Dynamic magnetic information storage or retrieval – Fluid bearing head support – Disk record
Reexamination Certificate
2000-01-21
2002-11-05
Letscher, George J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Fluid bearing head support
Disk record
Reexamination Certificate
active
06477012
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to magnetic recording devices, specifically, to air bearing sliders for use in a magnetic recording drive. In particular, the present invention relates to a method and apparatus for providing stronger and more broadly distributed negative pressure by using dual cross bars. This invention provides for a stable, static, and dynamic flying attitude with a compensating slider size reduction and a wide variation of skew angles.
2. Description of the Related Art
Magnetic recording systems transfer data through transducers that are supported by an air bearing film or layer as they move relative to the surface of a magnetic recording disk. Such transducers need to either “fly” at just a few micro-inches above a rotating disk surface (flying-type heads), or contact the rotating disk slightly within a safe range of contact pressure (pseudo contact-type heads). The air bearing film is produced by the pressurization of air as it flows between the rotating disk surface and the magnetic head assembly (also called the slider body).
For flying magnetic head assemblies, or flying heads, the air bearing functions to provide, without physical contact, a very thin clearance between the magnetic head assembly and the rotating disk. This minimizes the surface wear and damage to the flying head and the magnetic disk during operation, while maintaining a close separation to ensure a high density magnetic recording structure.
Flying heads thus provide a non-contact transducing mechanism between a magnetic transducer and a fast rotating recording medium. However, to obtain the best data transfer performance without causing serious tribological problems, this requires that a stable, constant spacing be maintained between a flying transducer (on the slider body) and the magnetic recording disk.
As the nominal flying height (the distance between the slider body and the rotating disk surface) of the flying slider decreases, the magnetic transducer achieves a higher resolution between individual data bit locations on the disk. Thus, a close space between the flying slider and the rotating disk, coupled with a very narrow transducer gap and a very thin magnetic recording film, allows for a higher recording capacity with very short wavelength and high frequency features. A constant spacing between the flying head slider body and the disk also minimizes the fluctuations in signal amplitude, thereby optimizing signal resolution. Finally, a constant low flying height over whole data area is the essential factor for an optimized higher density recording process regardless of skew angle variation and increasing rotating disk speed.
Therefore, to achieve a higher recording density the flying height must be reduced as much as possible without causing reliability problems. Problems can occur, however, when excessive and unwanted variations in the flying height result in contact between the flying slider and the rapidly rotating recording medium. Any such contact leads to wear of the slider and the recording surface, and in certain conditions, can be catastrophic to the operation of the disk drive.
Accordingly, development efforts continue to strive for lower and lower flying heights while trying to provide uniform or optimum flying height conditions across a range of flying conditions. Some tactics that are used are tangential velocity variations from the inside to the outside tracks and high speed track seeking movement.
Another way to achieve a high-speed access rate for stored data and to obtain a smaller drive size, is through the use of a rotary actuator rather than a linear actuator. By using a rotary actuator, the airflow under the slider is no longer substantially unidirectional, but varies widely in angle with respect to the longitudinal axis of the slider. The angle of the airflow with respect to the longitudinal axis of the slider is called the skew angle. In accessing the magnetic disks for recording, and playing back from disks using a rotary type actuator, the magnetic transducer continuously experiences air velocity and skew angle variations while moving from one data track to another data track of the disk in response to commands from a VCM controller. Large amount of skew angle and fast accessing movement of rotary actuator can cause a severe reduction of flying height, especially at inner and outer tracks.
Disk circumferential speed increases linearly from the inner diameter (ID) to the outer diameter (OD) of the rotating disk. Because a slider typically flies higher as the velocity of the disk recording medium increases, there is a tendency for the slider's outer rail to fly higher than the inner rail. Therefore, the flying slider has a structure that ensures that a roll angle can be generated in an attempt to counteract the tendency of the outer rail to fly higher than the inner rail. The roll angle is defined as the tilt angle between the principal plane of the slider in the radial direction of the disk and the principal plane of the disk surface.
The ability to control or generate changes in the roll angle are important to counteract other forces generated during disk drive manufacture or operations. Some of these forces or factors that must be compensated for include: manufacturing errors in the gimbals which attach the slider to the suspension arm; dynamic forces applied to the air bearing slider by the track accessing arm during tracking accessing; and varying skew angles tangential to the disk rotation as measured from the slider center line.
For example, regardless of the particular skew angle with respect to the direction of air flow, unequal pressure distribution develops between the outer and inner side rails. This causes the slider to fly with the inner rail much closer to the disk surface than the outer rail. As a result, the probability of physical contact with the disk surface at this slider's minimum flying height increases. Therefore, there is a continuing effort to develop air bearing sliders that carry a transducer as close to the disk surface as possible with a constant flying height and roll angle regardless of the varying flying conditions such as disk velocity and skew angle variation.
Air bearing sliders used in disk drives also typically have a leading edge (a front portion) and a trailing edge (a rear portion). Generally, the sliders have tapered or shallowly-etched portions at the leading edge to lift up slider by squeezing incoming air, and longitudinal air bearing rails that extend from the leading edge all or part way to the trailing edge. Airflow is developed in the direction on the disk surface and applied to cause the flying head slider to float off the rotating disk surface against the resiliency of the suspensions. Pitch angle is introduced through the fact that the flying height of the leading edge is generally different from that of the trailing edge. The pitch angle is defined as the tilt angle between the principal plane of the slider body in the tangential direction of the rotating disk and the principal plane of the disk surface.
The pitch angle is positive in the normal case in which the flying height of the trailing edge of the slider is lower than that of the leading edge of the slider. This is the preferred state for stable head flying. When the leading edge flying height is lower than the trailing edge flying height, however, the slider has a negative pitch angle, which can cause unstable head flying. In particular, with such a negative pitch angle, the possibility exists that there could be sudden physical contact between flying head and rotating medium.
Furthermore, if the designed positive pitch angle is too small, the possibility exists that the slider will dip down or inadvertently transition to a negative pitch angle orientation, caused by internal or external interference, for example, and the leading edge of the slider may hit the rotating disk. On the other hand, if the designed pitch angle is too large, the air stiffness needed for stable flying can
Cho Keung Youn
Park Ki-Ook
Letscher George J.
Samsung Electronics Co,. Ltd.
Volentine & Francos, PLLC
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