Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Reexamination Certificate
2000-12-29
2004-05-18
Chen, Tianjie (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
C360S265700, C360S265900
Reexamination Certificate
active
06738229
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to disk drives for storing data. More specifically, the present invention relates to a head stack assembly and an E-block that decrease track misregistration.
BACKGROUND
Disk drives are widely used in computers and data processing systems for storing information in digital form. These disk drives commonly use one or more rotating storage disks to store data in digital form. Each storage disk typically includes a data storage surface on each side of the storage disk. These storage surfaces are divided into a plurality of narrow, annular, regions of different radii, commonly referred to as “tracks”. Typically, an E-block having one or more actuator arms is used to position a data transducer proximate each data storage surface of each storage disk. Each data transducer is secured to one actuator arm with a suspension assembly. The data transducer is positioned at a target track on the storage surface in order to access information from, or transfer information to, the storage disk. The E-block is moved with an actuator motor relative to the storage disks. Depending upon the design of the disk drive, each actuator arm can retain one or two transducer assemblies.
The accurate and stable positioning of each data transducer near each data storage surface is critical to the transfer and retrieval of information from the disks. As a result thereof, vibration in the E-block, the suspension assemblies and the storage disks can cause errors in data transfers due to inaccuracies in the positioning of the data transducers relative to the storage disks. This is commonly referred to as “track misregistration.” The desire to increase performance characteristics of disk drives has resulted in increased rotational velocity of storage disks. Unfortunately, as disk speeds increase, aerodynamic forces also increase. This causes the storage disks to vibrate in the vertical direction, commonly referred to as “out-of-plane” movements. Such movements can result in an increased difficulty of maintaining the data transducer on the target track and increased inaccuracies in data transfers.
Further, the E-block, suspension assemblies, and the storage disks have modes of vibrations that cause track misregistration. Some of these modes of vibration are prevalent due to the existence of a kinematic relationship between the actuator arms, the suspension assemblies and the storage disks. More specifically, as the storage disk moves vertically because of out-of-plane irregularities of the storage disk, the suspension assembly hinges and the data transducer moves with respect to the surface of the storage disk. This off-track motion is extremely difficult or impossible to follow with the actuator motor.
Moreover, the vibrational forces on the storage disks cause the storage disks to deviate from its usual rotational plane and displacement of the data transducer from the target track. This displacement occurs in both an out-of-plane direction, as well as in a radial direction. The data transducer attempts to follow the disk contour, but in so doing, the data transducer moves off-track, resulting in track misregistration. Therefore, the radial and out-of-plane movements are said to be “coupled” to the track misregistration parameter. Such coupling occurs in disk drives where the storage disks and the actuator arms rotate in parallel planes.
A detailed description of the various problems associated with track misregistration due to vibration of the E-block, suspension assemblies, and out-of-plane motion of the storage disks is provided in U.S. Pat. No. 6,088,192, issued to Riener et al., and assigned to Quantum Corporation, the assignee of the present invention. The contents of U.S. Pat. No. 6,088,192 are incorporated herein by reference.
One attempt to reduce off track motion of the data transducer includes angling the suspension assembly and the data transducer in a roll direction. However, the arm bending mode of the E-block introduces an off-track component that is not significantly impacted by providing a roll angle to the suspension assembly and the data transducer.
Another attempt to minimize off track motion of the data transducer involves using thicker storage disks to minimize disk vibration. However, this design results in a greater thickness of the overall disk drive, and increased costs in manufacturing the disk drive.
Yet another attempt to reduce off track motion of the data transducer includes the addition of microactuators to adjust the position of the data transducers to compensate for the movements of the data transducers relative to the target track. Unfortunately, the addition of microactuators is costly, and further adds another level of complexity to the disk drive. Moreover, microactuators and the necessary electrical circuitry can require additional space within the drive housing, which can make such implementation difficult.
Still another attempt includes the addition of baffles to disrupt airflow across the actuator arms, the suspension assemblies, and disk motion induced by air turbulence. Unfortunately, this design is also not completely satisfactory.
In light of the above, there is the need for a disk drive, head stack assembly, and an E-block that minimizes track misregistration. Additionally, there is a need to provide an E-block having improved vibration and resonance characteristics, and which improves the performance of the disk drive. Further, there is a need for a head stack assembly that closely and accurately follows a data track despite out-of-plane disk motion, vibration of the actuator arms and/or vibration of the suspension assemblies. Moreover, there is a need for a head stack assembly having improved track-following characteristics that are relatively easy and inexpensive to manufacture.
SUMMARY
The present invention is directed to an E-block and a head stack assembly for a disk drive. The E-block includes an actuator hub and a first actuator arm secured to the actuator hub. The first actuator arm maintains a first data transducer near a first storage disk. Uniquely, the first actuator arm has a roll-bias angle along the majority of the length of the first actuator arm. The roll-bias angle has an absolute value of greater than zero degrees relative to the first storage disk. Preferably, the roll-bias angle is incorporated into substantially the entire length of the first actuator arm.
Importantly, by incorporating the roll-bias angle into the majority of the length of the first actuator arm, vibration of the first actuator arm and out-of-plane motion of the rotating first storage disk will have a reduced effect on the accurate positioning of the first data transducer relative to the first storage disk.
As used herein, the term “roll-bias angle” refers to the angle formed by the actuator arm relative to the plane of a storage surface of the storage disk. A negative roll-bias angle is present when a spindle side of the actuator arm is closer to the storage surface of the storage disk than a perimeter side of the actuator arm. In other words, the actuator arm is “tilted” toward a disk axis of the storage disk. A positive roll-bias angle occurs when the actuator arm is tilted in the opposite direction, i.e. away from the disk axis of the storage disk.
As used herein, the term “skew angle” refers to the orientation of the actuator arm and the attached data transducer relative to the storage disk. A “zero skew angle” occurs when a longitudinal axis of the actuator arm forms a ninety degree angle with a radial line from the disk axis to the data transducer. At a zero skew angle, the longitudinal axis of the actuator arm is coplanar with a line that is tangent to a curve of the track immediately adjacent to the data transducer. At a zero skew angle, there is no “straining” of the data transducer to remain on track. At a “negative skew angle”, the longitudinal axis of the actuator arm forms an obtuse angle with the radial line from the disk axis to the data transducer, i.e. the data transducer has moved from zero skew
Broder James P.
Chen Tianjie
Maxtor Corporation
Roeder Steven G.
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