Ramp design for dynamic load

Details Ramp design for dynamic load Ramp design for dynamic load

2000-04-20

2004-04-13

Heinz, A. J. (Department: 2653)

Dynamic magnetic information storage or retrieval

Head mounting

For moving head into/out of transducing position

Reexamination Certificate

active

06721134

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of mass storage devices. More particularly, this invention relates to a disc drive which includes a ramp for loading and unloading read/write heads from the surface of a disc in the disc drive.
BACKGROUND OF THE INVENTION
One of the key components of any computer system is a place to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are a disc that is rotated, an actuator that moves a transducer to various locations over the disc from track to track, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disc.
The transducer is typically housed within a small ceramic block. The small ceramic block is passed over the disc so that it can read information representing data from the disc or write information representing data to the disc. When the disc is operating, the disc is usually spinning at relatively high revolutions per minute (“RPM”). These days common rotational speeds are 7200 RPM. Rotational speeds in high performance disc drives are as high as 10,000 RPM. Higher rotational speeds are contemplated for the future. These high rotational speeds place the small ceramic block in high air speeds.
The small ceramic block, also referred to as a slider, is usually aerodynamically designed so that it flies over the disc. The bottom side of the slider, the area that is facing the disc surface, is aerodynamically designed so that the distance variation (fly height variation) of the head to the disc is minimal. Fly height variations occur, because of different shew angles between the air flow and the slider leading edge and different air speeds, while the slider is positioned on different tracks on the disc. The slider has an air bearing surface (“ABS”) which includes rails and a cavity between the rails. The air bearing surface is that portion of the slider that is nearest the disc as the disc drive is operating. When the disc rotates, an air bearing is formed between the disc and head. This air bearing lifts the head off of the disc and reduces friction forces. Some head designs have a depression in the air bearing surface that produces a negative pressure area at the depression. The negative pressure or suction counteracts the pressure produced at the rails to provide more uniform fly heights from disc inner diameter (ID) to outer diameter (OD). The fly height is the thickness of the air lubrication film or the distance between the disc surface and the head. This film eliminates mechanical friction and resulting wear that would occur if the slider and disc were in mechanical contact during disc rotation.
The best performance of the disc drive results when the head is flown as closely to the surface of the disc as possible without contact between the disc and the slider. Today's slider is designed to fly on a very thin layer of gas or air. In operation, the distance between the head and the disc is very small. Currently “fly” heights are about 1-2 microinches. It is contemplated that in future disc drives, the slider will not fly on a cushion of air but rather will pass through a layer of lubricant on the disc. A flexure or gimbal is attached to the load spring or load beam and to the slider. The flexure allows the slider to pitch and roll so that the slider can remain in close proximity to the disc.
Information representative of data is stored on the surface of the memory disc. Disc drive systems read and write information stored on tracks on memory discs. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the memory disc, read and write information on the memory discs when the transducers are accurately positioned over one of the designated tracks on the surface of the memory disc. The transducer is also said to be moved to a target track. As the memory disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the memory disc. Similarly, reading data on a memory disc is accomplished by positioning the read/write head above a target track and reading the stored material on the memory disc. To write on or read from different tracks, the read/write head is moved in a substantially radial direction across the tracks to a selected target track. To be totally accurate, the slider passes in a circular motion as it pivots about the axis of the actuator assembly. The data is divided or grouped together on the tracks. In most disc drives, the tracks are a multiplicity of concentric circular tracks. Servo feedback information is used to accurately locate the transducer.
One of the most critical times during the operation of a disc drive occurs just before the disc drive shuts down or during the initial moment when the disc drive starts. When shutdown occurs, the slider fly height decreases until the slider contacts the disc. The small block or slider is moved to a non-data area of the disc where it literally landed and skidded to a stop. To improve magnetic performance, discs now are formed with a smooth surface. The smooth surface allows lower flying heights. Stiction, which is static friction, occurs between the air bearing surface of the slider and the smooth disc surface. Forces from stiction, in some instances, can be high enough to separate the slider from the suspension or prevent the disc from spinning.
To overcome the stiction problem and to provide for a much more rugged design for disc drives used in mobile computers, such as portable computers and notebook computers, disc drive designers began unloading the sliders onto a ramp positioned on the edge of the disc. Disc drives with ramps are well known in the art. U.S. Pat. No. 4,933,785 issued to Morehouse et al. is one such design. Other disc drive designs having ramps therein are shown in U.S. Pat. Nos. 5,455,723, 5,235,482 and 5,034,837. Before power is actually shut off, the actuator assembly moves the suspension, slider and transducer to a park position on the ramp. Commonly, this procedure is referred to as unloading the heads. The disc drive must also be able to unload the heads if a so-called hot unplug occurs, where the slider is moving at full speed towards inner diameter (“ID”) and has almost reached the ID. The rotary inertia of the disc stack is now used to spin the motor, which is used as a generator to move the head stack from the ID to the outer diameter (“OD”) and up the ramp. Unloading the heads helps to insure that data on the disc is preserved since, it prevents shock inputs from causing heads to lift off of the disc and slap back down onto the disc. Unloading the heads can also prevent disc-to-arm contact that can cause disc damage. When starting up the disc drive, the process is reversed. In other words, the suspension and slider are moved from the ramp onto the surface of the disc which is already spinning at a constant speed. This is referred to as loading the heads or sliders onto the disc.
Use of a ramp to load and unload the disc overcomes many aspects of the stiction problem. However, during the loading process and the unloading process, the slider can contact the disc and result in head or disc damage. The danger of contact between the slider and discs is fairly high.
Dynamic load/unload of the slider to and from the disc is a very critical process, because of the potential danger of contact between the disc and the slider air-bearing surface. Since the air-bearing suction exerts a force that will hold the slider on the disc during the unloading process, deformati

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