US2896593A - Method for operating two-cycle engines - Google Patents

Description

Lawrence E. Riemenschneider, Chelsea, Mich.

N Drawing. Application Augusti8, 1955 7 Serial No. 527,163 n i 2 Claims. onizer-1 The present invention relates to lubricant motor fuels for two-cycle engines and lubricant additives useful in the production of such fuels.

Inthe operation of gas engines of the two-cycle type, the lubricating oil is mixed directly with the gasolene or other fuel, as distinguished from other types of gas engines in which the lubricating oil is retained in the crankcase. The mixture consisting of gasolene and a minor proportion of lubricating oil is fed to the combustion chamber, where it is burned. However, the design and carburetion adjustment of the two-cycle engine is necessarily directed toward obtaining the greatest efficiency and maximum horsepower from the gasolene proper, since the best performance of the engine is obviously dependent upon proper combustion of the component which forms by far the greatest part ofthe fuel mixture. Thus, the lubricant must burn as best it can; and in the case of lubricants known heretofore, faulty combustionof the lubricant component of the fuel mixture has led to a great deal of difiiculty.

In particular, faulty combustion of the lubricant component of the fuel mixture has heretofore resulted in carbon and sludge deposits which interfere with the exhaust port and cause fouling ofthe sparkplugs and sticking of the rings.Moreover, excessive carbon deposits have tended to build up on the head of the piston and in the cylinder head and ring grooves. These difficulties have led to marked reduction in power delivery and have required frequent disassembly and cleaning of the two-cycle engine. With a new, clean engine, no more than thirty hours of operation before cleaning could heretofore be expected; and upon subsequent operation, the time between plug cleaning has dropped to a fraction of this number of hours and in some cases has fallen to less than one hour.

Apart from the reduction in power and necessity'for frequent cleaning resulting from such deposits, a further difficulty has arisen apart from operation of the engine and as a result of mere storage of the engine containing fuel mixtures known to the prior art. This difficulty has manifested itself in the form of gummy deposits forming a coating on metal parts commonly known in the art as varnish.

Although many attempts Were made to overcome the foregoing difficulties and other disadvantages, none, so

far as I am aware, was entirely successful when carried into practice commercially on an industrial scale.

Accordingly, it is an object of my invention to provide a lubricant motor fuel for two-cycle engines, which will leave no appreciable residue upon combustion.

A further object of the invention is the provision of a lubricating additive for mixture with two-cycle engine fuel, such that the entire mixture will vaporize or burn without leaving an appreciable deposit on the engine parts. i

A still further object of my invention is the provision of a lubricating fuel for two-cycle engines, which will rates Patent U 2,896,593 Patented July 28, 1959 2 permit storage of the engine with greatly reduced gum formation.

Other objects and advantages of the present invention will become apparent from the following description and examples.

The lubricating oil component of my invention consists of polymersof olefins of which the monomers have not more than five carbon atoms. Among the operative embodiments are polymers of ethylene, propylene, butylene, isobutylene, and amyline; and particularly preferred is isobutylene. Polymerization of these mono nrgr s to the extent necessary to produce a lubricating oil 'may be carried out according to the method of any of US. Patents Numbers 2,278,445, April 7, 1942, 2,301,052 November 3, 1942, 2,318,719, May 11, 1943, 2,329,714, September 21, 1943, 2,345,574, April 4 1944, or 2,422,443, June 17, 1947. Although the operative embodiments of monomers are selected from the lower ethylene series, it will of course be understood that tiny amounts of polymers formed from higher monomers will not seriously affect the operativeness ofthe invention.

Temperatures up to aboutSOO degree Fahrenheit are encountered adjacent the crankcase and cylinder walls of two-cycle engines; and the polymers of the lower ethylene series described above will remain stable somewhat beyond that temperature range. However, the polymers according to the invention will depolymerize to a gaseous state at around 625 degrees Fahrenheit. Inasmuch as the temperatures reached during combustion of the fuel mixture are substantially above this latter temperature, it is obvious that the polymer components of the mixture will retain their lubricatingfunction until combustion and willthen completely depolymerize, leaving no residue. Thus, it does not matter that the polymeric lubricant component of the fuel mixture does not burn completely in the combustion chamber, since the unburned portion depolymerizes at the combustion temperatures and is completely exhausted as the monomeric gas from which the polymeric component was initially formed.

Fuel mixtures according to my invention are formed by the thorough mechanical mixing of a small proportion of polymeric lubricant additive according to the. invention with a liquid fuel such as gasolene or naptha. The two components are mutually miscible. A preferred proportion of polymeric lubricant additive is 6% by volume of the whole. A substantially smaller proportion of lubricant additive gives a decreased lubrication effeet; and higher proportions are not only wasteful but also decrease the efficiency of performance. However, when the two-cycle engine is new and in being broken in," it may be desirable to use a somewhat richer mixture including polymeric lubricant additive in the amount of about 9% by volume of the whole.

Although the use of polymeric lubricant additives in fuel mixtures according to my invention greatly reduces the amount of harmful deposit when used with a gasolene of any type, it was nevertheless found that some of the deposit was due to the use of generally available gasolenes containing lead and produced by the so-called cracking processes. These gasolenes produced by cracking contain a relatively high proportion of unstable molecules known to the art as wild molecules which combine with metals and other substances to form varnishes and gums. Moreover, certain components of the residues left by these commonly available gasolenes are electrically conductive at the temperatures encountered in the combustion chamber of a two-cycle engine, although the deposits would be virtually harmless in a four-cycle engine. Heretofore, the harmful effect of the residues left by the commonly available gasolenes containing lead and produced by cracking processes had been completely masked by the greater residues left by lubricant additives heretofore used.

Thus, it was found desirable also to provide the further refinement of the compositionof fuel mixtures according to my invention, comprising the use of lead-freestraight run gas olenes as the major component of the fuel. By straight run'gasolene is meant the natural cat which is obtained from crude oil by ordinary distillation before the remaining crude oil is subjected to cracking for the production of cracked gasolene. Thus, straight run gasolene is sharply distinguished from cracked gasolene, which latter has by contrast a relatively high proportion of wild molecules,

For the purpose of enabling those skilled in the art to practice the invention, the following exemplary illustration is given:

As a lubricant additive, a polymer of isobutylene was selected, having a pour point of minus 20 degrees Fahrenheit, a flash point of 215 degrees Fahrenheit, a'

viscosity at 100 degrees Fahrenheit of 230 Saybolt seconds and a viscosity at 210 degrees Fahrenheit of 50 Saybolt seconds, and a viscosity index of 114. This additive was mixed inthe amount of 6% by volume of the whole with a'straight run gasolene known as stove and lighting napth-a having a lead content of 0, an octane number of 65, a sulphur content of 0.02%, an A.P.-I. gravity of 64.5 degrees, and'a boiling point range'initially at 109 degrees Fahrenheit, 10% at 156 degrees Fahrenheit, at 169 degrees Fahrenheit, at 192 degrees Fahrenheit, at 206 degrees Fahrenheit, at 216 degrees Fahrenheit, at 231 degrees Fahrenheit, at 245 degreesFahrenheit, at .265 degrees Fahrenheit, at 294 degrees Fahrenheit, and an end boiling point at 339 degrees Fahrenheit. The mixture was borned as fuel in a two cycle engine; and after 48 hours of operation, no appreciable deposit ofresidue was noticed in the exhaust port, on the piston'head, in the cylinder head, or in the ring groove. Without removal of the fuel from the engine, the engine was permitted to stand for a month; and after the expiration ofthis'l'atter time, no appreciable deposit of varnish or gum was noticed on any'of the parts. f

Thus, from a consideration of the foregoing disclosure,

4 it will be obvious that I have achieved all of the initially recited objects of my invention.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

I claim:

1. A method of avoiding carbon and sludge residues on the parts of a two-cycle engine upon combustion and of reducing gum formation on the engine parts during storage of a two-cycle engine, which comprises operating a said two-cycle engine on a fuel consisting essentially of a mixture of lead-free, straight run gasolene, and a small but effective amount, from about 6% to about 9% by volume of the whole, of polymers of olefins of which the monomers have not more than .five carbon atoms.

2. A method of, avoiding carbon and sludge residues on the parts of a two-cycle'engine upon combustion and of reducing gum formation on the engine parts during storage of a two-cycle engine, which comprises'operating a said two-cycle engine on a fuel consisting essentially of a mixture of lead-free, straight run gasolene, and a small but effective amount, from about 6% to about 9% by volume of the whole, of polymers of isobutylene.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain Oct. 4., 1933'