EP0376909B1

EP0376909B1 - Internal-combustion engine

Info

Publication number: EP0376909B1
Application number: EP89870196A
Authority: EP
Inventors: Gerhard Schmitz
Original assignee: Gerhard Schmitz
Priority date: 1988-12-30
Filing date: 1989-12-01
Publication date: 1994-05-11
Anticipated expiration: 2009-12-01
Also published as: BE1002364A4; EP0376909A1; DE68915262D1; US5072589A; AT105606T

Description

The subject of the present invention is a method for producing an internal combustion engine and an engine for implementing this method, of the type described in claims 1 and 2 respectively.
A method and an engine of this type are described in French patent No. 771 168. In this engine, the combustion and low voltage cylinders are arranged so that the expansion which has started in each of the two four-stroke combustion cylinders can end in the low voltage cylinder. On the other hand, each oxidizing cylinder is supplied with fresh air or an air-fuel mixture, separately and independently of the low-voltage cylinder.
This engine aims to increase the power per cylinder while maintaining very good efficiency, thanks to the possibility of improving combustion and expansion conditions.
The present invention aims to increase the energy efficiency of an internal combustion engine with compound cylinders of the type described in the prior art.
To achieve this object, the method according to the invention and the engine for its implementation include the characteristics which are set out in the characterizing parts of claims 1 and 2, respectively.
The invention will be better understood, and other objects, characteristics, details and advantages thereof will appear more clearly during the explanatory description which follows, made with reference to the appended schematic drawings given solely by way of example illustrating two embodiments of the invention, and in which:

Figure 1 is a vertical sectional view of the engine block of a first embodiment with three cylinders, of an engine according to the invention.
FIG. 2 is a view in horizontal section of the engine block according to FIG. 1.
FIGS. 3a to 3d show four phases of the operation of the engine according to the invention shown in FIG. 1.
FIG. 4 illustrates the aspiration of air into the crankcase of the low-pressure two-stroke cylinder;
FIG. 5 illustrates the exhaust of the gases combined by the low-pressure two-stroke cylinder, in the case of the version with transverse scanning.
FIG. 6 illustrates the transverse sweeping of the remaining combined gases by the air in the low-pressure two-stroke cylinder.
FIG. 7 schematically illustrates the four phases taking place during two turns of rotation of the crankshaft in a two-stroke internal combustion engine with five cylinders, constituting a second embodiment of the invention.

Figures 1 to 6 relate to a first embodiment of an engine according to the invention, namely an internal combustion engine with two stages stepped by controlled ignition which is produced using three cylinders arranged in line. It comprises two high pressure oxidizing cylinders 2, 3 located at the ends of the crankshaft and a central cylinder 1, low pressure and two-stroke. The volume of the low pressure cylinder 1 is greater than that of the oxidizing cylinders 2,3. A heat exchanger 15 is connected to the low pressure cylinder 1 by a precompressed air delivery pipe 12 and its outlet is connected to the two high pressure oxidizing cylinders 2, 3 by the pipes for introducing the precompressed air-fuel mixture 13, 14 respectively. The tubing 12 is closable by a discharge valve 7 associated with the low pressure cylinder, while the tubing 13, 14 are provided with introduction valves 8, 11 associated with the oxidizing cylinders 2,3. It is at the level of these introduction tubes 13 and 14 that the introduction of the fuel by means of a controlled injection device 25 or a carburetor. The working chambers of the oxidizing cylinders 2, 3 are connected to the working chamber of the low pressure cylinder 1, respectively by transfer pipes 16, 17 of the combined gases. The transfer pipes 16, 17 are respectively provided with transfer valves 9, 10 associated with the oxidizing cylinders. The transfer valves 9 and 10, the air introduction or air-fuel mixture valves 8 and 11 as well as the spark plugs 26 are located in the cylinder head of the high pressure oxidizing cylinders 2 and 3. The jacket of the low pressure cylinder 1 has exhaust ports 20 for the combined gases and fresh air intake 22, connected respectively to an exhaust manifold for the combined gases 19 and a fresh air intake manifold 18. The low pressure casing 24, located downstream of the piston 4 of the cylinder 1 is a closed enclosure which is connected by means of the ports 21 and a scanning tube 23 to the part upstream of the low pressure piston 4.
In this configuration of the three cylinders 1 to 3, the low-pressure two-stroke cylinder 1 forms with the high-pressure oxidizing cylinder on the left 2 first a first pair of compressing cylinders and a first pair of expansion cylinders. With the right high-pressure oxidizing cylinder 3, the low-pressure cylinder 1 first forms a second pair of compressing cylinders and also a second pair of expansion cylinders. This will become apparent from the following description of the operation of the engine, with reference to FIGS. 3a to 3d. These figures show in detail the four phases which are encountered during two turns of the crankshaft in the engine represented in FIGS. 1 and 2. In FIGS. 3a to 3d the zones provided with simple points are zones filled with mixture air-fuel and the areas with small circles represent areas which are filled with combined gases.
Fig. 3a) The pistons 5 and 6 of the high-pressure oxidizing cylinders 2 and 3 are going up, and the piston 4 of the two-stroke low-pressure cylinder 1 is going down. The first pair of expansion cylinders, that is to say the combustion cylinders high pressure left 2 and low pressure two-stroke central 1, performs a second expansion of the combined gases, the transfer valve 9 being open. When the low-pressure two-stroke piston 4 approaches its bottom dead center, the combined gases will be evacuated by the exhaust ports 20 and the residue of these gases will be swept away by the fresh air supplied by means of the ports. intake 21. The right high pressure oxidizing cylinder 3 performs a second compression of the air-fuel mixture and the spark plug 26 will ignite it towards the end of this compression.
Fig. 3b) The two high pressure oxidizing pistons 5 and 6 are going down while the two-stroke low pressure piston 4 goes up. The first pair of compressing cylinders, i.e. the left high pressure oxidizing cylinder 2 and the two-stroke low pressure cylinder 1, performs the first compression, the precompressed air delivery and intake valves 7 air-fuel mixture 8 being open. Petrol is introduced at the level of the pre-compressed air-fuel mixture intake manifold 13. The high-pressure oxidizer cylinder on the right side 3 performs the first expansion of the combined gases.
Fig. 3c) The two high pressure oxidizing pistons 5 and 6 go up a second time while the two-stroke low pressure piston 4 goes back down. The second pair of expansion cylinders, that is to say the low-pressure two-stroke cylinder 1 and the right high-pressure oxidizing cylinder 3, in turn performs the second expansion of the combined gases, the corresponding transfer valve 10 being open. . When the low-pressure two-stroke piston 4 approaches its bottom dead center, the combined gases will be evacuated by the exhaust ports 20 and the residue of these gases will be swept away by the fresh air supplied by means of the ports. intake 21. The left high-pressure oxidizing cylinder 2 in turn performs the second compression of the air-fuel mixture, which will be ignited by means of a spark plug 26 towards the end of this compression.
Fig. 3d) The high pressure oxidizing pistons 5 and 6 go down again while the two-stroke low pressure piston goes up. The second pair of compression cylinders, i.e. the low-pressure two-stroke cylinder 1 and the right high-pressure oxidizing cylinder 3, now performs the first compression, the precompressed air delivery and intake valves 7 of the corresponding precompressed air-fuel mixture 11 being open. Gasoline is introduced at the level of the pre-compressed air-fuel mixture intake manifold 14. The left high-pressure oxidizing cylinder 2 performs the first expansion of the combined gases.
The next phase is that illustrated in Figure 3a).
Another embodiment of the two-stage two-stage internal combustion engine with three cylinders would be an engine as just described, but where the difference lies in the way of introducing the fuel, which this time will be directly injected towards the end of second compression in the combustion chambers of the high pressure oxidizing cylinders 2, 3 where it will then ignite spontaneously. The power of the radiator 15 as well as the displacement and compression ratios will obviously have to be readjusted.
From this embodiment of the three-cylinder engine, it is deduced, with reference to FIG. 7, that of five cylinders by juxtaposing two three-cylinder engines by arranging them in line so that the two central high-pressure oxidizing cylinders work perfectly in phase. We can then "merge" them into a single central high pressure oxidizing cylinder 3, which will then have a displacement preferably twice as large as that of the two high pressure oxidizing cylinders located at the ends of the crankshaft 2. The central high pressure oxidizing cylinder 3 will communicate with the two low-pressure two-stroke cylinders in the vicinity of 1 by means of valves 10 and transfer pipes 17. The second expansion of the combined gases located in this cylinder 3 will be done by transferring them simultaneously to the two low pressure cylinders with two adjacent two-stroke 1. FIGS. 7a to d show in detail the four phases that are encountered during two turns of the crankshaft in the two-stage two-stroke internal combustion engine with five cylinders, where the hatched areas in horizontal lines are filled with air only, hatched in small circles are filled with combined gases.
This procedure is obviously not limited to five cylinders and it is thus possible to create two-stage internal combustion engines of 5, 7, 9, ... cylinders. All these achievements lend themselves to two types of ignition, spontaneous and controlled.
All these versions of the two-stage two-stage internal combustion engine obviously also lend themselves to longitudinal scanning, where the exhaust lights will then be replaced by at least one exhaust valve fitted in the cylinder head of the low-pressure two-stroke cylinder.
The two-stage internal combustion engine, which is the subject of the present invention, will find use everywhere, where conventional internal combustion engines are currently used, in particular in road transport.
It is noted that the two-stroke internal combustion engines with reciprocating pistons, which have just been described, by way of example make it possible to increase the energy efficiency of the two-stroke internal combustion engine and with reciprocating piston compared to known engines. To achieve this goal, a two-stage thermodynamic cycle is carried out. This cycle includes a first compression, a second compression, a first expansion of the combined gases producing a usable mechanical work and finally a second expansion of the gases also producing a usable mechanical work. The air intake and the exhaust of the combined gases are carried out towards the end of the second expansion and at the start of the first compression according to the classic principle of the two-stroke internal combustion engine, where there is a sweep gases combusted by fresh air or air-fuel mixture while the piston is near its bottom dead center. This new cycle makes it possible first of all to increase the overall compression ratio and then the sweeping of the gases combined by air only. This is also possible in the petrol version, where petrol will be introduced between the compression stages.
In the case of the petrol version, the increase in the overall compression ratio requires intensive cooling between the two compression stages so as not to run the risk of premature detonation of the air-fuel mixture.
The high pressure oxidizing cylinders are only used to receive the air or the pre-compressed air-fuel mixture, to compress it the second time, to undergo combustion, to relax the combined gases the first time and finally to discharge these same gases under high pressure through the transfer tube (s).
The low-pressure two-stroke cylinder has the sole function of compressing and discharging fresh air, to receive the combined gases under high pressure and to participate in their second expansion, the exhaust of the combined gases followed by the scanning of the remaining gases by the fresh air coming towards the end of the second trigger when the piston is close to its bottom dead center.
The admission of fresh air into the low-pressure two-stroke cylinder is preferably done by means of scanning lights arranged in the cylinder liner so that they will be discovered by the piston towards the end of the stroke. of relaxation. The exhaust will be done either by an exhaust valve fitted in the cylinder head and we will speak of a longitudinal sweep, or by exhaust lights fitted in the cylinder liner so that the piston discovers them towards the end of the second trigger but before it discovers the scanning lights and in this case we will speak of a transverse scanning.
For the sweep to occur, the fresh air will advantageously be under a slight overpressure. This can be achieved either by any blower or by the classic principle of the two-stroke engine, called the "pump housing" where air is drawn into the housing. It is in this case that the jacket of the low-pressure two-stroke cylinder can be equipped with air intake lights towards the casing. These will only be discovered by the piston when it is close to its bottom dead center position. During its downward stroke, the volume downstream of the piston, that is to say the volume of the casing, decreases and the air therein is slightly compressed.
The main advantage over existing engines is increased fuel efficiency. For exchanger powers and maximum pressures which seem entirely acceptable, the calculations promise an increase in this efficiency of about 10 to 20% in the case of the petrol engine. This engine inherits an advantage from the conventional two-stroke engine, which is a specific power, that is to say a notable power / displacement ratio, without having the great defect of existing two-stroke engines, which is the driving fuel to the exhaust manifold during sweeping.
Another advantage of the new stepped two-stroke engine, proposed by the invention, compared to the existing two-stroke engines is the possibility of adjusting the power in several ways. Indeed, the throttle on suction, used until now, poses problems because, the sweeping pressure becoming too small, it leads to a significant dilution of the fresh air-fuel mixture so as to make combustion difficult. The two-stage internal combustion cycle allows, for example, to regulate the power at by means of a constriction at the level of the delivery pipes for precompressed air or also at the level of the pipes for introducing air or of a precompressed air-fuel mixture. In the latter case, the pressure in the heat exchanger will rise at partial speed which can be exploited to satisfy a sudden demand for power. In both cases, the sweep is not affected by the power setting.
The second compression ratio, i.e. the volumetric compression ratio of the high pressure oxidizing cylinder is relatively low (3 ... 6). The rebound is distributed over a complete revolution of the crankshaft. These two factors significantly reduce the unfeasible influence of a non-instantaneous combustion time. The compactness of the combustion chamber, which is in fact the dead space of the high pressure oxidizing cylinder, whose cubic capacity is relatively small and whose compression ratio is low, first of all limited, despite significant maximum pressures, mechanical stresses and then avoids an exaggerated thermal loss. It helps to avoid the rattling of gasoline combustion and probably increases the richness of spontaneous combustion. This latter advantage is also due to the second low compression ratio which prevents too rapid a drop in pressure and temperature after the piston has passed the top dead center.
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.
Yet another additional advantage is that the low pressure cylinder does not undergo combustion, therefore no sudden increases in pressure and temperature, which allows the use of materials other than those of current cylinders, which could be advantageous among other things in terms of lubrication and withstand even "dry" friction.

Claims

Procedure for producing an internal combustion engine of a type comprising at least three cylinders, each of which includes a work chamber whose volume is varied by the displacement in the cylinder of a piston between the upper neutral position and the lower neutral position under the effect of pressure forces generated at regular intervals in the said chamber, each cylinder having the means of admitting a gaseous fluid and evacuating combusted gases, the piston of each cylinder being linked to a crankshaft of the engine, according to which process at least one cylinder (1) is used to function as the low-pressure, two-stroke cylinder and two cylinders (2,3) to function as the four-stroke combustion cylinder, and causing the low-pressure cylinder piston to be displaced in a direction of movement opposite to that of the combustion cylinder, typified in that with every stroke of the low-pressure cylinder piston towards its upper neutral position, the gaseous fluid drawn in is forced out alternatively into one of the two combustion cylinders (2,3) by a separate channel in which the fluid is subjected to the action of a heat exchanger so that petrol may be added to the fluid between this heat exchanger (15) and the entry to the combustion cylinder (2,3) such that the combustion cylinder (2 or 3) in which the said fluid has been expelled is induced afterwards to execute successively intakes of the said fluid, compression of this fluid, a first expansion of the combusted gases, after ignition of this fluid or after spontaneous combustion of the fuel injected towards the end of the compression stroke and expulsion, during its travel from its lower neutral position towards its upper neutral position, of the combusted gases into the lower pressure cylinder in the course of the second of its expansion strokes, following that said expulsion of fluid out of the lower pressure cylinder into the combustion cylinder, with the purpose of a second expansion of combusted gases and their evacuation from the engine.
Engine to effect the procedure described in claim 1. in which the work chamber of the low-pressure cylinder (1) is capable of connection with an access channel (18) of gaseous fluid and an exhaust channel (19) of combusted gases and with the work chamber of each combustion cylinder (2,3) by a transfer channel (16 or 17) for combusted gases through the intermediary of a transfer valve (9 or 10) connected with the combustion cylinder (2 or 3), the pistons (4,5,6) of the low-pressure cylinders (1) and combustion cylinders (2,3) being linked to the crankshaft in such manner that the pistons (5,6) of the combustion cylinders (2,3), on the one hand, and the low-pressure cylinder piston, on the other hand, are displaced in opposite directions, distinguished in such a way that the work chamber of the low-pressure cylinder (1) is capable of reconnecting by an expulsion channel (12,13;12,14) of fluid in this work chamber, with the work chamber of each combustion cylinder through the intermediary of an expulsion valve (7) connected with the low-pressure cylinder (1) and through an introduction valve (8 or 11) connected with the combustion cylinder, such that each expulsion channel comprises a heat exchanger (15), and that these valves (7 to 11) are controlled in such a way that the said expulsion valve (7) remains open during the travel of the piston (4) of the low pressure cylinder (1) towards its upper neutral position, simultaneously with the introduction (8 or 11) of one of the two combustion cylinders (2 or 3) and that the transfer valve (9 or 10) of this combustion cylinder (2 or 3) is open during the second travel of the piston (4) of the low-pressure cylinder (1) towards its lower neutral position, after the intake of fluid into this cylinder.
Engine according to claim 2, typified in that the means of fuel injection are positioned in the part of the expulsion channel (13,14) linking the exit of the heat exchanger (15) to the entrance of the corresponding combustion cylinder.
Engine according to one of the claims 2 or 3, typified in that it comprises three cylinders (1 to 3), disposed in line, the two high-pressure combustion cylinders (2 and 3) positioned at the extremities of the crankshaft to which they are linked.
Engine according to one of the claims 2 or 3, typified in that it comprises five cylinders disposed in line, which are three high-pressure combustion cylinders and two low-pressure, two-stroke cylinders, two of the high-pressure cylinders positioned at the extremities of the crankshaft to which they are linked, the third high-pressure combustion cylinder positioned in the middle and capable of connecting with the two low-pressure, two-stroke cylinders adjacent respectively to at least a valve and a transfer manifold in order to transfer, after a second expansion stage, the combusted gases contained in the central high-pressure combustion cylinder into the two low-pressure cylinders connected with it, in a simultaneous manner.
Engine according to one of the claims 2 or 3, typified in that it comprises an uneven number, greater than five, of cylinders disposed in line such that two high-pressure combustion cylinders are positioned at the extremities of the crankshaft and that the other combustion cylinders are positioned between two low-pressure, two-stroke cylinders which shall be capable of connecting with the two low-pressure, two-stroke cylinders adjacent respectively to at least a valve and a transfer manifold in order to transfer, after the second expansion stage, the combusted gases contained in the high-pressure combustion cylinder into the two low-pressure cylinders connected with it, in a simultaneous manner.
Engine according to one of the claims 2 to 6, typified in that it comprises a heat exchanger (15) of which the entries (12) are capable of connecting with the work chambers of the low-pressure, two-stroke cylinders (1), through the aforementioned expulsion valves (7), and through the exits (13,14) of the work chambers of the high-pressure combustion cylinders (2,3) through the intermediary of the aforementioned introduction valves (8,11).
Engine according to one of the claims 2 to 7, typified in that the exchange passages of the work chambers of the high-pressure combustion cylinders (2,3) comprise the means of introducing fuel into the pre-compressed fluid according to the method of injection required or by means of carburettors, the work chambers of the high-pressure combustion cylinders being equipped with a means (26) of igniting the air-fuel mixture.
Engine according to claims 2 to 7, typified in that the work chambers of the high-pressure combustion cylinders (2,3) comprise the means of direct injection of fuel into the compressed air, towards the end of the compression stage in the cylinders, such that the fuel is spontaneously ignited.