Electricity: measuring and testing – Magnetic – Magnetic information storage element testing
Reexamination Certificate
1998-02-10
2001-08-14
Strecker, Gerard R. (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetic information storage element testing
C324S202000, C324S210000, C073S001810, C073S001890, C360S075000, C360S100100, C360S135000, C428S065100
Reexamination Certificate
active
06275029
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention generally relates to a disk drive apparatus and, more particularly, to a method for monitoring the flying height of a read/write transducer head relative to a disk surface.
2. Description of Related Art
Disk drives which are used, for example, in work stations, personal computers and portable computers, are required to provide a large amount of data storage within a minimum physical area. Generally, magnetic media type disk drives operate by positioning a read/write transducer head over tracks on a rotating magnetic storage disk. The positioning of the read/write head is accomplished by employing an actuator arm coupled to control electronics. The control electronics control the positioning of the actuator and the reading and writing functions of the transducer head.
Increasing storage capacity demands are being placed on disk drives. Computer systems are requiring disk drives to have higher storage capacity, while occupying a minimal amount of space within the computer system. In order to accommodate these demands, disk drives are being produced with reduced physical size and increased capacity.
One measure of determining the storage capacity of a disk drive is the flying height of the drive's transducer head above the drive's rotating storage disk. The flying height is the distance between the surface of the disk and the read/write head. In operation, a drive's disk achieves a certain angular velocity after start up of the drive, so that a cushion of air is generated above the disk's surface. This cushion of air forces the read/write head up off the surface of the disk to achieve a flying height. Having very small flying heights increases a drive's storage capacity, because flying the read/write head very close to the disk surface allows for high data bit density (i.e., the number of data bits per inch on a data track).
The largest data bit density can be obtained when the read/write transducer head contacts the disk surface. However, repeated contact between the read/write head and the disk surface results in damage to the head and disk. Thus, there has been an industry-wide trend to decrease the flying height in a disk drive without causing the read/write head to actually contact the disk surface.
However, as a read/write head flies over a rotating disk, the flying height does not remain constant, but rather tends to fluctuate slightly above and below a normal flying height. When flying heights are small, a variation in the flying height may cause the read/write head to randomly contact the disk surface. This situation is referred to as intermittent contact. Such repeated contact between the read/write head and disk surface can damage the head and disk. This damage can cause drive failures in an extremely short period of time. Such failures can result in the drive's user losing all of the data stored in the drive.
Accordingly, it is desirable to provide for determining whether the flying height of a read/write transducer head in a disk drive is so small that repeated intermittent contact is likely. When manufacturing disk drives, the ability to make such a determination provides for the testing of manufactured drives to ensure that the flying height is sufficiently large. During a disk drive's operation in the field, such a determination could be made to ensure that the drive is still operating with an acceptably large flying height. If the flying height of a user's drive is determined to be too small, the user can then be notified that the drive should be either serviced or replaced.
SUMMARY OF THE INVENTION
In accordance with the present invention, the flying height for a transducer head in a head-disk interface of a disk drive is monitored. By monitoring the flying height, it can be determined whether the flying height is below a predetermined flying height value. If the flying height is determined to be below the predetermined flying height value, then an indication is provided to signal an increased likelihood of the head contacting the surface of the disk in the head-disk interface.
In order to provide for monitoring the spacing between the transducer head and disk surface, the disk surface includes a region containing a set of asperities. Each asperity in the set of asperities extends from the disk surface to have a height less than the predetermined flying height value. The transducer head is placed over the region containing the asperities, and the disk is rotated. A determination is then made as to whether the spacing between the head and the disk surface is greater than a height of an asperity in the set of asperities.
In order to make such a determination about the spacing, it is determined whether the head contacts an asperity in the set of asperities. Whether such a contact occurs is determined by retrieving and analyzing a signal pattern provided by the transducer head, while the disk is rotating and the transducer head is positioned over the region containing the asperities. In analyzing the signal pattern, it is determined whether the signal pattern is within a predetermined threshold signal envelope.
If the signal pattern is within the predetermined threshold signal envelope, then the head has not contacted an asperity in the set of asperities. Accordingly, the flying height is acceptably large. If the signal pattern is not within the predetermined threshold signal envelope, then the head has contacted an asperity in the set of asperities. Thus, the flying height is unacceptably small.
REFERENCES:
patent: 4777544 (1988-10-01), Brown et al.
patent: 4828895 (1989-05-01), Bickert et al.
patent: 4841389 (1989-06-01), Hoyt et al.
patent: 4872071 (1989-10-01), Easton et al.
patent: 4931338 (1990-06-01), Toffle
patent: 5062021 (1991-10-01), Ranjan et al.
patent: 5168413 (1992-12-01), Coker et al.
patent: 5410439 (1995-04-01), Egbert et al.
patent: 5473431 (1995-12-01), Hollars et al.
patent: 5640089 (1997-06-01), Horikawa et al.
patent: 5689057 (1997-11-01), Baumgart et al.
patent: 5810477 (1998-09-01), Abraham et al.
patent: 5956217 (1999-09-01), Xuan et al.
patent: 6088176 (2000-07-01), Smith et al.
Gaudet et al; “Head Flight Height Monitoring”, IBM Tech. Discl. Bull., vol. 11 No. 12, p1650, May 1969.*
Blair et al; “Asperity Disk”, IBM Tech. Discl. Bull., vol.21 No. 12, p.4999, May 1979.*
Mackintosh; “A Standard Disk for Calibrating Head-Disk Interference Measuring Equipment”, IEEE Transactions on Magnetics, vol. Mag-18, No. 6, pp 1230-1232, Nov. 1982.
Berger Derek J.
Dempster Shawn B.
Olson Jonathan E.
Seagate Technology LLC
Strecker Gerard R.
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