Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Ptfe
Reexamination Certificate
2001-09-28
2003-12-23
Johnson, Jerry D. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Ptfe
C508S182000, C508S258000, C508S552000
Reexamination Certificate
active
06667281
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a grease composition, in particular a grease composition that is used as a lubricant for gears and sliding parts. The present invention specifically relates to a grease composition that is excellent in lubricity even at low temperatures, abrasion resistance, and anti-seizure property, and is suitable for use with electrical equipment of marine engines, air craft engines, and vehicle engines, which require grease providing long service life, for example, starters including various sliding parts and gears such as helical gears, reduction gears, drive shafts, and levers.
BACKGROUND OF THE INVENTION
A starter for starting up marine engines, aircraft engines, and vehicle engines usually has a pinion gear, which is driven via an overrunning clutch by a drive shaft of a motor. Upon switching on the motor for start-up, a magnet coil is excited to cause a lever to slide the pinion gear toward a ring gear provided on the output shaft of an engine. The pinion gear then meshes with the ring gear to rotate and start up the engine.
An engine starter has various sliding parts and gears. For lubrication of such parts, greases are mainly used which contain a base grease composed of a lubricating base oil and a thickener such as a lithium soap, and additives such as molybdenum disulfide or molybdenum dithiocarbamate.
Greases for various engine starters are required to have properties to enable smooth start-up even at low temperatures (lubricity at low temperatures), abrasion resistance, anti-seizure property, heat resistance, and low friction. However, properties of conventional greases cannot keep up with the recent increase in frequency of engine starter activation due to the recent effort to stop idling of vehicle engines for reducing emission in the light of global environmental problems. Thus there is a strong demand for improvement in particularly abrasion resistance and anti-seizure property of greases in order to prolong their service life.
In addition, greases for engine starters are demanded that will not adversely affect the electric contacts of the engine starters.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a grease composition that has excellent abrasion resistance and anti-seizure property, long service life, exhibits excellent lubricity even at low temperatures, and has no adverse effect on electric contacts.
It is another object of the present invention to provide a grease composition suitable for use with electrical equipment and engine starters of vehicles and the like, which has excellent abrasion resistance and anti-seizure property, long service life, exhibits excellent lubricity even at low temperatures, and has no adverse effect on electric contacts, as well as a method for lubricating a vehicle electrical equipment or an engine starter with this composition.
According to the present invention, there is provided a grease composition comprising:
(A) a silicon-free synthetic oil having a kinematic viscosity of 10 to 60 mm
2
/s at 40° C.;
(B) a urea thickener;
(C) melamine cyanurate; and
(D) polytetrafluoroethylene.
According to the present invention, there is also provided a lubricating method comprising applying the above grease composition to a vehicle electrical equipment or an engine starter having an electric contact, or use of the grease composition.
PREFERRED EMBODIMENTS OF THE INVENTION
The present invention will now be explained in detail.
Component (A) of the present grease composition is a synthetic oil that contains no silicon and has a specific kinematic viscosity. Examples of such a silicon-free synthetic oil may include poly-&agr;-olefins such as polybutene, 1-octene oligomer, and 1-decene oligomer, and hydrides thereof; diesters such as ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, and di-3-ethylhexyl sebacate; polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, and pentaerythritol pelargonate; alkylnaphthalene; alkylbenzene; polyoxyalkylene glycol; polyphenyl ether; dialkyl diphenyl ether; and mixtures thereof. Among these examples, poly-&agr;-olefins, diesters, polyol esters, and mixtures thereof are preferably used.
Synthetic oils containing silicon, such as silicon oil, which have adverse effect on electric contacts, cannot be used.
The kinematic viscosity of component (A) at 40° C. should be not lower than 10 mm
2
/s, preferably not lower than 15 mm
2
/s, for suppressing evaporation at elevated temperatures and for preventing solidification of the grease to achieve sufficiently long lubricating life, and should be not higher than 60 mm
2
/s, preferably not higher than 50 mm2/s, for achieving sufficient lubricity at low temperatures.
As component (A), a mixture of a plurality of synthetic oils may be used, as long as the kinematic viscosity of the mixture falls within the above-mentioned range. It is not mandatory that each and every synthetic oil in the mixture has a kinematic viscosity within the range mentioned above. It is yet preferred, for giving the grease sufficient fluidity at low temperatures, that each and every synthetic oil in the mixture has a kinematic viscosity that falls within the above-mentioned range.
According to the present invention, the amount of component (A) contained in the grease composition is not particularly limited. However, in order to eliminate any possibility that the grease becomes too solid to exhibit sufficient lubricity, the content of component (A) is preferably not less than 50% by weight, more preferably not less than 60% by weight of the grease composition, and preferably not more than 95% by weight, more preferably not more than 90% by weight of the grease composition.
Component (A) constitute a base oil in the grease composition of the present invention. In addition to the synthetic oil of component (A), the base oil of the present grease composition may also contain a mineral oil, such as paraffin or naphthene oil, as long as the desired advantages of the present invention are achieved.
A mineral oil may have anadverse effect on electric contacts, and may impair the fluidity of the grease at low temperatures. Thus, the content of the mineral oil is preferably not more than 20% by weight, more preferably not more than 10% by weight of the grease composition, and most preferably, no mineral oil is contained in the grease composition.
The kinematic viscosity of the mineral oil is not particularly limited. However, for suppressing evaporation at higher temperatures and for preventing solidification of the grease to achieve sufficiently long lubricating life, the kinematic viscosity of the mineral oil at 40° C. is preferably not lower than 10 mm
2
/s, more preferably not lower than 15 mm
2
/s. On the other hand, for giving sufficient lubricity at low temperatures, the kinematic viscosity of the mineral oil is preferably not higher than 100 mm
2
/s, more preferably not higher than 80 mm
2
/s.
Component (B) of the present grease composition is a urea thickener. The urea thickener may be selected from, for example, urea compounds, urea-urethane compounds, urethane compounds, and mixtures thereof.
Examples of the urea compounds, urea-urethane compounds, and urethane compounds may include diurea compounds, triurea compounds, tetraurea compounds, polyurea compounds (other than di-, tri-, and tetraurea compounds), urea-urethane compounds, diurethane compounds, and mixtures thereof. Among these, diurea compounds, urea-urethane compounds, diurethane compounds, and mixtures thereof are particularly preferred.
More specifically, the urea thickener may preferably be a compound, or a mixture of compounds represented by the formula (1):
X—CONH—R
1
—NHCO—Y (1)
In the formula (1), R
1
stands for a divalent hydrocarbon group, and X and Y may be the same or different groups, each standing for —NHR
2
, —NR
3
R
4
, or —OR
5
, wherein R
2
, R
3
, R
4
, and R
5
may be the same or different groups, each standing for a
Ikejima Syouzou
Kinoshita Hirotugu
Sakamoto Kiyomi
Wakahara Yasuyuki
Darby & Darby
Johnson Jerry D.
Nippon Oil Corporation
LandOfFree
Grease composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Grease composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Grease composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3165977