Auto centering of disks on a hard disk drive

Details Auto centering of disks on a hard disk drive Auto centering of disks on a hard disk drive

2001-09-04

2004-08-03

Hudspeth, David (Department: 2651)

Dynamic magnetic information storage or retrieval

Automatic control of a recorder mechanism

Controlling the head

C360S073030

Reexamination Certificate

active

06771451

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spindle motor/disk assembly of a hard disk drive.
2. Background Information
Hard disk drives contain a plurality of magnetic heads that are coupled to rotating disks. The heads write and read information by magnetizing and sensing the magnetic fields of the disk surfaces. There have been developed magnetic heads that have a write element for magnetizing the disks and a separate read element for sensing the magnetic fields of the disks. The read element is typically constructed from a magneto-resistive material. The magneto-resistive material has a resistance that varies with the magnetic fields of the disk. Heads with magneto-resistive read elements are commonly referred to as magneto-resistive (MR) heads.
Each head is attached to a flexure arm to create a subassembly commonly referred to as a head gimbal assembly (“HGA”). The HGA's are suspended from an actuator arm. The actuator arm has a voice coil motor that can move the heads across the surfaces of the disks.
The disks are rotated by a spindle motor that is mounted to a base plate of the drive. Each disk has a center opening that slides over a hub of the spindle motor. To allow clearance between the disks and spindle motor the inner diameter of the center opening is larger than the outer diameter of the motor hub. The larger center disk opening creates a space between the disks and the hub. The space may allow the disk to be offset from the center of the spindle motor.
The disks typically contain servo information that is used to locate and maintain the heads on the centers of each track. The servo information is typically written onto the disk during the manufacturing process of the hard disk drive units. The servo information is sometimes written onto the disk with an “off-line” servo writer. Off-lines writers include a spindle motor that spins a disk stack assembly, a plurality of heads coupled to the disks of the assembly, and a servo writing circuit coupled to the heads to write servo information onto the disks.
The disks are stacked onto a chuck that is coupled to the spindle motor. The chuck may have a feature that centers the disk stack with the spindle motor. To provide clearance for the disks, the outer diameter of the chuck is smaller than the inner diameter of the disk. The difference in diameter may allow the disk to be off-center in the servo writer. Offset disks may result in non-concentric tracks on the disk. Non-concentric tracks may increase the seek and servo routines of the drive, thereby degrading the performance of the disk drive.
BRIEF SUMMARY OF THE INVENTION
A method for assembling a disk stack assembly that has at least one disk. The method includes initially applying a torque to the disk stack assembly that is less than an operating torque and then spinning the disk stack at a speed that is less than an operating speed of the disk. A force is applied to the disk stack while the disk is spinning. The disk is then spun down and the operating torque is applied to the disk stack assembly.


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