U.S. patent application number 11/200891 was filed with the patent office on 2006-03-16 for bearing having anodic nanoparticle lubricant.
This patent application is currently assigned to Emerson Power Transmission Manufacturing, L.P.. Invention is credited to Patrick Tibbits.
Application Number | 20060056752 11/200891 |
Document ID | / |
Family ID | 34312570 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060056752 |
Kind Code |
A1 |
Tibbits; Patrick |
March 16, 2006 |
Bearing having anodic nanoparticle lubricant
Abstract
A bearing with lubricant having metal or metal alloy
nanoparticles that are more anodic than the metal or metal alloy of
which the inner or outer raceways of the bearing are constructed;
and method for using the same.
Inventors: |
Tibbits; Patrick;
(Valparaiso, IN) |
Correspondence
Address: |
MCDONNELL BOEHNEN HULBERT & BERGHOFF LLP
300 S. WACKER DRIVE
32ND FLOOR
CHICAGO
IL
60606
US
|
Assignee: |
Emerson Power Transmission
Manufacturing, L.P.
|
Family ID: |
34312570 |
Appl. No.: |
11/200891 |
Filed: |
August 10, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10620985 |
Jul 16, 2003 |
6945699 |
|
|
11200891 |
Aug 10, 2005 |
|
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Current U.S.
Class: |
384/462 |
Current CPC
Class: |
F16C 2204/50 20130101;
C10N 2020/06 20130101; F16C 2240/48 20130101; C23C 24/00 20130101;
F16C 33/6688 20130101; F16C 33/585 20130101; C10N 2030/02 20130101;
F16C 19/06 20130101; C10N 2050/015 20200501; F16C 19/52 20130101;
C10M 125/04 20130101; C10N 2010/04 20130101; C10M 2201/05 20130101;
F16C 33/6633 20130101; C23C 30/00 20130101 |
Class at
Publication: |
384/462 |
International
Class: |
F16C 19/00 20060101
F16C019/00 |
Claims
1. A bearing comprising: a first ring having a first raceway
constructed from a first metal or metal alloy; a second ring having
a second raceway constructed from a second metal or metal alloy; a
plurality of roller elements positioned between the first raceway
and the second raceway; and a lubricant disposed between the first
raceway and the second raceway, the lubricant containing a
plurality of suspended nanoparticles; wherein the suspended
nanoparticles are comprised of a third metal or metal alloy that is
more anodic than the first metal or metal alloy.
2. The bearing of claim 1, wherein the third metal or metal alloy
is more anodic than the second metal or metal alloy.
3. The bearing of claim 1, further comprising: a first layer of a
nanoparticle film disposed on at least a portion of the first
raceway, the nanoparticle film is comprised of the suspended
nanoparticles.
4. The bearing of claim 1, wherein the nanoparticles comprise zinc
or zinc alloy.
5. The bearing of claim 4, wherein an average diameter of the
suspended nanoparticles is approximately 10 nanometers.
6. The bearing of claim 4, wherein a diameter of the suspended
nanoparticles is between approximately 10 nanometers and a maximum
diameter entrainable between the roller and raceway.
7. The bearing of claim 6, wherein the maximum diameter entrainable
between the roller and raceway is governed by the equation
R.sub.max={[(r.sub.i+R).sup.2+4.mu..sup.2Rr.sub.i].sup.1/2-(r.sub.i+R)}/2-
, where R.sub.max denotes the radius of the largest particle that
the can be entrained.
8. The bearing of claim 4, wherein a concentration of the suspended
nanoparticles in the lubricant is from about 0.2 percent to about
0.5 percent by weight.
9. The bearing of claim 4, wherein a concentration of the suspended
nanoparticles in the lubricant is from about 0.2 percent to about
2.0 percent by weight.
10. The bearing of claim 4, wherein a concentration of the
suspended nanoparticles in the lubricant is from about 2.0 percent
to about 7.0 percent by weight.
11. A bearing comprising: a first ring having a first raceway
constructed from a first metal or metal alloy; a second ring having
a second raceway constructed from a second metal or metal alloy; a
plurality of roller elements positioned between the first raceway
and the second raceway; a first layer of a nanoparticle film
disposed on at least a portion of the first raceway, wherein the
nanoparticle film is comprised of a plurality of metal or metal
alloy nanoparticles that are more anodic than the first metal or
metal alloy.
12. The bearing of claim 11, wherein the nanoparticles comprise
zinc or zinc alloy.
13. The bearing of claim 12, wherein an average diameter of the
nanoparticles is approximately 10 nanometers.
14. The bearing of claim 12, wherein a diameter of the
nanoparticles is between approximately 10 nanometers and a maximum
diameter entrainable between the roller and raceway.
15. The bearing of claim 14, wherein the maximum diameter
entrainable between the roller and raceway is governed by the
equation
R.sub.max={[(r.sub.i+R).sup.2+4.mu..sup.1/2Rr.sub.i].sup.1/2-(r.sub.i+R)}-
/2, where R.sub.max denotes the radius of the largest particle that
the can be entrained.
16. The bearing of claim 12, wherein the nanoparticle film is
approximately 0.0002 inches thick.
17. The bearing of claim 12, wherein the nanoparticle film contains
a concentration of nanoparticles from about 0.2 percent to about
2.0 percent by weight.
18. The bearing of claim 12, wherein the nanoparticle film is from
about 0.00002 inches to about 0.0025 inches thick.
19. The bearing of claim 11, wherein the nanoparticle film covers
the entire first raceway.
20. The bearing of claim 11, further comprising a second layer of a
nanoparticle film disposed on at least a portion of the second
raceway, wherein the nanoparticle film is comprised of a plurality
of metal or metal alloy nanoparticles that are more anodic than the
second metal or metal alloy.
21. The bearing of claim 20, wherein the nanoparticle film covers
the entire second raceway.
22. A bearing comprising: a first ring having a first raceway
having a first outer surface, the first raceway being constructed
from a first metal or metal alloy; a second ring having a second
raceway having a second outer surface, the second raceway being
constructed from a second metal or metal alloy; a plurality of
roller elements positioned between the first raceway and the second
raceway; and a lubricant disposed between the first raceway and the
second raceway containing a plurality of suspended nanoparticles;
wherein the suspended nanoparticles are comprised of a third metal
or metal alloy that is more anodic than the first metal or metal
alloy; and wherein the suspended nanoparticles fill at least some
imperfections or pits in the first outer surface.
23. The bearing of claim 22, wherein the third metal or metal alloy
is more anodic than the second metal or metal alloy.
24. The bearing of claim 22, wherein the suspended nanoparticles
fill a majority of the imperfections or pits in the first outer
surface.
25. The bearing of claim 22, wherein the suspended nanoparticles
fill at least some imperfections or pits in the second outer
surface.
26. The bearing of claim 25, wherein the suspended nanoparticles
fill a majority of the imperfections or pits in the second outer
surface.
27. A method of lubricating a bearing, wherein the bearing
comprises a first ring having a first raceway constructed of a
first metal or metal alloy and a second ring having a second
raceway constructed of a second metal or metal alloy, the first
raceway and the second raceway forming a channel therebetween,
comprising the steps of: disposing within the channel a lubricant
containing a plurality of suspended nanoparticles; and forming a
first nanoparticle film on at least a portion of the first raceway,
the first nanoparticle film being formed from the suspended
nanoparticles; wherein the suspended nanoparticles and the first
nanoparticle film are comprised of a third metal or metal alloy
that is more anodic than the first metal or metal alloy.
28. The bearing of claim 27, wherein the first nanoparticle film is
formed by moving the roller elements over the first raceway.
29. The method of claim 27, further comprising: forming a second
nanoparticle film on at least a portion of the second raceway, the
second nanoparticle film being formed from the suspended
nanoparticles; wherein the third metal or metal alloy is more
anodic than the second metal or metal alloy.
30. The bearing of claim 29, wherein the second nanoparticle film
is formed by moving the roller elements over the second
raceway.
31. The bearing of claim 27, wherein the nanoparticles comprise
zinc or zinc alloy.
32. The bearing of claim 31, wherein an average diameter of the
suspended nanoparticles is approximately 10 nanometers.
33. The bearing of claim 31, wherein a diameter of the suspended
nanoparticles is between approximately 10 nanometers and a maximum
diameter entrainable between the roller and raceway.
34. The bearing of claim 33, wherein the maximum diameter
entrainable between the roller and raceway is governed by the
equation
R.sub.max={[(r.sub.i+R).sup.2+4.mu..sup.2Rr.sub.i].sup.1/2-(r.sub.i+R)}/2-
, where R.sub.max denotes the radius of the largest particle that
the can be entrained.
35. The bearing of claim 31, wherein the nanoparticle film is
approximately 0.0002 inches thick.
36. The bearing of claim 31, wherein the lubricant contains a
concentration of nanoparticles from about 0.2 percent to about 2.0
percent by weight.
37. The bearing of claim 31, wherein the nanoparticle film is from
about 0.00002 inches to about 0.0025 inches thick.
38. The bearing of claim 31, wherein a concentration of the
suspended nanoparticles in the lubricant is from about 0.2 percent
to about 0.5 percent by weight.
39. The bearing of claim 31, wherein a concentration of the
suspended nanoparticles in the lubricant is from about 0.2 to about
1.0 percent by weight.
40. The bearing of claim 31, wherein a concentration of the
suspended nanoparticles in the lubricant is from about 2.0 percent
to about 7.0 percent by weight.
41. The method of claim 27, further comprising: disposing within
the channel additional lubricant containing a plurality of
suspended nanoparticles; and forming a further first nanoparticle
film on at least a portion of the first raceway, the further first
nanoparticle film being formed from the suspended nanoparticles;
wherein the further first nanoparticle film is comprised of the
third metal or metal alloy.
42. The bearing of claim 41, wherein the further first nanoparticle
film is formed by moving the roller elements over the first
raceway.
43. The method of claim 41, further comprising: forming a further
second nanoparticle film on at least a portion of the second
raceway, the further second nanoparticle film being formed from the
suspended nanoparticles; wherein the further second nanoparticle
film is comprised of the third metal or metal alloy.
44. The bearing of claim 43, wherein the further second
nanoparticle film is formed by moving the roller elements over the
second raceway.
45. A device comprising: a first component constructed from a first
metal or metal alloy; a second component constructed from a second
metal or metal alloy, wherein the second component is in sliding or
rolling contact with an area of the first component; and a first
layer of a nanoparticle film disposed on at least a portion of the
area of the first component, wherein the nanoparticle film is
comprised of a plurality of metal or metal alloy nanoparticles that
are more anodic than the first metal or metal alloy.
46. The device of claim 45, wherein the nanoparticles comprise zinc
or zinc alloy.
47. The device of claim 46, wherein the nanoparticle film is
approximately 0.0002 inches thick.
48. The device of claim 46, wherein the nanoparticle film is from
about 0.00002 to about 0.0025 inches thick.
49. The device of claim 46, wherein the nanoparticle film contains
a concentration of nanoparticles from about 0.2 percent to about
2.0 percent by weight.
50. A lubricant comprising nanoparticles that are anodic to steel
in a concentration from about 0.2 percent to about 2.0 percent by
weight.
51. The lubricant of claim 50 wherein the nanoparticles are
comprised of zinc or zinc alloy.
52. A lubricant comprising nanoparticles that are anodic to steel
in a concentration from about 2.0 percent to about 7.0 percent by
weight.
53. The lubricant of claim 52 wherein the nanoparticles are
comprised of zinc or zinc alloy.
Description
FIELD OF INVENTION
[0001] The present invention is directed generally to lubricants,
and more particularly to lubricants used in rolling contacts, such
as in ball and roller bearings.
BACKGROUND OF THE INVENTION
[0002] In many applications, bearings encounter hostile, corrosive
operating environments and high repetition use. Corrosion, rolling
contact fatigue, and loss of lubricant may reduce bearing life.
Corrosion of steel in bearings may result in high maintenance costs
and equipment down time while costly repairs or replacements are
made. The high repetition inherent in bearing use causes fatigue in
the bearing elements and the raceways. Additionally, in use,
lubricant escapes from bearings, resulting in frequent maintenance
and possible equipment downtime while lubricant is reapplied. It is
thus desirable to have an invention that protects against
corrosion, promotes long fatigue life, and can be applied to
machine elements with minimum equipment downtime.
[0003] One known method of corrosion protection is to cover a
material with a protective coating to physically separate the
material from exposure to a potentially corrosive environment. For
example, methods have been taught to combat corrosion through the
application of a zinc plating to raceway and roller bearing
surfaces. As disclosed in U.S. Pat. No. 5,352,046, for example,
zinc or zinc alloy plated layers are applied to contact surfaces by
an electroplating process. This electroplating process is
disadvantageous, however, because it adds expense and time to the
manufacturing process. Corrosion protection of bearings and
raceways has also been attempted through multilayer plating and
protection systems, as disclosed in U.S. Pat. No. 6,062,735, for
example.
[0004] Disadvantageously, the application of these multiple layers
requires even more time and manufacturing expense than the
application of a single plated layer of zinc or zinc alloy. In
addition, neither U.S. Pat. No. 5,352,046 nor U.S. Pat. No.
6,062,735 discloses protection that can be readily applied or
retrofitted to bearings already in use.
[0005] Another method of corrosion protection is anodic protection.
Anodic protection involves the use of a more anodic, or active,
metal to coat and protect a metal that is less anodic. In some
applications, one advantage of anodic protection is that breaks or
scratches in the more anodic metal coating do not cause the
underlying less anodic metal to corrode.
[0006] The term anodic metal refers to the tendency of dissimilar
materials to ionize or corrode. The relative corrosive tendencies
of many dissimilar metals and metal alloys are predictable and have
been tabulated in what is commonly known as a galvanic series, an
example of which can be found at ASTM G82-98.
[0007] Metals and metal alloys are arranged in the galvanic series
from least anodic to most anodic. When dissimilar metals or metal
alloys are coupled such that electrons can flow between them,
electrons will flow from the more anodic metal or metal alloy to
the less anodic metal or metal alloy. This electron flow is
accompanied by ionization of the more anodic metal or metal alloy
that leads to corrosion of the more anodic metal or metal alloy.
Consequently, the more anodic metal or metal alloy can corrode but
the underlying, less anodic material does not.
[0008] Other inventions have sought to increase lubricant retention
through the use of solid lubricants or metal-containing pastes.
However, as disclosed in U.S. Pat. No. 4,363,737, for example,
these pastes do not provide anodic protection against corrosion.
This patent also ignores the necessity to entrain soft solid metal
particles in a lubricated contact in order to form transfer films
on the contacting bodies. The patent recommends a metal particle
content of at least thirty-five percent by weight, and does not
specify the size of the metal particles in the paste. Both particle
size and concentration strongly affect entrainment of particles. In
addition, Qiu, "Preparation of Ni Nanoparticles and Evaluation of
Their Tribological Performance As Potential Additives in Oils,"
discloses the use of Nickel nanoparticles as additives in
lubricating oils to improve their load bearing capacity and
friction and wear characteristics. Qiu does not, however, disclose
the use of nanoparticles to provide anodic protection against
corrosion.
[0009] Accordingly, there is a need for a lubricant for bearings
and other machine elements that provides anodic protection against
corrosion. In addition, there is a need to provide a lubricant for
bearings and other machine parts that provides a soft coating on
bearing raceways to improve rolling contact fatigue life. There is
also a need to provide a lubricant for bearings and other machine
elements that is easy to apply to bearings that are already in
use.
SUMMARY OF THE INVENTION
[0010] In accordance with these goals, the present embodiments
provide a bearing lubricant that includes metal or metal alloy
nanoparticles that are more anodic than the metal or metal alloy of
which the inner and outer raceways of the bearing are constructed.
In addition, the present embodiments provide a lubricant for
bearings and other machine parts that provides a soft coating on
bearing raceways to improve rolling contact fatigue life. The
lubricant is easy to apply to bearings that are already in use and
may replace corroded anodic metal or metal alloy coating within the
bearing. Although, particularly useful in the field of bearings the
lubricant and lubricant films or coatings with suspended
nanoparticles described herein may also be useful in other
applications, particularly in any environment where there is
rolling or sliding contact between contacting pieces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Further advantages of the present invention will become
apparent to those skilled in the art with the benefit of the
following detailed description of the preferred embodiments and
upon reference to the accompanying drawings in which:
[0012] FIG. 1A is a cross-sectional view of a bearing element with
an inner and outer ring, raceways, and a plurality of roller
elements;
[0013] FIG. 1B is a cross-sectional view of a bearing element with
an inner and outer ring, raceways, and a plurality of roller
elements;
[0014] FIG. 2 is a magnified side view of a section of a bearing
element with a roller element, raceways, and suspended anodic metal
or metal alloy nanoparticles;
[0015] FIG. 3 is a magnified side view of a section of a bearing
element with a roller element, suspended anodic metal or metal
alloy nanoparticles, and raceways with a coating of anodic metal or
metal alloy nanoparticle film;
[0016] FIG. 4 is a magnified side view of a section of a bearing
element with a roller element, suspended anodic metal or metal
alloy nanoparticles, and raceways with a coating of anodic metal or
metal alloy nanoparticle film filling in some of the pits and
imperfections on the raceways;
[0017] FIG. 5 is a magnified side view of a section of a bearing
element with a roller element, suspended anodic metal or metal
alloy nanoparticles, and raceways with portions of the raceways
covered with multiple layers of anodic metal or metal alloy
nanoparticle film, and
[0018] FIG. 6 is a magnified top view of a section of a bearing
element with a roller element, suspended anodic metal or metal
alloy nanoparticles, and a raceway with portions of the raceway
covered with an anodic metal or metal alloy nanoparticle film.
[0019] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof are shown by
way of example in the drawings and will herein be described in
detail. It should be specifically understood with respect to the
drawings that the drawings are of preferred alternate embodiments,
and there are many other embodiments and forms in which the present
invention may appear. It should also be understood that the
drawings and detailed description thereof are not intended to limit
the invention to the particular form disclosed, but on the
contrary, the invention is to cover all modifications, equivalents,
and alternatives falling within the spirit and scope of the present
invention or within the scope of the appended claims.
[0020] The invention could benefit operation of any device in which
interacting surfaces allow formation of a partial or complete
surface film from the nanoparticles suspended in the lubricant.
[0021] In addition, while the present invention is particularly
useful in harsh operating condition applications, the present
invention may be used for any other application where the use of
anodic metal or metal alloy nanoparticles would be suitable.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] FIG. 1A depicts a cross-sectional view of a bearing element
50, and FIG. 1B depicts a cross-sectional view of the bearing of
FIG. 1A taken along the line A-A. As shown in FIGS. 1A and 1B, a
typical bearing element 50 comprises an inner ring 30 and an outer
ring 40. The inner ring 30 and outer ring 40 are typically made
from hardened steel, but other materials such as stainless steel,
plastics, and ceramics can also be used, especially in corrosive
environments. In FIGS. 1A and 1B, inner ring 30 and outer ring 40
include inner raceway 60 and outer raceway 65, contain or partially
contain roller elements 10, and provide a surface upon which roller
elements 10 travel during use. The raceway of the inner ring can be
made of the same material as the raceway of the outer ring, or they
can be made of different materials. The use of the term "first
metal or metal alloy" and "second metal or metal alloy" as used
herein covers both. Thus, the first metal or metal alloy may be
either the same as or different from the second metal or metal
alloy. Roller elements 10 can be any type of rolling element used
in a bearing, including but not limited to any type of ball,
roller, needle, or thrust bearing. In a typical application, a
plurality of roller elements 10 are arranged in a bearing element
50 that supports or aligns rotating shafts or other machine
elements.
[0023] FIG. 2 depicts a magnified side view of a section of a
bearing element 50. As shown in FIG. 2, a roller element 10 is in
communication with inner raceway 60 and outer raceway 65. FIG. 2
also shows a magnified view of the imperfections 62 on the surface
of raceways 60 and 65. Anodic metal or metal alloy nanoparticles 70
are shown suspended in a lubricant 80 (filling the area between the
raceways 60 and 65).
[0024] The lubricant 80 including suspended anodic metal or metal
alloy nanoparticles 70 partially fills the areas between the roller
elements 10 and the raceways 60 and 65. The lubricant 80 would
ideally be a grease or extreme pressure grease suitable for use in
hostile conditions, such as Shell Albania EP2 Grease, to which
anodic metal or metal alloy nanoparticles 70 are added. The use of
other lubricants such as lubricating oils, pastes, or other fluids
or solids is also contemplated by the present invention.
[0025] Because the anodic metal or metal alloy nanoparticles 70 are
suspended in a lubricant 80, the present invention is particularly
suited for use in existing bearings or even bearings that are
already in operation. As with known methods of lubrication of
operational bearing elements, the lubricant 80 including suspended
anodic metal or metal alloy nanoparticles 70 can be injected into a
bearing through conventional grease fittings, with which bearings
are typically equipped. Thus, one advantage of the present
invention over the prior art is apparent. Prior art systems for
corrosion protection, such as electroplating a zinc-nickel layer on
raceways as disclosed in U.S. Pat. No. 5,352,046, require the
application of a zinc plated layer during the bearing manufacturing
process. Further it is uneconomical and prohibitively expensive to
electroplate a zinc-nickel layer on the raceways of existing
bearings. It is necessary to remove that bearing from use and
carefully clean the surface to be plated. This requires expensive
machine downtime and labor.
[0026] One embodiment of the present invention contemplates that
bearings will be lubricated with the anodic lubricant at the time
of manufacture. Furthermore, unlike zinc-plated bearings, the
anodic lubricant may also be applied to existing bearings and even
bearings in operation by simply packing the bearings with the
anodic lubricant.
[0027] As shown in FIG. 2, nanoparticles 70 have a generally
spherical shape, but nanoparticles 70 having any shape befitting
the spirit of the invention is contemplated. In general, a size and
shape that facilitates distribution of the nanoparticles 70 in the
lubricant 80 is most desirable. The nanoparticle concentration is
preferably between 0.2% and 2%. It is most preferable to use
nanoparticles 70 with concentrations from 0.2% to 0.5% in a
lubricant 80. However, it would also be possible to obtain the
advantages of the inventions using concentrations of nanoparticles
from 2% to 7%. As used herein, all references to concentrations and
percentages refer to percentage of concentration measured by
weight. Preferably, the average size of nanoparticles 70, while
suspended in lubricant 80, is approximately 10 nm in diameter, but
larger nanoparticles might be used. The entrainment of a particle
into a contact between two cylinders, such as the roller and
raceway of a roller bearing depends on the radii of the roller, R,
and raceway, r.sub.i, as well as on the friction coefficient, .mu.,
according to the equation
R.sub.max={[(r.sub.i+R).sup.2+4.mu..sup.2Rr.sub.i].sup.1/2-(r.sub.i+R)}/2
Where R.sub.max denotes the radius of the largest particle that the
contact can entrain.
[0028] As an example, a roller bearing having roller radius
R=0.0315 inches, inner race radius r.sub.i=0.29135 inches, and
coefficient of friction between particle and race and between
particle and roller .mu.=0.01, could entrain a particle of
R.sub.max=70 microns, or 140 microns in diameter. Where a higher
coefficient of friction exists, the roller/race contact could
entrain larger particles in the thin film of lubricant.
[0029] In common use and as used herein, the term nanoparticle
refers to a particle 50 nm or less in size, measured in any
direction. Nanoparticles are manufactured by companies such as
Aveka Group of Woodbury, Minn.
[0030] In an exemplary embodiment, nanoparticles 70 are anodic
relative to the material comprising the raceways 60 and 65.
Preferably, zinc or zinc alloy nanoparticles 70 can be used, and
are anodic to a steel raceway 60. Other combinations of materials
encompassed by the present invention can be ascertained through
reference to a galvanic series table, such as ASTM G82-98,
incorporated herein by reference.
[0031] FIG. 3 depicts a magnified side view of bearing element 50
with an anodic metal or metal alloy nanoparticle film 90 on at
least a portion of the raceways 60 and 65. As contemplated by the
present invention, the movement of roller elements 10 on raceways
60 and 65 acts on the nanoparticles 70-to form a film 90 on at
least a portion of the raceways 60 or 65. It should be evident that
nanoparticle film 90 may gradually form as the movement of the
roller elements 10 on raceways 60 and 65 continues to act on
nanoparticles 70. In addition, a layer or multiple layers of
nanoparticle film 90 may be formed simply by applying an oil or
grease that contains nanoparticles 70 to the raceways 60 or 65. An
oil or grease with nanoparticles 70 can be applied by spraying,
coating, or other methods. In any event, nanoparticle film 90 forms
a coating on at least a portion of the raceways 60 or 65 and
protects raceways 60 or 65 from the environment and prevents the
coated portions of raceways 60 or 65 from contacting corrosive
environmental conditions.
[0032] The nanoparticle film 90 is comprised of anodic metal or
metal alloy nanoparticles 70. Because the nanoparticle film 90 is
anodic relative to the material comprising the outer surface of the
raceways 60 and 65, the anodic nanoparticle film 90 will have a
tendency to corrode relative to the material comprising the outer
surface of the raceways 60 and 65. In addition, because the
nanoparticle film 90 is anodic relative to the material comprising
the outer surface of the raceways 60 and 65, it is not necessary,
for corrosion protection, for the nanoparticle film 90 to form a
continuous surface over the entire material comprising the outer
surface of the raceways 60 and 65. Breaks, chips, or
discontinuities in the nanoparticle film 90 will not cause the
material comprising the outer surface of the raceways 60 or 65 to
corrode. Instead, the nanoparticle film 90, as opposed to the
raceways 60 and 65, will still have a tendency to corrode, even if
breaks or discontinuities are present.
[0033] In addition, the present invention is advantageous because a
corroded nanoparticle film 90 can easily be replaced. The present
invention is particularly suited for bearings that are in
operation. Additional lubricant 80 containing nanoparticles 70 may
be added to a bearing as needed or as part of a regular maintenance
schedule. The movement of roller elements 10 on raceways 60 and 65
will continue to act on the nanoparticles 70 to form a nanoparticle
film 90 on the raceways 60 and 65 or on any existing layers of
nanoparticle film 90. As the nanoparticle film 90 forms, corroded
portions of the anodic metal or metal alloy nanoparticle film 90
will be replaced.
[0034] Another advantage of the present invention is that it
improves the anti-wear and anti-friction characteristics of the
roller elements 10 and the raceways 60 and 65. On the portions of
the raceways 60 and 65 where the nanoparticle film 90 is present,
the nanoparticle film 90 prevents a roller element 10 from directly
contacting the raceways 60 and 65. In many applications, especially
when the raceways 60 and 65 comprise hardened steel, the
nanoparticle film 90 will also be a softer surface on which a
roller element 10 will act. As shown in FIG. 3 and more
particularly in FIG. 4, the nanoparticles 70, and hence the
nanoparticle film 90, also fill the pits 62 and other imperfections
in the surface of raceways 60 and 65, thereby smoothing the
surfaces of raceways 60 and 65. As a result of the improved
anti-wear and anti-friction characteristics of roller elements 10
and raceways 60 and 65, the present invention improves the fatigue
life of bearing element 50.
[0035] To lengthen fatigue life, a thickness of the anodic metal or
metal alloy nanoparticle film is approximately 0.0002 inches,
although other thicknesses such as those ranging from 0.00002 to
0.0025 inches, are possible as well. A discussion of soft coatings
can be found in the book, STLE Life Factors for Rolling Bearings,
written by Zaretsky, and incorporated herein by reference. In
addition, to maximize anti-wear and anti-friction properties of the
raceway, a nanoparticle film 90 completely covering the raceway 60
is ideal. Fatigue life will improve, however, even if the
nanoparticle film 90 does not completely cover the raceways 60 or
65.
[0036] FIG. 5 depicts a magnified side view of bearing element 50.
The anodic metal or metal alloy nanoparticle film 90 may be formed
both on portions of the raceways 60 or 65 as well as on portions of
the anodic metal or metal alloy nanoparticle film 90 surface.
Further, multiple layers of anodic metal or metal alloy
nanoparticle film 90 may thus form as additional lubricant 80
containing suspended anodic metal or metal alloy nanoparticles 70
is added to the bearing 50, during, for example, maintenance or
re-greasing. It should also be evident that a gradual addition of
lubricant 80 containing suspended anodic metal or metal alloy
nanoparticles 70 will lead to a more gradual build-up of
nanoparticle film 90 and further, additional layers-of nanoparticle
film 90.
[0037] FIG. 6 depicts a magnified top view of bearing element 50
with a roller element 10 positioned over inner raceway 60 with
suspended nanoparticles 70. As can be seen in this figure, the
anodic metal or metal alloy nanoparticle film 90 forms on portions
of the raceway 60. Ideally, the entire raceways 60 and 65 will be
covered with a coating of anodic nanoparticle film 90. However, as
shown in FIG. 6, even partial coverage of the raceways 60 or 65
will provide anodic protection as well as provide antiwear and
antifriction benefits to the raceway.
[0038] While certain features and embodiments of the invention have
been described herein, it will be readily understood that the
invention encompasses all modifications and enhancements within the
scope and spirit of the present invention.
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