Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Nitrogen and heavy metal – or nitrogen and aluminum – in the...
Reexamination Certificate
2000-04-21
2001-07-10
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Nitrogen and heavy metal, or nitrogen and aluminum, in the...
C508S272000, C508S364000, C508S379000, C508S444000, C508S552000, C508S569000
Reexamination Certificate
active
06258760
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a grease composition which is suited for a sliding part of a constant velocity joint (hereinafter abbreviated as “CVJ”) of automobiles.
BACKGROUND OF THE INVENTION
CVJ is a member for evenly transmitting the power of an engine to rotate right and left wheels at a given velocity. With the recent tendency to a front engine front drive (FF) system of automobiles, CVJ has shown marked development.
When a tripod type joint or a double offset type joint slides while transmitting torque, slide resistance develops in the axial direction. If this resistance is great, vibrations from the engine or the road are transmitted to the automobile body, becoming the source of vibrations of the body and booming noise. While mechanical improvements against this problem have been added to CVJ itself, the frictional resistance of CVJ can be reduced by using low-friction grease, which is effective in lessening the vibrations and noise of automobiles.
Therefore, grease to be applied to CVJ, particularly plunging type CVJ is keenly required to reduce frictional resistance of the sliding part. Grease having a low coefficient of friction is capable of reducing the friction of CVJ and thereby preventing generation of vibrations.
In order to meet the above demand, cases are increasing in the market, in which urea grease having high heat resistance and excellent frictional wear characteristics is used. The grease compositions disclosed in JP-A-6-57283 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-B-5-79280 (The term “JP-B” as used herein means an “examined Japanese patent publication”) can be mentioned as typical examples.
The grease composition for CVJ according to JP-A-6-57283 is urea grease containing (a) molybdenum disulfide, (b) molybdenum dialkyldithiocarbamate sulfide, and (c) a lead dialkyldithiocarbamate.
The grease composition for CVJ according to JP-B-5-79280 comprises urea grease and, as additives, a combination of molybdenum dithiocarbamate and molybdenum dithiophosphate, or a mixture of these organomolybdenum compounds and zinc dithiophosphate.
These grease compositions available from those references, especially when applied to plunging type constant velocity joints, make the induced thrust force smaller than with commercially available grease. However, vibrations occur in the shaft, and they are not regarded as satisfactory low-frictional grease.
An object of the present invention is to provide a grease composition for CVJ which has a low coefficient of friction to decrease the vibrations of CVJ.
SUMMARY OF THE INVENTION
The present inventors have extensively studied to further improve the technique of JP-B-5-79280. As a result, they have found that a combination of specific sulfur compounds with conventional techniques provides grease capable of suppressing vibrations of CVJ, i.e., grease having a lower coefficient of friction. The present invention has been completed based on this finding.
The present invention relates to a grease composition for a constant velocity joint, which comprises a base oil, a urea thickening agent, (A) a molybdenum dialkyldithiocarbamate, (B) at least one molybdenum di(alkyl or aryl)dithiophosphate represented by formula (I):
wherein R
1
represents a primary or secondary alkyl group or an aryl group, and (C) at least one sulfur-containing additive selected from the group consisting of an ashless dithiocarbamate, a polysulfide, zinc dithiocarbamate, sulfurized fat and oil, an olefin sulfide, a sulfur-phosphorus extreme pressure additive, and a thiadiazole extreme pressure additive, wherein each of the components (A), (B) and (C) is in an amount of 10% by weight or less based on the total weight of the grease composition. Unless otherwise indicated, all the percents are given by weight based on total weight.
In a preferred embodiment, the grease composition further comprises (D) 5% by weight or less, based on the total weight of the grease composition, of at least one zinc di(alkyl or aryl)dithiophosphate represented by formula (II):
wherein R
2
represents a primary or secondary alkyl group or an aryl group.
The present invention also relates to a method of decreasing the coefficient of friction, which comprises adding the grease composition to a constant velocity joint, the grease composition comprising the same.
DETAILED DESCRIPTION OF THE INVENTION
The base oil which can be used in the present invention includes mineral oil, synthetic oils such as ester oils, ether oils and hydrocarbon oils, and mixtures thereof.
Any urea thickening agent, including diurea compounds, triurea compounds, tetraurea compounds, and urea-containing compounds such as urea urethane compounds and urea imide compounds, can be used.
The content of each of additives (A), (B), and (C) in the grease composition is 10% by weight or less. Even if the content is more than 10% by weight, the effects produced are the same or rather reduced. Each of the additives (A) and (B) is preferably added in an amount of 3 to 5% by weight or less. Additive (C) is preferably added in an amount of about 1% by weight. It is preferred that (A), (B) and (C) be each used in an amount of at least 0.1% by weight.
The content of additive (D) is 5% by weight, or less, preferably 3% by weight or less. Even if the content is more than 5% by weight, the effects produced are the same or rather reduced. The minimal effective content is about 0.1% by weight. Where additive (D) is used in combination with additives (A) to (C), excellent effects can be achieved even with the amount of each additive minimized. In this case, the highest efficiency can result when each additive is used in an amount of 0.5 to 3% by weight.
If desired, other optional additives, such as antioxidants, rust inhibitors, and dispersants, may be added appropriately to the grease of the present invention as far as the effects of the present invention are not impaired.
The molybdenum dialkyldithiocarbamate as additive (A) includes molybdenum diethyldithiocarbamate sulfide, molybdenum dipropyldithiocarbamate sulfide, molybdenum
dibutyldithiocarbamate sulfide, molybdenum
dipentyldithiocarbamate sulfide, molybdenum
dihexyldithiocarbamate sulfide, molybdenum
dioctyldithiocarbamate sulfide, molybdenum
didecyldithiocarbamate sulfide, molybdenum
didodecyldithiocarbamate sulfide, molybdenum
di(butylphenyl)dithiocarbamate sulfide, molybdenum
di (nonylphenyl)dithiocarbamate sulfide, oxymolybdenum
diethyldithiocarbamate sulfide, oxymolybdenum
dipropyldithiocarbamate sulfide, oxymnolybdenum
dibutyldithiocarbamate sulfide, oxymolybdenum
dipentyldithiocarbamate sulfide, oxymolybdenum
dihexyldithiocarbamate sulfide, oxymolybdenum
dioctyldithiocarbamate sulfide, oxymolybdenum
didecyldithiocarbamate sulfide, oxymolybdenum
didodecyldithiocarbamate sulfide, oxymolybdenum
di(butylphenyl)dithiocarbamate sulfide, and oxymolybdenum di(nonylphenyl)dithiocarbamate sulfide, and mixtures thereof.
Examples of R
1
in formula (I) representing additive (B) are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, tetracosyl, cyclopentyl, cyclohexyl, methylcyclohexyl, ethylcyclohexyl, dimethylcyclohexyl, cycloheptyl, phenyl, tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, dodecylphenyl, tetradecylphenyl, hexadecylphenyl, octadecylphenyl, benzyl, and phenethyl groups. The four R
1
's may be the same or different.
Specific examples of additive (B) include molybdenum diethyldithiophosphate sulfide, molybdenum
dipropyldithiophosphate sulfide, molybdenum
dibutyldithiophosphate sulfide, molybdenum
dipentyldithiophosphate sulfide, molybdenum
dihexyldithiophosphate sulfide, molybdenum
dioctyldithiophosphate sulfide, molybdenum
didecyldithiophosphate sulfide, molybdenum
didodecyldithiophosphate sulfide, molybdenum
di(butylphenyl)dithiophosphate sulfide, molybdenum
di(nonylphenyl)dithiophosphate sulfide, oxymolybdenum
d
Asahara Yukio
Masumori Ryuichi
Nagasawa Keizo
Nishimura Takao
Ozaki Takahiro
McAvoy Ellen M.
Showa Shell Sekiyu K.K.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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