Lubricant composition for use the reduction of piston ring fouling in an internal combustion engine

Abstract

The present invention relates to a lubricant composition comprising a base oil or base oil blend and one or more additives, wherein the lubricant composition has a kinematic viscosity at 100° C. of more than 5.0 mm2 / s (cSt), a cold cranking simulated dynamic viscosity at −15° C. according to ASTM D 5293 of less than 9500 mPas (cP) and a mini rotary viscosity test value of less than 60000 mPas at −20° C. according to ASTM D 4684, and wherein the base oil or base oil blend has been obtained from a waxy paraffinic Fischer-Tropsch synthesized hydrocarbon fraction and comprises a continuous series of isoparaffins having n, n+1, n+2, n+3 and n+4 carbon atoms, wherein n is between 15 and 35, suitable for the reduction of piston ring fouling in an internal combustion engine.

Description

FIELD OF INVENTION[0001]The present invention relates to a lubricant composition, and to the use of the lubricant composition for the reduction of piston ring deposits in a combustion engine.BACKGROUND OF THE INVENTION[0002]In the recent decades, use of internal combustion engines for transportation and other means of energy generation has become widespread. In particular compression ignited internal combustion engines which are also known as “Diesel engines” after Rudolf Diesel, who invented the first compression ignition engine in 1892, feature among the main type of engines employed for passenger cars in Europe, and globally for heavy duty applications, as well as for stationary power generation as a result of their high energy efficiency. In a compression-ignited internal combustion engine a fuel / air mixture is ignited by being compressed until it ignites due to the temperature increase due to compression, rather than by a separate source of ignition, such as a spark plug as in ...

AI Technical Summary

Benefits of technology

[0009]The engine for which the package according to the invention is to be employed is lubricated, i.e. the lubricant forms a film between surfaces of parts moving against each other so as to minimize direct contact between them. This lubricating film decreases friction, wearing, and production of excessive heat between the moving parts. Also as a moving fluid, the lubricant transposes heat from surfaces of lubricated parts due to friction from parts moving against each other or the oil film. Typically, an internal combustion engine has a crankcase, cylinder head, and cylinders. The lubricant is typically present in the crankcase, where crankshaft, bearings, and bottoms of rods connecting pistons to the crankshaft are submerged in the lubricant. The rapid motion of these parts causes the lubricant to splash and lubricate the contacting surfaces between the piston rings and interior surfaces of the cylinders. This lubricant film also serves as a seal between the piston rings and cylinder walls to separate the combustion volume in the cylinders from the space in the crankcase.

[0010]Without wishing to be bound to any particular theory, it is believed that the presence of the residual lubricant film reduces the temperature of the piston and interior surfaces of the cylinder, thereby reducing the formation of soot and sludge.

[0014]By virtue of the Fischer-Tropsch process, a Fischer-Tropsch derived base oil has essentially no, or undetectable levels of, sulphur and nitrogen. Compounds containing these heteroatoms tend to act as poisons for Fischer-Tropsch catalysts and are therefore removed from the synthesis gas feed. This can yield additional benefits, in terms of effect on catalyst performance, in fuel compositions in accordance with the present invention.

[0028]The base oils as derived from a Fischer-Tropsch wax as here described will be referred to in this description as Fischer-Tropsch derived base oils. Blends of different base oil grades or fractions having different viscosity may also be employed. This has the advantage that a large range of lubricant viscosity is available.

[0055]The lubricant used in the package according to the invention may comprise as the base oil component exclusively the paraffinic base oil, or a combination of the paraffinic base oils and ester as described above, or alternatively in combination with another additional base oil. The additional base oil will suitably comprise less than 20 wt %, more preferably less than 10 wt %, again more preferably less than 5 wt % of the total fluid formulation. Examples of such base oils are mineral based paraffinic and naphthenic type base oils and synthetic base oils, for example poly alpha olefins, poly alkylene glycols and the like. The amounts are limited by the nitrous oxide reduction that is to be attained. Preferably, the lubricant further comprises saturated cyclic hydrocarbons in an amount of from 5 to 10% by weight, based on the total lubricant since this improves the low temperature compatibility of the different components in the lubricant.

[0070]In a further aspect, the present invention provides for a method of lubricating a compression-ignited internal combustion engine comprising operating the engine and lubricating the engine with a lubricating oil composition of the first aspect. In yet a further aspect, the present invention provides a method of improving piston cleanliness and reducing the ring-sticking tendencies of a compression-ignited internal combustion engine comprising adding to the engine a lubricating oil composition according to the present invention. In yet a further aspect, the present invention provides a combination comprising the crankcase of a compression-ignited internal combustion engine, preferably having a specific power output of 25 kW / litre or greater, and a lubricating oil composition according to the invention.

Problems solved by technology

As set out above, applicants have found that the use of a lubricant comprising a Fischer-Tropsch derived base oil leads to a significant and unexpected synergistic increase in piston cleanliness.

This lubricating film decreases friction, wearing, and production of excessive heat between the moving parts.

The rapid motion of these parts causes the lubricant to splash and lubricate the contacting surfaces between the piston rings and interior surfaces of the cylinders.

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