Hitachi Global Storage Technologies Netherlands B.v.

Kenichi Kuramoto

Kenji Kuroki

Yoshihiko Maeda

Masayuki Kurita

Toru Aida

Yasuhiro Kotani

Masayuki Ishikawa

Shinya Sakamoto

Nobuhiro Kuwamura

Takanori Kawakami

Takao Matsui

Nobuhiko Wasa

Sayaka Nojiri

Hidefumi Tominaga

Shinji Matsushita

Hiroyasu Masuda

Akihiro Sera

Takahiro Nishioka

A method for measuring change of clearance between a head and a disk. The method includes reading a preliminarily written data string for clearance measurement on a disk to obtain a first measured value corresponding to a clearance, and writing a new data string for deterioration check onto the disk and reading the data string for deterioration check to obtain a second measured value corresponding to the clearance. The method also includes determining a deterioration of the data string for clearance measurement from a difference between the first measured value and the second measured value, measuring a clearance change using the data string for clearance measurement by a normal operation if the determination is that the data string for clearance measurement has not deteriorated, and measuring a clearance change by an operation different from the normal operation if the determination is that the data string for clearance measurement has deteriorated.

Disk drive and method for measuring clearance change in the disk drive

A disk drive. The disk drive includes a disk, a head, a head-slider, a moving mechanism, and a controller. The head is configured to access the disk. The head-slider includes the head, and is configured to fly in proximity to a recording surface of the disk. The moving mechanism is configured to move the head-slider over the disk, and to support the head-slider. The controller is configured to read out at least one from a plurality of clearance-measurement data strings from the recording surface of the disk using the head, and to calculate a clearance between the head and the disk from clearance-measurement results obtained from a plurality of resolutions with different frequency components.

Disk drive and method for measuring clearance between a head and a disk in a disk drive

A disk drive. The disk drive includes a disk configured to store data, a slider configured to fly in proximity to the disk, and a magnetic-recording head on the slider configured to access the disk. The disk drive also includes a moving mechanism configured to support and to move the head-slider, an adjustment portion configured to adjust clearance between the magnetic-recording head and the disk, and a controller configured to control the adjustment portion to control the clearance. The controller is configured to perform clearance control in a first mode in an operation selected from the group consisting of reading user data and writing user data according to a change in fly height of the slider after a load operation, and subsequently is configured to perform clearance control in a second mode in an operation selected from the group consisting of reading user data and writing user data.

Disk drive and method for controlling clearance in the disk drive

Embodiments of the present invention precisely measure clearance variation by temperature change using a value in a RW channel. In an embodiment of the present invention, an HDD measures resolution by signals in a RW channel. The measured resolution shows variations depending on temperature according to two factors. One factor is the clearance variation depending on the temperature and the other is the variation in operational property of the RW channel depending on the temperature. The HDD compensates for the temperature variation of the resolution according to the two factors. The HDD uses two kinds of sensed temperature. One corresponds to the temperature inside an enclosure in which head sliders are provided and the other corresponds to the temperature of the chip in which the RW channel is implemented. Sensing the drive temperature and the channel temperature independently achieves precise compensation for the variation in the measured resolution caused by clearance variation and channel property.

Disc drive device

Embodiments of the present invention help to detect contact between a head and a magnetic disk more accurately in specifying a heater power value for adjusting a clearance between a head element portion and the disk. According to one embodiment, a hard disk controller/multiprocessing unit (HDC/MPU) measures amplitudes of read signals in a user data field DATA. A hard disk drive (HDD) fills a gap between servo data with single data sector. The HDC/MPU measures the amplitudes of read signals in each data sector at different heater power values. It determines the heater power value at which contact occurs from the measured values.

Device and method for specifying control value for controlling clearance between head and disk, and magnetic disk drive device

Embodiments of the present invention help to prevent destabilization in voice coil motor (VCM) velocity control. According to one embodiment, a hard disk controller/multiprocessing unit (HDC/MPU) calibrates a correction operational coefficient of a detected back electromotive force (EMF) voltage before unloading. The calibration is carried out in a state that an actuator is pivoting. The HDC/MPU calibrates the correction coefficient according to a motion equation of the actuator using VCM current applied to a VCM and a detected value of a back EMF voltage detection circuit.

Disk drive and calibration method therefor

Embodiments of the invention improve utility of a magnetic disk drive in which a head is retracted if the magnetic disk drive is in a dropping state. In one embodiment, an HDC/MPU provided in a magnetic disk drive judges whether the magnetic disk drive is in a dropping state based on an output from an acceleration sensor which may detect an acceleration and performs a retraction operation of a head. After the HDC/MPU judges that a drop is occurring, the HDC/MPU detects whether the drop judgment is incorrect according to whether a shock sensor detects a shock occurrence and changes the drop judgment condition based on a detection history of detected incorrect judgments.

Magnetic disk drive with head retraction control

Embodiments of the invention prevent the magnetic head from dropping to the magnetic disk when it is retracted. If the power supply Vcc to the drive is interrupted, a power supply voltage detecting section detects that the power supply to the drive is interrupted. A control section sets switches to the ON state in order to discharge the charged retract capacitor and supply the discharge current to a voice coil. The control section retains the switches in the ON state for a period which is determined based on the discharge period specifying control data stored in a register and the count signal from a counter. A voice coil motor, to which the current is supplied, turns the actuator in the unloading direction to retract the actuator to the ramp.

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Kanagawa, Japan

Kenichi Kuramoto