Storage device, control method, control device, and program

Abstract

A heater for changing a projection distance protrusion value by thermal expansion accompanying electric-power-distributed heating is provided in a head having at least a reading element. At desired correction timing, a changed distance detection unit measures a clearance changed distance in a state in which the head is positioned to a track on the recording medium while increasing the amount of electric power distributed to the heater. A contact determination unit determines that the head is brought into contact with the recording medium when a derivative value of the clearance changed distance is below a predetermined threshold value. A measurement output unit outputs the clearance changed distance detected by the changed distance detection unit at the time of contact determination of the contact determination unit as a measurement result of the clearance between the reading element and the recording medium.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are block diagrams of a magnetic dick device showing an embodiment of a storage device according to the present invention;

FIG. 2 is an explanatory diagram of a mechanical structure of the magnetic disk device according tot he present embodiment;

FIGS. 3A and 3B are explanatory drawings of a head structure of the present embodiment;

FIG. 4 is a block diagram showing details of a functional configuration of an MPU in the present embodiment;

FIG. 5 is an explanatory diagram of a clearance control information table used in the present embodiment;

FIG. 6 is a flow chart of an overall processing operation of the present embodiment;

FIG. 7 is a flow chart showing details of the self correction process of step s2 of FIG. 6;

FIG. 8 is a flow chart showing details of the clearance control information measurement process of step s5 of FIG. 7;

FIG. 9 is a flow chart showing details of the clearance measurement process of step s3 of FIG. 8 using the space loss method of Wallace spacing loss;

FIG. 10 is an explanatory diagram of measurement track for performing clearance measurement;

FIG. 11 is a block diagram of a circuit unit for detecting amplitudes of preamble read signals;

FIG. 12 is an explanatory diagram schematically showing head projection distance protrusion values accompanying heating of electric-power-distributed heater;

FIG. 13 is a graph diagram of clearance changed distances measured along with increase of electric power distribution amount of the heater and derivative values;

FIGS. 14A and 14B are flow charts of the clearance measurement process of step s3 of FIG. 8 using HRF method;

FIG. 15 is an explanatory diagram of measurement-dedicated track used in the HRF method;

FIG. 16 is a flow chart of the projection transition time measurement process of step 5 of FIG. 8;

FIGS. 17A to 17C are explanatory diagrams of variation of read signal amplitude and clearance changed distance with respect to frame position along with heater electric power distribution;

FIG. 18 is a flow chart of the recording current projection distance protrusion value measurement process of step s6 of FIG. 8;

FIG. 19 is a flow chart of temperature correction coefficient measurement process of step s7 of FIG. 8;

FIG. 20 is a graph diagram showing variation of clearance and heater projection sensitivity protrusion sensitivity with respect to device temperature;

FIG. 21 is a flow chart of the write clearance control process of step S6 of FIG. 6;

FIG. 22 is a flow chart of the read clearance control process of step S10 of FIG. 6;

FIG. 23 is an explanatory diagram of a track of an embodiment in which clearance is measured and recorded for each track;

FIGS. 24A and 24B are flow charts of a clearance measurement process in which clearance is measured and written in track unit;

FIG. 25 is a flow chart of a write clearance control process performed by reading clearance recorded in track; and

FIG. 26 is a flow chart of a read clearance control process performed by reading clearance recorded in track.

Claims

1. A storage device characterized by having a head having at least a reading element and provided with a heater for changing a projection distance protrusion value by thermal expansion accompanying electric-power-distributed heating for accessing data by floating above a rotating recording medium; a changed distance detection unit for measuring a clearance changed distance between the reading element and the recording medium in a state in which the head is positioned to a track on the recording medium while increasing the amount of electric power distributed to the heater; a contact determination unit for determining that the head is brought into contact with the recording medium when a derivative value of the clearance changed distance is below a predetermined threshold value; and a measurement output unit for outputting the clearance changed distance detected by the changed distance detection unit at the time of contact determination of the contact determination unit as a measurement result of the clearance between the reading element and the recording medium.

2. The storage device according to claim 1, characterized in that the changed distance detection unit measures, as the changed distance of the clearance, amplitude of a read signal from a preamble part in a servo area in each frame of the recording medium by the reading element while increasing the amount of the electric power distributed to the heater; the contact determination unit determines that the head is in contact with the recording medium when the derivative value of the amplitude is below a predetermined threshold value; and the measurement output unit calculates the clearance from the amplitude at the point of the contact determination and outputs the clearance as the measurement result.

3. The storage device according to claim 1, characterized in that the changed distance detection unit has an amplitude detection unit for detecting amplitude of a read signal from a preamble part in a servo area of a frame of the recording medium by the reading element in a state in which the head is positioned to an arbitrary measurement objective track, an initial amplitude retaining unit for retaining initial amplitude Vo detected by the amplitude detection unit before the electric power is distributed to the heater, a measured amplitude retaining unit for retaining measured amplitude Vi detected by the amplitude detection unit upon measurement when electric power is distributed to the heater, and a calculating unit for calculating the clearance changed distance d as

4. The storage device according to claim 3, characterized in that the amplitude detection unit detects the amplitude of the read signal from an automatic gain control signal with respect to a variable gain amplifier for amplifying the read signal obtained from the reading element.

5. The storage device according to claim 1 characterized in that the changed distance measurement unit has a pattern reading unit for positioning the head to a predetermined measurement-dedicated track in which a repeated pattern of a predetermined frequency is recorded in a user data part and modulating the read signal of the repeated pattern; an amplitude detection unit for detecting basic frequency amplitude V (f) and third harmonic wave amplitude V (3f) of the read signal; an initial amplitude retaining unit for retaining the basic frequency amplitude Vo (f) and the third harmonic wave amplitude Vo (3f) detected by the amplitude detection unit before electric power is distributed to the heater; an initial amplitude ratio calculating unit for calculating an initial amplitude ratio Ro of the basic frequency and the third harmonic wave retained in the initial amplitude retaining unit as

6. The storage device according to claim 5, characterized in that, in the measurement-dedicated track, a repeated pattern having a recording wavelength that is 10 to 20 times the basic recording wavelength of user data is recorded in the user data area of each frame.

7. The storage device according to claim 1, characterized in that the recording medium is divided into a plurality of zones in a radial direction, and the measurement output unit writes the clearance measured for each of the zones to a system area of the recording medium.

8. The storage device according to claim 1, characterized in that the measurement output unit writes the clearance measured for each track of the recording medium to a clearance information area provided in a servo area of each frame.

9. A control method of a storage device having a head having at least a reading element and provided with a heater for changing a projection distance protrusion value by thermal expansion accompanying electric-power-distributed heating for reading/writing data by floating above a rotating recording medium; the control method of the storage device having a changed distance detection step of measuring a clearance changed distance between the reading element and the recording medium in a state in which the head is positioned to a track on the recording medium while increasing the amount of electric power distributed to the heater; a contact determination step of determining that the head is brought into contact with the recording medium when a derivative value of the clearance changed distance is below a predetermined threshold value; and a measurement output step of outputting the clearance changed distance detected in the changed distance detection step at the time of contact determination of the contact determination step as a measurement result of the clearance between the reading element and the recording medium.

10. The control method according to claim 9, characterized in that, in the changed distance detection step, amplitude of a read signal from a preamble part in a servo area in each frame of the recording medium is measured as the changed distance of the clearance by the reading element while increasing the amount of the electric power distributed to the heater; in the contact determination step, the head is determined to be in contact with the recording medium when the derivative value of the amplitude is below a predetermined threshold value; and, in the measurement output step, the clearance is calculated from the amplitude at the point of the contact determination and output as the measurement result.

11. The control method according to claim 9, characterized in that the changed distance detection step has an amplitude detection step of detecting amplitude of a read signal of a preamble part in a servo part area of a frame of the recording medium by the reading element in a state in which the head is positioned to an arbitrary measurement objective track, an initial amplitude retaining step of retaining initial amplitude Vo detected in the amplitude detection step before the electric power is distributed to the heater, a measured amplitude retaining step of retaining measured amplitude Vi detected in the amplitude detection step upon measurement when electric power is distributed to the heater, and a calculating step of calculating the clearance changed distance d as

12. The control method according to claim 9 characterized in that the changed distance detection step has a pattern reading step of positioning the head to a predetermined measurement-dedicated track in which a repeated pattern of a predetermined frequency is recorded in a user data step and modulating the read signal of the repeated pattern; an amplitude detection step of detecting basic frequency amplitude V (f) and third harmonic wave amplitude V (3f) of the read signal; an initial amplitude retaining step of retaining the basic frequency amplitude Vo (f) and the third harmonic wave amplitude Vo (3f) detected in the amplitude detection step before electric power is distributed to the heater; an initial amplitude ratio calculating step of calculating an initial amplitude ratio Ro of the basic frequency and the third harmonic wave retained in the initial amplitude retaining step as

12. The control method according to claim 11, characterized in that, in the measurement-dedicated track, a repeated pattern having a recording wavelength that is 10 to 20 times the basic recording wavelength of user data is recorded in the user data area of each frame.

13. A control device of a storage device having a head having at least a reading element and provided with a heater for changing a projection distance protrusion value by thermal expansion accompanying electric-power-distributed heating for accessing data by floating above a rotating recording medium; characterized by having a changed distance detection unit for measuring a clearance changed distance between the reading element and the recording medium in a state in which the head is positioned to a track on the recording medium while increasing the amount of electric power distributed to the heater; a contact determination unit for determining that the head is brought into contact with the recording medium when a derivative value of the clearance changed distance is below a predetermined threshold value; and a measurement output unit for outputting the clearance changed distance detected by the changed distance detection unit at the time of contact determination of the contact determination unit as a measurement result of the clearance between the reading element and the recording medium.

14. The control device according to claim 13, characterized in that the changed distance detection unit measures, as the changed distance of the clearance, amplitude of a read signal from a preamble part in a servo area in each frame of the recording medium by the reading element while increasing the amount of the electric power distributed to the heater; the contact determination unit determines that the head is in contact with the recording medium when the derivative value of the amplitude is below a predetermined threshold value; and the measurement output unit calculates the clearance from the amplitude at the point of the contact determination and outputs the clearance as the measurement result.

15. The control device according to claim 13, characterized in that the changed distance detection unit has an amplitude detection unit for detecting amplitude of a read signal from a preamble part in a servo area of a frame of the recording medium by the reading element in a state in which the head is positioned to an arbitrary measurement objective track, an initial amplitude retaining unit for retaining initial amplitude Vo detected by the amplitude detection unit before the electric power is distributed to the heater, a measured amplitude retaining unit for retaining measured amplitude Vi detected by the amplitude detection unit upon measurement when electric power is distributed to the heater, and a calculating unit for calculating the clearance changed distance d as

16. The control device described in claim 15, characterized in that the amplitude detection unit detects the amplitude of the read signal from an automatic gain control signal with respect to a variable gain amplifier for amplifying the read signal obtained from the reading element.

17. The control device according to claim 13 characterized in that the changed distance measurement unit has a pattern reading unit for positioning the head to a predetermined measurement-dedicated track in which a repeated pattern of a predetermined frequency is recorded in a user data part and modulating the read signal of the repeated pattern; an amplitude detection unit for detecting basic frequency amplitude V (f) and third harmonic wave amplitude V (3f) of the read signal; an initial amplitude retaining unit for retaining the basic frequency amplitude Vo (f) and the third harmonic wave amplitude Vo (3f) detected by the amplitude detection unit before electric power is distributed to the heater; an initial amplitude ratio calculating unit for calculating an initial amplitude ratio Ro of the basic frequency and the third harmonic wave retained in the initial amplitude retaining unit as

18. The control device according to claim 13, characterized in that the recording medium is divided into a plurality of zones in a radial direction, and the measurement output unit writes the clearance measured for each of the zones to a system area of the recording medium. 19. The control device according to claim 13, characterized in that the measurement output unit writes the clearance measured for each track of the recording medium to a clearance information area provided in a servo area of each frame.

20. A computer-readable storage medium which stores a program characterized by causing a computer of a storage device having a head having at least a reading element and provided with a heater for changing a projection distance protrusion value by thermal expansion accompanying electric-power-distributed heating for accessing data by floating above a rotating recording medium, to execute a changed distance detection step of measuring a clearance changed distance in a state in which the head is positioned to a track on the recording medium while increasing the amount of electric power distributed to the heater; a contact determination step of determining that the head is brought into contact with the recording medium when a derivative value of the clearance changed distance is below a predetermined threshold value; and a measurement output step of outputting the clearance changed distance detected by the changed distance detection unit at the time of contact determination of the contact determination unit as a measurement result of the clearance between the reading element and the recording medium.