Scheduled load of heads to reduce lubricant migration on pole tip and decrease time to ready

• US 9,064,542 B1
• Filed: 05/28/2013
• Issued: 06/23/2015
• Est. Priority Date: 04/08/2013
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Brunner, Ralf
• Primary Examiner(s): Wong, K.
• Application Number:
  US13/903,464
• Time in Patent Office: 756 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G11B 5/40 Protective measures on heads, e.g. against excessive temperature G11B5/31 takes precedence; protection against wear G11B5/255 ; protective structure of the head: see under structures, e.g. G11B5/3106
• CPC Class Codes: G11B 5/54 with provision for moving the head into or out of its operative position or across tracks

Abstract

A disk drive includes: a disk, a head, and control circuitry including a servo control system operable to actuate the head. The head is unloaded onto a ramp for a period of time based on a time constant. The head is loaded onto the disk after the period of time has elapsed and head-media spacing (HMS) is repeatedly measured. The head is unloaded when the HMS measurements become constant within a predetermined range.

Claims

1. A disk drive comprising:

a disk media;

a head; and

control circuitry comprising a servo control system configured to actuate the head for reduction of lubricant migration, the control circuitry configured to;

unload the head onto a ramp for a period of time based on a time constant;

load the head onto the disk after the period of time has elapsed;

repeatedly measure head-media spacing (HMS) until HMS measurements become constant within a predetermined range; and

unload the head when the HMS measurements become constant within a predetermined range.

2. The disk drive of claim 1, wherein the control circuitry is further configured to update the time constant based on a time taken for the HMS measurements to become constant within the predetermined range.

3. The disk drive of claim 2, wherein the control circuitry is configured to unload the head when the HMS measurements become constant within the predetermined range for another period of time based on the updated time constant.

4. The disk drive of claim 1, wherein the control circuitry is configured to measure HMS by comparison of a read back signal strength from the head with a baseline read back signal strength.

5. The disk drive of claim 1, wherein the control circuitry is configured to update the time constant based on one or more environmental conditions.

6. The disk drive of claim 1, wherein the period of time is configured to be less than three hours.

7. The disk drive of claim 1, wherein the control circuitry is further configured to update a predetermined baseline HMS after the head is loaded for another period of time and repeatedly measure the HMS until the HMS measurements become constant.

8. The disk drive of claim 7, wherein the another period of time is at least thirty minutes.

9. A method for mitigating lubricant migration onto a pole area of a slider in a hard disk drive (HDD), the method comprising:

unloading a head of the HDD onto a ramp for a period of time based on a time constant;

loading the head onto a disk media of the HDD after the period of time has elapsed;

repeatedly measuring head-media spacing (HMS) until HMS measurements become constant within a predetermined range; and

unloading the head when the HMS measurements become constant within the predetermined range.

10. The method of claim 9, further comprising updating the time constant based on a time taken for the HMS measurements to become constant within the predetermined range.

11. The method of claim 10, wherein the unloading the head when the HMS measurements become constant within the predetermined range is for another period of time based on the updated time constant.

12. The method of claim 9, wherein the measuring HMS comprises comparing a read back signal strength from the head with a baseline read back signal strength.

13. The method of claim 9, further comprising updating the time constant based on one or more environmental conditions.

14. The method of claim 9, wherein the period of time is configured to be less than three hours.

15. The method of claim 9, further comprising updating a predetermined baseline HMS after the head is loaded for another period of time and repeatedly measuring the HMS until the HMS measurements become constant.

16. The method of claim 15, wherein the another period of time is at least thirty minutes.

17. A control circuitry configured to actuate a head of a hard disk drive (HDD) for reduction of lubricant migration, the control circuitry configured to:

unload the head of the hard disk drive (HDD) onto a ramp for a period of time based on a time constant;

load the head onto a disk media of the HDD after the period of time has elapsed;

repeatedly measure head-media spacing (HMS) until HMS measurements become constant within a predetermined range; and

unload the head when the HMS measurements become constant within a predetermined range.

18. The control circuitry of claim 17, wherein the control circuitry is further configured to update the time constant based on a time taken for the HMS measurements to become constant within the predetermined range.

19. The control circuitry of claim 18, wherein the control circuitry is configured to unload the head when the HMS measurements become constant within the predetermined range for another period of time based on the updated time constant.

20. The control circuitry of claim 17, wherein the control circuitry is configured to measure HMS by comparison of a read back signal strength from the head with a baseline read back signal strength.

21. The control circuitry of claim 17, wherein the control circuitry is configured to update the time constant based on one or more environmental conditions.

22. The control circuitry of claim 17, wherein the period of time is configured to be less than three hours.

23. The control circuitry of claim 17, wherein the control circuitry is further configured to update a predetermined baseline HMS after the head is loaded for another period of time, and repeatedly measure the HMS until the HMS measurements become constant.

24. The control circuitry of claim 23, wherein the another period of time is at least thirty minutes.