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US 12,198,740 B1Granted
Magnetic disk device and method of detecting flying height of magnetic head
AssigneesKabushiki Kaisha Toshiba, Toshiba Electronic Devices & Storage Corporation
InventorMasayuki Kondo
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Abstract
According to one embodiment, a magnetic disk device comprising a magnetic head expanding to the magnetic disk side with the generated heat of a heater, a flying height measurement unit measuring a flying height of the magnetic head, based on a read signal of the magnetic head for data for measuring flying height written to the magnetic disk, and a controller. The controller detects variation of a measurement value of the flying height measurement unit, based on change of “correspondence between a change amount of the supply power and a measurement value of the flying height measurement unit”.
Claims9
A magnetic disk device comprising:
- a magnetic head performing data write to and data read from a magnetic disk, including a heater generating heat with supplied power, and expanding to the magnetic disk side with the generated heat of the heater;
- a flying height measurement unit measuring a flying height of the magnetic head, based on a read signal of the magnetic head for data for measuring flying height written to the magnetic disk;
- and
- a controller controlling the supply power to the heater;
- wherein
- the controller detects variation of a measurement value of the flying height measurement unit, based on change of “correspondence between a change amount of the supply power and a measurement value of the flying height measurement unit”;
- at a first time point, the controller reads the data for measuring the flying height with the magnetic head while changing the supply power in a decreasing direction from a reference value, monitors a first measurement value of the flying height measurement unit based on the read signal, obtains a first slope of change of the first measurement value for the change amount of the supply power by performing one differential operation off a quadratic approximation of the first measurement value, and obtains a “third correspondence between the first slope and the first measurement value” based on “a first correspondence between the change amount of the supply power and the first measurement value” and “a second correspondence between the change amount of the supply power and the first slope”,
- at a second time point, the controller reads the data for measuring the flying height with the magnetic head by setting the supply power to a first predetermined value, captures the measurement value of the flying height measurement unit based on the read signal as a first capture value, reads the data for measuring the flying height with the magnetic head by setting the supply power to a second predetermined value lower than the first predetermined value, captures the measurement value of the flying height measurement unit based on the read signal as a second capture value, and obtains a second slope of change between the first and second capture values of the measurement value of the flying height measurement unit for a change amount between the first and second predetermined values of the supply power, and
- the controller detects deviation between the first slope and the second slope as the variation of the measurement value of the flying height measurement unit.
6 more elements
A method of detecting a flying height of a magnetic head in a magnetic disk device, the device comprising:
- a magnetic head performing data write to and data read from a magnetic disk, including a heater generating heat with supplied power, and expanding to the magnetic disk side with the generated heat of the heater;
- a flying height measurement unit measuring a flying height of the magnetic head, based on a read signal of the magnetic head for data for measuring flying height written to the magnetic disk;
- and
- a controller controlling the supply power to the heater;
- the method comprising:
- detecting variation of a measurement value of the flying height measurement unit based on change of “correspondence between a change amount of the supply power and a measurement value of the flying height measurement unit”;
- wherein
- at a first time point, reading the data for measuring the flying height with the magnetic head while changing the supply power in a decreasing direction from a reference value, monitoring a first measurement value of the flying height measurement unit based on the read signal, obtaining a first slope of change of the first measurement value for the change amount of the supply power by performing one differential operation of a quadratic approximation of the first measurement value, and obtaining a “third correspondence between the first slope and the first measurement value” based on “a first correspondence between the change amount of the supply power and the first measurement value” and “a second correspondence between the change amount of the supply power and the first slope”,
- at a second time point, reading the data for measuring the flying height with the magnetic head by setting the supply power to a first predetermined value, capturing the measurement value of the flying height measurement unit based on the read signal as a first capture value, reading the data for measuring the flying height with the magnetic head by setting the supply power to a second predetermined value lower than the first predetermined value, capturing the measurement value of the flying height measurement unit based on the read signal as a second capture value, and obtaining a second slope of change between the first and second capture values of the measurement value of the flying height measurement unit for a change amount between the first and second predetermined values of the supply power, and
- detecting deviation between the first slope and the second slope as the variation of the measurement value of the flying height measurement unit.
7 more elements
Dependencies are inferred from the claim text.