Magnetic disk drive and control method thereof
View Patent ↗Embodiments of the present invention provide a magnetic disk drive capable of suppressing variations in flying height of a magnetic head caused by decrease in the amount of a low density gas inside a housing and a control method therefore. According to one embodiment, the magnetic disk drive includes a magnetic head, a magnetic disk, and a housing containing the magnetic head and the magnetic disk, wherein the housing is filled with a low density gas having a lower density than air. An amount of the low density gas in the housing is estimated and, based on the amount of the low density gas, a flying height of the magnetic head from a surface of the magnetic disk is controlled.
1. A magnetic disk drive including a magnetic head, a magnetic disk, and a housing containing the magnetic head and the magnetic disk, wherein the housing is filled with a low density gas having a lower density than air, the magnetic disk drive comprising:
a heat generating body provided in said housing;
an estimation part for estimating an amount of said low density gas in said housing based on a temperature change rate of said heat generating body; and
a control part for controlling a flying height of said magnetic head from a surface of said magnetic disk based on the amount of said low density gas.
2. A magnetic disk drive according to claim 1 further comprising, as said heat generating body, a voice coil motor which moves said magnetic head relative to said magnetic disk.
3. A magnetic disk drive according to claim 1 , wherein the estimation part measures temperatures of said heat generating body during heating or after heating with a plurality of timings to calculate the temperature change rate of said heat generating body.
4. A magnetic disk drive according to claim 1 further comprising a pressure sensor for detecting an internal pressure of said housing, wherein said estimation part estimates the amount of said low density gas based on a density of said low density gas and the pressure in said housing.
5. A magnetic disk drive according to claim 1 , wherein said estimation part obtains a signal which varies according to a density of said low density gas in said housing and estimates the density of said low density gas based on the signal.
6. A magnetic disk drive according to claim 5 , wherein:
said signal is a signal in which the magnitude of an NRRO component varies according to a density of said low density gas in said housing; and
said estimation part estimates the density of said low density gas based on the magnitude of said NRRO component.
7. A magnetic disk drive according to claim 5 further comprising a spindle motor for rotating said magnetic disk, wherein:
said signal is a signal showing a magnitude of output to said spindle motor; and
said estimation part estimate the density of said low density gas based on the magnitude of the output to said spindle motor.
8. A magnetic disk drive according to claim 5 further comprising a pressure sensor for detecting an internal pressure of said housing,
wherein said estimation part estimates the amount of said low density gas based on the density of said low density gas and the pressure in said housing.
9. A magnetic disk drive according to claim 1 further comprising a pressure sensor for detecting an internal pressure of said housing,
wherein said estimation part estimates the amount of said low density gas based on the pressure in said housing.
10. A magnetic disk drive according to claim 9 ,
wherein said estimation part estimates a density of said low density gas in said housing and, based on the density of the low density gas and the pressure in said housing, estimates the amount of said low density gas.
11. A magnetic disk drive according to claim 1 , wherein said control part increases a flying height of said magnetic head in response to a decrease in the amount of said low density gas.
12. A magnetic disk drive according to claim 1 , wherein said control part controls a flying height of said magnetic head based on a positive change rate and a negative change rate.
13. A magnetic disk drive according to claim 1 further comprising a pressure sensor for detecting an internal pressure of said housing,
wherein said control part controls the flying height of said magnetic head based on the amount of said low density gas and the pressure in said housing.
14. A magnetic disk drive according to claim 1 further comprising a temperature sensor for detecting an internal temperature of said housing,
wherein said control part controls the flying height of said magnetic head based on the amount of said low density gas and the temperature in said housing.
15. A magnetic disk drive according to claim 1 , wherein said control part obtains positional information representing a radial position of said magnetic disk where said magnetic head is positioned and, based on the amount of said low density gas and said positional information, controls the flying height of said magnetic head.
16. A magnetic disk drive according to claim 1 ,
wherein said magnetic head comprises an electric heating body which generates heat when electric power is applied; and
wherein said control part controls the flying height of said magnetic head by controlling the amount of power applied to said electric heating body.
17. A magnetic disk drive according to claim 1 , wherein said low density gas is helium.