U.S. patent application number 12/530119 was filed with the patent office on 2010-02-04 for grease composition and machine elements.
Invention is credited to Shinya Kondo, Daigo Nagumo.
Application Number | 20100029521 12/530119 |
Document ID | / |
Family ID | 39738351 |
Filed Date | 2010-02-04 |
United States Patent
Application |
20100029521 |
Kind Code |
A1 |
Kondo; Shinya ; et
al. |
February 4, 2010 |
GREASE COMPOSITION AND MACHINE ELEMENTS
Abstract
A grease composition which contains a large amount of thickener,
and may prevent a flaking effectively for a long period of time,
and machine elements in which the grease composition is filled are
provided. A grease composition comprising a thickener and a base
oil, characterized in that the thickener contains a diurea compound
represented by the Formula (I):
R.sup.1--NHCONH--R.sup.2--NHCONH--R.sup.3, (I) wherein R.sup.1 and
R.sup.3 are a phenyl group and/or a cyclohexyl group, R.sup.2 is a
C.sub.6-C.sub.15 divalent hydrocarbon group, and the molar ratio of
cyclohexyl group/(cyclohexyl group+phenyl group) in R.sup.1 and
R.sup.3 is 0.95 to 0.10.
Inventors: |
Kondo; Shinya; (Kanagawa,
JP) ; Nagumo; Daigo; (Kanagawa, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Family ID: |
39738351 |
Appl. No.: |
12/530119 |
Filed: |
March 10, 2008 |
PCT Filed: |
March 10, 2008 |
PCT NO: |
PCT/JP2008/054280 |
371 Date: |
September 4, 2009 |
Current U.S.
Class: |
508/386 |
Current CPC
Class: |
C10M 115/08 20130101;
F16C 33/6633 20130101; C10N 2040/02 20130101; C10N 2050/10
20130101; C10M 2207/0406 20130101; C10M 2207/003 20130101; C10M
2203/1006 20130101; C10M 2215/1026 20130101; C10N 2030/08 20130101;
C10M 169/02 20130101; C10N 2040/04 20130101 |
Class at
Publication: |
508/386 |
International
Class: |
C10M 133/00 20060101
C10M133/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 8, 2007 |
JP |
2007-058772 |
Claims
1. A grease composition comprising a thickener and a base oil,
characterized in that the thickener contains a diurea compound
represented by the Formula (I): R1-NHCONH--R2-NHCONH--R3, (I)
wherein R1 and R3 are a phenyl group and/or a cyclohexyl group, R2
is a C6-C15 divalent hydrocarbon group, and the molar ratio of
cyclohexyl group/(cyclohexyl group+phenyl group) in R1 and R3 is
0.95 to 0.10.
2. The grease composition according to claim 1, wherein the base
oil comprises a mineral oil.
3. The grease composition according to claim 1, wherein the base
oil comprises a phenyl ether based synthetic oil.
4. The grease composition according to claim 1, which is for
rolling lubrication units and/or rolling-sliding lubrication
units.
5. The grease composition according to claim 1, which is for
constant velocity joints and/or gears for automobiles.
6. The grease composition according to claim 1, which is for
rolling bearings.
7. A machine element in which the grease composition according to
claim 1 is filled.
8. The machine element according to claim 7, which is a constant
velocity joint and/or a gear for automobiles.
9. The machine element according to claim 7, which is a rolling
bearing.
Description
TECHNICAL FIELD
[0001] The present invention relates to a grease composition and
machine elements, and particularly, to a grease composition which
is suitably used for rolling bearings and constant-velocity joints
for automobile instruments or auxiliaries, and to a rolling
bearing, or constant-velocity joints in which the grease
composition is filled.
BACKGROUND ART
[0002] The service life of lubrication units used for rolling and
rolling-sliding is associated with fatigue, i.e. flaking. In order
to prevent this flaking and prolong the service life, it is
required to decrease the frequency of direct contact of both
surfaces lubricating with each other. As a method of not contacting
both the surfaces each other, a measure is generally taken to
increase the viscosity of the lubricating oil, i.e. the base oil in
the grease, and to thicken the oil layer.
[0003] However, some amount of thickener is needed in order for
this effect to be demonstrated. On the other hand, when the amount
of the thickener is too high, the property of the grease
composition to easily flow into a lubricating unit is impaired, and
therefore, a countermeasure thereto is required.
[0004] Such a property of the grease composition is strongly
required when machine elements to be lubricated are
constant-velocity joints, gears or rolling bearings for
automobiles.
[0005] As greases used for rolling bearings for automobile
instruments or auxiliaries, a diurea grease in which the base oil
mainly comprises a synthetic hydrocarbon oil and a phenyl ether
synthetic oil is used. Among diurea greases, particularly aromatic
diurea is often used because of its high temperature
resistance.
[0006] However, this kind of grease lacks the property to easily
flow into the lubricating unit and thus generates a flaking due to
insufficiency of lubricant.
[0007] On the other hand, as an example of providing the inflow
property by a thickener,
[0008] Patent Document 1 proposes a grease characterized in that a
gelling agent is incorporated as an essential ingredient in a base
oil comprising more than 50% by weight of ether synthetic oil,
which gelling agent comprises at least one of diurea compounds
represented by the following general formula,
R.sup.2--NHCONH--R.sup.1--NHCONH--R.sup.3,
[0009] wherein R.sup.1 represents a C.sub.6-C.sub.15 divalent
aromatic hydrocarbon group, R.sup.2 and R.sup.3 are the same or
different groups and each of R.sup.2 and R.sup.3 represents a
cyclohexyl group, a C.sub.7-C.sub.12 cyclohexyl derivative group or
a C.sub.8-C.sub.20 alkyl group, and in which gelling agent, the
content ratio of cyclohexyl group or derivative group thereof
[{(cyclohexyl group or derivative group thereof)/(cyclohexyl group
or derivative group thereof+alkyl group).times.100} is 50 to 100%.
However, with this grease, the thickener is short and needs
improvement in the flaking.
[0010] Patent Document 1 JP 2979274 B
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0011] An object of the present invention is to provide a grease
composition which contains a large amount of a thickener and which
prevents flaking effectively for a long period and which has an
excellent inflow property, and machine elements in which the grease
is filled.
[0012] Another object of the present invention is to provide a
grease composition which, if used for machine elements such as
constant-velocity joints, gears, rolling bearing and the like, has
an improved property to easily flow into the lubrication unit and
has a long fatigue life even under high temperature conditions, and
machine elements in which the grease is filled.
Means for Solving the Problems
[0013] The present invention provides the grease composition
described below and machine elements using the grease
composition.
1. A grease composition comprising a thickener and a base oil,
characterized in that the thickener contains a diurea compound
represented by the Formula (I),
R.sup.1--NHCONH--R.sup.2--NHCONH--R.sup.3, (I)
[0014] wherein R.sup.1 and R.sup.3 are a phenyl group and/or a
cyclohexyl group, R.sup.2 is a C.sub.6-C.sub.15 divalent
hydrocarbon group, and the molar ratio of cyclohexyl
group/(cyclohexyl group+phenyl group) in R.sup.1 and R.sup.3 is
0.95 to 0.10.
2. The grease composition according to the above-described item 1,
wherein the base oil comprises a mineral oil. 3. The grease
composition according to the above-described item 1, wherein the
base oil comprises a phenyl ether based synthetic oil. 4. The
grease composition according to any one of the above-described
items 1 to 3, which is for rolling lubrication units and/or
rolling-sliding lubrication units. 5. The grease composition
according to any one of the above-described items 1 to 4, which is
for constant velocity joints and/or gears for automobiles. 6. The
grease composition according to any one of the above-described
items 1 to 4, which is for rolling bearings. 7. A machine element
in which the grease composition according to any one of the
above-described items 1 to 4 is filled. 8. The machine element
according to the above-described item 7, which is a constant
velocity joint and/or a gear for automobiles. 9. The machine
element according to the above-described item 7, which is a rolling
bearing.
EFFECTS OF THE INVENTION
[0015] Because the grease composition of the present invention
contains a sufficient amount of thickener and the inflow property
of the grease composition into the lubrication unit is improved,
the fatigue life of machine elements such as constant-velocity
joint, gear and bearing is long.
[0016] The grease composition of the present invention may be
generally applied to rolling bearing. Particularly, the grease
composition of the present invention may suitably be used for
rolling bearings for automobile instruments or auxiliaries which
rolling bearings have flaking problems. Such bearings include
electromagnetic clutches for automobile air conditioners; bearings
used for intermediate pulley, idler pulley and tension pulley and
bearings used for alternators.
[0017] Further, the grease composition of the present invention is
suitably used for constant velocity joints such as fixed-type
(e.g., Rzeppa-type and Barfield-type) constant-velocity joints; and
slide-type (e.g., double offset type and cross groove type)
constant-velocity joints.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0018] Generally, in a rolling lubrication system or a
rolling-sliding lubrication system, a 1 flaking is associated with
the service life, which needs improvement. The present invention
was completed based on the finding that a grease composition which
uses a specific diurea thickener may effectively prevent the direct
contact between both the surfaces lubricating each other, and
improves anti-flaking property without increasing the viscosity of
the base oil. The grease composition of the present invention
comprising a specific diurea compound as a thickener easily enters
between the lubricating surfaces of rolling to prevent the direct
contact of both the surfaces of the metals and to effectively
prevent a flaking.
[0019] The base oil used for the present invention is not
restricted and those usually used for grease compositions may be
employed. A base oil having a kinematic viscosity of 10 to 400
mm.sup.2/s, more preferably 20 to 250 mm.sup.2/s, and still more
preferably 40 to 150 mm.sup.2/s at a temperature of 40.degree. C.
is preferred.
[0020] Examples of the base oil include mineral oils, synthetic
oils and natural oils. Examples of the synthetic oils include
hydrocarbon oils, aromatic oils, ester oils and ether oils.
Examples of the hydrocarbon oils include poly-.alpha.-olefins such
as normal paraffin, isoparaffin, polybutene, polyisobutylene,
1-decene oligomer, 1-decene and ethylene co-oligomer and
hydrogenation products thereof. Examples of the aromatic oils
include alkyl benzenes such as monoalkyl benzenes and dialkyl
benzenes and alkyl naphthalenes such as monoalkyl naphthalenes,
dialkyl naphthalenes and polyalkyl naphthalenes. Examples of the
ester oils include diester oils such as dibutyl sebacate,
di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate,
ditridecyl adipate and ditridecyl glutarate; aromatic ester oils
such as trimellitic acid esters, pyromellitic acid esters; polyol
ester oils such as trimethylolpropane esters, pentaerythritol
esters and dipentaerythritol esters; and complex ester oils which
are oligoesters of polyhydric alcohols and fatty acid mixtures of
dibasic acid monobasic acid. Examples of the ether oils include
polyglycols such as polyethylene glycol, polypropylene glycol,
polyethylene glycol mono-ethers and polypropylene glycol
mono-ethers; and phenyl ether oils such as monoalkyl triphenyl
ethers, alkyl diphenyl ethers, pentaphenyl ether, tetraphenyl
ether, monoalkyl tetraphenyl ethers and dialkyl tetraphenyl ethers.
Examples of other synthetic oils include tricresyl phosphate,
silicone oils and perfluoro alkyl ethers. Examples of the natural
oils include fats and oils such as beef tallow, lard, soybean oil,
rape oil, rice bran oil, coconut oil, palm oil, palm kernel oil and
hydrogenation products thereof. These base oils may be used
individually or as a mixture of two or more of them.
[0021] Mineral oils and alkyl diphenyl ethers are particularly
preferred.
[0022] The thickener used for the grease composition of the present
invention is a diurea compound represented by the above-described
formula (I). R.sup.1 and R.sup.3 are a phenyl group and/or a
cyclohexyl group, and the molar ratio of cyclohexyl
group/(cyclohexyl group+phenyl group) in R.sup.1 and R.sup.3 is
0.95 to 0.10, and preferably 0.90 to 0.15.
[0023] In the formula (I), R.sup.2 is a C.sub.6-C.sub.15 divalent
hydrocarbon group such as a linear or branched alkylene group, a
linear or branched alkenylene group, a cycloalkylene group or an
aromatic group.
[0024] The diurea thickener used in the present invention may be
obtained by, for example, reacting a prescribed diisocyanate and a
prescribed monoamine. Preferred specific examples of the
diisocyante include diphenylmethane-4,4'-diisocyanate (MDI) and
tolylene diisocyanate (TDI).
[0025] As the monoamine, a mixture of aniline and cyclohexylamine
is used in a prescribed ratio. A mixture of a diurea obtained from
a diisocyanate and aniline, and a diurea obtained from a
diisocyanate and cyclohexylamine, containing the diureas at the
above-described prescribed ratio may also be used.
[0026] The content of the thickener in the grease composition of
the present invention may be the amount which is appropriate for
obtaining the required consistency, and the content is usually
preferably 1 to 20%, more preferably 2 to 20% by mass based on the
total mass of the grease composition.
[0027] The grease composition of the present invention may contain
additives such as extreme pressure additives, antioxidants, rust
preventives and anticorrosives, which are usually used for grease
compositions.
EXAMPLES
[0028] The present invention will now be described specifically by
way of the following examples.
[0029] A diurea compound was prepared by reacting
diphenylmethane-4,4'-diisocyanate with aniline and/or
cyclohexylamine in a prescribed ratio in a base oil. Then the base
oil was added to the diurea compound in an amount to attain a
consistency of 300 to prepare a test grease composition.
[0030] The base oils used are the following two kinds.
Mineral oil: 500 neutral oil (kinematic viscosity at 40.degree. C.:
100 mm.sup.2/s) Alkyl diphenyl ether oil: MORESCO HILUBE LB 100
(Matsumura Oil Research Corp.; kinematic viscosity at 40.degree.
C.: 100 mm.sup.2/s)
[0031] The fatigue life test of the grease composition was
estimated by the following rolling four ball test.
[0032] Outline of Rolling Four Ball Test Method
[0033] Three bearing steel balls having a diameter of 15 mm are
provided and placed into a cylindrical container having an inside
diameter at the bottom of 36.0 mm, an inside diameter at the top
end of 31.63 mm and a depth of 10.95 mm, and then 20 g of a test
grease is applied. On the tops of these three steel balls, a steel
ball for bearing having a diameter of 5/8 inches is contacted and
when the steel ball is rotated at a prescribed rotation rate, the
bottom three steel balls revolve while rotating. These steel balls
are allowed to rotate continuously until a flaking occurs on the
surface of the steel ball.
[0034] A flaking occurs between balls where the contact pressure is
the highest.
[0035] The fatigue life is defined as a total rotation number at
the time when a flaking occurs.
[0036] Test Condition
[0037] Test steel ball: (.PHI.5/8 inch steel ball for bearing
(rotating ball), (.PHI.15 mm steel ball for bearing (driven
ball)
[0038] Test load (W): 400 kgf (6.5 Gpa)*
[0039] Rotation rate (n): 1500 rpm
[0040] Number of repeated tests: 5 (average life: average of five
tests)
[0041] Maximum Herzian pressure between balls. The value of 6.5 Gpa
represents a very high contact pressure and a state where the oil
film is considerably thin is resulted.
[0042] The compositions of the grease compositions and the test
results are show in Table 1 and Table 2.
TABLE-US-00001 TABLE 1 Examples 1 2 3 4 5 R.sup.1, R.sup.3 phenyl
100 90 50 15 0 molar ratio cyclohexyl 0 10 50 85 100 amount of
thickener 22 18 16 12 10 (% by mass) base oil mineral oil
consistency 300 fatigue life (.times.1000) 200 3000 5500 4200
1800
TABLE-US-00002 TABLE 2 Examples 6 7 8 9 10 R.sup.1, R.sup.3 phenyl
100 90 50 15 0 molar ratio cyclohexyl 0 10 50 85 100 amount of
thickener 22 18 16 12 10 (% by mass) base oil alkyl diphenyl ether
oil consistency 300 fatigue life (.times. 1000) 350 4200 6100 4800
2200
[0043] With the grease compositions (Example 1 and Example 6) where
100% of R.sup.1 and R.sup.3 are phenyl groups in the formula (I),
since the amount of the thickener was too high for the grease
composition to sufficiently flow into the lubrication unit, a
flaking occurred early to reach a fatigue life. On the other hand,
with the grease compositions (Example 5 and Example 10) where 100%
of R.sup.1 and R.sup.3 are cyclohexyl groups in the formula (I),
since the content of diurea compound was too small, a satisfactory
fatigue life was not obtained.
[0044] In contrast, with the grease compositions of Examples 2-4
and Examples 7-9 where the molar ratio of cyclohexyl
group/(cyclohexyl group+phenyl group) in R.sup.1 and R.sup.3 is
0.95 to 0.10 in the formula (I), the time for a flaking to occur
was extremely long, and which is therefore effective for preventing
occurrence of a flaking in CVJs, gears, rolling bearings and the
like.
[0045] These results show that the grease composition of the
present invention is effective for preventing all the flaking
events such as subsurface-initiated flaking and surface-initiated
flaking.
* * * * *