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...
Patent
1996-03-19
1997-09-30
McAvoy, Ellen M.
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...
508365, 508373, 508374, 508518, C10M14110, C10M14100
Patent
active
056725728
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel lubricating oil composition, in particular, a lubricating oil composition having improved friction reducing properties and wear resistance and suitable for use as a lubricating oil for internal combustion engines, automatic transmissions, suspension and power steering wheels, particularly as a lubricating oil for internal combustion engines.
2. Description of the Related Art
Lubricating oils are usually used for smoothing the operation of internal combustion engines, driving mechanisms such as automatic transmissions, suspensions and power stearings, and gears. Particularly, engine oils are effective in lubricating mainly sliding parts such as a piston ring and a cylinder liner, bearings of a crank shaft or a connecting rod, and valve trains including cams and valve lifters; in cooling the engine; in cleaning and dispersing combustion products; and in preventing rust formation and corrosion.
Thus, various functions are required of the engine oils and, recently, even better functions are being demanded as the required performance and engine output become higher and higher and the operation conditions more severe. Under these circumstances, additives such as a corrosion inhibitor, metallic detergent, ashless dispersant and antioxidant are incorporated into the engine oil in order to satisfy such requirements.
It is an important basic function of an engine oil to drive the engine smoothly and to prevent wear and seizure under any given condition. In the lubricated parts of an engine, a fluid lubrication state is mostly realized. However, in the valve train and the top and the bottom dead centers of a piston, a boundary lubrication state is apt to occur. In such a boundary lubrication, wear is usually prevented by addition of zinc dithiophosphate (ZnDTP) or zinc dithiocarbamate (ZnDTC).
Since the energy loss in the friction parts in which the lubricating oil participates is high in the engine, a friction modifier (FM) is added to the lubricating oil in order to minimize the friction loss and improve the fuel consumption. As the friction modifiers, extreme-pressure additives such as molybdenum compounds and phosphoric esters and oiliness improvers such as fatty acid esters and alkylamines are usually used.
However, when a combination of the antiwear agent with the friction modifier is used, the functions of both of them are not fully exhibited because of their competitive adsorption onto the metal surface. More specifically, ZnDTP and ZnDTC protect the metal surface from wear due to metal/metal contact by forming a protective film thereon, while the friction modifier also forms a low-friction film by the adsorption onto the metal surface, by the reaction therewith or by the formation of a polymer on the metal surface to reduce the friction. Therefore, when both ZnDTP or ZnDTC and the friction modifier are added to the lubricating oil, the adsorption of ZnDTP and ZnDTC is reduced in amount by the competitive adsorption onto the metal surface to reduce the wear resistance or no sufficient friction-reducing effect can be obtained even by the addition of the friction modifier.
On the other hand, an interaction between ZnDTP or ZnDTC and some detergent-dispersant is apt to occur to reduce the wear resistance. Further, other additives such as the detergent-dispersant might exert an influence on the effect of the friction modifier. Thus, the selection of other additives such as the detergent-dispersant and the concentration thereof must be taken into consideration.
The present invention has been completed after investigations made for the purpose of providing a lubricating oil composition having improved friction reduction and antiwear properties and suitable for use as a lubricating oil for internal combustion engines, automatic transmissions, suspension and power steering wheels, particularly as a lubricating oil for internal combustion engines.
SUMMARY OF THE INVENTION
After intensive investigations made for the purpo
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Arai Katsuya
Asano Satoshi
Wada Sadao
Allocca Joseph J.
McAvoy Ellen M.
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