WO1991010046A1

WO1991010046A1 - Cylindre head for reciprocating endothermic engines provided with at least one valve actuated either for suction or for exhaust

Info

Publication number: WO1991010046A1
Application number: PCT/IT1990/000102
Authority: WO
Inventors: Armando Romano
Original assignee: Armando Romano
Priority date: 1989-12-22
Filing date: 1990-12-21
Publication date: 1991-07-11
Also published as: IT1238307B; IT8948691A1; IT8948691A0

Abstract

The cylinder head (6) for reciprocating endothermic engines according to the present invention comprises at least one valve (10) actuated either for suction or for exhaust interacting with a first and a second arrangement of valves of the flap type acting as non-return or unidirectional valves and comprising flexible flaps, the first arrangement (19) permitting the passage towards the cylinder only of the suction gases, and the second (20) permitting the discharge towards the exhaust manifold only of the combusted gases, the said at least one valve being formed by a poppet valve (10) of a substantially conventional type actuated by a rotating camshaft (14) synchronised with the drive shaft.

Description

_CYLI_NDER HEAD FOR RECIPROCATING ENDOT__EKMlC" ENGINES^" PROVIDED WITH AT LEAST ONE VALVE ACTUATED EITHER FOR SUCTION OR FOR EXHAUSTDESCRIPTIO_N

The present invention relates to a cylinder head for endothermic reciprocating engines, which cylinder head possesses at least one valve actuated either for suction or for exhaust.

It is known that, in endothermic reciprocating engines, a particularly delicate structure is that of the cylinder head, especially in the case of Otto-cycle or four-stroke engines, or in the case of diesel-cycle engines.

There are, in fact, innumerable solutions for these structures from the general technical standpoint. The large number of solutions, some now obsolete and a great many others still current, clearly indicates that no general solution to the problem has yet been found in so far as many factors come into play, often in mutual conflict from the strictly technical standpoint or in conflict from the economic standpoint.

A problem within the problem, as regards the cylinder head of endothermic engines of the above- mentioned type, is that of controlling the suction and exhaust phases.

Conventionally, the suction and exhaust in engines of this type are controlled by means of at least two valves of the poppet type, actuated by means of cams, one for controlling the suction phase and one for controlling the exhaust phase of the burnt gases.

In the engines known as "naturally aspirated" a very important factor is the trapping coefficient, that is to say the minimisation of resistance to the flow of aspirated gases, air/petrol mixture in Otto engines or air in diesel engines. In engines of an economical type, two valves of the abovementioned type are employed, usually of equal size. For higher-performance engines, asymmetrical valves are employed, where the induction valve is larger than the exhaust valve, or alternatively multiple-valve arrangements, for example two induction valves and one exhaust valve. In some cases, as many as five valves per cylinder have been used. These solutions, while improving the problem of the trapping coefficient, enormously increase the complexity of the cylinder head and of the distribution actuating members, and the production costs. Relatively recently, valve systems of the flap type have been developed as non-return or unidirectional valves comprising flexible metal flaps which permit a unidirectional flow of gas.

As a matter of principle, non-return flap valves are widely employed in reciprocating (piston-type) compressors for gas or air. In endothermic reciprocating engines, the use of flap valves has been suggested (Utility Model Application no. 2314IB/80 in the name of Alfa Romeo S.p.A.; Patent Applications no. 22886A/82 and no. 19397A/83 in the name of Alfa Romeo Auto S.p.A.; Patent Application no. 19766A/88 in the name of Alfa Lancia Industriale S.p.A.; EP-A-0 268 339 in the name of Adler S.p.A) for controlling the flow of suction gases. The present invention provides a cylinder head for endothermic reciprocating engines, which comprises at least one valve actuated either for suction or for exhaust interacting with a first and a second arrangement of valves of the flap type acting as non-return or unidirectional valves and comprising flexible flaps, the first arrangement permitting the passage towards the cylinder only of the suction gases, and the second permitting the discharge towards the exhaust manifold only of the burnt gases, the said at least one valve being formed by a poppet valve of a substantially conventional type actuated by a rotating camshaft synchronised with the drive shaft.

Expediently, the at least one valve is disposed to interact with a cam-follower actuated by a single-lobe cam associated with a camshaft disposed to cause the opening of the at least one valve to coincide with the suction phase and with the exhaust phase.

According to the present invention, the cylinder head may comprise a further actuated valve associated with a further suction duct, the further valve being associated with a further camshaft disposed to actuate the opening thereof during the suction phase.

In this case, advantageously, the inlet manifold connected to the said at least one valve and the inlet manifold connected to the further valve are connected in a switchable manner to first and second carburetion means.

The structure of the cylinder head according to the present invention will be better understood by reference to the figures in the attached drawings, which represent two embodiments given solely by way of non- limiting example, and wherein:

Figures 1, 2, 3 and 4 successively show the cylinder head arrangement according to the present invention respectively in the phases of suction, compression at top dead centre, combustion and exhaust in a first embodiment;

Figures 5, 6, 7 and 8 successively show a second embodiment of the cylinder head according to the present invention, respectively in the phases of suction, compression at top dead centre, combustion and exhaust; and

Figure 9 shows diagrammatically the timing of the valves in conventional internal combustion engines and in internal combustion engines according to the first and second embodiments of the present invention.

It should be noted that the drawings of the embodiments shown relate in particular to an internal combustion engine (Otto cycle) . Variations which are obvious to a person skilled in the art will permit easy adaptation to diesel-cycle operation.

With reference to Figure 1, a typical four-stroke engine comprises a cylinder block 1 on which is machined or fixed a cylinder 2 within which slides a piston 3, connected in a known manner via a piston pin 4 and a connecting rod 5 to the drive shaft (not shown) .

The cylinder head designated as a whole by 6 comprises a chamber 7, which for example is hemispherical, bearing a seat 8 for the head 9 of a valve 10 of known structure. The valve 10 is associated with conventional spring and cam-follower means indicated respectively at 11, 12 which interact with a cam 13 fixed to a camshaf 1 . An inlet duct 15 and an exhaust duct 16 converge in the zone of action of the valve 10 and are connected respectively at 17, 18 to the conventional inlet and exhaust manifolds (not shown) .

In the zones 17, 18 are positioned non-return flap valves indicated as a whole by 19, 20 and comprising a body and, respectively, flaps 21, 22 disposed to permit the flow only in the direction of the arrows FA, FS.

The mode of operation of the device according to the invention is clearly apparent from the attached drawings. In the working phase shown in Figure 1, the cam 13 holds* the valve 10 open. The pressure reduction which is created in the cylinder 2 by the downward movement of the piston 3 causes the opening of the flaps

21 of the valve 19, and the air/petrol mixture can enter the cylinder 2 as indicated by the arrows. When the pressure reduction ceases and the piston 3 arrives at the bottom dead centre, the transient states due to the inertia of the air/petrol mass being ended, the flaps 21 close and the valve 10 also closes as a result of the rotation of the camshaft 14. At the end of the compression stroke, the situation is as shown in Figure

2, in which all the valves are closed.

After the decompression phase follows the combustion phase, illustrated in Figure 3, where it is noted that the cam 13, continuing its rotation in the anti-clockwise direction as shown in the drawings, is about to open the valve 10. The opening of the valve 10 occurs during the exhaust stroke as shown in Figure 4. In the situation according to Figure 4, the flaps 22 of the flap valve 20 will open, while the flaps 21 of the flap valve 19 remain closed under the action of the counter-pressure which exists in the zone of action of the valve 10. The burnt gases thus escape towards the exhaust manifold, as shown in Figure 4.

Clearly, if a different timing is required as between actuation of suction and exhaust, means could be provided to vary the sensitivity of the flap valves.

Figures 5 to 8 show a variation of the embodiment described above. In the variation shown in the above- mentioned Figures 5 to 8, parts corresponding to those in

Figures 1 to 4 will be indicated by the same reference numerals plus a prime ( ' ) .

In this embodiment, an auxiliary inlet of valve of conventional type is provided in order further to increase the trapping coefficient of the internal combus¬ tion engine. The provision of the auxiliary inlet valve makes it possible to increase the trapping coefficient to a much greater extent relative to the known multi-valve arrangements in so far as the valve which is actuated with a double suction/exhaust function makes it possible to have inlet ports having a much greater active area than that which is possible with the valves of separate function (suction and exhaust) of the known arrangements.

As may be noted in Figure 5, the cylinder head possesses a structure identical to that described above with reference to Figures 1 to 4. To this structure is added an additional inlet manifold designated 50, inter¬ acting with a poppet valve 51 actuated by a cam 52 fixed to a second camshaft 53. The return spring and the cam- follower 54 of the poppet valve 51 may be seen behind the exhaust duct 16'.

During operation, the head 9' of the valve shown as a whole by 10' and the members associated therewith operate as described above with reference to Figures 1 to 4.

In the construction shown in Figures 5 to 8, during the suction phase, in addition to the valve 10', the poppet valve 51 also comes into operation, actuated by the cam 52. It should be noted that the timing of the move¬ ment of the poppet valve 51 may be different from that of the valve 10' in order further to improve the suction performance, given that the poppet valve 51 is not subject to the constraints mentioned above for the valve not subject to the constraints mentioned above for the valve 10' .

With this arrangement, the timing of the valve

10' can be predetermined in order to optimise its performance in the exhaust phase; the adverse consequences arising therefrom for the suction phase can be compensated by modifying the timing of the valve 51.

In practice, the double-valve arrangement 10', 51 permits optimisations which would not be possible with conventional engines. This derives from the fact that, even with the aid of modern means of calculation, it is virtually impossible to predetermine the optimum operating conditions mathematically, and that consequently the final tuning of an engine is the subject of procedures of trial and error which have to take account of many factors which cannot be reduced to a simple mathematical model.

The successive cycles of the Otto cycle are shown in sequence in Figures 5, 6, 7 and 8, respectively illustrating the phases of suction, compression, combustion and exhaust, and no detailed explanation thereof is considered necessary. Likewise, although reference has been made to the Otto cycle, the arrangement of Figures 5 to 8 can be used for diesel- cycle engines.

Figure 9 illustrates, by way of example, the timing of the valves in conventional internal combustion engines and in internal combustion engines according to the first and second embodiments of the present invention.

In this figure, the abbreviations have the following meanings: A = suction C = compression Sp = combustion

Sc = exhaust

Line I shows the timing sequence for a conventional engine.

The lines II show in heavier type the "lifting" of the suction and exhaust valves in a conventional engine.

Line III shows the "lifting" of the double- function valve according to the invention, where the loop indicates the openings of the suction and exhaust flap valves.

Lines III and IV, considered together, indicate the operation of the second embodiment of the invention, and line IV indicates the "lifting" of the auxiliary suction valve.

It is further noted that, with the arrangement shown in Figures 5 to 8, in the case of Otto-cycle engines, the inlet manifold 17' or the inlet manifold 50 may be connected to carburetion or direct injection means which can be actuated separately, depending on whether the engine is to require reduced power or full power, the carburetion thus being optimised in both cases, improving performance and reducing specific rates of consumption.

Furthermore, with the arrangement according to the invention shown in Figures 1 to 4 and in Figures 5 to 8, the performance of an endothermic engine can be improved to obtain, depending on the design objectives, greater power or reduced consumption for equal power.

Finally, consideration should be given to the fact that, with the arrangement according to the invention, by virtue of the improved overall performance, in the case of Otto-cycle engines, the compression ratio can be reduced, allowing the problem-free use of low- octane fuels (unleaded) or fuels mixed with ethanol, with the known economic and environmental advantages.

The present invention has been described with reference to its currently preferred embodiments, given by way of non-limiting illustration, and it is understood that, in practice, the said embodiments can be subjected to variations and modifications by a person skilled in the art without departing from the scope of protection of the present industrial property right.

Claims

CLAIMS 1. Cylinder head for reciprocating endothermic engines, characterised in that it comprises at least one valve actuated by the either for suction or for exhaust interacting with a first and a second arrangement of valves of the flap type acting as non-return or unidirectional valves and comprising flexible flaps, the first arrangement permitting the passage towards the cylinder only of the suction gases, and the second permitting the discharge towards the exhaust manifold only of the combusted gases (exhaust) , the said at least one valve being formed by a poppet valve of a substantially conventional type actuated by a rotating camshaft synchronised with the drive shaft.

2. Cylinder head according to Claim 1, characterised in that the at least one valve is disposed to interact with a cam-follower actuated by a single-lobe cam associated with a camshaft disposed to actuate the opening of the at least one valve to coincide with the suction and with the exhaust phase.

3. Cylinder head according to Claim 2, characterised in that it comprises a further actuated valve associated with a further suction duct, the further valve being associated with a further camshaft disposed to actuate the opening thereof during the suction phase.

4. Cylinder head according to Claim 3, characterised in that the inlet manifold connected to the said at least one valve and the inlet manifold connected to the further valve are connected in a switchable manner to first and second carburetion means.

5. Cylinder head according to Claim 1 or 2 characterised in that it operates in accordance with the Otto cycle.

6. Cylinder head according to Claim 1 or 2 characterised in that it operates in accordance with the diesel cycle.