The invention relates to an internal combustion engine conceived with the aim of combining the most advantageous aspects of a two-stroke engine with those of a four-stroke engine.

It is well known that the operating cycle of a two-stroke engine is performed with two strokes of the piston, one toward the B.D.C. (bottom dead center) and the other one toward the T.D.C. (top dead center), which force the driving shaft to perform one revolution.

- In the first stroke, which begins with the ignition of the spark between the electrodes of the spark plug, the mixture, which was previously compressed in the combustion chamber, explodes and the expansion of the burned gases forces the piston to descend toward the B.D.C. , covering the intake port and compressing the previously-aspirated mixture in the crankcase. During the descent and before reaching the B.D.C., the piston uncovers first the exhaust port for the egress outside of the burned gases and immediately afterward the transfer port through which the fresh mixture, compressed in the crankcase, flows into the cylinder and, by virtue of the difference in temperature, does not mix with the burned gases but facilitates the total egress thereof.

- In the second stroke, which corresponds to the return stroke toward the T.D.C. , the piston closes first the transfer port, then the exhaust port and then, by compressing the mixture in the cylinder, creates a partial vacuum in the crankcase that makes the fresh mixture flow into it from the carburetor.

At the end of the compression of the mixture in the cylinder, the spark ignites and the cycle is repeated.

In four-stroke engines the operating cycle is performed with four strokes or phases of the piston, which force the driving shaft to perform two revolutions.

- In the intake stroke, in which the intake valve is open and the exhaust valve is closed, the descent of the piston toward the B.D.C. causes the cylinder to be filled with the mixture of air and fuel aspirated from the carburetor.

- In the compression stroke, in which both valves are closed, the stroke of the piston toward the T.D.C. compresses all of the aspirated mixture in the combustion chamber.

- In the combustion stroke, a spark from the spark plug ignites the compressed mixture and the piston, pushed violently toward the B.D.C., transfers speed to the driving shaft.

- In the exhaust stroke, the return of the piston toward the T.D.C. by virtue of the momentum gained by the driving shaft in the preceding stroke causes the expulsion of the burned gases through the exhaust valve which is temporarily open.

From a comparison of the two engines described, it can be seen first of all that the two-stroke engine, which has the advantage that it has an active stroke for each revolution of the driving shaft and therefore theoretically twice the power with respect to that of a four-stroke engine of the same cubic capacity which has an active stroke every two revolutions, has the further advantage of the absence of valves and of the corresponding distribution mechanism which, being operated by the camshaft, is synchronized with the movement of the driving shaft by which it is moved.

In fact both the valves and the distribution mechanism are replaced by simple slots or ports provided in the cylinder which are opened and closed at the appropriate time by the passage of the piston in motion. It is obvious that all this makes the construction of a two-stroke engine simpler and cheaper than a four-stroke engine of the same cubic capacity.

But the above mentioned advantages are counteracted by drawbacks which are determined by the fact that in the two- stroke engine the lubrication of the moving elements is obtained by adding a quantity of oil to the gasoline which, while it is necessary to prevent the linkages and pistons from seizing, will bum and cause pollution. Furthermore the volumetric efficiency is lower owing to the dilution of the carburated mixture owing to the imperfect washing of the burned gases and also because part of that mixture escapes, during the washing step, through the exhaust ports. This results in higher consumption of gasoline per horsepower/hour and a reduction in power which, effectively, is not twice that of a four-stroke engine but merely 40-60% greater.

The aim of the present invention is to devise an internal combustion engine that combines the most advantageous aspects of a two-stroke engine with those of a four-stroke engine.

The internal combustion engine according to the invention, which is improved in light of the above considerations, is described below with reference to the enclosed drawings in which, solely for the purposes of non limiting example:

- Figures 1, 2 and 3 show three steps of the two-stroke cycle of a first embodiment of the engine according to the invention;

- Figures 4, 5 and 6 show three steps of the two-stroke cycle of a second embodiment of the engine according to the invention.

With reference to the figures and starting from the ones showing the first embodiment of the internal combustion engine, it can be seen that it is an embodiment characterized first of all in that the movement of the piston 1 inside the cylinder 2 causes the opening and also the closing of one or more ports 4 connected to a conventional compressor 3, together with the corresponding opening and closing of one or more ports 5 connected to the exhaust duct 6 for the burned gases.

In particular, upon the ignition of the spark between the electrodes of the spark plug 7 (Figure 1), the combustion of the compressed mixture of air and fuel in the combustion chamber forces the piston 1 to descend suddenly toward the B.D.C..

During the descent and up until the return toward the T.D.C., the piston 1 uncovers the ports 4 and 5 (Figure 2), allowing the clean air, introduced by the compressor 3, to expel the entirety of the burned gases through the exhaust duct 6.

After the ports 4 and 5 have been closed by the return of the piston 1 (Fig. 3), the residue of clean air, present in the cylinder 2 after the expulsion of the burned gases, is mixed with the fuel that the injector 8, regulated by a control unit, introduces until, when the return of the piston 1 and the compression of the mixture formed are complete, combustion occurs (Figure 1) and the cycle starts again.

From an examination of the drawings in Figures 4, 5 and 6 it can be seen that the second embodiment of the internal combustion engine is characterized first of all in that the movement of the piston 1 inside the cylinder 2 causes the opening and also the closing of one or more ports 5 connected to the exhaust duct 6 for the burned gases.

In particular, upon the ignition of the spark between the electrodes of the spark plug 7 (Fig. 4), the combustion of the compressed mixture of air and fuel in the combustion chamber forces the piston 1 to descend suddenly toward the B.D.C..

During the descent and up until the return toward the T.D.C., the piston 1 uncovers one or more ports 5, as it is necessary to expel, through the exhaust duct 6, the burned gases pushed by the clean air introduced by the injector 10 (Figure 5).

This is an injector controlled by a control unit based on the programmed timings in order to optimize first the washing of the combustion chamber and then the oversupply of air in the mixture to be formed with the fuel injected by the injector 8 (Figure 6), which is also regulated by a control unit.

It is evident that, differently from the first embodiment, i.e. embodiment in Figures 1, 2 and 3, in which the dosing of the mixture can be regulated only through the quantity of fuel that the injector 8 introduces into the remaining air inside the cylinder 2 after the expulsion of the burned gases and the closing of the ports 4 and 5, the second embodiment, the one in Figures 4, 5 and 6, also has the advantage that, after the closing of one or more ports 5 of the exhaust duct 6 (Figure 6), the fuel injector 8 and also the air injector 10 intervene to precisely dose the two components in the necessary quantities in each instance to optimize the yield of the engine in any operating condition.

While different in terms of the capacity to dose the mixture inside the cylinder 2, both versions shown and described focus on a two-stroke engine that, as such, has an active stroke for each revolution of the driving shaft and has no valves because they are replaced by simple ports.

Furthermore, in the engine in the two versions, the injection of the fuel into the cylinder occurs only after the perfect washing of the combustion chamber and the lubrication of the moving elements has been obtained, inside the crankcase 9, by way of an oil bath, sprayed oil or the like.

The disclosures in Italian Utility Model application No. 202018000002297 from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.