EP0302042B1 - Six-stroke internal combustion engine - Google Patents

Abstract

The six strokes are the intake of air, the initial compression accompanied or followed by any cooling, the second compression followed by combustion, the initial expansion producing useful work, the second expansion also producing useful work and finally the discharge of the burnt gases. This new engine on which combustion is by spark ignition (petrol version), or auto-ignition (diesel version) will preferably comprise a multiple of five non-uniform cylinders. It will have an energy efficiency which may be up to 30% higher than that of a four-stroke internal combustion engine. <IMAGE>

Description

The present invention relates to an internal combustion engine of the type described in the preamble to the main claim.

An engine of this type is known from US-A-3,789,807. In this engine, the working chambers of the two cylinders are also connected by a pipe to allow the discharge of the precompressed air into the suction cylinder at low pressure. in the high pressure combustion cylinder. This line is provided with a valve which is controlled so that this discharge ends before the cylinder piston has reached its top dead center position. In addition, a collecting chamber is arranged between the two cylinders in the transfer line. This comprises, in addition to the aforementioned transfer valve, associated with the combustion cylinder, an introduction valve which is associated with the suction cylinder so that the introduction of the combustion gases under high pressure takes place when the cylinder piston aspirant is at its top dead center position. Then the mixture of the compressed air which had remained in the working chamber of these cylinders after the closing of the discharge valve and of the gases under high pressure coming from the collecting chamber is ignited to carry out a second combustion. The purpose of this double combustion is to reduce the rate of pollutants in the exhaust gas.

Now this internal combustion engine with pistons alternatives has the disadvantage of having an energy efficiency which is far from optimal.

The object of the present invention is to propose an engine which makes it possible to increase the energy efficiency of an engine of the type described in the preamble.

To achieve this object, the engine according to the invention has the characteristics which are set out in the characterizing part of claim 1.

As is clear from this claim, the invention makes it possible to obtain the objective sought by carrying out a double compression and a double expansion, that is to say by means of an engine structure carrying out a six-stroke thermodynamic cycle .

An engine which has four cylinders and performs double compression and double expansion is already known from DE-P-3518031. However, unlike the invention, these four cylinders are mounted in series and traversed successively by the fluid to execute the above operations. In addition, the known engine comprises intermediate pressure chambers between two adjacent cylinders.

The engine according to DE-A-3518031 therefore has a very complex structure and fundamentally different from that of the engine according to the invention where the cylinders are grouped in pairs which gives the engine a much higher efficiency.

The first step of the six-step cycle of the invention, that is to say the suction of air or of the air-fuel mixture, only involves low pressure suction cylinders. The third and fourth beat of this same cycle, that is to say the second compression and the first expansion of the combined gases respectively, only involve high pressure oxidizing cylinders. The final delivery of the combined gases under low pressure, which represents the sixth time of the cycle, only involves low pressure suction cylinders and, if they exist, low pressure pressure cylinders. The second stage of the cycle in question, that is to say the first compression of the air or of the air-fuel mixture accompanied or possibly followed by cooling, involves a low pressure suction cylinder and a high pressure oxidizing cylinder preferably in such a way that the piston of the second recedes in order to be able to receive the air or the precompressed air-fuel mixture while the piston of the other advances and expels this same fluid. They will therefore move in phase opposition to each other and we will call in the rest of this text such a set of a low pressure suction cylinder and a high pressure oxidizing cylinder a "pair of cylinders compressants " . The fifth stage of the six-stage cycle, that is to say the second expansion of the combined gases, involves a low pressure suction cylinder, a high pressure oxidizing cylinder and possibly a low pressure discharging cylinder so that the piston from the high-pressure oxidizing cylinder, advancing, pushes the combustion gases through the transfer tube (s) to the adjacent low-pressure suction cylinder, the piston of which then moves back to accommodate these same gases or a part of them, and possibly to the low pressure pumping cylinder, also adjacent to the same high pressure oxidizing cylinder, and the piston also moves back to accommodate the other part of the combined gases. this piston and that of low pressure suction cylinder move in phase with each other and in phase opposition with respect to the piston of the high pressure oxidizer cylinder. In the absence of the low pressure pressure cylinder, we will call the set of two cylinders performing the second expansion as described above a " pair of pressure reducing cylinders " and in the case where the low pressure pressure cylinder exists a "triplet of cylinders relaxing . " It is then seen that two cylinders forming a pair of compressing cylinders will not preferably form a pair of expansion cylinders or preferably will not belong to the same triplet of expansion cylinders. It goes without saying that the displacement of the low-pressure suction cylinders must be greater than that of the high-pressure oxidizing cylinders so that we can speak of air or of a pre-compressed air-fuel mixture at the end of the second stage.

For reasons of symmetry, all the low pressure suction cylinders, as well as all the high pressure oxidizing cylinders, will preferably have the same bore and the same stroke respectively. Regarding the displacement of the low pressure pressure cylinders, if they exist, this is to be optimized as a function of the displacement of the high pressure oxidizing cylinders and low pressure aspirants. Probably, for reasons of constructive ease, it will have the same bore and stroke as the low pressure suction cylinders.

This embodiment of the invention is therefore an internal combustion engine essentially composed of at least one pair of compressing cylinders and at least one pair, possibly a triplet, of expansion cylinders.

According to another embodiment of the invention, the engine comprises a single pair of cylinders, the precompressed air discharged by the suction cylinder at low pressure is stored in a tank before being transmitted at the right time to the combustion cylinder.

The ignition will be either of the controlled type or of the spontaneous type and we will speak of a six-stroke internal combustion engine with controlled ignition and in the other case of a six-stroke internal combustion engine with spontaneous ignition.

The main advantage, which is also the aim of the present invention, compared to existing engines is a significant increase in fuel efficiency. For exchanger powers and maximum pressures which seem completely acceptable to us, the calculations promise us an increase in this efficiency of approximately 25 to 30% in the case of spark-ignition engines, this being mainly due to the increase in overall compression ratio. In the case of spontaneous ignition engines, the gain in efficiency will probably not be as great. In all cases, the presence of the low pressure pressure cylinder is beneficial to performance because it provides us with an overall expansion rate greater than the overall compression rate, which is generally an advantage of the six cycle. time compared to the four-stroke cycle.

The compactness of the combustion chamber, which is in fact the dead space of the high-pressure oxidizing cylinder which we know is relatively small, contributes, in the case of the petrol version, to avoid rattling which makes it possible to further increase the compression ratio or to use petrol with a lower octane number, therefore less harmful, and in the case of the Diesel version, probably makes it possible to increase the richness during the injection of the combustible.

The compactness of the combustion chamber, that is to say the higher volume / bore ratio, provides savings in heat losses during combustion.

A smaller second compression ratio (4 ... 6) and the distribution of the rebound over a full revolution of the crankshaft significantly reduces the unfavorable effect on the internal efficiency of non-instantaneous combustion (combustion time approximately 2 milliseconds) for high rotational speeds.

The concentration of large pressures on small cylinders saves sealing segments in large low pressure cylinders, which reduces mechanical losses. This concentration also makes it possible to reduce the weight of the engine.

Another advantage of the new engine is that the exhaust gases are significantly less hot which will ensure a longer service life of the exhaust system and in addition in combination with the fact as the dead space of the suction cylinders will be as small as possible, we can expect a high filling rate.

The fact that the cylinders in direct communication with the outside, that is to say the low pressure cylinders, do not undergo combustion and the fact that the depressions during the openings of the low pressure discharge valves will be significantly lower, will likely lead to a more favorable tone.

The major drawback is the fact that the total power-to-displacement ratio is probably lower than that of existing engines.

• Les figures 1a à 1c sont respectivement des vues en élévation du bloc moteur où l'on distingue le système de la commande des soupapes, c'est-à-dire l'arbre à cames et les culbuteurs, en coupe horizontale du bloc moteur et finalement en coupe verticale dans celui-ci.
• La figure 2 à échelle plus grande, montre les différents organes repris à la figure 4, où l'on a disposé toutes les soupapes sur une ligne pour simplifier le dessin,
• la figure 3 à grande échelle, montre en une coupe verticale un ensemble raccord de tubulure et soupape, où le ressort est du type vase d'expansion.
• La figure 4 à petite échelle, montre en a à d les quatre phases que l'on observe pour deux tours de rotation du vilebrequin, où comme à la figure 2, toutes les soupapes sont alignées,
• la figure 5 montre de façon schématique un moteur selon l'invention à six temps et quater cylindres, a étant une vue en coupe verticale, b montrant la disposition des soupapes et tubulures et c montrant la disposition des cames et poussoirs, et
• la figure 6 montre le diagramme pression-volume dans les cylindre du cycle à six temps.

The invention is described in more detail with the aid of the appended figures, referring to two embodiments, which are a six-stroke five-cylinder internal combustion engine and a four-cylinder engine. First of all, note that all the figures are only qualitative concept drawings. Among these figures.

• FIGS. 1a to 1c are respectively elevation views of the engine block where the valve control system is distinguished, that is to say the camshaft and the rocker arms, in horizontal section of the engine block and finally in vertical section in it.
• FIG. 2 on a larger scale, shows the various members shown in FIG. 4, where all the valves have been placed on a line to simplify the drawing,
• Figure 3 on a large scale, shows in a vertical section a set of tubing connection and valve, where the spring is of the expansion tank type.
• Figure 4 on a small scale, shows a to d the four phases observed for two turns of the crankshaft, where as in Figure 2, all the valves are aligned,
• FIG. 5 shows schematically an engine according to the invention with six times and four cylinders, a being a view in vertical section, b showing the arrangement of the valves and pipes and c showing the arrangement of the cams and tappets, and
• Figure 6 shows the pressure-volume diagram in the cylinders of the six-stroke cycle.

With reference to the figures, the six-stroke internal combustion engine with positive ignition is produced using five cylinders arranged in line. It has two high pressure suction cylinders 1, 5 located at the ends of the crankshaft, two high pressure oxidizing cylinders 2, 4 located alongside the low pressure suction cylinders respectively and finally a low pressure pressure cylinder 3 located in the middle. The inlet of the heat exchanger 28 is connected to the low suction cylinders pressure 1, 5 through the delivery pipes of precompressed air 33, 34 respectively and its outlet is connected to the high pressure oxidizing cylinders 2, 4 by the pipes of introduction of the precompressed air-fuel mixture 31, 32 respectively. It is at these introduction pipes 31 and 32 that the fuel is introduced by means of a controlled injection or of, preferably two carburettors pressurized, by putting, for example, the tank of these under the pressure prevailing inside the exchanger by means of a simple tube which connects the two. The transfer valves 14, 16, 18 and 20 are located in the cylinder heads of the high-pressure oxidizing cylinders 2 and 4. The low-pressure suction and discharge cylinders are connected to the exhaust manifold or manifold 30 by the gas discharge valves combined at low pressures 13, 21 and 17 respectively. The transfer pipes 24, 25 and 26, 27 intimately connect the cylinders 1 and 2, 2 and 3, 3 and 4, as well as 4 and 5 respectively. The low pressure suction cylinder 1 on the left side and the high pressure combustion cylinder 4 on the right side form a pair of compressing cylinders as this has been defined above. The second pair of compressing cylinders is formed by the low pressure suction cylinder 5 on the right side and the high pressure oxidizing cylinder 2 on the left side. This engine comprises two triplets of expansion cylinders as they have been defined above. These are first the low pressure pressure cylinder 3 located in the center and the two low pressure suction cylinders 1 and high pressure oxidizer 2 on the left side and then the same low pressure pressure cylinder 3 and the low pressure suction cylinders 5 and high oxidant pressure 4 on the right side.

Let us now examine in detail the four phases which are encountered during two turns of the crankshaft, for the six-stroke and five-cylinder engine described above, with reference to Figures 2 and 4.

Figure 4 a): The pistons of the high pressure oxidizing cylinders 7 and 9 are going up, and the pistons of the low pressure cylinders 6, 8 and 10 are going down. The low pressure suction cylinder on the left side 1 draws in the air supplied by an intake manifold indicated at 43 and the corresponding valve 11 is open. The adjacent high-pressure oxidizing cylinder 2 compresses the air-fuel mixture a second time and the spark plug will light it towards the end of this compression. The second triplet of expansion cylinders 3, 4 and 5, defined above, performs the second expansion of the combined gases, the corresponding transfer valves 18 and 20 being open.

Figure 4 b): The pistons of the high pressure oxidizing cylinders go down and those of the low pressure cylinders go up now. The first pair of compressing cylinders 1, 4 performs the first compression, the corresponding valves 12, 19 being open. The high pressure oxidizing cylinder 2 performs the first expansion of the combined gases. The low pressure discharge cylinders 3 and low pressure suction cylinder 5 on the right side expel the combined gases, the discharge valves 17 and 21 being open.

Figure 4 c): The pistons of the high pressure oxidizing cylinders go up while the pistons of the low pressure cylinders go down. The low pressure suction cylinder 5 on the right side in turn performs the air suction, the suction valve 23 being open. The adjacent high-pressure oxidizing cylinder 4 performs the second compression of the air-fuel mixture and the spark plug will light it towards the end of this compression. The first triplet of expansion cylinders 1, 2 and 3 performs the second expansion of the combined gases, the corresponding transfer valves 14, 16 being open.

Figure 4 d): The pistons of the high pressure oxidizing cylinders go down and those of the low pressure cylinders go up again. The second pair of compression cylinders 5 and 2 performs the first compression of the air-fuel mixture, the corresponding delivery and introduction valves 22 and 15 being open. The right side high pressure oxidizing cylinder 4 performs the first expansion of the combined gases. The cylinders driving 3 and sucking 1 low pressure expel the combined gases. The discharge valves 17 and 13 are open.

Now we can return to Figure 4 a).

Another embodiment of the six-stroke internal combustion engine would be a five-cylinder engine as just described, where the difference lies in the way of introducing the fuel, which this time will be directly injected into the combustion chambers high pressure oxidizing cylinders 2 and 4 where it will ignite spontaneously. The power of the radiator 28 as well as the displacement and compression ratios will obviously have to be readjusted.

From these two embodiments, we deduce yet another by simply deleting the low pressure pressure cylinder 3, everything else remaining unchanged.

This version obviously lends itself to the two types of ignition in question. Now you don't have to line up the four cylinders. We can also store them on either side of the crankshaft where the low pressure cylinders are located opposite the high pressure oxidizing cylinder with which they form a pair of compressing cylinders and next to the high pressure oxidizing cylinder with which they form a pair of relaxing cylinders. It goes without saying that it is possible, by juxtaposing blocks of five or four cylinders as described above, to create other embodiments of the present invention.

For all the envisaged embodiments, the heat exchanger 28 can be replaced by two independent radiators so that each one connects the precompressed air delivery pipe 33 (or 34) of the low pressure suction cylinder 1 (or 5) to the inlet manifold 32 (or 31) of the corresponding high pressure oxidizing cylinder 4 (or 2). But in this case, the heat exchange surfaces will be less profitable, because the speed of air flow through the exchanger is noticeable only for 25% of the time, on the other hand, in the case of the single exchanger, this is the case for 50% of the time. Despite this, this can become interesting for reasons of constructive simplicity in the case of the six-stroke diesel version, because the power of the exchanger, may be that experience shows that it does not even need at all , will probably be lower.

Another detail is worth considering. The discharge and introduction valves for precompressed air 12, 15, 19 and 22 must provide a two-way seal. Indeed, in regime, the heat exchanger will be constantly under pressure and these valves are momentarily subjected to a force which tends to open them when the downstream pressure (i.e. the pressure inside the exchanger) exceeds that which reigns upstream. This will be the case during suction for low pressure suction cylinders and towards the end of the discharge of pressurized gases for high pressure oxidizing cylinders. On the other hand, it is necessary to avoid that the air can escape along the valve stem 38. To remedy these two difficulties, one could consider using instead of conventional valve springs springs of the expansion vessel type 39. By drilling communication holes 40 to put the vessel under the pressure prevailing in the radiator 28 and ensuring that the diameter of the vessel is greater than that of the base of the valve 41, the pressure prevailing inside the exchanger as well as the pressure prevailing in the cylinder will both tend to close the valve in question. During startup, the radiator not being under pressure, only the mechanical stiffness of the vessel 39 will have to ensure the closing of the valve in question. Nothing prevents the same type of spring from being used for the other valves, in particular the transfer valves 14, 16, 18 or 20. For the low pressure suction and discharge valves 11, 13, 17, 21 and 23 , it is preferable to use conventional valve springs.

Another detail to note is that the transfer valves 14, 16, 18 and 20 and the suction valves 11 and 23 are centered relative to the vertical plane of symmetry of the engine block. Therefore, the corresponding rockers 35 will of a special shape so that their pivot axes are preferably orthogonal to the axis of the crankshaft.

A final constructive detail concerns the cold start, which will probably pose a problem for the six-stroke engine. A system of tubes 36 and valves 37, shown schematically in Figure 2, actuated by the user or automatically, will divert the flow of compressed air so that it arrives at the high oxidizing cylinders pressure without passing through the heat exchanger. The arrows in solid lines, with reference to FIG. 2, indicate the flow of precompressed air in regime and in dotted lines that of starting. The corresponding positions of the valves are also drawn in solid lines and dotted lines respectively.

FIG. 5 schematically illustrates in several views a six-stroke, four-cylinder internal combustion engine according to the present invention. Figures 5b and 5c show schematically respectively the arrangement of valves and pipes and the arrangement of cams and pushers.

FIG. 8 illustrates the six-stroke cycle according to the invention. This figure gives the diagram of the pressure as a function of the volume in the cylinders. Curve 1 indicates the pressure prevailing in the high pressure oxidizing cylinder, while curve b gives the pressure that is obtained in the low pressure suction cylinder. This diagram has been drawn up for an engine corresponding to that shown in FIG. 5.

The six-stroke internal combustion engine which is the subject of the present invention will find use everywhere, where four-stroke internal combustion engines are currently used, in particular in road transport.

The new engine according to the invention, the combustion of which is with ignition either controlled (petrol version) or spontaneous (Diesel version), will preferably comprise in multiple of five non-uniform cylinders. It will have an energy efficiency which can be up to 30% higher than that of a four-stroke internal combustion engine.

Claims (11)

1. An internal combustion engine with at least two cylinders which each comprise a working chamber whose volume is varied by displacement in the cylinder of a piston between a position of upper dead centre and a position of lower dead centre, under the effect of pressure forces generated periodically in the aforesaid chamber to each cylinder being associated with valve means for inlet and exhaust of a gaseous fluid, the piston of each cylinder being linked to a crankshaft of the engine, the cylinders being set up in pairs, one cylinder (2) acting as a high pressure combustion cylinder whereas the other cylinder (1) is adapted to operate as a low pressure suction cylinder, the chamber of the latter being able to communicate with an air inlet manifold (43) by means of one actuated device at least such as an inlet valve (11) for pre-compression of sucked in air, with a working chamber of the combustion cylinder (2) to which it is associated through at least one transfer valve (14) for transferring gases burnt at high pressure in the combustion cylinder, into the suction cylinder (1), and with a burnt gas exhaust manifold (30), by one exhaust valve (13) at least, characterized in that the engine comprises at least four cylinders (1,2,4,5) set up in order to create two pairs (1,2; 4,5), the working chamber of the low pressure suction cylinder (1 or 5) of one pair is able to communicate with the working chamber of the combustion cylinder (4 or 2) of the other pair in order to expel in the latter the pre-compressed air to which will eventually have been added the fuel by one exhaust valve (12 or 22) at least associated to the suction cylinder and by one feed-in valve (19 or 15) at least of the aforesaid air or pre-compressed expelled mixture, associated to the combustion cylinder (4 or 2) of the other pair, for the purpose of compression and combustion of the air-fuel mixture and directly with the associated working chamber of the combustion cylinder (2 or 4), through the aforesaid transfer valve (14 or 20) at least, for transfer of the gas burnt at high pressure in the combustion cylinder, in the suction cylinder for the purpose of a second expansion, while the valves are actuated in a manner such that the engine operates as a six stroke internal combustion engine.

2. Engine according to claim 1, characterized in that it comprises a third low pressure cylinder (3) whose working chamber is able to communicate with the working chambers of the two combustion cylinders (2,4) by two transfer valves (15,18) at least advantageously associated to the latter and operating in synchronization with the aforesaid transfer valves (14,20) for the purpose of contributing to the aforesaid second expansion of burnt gases and with the exhaust manifold (30), by one exhaust valve (17) at least.

3. Engine according to claim 2, characterized in that the five cylinders (1 to 5) are set up in line, the two suction cylinders (1,5) located at the ends of the crankshaft to which they are connected, the third low pressure cylinder (3) being located in the middle.

4. Engine according to the preceding claims, characterized in that it comprises a heat exchanger (28) whose inputs (33,34) are able to communicate with the working chambers of the suction cylinders (1,5), through the aforesaid exhaust valves (12,22) and through the outlets (31,32) to the working chambers of the combustion cylinders (2,4), by means of the aforesaid inlet valves (15,19).

5. Engine according to the preceding claims, characterized in that the communication channels of the working chambers of the suction cylinders (1,5) with the combustion cylinders (2,4) comprise means for introducing fuel into pre-compressed air, such as methods for injection actuated by spontaneous ignition or by carburetor devices.

6. Engine according to anyone of the claims 1 and 3 to 5, characterized in that it comprises a multiple of four cylinders.

7. Engine according to anyone of the claims 1 to 6, characterized in that it comprises a multiple of five cylinders.

8. Engine according to anyone of the preceding claims characterized in that one of the valve springs at least is of the pressurized expansion chamber (39) type.

9. Engine according to claim 7, characterized in that the expansion chamber (39) used as a valve spring has perforations (40) set in the wall of the manifold which enable setting up inside the expansion chamber (39) of the pressure which is upstream of the valve.

10. Engine according to one of the claims 1 to 9, characterized in that the two or three pistons (6,8,10) of low pressure cylinders (1,3,5) are adapted for displacement in phase and in inversion of phase to pistons (7,9) of high pressure combustion cylinders (2,4).

11. Engine according to any öne of the preceding claims characterized in that aforesaid valves associated to different cylinders are kept in a state of opened or closed operation during virtually the whole duration of the piston stroke of the corresponding cylinder.

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