Dynamic magnetic information storage or retrieval – Head mounting – For adjusting head position
Reexamination Certificate
2001-08-01
2004-03-16
Heinz, A. J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head mounting
For adjusting head position
Reexamination Certificate
active
06707646
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention generally relates to rigid or hard disk drives or tape recording devices which store information or data on rotating or moving storage media. More specifically, the invention relates to a method and apparatus for dynamically controlling the flying behavior of a read/write magnetic head as a rotating magnetic disk spins under the head or as a moving magnetic tape moves under the head.
2. Description of the Related Art
Magnetic disk storage devices known in the prior art comprise an air-bearing slider. The slider itself is mounted on a so-called suspension arm which essentially functions as a load beam and which comprises a rigid portion and an elastic portion, wherein the elastic portion generates a load for urging the slider towards or away of the recording medium, so that the slider on which an electromagnetic transducer is mounted is pushed to the recording medium or pulled away from the recording medium with a certain necessary load.
For example, when a recording medium such as a magnetic recording disk is rotating, the load exerted on the slider is balanced by the airflow of an air cushion force exerted on the air bearing surface of the slider. As a result, the slider flies above the recording medium with a very fine gap, the so-called “flying height.”
The flying height of a slider carrying a magnetic read/write head above a rotating magnetic hard disk lies currently in the range of 20 nanometers and will likely decrease in the future. In currently known hard disk devices the flying height is substantially determined by the particular design of an air bearing surface of the slider and a head gimbal assembly. But thereupon variations of the flying height within a few nanometers may exist for non-identical devices of the same type owing to fabrication tolerances. These tolerances considerably influence the writing and reading characteristics to and from the hard disk.
Two different groups of types of prior art magnetic head suspension mechanisms are known. In a first group, a thin film formed on the elastic portion of the suspension arm which is expandable or shrinkable due to an internal stress of the film itself causes the elastic portion and thereby the arm to bend thus varying the flying height of the read/write head above the disk surface. However, the bending of the suspension arm towards the disk surface increases the spring force pushing against the aerodynamic lift of the slider.
Transducers for bending the suspension arm, piezoelectric films, or bi-metallic strips have been proposed in the art. Approaches belonging to the first mentioned group are disclosed for instance in U.S. Pat. No. 5,825,590, “Magnetic Head Suspension Mechanism with a Thin Film Thereon For Creating a Bent Portion of a Vibration Absorbing Portion,” assigned to Fujitsu Ltd., Japan and in U.S. Pat. No. 5,377,058, “Fly Height Servo Control of Read/Write Head Suspension” assigned to IBM Corporation, New York.
Another group of prior art approaches provides for a one-time and static adjustment of the spring pressure and/or the shape of the bending of the suspension arm. In Japanese Abstract JP 5189906 A, during production of floating type magnetic heads, it is therein proposed to set the floating amount of a slider at a small and exact amount by transferring heat energy to the spring part of the suspension arm and adjusting the spring pressure. Applying the heat is particularly accomplished by irradiating the spring with a laser beam and setting the bending amount in the rolling direction of the spring part by a discrete spring pressure regulation. After having set the bending amount the slider is mounted on the suspension arm.
According to another static approach disclosed in Japanese Abstract JP 63281283 A, the spring part is made of a superelastic material such as a shape-memory alloy which allows that the initial form of the spring part is rather a bent shape. The initial form is deformed until it is approximately parallel to the disk surface. Since only the spring part is made of the super elastic material, an in-plane rigidity is ensured and in addition the spring constant is minimized.
The above approaches using a transducer element have the drawback that such an element requires larger areas on the suspension what, for instance, complicates further miniaturization of the suspension arm.
SUMMARY OF THE INVENTION
The concept underlying the present invention is to influence or to vary the spring constant of a suspension and therefore to influence the equilibrium state of the prementioned two opposite forces, one resulting from the aircushion underneath the air-bearing surface of the slider thus causing a lift or sink force and the other force provided by the spring force of the suspension itself. By disturbing this equilibrium state of forces, the flying height of the read/write head can be changed in a controlled manner. By a controlled variation of the spring constant, the flying height therefore can be adjusted very precisely.
In contrast to the prior art approaches described above, the present invention provides for a passive as well as a active mechanism where actuation of the read-/write head is accomplished only by varying the spring constant k, and not by active deflection DX as in the prior art approaches, F=k−DX. In contrast to the prior art approaches, where the suspension is deflected actively by providing a bending force or bending momentum, according to the present invention the suspension, moreover, is being bent merely as a consequence of the new equilibrium of the mechanical forces acting upon the slider. In addition or alternative to the bending, the suspension can also be bent locally or even buckled by locally varying the spring constant give by the elastic modulus of the suspension material, respectively.
This invention therefore enables adjusting of an incorrect gramload or varying gramload only by (actively) adapting the spring constant appropriately. This can be accomplished already during the manufacturing process for the disk storage device after the suspension together with the read/write head have been assembled to the storage device or it can be accomplished during HDD operation as an active adjustment tool.
In addition, the proposed actuation scheme can also be implemented in a very small area on the suspension thus, for instance, enabling further miniaturization of the suspension arm.
For measuring the flying height of the head, there exist a number of methods and systems e.g. a thermal proximity sensing technique used in scanning probe microscopy sensors and exemplarily disclosed in U.S. Pat. No. 5,527,110 (Abraham et al.) entitled, “Method and Apparatus for Detecting Asperities on Magnetic Disks using Thermal Proximity Imaging”. As the spinning velocity of the hard disk is nearly constant during operation of the disk storage device, the lift or sink forces are nearly constant too for a given design of the slider, in particular its shape of the air-bearing surface, thus allowing a one-time adjustment of an incorrect gramload. In addition, a particular flying height can be set during the manufacturing process.
Besides a static adjustment of the spring force by way of varying the spring constant, also an active or dynamic flying height adjustment can be accomplished to guarantee a good read and write characteristic and particularly the operation characteristic of the underlying spinning storage system.
Thereupon, through the high-speed spinning of the disk, the entire disk storage device will normally change its temperature during operation. This does also raise the temperature of the suspension arm and the air temperature inside a disk storage housing. Different temperatures of the suspension arm particularly cause changes of the spring force and thus corresponding changes of the flying height of the head. Variations of the air pressure or contamination of the air bearing surface have an impact on the air streaming underneath the slider and thus influence the lift force actuating on the sli
Berger Ruediger Friedrich
Dietzel Andreas
Fleischmann Friedrich
Bracewell & Patterson L.L.P.
Heinz A. J.
Hitachi Global Storage Technologies - Netherlands B.V.
Martin Robert B.
LandOfFree
Method and apparatus for dynamically controlling the flying... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for dynamically controlling the flying..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for dynamically controlling the flying... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3259393