Disk drive apparatus and read error recovery method in a disk drive apparatus

• US 5,754,355 A
• Filed: 04/17/1996
• Issued: 05/19/1998
• Est. Priority Date: 09/21/1995
• Status: Expired due to Term

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: International Business Machines Corporation
• Inventors: Nakajima, Michio, Suda, Katsumi, Nakamura, Takashi, Ogasawara, Kenji, Yoneda, Isao, Tsuwako, Kazushi, Harako, Fujio, Yokoe, Yuji
• Primary Examiner(s): Sniezek, Andrew L.
• Application Number:
  US08/633,596
• Time in Patent Office: 762 Days
• Field of Search: 360/75, 360/73.03, 360/137, 360/73.01, 360/70, 360/31, 360/105, 360/109, 360/113, 360/53, 360/78.04, 360/78.08, 360/78.14
• US Class Current: 360/73.03
• CPC Class Codes: G11B 19/04 Arrangements for preventing, inhibiting, or warning against double recording on the same blank or against other recording or reproducing malfunctions
• CPC Class Codes: G11B 19/20 Driving; Starting; Stopping; Control thereof
• CPC Class Codes: G11B 2005/0016 of magnetoresistive transducers
• CPC Class Codes: G11B 23/505 of disk carriers
• CPC Class Codes: G11B 5/6005 Specially adapted for spacing from a rotating disc using a fluid cushion

Abstract

A disk drive apparatus and read error recovery method in a disk drive apparatus removes thermal asperities on disk surfaces. A projection, such as a thermal asperity, on the recording surfaces of disks is detected when a signal transducer head contacts the projection. The flying height of the signal transducer head is lowered, e.g., by changing the disk rotation speed from the normal rotation speed in read/write operations or by heating a suspension having a bimetal element, while the signal transducer head is positioned over the detected projection on the track. The signal transducer head strikes the projection to break the projection. This avoids a subsequent error from being caused by the thermal asperity.

Claims

1. A disk drive apparatus which rotates a data storage disk and reads data on said disk using a signal transducer head floating at a first flying height over a track on said disk, said disk drive apparatus comprising:

detecting means for detecting a read error in a read signal output from said signal transducer head when said signal transducer head is floating at said first flying height over said track; and

read error recovery means, responsive to said detecting means detecting a read error, for recovering from said read error by reducing the flying height of said signal transducer head from said first flying height while said signal transducer head is floating over said track to make said signal transducer head strike and break a projection on said disk.

2. A disk drive apparatus as recited in claim 1, wherein:

said signal transducer head includes a magnetoresistive (MR) head, and said read error is caused when the temperature of said MR head increases when said signal transducer head contacts said projection.

3. A method of recovering from a read error in a disk drive apparatus which rotates a data storage disk and reads data on said disk using a signal transducer head floating at a first flying height over a track on said disk, said method comprising the steps of:

detecting a read error in a read signal output from said signal transducer head when said signal transducer head is floating at said first flying height over said track; and

reducing the flying height of said signal transducer head, in response to detecting said read error, from said first flying height while said signal transducer head is floating over said track to make said signal transducer head strike and break a projection on said disk.

4. A disk drive apparatus which rotates a data storage disk and reads data on said disk using a signal transducer head floating over said disk, said signal transducer head floats at a first flying height over a track on said disk when said disk rotates at a normal rotation speed, said disk drive apparatus comprising:

detecting means for detecting a read error in a read signal output from said signal transducer head when said signal transducer head is floating at said first flying height over said track;

read error recovery means, responsive to said detecting means detecting a read error, for recovering from said read error by changing the rotation speed of said disk from said normal rotation speed to another rotation speed while said signal transducer head is floating over said track to reduce the flying height of said signal transducer head from said first flying height and to make said signal transducer head strike and break a projection on said disk;

servo positioning means, responsive to a servo clock signal and to a servo signal output from said signal transducer head in response to servo data on said disk, for positioning said signal transducer head over said track both when the rotation speed of said disk is said normal rotation speed and said another rotation speed; and

servo clock supplying means for supplying said servo clock signal to said servo positioning means and for changing the frequency of said servo clock signal based on the rotation speed of said disk.

5. A disk drive apparatus as recited in claim 4, wherein:

said read error is caused by said signal transducer head contacting said projection, and wherein said projection is a thermal asperity.

6. A disk drive apparatus as recited in claim 4, wherein:

said signal transducer head is a positive pressure signal transducer head, wherein said flying height of said positive pressure signal transducer head increases as the rotation speed of said disk increases; and

said read error recovery means reduces the rotation speed of said disk from said normal rotation speed.

7. A disk drive apparatus as recited in claim 5, wherein:

said signal transducer head is a positive pressure signal transducer head, wherein said flying height of said positive pressure signal transducer head increases as the rotation speed of said disk increases; and

said read error recovery means reduces the rotation speed of said disk from said normal rotation speed.

8. A disk drive apparatus, comprising:

a spindle motor for rotating a data storage disk at a normal rotation speed and another rotation speed;

a voice coil motor for moving a signal transducer head over a track of said disk, said signal transducer head floats at a first flying height over said disk when said spindle motor rotates said disk at said normal rotation speed;

a signal processing circuit for detecting a read error in a read signal output from said signal transducer head when said signal transducer head is floating at said first flying height over said track on said disk;

a controller, responsive to said signal processing circuit detecting a read error, for changing the rotation speed of said disk from said normal rotation speed to said another rotation speed while said signal transducer head is floating over said track to reduce the flying height of said signal transducer head from said first flying height and to make said signal transducer head strike and break a projection on said disk;

a servo information processing circuit, responsive to a servo clock signal and to a servo signal output from said signal transducer head in response to servo data on said disk, for positioning said signal transducer head over said track both when the rotation speed of said disk is said normal rotation speed and said another rotation speed; and

a servo clock source for supplying said servo clock signal to said servo information processing circuit and for changing the frequency of said servo clock signal based on the rotation speed of said disk.

9. A controller for a disk drive apparatus which rotates a data storage disk and reads data on said disk using a signal transducer head floating over said disk, said signal transducer head floats at a first flying height over a track on said disk when said disk rotates at a normal rotation speed, said disk drive apparatus includes detecting means for detecting a read error in a read signal output from said signal transducer head when said transducer is floating at said first flying height over said track on said disk, said controller comprising:

speed changing means, responsive to said detecting means detecting a read error, for changing the rotation speed of said disk from said normal rotation speed to another rotation speed while said signal transducer head is floating over said track to reduce the flying height of said signal transducer head from said first flying height and to make said signal transducer head strike and break a projection on said disk;

servo positioning means, responsive to a servo clock signal and to a servo signal output from said signal transducer head in response to servo data on said disk, for positioning said signal transducer head over said track both when the rotation speed of said disk is said normal rotation speed and said another rotation speed; and

means for changing the frequency of said servo clock signal based on the rotation speed of said disk.

10. A method for recovering from read errors in disk drive apparatus which rotates a data storage disk and reads data on said disk using a signal transducer head floating over said disk, said signal transducer head floats at a first flying height over a track on said disk when said disk rotates at a normal rotation speed, said method comprising the steps of:

detecting a read error in a read signal output from said signal transducer head when said transducer is floating at said first flying height over said track on said disk;

changing the rotation speed of said disk, when said read error is detected, from said normal rotation speed to another rotation speed while said signal transducer head is floating over said track to reduce the flying height of said signal transducer head from said first flying height and to make said signal transducer head strike and break a projection on said disk;

positioning said signal transducer head over said track both when the rotation speed of said disk is said normal rotation speed and said another rotation speed based on a servo clock signal and on a servo signal output from said signal transducer head in response to servo data on said disk; and

changing the frequency of said servo clock signal based on the rotation speed of said disk.

11. A method for recovering from read errors as recited in claim 10, wherein said read error is caused by said signal transducer head contacting said projection, said projection being a thermal asperity, said step of changing the rotation speed of said disk including the substep of said signal transducer head striking and breaking said thermal asperity.

12. A method for recovering from read errors as recited in claim 10, wherein said signal transducer head is a positive pressure signal transducer head, wherein said flying height of said positive pressure signal transducer head increases as the rotation speed of said disk increases, said step of changing the rotation speed of said disk including the substep of reducing said rotation speed of said disk from said normal rotation speed.

13. A method for recovering from read errors as recited in claim 11, wherein said signal transducer head is a positive pressure signal transducer head, wherein said flying height of said positive pressure signal transducer head increases as the rotation speed of said disk increases, said step of changing the rotation speed of said disk including the substep of reducing said rotation speed of said disk from said normal rotation speed.

14. A disk drive apparatus which rotates a data storage disk and reads data on said disk using a signal transducer head floating over said disk, said signal transducer head floats at a first flying height over a track on said disk, said disk drive apparatus comprising:

detecting means for detecting a read error in a read signal output from said signal transducer head when said signal transducer head is floating at said first flying height over said track;

a suspension supporting said signal transducer head, said suspension including a bimetal element and a heating element for heating said bimetal element, said bimetal element being arranged to reduce the flying height of said signal transducer head when heated by said heating element; and

read error recovery means, responsive to said detecting means detecting a read error, for recovering from said read error by activating said heating element to reduce the flying height of said signal transducer head from said first flying height while said signal transducer head is floating over said track and to make said signal transducer head strike and break a projection on said disk.

15. A method for recovering from read errors in a disk drive apparatus which rotates a data storage disk and reads data on said disk using a signal transducer head floating over said disk, said signal transducer head floats at a first flying height over a track on said disk, said disk drive apparatus including a suspension supporting said signal transducer head, said suspension including a bimetal element and a heating element for heating said bimetal element, said bimetal element being arranged to reduce the flying height of said signal transducer head when heated by said heating element, said method comprising the steps of:

detecting a read error in a read signal output from said signal transducer head when said signal transducer head is floating at said first flying height over said track; and

activating said heating element, in response to said detecting means detecting said read error, to reduce the flying height of said signal transducer head from said first flying height while said signal transducer head is floating over said track and to make said signal transducer head strike and break a projection on said disk.