U.S. patent application number 11/832332 was filed with the patent office on 2009-02-05 for wear reduction in fdb by enhancing lubricants with nanoparticles.
This patent application is currently assigned to SEAGATE TECHNOLOGY LLC. Invention is credited to Raquib Uddin Khan.
Application Number | 20090033164 11/832332 |
Document ID | / |
Family ID | 40337429 |
Filed Date | 2009-02-05 |
United States Patent
Application |
20090033164 |
Kind Code |
A1 |
Khan; Raquib Uddin |
February 5, 2009 |
WEAR REDUCTION IN FDB BY ENHANCING LUBRICANTS WITH
NANOPARTICLES
Abstract
An embodiment of the invention relates to a spindle motor of a
magnetic recording storage device, the spindle motor comprising a
fluid dynamic bearing comprising a lubricant comprising at least
one of an organic and inorganic nanomaterial.
Inventors: |
Khan; Raquib Uddin;
(Pleasanton, CA) |
Correspondence
Address: |
Seagate Technology;c/o DARBY & DARBY P.C.
P.O. Box 770, Church Street Station
New York
NY
10008-0770
US
|
Assignee: |
SEAGATE TECHNOLOGY LLC
Scotts Valley
CA
|
Family ID: |
40337429 |
Appl. No.: |
11/832332 |
Filed: |
August 1, 2007 |
Current U.S.
Class: |
310/90 ; 508/110;
508/154; 508/165; 508/171; 977/742 |
Current CPC
Class: |
C10N 2010/14 20130101;
C10N 2030/02 20130101; C10M 169/04 20130101; C10N 2040/18 20130101;
C10M 2201/041 20130101; C10M 2207/2855 20130101; C10M 2207/2815
20130101; C10N 2020/06 20130101; C10M 2207/2825 20130101; C10M
2201/065 20130101; C10M 2201/066 20130101 |
Class at
Publication: |
310/90 ; 508/110;
508/154; 508/165; 508/171; 977/742 |
International
Class: |
C10M 125/02 20060101
C10M125/02; C10M 163/00 20060101 C10M163/00 |
Claims
1. A spindle motor of a magnetic recording storage device, the
spindle motor comprising a fluid dynamic bearing comprising a
lubricant comprising at least one of an organic and inorganic
nanomaterial.
2. The spindle motor of magnetic recording storage device of claim
1, wherein the lubricant has a single phase composition.
3. The spindle motor of magnetic recording storage device of claim
1, wherein the lubricant comprises a mineral base hydro carbon,
synthetic hydrocarbon containing compound, or combinations
thereof.
4. The spindle motor of magnetic storage device of claim 1, wherein
the lubricant comprises about 0.01 to about 5.0 percent by weight
of the organic or inorganic nanomaterial.
5. The spindle motor of magnetic storage device of claim 1, wherein
the lubricant comprises about 0.02 to about 2.0 percent by weight
of the organic or inorganic nanomaterial.
6. The spindle motor of magnetic storage device of claim 1, wherein
the lubricant comprises about 0.05 to about 1.0 percent by weight
of the organic or inorganic nanomaterial.
7. A spindle motor of a magnetic recording storage device of claim
1, wherein the lubricant comprises di-2-ethyl hexyl suberate.
8. The spindle motor of magnetic recording storage device of claim
1, wherein the lubricant comprises an ester selected from the group
consisting of diester, monoester, simple ester, compound ester and
combinations thereof.
9. The spindle motor of magnetic recording storage device of claim
8, wherein the lubricant comprises an additive.
10. The spindle motor of magnetic recording storage device of claim
1, wherein the lubricant comprises di-2-ethyl hexyl pimelate.
11. The spindle motor of magnetic recording storage device of claim
1, wherein the organic nanomaterial comprises carbon nano tubes,
onions, or combinations thereof.
12. The spindle motor of magnetic recording storage device of claim
11, wherein the onions are Ni/Y based single wall carbon nano
tubes, Fe-based multiwall carbon nano tubes, metal free multiwall
nano tubes, or combinations thereof.
13. The spindle motor of magnetic recording storage device of claim
1, wherein the inorganic nanomaterial comprises inorganic fullerene
(IF) comprising IF-MoS.sub.2, IF-WS.sub.2, IF-NbS.sub.2 or
combinations thereof.
14. A lubricant comprising (a) an organic or inorganic nanomaterial
and (b) a mineral base hydro carbon, synthetic hydrocarbon
containing compound, or combinations thereof.
15. The lubricant of claim 14, wherein the lubricant comprises 0.01
to 5.0 percent by weight of the organic or inorganic
nanomaterial.
16. The lubricant of claim 14, wherein the inorganic nanomaterial
comprises carbon nano tubes, onions, or combinations thereof.
17. The lubricant of claim 14, wherein the onions are Ni/Y based
single wall carbon nano tubes, Fe-based multiwall carbon nano
tubes, metal free multiwall nano tubes, or combinations
thereof.
18. The lubricant of claim 14, wherein the inorganic nanomaterial
comprises IF-MoS.sub.2, IF-WS.sub.2, IF-NbS.sub.2 or combinations
thereof.
19. A spindle motor of a magnetic recording storage device, the
spindle motor comprising a fluid dynamic bearing comprising a
lubricant comprising an organic liquid and an inorganic
nanomaterial, wherein the inorganic nanomaterial and the organic
liquid form a suspension such that the inorganic nanomaterial does
not settle out from the suspension.
20. The spindle motor of magnetic recording storage device of claim
19, wherein the inorganic nanomaterial comprises IF-MoS.sub.2,
IF-WS.sub.2, IF-NbS.sub.2 or combinations thereof.
Description
RELATED APPLICATION
[0001] None.
BACKGROUND
[0002] Magnetic discs with magnetizable media are used for data
storage in most all computer systems. Current magnetic hard disc
drives operate with the read-write heads only a few nanometers
above the disc surface and at rather high speeds, typically a few
meters per second. Because the read-write heads can contact the
disc surface during operation, a layer of lubricant is coated on
the disc surface to reduce wear and friction.
[0003] FIG. 1 shows a disk recording medium and a cross section of
a disc showing the difference between longitudinal and
perpendicular recording. Even though FIG. 1 shows one side of the
non-magnetic disk, magnetic recording layers are sputter deposited
on both sides of the non-magnetic aluminum substrate of FIG. 1.
Also, even though FIG. 1 shows an aluminum substrate, other
embodiments include a substrate made of glass, glass-ceramic,
NiP/aluminum, metal alloys, plastic/polymer material, ceramic,
glass-polymer, composite materials or other non-magnetic
materials.
[0004] Lubricants in a disc drive are applied on the spindle motor
as well as on the disc surface. A lubricant fluid such as oil is
typically filled in the bearing space which is created in the gap
between the bearing sleeve and the shaft bush of a fluid dynamic
bearing. On the other hand, a lubricant is applied to the disc
surface by dipping the disc in a bath containing the lubricant or
spraying the lubricant to the disc surface.
[0005] The lubricant film on the spindle motor or hard discs
provides protection to the underlying materials by preventing wear.
In addition, it provides protection against corrosion of the
underlying materials. Reliability of hard disk drive is depends on
the durability of the spindle motor and thin film media.
Lubrication plays unquestionably an important role.
[0006] There are many common kinds of lubricants presently used in
different kinds of fluid dynamic bearing but very few kinds are
appropriate for disk drive application. It has been found that disk
drive is very sensitive to the type and the amount of chemicals
used in different components it is made from. Thus, it is desirable
to develop a novel lubricant that would be appropriate for fluid
dynamic bearing of disk drive application such that the lubricant
exhibits compatibility with disk-head interface.
SUMMARY
[0007] An embodiment of the invention relates to a spindle motor of
a magnetic recording storage device, the spindle motor comprising a
fluid dynamic bearing comprising a lubricant comprising at least
one of an organic and inorganic nanomaterial.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present invention will be better understood by reference
to the Detailed Description of the Invention when taken together
with the attached drawings, wherein:
[0009] FIG. 1 shows a magnetic recording medium.
[0010] FIG. 2 shows a fluid dynamic bearing spindle motor.
DETAILED DESCRIPTION OF THE INVENTION
[0011] As used in the specification and claims, the singular forms
"a", "an" and "the" include plural references unless the context
clearly dictates otherwise.
[0012] The invention is directed to a lubricant for a disc and to a
spindle motor containing the lubricants of the embodiments of the
invention. Lubricants typically are liquid and contain molecular
weight components that range from several atomic mass unit (AMU) to
thousands of AMU including diesters, polyol esters, synthetic
hydrocarbon, perfluoropolyether (PFPE) etc.
[0013] A "nanomaterial" as used herein refers to a structure, a
device or a system having a dimension at the atomic, molecular or
macromolecular levels, in the length scale of approximately about 1
to about 500 nanometer range. Preferably, a nanomaterial has
properties and functions because of the size and can be manipulated
and controlled on the atomic level. Nanoparticles are of great
scientific interest as they are effectively a bridge between bulk
materials and atomic or molecular structures. A bulk material
should have constant physical properties regardless of its size,
but at the nano-scale this is often not the case. Size-dependent
properties are observed such that the properties of materials could
change as their size approaches the nanoscale. For example, the
bending of bulk copper (wire, ribbon, etc.) occurs with movement of
copper atoms/clusters at about the 50 nm scale. Copper
nanoparticles smaller than 50 nm are considered super hard
materials that do not exhibit the same malleability and ductility
as bulk copper. The interesting and sometimes unexpected properties
of nanoparticles are partly due to the aspects of the surface of
the material dominating the properties in lieu of the bulk
properties. The percentage of atoms at the surface of a material
becomes significant as the size of that material approaches the
nanoscale. For bulk materials larger than one micrometre the
percentage of atoms at the surface is minuscule relative to the
total number of atoms of the material. Suspensions of nanoparticles
in liquid such as lubrication oil are possible because the
interaction of the particle surface with the solvent is strong
enough to overcome differences in density, which usually result in
a material either sinking or floating in a liquid. Nanoparticles
often have unexpected visible properties because they are small
enough to scatter visible light rather than absorb it. For example
gold nanoparticles appear deep red to black in solution. At the
small end of the size range, nanoparticles are often referred to as
clusters. Metal, dielectric, and semiconductor nanoparticles have
been formed, as well as hybrid structures (e.g., core-shell
nanoparticles). Nanospheres, nanorods, and nanocups are just a few
of the shapes that within the embodiments of the invention.
[0014] FIG. 2 shows a fluid dynamic bearing spindle motor. FIG. 2
is a vertical sectional view of a single thrust plate hydrodynamic
bearing motor design of a type which is already established in this
technology. The basic structure of the motor shown in this figure
includes a stationary shaft 10 and a hub 12 supported from a sleeve
13 for rotation around the shaft. The shaft 10 includes a thrust
plate 14 at one end, and terminates in a shoulder 16 at the
opposite end. The sleeve 13 supports a counterplate 19 at one end,
for rotation over the thrust plate 14. The counterplate 19 and
thrust plate 14 are separated by a sufficient gap 22 to allow
movement of lubricating fluid to lubricate the hydrodynamic bearing
through the central hole or reservoir 20, through the gap 22,
through the reservoir 26 defined between the end of the thrust
plate 14 and an interior surface 27 of the sleeve 13, and between
the lower surface 24 of the thrust plate 14 and an upper surface 25
of the sleeve 13, and between an inner surface 28 of the sleeve and
the exterior surface 29 of the fixed shaft. The fluid path is
completed to reservoir 20 primarily through a central bore 21. In
order to promote the flow of fluid over the bearing surfaces which
are defined between the thrust plate 14 and the counterplate 19;
between the thrust plate 14 and the sleeve 13, and between the
shaft 10 and the sleeve 13, typically one of the two opposing
surfaces of each such assembly carries sections of grooves as is
well known in this technology.
[0015] The fluid flow between the bearing surfaces creates
hydrodynamic pressure, resulting in stiffness. Circulation of fluid
is maintained through central hole 20 of the shaft to the other
bearing surfaces by the appropriate designing of geometry and
grooving patterns of the baring surfaces. The remainder of the
structure of significance which is used to complete the motor
design include shaft extension 30 which ends in threaded region 31
which is threaded into a portion of the base 44. A stator 42
cooperates with magnets 40 which are supported from the sleeve 13,
with energization of the stator windings 42 causing rotation of the
sleeve 18 and the hub 12 about the stationary shaft.
[0016] As used in a disc drive motor, this system supports one or
more discs 44 for rotation. Because the transducers and disc drives
fly at extremely low heights over the surface of the disc, it is
essential that there not be wobble or vibration of the hub and disc
as it rotates. Moreover, it is also important that should such
wobble occur, that there is no touch down between the surfaces of
the thrust plate 14 and the opposing surface of the counterplate 19
and sleeve 13. However, as explained above, in a cantilever type
bearing such as shown in FIG. 2, where the load carrying surface
which is thrust plate 14 is located far from the center point about
which any pivoting would occur in the event of vibration or wobble,
there is a much greater chance of a touch down or contact between
the facing surfaces, which would result in both wear of the
surfaces over the long term, and a slow down of the rotational
speed of the disc in the short term.
[0017] Lubricants in a disc drive are applied on the spindle motor
as well as on the disc surface. A lubricant fluid such as oil is
typically filled in the bearing space which is created in the gap
between the bearing sleeve and the shaft bush of a fluid dynamic
bearing. On the other hand, a lubricant is applied to the disc
surface by dipping the disc in a bath containing the lubricant or
spraying the lubricant to the disc surface.
[0018] The lubricant film on the spindle motor or hard discs
provides protection to the underlying materials by preventing wear.
In addition, it provides protection against corrosion of the
underlying materials. Reliability of hard disk drive is depends on
the durability of the spindle motor and thin film media.
Lubrication plays unquestionably an important role.
[0019] Conventional lubricant additives that reduce the friction
and wear are organic compounds and their effectiveness is dependent
on a tribo-chemical reaction leading to a tribological film
formation having some harmful byproducts. The embodiments of the
present invention relate to lubricant containing nanomaterials such
as carbon nanotubes, onions and/or inorganic fullerene (IF) in
which no chemical reaction is generally required to achieve low
friction in lubricant. According to the embodiments of the
invention, the nanomaterials are active as friction and wear
reducers of the lubricant even at ambient and low temperatures.
[0020] Lubricants can include Di-Octyl Sebacate, Di octyl Azelate,
Di octyl suberate, Dioctyl Pimelate, Di-octyl adipate, which are
the reaction products of 2-Ethyl-I-hexanol (Isooctyl alcohol) and
the dibasic acids of C10 (10 carbon), C9, C8, C7 and C6
respectively (named--sebacic acid, azelaic acid, Suberic acid,
Pimelic acid and adipic acid). The lubricants may also include the
polyol ester, synthetic hydrocarbon, PFPE etc. The lubricants of
the embodiments may also contain other additives like anti-oxidant,
corrosion inhibitors etc. to enhance the overall lubricant life.
The lubricants of the embodiments of the invention further comprise
organic and/or inorganic nanomaterials.
[0021] The nanoparticles of the embodiments of the invention can be
nanotubes, fullerenes, onions, etc. A "nanotube" refers either a
carbon nanotube or an inorganic nanotube. The carbon nanotube
refers to a fullerene molecule having a cylindrical or toroidal
shape. A "fullerene" refers to a form of carbon having a large
molecule consisting of an empty cage of sixty or more carbon atoms.
Carbon nanotubes are allotropes of carbon. A single wall carbon
nanotube is a one-atom thick graphene sheet of graphite (called
graphene) rolled up into a seamless cylinder with diameter of the
order of a nanometer. This results in a nanostructure where the
length-to-diameter ratio exceeds 10,000. Such cylindrical carbon
molecules have novel properties that make them potentially useful
in many applications in nanotechnology, electronics, optics and
other fields of materials science. They exhibit extraordinary
strength and unique electrical properties, and are efficient
conductors of heat. Carbon nanotubes are members of the fullerene
structural family, which also includes buckyballs. Whereas
buckyballs are spherical in shape, a nanotube is cylindrical, with
at least one end typically capped with a hemisphere of the
buckyball structure. Their name is derived from their size, since
the diameter of a nanotube is in the order of a few nanometers
(approximately 50,000 times smaller than the width of a human
hair), while they can be up to several millimeters in length. There
are two main types of nanotubes: single-walled nanotubes and
multi-walled nanotube.
[0022] An inorganic nanotube is a cylindrical molecule often
composed of metal oxides, and morphologically similar to a carbon
nanotube. Inorganic nanotubes have been observed to occur naturally
in some mineral deposits. Inorganic nanotubes can be synthesized of
inorganic materials, such as vanadium oxide and manganese oxide.
Inorganic nanotubes can also be constructed from main group
elements, boron nitride (borazine) being a prime contender. Being
as borazine is isoelectronic with benzene, the substance could
logically form sheets, fullerene analogs and nanotube analogs.
[0023] As the nanomaterials of the embodiments of the invention
have a very large surface to volume ratio, the friction value in
lubricated system of the embodiments of the invention can come down
significantly even with a small addition of the nanomaterials of
the invention. The amount of nanomaterials in the lubricant of the
embodiments of the invention can be in the range of about 0.01 to
about 5 percent by volume of the lubricating oil, more preferably
in the range of about 0.02 to about 1 percent by volume of the
lubricating oil, and most preferably in the range of about 0.05 to
about 0.5 percent by volume of the lubricating oil.
[0024] It is desirable that the lubricant has a relatively narrow
molecular weight distribution of molecular components. In practice,
the narrower the distribution the easier it will be to maintain a
steady-state concentration of one or more components in the vapor.
For example, if the highest and lowest molecular weight components
in the lubricant have very similar molecular weights, their vapor
pressures will also be very similar. The lubricant can also be the
mixture of two or more lubricants which will contain the nano
materials as additives.
[0025] The viscosity range of the lubricant can be 3 to 50 cst @
40.degree. C. and 1 to 10 cst @ 100.degree. C. and more preferably
5-15 cst @ 40.degree. C. and 2 to 8 cst @ 100.degree. C.
EXAMPLES
[0026] The following ester-containing lubricants were prepared by
the reaction of an acid a dioctyl alcohol:
TABLE-US-00001 Acid Dioctyl alcohol Ester Adipic acid (6 carbon)
2-ethyl hexyl alcohol (8 carbon) Di-2-ethyl hexyl adipate Pemelic
acid (7 carbon) 2-ethyl hexyl alcohol (8 carbon) Di-2-ethyl hexyl
pimelate Phthalic acid (8 carbon) 2-ethyl hexyl alcohol (8 carbon)
Di-octyl phthlate Suberic acid (8 carbon) 2-ethyl hexyl alcohol (8
carbon) Di-2-ethyl hexyl suberate Azelaic acid (9 carbon) 2-ethyl
hexyl alcohol (8 carbon) Di-octyl azelate Sebacic acid (10 carbon)
2-ethyl hexyl alcohol (8 carbon) Di-octyl sebacate
[0027] The lubricants embodiment of the invention can be prepared
by mixing these ester-containing lubricants with carbon nano tubes
and onions like Ni/Y based single wall carbon nano tubes, Fe-based
multiwall carbon nano tubes or metal free multiwall nano tubes and
inorganic nanoparticles such as inorganic fullerene (IF), e.g.,
IF-MoS.sub.2, IF-WS.sub.2, IF-NbS.sub.2 can be added in an amount
ranging from about 0.01 to about 5.0 weight percent to form the
lubricants of the embodiments of the invention.
[0028] In this application, the word "containing" means that a
material comprises the elements or compounds before the word
"containing" but the material could still include other elements
and compounds. This application discloses several numerical ranges
in the text and figures. The numerical ranges disclosed inherently
support any range or value within the disclosed numerical ranges
even though a precise range limitation is not stated verbatim in
the specification because this invention can be practiced
throughout the disclosed numerical ranges.
[0029] The above description is presented to enable a person
skilled in the art to make and use the invention, and is provided
in the context of a particular application and its requirements.
Various modifications to the preferred embodiments will be readily
apparent to those skilled in the art, and the generic principles
defined herein may be applied to other embodiments and applications
without departing from the spirit and scope of the invention. Thus,
this invention is not intended to be limited to the embodiments
shown, but is to be accorded the widest scope consistent with the
principles and features disclosed herein. The implementations
described above and other implementations are within the scope of
the following claims.
* * * * *