Continued use of a proper lubricating oil is essential for the maintenance of any internal combustion engine. The use of an appropriate lubricating system not only enhances engine performance, but prolongs the effective life of the engine. Standard lubricating systems for internal combustion engines generally comprise a petroleum-based oil. Such an oil functions in the engine to facilitate the movement of engine parts, to minimize wear due to friction, to remove heat from the engine parts, to absorb shocks between engine parts, to form a seal between piston rings and piston cylinder walls, and to cleanse the engine.
Due to the range of performance that is demanded from it, a satisfactory lubricating oil must have several properties. Primary among these is a favorable viscosity rating. Viscosity is a measure of the resistance of a liquid to flow. The viscosity of an oil determines the ease with which engine parts move with respect to each other. Viscosity may be influenced by temperature, pressure, and shear forces due to fluid movement. For example, as temperatures increase, lubricant oil viscosity tends to breakdown, resulting in increased fluidity. The viscosity index is an empirical system for expressing the change in viscosity with changing temperatures on a scale from 0 to 100. However, oils with a viscosity index of greater than 100 may be manufactured from crude oils by the addition of, for example, polymers to the oil.
During prolonged exposure to high temperatures in an engine (and to fluctuations between high and low temperatures) a reduction in viscosity may occur. Thus, at temperatures at which an engine operates, the oil may become more fluid in character, making the oil more susceptible to penetration during the application of heavy loads. For example, during the application of a load, an oil with the proper viscosity will form a film around bearings to allow movement and to create a seal, for example, between piston rings and cylinder walls, and will help absorb shock. Upon a reduction in viscosity, the oil will form a less-adequate seal and will not maintain the necessary film on bearings and the like, resulting in wear on engine parts due to friction.
Another important property of lubricant oils is a resistance to carbon formation. At the high temperatures which result from operation of most engines, oil may be burned to produce carbon. Formation of carbon on engine components results in poor engine performance by, for example, causing piston rings to stick to ring grooves in the cylinder housing the piston. Obviously, carbon formation also results in inefficient utilization of the oil.
A good lubricating oil should also be resistant to oxidation. At high temperatures, oils become oxidized and the products of oxidation may coat engine parts, retarding movement. However, perhaps the greatest contributor to the loss of effectiveness of lubricant oil is the formation and accumulation of contaminants. Acids, as well as carbon, produced by the breakdown of engine oil may form in the combustion chamber, resulting in inefficient engine operation.
Largely as a result of the accumulation of contaminants, viscosity breaks down, both in terms of flow and resistance to penetration. That, among other factors, causes wear on engine parts which, in turn, requires more oil consumption for proper function. Accordingly, engine oil must be changed on a regular basis in order to prevent permanent damage to engine components. Most commercially-available engine oils contain additives (e.g., detergents) which reduce the accumulation of contaminants. However, such additives do not prevent the breakdown in viscosity and accumulation of acidic waste products and carbon which result from prolonged use of engine oil. Typically, automobile manufacturers recommend that oil be changed after 3000 miles of operation, which amounts to about 100-250 hours of engine operation. Replacement intervals for other types of engines vary depending upon the type of engine and the use to which the engine is put.
As shown by the foregoing, there is a need in the art for materials and methods for prolonging the working life of a lubricating oil in an engine and for preventing lubricant oil breakdown as provided in the present invention, a summary of which follows.
USPTO Backgrounds
USPTO Backgrounds