DESCRIPTION

Field of application

The present invention relates to an internal-combustion engine functioning according to the Otto (Beau de Rochas) thermodynamic cycle or the Diesel thermodynamic cycle, but having, as compared to traditional four-stroke engines having the same or similar dimensions and cubic capacity, a weight-to-power ratio that is approximately halved and, as compared to two-stroke engines, a higher thermodynamic efficiency.

The applications of the engine are the same as those of traditional engines but with the peculiarity that the production cost per unit weight for four-stroke engines is approximately halved given the same power yield. Moreover, if it is installed on transport and locomotion means, added to the above advantage is a lower weight of the means, with the consequent advantages that, according to the various cases of use, derive therefrom.

Prior art

The most widespread thermal engine with reciprocating motion of an internal- combustion type (whether with Otto cycle or Diesel cycle) is the four-stroke engine.

The two-stroke engine with similar features and dimensions, which in theory should have twice the power, is used exclusively in the motorcycle field for small cubic capacities (50 cm ³ , 125 cm ³ , and rarely 250 cm ³ ) of an Otto-cycle type and in marine engines for propulsion of larger-sized ships (e.g., container ships, VLCCs, and ULCCs) according to the Diesel cycle; the remaining applications may be in emergency generator systems, by virtue of the simplicity and reliability of the system for generation of mechanical energy and of the low likelihood of use.

In these engines, immediately after spontaneous exhaust of the fumes, there occurs the so-called flushing, i.e., forced exhaust of the residual fumes still present within the cylinder into the exhaust manifold (or duct). Said flushing takes place by the action of the fresh intake gases at the intake of the cylinder, which albeit only partial causes exit through the exhaust manifold, of the residual fumes of the previous cycle, mixing in part with the latter, exit unburnt into the atmosphere. The simultaneous occurrence of these two phenomena reduces the thermal efficiency to the point of rendering the two-stroke engine unusable in the majority of cases.

In addition, both the low efficiency and the above phenomenon cause introduction of unburnt hydrocarbons into the environment, which are a source of intolerable pollution even above the limits imposed by current regulations.

Aim and description of the invention

The aim of the present invention is to provide an engine with an active phase of delivery of mechanical energy at each revolution of the shaft, and hence having approximately twice the power as compared to four-stroke engines of similar dimensions, but with approximately the same thermal efficiency and quality of the fumes.

Conversely, to provide an engine that has a weight that is approximately half the weight of a traditional four-stroke engine having the same performance levels and the same power (and hence an engine with a lower production cost, approximately halved).

Adoption of the above engine, as well as being justified by the lower production cost, may be useful in applications where it is convenient to have low weights, namely: in the aviation field for enabling a light weight of the means and an increase in the payload and/or autonomy and/or speed, hence with reduction of the flight times. In the field of naval transport for enabling increase in the gross carrying capacity and/or in the autonomy of the means, or in the speed to obtain shorter navigation times; and in the field of land wheeled transport for enabling an increase in autonomy or alternatively in the volume of the internal spaces in the case of transport means for passengers or goods with low specific weight or an increase in autonomy and/or carrying capacity in the case of maximum limits for the total weight of the means.

In particular, for motorcycles, the possibility of having a lower weight given the same power can improve manageability of the means, enabling higher accelerations thereof and, given the same weight, increasing their autonomy.

In the following an example of embodiment of the present invention is described with reference to the attached drawings, wherein Figures 1 to 20 illustrate a complete operating cycle of the engine according to the invention.

In the drawings and in the description, parts that are the same as or equivalent to one another are designated by the same reference numbers.

With reference to the drawings, the engine according to the invention comprises, in a way in itself known, a cylinder 1 , sliding in which, with reciprocating motion is a piston 3 connected to a connecting rod-crank transmission system (items 4, 5, 6, 7, 8, 9), said piston 3 being slidable between a bottom dead centre and a top dead centre. Two ducts of an appropriate shape are designated by 2, 2’, which give out, on diametrally opposite sides (but in a longitudinal position to be determined also experimentally), into said cylinder 1 at said bottom dead centre, one 2 for intake of the air or of the fresh gases, and the other 2’ for exhaust of the burnt gases.

Shut-off valves are designated by 10, 10’, if required, for shutting off communication between said intake and exhaust ducts 2 and 2’, respectively, and said cylinder 1. Finally, designated by 11 is the intake valve and by 1 T the exhaust valve set at the head of the cylinder 1 in a position corresponding to the top dead centre of the stroke of the piston 3.

The characteristic of the engine according to the invention lies in the fact that mounted between the piston 3 and the head of the cylinder 1 is a thin diaphragm 12 of an appropriate shape, referred to in what follows as“disk” or“separator”, the lateral surface of which has the shape of a straight circular cylinder and which has a nominal diameter equal to that of the cylinder 1 but with tolerances, if necessary, such as to obtain a clearance that will enable sliding thereof in a fluid-tight way but without any direct contact against the inner walls of the inner surface of the cylinder 1 or of the cylinder liner, where present. Means (not illustrated) are provided for driving said disk 12 in the cylinder 1 so as to separate the exhaust gases from the fresh gases, i.e. , from the air and fuel mixture (in the case of the Otto cycle) or from the air alone (in the case of the Diesel cycle). An arrow F indicates, in all the figures, the position progressively assumed by the disk 12.

Displacement of the disk 12 can also be controlled via plungers connected thereto, having the shape of rods that come out of the cylinder head and traverse also the piston, if necessary, or traverse just the piston in the case where it is required to contain the overall dimensions of the engine. Alternatively, the disk 12 can be controlled via electromagnetic or hydraulic or pneumatic systems or systems of any other type, present within the engine block or in the proximity thereof or within the liner, if the latter is present. In the case of the rods having the function of plungers that drive the disk 12, these can be driven via cams (also desmodromic cams) or with any other system of a mechanical, hydraulic, pneumatic, or electromagnetic type or of some other type internal or external to the cylinder, without thereby limiting the scope of protection of the present patent and of the claims. For driving of the disk, whatever the system adopted, this must be such as to maintain, within itself and/or the engine system, the mechanical energy of the moving parts approximately constant, preserving it or transmitting it to other components in motion or converting it simultaneously during operation into some other form of energy, whether electromagnetic, pneumatic, hydraulic, or any other type envisaged by the system.

During the stroke within the cylinder, the fumes are pushed alternatively into the exhaust valve 1 1’ located in the cylinder head and into the 2’ on the opposite side of the cylinder close to the bottom dead centre. Simultaneously, on the other side of the disk 12, fresh gases are taken in (in what follows, by“fresh gases” we mean either the air in the case of an Otto cycle or the air and fuel in the case of a Diesel cycle) through the valve 1 1 and the duct 2 alternatively, prior to their combustion. Separation of the fumes from the fresh gases is thus obtained, enabling perfect flushing of the cylinder during operation of the engine.

In this way, an engine is obtained with an active phase where mechanical energy is delivered at output at each revolution of the crankshaft as occurs in traditional two-stroke engines but, as compared to the latter, with a higher efficiency approximately equal to that of a four-stroke engine having the same or similar dimensions, as compared to which it has approximately twice the power.

Comparing the case of a four-stroke engine of similar size and weight, with the present innovative solution, approximately twice the power is thus obtained.

Likewise, considering the same power, the main effect is a reduction (hence approximately a halving) of the weight of the engines, which would improve the acceleration performances of land transport means for people alone and also would enable reduction in consumption by virtue of the increase in efficiency and of the lower weight. In the case of means of transport for goods of any type, the main effect is an increase in carrying capacity equal to the saving in weight of the engine and of the fuel, this being due to the higher thermodynamic efficiency, given the same autonomy. These are the advantages deriving from adoption of the present engine.

In the case of air transport, the reduction in the absolute weight of the means, which is equal to the difference between the weight of the traditional engine and that of the engine according to the present invention, would enable an improvement in the characteristics of flight or, given the same characteristics, a larger number of passengers, in the case of aeroplanes for transport of people or a higher possibility of loading in the case of cargo planes. This result achieves, for engines typically adopted in the aeronautics sector (Otto-cycle four-stroke reciprocating engines supplied with aviation gasoline at least for medium-sized and small-sized aircrafts), approximately halving of the weight-to-power ratio, approaching the ratio (or even reaching it or exceeding it at least for small engines) of aeronautical gas turbines (whether of a jet or turboprop type), and hence constituting a valid substitute thereof also given the higher thermodynamic efficiency above all at regimes different from the design one. An effect of the higher efficiency is a greater autonomy in the case of passenger-transport aircraft or, conversely, given the same autonomy, is the possibility of a higher payload equal to the reduction in fuel transported in the tanks and storage systems.

For these characteristics, it is thus possible to install the engine according to the present invention, also functioning according to the Diesel cycle, as engine in the aeronautics sector, which, with a weight-to-power ratio similar to or lower than that of a gas turbine (at least for small aircraft), would obtain the simultaneous advantage of higher thermodynamic efficiency typical of the Diesel cycle (as compared to the Otto cycle and above all to the Joule-Brayton cycle of gas turbines and turboprops), and hence a greater autonomy or, given the same autonomy, a lower weight of the fuel carried and hence a higher payload.

In addition, the fuel of the diesel engine, given that it is a fuel oil (of mineral origin, vegetal origin, animal origin, of synthesis or of any other origin as chemical compound and/or mixture of fuel products and additives) of lower cost as compared to aviation gasoline of reciprocating engines or to kerosenes that are normally used in the aeronautics sector in gas turbines, in addition to being more readily available, would achieve also a further saving in cost and hence above all a greater economy of air transport, given that fuel is the most important cost item, which in the case of an increasing trend of prices would constitute a considerable advantage. In addition, the lower flammability of fuel oils entails a lower likelihood of fire and above all of explosion.

In the case of helicopters, the higher efficiency of reciprocating engines at all regimes as compared to gas turbines, for which the efficiency drastically drops to a minimum to depart from the normal operating design condition.

For this reason, in fact, during landing or take-off, the low power availability can cause malfunctioning, sometimes with disastrous consequences.

Given the above drawbacks typical of gas turbines, the system forming the subject of the present invention can thus provide, in the same way as the other internal-combustion engines, sufficient efficiency levels in a wide range of regimes (including those of take-off and landing) and with a weight-to-power ratio similar to that of gas turbines.

In the naval sector, following the same criterion, the saving in weight of the engine would result in an equal increase of the net payload (which, as is known, is determined by the presence of the load lines visible on the sides of the ships, and is a mandatory value established by international laws and imposed by the authorities and by the shipping registers for the maximum weight of the goods) and hence in a greater economy of transport of merchant vessels. In cruise liners or ferry boats, the saving in weight results in a greater volume available for the passengers, it being thus possible to increase the number of passengers transported, the other characteristics of the means remaining the same. In ships, in general, a greater lightness of the engine, and hence a smaller displacement, would enable an increase in the speed given the same installed power and/or a greater autonomy given the same net loading or a greater load or a greater space for containing the goods to be transported on board the ship, given the same amount of fuel taken on board for propulsion, and hence given the same gross carrying capacity.

Described in what follows, purely by way of non-limiting example, with reference to Figures 1 to 20, is an operating cycle of the engine according to the invention, where driving of the disk is not illustrated.

With reference to Figure 1 , the piston 3 is illustrated at the bottom dead centre and in the exhaust phase. Exhaust in this phase occurs through the top valves 11’ and also, if it is deemed appropriate, through the bottom valve 2’.

Next (Figure 2), the disk 12 rises at a rate much higher than that of the underlying piston 3 from which it separates, with inlet of the air (or of the air-fuel mixture) into the cylinder 1 in the area comprised between piston 3 and disk 12.

While in the part of the cylinder 1 above the disk 12 the burnt gases exit completely through the top exhaust valve 11’ that is open (Figures 2 and 3), rise of the disk 12 up to contact with the cylinder head and exhaust of the overlying fumes are completed.

Simultaneously, filling of the cylinder with fresh gases in the part below the disk occurs (Figures 3 and 4).

Albeit not shown in the drawings, it is highlighted that, in the case of closing of the bottom exhaust valve 2’, the disk can be stopped in a position corresponding to, and in the proximity of, the top part of the port of the intake duct 2 set in the bottom area just above the bottom dead centre (Figures 1 , 2, 19, and 20), thus obtaining a reduction of the down stroke.

The piston, rising, passes beyond the intake port (Figure 3) and compresses the fresh gases until it approaches (Figures 4 and 5) the top dead centre, in the proximity of which, in the case of the Otto cycle, spark-controlled ignition occurs or, in the case of the Diesel cycle, spontaneous ignition occurs following upon injection of fuel oil (Figures 5 and 6). There is to be considered the variability, according to the design and/or experimental results, of the position of the injectors (Diesel cycle, for enabling onset of spontaneous ignition) and of the spark plugs (Otto cycle, for controlled ignition), these possibly being located, in an appropriate number, either on the cylinder head or in the proximity of the latter, on the lateral surface of the cylinder.

Once the piston has reached the top dead centre, expansion starts given that the disk 12 rests against the cylinder head and is fixed with respect thereto (Figure 7).

Given that the disk remains stationary in contact with the cylinder head (Figures 8 and 9) and just the piston descends, when the latter approaches the bottom dead centre and with a certain advance, opening of the bottom exhaust valve occurs and in the time elapsing until the piston has reached the bottom dead centre, the disk 12 descends (Figure 10). Meanwhile, the top intake valve 11 opens, enabling, simultaneously with exhaust, intake of, i.e. , filling of the cylinder with, fresh gases for combustion.

Thus obtaining perfect flushing of the cylinder (Figure 12).

The replacement of gases present in the cylinder is completed with lowering of the disk until it comes into contact with the head of the piston (Figures 11 and 12), there having occurred complete intake in the space comprised between the top surface of the disk 12 and the cylinder head, and exhaust, this being concluded when the disk 12 reaches the bottom dead centre (Figure 12). In this phase, if it is deemed necessary (following upon calculation and experimental testing, taking into account the value of pressure in this phase) the exhaust valve will close immediately after or during passage of the disk. The first revolution of the engine shaft is thus completed, with a degree of approximation due to the advances and delays to be calculated theoretically and via experimental testing, with a useful phase (Figure 7 to Figure 12) of transfer of mechanical power to the engine shaft. In the next phases, the disk 12, remaining adherent to the cylinder head and rising fixedly with respect thereto (Figures 13 and 14), proceeds towards the top dead centre, in the proximity of which ignition of the supporter of combustion and of the fuel occurs in the area overlying the disk and piston and below of the cylinder head (Figures 15 and 16). Once the top dead centre is reached (Figure 17), there occurs expansion, i.e. , the active phase (with transfer of mechanical energy to the engine shaft), and descent of the piston and of the disk 12 once again fixedly joined together (Figures 18, 19, and 20) as far as the bottom dead centre, where again exhaust occurs (as in Figure 20 and in Figure 1 ), and then the cycle here described is repeated.

In this latter phase, the disk 12 will reach the bottom dead centre, and the bottom exhaust valve set at the duct 2’ may be open or closed, according to the experimental tests and/or calculations enabling, as already highlighted above, a shorter stroke of the disk which may stop at the top edge of the bottom intake duct, exhaust completely occurring from the top valve alone.

In any case, upon reaching the bottom dead centre, taking into account any necessary advances or delays with respect thereto, the bottom intake valve opens completely for intake of the fresh gases, which occurs in the area comprised between the disk that is rising and the top surface of the piston positioned in the proximity of b.d.c., the cylinder thus filling with fresh gases, which are then compressed by the piston, as the latter goes up the cylinder. The pressure of incoming air (Figures 1 , 2, 3, 4), both in the case of naturally aspirated engines and in the case of supercharged engines, is not such as to represent mechanical work, if not to a negligible extent, performed by the separating disk 12.

The above cycle has been completed with two revolutions of the engine shaft, for each of which the active phase (see Figures 8 to 12 for the first revolution and Figures from 17 to 20 and 1 for the second) occurs while the piston is in the descending stroke with yielding of mechanical energy, i.e., work, at output, which, by convention, is positive.

It is hence pointed out that the advantage achieved is an active phase at each revolution as occurs in a two-stroke engine, while the drawback of the latter that causes lowering of efficiency is eliminated, namely, defective flushing (which is the only reason for non-generalized adoption of such engines), i.e. , mixing of the combustion residue of the previous cycle with the fresh gases for combustion in the cycle in progress, part of which are moreover unnecessarily discharged unburnt into the atmosphere.

With the present system disclosed herein, perfect flushing is hence obtained via the disk 12, in a way at least equal to what is obtained with the idle stroke in a four- stroke engine.

Finally, given the absence of contact (or low forces and hence low friction) of the disk 12 against the wall of the cylinder, the motion (unlike the idle motion in a four- stroke engine) does not present any friction, if not negligible, between solid surfaces, and, since moreover the air at inlet is not, to a first approximation, either taken in or compressed by the disk 12, no hydraulic and/or hydrostatic resistances are set up, except to a limited extent, the motion of the disk 12 being the same as that of the fresh and burnt gases that it separates.

It is pointed out that the system can be adopted both with naturally aspirated engines and with supercharged or turbosupercharged engines.

The example provided schematically herein may undergo numerous variations and modifications, as well as particularizations, whatever the implementation, all of which are in any case included in what is described herein and in any item that can be obtained or built without departing from the claims provided in what follows. The materials that can be used, appropriately chosen, do not represent a limit to the present description of the invention. The drawings, with the proportions and dimensions represented, along with the corresponding notes and references, are functional for the purposes of description and of an understanding of the underlying idea and do not represent a limit to the scope of the invention described herein.

The present system supplies a power that is approximately twice as that of a four-stroke engine of the same size and cubic capacity having approximately the same efficiency. It is hence similar to a two-stroke system, with the advantage that no mixing of the exhaust gases with the fresh gases of the next cycle occurs, which is the cause, in two-stroke engines, of a reduction in thermal efficiency to the point of reducing the theoretical power thereof, which, from being approximately twice that of a four-stroke engine of the same size, drops to an effective value of approximately one and a half times.

The system illustrated herein entails a power that is approximately twice that of a four-stroke engine of the same size, cubic capacity, and weight.

Hence, conversely, given the same power, the weight of the engine is reduced to approximately half the weight of a four-stroke engine with similar dimensions, the efficiency remaining approximately unvaried. The adoption of the engine according to the invention would be useful for aircraft and ships, the loading capacity of which would increase by an amount equal to the difference in weight of the two engines thus obtained, the autonomy remaining approximately unvaried given the same fuel storage volume.

Positioning of the injectors and of the spark plugs (which is not, on the other hand, indicated in the drawings) may also be lateral in the combustion chamber to allow for the presence of the disk when this is stationary in the top position of the cylinder. In the case of multicylinder engines, the system for moving the separator will be common to the various cylinders with distribution of the motion to the various disks. The total energy present in the driving system of the disk will be approximately constant whatever the system or combination of systems adopted: mechanical, with cams also of a desmodromic type, hydraulic, pneumatic, electromagnetic, or any other system.

As regards the valves, in addition to the head valves, those at the base of the cylinder will be present, one for exhaust 10’ and the other for intake 10, only if it is deemed necessary according to the calculations and experimental tests carried out, it being possible to omit any of the two or both on the basis of the pressures, the motion of the gases, the relative position, and the shapes of the ports and/or ducts (2 and 2’).

During rise of the disk 12, the bottom intake valve will open when on the top face of the disk 12 the exhaust gases pushed in the top exhaust valve are present (the disk 12, as already mentioned above, may, in this phase, present a shorter stroke as compared to the maximum stroke and, as far as the top point of the bottom intake duct, may separate itself from the piston - up to that moment, it was, in fact, adherent thereto during descent - see Figures 1 , 2, 3, 4 -, which proceeds as far as the bottom dead centre, the bottom exhaust valve, if present, being closed).

At the end of the expansion phase performed by the piston (Figure 10), the bottom exhaust valve (if present) will be completely open until the cylinder is completely emptied by the disk 12 (Figures 11 and 12), and immediately closes after passage of the disk 12 (Figure 12). Flowever, in the case of absence of the valve, exhaust can occur in a complete way, it being envisaged beforehand in the design stage (via calculation of the position and shape of the duct and of the fluid-dynamics of the gases) and being finally verified experimentally. In this phase (Figure 12 and 13) the disk 12 and piston will move fixedly together traversing the cylinder in a phase of compression like that of a normal four-stroke engine (Figures 13, 14, 15, 16). Once the disk 12 and piston, always fixed with respect to one another, have reached the top dead centre, there will be an expansion phase equal to that of a normal four-stroke engine, in the proximity of the bottom dead centre there occurring exhaust through the top valve 11’ alone or through the two valves 11’ and 2’ (if the latter is present) (see Figures 1 and 20) according to the design choice. Likewise (Figures 10, 11 , and 12), the bottom intake valve 10, if present (the above considerations made for the exhaust valve 10’ applying also to the valve 10), may be open or closed, according to the design choice, calculation, and experimental tests conducted. The relative vertical position of the bottom intake and exhaust ports may be also different from the one illustrated in the drawings, to be established via calculation and experimental tests and according to the thermodynamic efficiency, as likewise the dimensions and shapes of the bottom intake and exhaust ports. The valves (if present) of the bottom ports may be of any type, taking into account the not excessive pressure in the bottom part of the cylinder.

As mentioned above, the bottom valves, whether any of the two or both, may even not be present (and in the case of opening of the valve represented in Figure 1 , backflow of the exhaust gases or outflow of the fresh gases may be prevented or rendered negligible via an appropriate shape of the ducts and positioning of the intake and/or exhaust ports), the backflow of exhaust gases possibly being negligible or zero in the phase of rise of the disk 12 (Figure 2), the latter moving upwards and taking in just fresh gases, considering the energy of the fumes at outlet from the exhaust duct and with an appropriate positioning of the intake duct, by imposing a shorter stroke on the disk 12, which in this phase (Figure 2) might not reach the bottom dead centre, stopping at the top limit of the intake port 2. It is pointed out that the drawings provided for reference have only the purpose of enabling an understanding of the present invention, are not in scale, and are not significant either as regards the dimensions or as regards the proportions between the parts and mutual positions of the components.

As regards the injectors (in the case of the Diesel cycle), they will be positioned so as to be able to function even in presence of the disk 12, and hence they may be located in the lateral and top part of the cylinder and provided in a suitable number. Alternatively, they may be positioned at the head with a small aperture in the disk 12 that enables just outlet of the diesel oil when it is injected and, in any case, has a size such as not to allow passage of gases through it if not to a negligible extent.

As regards the spark plugs (in the case of the Otto cycle), they will be arranged so as to be able to function also in the presence of the disk, and hence in the lateral part of the cylinders close to the head or directly through the disk 12 if deemed necessary and possible and they will be provided in a number such as to guarantee perfect ignition.