshitaka MURAKAWA, Naoharu TANIGAWA, Yoshihiko MINACHI, Hitoshi TAGUCHI
  • Patent number: 8507395
    Abstract: A dielectric ceramic composition comprising a compound expressed by a formula of ABO3, where “A” is Ba alone, or Ba and at least one selected from Ca and Sr, and “B” is Ti alone, or Ti and Zr, and having a perovskite-type crystal structure, and an oxide of a rare-earth element including Sc and Y. The dielectric ceramic composition includes a dielectric particle having a core-shell structure which has a core and a shell, the shell being present around the core and including at least “R” element, and in the shell, a region showing a maximum content rate of “R” element is a boundary region between the core and the shell.
    Type: Grant
    Filed: August 30, 2011
    Date of Patent: August 13, 2013
    Assignee: TDK Corporation
    Inventors: Yoshitaka Murakawa, Yukie Nakano, Shirou Ootsuki
  • Publication number: 20120050941
    Abstract: A dielectric ceramic composition comprising a compound expressed by a formula of ABO3, where “A” is Ba alone, or Ba and at least one selected from Ca and Sr, and “B” is Ti alone, or Ti and Zr, and having a perovskite-type crystal structure, and an oxide of a rare-earth element including Sc and Y. The dielectric ceramic composition includes a dielectric particle having a core-shell structure which has a core and a shell, the shell being present around the core and including at least “R” element, and in the shell, a region showing a maximum content rate of “R” element is a boundary region between the core and the shell.
    Type: Application
    Filed: August 30, 2011
    Publication date: March 1, 2012
    Applicant: TDK CORPORATION
    Inventors: Yoshitaka MURAKAWA, Yukie NAKANO, Shirou OOTSUKI
  • Patent number: 7275166
    Abstract: Provided is a power saving control method and system for data storage devices or electrical equipment. Herein, data items are divided into groups according to required response times or access frequencies. The groups of data items are allocated to data storage devices or pieces of electrical equipment. A data storage device or electrical equipment to which data that may be accessed using a long response time at a low access frequency is set to a power-saving mode of a higher level. Consequently, the data storage devices or pieces of electrical equipment are provided with power-saving features of different levels. Eventually, energy saving can be achieved more efficiently.
    Type: Grant
    Filed: March 24, 2005
    Date of Patent: September 25, 2007
    Assignee: Fujitsu Limited
    Inventors: Yoshihiko Kaiju, Shoichi Yoshida, Yoshitaka Murakawa, Akio Futamata, Katsuyoshi Ito
  • Publication number: 20050273638
    Abstract: Provided is a power saving control method and system for data storage devices or electrical equipment. Herein, data items are divided into groups according to required response times or access frequencies. The groups of data items are allocated to data storage devices or pieces of electrical equipment. A data storage device or electrical equipment to which data that may be accessed using a long response time at a low access frequency is set to a power-saving mode of a higher level. Consequently, the data storage devices or pieces of electrical equipment are provided with power-saving features of different levels. Eventually, energy saving can be achieved more efficiently.
    Type: Application
    Filed: March 24, 2005
    Publication date: December 8, 2005
    Applicant: FUJITSU LIMITED
    Inventors: Yoshihiko Kaiju, Shoichi Yoshida, Yoshitaka Murakawa, Akio Futamata, Katsuyoshi Ito