Patent Application
20060146443
The invention relates to noise dampening structures in a hard disk drive. More particularly, the invention relates to a disk damper configured to reduce air turbulence, which otherwise causes vibrations causing the read-write head to experience noise when accessing the rotating disk surface.
Disk dampers suppress system noise caused by the vibration of the rotating disk or disks. The gaseous media (often air) surrounding the rotating disks is moved by the rotating disk surfaces. The airflow circulating between the disks and disk damper forms a flat, thin donut-shaped channel. This channel often has a rectangular cross section that extends from the outside diameter to the inside diameter of the rotating disk surfaces. If the spacing between the disk and the disk damper is small enough, and the overlap between them is large enough, the thin air film in the channel has the desired damping effect.
While the prior art disk dampers reduce noise from the vibration of the disk(s), there remain problems. For example, some prior art disk dampers while reducing disk vibrations, add a different type of noise. The air stream, after leaving the channel, creates turbulence, which interacts with the actuator assembly. This interaction increases the noise experienced by the read-write head in the actuator assembly as it accesses the rotating disk surface. The turbulence is caused by the physical configuration of the disk damper. Specifically, the typical prior art disk damper has blunt edges. As the airflow leaves the channel, the blunt edges create rapid air expansion and pressure changes, which lead to turbulence. What is needed is a disk damper reducing the air turbulence, which vibrates the actuator assembly, causing the read-write head to experience noise when accessing the rotating disk surface.
The present invention includes apparatus and methods for disk dampers configured to reduce air turbulence. Disk dampers fabricated in accord with the invention include an inlet edge and/or an outlet edge, oriented and shaped to control airflow within the hard disk drive to minimize the airflow turbulence experienced by the actuator assembly. Reducing the turbulence experienced by the actuator assembly improves the Position Error Signal (PES), as the read-write head accesses a rotating disk surface. As used herein, the inlet edge refers to the leading edge as the airflow enters the channel. The outlet edge refers to the trailing edge as the airflow leaves the channel. The invention applies to hard disk drives including air or other gasses within their enclosure.
The outlet edge is preferably be curved and oriented at an oblique angle with respect to the angular rotation of the disk(s) in the hard disk drive. The outlet edge preferably extends over a section of a sector angle. The distributed airflow along the outlet edge permits the overall flow velocity to slow gradually, which creates less turbulence near the actuator assembly and consequently less system noise. As used herein, an oblique angle is not a blunt angle, which approaches being a right angle.
The inlet edge is preferably oblique, which helps to slow the overall velocity of the airflow into the disk damper. This also allows the tip of the inlet edge to be positioned closer to the actuator assembly than previously possible, which reduces air velocity at the actuator assembly, additionally minimizing the noise caused by air turbulence.
Embodiments of the invention including both oblique outlet edges and oblique inlet edges have been experimentally shown to improve the PES for the rotating disk surfaces.
The present invention includes apparatus and methods for disk dampers with an inlet edge and/or an outlet edge, oriented and shaped to control airflow within the hard disk drive to minimize the airflow turbulence experienced by actuator assembly. The invention improves the Position Error Signal (PES), as the read-write head accesses a rotating disk surface. As used herein, the inlet edge refers to the leading edge as the airflow enters the channel. The outlet edge refers to the trailing edge as the airflow leaves the channel. The invention is particularly suited for use in hard disk drives including air or other gasses within the disk drive enclosure.
Currently, the gap between a disk surface and the facing, prior art, disk damper surface is about 0.5 millimeter (mm). This gap generates a thin pressurized air film, used to suppress disk vibrations. In typical current disk drives there is a blunt angular transition of the airflow cross section at the outlet edge. This blunt angular transition causes the sudden release, expansion and depressurizing of the air film as it leaves the channel, which can create excessive air turbulence as it moves away from such outlet transitions.
The disk damper preferably includes three contiguous, coplanar sections, an inlet transition section 190, and an intermediate section 192, and an outlet transition section 194. The intermediate section 192 preferably has an essentially constant radial width (the radial line originates from the spindle Z-axis 132), and has a length extending between φ1 and φ2. Both the inlet transition section 190 and the outlet transition section 194 have varying radial widths. The radial width of inlet transition section 190 increases through the length of φ1 from zero to the radial width of the intermediate section, and the radial width of the outlet transition section 194 increases through the length of φ2 from zero to the radial width of the intermediate section.
The disk damper 102 is spaced apart form the disk surface 109 to form a gap or channel between them. The channel is best seen in
In the embodiment shown in
The outlet edge 126 is preferably curved and oriented at an oblique angle to the angular rotation of at least disk 101, with the curve extending over an arc of a φ2 angle. The distributed airflow along the oblique outlet edge 126 permits the overall flow velocity to slow gradually, which creates less turbulence near the actuator assembly 144 and consequently less system noise. Outlet end 121 and the outlet edge 126 are joined smoothly.
An alternate embodiment is seen in
The φ2 angle is preferably between twenty degrees and eighty degrees, but more preferrably between twenty five degrees and seventy degrees, and still more preferrably between thirty degrees and sixty degrees.
The inlet edge 124 is preferably curved and oriented at an oblique angle to the angular rotation of the disk 101, with the curve extending over an arc of a φ1 angle. This configuration has been found to slow the velocity of the gaseous media in the channel 133 and reduce turbulence created at the inlet edge. Consequently, the tip 123 of the inlet edge 124 may be closer to the actuator assembly 144 than is possible in prior art designs.
The inlet edge 124 receives a circulating airflow 111 from the direction of the actuator assembly 144. Referring to
The φ1 angle is preferably between twenty degrees and sixty degrees, but more preferrably between twenty five degrees and fifty degrees, and still more preferrably between thirty degrees and forty five degrees.
This invention is particularly suited for use in a hard disk including more than one disk.
Tables 1, 2 and 3 show comparisons of three PES measurements taken at three different radial locations on hard disk drives assembled with two different disk damper assemblies: (1) A disk damper constructed in accord with the invention, and (2) a prior art disk damper. The Tables show noticeable improvement by lowering the noise spectrum for the hard disk drive with the disk damper invention. The Middle Diameter refers to measurements performed midway between the Inside Diameter 150 and the Outside Diameter 108 on the rotating disk surface 109 of the Figures.
Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiments can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.
