Patents by Inventor Takehiko Hamaguchi

Takehiko Hamaguchi 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: 11049518
    Abstract: A data storage device is disclosed comprising a head actuated over a disk comprising servo data for defining a plurality of data tracks, wherein each data track comprises a plurality of data segments. First data is written to data segments of a first data track, and second data is written to data segments of a second data track. After writing the second data, the first data is read at multiple off-track offsets of the first data track to measure an average off-track read capability (OTRC) of the first data track. A cross-track profile is generated for a first data segment of the first data track, and at least part of the cross-track profile is correlated with the measured average OTRC.
    Type: Grant
    Filed: May 15, 2020
    Date of Patent: June 29, 2021
    Assignee: Western Digital Technologies, Inc.
    Inventors: Hiroshi Ide, Takehiko Hamaguchi, Masaomi Ikeda, Naoto Ito
  • Publication number: 20200411050
    Abstract: A data storage device is disclosed comprising a head actuated over a disk comprising servo data for defining a plurality of data tracks, wherein each data track comprises a plurality of data segments. First data is written to data segments of a first data track, and second data is written to data segments of a second data track. After writing the second data, the first data is read at multiple off-track offsets of the first data track to measure an average off-track read capability (OTRC) of the first data track. A cross-track profile is generated for a first data segment of the first data track, and at least part of the cross-track profile is correlated with the measured average OTRC.
    Type: Application
    Filed: May 15, 2020
    Publication date: December 31, 2020
    Inventors: Hiroshi Ide, Takehiko Hamaguchi, Masaomi Ikeda, Naoto Ito
  • Patent number: 10699745
    Abstract: A data storage device is disclosed comprising a head actuated over a disk comprising servo data for defining a plurality of data tracks, wherein each data track comprises a plurality of data segments. First data is written to a first data segment of a first data track, and second data is written to a second data segment of a second data track. After writing the second data, a quality metric is measured for at least two off-track offsets of the first data segment. A track pitch is estimated between the first data segment and the second data segment based on the quality metrics, and a track trajectory is generated for the second data segment based on the estimated track pitch. Third data is written to the second data segment based on the track trajectory.
    Type: Grant
    Filed: June 28, 2019
    Date of Patent: June 30, 2020
    Assignee: Western Digital Technologies, Inc.
    Inventors: Hiroshi Ide, Takehiko Hamaguchi, Masaomi Ikeda, Naoto Ito
  • Patent number: 10607645
    Abstract: A data storage device is disclosed comprising a head actuated over a disk comprising servo data for defining a plurality of data tracks. A plurality of zones are defined for the disk, wherein each zone comprises a plurality of the data tracks. Position error signal (PES) repeatable runout (RRO) values are generated based on the servo data in a first zone, and data sector squeeze RRO values are generated based on data segments in the first zone. A first data track format for the first zone is generated based on the PES RRO values, and a second data track format is generated for the first zone based on the data sector squeeze RRO values.
    Type: Grant
    Filed: June 28, 2019
    Date of Patent: March 31, 2020
    Assignee: Western Digital Technologies, Inc.
    Inventors: Takehiko Hamaguchi, Hiroshi Ide
  • Patent number: 8049986
    Abstract: According to one embodiment, a control method for a magnetic disk device includes writing data by varying a phase of the array period of the plurality of magnetic elements or a phase of the time period of the recording signal in one section of the track from a corresponding phase in another section of the track, reading a reproduction signal from the track, and determining a phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal, based on a reproduction signal read from the one section and a reproduction signal read from the other section. In another embodiment, a magnetic disk includes a track in which magnetic elements are magnetically separated and arranged in an array period, and a phase of the array period in one section is different from a phase in another section of the track.
    Type: Grant
    Filed: August 19, 2009
    Date of Patent: November 1, 2011
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Kenya Ito, Takehiko Hamaguchi
  • Patent number: 7839590
    Abstract: In a method of servo writing of a magnetic recording system and the magnetic recording system, the signal is recorded in a dummy area with a higher recording density than the burst signal. Also, the maximum bit length of the burst area is shortened as compared with the maximum bit length of the data area. A servo control method for perpendicular recording similar to that for longitudinal recording can be used to reduce the development cost. The anti-signal decay performance is also improved. Further, since the variations of the burst signal along the track width is suppressed, the positioning accuracy is improved. These effects combine to produce a reliable magnetic recording system of large capacity.
    Type: Grant
    Filed: September 9, 2008
    Date of Patent: November 23, 2010
    Assignee: Hitachi Global Storage Technologies Japan, Ltd.
    Inventors: Yasutaka Nishida, Takehiko Hamaguchi, Hideki Sawaguchi, Hisashi Takano
  • Patent number: 7724490
    Abstract: Embodiments in accordance with the present invention provide a degaussing device and a degaussing method capable of efficiently degaussing a magnetic disk, especially, a magnetic disk of the perpendicular magnetic recording system, without resorting to a magnetic field of a high intensity. Embodiments in accordance with the present invention provide a degaussing method of degaussing a magnetic disk not yet installed in a magnetic disk drive by applying an external magnetic field to the magnetic disk by a degaussing device. In accordance with one embodiment, the method includes disposing the magnetic disk in the degaussing device such that the direction of an external magnetic field is inclined at an angle to the axis of easy magnetization of the magnetic disk.
    Type: Grant
    Filed: April 24, 2007
    Date of Patent: May 25, 2010
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Hitoshi Tamura, Hiroki Mori, Mitsuru Hamaguchi, Kunihiko Mine, Takehiko Hamaguchi
  • Publication number: 20100085657
    Abstract: According to one embodiment, a control method for a magnetic disk device includes writing data by varying a phase of the array period of the plurality of magnetic elements or a phase of the time period of the recording signal in one section of the track from a corresponding phase in another section of the track, reading a reproduction signal from the track, and determining a phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal, based on a reproduction signal read from the one section and a reproduction signal read from the other section. In another embodiment, a magnetic disk includes a track in which magnetic elements are magnetically separated and arranged in an array period, and a phase of the array period in one section is different from a phase in another section of the track.
    Type: Application
    Filed: August 19, 2009
    Publication date: April 8, 2010
    Inventors: Kenya Ito, Takehiko Hamaguchi
  • Patent number: 7545595
    Abstract: A magnetic disk apparatus including: a disk holding data as magnetic information on a magnetic recording film; a head to perform writing and reading of the magnetic information; a rotary actuator to move the head in a radial direction of the disk; plural heat elements in the head to locally heat the disk; a write element in the head to apply a magnetic field to the disk; and means for selecting at least one heat element from the plural heat elements, wherein the means for selecting the heat element selects at least one heat element from the plural heat elements so as to bring a center line of an area heated by the heat element and a center line of the position of the magnetic field generated by the write element into approximate correspondence, in correspondence with a relative angle between the head and a direction of movement of the disk.
    Type: Grant
    Filed: February 16, 2006
    Date of Patent: June 9, 2009
    Assignee: Hitachi Global Storage Technologies Japan, Ltd.
    Inventors: Takehiko Hamaguchi, Atsushi Nakamura, Yasutaka Nishida, Masafumi Mochizuki, Hideki Sawaguchi
  • Patent number: 7525765
    Abstract: In a magnetic disk apparatus, mounting of plural heating elements to a magnetic head slider is permitted. Thermally assisted magnetic recording from inner to outer surface is permitted at a small amount of power consumption. In one embodiment, the magnetic disk apparatus has a magnetic disk on which magnetic information is recorded, a magnetic head slider having an air bearing surface for floating from the magnetic disk in proximity thereto, and a rotary actuator moving over the disk arcuately while supporting the magnetic head slider by a suspension. A recording element acting to record magnetic information on the magnetic disk, a playback element acting to play back the magnetic information recorded on the magnetic disk, and plural heating elements acting to locally heat the magnetic disk are carried on the magnetic head slider.
    Type: Grant
    Filed: December 8, 2005
    Date of Patent: April 28, 2009
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Masayuki Kurita, Takehiko Hamaguchi, Hidekazu Kohira, Mikio Tokuyama
  • Patent number: 7518814
    Abstract: Embodiments of the invention provide an inexpensive magnetic head tester employing component parts of a production HDD and capable of exercising functions very close to those of a production HDD. In one embodiment, a magnetic head tester employs the VCM actuator and the control circuit of a production HDD and has a lightweight, simple HGA fixing mechanism mounted on an actuator arm. The HGA fixing mechanism fixes an HGA to the actuator arm by a method using a very light holding spring mounted on the arm, a method of mechanically clamping an HGA by using air pressure, or a method of fixing an HGA to the arm by elastically deforming a rubber clamping member by air pressure. Servo control is achieved by the actuator of a production VCM. An end part of the VCM actuator is stopped by a stopping mechanism and is held by a holding spring to prevent the runaway of the VCM actuator. Servo control is performed by balancing the driving force of the VCM and the resilience of the spring.
    Type: Grant
    Filed: September 1, 2006
    Date of Patent: April 14, 2009
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Hiroshi Umezaki, Norifumi Miyamoto, Kazuhiko Washizu, Takehiko Hamaguchi, Kenji Itoh
  • Patent number: 7486485
    Abstract: Embodiments of the invention prevent a decrease in magnetization or demagnetization from occurring to recording magnetization regardless of a direction in which a stray field is applied. In one embodiment, an apparatus for data storage system comprises a head having a magnetic field shield in the vicinity of a main pole, and a cover of the device, using a constituent material with a magnetic field shielding effect, across the cover, or at part thereof. When a stray field in a direction perpendicular to a recording medium is applied, the effect of the magnetic field is alleviated by the magnetic field shield installed in the vicinity of the main pole. In such a case, it need only be sufficient to form the magnetic field shield in a shape optimum for removing the stray field in the perpendicular direction only.
    Type: Grant
    Filed: October 28, 2005
    Date of Patent: February 3, 2009
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Takehiko Hamaguchi, Yoshihisa Kamo, Hideaki Maeda, Yukiya Shimizu, Ikuya Tagawa, Tetsuo Yuki
  • Publication number: 20090021854
    Abstract: In a method of servo writing of a magnetic recording system and the magnetic recording system, the signal is recorded in a dummy area with a higher recording density than the burst signal. Also, the maximum bit length of the burst area is shortened as compared with the maximum bit length of the data area. A servo control method for perpendicular recording similar to that for longitudinal recording can be used to reduce the development cost. The anti-signal decay performance is also improved. Further, since the variations of the burst signal along the track width is suppressed, the positioning accuracy is improved. These effects combine to produce a reliable magnetic recording system of large capacity.
    Type: Application
    Filed: September 9, 2008
    Publication date: January 22, 2009
    Inventors: Yasutaka Nishida, Takehiko Hamaguchi, Hideki Sawaguchi, Hisashi Takano
  • Patent number: 7474493
    Abstract: The invention provides a servo pattern that is stable for long time, easily writable, and excellent in S/N. DC-signal area included in a burst area of a servo pattern comprises combination of positive and negative DC-signals, low-density dummy bit, or pattern having phases that are deviated each other so that the sum of magnetization of the burst area of the servo pattern is equalized to 0.
    Type: Grant
    Filed: November 6, 2003
    Date of Patent: January 6, 2009
    Assignee: Hitachi Global Storage Technologies Japan, Ltd.
    Inventors: Takehiko Hamaguchi, Hideaki Maeda, Kazuhisa Shishida, Yasutaka Nishida
  • Patent number: 7443625
    Abstract: In the present invention, by making the width of the write element larger than the track pitch and securing a write magnetic field strong enough to reverse the magnetization of the magnetic layer, and further by writing while shifting a write head comprising the write element, a magnetic disk drive, of which the track width is narrower than the write element width, and the storage capacity is large, is realized.
    Type: Grant
    Filed: April 17, 2006
    Date of Patent: October 28, 2008
    Assignee: Hitachi Global Storage Technologies Japan Ltd.
    Inventors: Takehiko Hamaguchi, Atsushi Nakamura, Yasutaka Nishida, Hisashi Takano, Yohji Maruyama, Hiroshi Ide, Hideki Sawaguchi, Futoshi Tomiyama
  • Patent number: 7436611
    Abstract: In a method of servo writing of a magnetic recording system and the magnetic recording system, the signal is recorded in a dummy area with a higher recording density than the burst signal. Also, the maximum bit length of the burst area is shortened as compared with the maximum bit length of the data area. A servo control method for perpendicular recording similar to that for longitudinal recording can be used to reduce the development cost. The anti-signal decay performance is also improved. Further, since the variations of the burst signal along the track width is suppressed, the positioning accuracy is improved. These effects combine to produce a reliable magnetic recording system of large capacity.
    Type: Grant
    Filed: March 17, 2006
    Date of Patent: October 14, 2008
    Assignee: Hitachi Global Storage Technologies Japan, Ltd.
    Inventors: Yasutaka Nishida, Takehiko Hamaguchi, Hideki Sawaguchi, Hisashi Takano
  • Publication number: 20080192379
    Abstract: Embodiments of the present invention provide a process that monitors a magnetic playback signal while gradually increasing an electricity supply amount for a heater to thereby determine contact between a magnetic head slider and a magnetic disk medium. According to one embodiment, after components for configuring a magnetic recording/playback portion are assembled into a housing, magnetic information is played back on a specific track of a magnetic disk medium by using a playback element while gradually increasing an electricity supply amount for a heater of a magnetic head slider. An amplitude of a playback signal is measured at a plurality of portions along a circumferential direction of the track. Contact between the magnetic head slider and the magnetic disk medium is detected in accordance with an increase in variation in the measured amplitude.
    Type: Application
    Filed: January 24, 2008
    Publication date: August 14, 2008
    Inventors: Masayuki Kurita, Hideaki Tanaka, Noriaki Satoh, Toyomi Ohsawa, Toshiya Shiramatsu, Atsushi Yatagai, Satoshi Ohki, Hiroshi Ide, Hidekazu Kohira, Takehiko Hamaguchi
  • Publication number: 20080186629
    Abstract: Embodiments of the present invention provide a method of producing a magnetic disk device in which a plurality of heads can appropriately record servo data on a magnetic disk. The method of producing the magnetic disk device according to one embodiment includes the steps of: attaching a magnetic disk, a plurality of heads and head amplifier circuit to the magnetic disk device; and recording the servo data input through the head amplifier circuit with the plurality of heads on the magnetic disk all at once; wherein the head amplifier circuit includes a plurality of amplifiers provided corresponding to the plurality of heads respectively and a plurality of registers which is provided corresponding to the plurality of amplifiers respectively and holds set values determining the amplification of the amplifiers, and the step of recording the servo data is conducted with the plurality of registers included in the head amplifier circuit individually set.
    Type: Application
    Filed: January 16, 2008
    Publication date: August 7, 2008
    Applicant: Hitachi Global Storage Technologies Inc.
    Inventors: Takehiko Hamaguchi, Yukiya Shimizu, Satoshi Ohki, Hideaki Maeda
  • Patent number: 7365933
    Abstract: Embodiments of the invention provide optimum servo patterns for perpendicular magnetic recording method. In one embodiment, a burst field of servo patterns is composed of burst-signal parts in each of which a constant frequency occurs successively and zero-signal parts each of which has been demagnetized to a state of zero-magnetization, and the total magnetization of the burst field is made approximately 0. The zero signal portions are formed by shutting off a write current at a time during an operation to record servo patterns on a disk initialized to a state of zero-magnetization. The total magnetization of all servo patterns is made approximately 0 by encoding an address mark field and a track code field of servo patterns by a phase shift method.
    Type: Grant
    Filed: January 12, 2006
    Date of Patent: April 29, 2008
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Takehiko Hamaguchi, Hideaki Maeda, Kazuaki Usui, Kazuhisa Shishida, Takashi Konishi
  • Patent number: 7289284
    Abstract: Embodiments of the invention prevent demagnetization or degaussing of recorded magnetizations, even if a stray field is applied. In one embodiment, an output of a read head including a magneto-resistive effect element is inputted to a stray field detector through a DC amplifier and a DC filter. The stray field detector monitors dc components of the output from the read head, and escapes a head from above a magnetic recording medium.
    Type: Grant
    Filed: August 1, 2005
    Date of Patent: October 30, 2007
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Reiko Arai, Takehiko Hamaguchi, Atsushi Kikugawa, Hideaki Maeda, Liping Shen, Mikio Suzuki