U.S. patent application number 12/344993 was filed with the patent office on 2010-01-21 for grease composition for constant velocity joint.
This patent application is currently assigned to HYUNDAI MOTOR COMPANY. Invention is credited to Sung Uk Lee.
Application Number | 20100016194 12/344993 |
Document ID | / |
Family ID | 41530812 |
Filed Date | 2010-01-21 |
United States Patent
Application |
20100016194 |
Kind Code |
A1 |
Lee; Sung Uk |
January 21, 2010 |
GREASE COMPOSITION FOR CONSTANT VELOCITY JOINT
Abstract
A grease composition for a constant velocity joint is provided,
which comprises a mineral oil as a base oil along with an
alicyclic-aliphatic diurea thickener, a sulfur-ester-based
additive, molybdenum dithiocarbamate (Mo-DTC), molybdenum
dithiophosphate (Mo-DTP) and zinc dithiophosphate (Zn-DTP) as
additives. The composition improves NVH performance by lowering a
generated axial force and P.R. (plunging resistance) while
increasing abrasion resistance.
Inventors: |
Lee; Sung Uk; (Gyeonggi-do,
KR) |
Correspondence
Address: |
EDWARDS ANGELL PALMER & DODGE LLP
P.O. BOX 55874
BOSTON
MA
02205
US
|
Assignee: |
HYUNDAI MOTOR COMPANY
Seoul
KR
|
Family ID: |
41530812 |
Appl. No.: |
12/344993 |
Filed: |
December 29, 2008 |
Current U.S.
Class: |
508/365 |
Current CPC
Class: |
C10M 2215/1026 20130101;
C10M 2219/068 20130101; C10N 2030/76 20200501; C10M 2219/024
20130101; C10M 2223/045 20130101; C10N 2040/04 20130101; C10M
169/06 20130101; C10N 2050/10 20130101; C10N 2030/02 20130101; C10N
2030/06 20130101; C10M 2219/068 20130101; C10N 2010/12 20130101;
C10M 2223/045 20130101; C10N 2010/04 20130101; C10M 2223/045
20130101; C10N 2010/12 20130101; C10M 2219/068 20130101; C10N
2010/12 20130101; C10M 2223/045 20130101; C10N 2010/12 20130101;
C10M 2223/045 20130101; C10N 2010/04 20130101 |
Class at
Publication: |
508/365 |
International
Class: |
C10M 141/10 20060101
C10M141/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 15, 2008 |
KR |
10-2008-0068744 |
Claims
1. A grease composition for constant velocity joint comprising: (a)
75.0-88 wt % of a base oil; (b) 7.0-10.0 wt % of a thickener
comprising an aliphatic diurea and an alicyclic diurea in a mixing
ratio of 1:2.2-1:2.4 by weight; and (c) 3.6-15 wt % of an additive
comprising a sulfur-ester-based additive, molybdenum
dithiophosphate (Mo-DTP), molybdenum dithiocarbamate (Mo-DTC) and
zinc dithiophosphate (Zn-DTP).
2. The composition of claim 1, wherein the base oil is a mineral
oil having a dynamic viscosity of 60-100 mm.sup.2/s at 40.degree.
C.
3. The composition of claim 1, wherein the alicyclic diurea is a
compound of the following Formula 1:
R.sup.1NH--CO--NH--C.sub.6H.sub.4-p-CH.sub.2--C.sub.6H.sub.4-p-HN--CO--NH-
R.sup.1 [Formula 1] wherein R.sup.1 is a C.sub.6 cyclohexyl
group.
4. The composition of claim 1, wherein the aliphatic diurea is a
compound of the following Formula 2:
2,4-[R.sup.2NH--CO--NH].sub.2--C.sub.6H.sub.3--CH.sub.3 [Formula 2]
wherein R.sup.2 is a C.sub.18 oleyl group.
5. The composition of claim 1, wherein the additive comprises
1.0-3.0 wt % of a sulfur-ester-based additive, 0.1-1.0 wt % of
molybdenum dithiophosphate, 1.50-4.0 wt % of molybdenum
dithiocarbamate, and 1.0-3.0 wt % of zinc dithiophosphate.
6. The composition of claim 1, wherein the molybdenum
dithiocarbamate is a compound of the following Formula 3:
[R.sup.3R.sup.4N--CS--S].sub.2--Mo.sub.2O.sub.mS.sub.n [Formula 3]
wherein R.sup.3 and R.sup.4 are independently a C.sub.1-C.sub.24
alkyl group; and m is an integer of 0-3 and n is an integer of 1-4
with m+n being 4.
7. The composition of claim 1, wherein the molybdenum
dithiophosphate is a compound of the following Formula 4:
##STR00002## wherein R.sup.5, R.sup.6, R.sup.7 and R.sup.8 are
independently a C.sub.1-C.sub.24 primary or secondary alkyl or a
C.sub.6-C.sub.30 aryl group.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims under 35 U.S.C. .sctn.119(a) the
benefit of Korean Patent Application No. 10-2008-0068744 filed Jul.
15, 2008, the entire contents of which are incorporated herein by
reference.
BACKGROUND
[0002] (a) Technical Field
[0003] The present invention relates to a grease composition for a
constant velocity joint.
[0004] (b) Background Art
[0005] A constant velocity joint receives a driving or braking
torque and transmits the torque regardless of angle of deviation in
two axes connected to the joint. A grease applied to the constant
velocity joint reduces a lateral direction shaking, which is
generated in sudden acceleration or braking in low gear and causes
shudder vibration of a vehicle. The grease also prevents shudder
vibration of a vehicle with an automatic transmission in idle mode.
However, when the grease has a low abrasion resistance, an abnormal
abrasion can occur between a wheel and a roller depending on angle
of deviation of a joint, thereby causing the shudder vibration.
SUMMARY OF THE DISCLOSURE
[0006] One of the objects of the invention is to provide a grease
composition for a constant velocity joint that can decrease
friction between metals while increasing abrasion resistance and
improving lubricating properties.
[0007] The grease composition according to one aspect of the
present invention comprises a mineral oil as a base oil along with
a urea-based thickener, a sulfur-ester-based additive, molybdenum
dithiocarbamate (Mo-DTC), molybdenum dithiophosphate (Mo-DTP) and
zinc dithiophosphate (Zn-DTP).
[0008] The above and other aspects of the invention is discussed
infra.
DETAILED DESCRIPTION
[0009] Reference will now be made in detail to the preferred
embodiments of the present invention. The embodiments are described
below so as to explain the present invention by referring to the
figures.
[0010] A grease composition for a constant velocity joint according
to the present invention comprises: (a) 75.0-88 wt % of a base oil;
(b) 7.0-10.0 wt % of a thickener comprising an aliphatic diurea and
an alicyclic diurea in a mixing ratio of 1:2.2-1:2.4 by weight; and
(c) 3.6-15 wt % of an additive comprising a sulfur-ester-based
additive, molybdenum dithiophosphate (Mo-DTP), molybdenum
dithiocarbamate (Mo-DTC) and zinc dithiophosphate (Zn-DTP).
[0011] As the base oil, although any known base oils for a grease
composition for a constant velocity joint can be used in the
present invention, a mineral oil is preferred. Examples of the
mineral oil include solvent-purified or hydrogenated paraffin-based
mineral oils and naphthene-based mineral oils.
[0012] Preferably, the base oil may have a dynamic viscosity of
60-100 mm.sup.2/s at 40.degree. C. If the dynamic viscosity is
lower than 60 mm.sup.2/s, the base oil may be evaporated due to
insufficient thermal resistance. If the dynamic viscosity is higher
than 100 mm.sup.2/s, it will increase torque and heat emission.
[0013] Suitably, the base oil is contained in a grease composition
in the amount of 75.0-88.0 wt %. If the amount of the base oil is
less than 75.0 wt %, the grease will not be applicable due to
excessive solidification. If the amount is more than 88.0 wt %, it
will cause the oil separation too high and also cause softening
problem.
[0014] The thickener used in the present invention may comprise (i)
an alicyclic diurea of Formula 1 prepared by reacting
diphenylmethane-4,4-diisocyanate (MDI) with cyclohexyl amine and
(ii) an aliphatic diurea of Formula 2 prepared by reacting toluene
diisocyanate (TDI) and oleyl amine in an appropriate mixing ratio.
Suitably, the thickener is contained in a grease composition
preferably in the amount of 7.0-10.0 wt %. When the amount is less
than 7.0 wt %, the composition may result in a liquid phase with
high penetration, thus easily causing oil separation. When the
amount is more than 10.0 wt %, fluidity can be lowered due to
solidification of grease.
R.sup.1NH--CO--NH--C.sub.6H.sub.4-p-CH.sub.2--C.sub.6H.sub.4-p-HN--CO--N-
HR.sup.1 [Formula 1]
[0015] where R.sup.1 is a C.sub.6 cyclohexyl group.
2,4-[R.sup.2NH--CO--NH].sub.2--C.sub.6H.sub.3--CH.sub.3 [Formula
2]
[0016] where R.sup.2 is a C.sub.18 oleyl group.
[0017] A urea-based thickener can be prepared by reacting isocyante
with an amine compound. To avoid unreacted amine group, isocyante
is preferred to be mixed with an approximately equivalent amount of
the amine compound.
[0018] Moreover, a preferable mixing ratio of the aliphatic diurea
and the alicyclic diurea is 1:2.2-1:2.4 considering the hardening
property at high temperature and the softening property under
sheared conditions.
[0019] The additive is contained in a grease composition preferably
in the amount of 3.6-15 wt %, and the additive may preferably
include a sulfur-ester-based additive, Mo-DTP, Mo-DTC and
Zn-DTP.
[0020] In particular, Mo-DTC and Mo-DTP, which are used for
improving friction and avoiding abrasion, have a structure of the
following Formulas 3 and 4, respectively.
[R.sup.3R.sup.4N--CS--S].sub.2--Mo.sub.2O.sub.mS.sub.n [Formula
3]
[0021] where R.sup.3 and R.sup.4 are independently a
C.sub.1-C.sub.24 alkyl group; and m is an integer of 0-3 and n is
an integer of 1-4 with m+n being 4.
##STR00001##
[0022] where R.sup.5, R.sup.6, R.sup.7 and R.sup.8 are
independently a C.sub.1-C.sub.24 primary or secondary alkyl or a
C.sub.6-C.sub.3 aryl group.
[0023] The additive is used for improving friction property,
extreme pressure property and abrasion resistance. A preferable
amount of Mo-DTC is 1.5-4.0 wt % relative to the total weight of
the grease composition. When the amount is more than 4.0 wt %, no
improvement of properties can be anticipated. When the amount is
less than 1.5 wt %, the improvement of friction property can be
insufficient. A preferable amount of Mo-DTP is 0.1-1.0 wt %
relative to the total weight of the grease composition. If the
amount is more than 1.0 wt %, the increase in abrasion resistance
can level off. If the amount is less than 0.1 wt %, the abrasion
resistance can be lowered.
[0024] The sulfur-ester-based additive is used in the amount of
1.0-3.0 wt % relative to the total weight of the grease composition
for maintaining a stable friction coefficient and abrasion
resistance relative. If the amount is outside the aforementioned
range, friction and abrasion properties become unstable.
[0025] Zn-DTP is used for improving the friction property of
molybdenum dithiocarbamate in the amount of 1.0-3.0 wt % relative
to the total weight of the grease composition. If the amount is
more than 3.0 wt %, the increase in abrasion resistance can level
off. If the amount is less than 1.0 wt %, the abrasion resistance
can be insufficient.
[0026] In an embodiment, the grease composition may further
comprise the conventional additives such as extreme pressure
additives, antioxidants and anticorrosive agents besides the
aforementioned additives, i.e., a sulfur-ester-based additive,
Mo-DTP, Mo-DTC and Zn-DTP.
[0027] Any known extreme pressure agent can be used in the present
invention to improve the load resistance and the extreme pressure
property. Examples of the extreme pressure agent include organic
zinc compounds such as zinc dithiocarbamate, zinc dithiophosphate
and zinc phenate; organic antimony compounds such as antimony
dithiocarbamate and antimony dithiophosphate; organic bismuth
compounds such bismuth naphthenate and bismuth dithiocarbamate;
organic sulfonate, phenate or phosphenate of alkali metal or
alkaline earth metals; and organic metal compounds such as of gold,
silver, titanium or cadmium. Also, sulfur-based extreme pressure
agents can be used. Examples of sulfur-based extreme pressure agent
include sulfides such as dibenzyldisulfide, polysulfide, oil
sulfides, ashless carbamate compounds, thiourea-based compound and
thiocarbonates. In addition, phosphate-based extreme pressure
agents can be used. Examples of phosphate-based extreme pressure
agents include phosphate esters such as trioctylphosphate,
tricredylphosphate; and acid phosphate esters such as phosphorous
ester and acid phosphorous ester. Furthermore, chlorinated extreme
pressure agents such as chlorinated paraffin and solid lubricants
such as molybdenum disulfide, tungsten disulfide, graphite,
polytetrafluoroethylene (PTFE), antimony sulfide, boron nitride can
be used.
[0028] Examples of the antioxidants include age resistors and
ozone-deterioration-preventing agents, which are conventionally
contained in rubber, plastics and lubricants. Examples of such
compounds include amine compounds such as phenyl-1-naphthyl amine,
phenyl-2-naphthyl amine, diphenyl-p-phenylene diamine, dipyridyl
amine, phenothiazine, N-methylphenothiazine, N-ethylphenothiazine,
3,7-dioctylphenothiazine, p,p'-dioctyldiphenyl amine,
N,N'-diisopropyl-p-phenylene diamine and
N,N'-di-sec-butyl-p-phenylene diamine; and phenol-based compounds
such as 2,6-di-tert-dibutylphenol.
[0029] Examples of the anticorrosive agents include sulfonates of
alkali metal or alkaline earth metal such as ammonium salt, barium,
zinc, calcium and magnesium of organic sulfonate; organic
carbonates; organic phenates; organic phosphonates; alkyl or
alkenyl succinic acid derivatives such as alkyl or alkenyl succinic
acid ester; partial esters of polyhydric alcohol such as sorbitan
monostearate; hydroxyl fatty acids such as oleoyl sarcosine;
mercaptofatty acids or metal salt thereof such as 1-mercaptosteatic
acid; higher fatty acids such as stearic acid; higher alcohols such
as isostearyl alcohol; ester of higher alcohol and higher fatty
acid; thiazoles such as 2,5-dimercapto-1,3,4-thiadiazole and
2-mercaptothiadiazole; imidazoles such as
2-(decyldithio)-benzoimidazole and benzoimidazole; disulfides such
as 2,5-bis(dodecyldithio)benzoimidazole; phosphate esters such as
trisnonylphenylphosphite; thiocarbonate ester such as
dilaurylthiopropionate; and nitrites.
[0030] The urea-based thickener improves the mechanical stability
and water resistance of the grease composition. The
sulfur-ester-based additive, Mo-DTP, Mo-DTC and Zn-DTP added to a
mixture of the aforementioned base oil and urea thickener improves
friction property and abrasion resistance of the grease
composition, thereby maintaining Lubricating effect for a long
time.
EXAMPLES
[0031] The following examples illustrate the invention and are not
intended to limit the same.
Preparation Example 1
Preparation of Alicyclic Diurea (Thickener)
[0032] 4,500 g of base oil and 558 g of
diphenylmethane-4,4'-diisocyanate were mixed and heated at
70-80.degree. C. A mixture of 4,500 g of base oil and 442 g of
cyclohexyl amine was added to the heated mixture. The resulting
mixture was sufficiently mixed, heated up to 170.degree. C. and
placed at room temperature, thus providing a base urea grease.
Preparation Example 2
Preparation of Aliphatic Diurea (Thickener)
[0033] 4,500 g of base oil and 362.7 g of toluene-2,6-diisocyanate
were sufficiently mixed, and added with a mixture of 4,550 g of
base oil and 537.3 g of oleyl amine. The resulting mixture was
sufficiently mixed, heated up to 170.degree. C. and placed at room
temperature, thus providing a base urea grease.
Examples 1-3 and Comparative Examples 1-2
[0034] Grease compositions for a constant velocity joint were
prepared by using ingredients as shown in Table 1. A mineral oil
(dynamic viscosity at 40.degree. C.: 95 cSt) was used as a base
oil. A urea-based thickener was prepared by mixing the aliphatic
diurea (Preparation Example 2) and the alicyclic diurea
(Preparation Example 1) in the mixing ratio of 1:2.3.
TABLE-US-00001 TABLE 1 Ex. Comp. Ex. Ingredients (wt %) 1 2 3 1 3
Base oil Mineral oil 85.7 85.5 87.3 86 87.5 Thickener Alicyclic
diurea 6.6 6.3 6.3 9.5 -- Aliphatic diurea 2.9 2.7 2.7 -- 9.0
Additive Molybdenum 2.2 2.0 1.7 -- 2.0 dithiocarbamate.sup.1)
Molybdenum 0.1 -- -- 0.1 -- dithiophosphate.sup.2) Sulfur
ester.sup.3) 1.0 2.0 1.0 1.0 -- Zinc dithiophosphate.sup.4) 1.5 1.5
1.0 1.5 1.5 .sup.1)Molybdenum dithiocarbamate: Sakuralube 200 of
Adeka Co., Ltd. .sup.2)Molybdenum dithiophosphate: Sakuralube 300
of Adeka Adeka Co., Ltd. .sup.3)Sulfur ester: Lubrizol 5333 of
Lubrizol Co., Ltd. .sup.4)Zinc dithiophosphate: RC3180 of
RheinChemie Co., Ltd.
Test Examples
Measurement of Properties
[0035] Properties of the grease compositions for a constant
velocity joint prepared in Examples 1-3 and Comparative Examples
1-2 were measured as follows, and the results are presented in
Table 2.
[0036] 1) Worked penetration was measured according to ASTM D
217,
[0037] 2) propping point was measured according to ASTM D 566.
[0038] 3) Oil separation was measured according to ASTM D6184.
[0039] 4) Friction coefficient (SRV) was measured under the
following conditions according to ASTM D 5707-05 (A standard method
for measuring the friction property and the abrasion resistance of
a grease by using high-frequency SRV tester)
[0040] Load: 100N, 300N and 500N
[0041] Speed: 10 Hz
[0042] Distance: 4 mm
TABLE-US-00002 TABLE 2 Ex. Comp. Ex. Properties 1 2 3 1 3 Worked
penetration 321 325 323 325 325 (at 25.degree. C.) Dropping point
(.degree. C.) 235 237 234 235 232 Oil separation (wt %) 0.7 0.6 0.7
0.7 0.7 Friction coefficient 0.060 0.070 0.068 0.09 0.105 (SRV)
[0043] As shown in Table 2, the grease compositions prepared by
using a urea-based thickener with a relatively high limit
heat-resistant temperature in Examples 1-3 were ascertained as
superior in oil separation and dropping point showing durability
and operability at high temperature. Furthermore, the grease
compositions prepared in Examples 1-3 were superior to those of
Comparative Examples in friction property because a
sulfur-ester-based additive, Mo-DTP, Mo-DTC and Zn-DTP were
used.
[0044] A grease composition for constant velocity joint of the
present invention is effective in stably maintaining friction
coefficient by using Zn-DTP and a sulfur-ester-based additive. A
grease composition for constant velocity joint of the present
invention is also superior in lowering friction coefficient between
metals, increasing abrasion resistance and decreasing a generated
axial force and P.R. value by using Mo-DTP and Mo-DTC.
[0045] The invention has been described in detail with reference to
preferred embodiments thereof. However, it will be appreciated by
those skilled in the art that changes may be made in these
embodiments without departing from the principles and spirit of the
invention, the scope of which is defined in the appended claims and
their equivalents.
* * * * *