Pitch and roll attitude control for sliders in a disk drive

Details Pitch and roll attitude control for sliders in a disk drive Pitch and roll attitude control for sliders in a disk drive

1998-12-08

2003-03-18

Miller, Brian E. (Department: 2652)

Dynamic magnetic information storage or retrieval

Head mounting

Disk record

Reexamination Certificate

active

06535355

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of mass storage devices. More particularly, this invention relates to a disk drive which includes a device for controlling the pitch and roll attitudes of the sliders as they are loaded and unloaded from the surface of the disk in the disk 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 disk drive. The most basic parts of a disk drive are a disk that is rotated, an actuator that moves a transducer to various locations over the disk, and electrical circuitry that is used to write and read data to and from the disk. The disk drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disk surface. A microprocessor controls most of the operations of the disk drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disk.
The transducer is typically housed within a small ceramic block. The small ceramic block is passed over the disk in a transducing relationship with the disk. The transducer can be used to read information representing data from the disk or write information representing data to the disk. When the disk is operating, the disk is usually spinning at relatively high revolutions per minute (“RPM”). These days common rotational speeds are 7200 RPM. Rotational speeds in high performance disk 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 disk. 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 disk as the disk drive is operating. When the disk rotates, air is dragged between the rails and the disk surface causing pressure, which forces the head away from the disk. At the same time, the air rushing past the depression in the air bearing surface produces a negative pressure area at the depression. The negative pressure or suction counteracts the pressure produced at the rails. The different forces produced counteract and ultimately fly over the surface of the disk at a particular fly height. The fly height is the thickness of the air lubrication film or the distance between the disk surface and the head. This film eliminates the friction and resulting wear that would occur if the transducing head and disk were in mechanical contact during disk rotation.
The best performance of the disk drive results when the ceramic block is flown as closely to the surface of the disk as possible. Today's small ceramic block or slider is designed to fly on a very thin layer of gas or air. In operation, the distance between the small ceramic block and the disk is very small. Currently “fly” heights are about 1-2 micro inches. In some disk drives, the ceramic block does not fly on a cushion of air but rather passes through a layer of lubricant on the disk. A flexure is attached to the load spring and to the slider. The flexure allows the slider to pitch and roll so that the slider can accommodate various differences in tolerance and remain in close proximity to the disk.
Information representative of data is stored on the surface of the memory disk. Disk drive systems read and write information stored on tracks on memory disks. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the memory disk, read and write information on the memory disks when the transducers are accurately positioned over one of the designated tracks on the surface of the memory disk. The transducer is also said to be moved to a target track. As the memory disk 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 disk. Similarly, reading data on a memory disk is accomplished by positioning the read/write head above a target track and reading the stored material on the memory disk. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disk drives, the tracks are a multiplicity of concentric circular tracks. In other disk drives, a continuous spiral is one track on one side of a disk drive. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held very accurately during a read or write operation using the servo information.
One of the most critical times during the operation of a disk drive occurs just before the disk drive shuts down or during the initial moment when the disk drive starts. When shutdown occurs, the small ceramic block or slider is typically flying over the disk at a very low height. In the past, the small block or slider was moved to a non-data area of the disk where it literally landed and skidded to a stop. Problems arise in such a system. When disks were formed with a smooth surface, stiction forces occur between the slider and the disk surface. In some instances, the forces due to separate the slider from the suspension. Another problem is that landing a slider on the disk may limit the life of the disk drive. Each time the drive is turned off another contact start stop cycle occurs. After many contact start stop cycles, the small ceramic block or slider may chip or produce particles. The particles could eventually cause the disk drive to fail. When shutting down a disk drive, several steps are taken to help insure that the data on the disk is preserved. In general, the actuator assembly is moved so that the transducers do not land on the portion of the disk containing data. There are many ways to accomplish this. A ramp on the edge of the disk is one design method that has gained industry favor more recently. Disk 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 disk drive designs having ramps therein are shown in U.S. Pat. Nos. 5,455,723, 5,235,482 and 5,034,837.
Typically, the ramp is positioned to the side of the disk. A portion of the ramp is positioned over the disk itself. In operation, before power is actually shut off, the actuator assembly moves the suspension, slider and transducer to a park position on the ramp. When the actuator assembly is moved to a position where parts of the suspension are positioned on the top of the ramp, the sliders or ceramic blocks do not contact the disk. Commonly, this procedure is referred to as unloading the heads. Unloading the heads helps to insure that data on the disk is preserved since, at times, unwanted contact between the slider and the disk results in data loss on the disk. The actuator assembly may be provided with a separate tang associated with each head suspension. The tang may ride up and down the ramp surface. In other drives, the ramp may be positioned such that the suspension rides up and down the ramp to unload and load the disk or disks of the disk drive. When starting up the disk drive, the process is reversed. That is to say that the suspension and slider are moved from the ramp onto the surface of the disk. This is referred to as loading the heads onto the disk.
During load and unload of the slider onto the disk, the slider typically rolls and pitches. Sometimes the slider pitches or rolls too much. The result is that the slider may then contact the disk. In other words, if the slider rolls too much when it is loaded or unloaded, the edge of the slider may contact the disk. If the slider pitches too much when the is loaded or un

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