Dynamic magnetic information storage or retrieval – Record transport with head stationary during transducing – Disk record
Reexamination Certificate
2002-02-12
2004-09-28
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Record transport with head stationary during transducing
Disk record
C360S099120, C360S245200
Reexamination Certificate
active
06798613
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates an apparatus and method for correcting the Z-height, gram load, pitch static attitude and/or the roll static attitude during assembly of a hard disk drive.
BACKGROUND
Magnetic recording hard disk drives are widely used in computers and data processing systems for storing information in digital form. These disk drives commonly include (i) a drive housing having a base and a pivot, (ii) one or more rotating storage disks, (iii) one or more actuator arms that are mounted on the pivot, and (iv) one or more head suspension assemblies. Each storage disk typically includes one or more tracks.
FIG. 1A
illustrates a prior art head actuator assembly
10
P including an actuator hub
12
P, an actuator arm
14
P, and a head suspension assembly
16
P having a load beam
18
P, a slider
20
P, and a flexure
22
P that secures the slider
20
P to the load beam
18
P. The slider
20
P includes an air bearing surface
24
P. The load beam
18
P is bent at an angle &thgr;. As is well known in the art, an additional head suspension assembly (not shown) is typically attached to the bottom surface of the actuator arm
14
P. Further, the head actuator assembly
10
P typically includes a plurality of actuator arms
14
P, each having one or more head suspension assemblies
16
P.
FIG. 1B
illustrates the relationship of a prior art head suspension assembly
16
P to a storage disk
26
P when the storage disk
26
P is not rotating. In this position, the head suspension assembly
16
P is in a “loaded” state. In the loaded state, the load beam
18
P is bent so that the angle &thgr; (illustrated in
FIG. 1A
) is reduced from the angle &thgr; illustrated in FIG.
1
A and the angle &thgr; is typically greater than zero. Because the load beam
18
P resists this deformation, a force, commonly referred to as the gram load, is transmitted to the slider
20
P. The distance between the air bearing surface
24
P of the slider
20
P and a top mounting side
28
P of the actuator arm
14
P is commonly referred to as the Z height.
FIG. 1C
illustrates a prior art view of the load beam
18
P being held in the loaded state by a pin
30
P. In this configuration, an angle &agr; is defined by the air bearing surface
24
P and the top surface
28
P. The angle &agr; is referred to as the pitch static attitude (PSA) of the slider
20
P.
FIG. 1D
illustrates a prior art end view of the head suspension assembly
16
P with the load beam
18
P held in the loaded state. An angle &bgr; is defined by the horizontal tilt of the air bearing surface
24
P of the slider
20
P relative to the top mounting side
28
P of the actuator arm
14
P. The angle &bgr; is referred to as the roll static attitude (RSA) of the slider
20
P. The term “static attitude” is used to describe either the PSA or the RSA, or both parameters together. The load beam
18
P and the flexure
22
P are also illustrated in FIG.
1
D.
FIG. 1E
illustrates a prior art view of the relationship of the head suspension assembly
16
P to the storage disk
26
P when the storage disk
26
P is rotating. The rotation of the storage disk
26
P causes the slider
20
P to ride on an air bearing a distance “h” from the storage disk
26
P. The distance “h” is referred to as the “flying height” of the slider
20
P and represents the position that the slider
20
P occupies when the storage disk
26
P is rotating during normal operation of the disk drive. The load beam
18
P and a portion of the actuator arm
14
P are also illustrated in FIG.
1
E.
The need for increased storage capacity, compact construction, and reduced cost has led to disk drives having fewer storage disks, with each storage disk having increased track density. As track density increases, it is necessary to decrease the flying height of the slider and have tighter control on the flying height. More specifically, if the flying height is not maintained within a certain range, the quality of the data transferred to and from the storage disk is degraded. As a result thereof, accurately controlling the flying height of the slider is critical to the accurate transfer and/or retrieval of information from the storage disk.
The flying height of the slider is influenced by a number of factors, including the rotation speed of the storage disk, the design of the air bearing surfaces of the slider, the pitch static attitude, the roll static attitude, the gram load, and the Z height. For example, the flying height is often higher than nominal if the Z height is higher than nominal. More specifically, when the Z height is higher than nominal, the pitch static attitude is more positive than desired and the gram load is lower than desired. All three of these factors cause an increase in the flying height. This problem is further aggravated if the pitch static attitude is higher than nominal when measured at a nominal Z-height and/or the gram load is lower than nominal when measured at the nominal Z-height.
Accordingly, one way of attempting to achieve the desired flying height includes closely controlling the Z-height. Typically, the Z-height of a disk drive depends on the stack-up of many tolerances, including but not limited to the position of the pivot relative to the base, the pivot height relative to the base, and the thickness and flatness of the actuator arm. Typically, the height of the storage disk relative to the base is very precise. Thus, the Z-height can be controlled by closely controlling the individual dimensions and tolerances that determine the Z-height. In other words, tolerances can be tightened so that the actuator arm is brought to the proper Z-height relative to the disk. However, tightening tolerances increases the cost of manufacturing.
Still another way to achieve the desired flying height includes controlling and adjusting the gram load, the pitch static attitude and the roll static attitude. For example, a laser can be used to adjust the pitch static attitude, the roll static attitude and the gram load after the head suspension assembly has been merged into the storage disks. In this design, a harmonic ratio flying height detector is used to estimate the flying height by writing a signal on the disk having a read back spectrum that is constant along the track and which has nonzero amplitude for at least two different frequencies. If the flying height is estimated to be too high or too low, the laser directs one or more laser beams at the load beam to adjust the pitch static attitude, the roll static attitude and/or the gram load. Subsequently, the harmonic ratio flying height detector is again used to estimate the flying height. If the flying height is again too high or too low, the laser again directs one or more laser beams at the load beam to adjust the pitch static attitude, the roll static attitude and/or the gram load. This process is repeated until the desired flying height is determined by the harmonic ratio flying height detector.
Unfortunately, this process is not very practical because the harmonic ratio flying height detector is not very accurate at measuring the flying height and access to load beams that are merged between the storage disks is extremely limited.
In light of the above, the need exists to provide a way to narrow the distribution of the flying heights, the Z-heights, the gram loads, the pitch static attitudes and the roll static attitudes in a population of disk drives. Another need exists to provide a disk drive with reduced track misregistration. Yet another need exists to provide a disk drive that is relatively easy and cost effective to manufacture.
SUMMARY
The present invention is directed to a disk drive that includes a drive housing, an actuator arm mounted to the drive housing, a head suspension assembly secured to the actuator arm, a spindle secured to the drive housing, a storage disk positioned on the spindle and a spacer positioned on the spindle. The head suspension assembly includes a slider. The actuator arm includes a suspension mounting side and the spindle includes a disk mounting surface. The spacer is positio
Krajnovich Douglas J.
Yogi Tadashi
Broder James P.
Evans Jefferson
Maxtor Corporation
Roeder Steven G.
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