WO2007080619A2

WO2007080619A2 - Rotary valve internal combustion engine with seal and valve register arrangement

Info

Publication number: WO2007080619A2
Application number: PCT/IT2007/000013
Authority: WO
Inventors: Vito Consoloni; Kurt Valentinitsch
Original assignee: Vito Consoloni; Kurt Valentinitsch
Priority date: 2006-01-09
Filing date: 2007-01-08
Publication date: 2007-07-19
Also published as: WO2007080619A3

Abstract

An internal combustion engine with having a combustion chamber made inside the rotary valve. To s'ald combustion chamber opens a seat, axially ma'de in the top part of the rotary valve, apt to house a spark plug, or injector. The hollow cavity of the head apt to house the rotary valve provides circular grooves, coaxial to the cylinder, and housing elastic rings pressed by their elastic force on the external surface of the rotary valve. Further grooves for straight seals are made in the head around the apertures of the induction and exhaust pipes.

Description

ROTARY VALVE INTERNAL COMBUSTION ENGINE WITH SEAL AND

VALVE REGISTER ARRANGEMENT

Field of the Invention

The present invention relates to an internal combustion engine which runs on petrol or diesel fuel.

In particular the invention relates to an internal combustion engine with rotating valves coaxial to the cylinders of the engine.

Background of the Invention

As known, in reciprocating internal combustion engines, Ihe engine timing is made by a set of apertures, and relating shutters and shutter actuators, dedicated to let each cylinder communicate with the fuel supply devices or the exhaust line. Two-stroke engines are usually fed in a very simple way, using inlet and exhaust ports directly cut in the cylinder, in correspondence to the piston bottom dead center the piston itself acting as a shutter of the ports, whereas for four-stroke engines have been developed various solutions avoiding, among the other, any overlapping of the different strokes of the process, overlapping that unfortunately in two-stroke engines is inevitable and it is tolerated because of the simplicity of the previously mentioned arrangement; it causes, as you know, a high specific fuel consumption and noxious emissions of unburnt hydrocarbon from the exhaust pipe. Among the various evaluated engine timing systems for four-stroke engines, the one generally utilized in mass production comprises overhead disk valves apt to open and close the inlet and exhaust ports cut in the cylinder; the induction and discharge processes are in fact performed in correspondence to the top dead center so, unlike two-stroke engines, the valves are always placed overhead either directly on top of the cylinder or in a protrusion of the head beside the cylinder. In both cases there is a relevant mechanical stress because of the collisions of the valve with its seat and of the valve tappet with the valve stem; this is due to the gap in the operating mechanism required to assure the sealing when the valve is closed. A further disadvantage relating to this kind of timing system descends from the intricacy of the valves actuating mechanism; intricacy which raises with the speed rate and performances required to the engine.

Different engine timing systems, tested and still used on particularly advanced engines, provide sleeves, inserted in the cylinder, apt to close and open ports made in the upper part of the cylinder itself. Due to the asymmetry of the induction and discharge strokes with respect to a given angular position of the crankshaft, two concentric sleeves are needed, which moves in turns, properly shifted, or a single sleeve having rotating and translation motions. It descends, then, a certain complexity of the cylinder and of the mechanism actuating the sleeve, or sleeves.

Furthermore, it is difficult to deal with the lubricating and cooling requirements, so that specific solutions are designed and adopted for the different applications. For the above reasons, this kind of engine timing, which undoubtedly has advantages as regards reliability and performances, avoiding in the mass production the collisions that occur between the valve and its seat, is nevertheless suitable only for such applications where the production costs are of a minor relevance.

Further engine timing systems provide rotary valves, placed on the cylinder, coaxially or in a perpendicular direction. Such systems, which have, with respect to the standard overhead valve distribution, the same advantages of the sleeve distribution and which, with respect to these last, have fewer mass production costs, have not been put into practice since now, mainly in view of the low reliability of the proposed solutions due to lubricating problems and to the low efficiency of the combustion chamber. An example of such solutions is disclosed in US patent US4033317 which is, in time order, the last of a series of patent applications filed by an applicant relating to an engine in which the engine timing is obtained through a rotary valve coaxial to the cylinder; patent applications in which are disclosed various solutions relating to the shape of said valve, in particular the position and number of induction and exhaust ports and the shape of the combustion chamber that is often deeply asymmetric.

The above said US patent provides a special shape both of the ports of the rotary valve and of the upper part of the piston, in order to generate, when it gets its top dead center, two separate combustion chambers; the consequence is a clear intricacy of the layout, raising costs and overheating of the piston.

Considering, however, the undoubted possible advantages of this kind of engine timing system with respect to the present, widely spread, overhead valve distribution, it can be understood the opportunity to seek and propose valid solutions to the above shown matters regarding the efficiency and the lubrication of the combustion chamber. Summary of the Invention

The main object of the present invention is to provide an internal combustion engine in which the timing system provides a rotary valve coaxial to the cylinder, said engine having a highly functional and efficient combustion chamber as regards output power and consumption.

Further object of the present invention is to provide an internal combustion engine in which the timing system provides a rotary valve coaxial to the cylinder, said engine having a lubricating-cooling fluid seal assembly arrangement through which is deeply increased the seal of this kind of engines making it similar, in efficiency, to the one of the widespread overhead disk valve engines. Another object of the invention is to provide an internal combustion engine in which the timing system, providing a rotary valve coaxial to the cylinder, is designed to easily replace the present overhead disk valve timing systems.

Said objects are attained by an internal combustion engine, in particular a four- stroke engine, in which at least one cylinder houses a reciprocating piston, characterized in that it comprises, coupled to said cylinder, at least one rotary valve whose axis of rotation corresponds to the axis of said cylinder, said rotary valve providing at least one port apt to put into communication the induction and exhaust pipes of the head with a combustion chamber obtained in said rotary valve, said combustion chamber communicating with a seat made along the axis of the rotary valve apt to house the sparking plug, in case of engines running on petrol fuel, or an injector in case of diesel engines. Said at least one port of the rotary valve tangentially enters the combustion chamber.

Both the rotary valves and the relating actuating components and the induction and exhaust pipes are housed in the head of the engine.

The induction pipes are preferably arranged according to directions leading to a peripheral zone of the combustion chamber.

The number of induction and exhaust pipes changes according to the desired speed range of the rotary valve; as a consequence changes the number of ports made in the rotary valve.

Said engine provides a lubricating-cooling fluid seal assembly comprising, made in the hollow cavity of the head which houses the rotary valve, circular grooves, coaxial to the cylinder, housing metallic elastic rings pressed by their elastic force on said rotary valve, said grooves being arranged over and under the apertures of the induction and exhaust pipes.

Further seats for relating straight seals are provided, still in the head, around the lateral walls of the apertures of the induction and exhaust pipes, so that the aperture of each induction or exhaust valve is sealed at each side by sealing elements.

Seats for further elastic rings coaxial to the cylinder are provided at the end sections of the hollow cavity housing the rotary valve in order to avoid compression decreasing and also to avoid leakage of lubricating-cooling fluid towards the cylinder and the upper part of the head.

The elastic rings have a gap apt to give it the elastic properties needed to assembly them and to let them work properly, said gap being designed so that, even in a partially stretched configuration, which is the standard work configuration, the ends of one side of the gap partially overlap the ends of the other side.

The dowel pins of the elastic rings, one per ring, are integral to the head and are advantageously disposed at different angular positions.

Both the elastic rings and the straight seals are coated with silicium carbide. material also coating the external surface of the rotary valve as it grants, in addition to a very high hardness also good self-lubricating qualities.

The rotary valve is put into rotation by transmission means connected, with a specific transmission ratio, to the crankshaft.

Advantageously the engine comprises a bush apt to adjust the relative position of the rotary valve with respect to the cylinder, said bush, coaxial to the valve, being placed between the upper part of the valve itself and the upper part of the hollow cavity of the head to which the bush is connected by thread means through which is performed said adjustment.

A lubricating fluid is conveyed towards the friction surfaces between said valve, said bush and said transmission means, thanks to a circulation line comprising a tank obtained in said head, at least one duct connecting said tank with the lower section of said bush and helicoidal grooves made in correspondence to the section of the external surface of the rotary valve where is housed the bush, said helicoidal grooves being apt to pump the lubricating fluid towards the top of the rotary valve thanks to the revolving movement of the valve itself.

The shape of the induction pipes and the shape of the ports of the rotary valve are designed and optimised to be suitable to the specific application in order to obtain the highest efficiency for filling the combustion chamber.

The advantages that may come with the internal combustion engine of the invention are clear, relating to the deep functionality of the timing system and the easy manufacturing and assembling operations of the whole engine coming with the adoption of the above timing system.

The specific shape of the combustion chamber and of the ports of the rotary valve provide a very efficient combustion, from which descends a higher power at the same cylinder capacity and reduction of consumption.

The head of the engine according to the invention can easily replace the head of the standard overhead valve engines having the same dimensions and arrangement of the cylinders.

The sealing system is especially efficient thanks to the specific solutions provided to grant the lubricant-proof seal in the concerned areas of the engine. Moreover, said sealing systems has a long time reliability thanks to the union of a very simple layout and the use of materials having performances that fit the scope.

Brief Description of the Drawings

For a better understanding of the characteristics and the advantages of the present invention, some embodiments will now be described by way of examples with reference to the accompanying drawings, in which:

- figure 1 shows a sketched section view of a portion of an internal combustion engine according to the invention;

- figure 2 shows a sketched top view relating to a component of the engine of fig.l;

- figure 3 shows a group of the engine of the invention, according to a different embodiment;

- figures 4 and 5 respectively show a section side view and a top view of a specific component of the engine of the invention; - figures 6 and 7 show to views similar to the views of fig.4 and fig.5, but relating to a different embodiment of the same component of the engine;

- figure 8 a section view of a part of the head of the engine of fig.1 ;

- figure 9 shows a detail of a section view obtained by the section plane IX-IX offig.8; - figure 10 shows a top view of a component of the engine of the invention;

- figures 11 and 12 show section views of the component of fig.10 respectively obtained by the section plane XI-XI and XH-XII of fig.10.

- figures 13 shows a top view of the component of fig.10 in a specific work configuration; - figure 14 shows a section view of the component of fig.13 obtained by the section plane XIV-XIV of fig.13;

- figure 15 shows a sketched view, analogue to the view of fig.1, of a different embodiment of the engine of the invention;

- figure 16 shows a top view of a component of the engine of fig.15. Description of Preferred Embodiments

Referring to fig.l is shown as a whole with 10 a portion of an internal combustion engine relating to a cylinder, 11, its piston 12, and the portion of the head, 13, relating to said cylinder. In the head, 13, there are conduits, 14, of the cooling circuit, as well as the induction pipes, 15, 16, of the fuel mixture entering the combustion chamber, 18. This last is provided in a rotary valve, 19, having a substantially truncated-conic shape, housed in the head, 13, in correspondence to the cylinder, 11, the axis of rotation of said valve 19 corresponding to the axis of said cylinder, and the maximum diameter of the seat of the valve being equal to the internal diameter of the cylinder. The rotary valve 19 provides, in this embodiment, two ports, 20, 21, apt to put into communication the combustion chamber 18 with, in turns, the induction pipes, 15, 16, and the exhaust pipes, 22, 23, sketched in fϊg.2. The top part of the rotary valve is connected, by screw means, 24, to a gear wheel, 25, rotating coaxial to the valve itself. Said gear wheel 25 gear with a second gear wheel, 26, keyed to a shaft, 27, perpendicular to the valve 19. To said shaft 27 is also keyed a further gear, 28, intended to transmit the torque to said shaft 27, from the crankshaft, not shown in figure, according to a specific transmission ratio. The transmission to said gear 28 is preferably made by a V- shaped belt, but it can be also made by a set of gears or other transmission means. The gear wheel 25 provides a central hollow hub, 29, through which is entered and partially houses the sparking plug, 30, shown in fig.l, or the injector, 31, shown in the embodiment of fig.3. You have to notice that the sparking plug, 30, or the injector, 31, are housed in a seat, 32, obtained in the rotary valve 19, exactly along its central axis, so that the ignition spark, or the injection of fuel, take place exactly in the central top part of the combustion chamber 18; the electric power supply, or the fuel supply, coming thanks to revolving collectors of the known art. The exact position and alignment of the gear wheel 25, and of the valve 29, with respect to the head 13, are assured by geometrically binding, freely revolving, the end section of said wheel's hub opposite to the end connected to the valve 19. The bond is obtained thanks to a sleeve, 40, providing a thread on its external surface which couples with a bush, 33, apt to axially set the position of the sleeve with respect to a crossbar, 34, integral to the external part, 38, of the head 13, by screw bars, 39. Between said sleeve 40 and the hub 29 of the gear wheel is housed a set of radial and thrust bearings.

As you can see in fϊg.2, the induction pipes, 15, 16, are obtained in the head according to directions which let them enter the combustion chamber 18 in a peripheral zone; the combustion chamber is comprised inside the dot line 36. Also the ports, 20, 21, of the rotary valve are cut to enter the same peripheral zone of the chamber 18.

Thanks to such arrangement of the induction pipes and the ports, is obtained, inside the combustion chamber, a high and uniform filling, because of the generation of a whirling flow of the fuel mixture inside the combustion chamber. Also the shape of the pipes and ports is useful to obtain an increased efficiency of the combustion process. In particular are shown, in figg. 4 and 6, two possible embodiments of the rotary valve in which the shape of the ports 20, 21, is not trapezoidal like in fig.1 and fig.3. Port 20"', shown in fig.4, has rectangular transversal section, whereas port 20" shown in fig.6 has a semi-elliptic shape.

Furthermore, you must note that, in a different way from the truncated-conic shape of the rotary valve 19 shown in figg.l and 3, in the embodiment of fig.4 it has a higher cylindrical external zone, whereas in the embodiment of fig.6, the external shape of the part of the valve comprising the combustion chamber is hemispheric.

The lubricating-cooUng fluid sealing system, well shown in fig.8, provides, in the hollow cavity, 42, of the head 42 apt to house the rotary valve 19, circular grooves, 43, 44, 45, 46, coaxial to the cylinder, 11, in which are housed elastic rings, 47, better shown in figg. from 10 to 14. Two of said circular grooves, 43, 44, are placed close to the apertures of the induction pipe, 15, and the exhaust pipe, 22 ,and precisely, with reference to the direction of the compression stroke of the piston, 12, of the cylinder, 11, respectively before and behind said apertures. Further grooves placed along the lateral sides of the apertures of pipes 15 and 22, are seats, 48, for straight seals, 49.

Said seats, 48 and the relating straight seals, 49, are as long as to extent parallel to the pipe 15 or 22 they seal, and they cross the grooves 43, 44, in which are the rings, 47. As you can see in the detail of fig.9, said seals, 49, provides, just in correspondence to the section which crosses grooves 43, 44, cuts apt to house said elastic rings, 47, that, in this way, firmly fasten the seals in their seats, 49. The elastic rings, 47, as you can see in figg.lO and 11, provide a gap, 50, shaped in a Greek key, so that the end 51 of a first side of the gap lays between the ends, 52, of the other side of the gap itself. In this way, as you can notice in figg. 13 and 14 also in a partially stretched configuration of the ring, that is the standard work configuration, the opposite ands, 51 and 52, remain partially overlapped, so avoiding leakage of fluid from the top to the bottom side of the ring, 47. In a diametrally opposite direction with respect to the gap, 50, there is a semicircular cut, 53, apt to set the position for fitting a dowel pin, of known art, in the head, 13, in each of the grooves, 43, 44, 45, 46, to avoid the rotation of the ring, 47, which could happens as a consequence of the friction with the rotary valve during its revolving movement.

Said elastic, 47, has, in the present embodiment, a trapezoid section, in which the external surface, 54, is cylindrical, the internal surface, 55 is sloped according to the slope of the valve, 19, and the top and bottom surfaces, 56, are perpendicular to the axis, 57 of the cylinder, 11. The sealing is assured because when the valve 19 is assembled, it causes the rings, 47, to elongate, so that their elastic force keeps the surface 55 pressed against the external surface of the rotary valve, 19. You have to notice that also in the stretched configuration the ends 51 and 52 of the gap 50, remain partially overlapped, so avoiding possible leakage of lubricating fluid or compression, in the zone comprising the gap 50 itself.

The dowel pins are placed, one per groove 43, 44, 45, 46, in different angular positions, in order to reduce the risk of leakage of lubricant across the thin zones 53 of the rings suitable to set the fitting of the pins. In this specific embodiment, in which four rings, 47, are provided, said dowel pins are positioned at 90° one from the other.

Finally, is particularly advantageous the use of silicium carbide as a coating material of the rings, 47, and the seals, 49, as the properties of said material help improve the lubrication between rotary valve and head, and increase the life and the reliability of the above sealing components. In fact, it is a self-lubricating material with a tremendous hardness, which grants the maximum performances under both aspects of lubrication and working life.

The same material is also used for coating the external surface of the rotary valve, 19, in order to improve the lubrication, and, most important, the hardness and then working life of the valve, which, rotating inside the head, is subjected to friction against the rings, 47, which could cause an early wear. The rotary valve engine according to the invention works as described in the followings. According to the number of pipes in the head, and the number of ports of the valve, the work process is equivalent to the one the standard four-stroke engines provided with one or more couples of overhead valves for each cylinder. In the case, for instance, that the rotary valve has just one port and the head has just two pipes, one for induction, one for exhaust gas, the work process is the same of a standard four-stroke engine with two valves per cylinder; one thermodynamic cycle corresponds to one revolution of the rotary valve, during which you have the two crankshaft's revolutions needed to perform the four strokes of the pistons respectively intended for aspiration, compression, combustion and discharge. So, the port of the rotary valve, during one revolution, gets in front of the induction pipe at the beginning of the thermodynamic cycle and in front of the exhaust pipe at the end of the thermodynamic cycle. The torque transmission from the crankshaft to the rotary valve has a ratio of 2 to 1. In the case of the shown embodiments, where there are n.2 ports and n.4 pipes, the work process corresponds to the one of a standard four-stroke engine with four overhead valves per cylinder, two for induction and two for discharge.

The arrangement shown in fig.2 refers to the induction stroke during which the air or fuel mixture enters simultaneously from two opposite zones of the combustion chamber, producing the effective filling above disclosed. You have to notice that after a rotation of 180° of the rotary valve is repeated an identical induction configuration, relating to the following thermodynamic cycle; so, for each complete revolution of the rotary valve the crankshaft performs four revolutions, needed to perform two thermodynamic cycles. Therefore, the torque transmission from the crankshaft to the rotary valve has a ratio of 2 to 1. Obviously, further schemes and arrangements can be provided to obtain the work processes of different standard four-stroke engines, as regards number of pipes and valve per cylinder.

For instance, providing four ports in the rotary valve, uniformly spaced, and the transmission ratio between the crankshaft and rotary valve is set to 8 to 1, you have the work process of a four-stroke engine with two overhead valves per cylinder if there are two pipes in the head, whereas you have the work process of a four-stroke engine with four overhead valves per cylinder if there are four pipes in the head.

You must consider that a limitation of the possible arrangements may come from the size of the cylinder, and the relating rotary valve, in which could not be opened suitable ports beyond a certain number.

Anyway, for each possible solution, the advantages concerning the simple structure of rotary valves engines are obtained and, in addiction, the specific advantages of the present invention, coming from the peculiar layout of the rotary valve comprising the sparking plug or the injector, and the particular shape and arrangement of the ports and the induction and exhaust pipes; advantages that concerns both the high efficiency of the combustion process and the reduction of consumption.

Obviously the above advantages keep safe also in presence of modification and changes to what above disclosed. May certainly vary the scheme of the transmission from the crankshaft to the rotary valve, that could provide a conical gear in correspondence to the valve, as in the shown embodiments, or in correspondence to the crankshaft, by V-shaped belt or chain. The axial adjustment of the rotary valve 19 with respect to the head 13 may be different. In particular, a very advantageous adjustment system is shown in the embodiment of figg.15 and 16. In the top part of the head 13' is obtained, coaxial to the hollow cavity 42, a seat for a bush 58, connected to the head 13' by a threads 59 made in the external surface of the bush 58 and its seat in the head. The top external part of the rotary valve is housed not directly in the cavity 42 of the head 13' but in the bush 58 which then act as a friction bearing. The top surface of the valve, like in the embodiment of fig. I₅ is bound to a gear wheel 25' by screw means 24'. Said gear wheel, in this embodiment, is a component of a transmission set, not shown in figure, that provides a conical gear in correspondence to the crankshaft. In this way the overall height of the gear wheel can be reduced, whose bottom surface, in addiction to being bound to the rotary valve 19', directly mates the top surface of the bush 58. With such arrangement the axial position of the rotary valve is adjusted by change the axial position of the bush 58, that is screwing it up or down by the threads 59. To exactly settle to axial movement of the bush 58 and then the movement of the valve 19' and of the gear wheel 25', with respect to the head 13', in the top surface of the bush 58 are made twenty through holes, 60, at the same angular distance, apt to align, thanks to a cylindrical pin, 61, with three holes, 62, made in the head 13', at an angular distance of 120° one from the other; it is therefore obtained the chance to perform the above said adjustment with distances of one sixtieth of the thread's 59 pitch. To avoid damage or wear to the components subjected to friction, that is the coupling zone 63 between the bush 58 and the corresponding external surface of the rotary valve 19', and the mating area, 64, between the top surface of the bush 58 and the gear wheel 25', a simple and effective auxiliary lubricating system is provided. The system comprises an annular tank, 65, made in the top part of the head 13', and a pipe, 66, feeding the lubricating-cooling fluid to the lower side part of the bush 58, which has a hole, 67, that let the fluid enter the coupling zone between the bush 58 and the rotary valve 19' which provides, on its external surface, helicoidal grooves, 68, apt to pump the fluid upwards with a certain pressure thanks to the revolving movement of the valve itself. It is so obtained a good lubrication both of the coupling zone 63 and of the mating area 64. The lubricant, in fact, once reached the top of the rotary valve cannot flows into the cavity of the central hub 29' because of the presence of labyrinth seals, 69, so it must cross the mating area 64 and pour out again in the tank 65. A cap, 70, and oil baffles, 71, avoid discharge of lubricant outside the engine 10'. You have to consider that the ring 47' placed in correspondence to the top end of the rotary valve is, in this case, housed in a seat made in the bush 58. The clear advantage of the above disclosed embodiments consists in that possible leakage of lubricant through said ring 47' are not noxious thanks to the presence of the auxiliary lubricating system for lubrication of the coupling zone 63 and of the mating area 64.

Further visible advantage is the reduced overall height of the above solution. Further and advantageous changes may concern the exhaust pipes, which could be arranged tangential to the combustion chamber, instead of in a radial direction like in the disclosed embodiments. The combustion chamber may be shaped in a different way with respect to the hemispheric shape shown in the appended figures.

The engine preferably has in-line cylinder, but it may comprise a single cylinder, or several cylinders in parallel sets. The global arrangement and the number of sealing elements may change, fitting the requirements of specific applications, relating, for instance, to the shape of the external surface of the rotary valve 19, 19', 19", 19'", or to a different shape or number induction pipes, 15, 16 and exhaust pipes, 22, 23. The seals 49 may differ in length and shape, and they could not have the cuts apt to house the rings 47 because could be unnecessary their fastening action, thanks to the presence of different fastening means or to the fastening action due to the interference between the seals and their seats, 48.

The elastic rings, 47, 47', could have a different shape of their section, the only requirements remaining the fact that the surface 55 properly mates the external surface of the rotary valve, 19, 19', 19", 19'", in order to assure the sealing. The gap, 50, of the rings 47, 47', could be differently shaped, hi particular, keeping the Greek key shape, a greater number of ends 51 and 52 could be provided, as a function of the available space, or the Greek key shape could be made in the direction perpendicular to the one of the embodiment. Nevertheless, said gap, 50, could also be cut according to different shapes for a simpler structure, and in particular the dowel pin could be fitted in correspondence to the gap.

These ones and more changes may be carried out to the above disclosed internal combustion engine, always remaining in the ambit of protection of the following claims.

Claims

C L A I M S

1- Rotary valve internal combustion engine, in which at least one cylinder houses a reciprocating piston, characterized in that it comprises, coupled to said cylinder, at least one rotary valve whose axis of rotation corresponds to the axis of said cylinder, said rotary valve providing at least one port apt to put into communication the induction and exhaust pipes of the head with a combustion chamber obtained in said rotary valve, said combustion chamber communicating with a seat made along the axis of the rotary valve apt to house the sparking plug, in case of engines running on petrol fuel, or an injector in case of diesel engines.

2- Internal combustion engine according to the previous claim characterized in that said at least one port (20) tangentially enters the combustion chamber (18).

3- Internal combustion engine according to claim 1 or 2 characterized in that the said combustion chamber (18) communicates with said seat (32) made along the axis of rotation of the rotary valve (19) so that the ignition spark, by said sparking plug (30) in case of petrol engines, or the injection of fuel, by said injector (31) in case of diesel engines, take place in the central top part of the combustion chamber (18). 4- Internal combustion engine according to claim 1, 2 or 3 characterized in that at least one induction pipe of said head (13) is arranged in a way to lead to a peripheral zone of the combustion chamber (18). 5- Internal combustion engine according to the previous claim characterized in that said rotary valve (19) provides two ports (20, 21) apt to put into communication the combustion chamber (18) with, in turns, induction pipes (15, 16) and exhaust pipes (22, 23) of the head (13).

6- Internal combustion engine according to one of the previous claims characterized in that said combustion chamber (18) has a substantially hemispheric shape. 7- Internal combustion engine according to one of the previous claims characterized in that said rotary valve (19) is put into rotation by transmission means connected, with a specific transmission ratio, to the crankshaft

8- Internal combustion engine according to the previous claim characterized in that said rotary valve (19) is bound at its top end, by screw means (24), or equivalent means, to a gear wheel (25) rotating coaxial to said rotary valve.

9- Internal combustion engine according to the previous claim characterized in that said gear wheel (25) comprises a central hollow hub (29) through which is entered and that partially houses said sparking plug (30) or said injector (31).

10- Internal combustion engine according to one of the previous claims characterized in that said at least one port of said rotary valve has a substantially trapezoidal shape.

11- Internal combustion engine according to one of the previous claims characterized in that said rotary valve (19) has a substantially truncated- conical shape and is housed in a hollow cavity of said head (13) whose maximum diameter is equal to the internal diameter of the cylinder (11). 12- Internal combustion engine according to one of the previous claims characterized in that it comprises, made in the hollow cavity (42) of said head (13) housing said rotary valve (19), circular grooves (43, 44, 45, 46), coaxial to the cylinder (11), in which are housed elastic rings (47) pressed by their elastic force on said rotary valve (19).

13- Internal combustion engine according to the previous claim characterized in that it comprises, made in said hollow cavity (42) of the head (13), seats (48) for relating straight seals (49), said seals being arranged around the lateral walls of said apertures of the induction and exhaust pipes (15, 16, 22, 23).

14- Internal combustion engine according to the previous claim characterized in that said straight seals (49) have a cut through which pass the elastic rings (47) to assure a firm fastening of said seals (49) in their seats (48). 15- Internal combustion engine according to the claim 11, 12 or 13 characterized in that the gap (50) of the elastic rings (47), apt to give them the elastic properties they need to fit the grooves (43, 44, 45, 46), is shaped in a way that, even when the ring is partially stretched, that is the standard ring's work configuration, the ends (51) of one side of the gap (50) remain partially overlapping the ends (52) of the other side of the gap.

16- Internal combustion engine according to one of the claims from 11 to 14 characterized in that said elastic rings (47) and said straight seals (49) have a silicium carbide coating.

17- Internal combustion engine according to one of the claims from 11 to 14 characterized in that the dowel pins of the elastic rings (47) are fitted in the respective grooves (43, 44, 45, 46) at different angular positions.

18- Internal combustion engine according to one of the previous claims characterized in that the external surface of said rotary valve (19) has a silicium carbide coating. 19- Internal combustion engine according to one of the previous claims characterized in that it comprises a bush (58) for adjusting the height of said rotary valve (19') with respect to the cylinder (11), said bush (58), coaxial to said rotary valve (19'), being mounted between the upper section of the valve (19') and the hollow cavity (42) of the head (13'), to which the bush is connected by threads (59) useful to perform the above said adjustment.

20- Internal combustion engine according to the previous claim characterized in that the bottom surface of said gear wheel (25') mates, and is kept pressed against, the top surface of said bush (58). 21- Internal combustion engine according to claim 18 or 19 characterized in that it provides an auxiliary lubricating circuit feeding a lubricating fluid towards the coupling zone (63) and the mating area (54) between said rotary valve (19'), said bush (58) and said gear wheel (25'), said circuit comprising a tank (65) made in said head (13'), at least one duct (66, 67) connecting said tank (65) with the lower section of said bush (58)m and helicoidal grooves

(6S) cut in correspondence to the external surface of the rotary valve (19') where is housed the bush (58), said grooves (68) being apt to pump the lubricating fluid towards the top of the rotary valve (19') thanks to the revolving movement of the valve itself. 22- Internal combustion engine according to claim 11 or followings characterized in that at least one of said circular grooves (43, 44, 45, 46) is made in the internal lower section of said bush (58).