U.S. patent application number 11/030077 was filed with the patent office on 2005-06-09 for roller bearing.
This patent application is currently assigned to NSK Ltd.. Invention is credited to Fujita, Yasunobu, Kimura, Keisuke, Naka, Michiharu.
Application Number | 20050124511 11/030077 |
Document ID | / |
Family ID | 26571491 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050124511 |
Kind Code |
A1 |
Fujita, Yasunobu ; et
al. |
June 9, 2005 |
Roller bearing
Abstract
Enhanced fretting resistance, high-speed capability, and service
live are achieved by a roller bearing comprised of a plurality of
rolling elements held between inner and outer races with a cage
interposed therebetween, and wherein oil film of lubricating oil of
which the dynamic viscosity at 40.degree. C. is 20 to 150
mm.sup.2/s, and which preferably contains an extreme pressure agent
and a corrosion preventing agent, is formed on the raceway surfaces
of the inner and outer races, the cage and the rolling elements and
grease is enclosed.
Inventors: |
Fujita, Yasunobu;
(Fujisawa-shi, JP) ; Kimura, Keisuke;
(Fujisawa-shi, JP) ; Naka, Michiharu;
(Fujisawa-shi, JP) |
Correspondence
Address: |
MILES & STOCKBRIDGE PC
1751 PINNACLE DRIVE
SUITE 500
MCLEAN
VA
22102-3833
US
|
Assignee: |
NSK Ltd.
|
Family ID: |
26571491 |
Appl. No.: |
11/030077 |
Filed: |
January 7, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11030077 |
Jan 7, 2005 |
|
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09199447 |
Nov 25, 1998 |
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Current U.S.
Class: |
508/364 ;
508/365; 508/371; 508/378; 508/379 |
Current CPC
Class: |
C10M 2207/1265 20130101;
C10M 2207/2855 20130101; C10M 2207/281 20130101; C10M 2207/2825
20130101; C10M 2223/04 20130101; C10M 2207/1225 20130101; C10M
2209/00 20130101; C10M 135/10 20130101; C10M 2207/282 20130101;
C10N 2040/02 20130101; C10M 105/38 20130101; C10M 2207/129
20130101; C10M 2215/30 20130101; C10M 2219/09 20130101; C10M 105/18
20130101; C10M 2207/284 20130101; C10M 2207/285 20130101; C10M
2207/286 20130101; C10M 2207/021 20130101; C10M 2207/283 20130101;
C10M 2205/02 20130101; C10M 2209/104 20130101; C10M 2215/226
20130101; C10M 2207/125 20130101; C10M 2223/045 20130101; C10M
137/10 20130101; C10M 2207/024 20130101; C10M 137/02 20130101; C10M
2207/2835 20130101; C10M 2209/02 20130101; C10M 2215/225 20130101;
C10N 2010/12 20130101; C10M 2215/221 20130101; C10M 105/36
20130101; C10M 2207/34 20130101; C10M 2215/04 20130101; C10M
2219/068 20130101; C10M 2201/085 20130101; C10M 107/02 20130101;
C10M 117/02 20130101; C10M 169/00 20130101; C10M 2215/22 20130101;
C10M 2223/02 20130101; C10M 2223/049 20130101; C10M 125/24
20130101; C10M 2207/0406 20130101; C10M 2207/166 20130101; C10M
2207/289 20130101; C10M 2207/246 20130101; C10M 2223/10 20130101;
C10M 2209/10 20130101; C10M 2223/042 20130101; C10M 2205/0206
20130101; C10M 2207/04 20130101; C10M 2219/044 20130101; C10N
2010/02 20130101; C10M 2207/186 20130101; C10M 2207/026 20130101;
C10M 2207/206 20130101; C10N 2010/04 20130101; C10M 2215/26
20130101 |
Class at
Publication: |
508/364 ;
508/365; 508/371; 508/378; 508/379 |
International
Class: |
C10M 169/04; C10M
169/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 26, 1997 |
JP |
9-324446 |
Nov 24, 1998 |
JP |
10-332635 |
Claims
1. A fretting resisting spindle support roller bearing of a
low-torque spindle drive, comprising a plurality of rolling
elements held between inner and outer races with a cage interposed
therebetween, wherein an oil film of lubricating oil of which a
dynamic viscosity at 40.degree. C. is at least 120 and not
exceeding 150 mm.sup.2/s and effective to improve fretting
resisting properties, and which contains an extreme pressure agent
and a corrosion preventing agent, is formed on raceway surfaces of
the inner and outer races, said cage and said rolling elements, and
wherein a grease is enclosed.
2. A fretting resisting roller bearing according to claim 1,
wherein said inner and outer races are made of steel and said
rolling elements are made of ceramics.
3. A fretting resisting roller bearing according to claim 1,
wherein said inner and outer races are made of steel and said
rolling elements are made of an alloy of greater hardness than said
inner and outer races.
4. A fretting resisting roller bearing according to claim 2,
wherein said rolling elements have a Vickers hardness of at least
1300.
5. A fretting resisting roller according to claim 4, wherein said
extreme pressure agent is an organic metallic salt.
6. A fretting resisting roller bearing according to claim 5,
wherein said organic metallic salt is selected from the group
consisting of molybdenum thiocarbamate, molybdenum dithio
phosphate, zinc thiocarbamate, and zinc dithiophosphate.
7. A fretting resisting roller bearing according to claim 4,
wherein said corrosion preventing agent is selected from the group
consisting of phosphoric acid ester and phosphorous acid ester.
8. A fretting resisting roller bearing according to claim 4,
wherein said corrosion preventing agent is molybdenum
dithiocarbamate.
9. A fretting resisting roller bearing according to claim 3,
wherein said rolling elements have a Vickers hardness of at least
1300.
10. A fretting resisting roller bearing according to claim 9,
wherein said extreme pressure agent is an organic metallic
salt.
11. A fretting resisting roller bearing according to claim 10,
wherein said organic metallic salt is selected from the group
consisting of molybdenum thiocarbamate, molybdenum dithiophosphate,
zinc thiocarbamate, and zinc dithiophosphate.
12. A fretting resisting roller bearing according to claim 1,
wherein said extreme pressure agent is an organic metallic
salt.
13. A fretting resisting roller bearing according to claim 12,
wherein said organic metallic salt is selected from the group
consisting of molybdenum thiocarbamate, molybdenum dithio
phosphate, zinc thiocarbamate, and zinc dithiophosphate.
14. A fretting resisting roller bearing according to claim 1,
wherein said corrosion preventing agent is selected from the group
consisting of phosphoric acid ester and phosphorous acid ester.
15. A fretting resisting roller bearing according to claim 1,
wherein said corrosion preventing agent is molybdenum
dithiocarbamate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a roller bearing, and particularly
to a roller bearing for a spindle which is a portion of the
constituent parts of various motors or the like and which exhibits
an excellent bearing characteristic and a greatly mitigated
susceptability fretting corrosion created by repeated shock and
swing attributable to extraneous vibration as during
conveyance.
[0003] 2. Related Background Art
[0004] The industry related to electrical instruments is
experiencing a rapid rate of technological innovation as compared
with the other industrial fields. The available periods of
particular types of machines are short, and new types of machines
introducing techniques (smaller electric power consumption, higher
responsiveness, higher accuracy, compactness, etc.) are being
developed one after another.
[0005] The bearings for the spindles of various motors or the like
have been required to provide higher speed capability with the
development of the new types of machines as described above, and
lower torque has come to be required of them for the purpose of
smaller electric power consumption. In the roller bearings used for
the spindles according to the prior art, there have been adopted a
lubricating portion filled with grease, and a method of applying
lubricating oil to the raceway surface or the like of the bearing
and further enclosing grease therein. At present, for the purpose
of lower torque to accommodate the requirement for smaller electric
power consumption as described above, an amount of grease is
reduced, and as lubricating oil applied to the raceway surface or
the like of the bearing, many lubricating oils of low dynamic
viscosity (dynamic viscosity of 5 to 15 mm.sup.2/s at 40.degree.
C.) are used for rust prevention and low torque.
[0006] The shipment of various motors often takes place on land,
and they are transported in an environment in which they are apt to
be subjected to extraneous vibrations. By these extraneous
vibrations, the bearings for the spindles suffer from axial
vibration or repeated circumferential swing depending on the way in
which the instruments are placed.
[0007] When such axial vibration or circumferential swinging
movement is repeated, a bearing for a spindle designed for torque
may be subjected to fretting corrosion on the raceway surfaces of
the outer race and inner race thereof and the contact surfaces of
the rolling elements thereof, because the quantity of grease is
small and the strength of oil film is low in lubricating oil of low
dynamic viscosity.
[0008] The creation of fretting corrosion may result in an increase
in the sound and vibration of the bearing and may also pose a
serious hinderance to further improvement in required accuracy.
[0009] So, the present invention has been made in order to prevent
the creation of fretting corrosion in a bearing for a spindle
during the conveyance of various motors as noted above, and a
principal object thereof is to provide a fretting-resisting roller
bearing which is not adversely affected in its characteristics and
achieves a higher temperature and a higher speed as well as a
longer life.
SUMMARY OF THE INVENTION
[0010] To achieve the above object, the roller bearing of the
present invention is a roller bearing comprised of a plurality of
rolling elements held between an inner race and an outer race with
a cage interposed therebetween, characterized in that an oil film
of lubricating oil of which the dynamic viscosity at 40.degree. C.
is 20 to 150 mm.sup.2/s is formed on the raceway surfaces of the
inner and outer races, the cage and the rolling elements and grease
is enclosed.
[0011] The roller bearing of the present invention is heightened in
the dynamic viscosity of the lubricating oil and the strength of
the oil film with a view to improve the fretting-resisting property
during the conveyance of various motors.
[0012] Also, for example, the rolling elements are made of ceramics
or a super-hard alloy of which the Vickers hardness is 1300 or
greater, and the outer race and inner race are made of steel.
Preferably, a material differing from that of the outer race and
inner race is used as the material of the rolling elements and the
hardness thereof is increased, whereby not only fretting corrosion
can be suppressed by the prevention of the adhesion phenomenon
between the members (the raceway surfaces of the outer and inner
races and the rolling elements) and the decrease in Hertzian
contact area due to the difference in Young's modulus, but also a
good function is obtained even under use conditions of high
temperature and high-speed rotation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a graph showing the acceleration signal execution
values of each embodiment and each comparative example.
[0014] FIG. 2 is a graph showing the rotation torques of each
embodiment and each comparative example.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] Some embodiments of the fretting-resisting roller bearing of
the present invention will hereinafter be described in detail.
[0016] The fretting-resisting roller bearing of the present
invention is a roller bearing comprised of a plurality of rolling
elements held between an inner race and an outer race with a cage
interposed therebetween, wherein an oil film of lubricating oil of
which the dynamic viscosity at 40.degree. C. is 20 to 150
mm.sup.2/s is formed on the raceway surfaces of the inner and outer
races, the cage and the rolling elements, and grease is
enclosed.
[0017] When the dynamic viscosity of the lubricating oil at
40.degree. C. is less than 20 mm.sup.2/s, the strength of the oil
film is low and fretting corrosion is liable to be created by
extraneous vibrations. When conversely, the dynamic viscosity at
40.degree. C. is higher than 150 mm.sup.2/s, rotation torque
increases because the dynamic viscosity of the lubricating oil is
high. Further, to reduce fretting corrosion, it is preferable that
the dynamic viscosity at 40.degree. C. be 40 mm.sup.2/s or
greater.
[0018] While the lubricant composition used as the lubricating oil
is not particularly limited, it may be composed of base oil and
various additives mentioned below, whereby there is formed
lubricating oil film having a fretting-resisting property and a
rust prevention property and suitable for use at a high
temperatures and high speeds. In the embodiments as described
hereinafter, the composition of the additives can be selected in
accordance with use conditions of the bearings if control of
fretting corrosion is maintained, and anti-rust properties and
additional properties also be provided. Particularly, if the higher
anti-rust properties are required under some use conditions,
preferably the lubricant oil may be anti-rust lubricant oil
containing a rust prevention agent which has high anti-rust
properties.
[0019] (Base Oil)
[0020] Regarding the base oil, as ester oil, use may preferably be
made of diester oil obtained from the reaction of dibasic acid and
branch alcohol, aromatic ester oil obtained from the reaction of
aromatic tribasic acid and branch alcohol, or hindered ester oil
obtained from the reaction of polyatomic alcohol and monobasic
acid.
[0021] As diester oil, mention may be made of dioctyl adipate
(DOA), diisobutyl adipate (DIBA), dibutyl adipate (DBA), dioctyl
azelate (DOZ), dibutyl sebacate (DBA), dioctyl sebacate (DOS),
methyl acetyl recinolate (MAR-N) or the like.
[0022] As aromatic ester oil, mention may be made of trimellitic
acid ester, trioctyl trimellitate (TOTM), tridecyl trimellitate,
tetraoctyl pyromellitate or the like.
[0023] As hindered ester oil, mention may be made of one obtained
by polyatomic alcohol and monobasic acid being suitably reacted
with each other. Monobasic acid to be reacted with polyatomic
alcohol may be single or plural. Further, it may be used as complex
ester which is oligoester of polyatomic alcohol and mixed aliphatic
acid of dibasic acid and monobasic acid.
[0024] As polyatomic alcohol, mention may be made of trimethylol
propane (TMP), pentaerythritol (PE), dipentaerythritol (DPE),
neopentyl glycol (NPG), 2-methyl-2-propyl-1,3-propane (MPPD) or the
like.
[0025] As monobasic acid, use is made chiefly of univalent
aliphatic acid of C.sub.4 to C.sub.18. Specifically, mention may be
made of acetic acid, valerianic acid, caproic acid, caprylic acid,
enanthic acid, pelargonic acid, capric acid, undecanic acid,
laurylic acid, mistiric acid, palmitic acid, beef fatty acid,
stearic acid, caproleic acid, undecylenic acid, linder acid, tudu
acid, fiseterinic acid, milistolenic acid, palmitoleic acid,
petroserine acid, oleic acid, elaiolic acid, asclepic acid,
vaccenic acid, sorbic acid, linoleic acid, linolenic acid, sabineic
acid, recinoleic acid, or the like.
[0026] As synthetic hydrocarbon oil, there is phenyl ether oil in
which (di)alkyl chain of C.sub.12 to C.sub.20 of disphenyl,
tripheyl and tetraphenyl was derived.
[0027] Taking lower evaporation and longer life into account, it is
preferable that ester oil be chosen from aromatic ester oil and
hindered ester oil and be used singly or mixedly. Particularly TOTM
is readily available and is excellent in a low evaporating
property, a lubricating property, etc. Also, (di)alkyl polyphenyl
ether oil is preferable as ether oil. Fluorophosphazene oil can
also be suitably used.
[0028] Also, by adding additives such as rust prevention agents,
oily agents and oxidation preventing agents mentioned below,
lubricating performance (fretting-resisting property or the like)
and durability can be enhanced.
[0029] (Rust Prevention Agent)
[0030] Organic sulfonic acid metal or ester is preferable as a rust
prevention agent. As organic sulfonic acid salt, use is made, for
example, of dinonyl naphthalene sulfonic acid and heavy alkyl
benzene sulfonic acid, and as the metal salt thereof, there is
calcium sulfonate, barium sulfonate, sodium sulfonate or the
like.
[0031] As ester, in sorbitan derivative, there is sorbitan
monolaurate, sorbitan tristearate, sorbitan monooleate, sorbitan
trioleate or the like as the partial ester of polybasic carboxylic
acid and polyatomic alcohol. As alkyl ester type, there is
polyoxyethylene laurate, polyoxyethylene oleate, polyoxyethylene
stearate or the like.
[0032] As these rust prevention agents, organic sulfonic acid metal
salt and ester can be used singly or as a mixture. Taking it into
account to improve the rust prevention property and suppress
fretting corrosion, ester polyoxyethylene sorbitan laurate is high
in dissolving property and is suitably used as sulfonic acid
metallic salt such as calcium sulfonate, and fluorophosphazene
oil.
[0033] (Oily Agent)
[0034] As an oily agent, the lubricating oil may preferably use
oleic acid, stearic acid or the like as higher fatty acid, lauryl
alcohol, oleyl alcohol or the like as higher alcohol, stearyl
amine, cetyl amine or the like as amine. These can be used singly
or mixedly.
[0035] (Oxidation Preventing Agent)
[0036] As an oxidation preventing agent, a nitrogen containing
compound oxidation preventing agent and a phenol oxidation
preventing agent may preferably be used singly or as a mixture.
[0037] As the nitrogen containing compound oxidation preventing
agent, there is phenyl a naphthylamine, diphenylamine, phenylene
diamine, oleyl amideamine, phenothiazine or the like.
[0038] As a phenol oxidation preventing agent, there is hindered
phenol such as p-t-butyl-phenyl salicylate, 2,6-di-t-butyl-p-phenyl
phenol, 2,2'-methylenebis-(4-methyl-6-t-octyl phenol),
4,4'-butyrydenbis-6-t-buty- l-m-cresol,
tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propio-
nate]methane,
1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxylbenzil)b-
enzene,
n-octadecyl-.beta.-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate,
2-n-octylthio-4,6-di(4'-hydroxy-3',5'-di-t-butyl)phenoxy-1,3,5-triazine,
4,4'-thiobisu-[6-t-butyl-m-cresol],
2-(2'-hydroxy-3'-t-butyl-5'-methylphe- nyl)-5-chlorobenzotriazole
or the like.
[0039] (Extreme Pressure Agent)
[0040] As an extreme pressure agent, use can be made of organic
metallic salt such as molybdenum thiocarbamate, molybdenum dithio
phosphate, zinc thiocarbamate, zinc dithiophosphate or the
like.
[0041] (Corrosion Preventing Agent)
[0042] As a corrosion preventing agent, mention may be made of
phosphoric acid ester, phosphorous acid ester or the like.
Particularly, molybdenum dithiocarbamate and phosphorous acid ester
exhibit an excellent fretting resisting property and may therefore
be preferred.
[0043] In addition to the foregoing agents, a friction preventing
agent, a viscosity index improving agent or the like may be
contained in the lubricating oil. These may all be conventional
agents.
[0044] Regarding the base oil and additive of the grease enclosed
in the above-described fretting-resisting roller bearing of the
present invention, use may be made of ones similar to the
above-described lubricating oil composition of the present
invention. Also, a thickness regulating agent may be a conventional
one such as metallic soap or urea resin, but from the viewpoint of
the characteristic of the bearing for a spindle, lithium soap
having an excellent characteristic in acoustic life is
preferable.
[0045] In the case of the fretting-resisting roller bearing of the
present invention, the contacting portions of the raceway surfaces
of the outer and inner races and the rolling elements are the same
material or different materials. Preferably, when different
materials are used, they are steel and ceramics or steel and a
super-hard alloy. If the lubricating oil in the present invention
is used, the fretting corrosion will be greatly mitigated, and
further, under an environment of severe vibration condition,
different materials may be small in the frictional force acting on
the contacting portions as compared with steel and steel, and in
these contacting portions, it is more difficult for such an injury
which will lead to fretting corrosion to occur.
[0046] In the case of ceramics, the material forming the rolling
elements may be silicon nitride, zirconia, alumina or the like, and
in the case of a super-hard alloy, the material forming the rolling
elements may be tungsten carbide or the like.
[0047] The friction characteristic on the contacting portions of
the raceways of the outer and inner races made of steel and the
rolling surfaces of the rolling elements made of ceramics or a
super-hard alloy is improved as compared with the friction
characteristic when steel and steel contact with each other.
[0048] Above all, the combination of bearing steel and silicon
nitride, stainless steel and silicon nitride, bearing steel and
zirconia, bearing steel and tungsten carbamate, or stainless steel
and tungsten carbamate provides an excellent friction
characteristic (a low friction characteristic) and is excellent in
the fretting resisting property. By combining these with the
above-mentioned lubricating oil, a further effect is obtained
against fretting corrosion and these combinations can be preferably
be used.
[0049] Description will now be made of the conditions and results
of evaluation tests carried out to confirm the effect of the
present invention.
1 [Bearing Outer Race Swing Test] Tested bearing: 695 Frequency: 27
Hz Angle of swing: 2.degree. Load (Fa): 14.7 N Frequency of swing:
1 .times. 10.sup.5 times Enclosed grease: Lithium soap grease
[0050] The above-mentioned swing test was carried out, and the
acceleration of the bearing in the radial direction thereof after
the test was measured and evaluation was effected.
[0051] A heretofore used bearing specification [Comparative Example
1] was subjected to a swing test, and comparison evaluation was
effected with the bearing radial direction acceleration signal
execution value after the test being 100%.
[0052] Because the traces of minute fretting corrosion created on
the inner and outer races and rolling elements of the bearing can
be measured with good sensitivity, the bearing radial direction
acceleration was used as a test evaluation item.
2 [Measurement of Rotation Torque] Tested bearing: 695 Load (Fa):
14.7 N Number of revolutions: 3600 rpm
[0053] As regards the magnitude of torque, 1.2 gf.multidot.cm or
less was regarded as being successful.
[0054] The test conditions of each embodiment and each comparative
example are as follows:
[0055] [Embodiment 1]
[0056] A bearing in which lubricating oil C of which the dynamic
viscosity at 40.degree. C. was 90 mm.sup.2/s was formed into film
on the raceway surfaces of inner and outer races, a cage and
rolling elements and grease was enclosed was tested in a pre-load
state under the above-mentioned conditions.
[0057] [Embodiment 2]
[0058] A bearing in which rolling elements were made of silicon
nitride and lubricating oil C of which the dynamic viscosity at
40.degree. C. was 90 mm.sup.2/s was formed into film on the raceway
surfaces of inner and outer races, a cage and rolling elements and
grease was enclosed was tested in a pre-load state under the
above-mentioned conditions.
[0059] [Embodiment 3]
[0060] A bearing in which rolling elements were made of tungsten
carbide of Vickers hardness 1300 and lubricating oil C of which the
dynamic viscosity at 40.degree. C. was 90 mm.sup.2/s was formed
into film on the raceway surfaces of inner and outer races, a cage
and rolling elements and grease was enclosed was tested in a
pre-load state under the above-mentioned conditions.
[0061] [Embodiment 4]
[0062] A bearing in which lubricating oil B of which the dynamic
viscosity at 40.degree. C. was 25 mm.sup.2/s was formed into film
on the raceway surfaces of inner and outer races, a cage and
rolling elements and grease was enclosed was tested in a pre-load
state under the above-mentioned conditions.
[0063] [Embodiment 5]
[0064] A bearing in which rolling elements were made of silicon
nitride and lubricating oil B of which the dynamic viscosity at
40.degree. C. was 25 mm.sup.2/s was formed into film on the raceway
surfaces of inner and outer races, a cage and rolling elements and
grease was enclosed was tested in a pre-load state under the
above-mentioned conditions.
[0065] [Embodiment 6]
[0066] A bearing in which rolling elements were made of tungsten
carbide of Vickers hardness 1300 and lubricating oil B of which the
dynamic viscosity at 40.degree. C. was 25 mm.sup.2/s was formed
into film on the raceway surfaces of inner and outer races, a cage
and rolling elements and grease was enclosed was tested in a
pre-load state under the above-mentioned conditions.
[0067] [Embodiment 7]
[0068] A bearing in which lubricating oil E of which the dynamic
viscosity at 40.degree. C. was 150 mm.sup.2/s was formed into film
on the raceway surfaces of inner and outer races, a cage and
rolling elements and grease was enclosed was tested in a pre-load
state under the above-mentioned conditions.
[0069] [Embodiment 8]
[0070] A bearing in which lubricating oil F of which the dynamic
viscosity at 40.degree. C. was 25 mm.sup.2/s was formed into film
on the raceway surfaces of inner and outer races, a cage and
rolling elements and grease was enclosed was tested in a pre-load
state under the above-mentioned conditions.
[0071] [Embodiment 9]
[0072] A bearing in which lubricating oil G of which the dynamic
viscosity at 40.degree. C. was 90 mm.sup.2/s was formed into film
on the raceway surfaces of inner and outer races, a cage and
rolling elements and grease was enclosed was tested in a pre-load
state under the above-mentioned conditions.
[0073] [Embodiment 10]
[0074] A bearing in which lubricating oil H of which the dynamic
viscosity at 40.degree. C. was 120 mm.sup.2/s was formed into film
on the raceway surfaces of inner and outer races, a cage and
rolling elements and grease was enclosed was tested in a pre-load
state under the above-mentioned conditions.
[0075] [Comparative Example 1]
[0076] A bearing in which lubricating oil A of which the dynamic
viscosity at 40.degree. C. was 11 mm.sup.2/s was formed into film
on the raceway surfaces of inner and outer races, a cage and
rolling elements and grease was enclosed was tested in a pre-load
state under the above-mentioned conditions.
[0077] [Comparative Example 2]
[0078] A bearing in which lubricating oil D of which the dynamic
viscosity at 40.degree. C. was 160 mm.sup.2/s was formed into film
on the raceway surfaces of inner and outer races, a cage and
rolling elements and grease was enclosed was tested in a pre-load
state under the above-mentioned conditions.
[0079] The compositions of the lubricating oils A to H used in the
above-described embodiments and comparative examples are shown in
Table 1 below.
3 TABLE 1 Lubricating Lubricating Lubricating Lubricating Oil A Oil
B Oil C Oil D kind of DOS PAO TOTM ADE oil dynamic 11 25 90 160
viscosity mm.sup.2/s (40.degree. C.) rust calcium calcium calcium
sodium prevention sulfonate sulfonate sulfonate sulfonate agent
additive -- zinc molybdenum phosphorous dithiophos- dithiophosphate
acid ester phate Lubricating Lubricating Lubricating Lubricating
Oil E Oil F Oil G Oil H kind of MO PET TOTM PAO oil dynamic
viscosity 150 25 90 120 mm.sup.2/s (40.degree. C.) rust sodium
calcium barium calcium prevention sulfonate sulfonate sulfonate
sulfonate agent additive phosphorous phosphorous zinc molybenum
acid acid ester dithiophosphate dithiophosphate DOS: dioctyl
sebacate, PAO: poly-.alpha.-olefin, TOTM: trioctyl trimellitate,
ADE: alkyl diphenyl ether MO: mineral oil
[0080] The acceleration signal execution values and rotation
torques in the above-described embodiments and comparative examples
are shown in the graphs of FIGS. 1 and 2, respectively.
[0081] According to the fretting-resisting roller bearing of the
present invention described above, there are obtained the following
effects:
[0082] (1) The oil film of lubricating oil having high dynamic
viscosity is formed on the raceway surfaces of the inner and outer
races, the cage and the rolling elements and therefore, there can
be provided a fretting-resisting roller bearing in which the
strength of the oil film is high, the fretting-resisting property
during conveyance is improved and the various characteristics of
the bearing are not adversely affected, and which further achieves
a higher temperature and a higher speed as well as a longer
life.
[0083] (2) When the material of the rolling elements is ceramics or
a super-hard alloy of Vickers hardness 1300 or greater and the
outer and inner races are made of steel and a material differing
from the material of the outer and inner races is used as the
material of the rolling elements, the hardness thereof is
increased, whereby not only fretting corrosion can be suppressed by
the prevention of the adhesion phenomenon between the members (the
raceway surfaces of the outer and inner races and the rolling
elements) and the decrease in the Hertzian contact area by the
difference in Young's modulus, but also the bearing functions well
even under the use conditions of high temperatures and high-speed
rotation.
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