Magnetic disk drive with flying height control system
View Patent ↗Embodiments of the invention appropriately control the flying height of a magnetic head slider as necessary without making the magnetic head slider touch the magnetic disk. In one embodiment, when a magnetic disk drive is started, the level of electric power predefined for the ordinary temperature (room temperature) is read in from the internal memory of an MPU. A temperature sensor measures the internal temperature of the magnetic disk drive and sends it to the MPU. According to the temperature sent from the temperature sensor, the MPU calculates the level of electric power which should be applied to a flying height adjustment structure. According to the calculated electric power, the MPU increases or decreases the electric power applied to the flying height adjustment structure. At a flying height controlled (corrected) by the flying height adjustment structure, a magnetic head slider performs read/write on a magnetic disk.
1. A magnetic head slider flying height control method for a magnetic disk drive comprising a magnetic disk; a magnetic head slider which flies low above the magnetic disk to write or read magnetic information thereon; and a flying height adjustment structure provided with a heat source placed near the read/write element of the magnetic head slider to control the flying height of the magnetic head slider, said method comprising:
detecting the temperature of the magnetic disk drive;
calculating the amount of deformation of the read/write element relative to the magnetic head slider at the detected temperature;
calculating the level of electric power which compensates for the amount of deformation calculated; and
applying the calculated level of electric power to the flying height adjustment structure;
wherein the amount of deformation is the amount of protrusion or the amount of retreat, and
wherein provided that the ratio of the change in the amount of protrusion of the read/write element to the change in the detected temperature is i nm/° C. and the ratio of the change in the flying height to the change in the electric power applied to the flying height adjustment structure is I nm/mW, if the temperature rises to T° from start temperature t° C., the electric power applied to the flying height adjustment structure is decreased by i(T−t)/I.
2. A magnetic head slider flying height control method according to claim 1 , wherein the temperature of the magnetic disk drive is the internal temperature of the magnetic disk drive.
3. A magnetic head slider flying height control method according to claim 1 , wherein the temperature of the magnetic disk drive is the temperature near the read/write element.
4. A magnetic head slider flying height control method for a magnetic disk drive comprising a magnetic disk; a magnetic head slider which flies low above the magnetic disk to write or read magnetic information thereon; and a flying height adjustment structure provided with a heat source placed near the read/write element of the magnetic head slider to control the flying height of the magnetic head slider, said method comprising:
detecting the temperature of the magnetic disk drive;
calculating the amount of deformation of the read/write element relative to the magnetic head slider at the detected temperature;
calculating the level of electric power which compensates for the amount of deformation calculated; and
applying the calculated level of electric power to the flying height adjustment structure;
wherein the amount of deformation is the amount of protrusion or the amount of retreat, and
wherein provided that the ratio of the change in the amount of retreat of the read/write element to the change in the detected temperature is i nm/° C. and the ratio of the change in the flying height to the change in the electric power applied to the flying height adjustment structure is I nm/mW, if the temperature rises to T° C. from start temperature t° C., the electric power applied to the flying height adjustment structure is increased by i(T−t)/I.
5. A magnetic disk drive comprising:
a magnetic disk;
a magnetic head slider which flies low above the magnetic disk to write or read magnetic information thereon;
a flying height adjustment structure provided with a heat source placed near the read/write element of the magnetic head slider to control the flying height of the magnetic head slider;
a temperature detecting sensor; and
a control unit;
wherein said control unit, based on the temperature detected by the temperature detecting sensor, calculates the amount of deformation of the read/write element relative to the magnetic head slider; calculates the level of electric power which compensates for the amount of deformation calculated; and applies the calculated level of electric power to the flying height adjustment structure; and
wherein the amount of deformation is the amount of protrusion or the amount of retreat; and
wherein the control unit is configured to decrease the electric power supplied to the flying height adjustment structure by i(T−t)/I, if the temperature rises to T< C. from start temperature t< C., provided that the ratio of the change in the amount of protrusion of the read/write element to the change in the detected temperature is i nm/° C. and the ratio of the change in the flying height to the change in the electric power applied to the flying height adjustment structure is I nm/mW.
6. A magnetic disk drive comprising:
a magnetic disk;
a magnetic head slider which flies low above the magnetic disk to write or read magnetic information thereon;
a flying height adjustment structure provided with a heat source placed near the read/write element of the magnetic head slider to control the flying height of the magnetic head slider;
a temperature detecting sensor; and
a control unit;
wherein said control unit, based on the temperature detected by the temperature detecting sensor, calculates the amount of deformation of the read/write element relative to the magnetic head slider; calculates the level of electric power which compensates for the amount of deformation calculated; and applies the calculated level of electric power to the flying height adjustment structure; and
wherein the amount of deformation is the amount of protrusion or the amount of retreat; and
wherein the control unit is configured to increase the electric power supplied to the flying height adjustment structure by i(T−t)/I, if the temperature rises to T< C. from start temperature t° C., provided that the ratio of the change in the amount of retreat of the read/write element to the change in the detected temperature is i nm/° C. and the ratio of the change in the flying height to the change in the electric power applied to the flying height adjustment structure is I nm/mW.
7. A magnetic disk drive according to claim 6 , wherein the temperature sensor is provided on a control circuit board having the control unit mounted thereon.
8. A magnetic disk drive according to claim 6 , wherein the temperature sensor is provided in the magnetic disk drive.
9. A magnetic disk drive according to claim 6 , wherein the temperature sensor is provided on the magnetic head slider.
10. A magnetic disk drive according to claim 6 , wherein the temperature sensor detects the temperature of the read/write element from the change of the resistance of the read/write element.