U.S. patent application number 10/539375 was filed with the patent office on 2006-04-06 for grease compostion for automobile electrical equipment auxiliary device and prelubricated rolling using the grease composition.
Invention is credited to Katsuaki Denpou, Yasunobu Fujita, Shinya Nakatani, Hisao Sumiya.
Application Number | 20060073989 10/539375 |
Document ID | / |
Family ID | 32716352 |
Filed Date | 2006-04-06 |
United States Patent
Application |
20060073989 |
Kind Code |
A1 |
Fujita; Yasunobu ; et
al. |
April 6, 2006 |
Grease compostion for automobile electrical equipment auxiliary
device and prelubricated rolling using the grease composition
Abstract
To provide a grease composition for auxiliary machinery of
automobile electrical component containing an aromatic ester
oil-containing base oil having a specific diurea compound as a
thickener blended therewith and a rolling bearing having the
foregoing grease composition packed therein. The foregoing grease
composition and rolling bearing do not generate abnormal noises
even at an extremely low temperature of -40.degree. C., have
excellent seizure resistance even under a high temperature closed
to 180.degree. C., have excellent rust preventing performance, and
are suitable especially for electrical parts and auxiliary
machineries of engines, etc.
Inventors: |
Fujita; Yasunobu; (Kanagawa,
JP) ; Nakatani; Shinya; (Kanagawa, JP) ;
Denpou; Katsuaki; (Kanagawa, JP) ; Sumiya; Hisao;
(Kanagawa, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
32716352 |
Appl. No.: |
10/539375 |
Filed: |
January 5, 2004 |
PCT Filed: |
January 5, 2004 |
PCT NO: |
PCT/JP04/00006 |
371 Date: |
June 16, 2005 |
Current U.S.
Class: |
508/116 ;
508/481; 508/552 |
Current CPC
Class: |
C10M 2207/2855 20130101;
C10N 2040/14 20130101; C10M 169/02 20130101; B82Y 30/00 20130101;
C10M 2215/1026 20130101; C10N 2030/12 20130101; F16C 33/7879
20130101; C10N 2030/08 20130101; C10N 2040/02 20130101; F16C 19/184
20130101; C10N 2050/10 20130101 |
Class at
Publication: |
508/116 ;
508/481; 508/552 |
International
Class: |
C10M 115/08 20060101
C10M115/08; C10M 105/36 20060101 C10M105/36 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 6, 2003 |
JP |
2003-000363 |
Nov 4, 2003 |
JP |
2003-374317 |
Claims
1. A grease composition for auxiliary machinery of automobile
electrical component, which is characterized by containing a base
oil containing an aromatic ester oil in an amount of 30% by mass or
more based on the whole amount of the base oil and a diurea
compound, as a thickener, represented by the following general
formula in an amount of from 5 to 35% by mass based on the whole
amount of the grease composition: R8-NHCONH--R9-NHCONH--R10
(wherein R9 represents an aromatic hydrocarbon group having from 6
to 15 carbon atoms; and R8 and R10, which may be the same or
different, each represents an aliphatic hydrocarbon group, an
alicyclic hydrocarbon group, or a fused ring).
2. The grease composition for auxiliary machinery of automobile
electrical component according to claim 1, which is characterized
in that the aromatic ester oil is a trimellitic ester oil or a
pyromellitic ester oil.
3. The grease composition for auxiliary machinery of automobile
electrical component according to claim 2, which is characterized
in that in the trimellitic ester oil and the pyromellitic ester
oil, a hydrocarbon group to be derived is a hydrocarbon group
having from 6 to 10 carbon atoms.
4. The grease composition for auxiliary machinery of automobile
electrical component according to claim 1, which is characterized
by containing at least one member of carbon black and carbon nano
tube as a conductive powder.
5. The grease composition for auxiliary machinery of automobile
electrical component according to claim 1, which is characterized
by containing two or more members selected from rust preventives
made of a carboxylic acid or a carboxylate, ester based rust
preventives, and amine based rust preventives in an amount of from
0.2 to 10% by mass in total and from 0.1 to 9.9% by mass singly
based on the whole amount of the grease composition.
6. A rolling bearing, which is characterized by casing freely
rollingly plural rolling elements by a cage between an inner race
and an outer race and packing the grease composition for auxiliary
machinery of automobile electrical component according to claim 1
therein.
7. The rolling bearing according to claim 6, which is characterized
by containing a contact type rubber seal.
Description
TECHNICAL FIELD
[0001] The present invention relates to a grease composition which
is used especially under severe conditions of high temperature,
high speed, high load and vibration in automobile electrical parts
or auxiliary machineries of engines such as alternators,
intermediate pulleys, and electromagnetic clutches for car air
conditioners and further which is used for parts required to have
fluidity at an extremely low temperature of -40.degree. C., and to
a rolling bearing having the foregoing grease composition packed
therein.
BACKGROUND ART
[0002] In automobiles, by the spread of FF (front engine front
drive) vehicles aiming at miniaturization and lightening and the
demands of enlargement of an accommodation space, a reduction of
the engine room space is unavoidable, miniaturization and
lightening of the above-enumerated electrical parts and auxiliary
machineries of engines are further being advanced, and respective
parts to be integrated thereinto are required to have high
performance and realize a high output more and more. However, a
lowering of the output due to the miniaturization is inevitable.
For example, in alternators and electromagnetic clutches for car
air conditioners, the lowering of the output is compensated by
accelerating the speed, and following this, intermediate pulleys
are actuated at a high speed. Further, by the demand for improving
silence properties, since closing of an engine room is advancing
and an increase of the temperature within the engine room is
promoted, it has become necessary that these parts endure high
temperatures.
[0003] For the sake of improving the seizure life at a high
temperature, there have hitherto been made various proposals. For
example, as described in JP-B-7-45677 and Japanese Patent Nos.
3,290,010 and 3,330,755, greases made of a trimellitic ester
oil-containing base oil having a urea compound as a thickener
blended therein are widely used. Also, in rolling bearings to be
used for these applications, there is also required a
countermeasure against a flaking phenomenon accompanied with a
structural change of the transfer surface. For example,
JP-A-2002-195277 and JP-A-2003-13973 propose a method for adding a
metal passive agent such as nitrous acid.
[0004] Automobiles are used in various countries and states of the
world, the use environment thereof is diverse, and required
characteristics are diverse corresponding thereto. For example, in
the cold district, a requirement for the non-generation of abnormal
noises caused due to a shortage of fluidity of a lubricant at the
time of start-up of engine is high; and in the tropical rain forest
district and the district closed to the sea, since the humidity and
salinity in the air are high, a requirement for rust preventing
properties is high.
[0005] However, greases which can fully meet these diverse
requirements inclusive of the above-enumerated greases have not
been obtained yet. Then, an object of the invention is to provide a
grease composition and a rolling bearing which do not generate
abnormal noises even at an extremely low temperature of -40.degree.
C., have excellent seizure resistance even under a high temperature
closed to 180.degree. C., have excellent flaking resistance and
rust preventing performance, and are suitable especially for the
foregoing electrical parts and auxiliary machineries of engines,
etc.
DISCLOSURE OF THE INVENTION
[0006] In order to solve the foregoing problems, the present
inventors made extensive and intensive investigations. As a result,
it has been found that among diurea compounds, those having an
alicyclic hydrocarbon group, when combined with a base oil
containing an aromatic ester oil, exhibit an excellent lubricating
performance over a wide temperature range of from an extremely low
temperature to a high temperature, do not generate abnormal noises
at a low temperature, and can improve greatly a seizure performance
of a bearing, leading to accomplishment of the invention.
[0007] Specifically, the invention provides a grease composition
for auxiliary machinery of automobile electrical component, which
is characterized by containing a base oil containing an aromatic
ester oil in an amount of 30% by mass or more based on the whole
amount of the base oil and a diurea compound, as a thickener,
represented by the following general formula in an amount of from 5
to 35% by mass based on the whole amount of the grease composition.
R8-NHCONH--R9-NHCONH--R10 (In the formula, R9 represents an
aromatic hydrocarbon group having from 6 to 15 carbon atoms; and R8
and R10, which may be the same or different, each represents an
aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or a
fused ring).
[0008] Also, the invention provides the foregoing grease
composition for auxiliary machinery of automobile electrical
component, which is characterized by containing at least one member
of carbon black and carbon nano tube as a conductive powder for the
purpose of imparting conductivity. Further, it is preferable that
two or more members selected from rust preventives made of a
carboxylic acid or a carboxylate, ester based rust preventives, and
amine based rust preventives are contained as a rust preventive in
an amount of from 0.2 to 10% by mass in total and from 0.1 to 9.9%
by mass singly based on the whole amount of the grease composition,
whereby sufficient rust preventing properties are imparted. Also,
such rust preventives are free from adverse influences against the
environment.
[0009] Also, the invention provides a rolling bearing, which is
characterized by casing freely rollingly plural rolling elements by
a cage between an inner race and an outer race and packing the
foregoing grease composition for auxiliary machinery of automobile
electrical component therein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a cross-sectional view to show a double row
angular ball bearing as one embodiment of the rolling bearing of
the invention;
[0011] FIG. 2 is a graph to show the results of Verification-I of
the content of an aromatic ester oil;
[0012] FIG. 3 is a graph to show the results of Verification-I of
the blending amount of a thickener;
[0013] FIG. 4 is a graph to show Relationship-I between a pour
point of a base oil and the generation of abnormal noises at a low
temperature;
[0014] FIG. 5 is a graph to show the results of Verification-II of
the content of an aromatic ester oil;
[0015] FIG. 6 is a graph to show the results of Verification-II of
the blending amount of a thickener;
[0016] FIG. 7 is a graph to show Relationship-II between a pour
point of a base oil and the generation of abnormal noises at a low
temperature;
[0017] FIG. 8 is a graph to show the relationship between the
addition amount of carbon black and the generation probability of
flaking; and
[0018] FIG. 9 is a graph to show the relationship between the
particle size of carbon black and the anderon value.
[0019] Also, in the drawings, symbol 10 stands for a double row
angular ball bearing; 15 stands for an outer race; 16 stands for an
inner race; 17 stands for an outer raceway; 18 stands for an inner
raceway; and 19 stands for a rolling element (ball).
BEST MODE FOR CARRYING OUT THE INVENTION
[0020] The grease composition for auxiliary machinery of automobile
electrical component (hereinafter simply referred to as "grease
composition") and the rolling bearing of the invention will be
hereunder described in detail.
Grease Composition
[Base Oil]
[0021] In the grease composition of the invention, the base oil
contains an aromatic ester oil. Of aromatic ester oils, trimellitic
ester oils represented by the following formula (I) are preferable.
##STR1##
[0022] In the formula (I), R1, R2, and R3, which may be the same or
different, each represents a saturated or unsaturated linear or
branched hydrocarbon group. Also, those having from 6 to 10 carbon
atoms are preferable.
[0023] Also, as the aromatic ester oil, pyromellitic ester oils
represented by the following formulae (II) and (III) are
preferable. ##STR2##
[0024] In the formula (II) and formula (III), R4, R5, R6, and R7,
which may be the same or different, each represents a saturated or
unsaturated linear or branched hydrocarbon group. Also, those
having from 6 to 10 carbon atoms are preferable.
[0025] There have hitherto been known polyphenyl ether oils,
silicone oils, fluorocarbon oils, and the like as a lubricant
having excellent heat resistance. However, all of these lubricants
are very expensive and involve such a problem that silicone oils
and fluorocarbon oils are generally inferior in lubricity. In
contrast, the foregoing aromatic ester oils are relatively cheap
and have such an advantage that they are excellent in heat
resistance, oxidation resistance, abrasion resistance, and the
like. In particular, since the trimellitic ester oils and
pyromellitic ester oils represented by the formulae (I) to (III)
and containing a hydrocarbon group having from 6 to 10 carbon atoms
have a low pour point and a high viscosity index, they are suitable
for auxiliary machineries of automobile electrical components which
are required to have a wide use temperature of from an extremely
low temperature to a high temperature. Especially, the trimellitic
ester oils have a low pour point and are preferable.
[0026] Such trimellitic ester oils and pyromellitic ester oils
containing a hydrocarbon group having from 6 to 10 carbon atoms are
available in the market; examples of the trimellitic ester oils
include "TRIMEX T-08" and "TRIMEX N-08", all of which are
manufactured by Kao Corporation, "ADEKA PROVER T-45", "ADEKA PROVER
T-90" and "ADEKA PROVER PT-50", all of which are manufactured by
Asahi Denka Co., Ltd., and "EMKARATE 8130" and "EMKARATE 9130", all
of which are manufactured by UNIQEMA; and examples of the
pyromellitic ester oils include "ADEKA PROVER LX-1891" and "ADEKA
PROVER LX-1892", all of which are manufactured by Asahi Denka Co.,
Ltd.
[0027] The content of the foregoing aromatic ester oil is
preferably 30% by mass or more based on the whole amount of the
base oil. When the content of the aromatic ester oil is less than
30% by mass, seizure is likely caused at a high temperature, and
the abrasion resistance is not thoroughly revealed. Examples of a
lubricant which can be used jointly include mineral oils,
fluorocarbon oils, silicone oils, synthetic hydrocarbon oils, ether
oils, ester oils other than aromatic ester oils, and glycol oils.
Of these, those which have a low pour point and which are excellent
in heat resistance, oxidation resistance, etc. are preferable, and
synthetic hydrocarbon oils, ether oils, and ester oils are
suitable. Specifically, examples of the synthetic hydrocarbon oils
include poly-.alpha.-olefin oils; examples of the ether based oils
include alkyl diphenyl ethers and alkyl triphenyl ethers; and
examples of the ester oils include diester oils, neopentyl type
polyol ester oils, and complex ester oils thereof. They may be used
singly or can be properly combined and used. Above all, taking into
consideration not only low pitch sound fluidity while taking into
account the generation of abnormal noises at an extremely low
temperature but also improvements in the lubricating performance
and seizure life under severe conditions of high temperature, high
speed, high load and vibration, a combined use with a polyol ester
oil such as pentaerythritol ester oils, a poly-.alpha.-olefin oil,
or an alkyl diphenyl ether oil is preferable.
[0028] Also, a kinematic viscosity at 40.degree. C. of the base oil
is preferably from 30 to 150 mm.sup.2/s, and taking into
consideration of the low-temperature fluidity, it is more
preferably from 40 to 130 mm.sup.2/s. It is most preferably from 40
to 100 mm.sup.2/s.
[Thickener]
[0029] The foregoing base oil is blended with a diurea compound
represented by the following formula (IV) as a thickener.
R8-NHCONH--R9-HNCOHN--R10 (IV)
[0030] In the formula (IV), R9 represents an aromatic hydrocarbon
group having from 6 to 15 carbon atoms; and R8 and R10, which may
be the same or different, each represents a hydrocarbon group or a
fused ring hydrocarbon group. Also, in R8 and R10, the hydrocarbon
group may be any of an aliphatic hydrocarbon group or an aromatic
hydrocarbon group; and the fused ring hydrocarbon group preferably
has from 9 to 19 carbon atoms. It is preferable that R8 and R10
each contains at least an alicyclic hydrocarbon group or an
aliphatic hydrocarbon group. A diurea compound containing an
alicyclic hydrocarbon group has such properties that it has
excellent heat resistance as compared with a diurea compound
containing an aliphatic hydrocarbon group. The diurea compound
containing an aliphatic hydrocarbon group has such an advantage
that when used as a thickener of grease, it is excellent in
fluidity of the grease as compared with the diurea compound
containing an alicyclic hydrocarbon group. Also, the diurea
compound containing an alicyclic hydrocarbon group or an aliphatic
hydrocarbon group has a large surface area per unit volume and a
high thickening effect as compared with a diurea compound
containing an aromatic hydrocarbon group due to a difference of the
fibrous shape thereof. For that reason, when compared in terms of
the same penetration, the diurea compound containing an aliphatic
hydrocarbon group or an alicyclic hydrocarbon group may be made
small in the use amount as compared with the diurea compound
containing an aromatic hydrocarbon group so that the proportion of
the base oil can be increased in proportion thereto and that the
seizure resistance can be improved.
[0031] The diurea compound represented by the foregoing formula
(IV) is obtained by reacting 2 moles in total of a monoamine
containing R8 or R10 in the skeleton thereof with one mole of a
diisocyanate containing R9 in the skeleton thereof in a base
oil.
[0032] Examples of the diisocyanate containing R9 in the skeleton
thereof which can be suitably used include diphenylmethane
diisocyanate, tolylene diisocyanate, xylylene diisocyanate,
biphenylene diisocyanate, dimethyldiphenylene diisocyanate, and
alkyl substitution compounds thereof.
[0033] Examples of the monoamine containing a hydrocarbon group as
R8 or R10 in the skeleton thereof which can be suitably used
include aniline, cyclohexylamine, octylamine, toluidine,
dodecylaniline, octadecylamine, hexylamine, heptylamine,
nonylamine, ethylhexylamine, decylamine, undecylamine,
dodecylamine, tetradecylamine, pentadecylamine, nonadecylamine,
eicodecylamine, oleylamine, linolenoylamine, linolenylamine,
methylcyclohexylamine, ethylcyclohexylamine,
dimethylcyclohexylamine, diethylcyclohexylamine,
butylcyclohexylamine, propylcyclohexylamine, amylcyclohexylamine,
cyclooctylamine, benzylamine, benzhydrylamine, phenethylamine,
methylbenzylamine, biphenylamine, phenylisopropylamine, and
phenylhexylamine.
[0034] Also, examples of the monoamine containing a fused ring
hydrocarbon group as R8 or R10 include indene based amine compounds
such as aminoindene, amineindane, and amino-1-methyleneindene;
naphthalene based amine compounds such as aminonaphthalene
(naphthylamine), aminomethylnaphthalene, aminoethylnaphthalene,
aminodimethylnaphthalene, aminocadalene, aminovinylnaphthalene,
aminophenylnaphthalene, aminobenzylnaphthalene,
aminodinaphthylamine, aminobinaphthyl,
amino-1,2-dihydronaphthalene, amino-1,4-dihydronaphthalene,
aminotetrahydronaphthalene, and aminooctalin; fused dicyclic amine
compounds such as aminopentalene, aminoazulene, and aminoheptalene;
aminofluorene based amine compounds such as aminofluorene and
amino-9-phenylfluorene; anthracene based amine compounds such as
aminoanthracene, aminomethylanthracene, aminodimethylanthracene,
aminophenylanthracene, and amino-9,10-dihydroanthracene;
phenanthrene based amine compound such as aminophenanthrecene,
amino-1,7-dimethylphenanthrecene, and amninoretene; fused tricyclic
amine compounds such as aminobiphenylene, amino-s-indacene,
amino-as-indacene, aminoacenaphthylene, aminoacenaphthene, and
amiophenalene; fused tetracyclic amine compounds such as
aminonaphthacene, aminochrysene, aminopyrene, aminotriphenylene,
aminobenzanthracene, aminoaceanthrylene, aminoaceanthrene,
aminoacephenanthrylene, aminoacephenanthrene, aminofluoranthene,
and aminopleiadene; fused pentacyclic amine compounds such as
aminopentacene, aminopentaphene, aminopicene, aminoperylene,
aminodibenzanthracene, aminobenzopyrene, and aminocholanthrene; and
fused polycyclic (hexacyclic or polycyclic) amine compounds such as
aminocoronene, aminopyranthrene, aminoviolanthrene,
aminoisoviolanthrene, and aminoovalene.
[0035] The diurea compound represented by the foregoing formula
(IV) may be used singly or in admixture and is blended in an amount
of from 5 to 35% by mass base on the whole amount of the grease
composition. When the blending amount is less than 5% by mass, it
is difficult to keep the grease state, whereas when it exceeds 35%
by mass, the grease is excessively hardened so that the lubricating
effect cannot be sufficiently revealed. Taking into consideration
endurance under further high temperature, high speed, high load and
high vibration conditions, in view of grease softening by high
temperature and high shearing and lubricating effect, it is
preferable that the blending amount is from 10 to 30% by mass.
[0036] A worked penetration of the grease composition is preferably
from 220 to 340. In order to make the worked penetration fall
within this range by the blending amount of the diurea compound
represented by the foregoing formula (IV), it is desired that a
molar ratio of the alicyclic hydrocarbon group or aliphatic
hydrocarbon group is 20% by mole or more of the total sum of the
aliphatic hydrocarbon group or aliphatic hydrocarbon group and the
aromatic hydrocarbon group with the whole amount being defined as
100.
[Conductive Powder]
[0037] For the purposes of eliminating a potential difference
between the inner and outer races of bearing and preventing a
flaking phenomenon from occurring, it is preferred to add a
conductive powder. The conductive powder is not particularly
limited. However, taking into consideration the matters that
conductivity can be kept to a high temperature and that lubricity
of the grease is not deteriorated, carbon based powders such as
carbon black and carbon nano tube can be suitably used. The carbon
black preferably has a mean particle size of not more than 5 .mu.m,
and more preferably not more than 2 .mu.m. Most preferably, those
having a mean particle size of from 10 to 300 nm are used. Such
carbon black is available in the market, and examples thereof
include KETJEN BLACK EC and KETJEN BLACK EC600JD, all of which are
manufactured by Lion Akzo Co., Ltd. As the carbon nano tube, not
only fullerenes of C60 and C70 but also those having a diameter of
not more than 15 nm and a length of not more than 5 .mu.m can be
suitably used. Preferably, those having a diameter of not more than
10 nm and a length of not more than 2 .mu.m are used. Such carbon
nano tube is available in the market, and examples thereof include
carbon nano fiber VGCF manufactured by Showa Denko K.K.
[0038] An addition amount of such a conductive powder in the grease
composition is preferably from 0.5 to 5% by mass based on the whole
amount of the grease composition. When the addition amount is not
more than 0.5% by mass, the addition effect is not obtained,
whereas when it exceeds 5% by mass, the fluidity of the grease is
influenced. Also, when the foregoing mean particle size or length
exceeds 2 .mu.m, there is some possibility that the acoustic
performance of the bearing is influenced.
[Rust Preventive]
[0039] In the bearing for auxiliary machineries of automobile
electrical components which is the application of the invention,
high rust preventing properties are required, and therefore, it is
preferred to add a rust preventive. Of rust preventives, rust
preventives made of a carboxylic acid or a carboxylate, ester based
rust preventives, and amine based rust preventives, all of which
are low in a load against the environment, are preferable. In order
to reveal sufficiently the rust preventing performance, these rust
preventives are used in admixture of two or more kinds thereof, and
the content thereof is from 0.2 to 10% by mass in total and from
0.1 to 9.9% by mass singly based on the whole amount of the grease
composition. When the amount of the base oil is increased, the
seizure resistance is improved. Accordingly, the amount of the rust
preventives is preferably from 0.2 to 6% by mass in total and from
0.1 to 5.9% by mass singly.
[0040] Though the rust preventives made of a carboxylic acid or a
carboxylate, the ester based rust preventives, and the amine based
rust preventives are not particularly limited, preferred examples
thereof are given below. Examples of the carboxylic acid or
carboxylate include monocarboxylic acids such as stearic acid,
dicarboxylic acids such as alkyl- or alkenylsuccinic acids and
derivatives thereof, and metal (for example, calcium, barium,
magnesium, aluminum, zinc, and lead) salts of naphthenic acid,
abietic acid, a lanolin fatty acid, or an alkenylsuccininc acid. Of
these, alkenylsuccinic acids and zinc naphthenate are suitable.
Examples of the ester based rust preventives include sorbitan
monooleate, sorbitan trioleate, pentaerythritol monooleate, and
carboxylic acid partial esters of a polyhydric alcohol such as
succinic half esters. Of these, sorbitan monooleate and succinic
half esters are suitable. As the amine based rust preventives,
alkoxyphenylamines, partial amides of a dibasic carboxylic acid,
and the like are suitable.
[Other Additives]
[0041] For the purpose of further enhancing the performance of the
grease composition, other additives can be added as the need
arises. Examples of other additives include antioxidants such as
amine bases, phenol bases, sulfur bases, zinc dithiophosphate, and
zinc dithiocarbamate; extreme pressure agents such as phosphorus
bases, zinc dithiophosphate, and organomolybdenum; oiliness agents
such as fatty acids and animal and vegetable oils; and metal
deactivators such as benzotriazles. These can be added singly or in
combinations of two or more kinds thereof. An addition amount of
such additives is not particularly limited and properly set up so
far as the prescribed object of the invention can be achieved.
Rolling Bearing
[0042] Also, the invention relates to a rolling bearing having the
foregoing grease composition packed therein. Though the rolling
bearing is not limited with respect to the kind, construction and
structure, for example, a double row angular ball bearing 10
illustrated in FIG. 1 can be enumerated. In the illustrated double
row angular ball bearing 10, plural rolling elements (balls) 19, 19
are provided freely rollingly between double row outer raceways 17,
17 provided on the inner peripheral surface of an outer race 15 and
inner raceways 18, 18 provided on the respective outer peripheral
surfaces of inner races 16, 16, thereby making relative rotation
between the outer race 15 and the inner races 16, 16 free. Also, an
opening between the outer race 15 and the inner races 18, 18 is
sealed by a sealing unit 1. This sealing unit 1 is one comprising a
metallic slinger 2 having a sealing material 3 made of an elastic
material integrally molded therewith. The slinger 2 is constructed
of a first member having an approximately L-shape cross-section and
having an annular form as a whole, which is provided with an outer
diameter side cylindrical portion 5 which can be freely internally
fitted and fixed to the end part inner peripheral surface of the
outer race 15 and an inside circular ring portion 6 which is folded
internally in the diameter direction from the inner end edge in the
axis direction of the outer diameter side cylindrical portion 5;
and a second member having an L-shape cross-section and having an
annular form as a whole, which is provided with an inner diameter
side cylindrical portion 8 which can be freely externally fitted
and fixed to the outer end part outer peripheral surface of the
inner race 16 and an outside circular ring portion 9 which is
folded externally in the diameter direction from the outer end edge
in the axis direction of this inner diameter side cylindrical
portion 8. The sealing material 3 is provided with three outer,
intermediate and inner seal lips 3a, 3b, 3c; a tip edge of the
outer seal lip 3a positioned in the outermost side is brought into
slidable contact with the inner surface of an outer circular ring
portion 9 constituting the slinger 2 along the entire periphery;
and tip edges of the intermediate seal lip 3b and inner seal lip
3c, the both of which are the remaining two seal lips, are brought
into slidable contact with the outer peripheral surface of the
inner diameter side cylindrical portion 8 constituting the slinger
2 along the entire periphery, thereby revealing a high sealing
performance.
[0043] The foregoing grease composition is packed in a space formed
by the outer race 15, the inner races 16, 16, the ball 19, and the
sealing unit 1. Though a packing amount is not limited, it is
preferable that the prelubricating amount accounts for from 25 to
45% by volume of the foregoing space.
[0044] Since the foregoing grease composition is packed, the
rolling bearing of the invention is well actuated even under severe
conditions of high temperature, high speed, high load and
vibration. Further, it does not generate abnormal noises even at an
extremely low temperature of -40.degree. C. and therefore, is
suitable for auxiliary machinery of automobile electrical
component.
EXAMPLES
[0045] The invention will be further described below with reference
to the following Examples and Comparative Examples, but it should
be construed that the invention is not limited thereto in any
way.
Examples 1 to 8 and Comparative Examples 1 to 2
(Preparation of Test Grease)
[0046] Each of test greases was prepared at a blending shown in
Table 1. During this, a half amount of a base oil was charged in a
first vessel, into which was then thrown and dissolved
cyclohexylamine. Furthermore, a half amount of a base oil was
charged in a second vessel, into which was then thrown and
dissolved diphenylmethane-4,4-diisocyanate. Then, the contents of
the first vessel were added in the second vessel and reacted with
stirring upon heating at about 70.degree. C. Thereafter, the
temperature was increased to 160.degree. C., thereby stopping the
reaction. After cooling, a rust preventive and an antioxidant were
added, and the mixture was passed through a roll mill and
deaerated, thereby obtaining a test grease. Incidentally, a
blending amount of the rust preventive was 2% by mass in total, and
the kind and blending amount of the antioxidant were made
common.
[0047] Using each of the thus prepared test greases, the following
(1) seizure test-I, (2) low-temperature abnormal noise test-I, (3)
high-temperature penetration change test and (4) rust preventing
test were carried out. The results are also shown in Table 1.
(1) Seizure Test-I:
[0048] 1 g of the test grease was packed in a contact rubber
seal-provided double row angular ball bearing having an inner
diameter of .phi.35 mm, an outer diameter of .phi.52 mm, and a
width of 20 mm (see FIG. 1), thereby preparing a test bearing.
Then, the test bearing was subjected to continuous rotation under
conditions at an outer race rotation speed of 10,000 min.sup.-1, a
bearing temperature of 170.degree. C. and a radial load of 1,960 N,
and when the bearing outer race temperature was increased by
15.degree. C., it was considered that seizure occurred, and the
test was stopped. The results were shown in terms of a relative
value with the seizing life of Comparative Example 3 being defined
as 1.
(2) Low-Temperature Abnormal Noise Test-I:
[0049] 3.5 g of the test grease was packed in a contact rubber
seal-provided single row deep groove ball bearing having an inner
diameter of .phi.25 mm, an outer diameter of .phi.62 mm, and a
width of 17 mm, thereby preparing a test bearing. Then, an
operation of rotating the inner race at a rotation speed of 1,800
min.sup.-1 for 5 seconds and then at 3,600 min.sup.-1 for 5 seconds
under conditions at -30.degree. C. and an axial load of 980 N was
performed 5 times, thereby confirming the presence or absence of
the generation of abnormal noises. The case where abnormal noises
were generated was defined to be dissatisfactory.
(3) High-Temperature Penetration Change Test;
[0050] The test grease was coated in the state of a film having a
thickness of 3 mm on an iron plate and then allowed to stand under
the atmosphere at 170.degree. C. for 240 hours. After standing, a
worked penetration was measured and compared with the worked
penetration before standing. The case where a change of the worked
penetration exceeded .+-.100 was defined to be dissatisfactory.
(4) Rust Preventing Test:
[0051] 2.7 g of the test grease was packed in a single row deep
groove ball bearing having an inner diameter of .phi.17 mm, an
outer diameter of .phi.47 mm, and a width of 14 mm, 0.3 mL of a
0.1% sodium chloride aqueous solution was further poured into the
bearing, and a non-contact seal was fitted, thereby preparing a
test bearing. The test bearing was rotated so as spread the test
grease and the sodium chloride aqueous solution all over the inside
of the bearing and then allowed to stand under the environment at
60.degree. C. and 70% RH for 3 days. After standing, the test
bearing was broken up, and the inner raceway surface was observed,
thereby confirming the presence or absence of the generation of
rust. The case where rust was generated was defined to be
dissatisfactory. TABLE-US-00001 TABLE 1 Grease blending and test
results Example 1 Example 2 Example 3 Example 4 Example 5 Thickener
Diurea Diurea Diurea Diurea Diurea (aromatic + (alicyclic +
(alicyclic) (aromatic + alicyclic) (alicyclic) alicyclic)
aliphatic) Amount of 15 13 18 16 20 thickener % by mass
Construction of PE TE TE TE TE base oil (100) (100) (100) (100)
(100) Hydrocarbon C8 C7 to C9 C8 C8, C10 C7 to C9 group of n-Octyl
Mixed 2-Ethylhexyl n-Octyl, Decyl Mixed aromatic ester Rust
preventive (Sorbitan (Calcium (Zinc (Succinic half (Sorbitan
trioleate) + naphthenate) + naphthenate) + ester) + (Sorbitan
monooleate) + (zinc (Alkenylsuccinic (Succinic half (Succinic half
monooleate) naphthenate) acid) ester) ester) + (Sorbitan
monooleate) Kinematic 83 53 90 48 70 viscosity of base oil
mm.sup.2/s @40.degree. C. Worked No. 2 No. 2 to No. 1 No. 1 No. 2
No. 3 penetration Pour point of -38 -45 -40 -46 -48 base oil
.degree. C. High- Satisfactory Satisfactory Satisfactory
Satisfactory Satisfactory temperature penetration change
Low-temperature Satisfactory Satisfactory Satisfactory Satisfactory
Satisfactory abnormal noise test-I Seizure test-I 11 10 14 7 12
Rust preventing Satisfactory Satisfactory Satisfactory Satisfactory
Satisfactory test Comparative Comparative Example 6 Example 7
Example 8 Example 1 Example 2 Thickener Diurea Diurea Diurea
Triurea Diurea (alicyclic) (aromatic + aliphatic) (aliphatic)
(aromatic) (aromatic) Amount of 18 22 12 24 23 thickener % by mass
Construction of TE + ADE TE + PET TE TE MO base oil (30:70) (50:50)
(100) (100) (100) Hydrocarbon C7 to C9 C10 C12 C8, C10 group of
Mixed Decyl Dodecyl n-Octyl, Decyl aromatic ester Rust preventive
(Sorbitan (Stearic acid) + (Zinc Succinic half Sorbitan monooleate)
+ (Zinc (Sorbitan naphthenate) + ester trioleate naphthenate)
monooleate) (Alkenylsuccinic anhydride) Kinematic 80 60 130 48 97
viscosity of base oil mm.sup.2/s @40.degree. C. Worked No. 1 No. 3
to No. 2 No. 2 No. 2 No. 2 penetration Pour point of -40 -35 -25
-46 -25 base oil .degree. C. High- Satisfactory Satisfactory
Satisfactory Dissatisfactory Dissatisfactory temperature
penetration change Low-temperature Satisfactory Satisfactory
Dissatisfactory Satisfactory Dissatisfactory abnormal noise test-I
Seizure test-I 9 7 10 4 1 Rust preventing Satisfactory Satisfactory
Satisfactory Dissatisfactory Dissatisfactory test TE: Trimellitic
ester PE: Pyromellitic ester PET: Pentaerythritol ester (30
mm.sup.2/s @40.degree. C.) ADE: Dialkyl diphenyl ether (100
mm.sup.2/s @40.degree. C.) MO: Mineral oil (97 mm.sup.2/s
@40.degree. C.)
[0052] As shown in Table 1, the test greases of the Examples
containing an aromatic ester oil-containing base oil and a diurea
compound represented by the general formula (IV) as a thickener
according to the invention are less in a change of the worked
penetration at a high temperature and excellent in high-temperature
endurance. Also, by packing each of the test greases of the
Examples, the seizure life of bearing can be improved, the
generation of abnormal noises at a low temperature can be
suppressed, and further, the rust preventing properties are
improved. However, as in Example 8, even by using an aromatic ester
oil-containing base oil and using a diurea compound containing an
aliphatic hydrocarbon group as a thickener, when the viscosity of
the base oil is high, abnormal noises are generated at a low
temperature. Also, as in Comparative Example 1, even by using an
aromatic ester oil-containing base oil, when a triurea compound
containing an aromatic hydrocarbon group is used as a thickener,
the high-temperature endurance is deteriorated, and further, since
the rust preventive is a succinic half ester singly, the rust
preventing performance is lowered.
(Verification-I of the Content of Aromatic Ester Oil)
[0053] Test greases were prepared according to the blending of the
test grease of Example 7, except for using a base oil wherein the
blending ratio of the trimellitic ester oil to the pentaerythritol
ester oil was changed. Then, the foregoing (1) seizure test-I was
carried out using these test greases.
[0054] The relationship between the content of the trimellitic
ester oil and the seizure life is shown as a graph in FIG. 2.
Incidentally, the seizure life is shown in terms of a relative
value against the case of single use of the pentaerythritol ester
oil (100%). As shown in the drawing, it is noted that when the
trimellitic ester oil is contained in an amount of 30% by mass or
more, the seizure life becomes especially good.
(Verification-I of the Blending Amount of Thickener)
[0055] Test greases were prepared according the blending of the
test grease of Example 5, except for changing the blending amount
of the thickener. Then, the foregoing (1) seizure test-I was
carried out using these test greases.
[0056] The relationship between the blending amount of the
thickener and the seizure life is shown as a graph in FIG. 3.
Incidentally, the seizure life is shown in terms of a relative
value against Comparative Example 3. As shown in the drawing, it is
noted that when the thickener is blended in an amount of from 5 to
35% by mass, especially from 10 to 30% by mass, the seizure life
becomes good.
(Relationship-I Between Pour Point of Base Oil and the Generation
of Abnormal Noises at Low Temperature)
[0057] Base oils having a different pour point were prepared using
a pentaerythritol ester having a pour point of -55.degree. C. and a
pyromellitic ester having a pour point of -20.degree. C., and a
diurea compound containing an alicyclic hydrocarbon group was
blended with each of the base oils, thereby preparing test greases.
Incidentally, the blending amount of the diurea compound was made
constant, and the worked penetration was adjusted at No. 2. Then,
the foregoing (2) low-temperature abnormal noise test-I was carried
out using these test greases.
[0058] The relationship between the pour point of the base oil and
the generation of abnormal noises is shown in FIG. 4. It is noted
that when the pour point of the base oil is not higher than
-30.degree. C., abnormal noises are not generated.
Examples 9 to 15 and Comparative Examples 3 to 5
(Preparation of Test Grease)
[0059] Each of test greases was prepared at a blending shown in
Table 2. During this, a half amount of a base oil was charged in a
first vessel, into which was then thrown and dissolved
cyclohexylamine. Furthermore, a half amount of a base oil was
charged in a second vessel, into which was then thrown and
dissolved diphenylmethane-4,4-diisocyanate. Then, the contents of
the first vessel were added in the second vessel and reacted with
stirring upon heating at about 70.degree. C. Thereafter, the
temperature was increased to 160.degree. C., thereby stopping the
reaction. After cooling, a rust preventive, an antioxidant and
carbon black were added, and the mixture was passed through a roll
mill and deaerated, thereby obtaining a test grease. Incidentally,
the kind and blending amount of the antioxidant were made
common.
[0060] Using each of the thus prepared test greases, the following
(1) seizure test-II, (2) low-temperature abnormal noise test-I and
(5) flaking resistance test were carried out. Also, the (3)
high-temperature penetration change test and the (4) rust
preventing test were carried out in the same manners as described
above. The results are also shown in Table 2.
(1) Seizure Test-II:
[0061] 1 g of the test grease was packed in a contact rubber
seal-provided double row angular ball bearing having an inner
diameter of .phi.35 mm, an outer diameter of .phi.52 mm, and a
width of 20 mm (see FIG. 1), thereby preparing a test bearing.
Then, the test bearing was subjected to continuous rotation under
conditions at an outer race rotation speed of 13,000 min.sup.-1, a
bearing temperature of 130.degree. C. and a radial load of 1,560 N,
and when the bearing outer race temperature was increased by
15.degree. C., it was considered that seizure occurred, and the
test was stopped. The case where the time for reaching the seizure
was 1,000 hours or more was defined to be satisfactory.
(2) Low-Temperature Abnormal Noise Test-II:
[0062] 3.5 g of the test grease was packed in a contact rubber
seal-provided single row deep groove ball bearing having an inner
diameter of .phi.25 mm, an outer diameter of .phi.62 mm, and a
width of 17 mm, thereby preparing a test bearing. Then, the inner
race was rotated at 2,600 min.sup.-1 for 30 seconds under
conditions at -30.degree. C. and an axial load of 9,800 N, thereby
confirming the presence or absence of the generation of abnormal
noises. The case where abnormal noises were generated was defined
to be dissatisfactory.
(5) Flaking Resistance Test:
[0063] 2.5 g of the test grease was packed in a single row deep
groove ball bearing having an inner diameter of .phi.17 mm, an
outer diameter of .phi.47 mm, and a width of 14 mm, thereby
preparing a test bearing. This test bearing was integrated into an
alternator of an actual engine, and the engine was repeatedly
subjected to continuous rotation under the atmosphere at room
temperature at from 1,000 to 6,000 min.sup.-1 (the rotation number
of bearing: 2,400 to 13,300 min.sup.-1) under a pulley load of
1,560 N. At this time, a vibration value was measured, and when the
vibration value exceeded 5 times the initial value, it was
considered that flaking occurred. The test was carried out 10
times, and the number of times of occurrence of the flaking was
determined for a rotation time of less than 500 hours.
TABLE-US-00002 TABLE 2 Grease blending and test results Example 9
Example 10 Example 11 Example 12 Example 13 Thickener Diurea Diurea
Diurea Diurea Diurea Amine (aliphatic) (alicyclic + (alicyclic)
(alicyclic + (alicyclic + Ratio 100 aliphatic) 10/90 100 aliphatic)
30/70 aliphatic) 50/50 Amount of 15 13 18 16 20 thickener % by mass
Construction of PE TE TE TE TE base oil (100) (100) (100) (100)
(100) Hydrocarbon C8 C8 C7 to C9 C8, C10 C4 to C10 group of n-Octyl
2-Ethylhexyl Mixed n-Octyl, Decyl Mixed aromatic ester Rust
preventive [Sorbitan [Calcium [Zinc [Succinic half [Sorbitan
Addition amount trioleate naphthenate naphthenate ester (2)] +
monooleate (3)] + (2.5)] + (2)] + [Succinic (0.5)] + [Succinic
[Sorbitan [Zinc [Alkenylsuccinic half half monooleate (3)]
naphthenate (1)] acid (2.5)] ester (2)] ester (2.5)] + Total: 5%
Total 4% Total: 5% Total: 4% [Sorbitan monooleate (2.5)] Total:
5.5% Conductive CB CN + CB CB CB CN substance 1% 0.5% + 2% 5% 3% 3%
Kinematic 83 90 53 48 100 viscosity of base oil mm.sup.2/s
@40.degree. C. Worked No. 2 No. 2 to No. 1 No. 1 No. 2 No. 3
penetration Pour point of -38 -45 -48 -46 -48 base oil .degree. C.
High- Satisfactory Satisfactory Satisfactory Satisfactory
Satisfactory temperature penetration change Low-temperature
Satisfactory Satisfactory Satisfactory Satisfactory Satisfactory
abnormal noise test-II Seizure test-II Satisfactory Satisfactory
Satisfactory Satisfactory Satisfactory Rust preventing Satisfactory
Satisfactory Satisfactory Satisfactory Satisfactory test Flaking
0/10 0/10 0/10 0/10 0/10 resistance test Comparative Comparative
Comparative Example 14 Example 15 Example 3 Example 4 Example 5
Thickener Diurea Diurea Diurea Triurea Diurea Amine (alicyclic +
(aliphatic) (aliphatic) (aromatic) (aromatic) Ratio aliphatic) 100
100 100 100 70/30 Amount of 12 15 12 24 23 thickener % by mass
Construction of TE + ADE TE + PAO TE TE MO base oil (30:70) (50:50)
(100) (100) (100) Hydrocarbon C7 to C9 C8 C10 C8, C10 group of
Mixed 2-Ethylhexyl Decyl n-Octyl, Decyl aromatic ester Rust
preventive [Sorbitan [Succinic half [Zinc Succinic half Sorbitan
Addition amount monooleate (3)] + ester 3)] + [Sorbitan naphthenate
ester (0.5) trioleate (0.5) [Zinc monooleate (0.5)] + [Alkenyl-
0.5% 0.5% naphthenate (4)] (3)] + [Zinc succinic Total: 7%
naphthenate anhydride (3.5)] (0.5)] Total: 9.5% Total: 1%
Conductive CB + CN CB CB -- -- substance 4% 0.5% 7% Kinematic 80 60
160 48 97 viscosity of base oil mm.sup.2/s @40.degree. C. Worked
No. 1 No. 3 to No. 2 No. 4 to No. 3 No. 2 No. 2 penetration Pour
point of -40 -45 -15 -46 -25 base oil .degree. C. High-
Satisfactory Satisfactory Satisfactory Dissatisfactory
Dissatisfactory temperature penetration change Low-temperature
Satisfactory Satisfactory Dissatisfactory Satisfactory
Dissatisfactory abnormal noise test-II Seizure test-II Satisfactory
Satisfactory Satisfactory Satisfactory Satisfactory Rust preventing
Satisfactory Satisfactory Satisfactory Dissatisfactory
Dissatisfactory test Flaking 0/10 0/10 0/10 3/10 4/10 resistance
test TE: Trimellitic ester PAO: Poly-.alpha.-olefin (48 mm.sup.2/s
@40.degree. C.) ADE: Dialkyl diphenyl ether (100 mm.sup.2/s
@40.degree. C.) MO: Mineral oil (97 mm.sup.2/s @40.degree. C.) CB:
Carbon black CN: Carbon nano tube
[0064] As shown in Table 2, the test greases of the Examples
containing an aromatic ester oil-containing base oil and a diurea
compound represented by the general formula (IV) as a thickener
according to the invention are less in a change of the worked
penetration at a high temperature and excellent in high-temperature
endurance. Also, by packing each of the test greases of the
Examples, the seizure life of bearing can be improved, the
generation of abnormal noises at a low temperature can be
suppressed, and the rust preventing properties are improved.
Further, by containing a conductive powder, the flaking resistance
is improved. On the other hand, as in Comparative Example 3, in the
test grease containing excessively a conductive powder, the
acoustic characteristics are adversely affected, and abnormal
noises are generated at a low temperature. Also, as in Comparative
Example 4, even by using an aromatic ester oil-containing base oil,
when a triurea compound containing an aromatic hydrocarbon group is
used as a thickener, the high-temperature endurance is
deteriorated, and further, since the rust preventive is a succinic
half ester singly, the rust preventing performance is lowered.
Moreover, in Comparative Examples 4 and 5, since a conductive
powder is not contained, the flaking resistance is also
deteriorated.
(Verification-II of the Content of Aromatic Ester Oil)
[0065] Test greases were prepared according to the blending of the
test grease of Example 15, except for using a base oil wherein the
blending ratio of the trimellitic ester oil to the
poly-.alpha.-olefin oil was changed. Then, the foregoing (1)
seizure test-II was carried out using these test greases.
[0066] The relationship between the content of the trimellitic
ester oil and the seizure life is shown as a graph in FIG. 5.
Incidentally, the seizure life is shown in terms of a relative
value against the case of single use of the poly-.alpha.-olefin oil
(100%). As shown in the drawing, it is noted that when the
trimellitic ester oil is contained in an amount of 30% by mass or
more, the seizure life becomes especially good.
(Verification-II of the Blending Amount of Thickener)
[0067] Test greases were prepared according the blending of the
test grease of Example 11, except for changing the blending amount
of the thickener. Then, the foregoing (1) seizure test-II was
carried out using these test greases.
[0068] The relationship between the blending amount of the
thickener and the seizure life is shown as a graph in FIG. 6.
Incidentally, the seizure life is shown in terms of a relative
value against Comparative Example 5. As shown in the drawing, it is
noted that when the thickener is blended in an amount of from 5 to
35% by mass, especially from 10 to 30% by mass, the seizure life
becomes good.
(Relationship-II Between Pour Point of Base Oil and the Generation
of Abnormal Noises at a Low Temperature)
[0069] Base oils having a different pour point were prepared using
a pentaerythritol ester having a pour point of -55.degree. C. and a
pyromellitic ester having a pour point of -20.degree. C., and a
diurea compound containing an alicyclic hydrocarbon group was
blended with each of the base oils, thereby preparing test greases.
Incidentally, the blending amount of the diurea compound was made
constant, and the worked penetration was adjusted at No. 2. Then,
the foregoing (2) low-temperature abnormal noise test-II was
carried out using each of the test greases.
[0070] The relationship between the pour point of the base oil and
the generation of abnormal noises is shown in FIG. 7. It is noted
that when the pour point of the base oil is not higher than
-30.degree. C., abnormal noises are not generated.
(Verification of the Content of Carbon Black)
[0071] Test greases were prepared according to the blending of the
test grease of Example 9, except for changing the addition amount
of carbon black. Then, the foregoing (5) flaking resistance test
was carried out using these test greases, and a generation
probability of flaking was calculated according to the following
expression. [Generation probability of flaking (%)]=[(Number of the
generation of flaking)/(Number of tests)(=10)].times.100
[0072] The relationship between the addition amount of carbon black
and the generation probability of flaking is shown in FIG. 8. It is
noted that by adding carbon black in an amount of 0.5% by mass or
more, the generation of flaking is suppressed.
(Verification of Particle Size of Carbon Black)
[0073] Test greases were prepared according to the blending of the
test grease of Example 9, except for adding carbon black having a
particle size of from 34 nm to 6 .mu.m (however, the addition
amount was made constant at 5% by mass). Then, each of the test
greases was packed in a single tow deep groove ball bearing having
an inner diameter of .phi.17 mm, an outer diameter of .phi.47 mm,
and a width of 14 mm such that the test grease accounted for 35% of
a spacial volume, thereby preparing a test bearing. The test
bearing was subjected to rotation under the atmosphere at room
temperature at an inner race rotation speed of 1,800 min.sup.-1
under an axial load of 49 N, and an anderon value (180 to 10,000
Hz) for 120 seconds after the start of rotation was measured. The
case where the anderon value during this time is not more than 2.5
is considered to be satisfactory in the practical use.
[0074] The relationship between the particle size of carbon black
and the anderon value is shown in FIG. 9. It is noted that by using
carbon black having a particle size of not more than 5 .mu.m, the
flaking resistance can be imparted while keeping the acoustic
characteristics.
INDUSTRIAL APPLICABILITY
[0075] According to the invention, there is provided a grease
composition for auxiliary machinery of automobile electrical
component, which does not generate abnormal noises even at an
extremely low temperature of -40.degree. C., has excellent seizure
resistance even under a high temperature closed to 180.degree. C.,
and has excellent flaking resistance and rust preventing
performance. Also, according to the invention, there is provided a
rolling bearing which is suitable for electrical parts, auxiliary
machineries of engines, and the like.
* * * * *