EP0345436A1 - Two-stroke double piston engine - Google Patents

Abstract

In a two-stroke double piston engine, a piston (2, 3) runs in each of two adjacent cylinders (1a, 1b), a common combustion chamber (15) being formed. <??>In order to ensure that such an engine gives low exhaust emissions in combination with low consumption, a lean mixture is burnt, the complete combustion of which is made possible by the fact that a rotation of the fuel/air mixture or ignited mixture is produced in the common combustion chamber (15), with the result that this mixture burns rapidly and thoroughly. In addition, the two-stroke double piston engine can be designed for stratified charging, excellent separation between the lean component and the rich component of the mixture being effected by the centrally arranged partition wall (24) in the double cylinder (1). <IMAGE>

Description

The invention relates to a two-stroke twin-piston engine according to the preamble of claim 1, as has become known for example according to the Puch system.

The invention has for its object to develop a double-piston engine mentioned at the outset so that consumption can also be reduced if the exhaust gas emission values are reduced.

To achieve the object, the invention is characterized in that a rotation of the fuel-air mixture or the ignited mixture is generated in the common combustion chamber.

With the given technical teaching, the advantage is achieved that even lean mixtures burn out quickly, as a result of which low consumption is achieved with very low exhaust gas emissions.

With a mixture composition of lambda 1.3 and higher, the NOx are reduced so much that they comply with the regulations. In order to burn out such a lean mixture properly and quickly enough, a strong rotation in the combustion chamber is necessary. Only with such a combustion process runs as fast as with mixtures of lambda 0.9 - 1.0. This is necessary in order to achieve very low consumption with good performance.

The inventor already had experience with four-stroke engines with similarly designed combustion chambers. The consumption has been reduced by approx. 20% and is below 260 g / KWh from 120 km / h. At full load, it is between 2,000 - 5,000 rpm 240 - 245 g / KWh. The FTP 75 (CVS) test on a Fiat Ritmo 75 brought the following values with this combustion chamber and a mini catalytic converter:
HC: 0.32 - CO: 2.8 - NOx: 0.71 g / mile, consumption: 6.3 1/100 km = 37.1 M / GAL.

Consumption is also extremely low here, in the composite test 32% below the US regulation.

The exhaust gas values are 20 - 30% below the USA regulation. The ECE emissions regulations are undercut by 30 - 70%.

In a preferred embodiment of the present invention, the double-piston engine is designed as a two-stroke engine system Puch.

In the series version, the double-piston, two-stroke System Puch engine has no higher consumption than a four-stroke engine, since it has no fresh gas losses during charging and also has different control times for the inlet and outlet.

The same values can be achieved with such an engine as with a four-stroke engine with a combustion chamber with rapid rotation of the gas mixture before and during the combustion process.

• 1. Ein ruhiger Lauf des Motors wird mit drei Zylindern anstelle sechs Zylindern beim Viertakter erreicht.
• 2. Die Literleistung ist höher.
• 3. Der Zylinderkopf ohne Ventile hat eine kleinere Bauhöhe, ist sehr einfach aufgebaut und ist preiswert herzustellen.

However, the two-stroke engine has the following advantages:

• 1. The engine runs smoothly with three cylinders instead of six cylinders with the four-stroke engine.
• 2. The liter output is higher.
• 3. The cylinder head without valves has a smaller overall height, is very simple and is inexpensive to manufacture.

In summary, the following advantages result:
For the same performance, the engine is approx. 30% smaller, lighter and cheaper than a corresponding four-cylinder four-stroke engine and has the smooth running of a four-stroke six-cylinder engine.

When realizing the technical teaching according to the invention, it is important that a strong rotation of the fuel-air mixture or the ignited mixture is generated in the common combustion chamber by forming a longer pinch gap with the cylinder head and the cylinder head with the upper edge of the one piston outside this nip has the shape of an arc of a circle.

One of the pistons controlling the exhaust port therefore has on its side closest to the exhaust port an inclined line directed towards the cylinder head, which in a horizontal piston (with the engine standing vertically) extends across the entire width of the piston and extends across the top of the piston ends.

This comb-like upper piston edge is followed by a fillet in the piston crown, which in the top dead center position of both pistons forms a continuous surface with the adjacent piston crown of the piston, which controls the overflow slot.

This surface of the piston controlling the overflow slot is preferably likewise designed as a straight line and is arranged in the region of a recess which in turn opens into a fillet which in turn merges into a straight line, this straight line being part of a further pinch gap.

In the top dead center position, the piston controlling the outflow slot thus forms a first, long pinch gap, which leads to rapid ejection of the mixture enclosed in this pinch column leads towards the combustion chamber. Due to the egg-shaped shape of the upper cylinder wall, a strongly rotating flow is generated in the combustion chamber, which finds rounded, merging radii on all parts in contact with the mixture, so that the rotation does not encounter any significant flow resistances.

This fast rotating flow is reinforced by the right, shorter pinch gap; which also emits a nip flow in the direction of the rotation and thereby accelerates the rotation.

A further acceleration of the rotation takes place in that the ignition jet of the spark plug flows out of an outflow channel and the direction of this channel also takes place in the direction of the rotation, so that the rotation flow is in turn supported thereby.

In a second embodiment of the present invention, it is provided that instead of arranging the spark plug in a spark plug chamber with an outflow channel in front of it, a recess in which the spark plug is arranged is arranged in the piston which controls the outflow slot. The reason for this recess is again formed as a straight line, which is directed obliquely upwards and continues the upper cylinder wall. This recess in the piston crown of the left-hand piston in conjunction with the oblique straight line initially acts as a pinch gap. In addition, however, the ignition jet generated by the spark plug causes an additional acceleration of the ignited mixture leaving this pre-combustion chamber, so that this again results in a strong rotational flow.

In another embodiment of the present invention it is provided to generate a stratified charge of the incoming combustion air, which is particularly simple and inexpensive with the engine design according to the invention. It is only with the combustion chamber according to the invention for the double-piston engine and the rotation of the mixture provided according to the invention that a stratified charge is achieved which enables thorough mixing with the lean mixture after ignition.

Mixing of the stratified charge is thus avoided until ignition, with the richer mixture being ignited first, after which the lean mixture is only then mixed with the ignited richer mixture.

When designing the engine according to the invention without stratified charge, a second spark plug can be very important for the rapid burnout, while in the embodiment according to the invention with stratified charge the second spark plug provided in a modified exemplary embodiment can be omitted.

The subject matter of the present invention results not only from the subject matter of the individual patent claims, but also from the combination of the individual patent claims with one another.

All of the information and features disclosed in the documents, in particular the spatial configuration shown in the drawings, are claimed to be essential to the invention insofar as they are new to the prior art, individually or in combination.

In the following, the invention will be explained in more detail with reference to drawings showing several possible embodiments. Further features and advantages of the invention which are essential to the invention emerge from the drawings and their description.

• Figur 1: Schnitt durch eine erste Ausführungsform eines Zweitakt-­Doppelkolbenmotors im oberen Totpunkt der Kolben;
• Figur 2: Schnitt durch den gleichen Motor im unteren Totpunkt der Kolben;
• Figur 3: eine gegenüber Figur 1 abgewandelte Ausführungsform eines Doppelkolbenmotors.

Show it:

• Figure 1: Section through a first embodiment of a two-stroke double-piston engine in the top dead center of the pistons;
• Figure 2: Section through the same engine at the bottom dead center of the pistons;
• Figure 3: an alternative to Figure 1 modified embodiment of a double-piston engine.

According to FIG. 1, the two-stroke double-piston engine according to the exemplary embodiment consists of a double cylinder 1 in which the pistons 2, 3 run through a partition 24 fixed to the housing.

Through the inlet slot 4, fuel-air mixture is pressed into the left cylinder 1b during the charging process from the crank chamber. This mixture pushes the burned gases of the previous work cycle in front of it to the outlet slot 5, which is controlled by the right-hand piston 2. The outlet slot 5 is opened by the known control of the Puch motor rather than the inlet slot 4.

During the upward movement of the pistons 2, 3, the outlet slot 5 closes earlier than the inlet slot 4, thereby avoiding that fresh gases are lost, which is the case with normal two-stroke engines and leads to higher consumption there.

The spark plug 7 is located in the cylinder head 6. According to FIG. 1, this is seated in a prechamber 8 with an adjoining outflow channel 9, the longitudinal axis of the outflow channel 9 pointing in the direction of the rotation 20 of the fuel-air mixture generated in the combustion chamber 15.

The rotation shown in Figure 1 is achieved by the following design measures.

The left piston 3 has an oblique piston head, which is directed obliquely upward in the form of a straight line 25, the straight line 25 being parallel and at a short distance from the associated straight wall of the cylinder head 6 in the top dead center position, thereby forming a pinch gap 19 .

The straight line 25 on the piston crown of the cylinder 3 ends in a comb-like piston upper edge 10 extending in the horizontal direction, to which a fillet 26 in the piston crown of the piston 3 is connected.

The piston 2 controlling the outlet slot 5 also has a recess 27 in the piston crown next to the partition 24 fixed to the housing, the base of which is designed as a straight line 21.

This straight line 21 is directed obliquely downwards and continuously continues the contour of the fillet 26 of the left piston 3.

At the bottom of the recess 27, a groove 28 is machined in the piston 2, which forms a piston arch 12, which in turn runs into a straight line 29. The straight line 29 in connection with an assigned upper cylinder head wall forms a second, shorter pinch gap 18.

When the pistons 2 and 3 approach top dead center, a pinch gap 19 is formed between the top edge of the piston 10 and the cylinder head 6, from which the gas mixture flows out at a very high pressure in the direction 16 and generates a rotational flow in the combustion chamber 15. The rotation is generated by the shape of the cylinder arc 11, the piston arc 12 and of the deflection bend 13. It is also conveyed in the flow by escaping gases from the pinch gap 18. A further conveyance in the flow direction is brought about by the outflowing fuel gas from the spark plug chamber 8 via the outflow channel 9.

The embodiment of Figure 3 differs from that of FIGS. 1 and 2 only in that a recess 30 is arranged in the left piston 3, the bottom of which is formed as a straight line 22, which in turn is approximately parallel to the upper, just executed cylinder head wall of the Cylinder head 6 is. As a result, a pre-combustion chamber 14 is formed for a spark plug 7 arranged in the cylinder head 6.

When ignited, the mixture burns in the pre-combustion chamber 14 and flows at high pressure and speed in the direction 16 into the main combustion chamber 15a, where a rotation also occurs in this way.

This rotation is further extended or supported by the ignition of a second spark plug 31. The ignition of this second spark plug 31 takes place only later in comparison to the ignition of the first spark plug 7, namely only when the mixture ignited by the first spark plug 7 has reached the region approaches the second spark plug 31.

In the following, the present invention now describes the possibility of generating a stratified charge in all of the embodiments shown in FIGS. 1 to 3, which brings about unexpected advantages with the engine concept according to the invention.

For this purpose, an injection nozzle 33 is arranged in the channel of the inlet slot 4 so that it injects fuel into the channel at a certain point in time. The injection time is controlled so that the fuel in the overflowing air quantity only in the second part of the total amount of air is injected.

This means that the fuel is then injected into the channel of the inlet slot 4 when part of the inflowing air has already passed the inlet slot 4.

In a preferred embodiment of this idea, it is preferred if the fuel is only injected into the channel of the inlet slot 4 when the air has already passed the inlet slot 4 by a quarter to a half of the total amount of air.

This measure results in that the first part of the overflowing amount of air is without fuel and push the combustion gases in front of them in the direction of the outlet slot 5 and convey them out of this outlet slot 5. This prevents even the smallest amounts of fuel from entering the exhaust during the flushing process.

A stratified charge in the usual two-stroke engines has already been proposed (DE-OS 36 19 794).

In these known two-stroke engines, however, stratified charge is hardly achieved that there is a direct connection across the open cylinder from the inlet slot to the outlet slot.

This is avoided in the invention. Here is the partition wall 24 between the inlet slot 4 and the outlet slot 5. The overflowing amount of air then goes up in the left cylinder 1b, there over the partition 24 down into the right cylinder 1a.

This is essentially the air without fuel at the end of the purge cycle in the cylinder 1a, and the fueled air is in cylinder 1b.

During the compression stroke (pistons 2 and 3 or 3a go up), the richer mixture is in the area of the nip 19 or the recess 30. There it is ignited by the spark plug 7 and flows in the directions 16 and 32 into the other fuel-free ones or lean part of the combustion air. In this way, the ignited mixture rotates in directions 16 and 20.

This results in thorough mixing and burning through of the overall mixture, which overall can be very lean since the ignition takes place in the region of the recess 30 in the case of the leaner, richer mixture. This stratified charge makes it possible to run even leaner mixtures than is possible with lean-burn engines without stratified charge. In this way, the NOx content is reduced even further.

When the engine is stratified, as described above, the second spark plug 31 can be omitted.

In the above description it was stated as a preferred embodiment that the right piston 2 with the specific bottom shape described is assigned to the outlet slot 5, while the left piston 3 with its differently shaped bottom shape is assigned to the inlet slot 4.

In another embodiment of the present invention, it can also be the other way round, namely that pistons 2 and 3 are interchanged with one another, inlet slot 4 and outlet slot 5 according to FIG.

DRAWING LEGEND

• 1 double cylinder
• 1a right cylinder
• 1b left cylinder
• 2 pistons
• 3 pistons 3a pistons
• 4 inlet slot
• 5 outlet slot
• 6 cylinder head
• 7 spark plug
• 8 spark plug chamber
• 9 outflow channel
• 10 piston top edge
• 11 arcs
• 12 piston elbows
• 13 deflection bend
• 14 pre-combustion chamber
• 15 combustion chamber
• 15a combustion chamber
• 16 direction
• 18 Pinch gap on the right
• 19 Pinch gap on the left
• 20 rotation
• 21 straight
• 22 Straight
• 23 crank chamber
• 24 partition
• 25 straight
• 26 fillet
• 27 recess
• 28 fillet
• 29 Straight
• 30 recess
• 31 spark plug
• 32 flow circular arc
• 33 injector

Claims (14)

1. Two-stroke double-piston engine, in each of which a piston runs in two cylinders lying next to each other and a common combustion chamber, the two pistons forming a common combustion chamber with the cylinder head at top dead center, characterized in that in the common combustion chamber (15) there is a rotation the fuel-air mixture or the ignited mixture is generated. 2. Two-stroke double-piston engine according to claim 1, characterized in that with the upper edge (10) of a piston (3,3a) a longer pinch gap (19) with the cylinder head (6) is formed and the cylinder head (6) outside of this pinch gap Has approximately the shape of an arc (11). 3. Two-stroke twin-piston engine according to claim 1, characterized in that a piston arc (12) is arranged in the piston (2), which represents the extension of the circular arc (11) and then runs out into a straight line (21). 4. Two-stroke double-piston engine according to claim 1, characterized in that a deflection bend (13) is arranged in the piston (3,3a). 5. Two-stroke double-piston engine according to claim 2, characterized in that the circular arc (11) in the double cylinder (1) with the piston arc (12), the upward straight line (21) and the deflection arc (13) of the piston (3,3a ) form almost a flow oval. 6. Two-stroke double-piston engine according to one of claims 1-3, characterized in that the spark plug (7) in a chamber (8) with an outflow channel (9) is arranged and the outflow channel (9) points in the direction of the rotational flow (20) in the flow oval. 7. Two-stroke double-piston engine according to one of claims 1-6, characterized in that a recess (30) is arranged on the surface of the piston (3a), which has a pre-combustion chamber (14) at the top dead center of the piston with the cylinder head (6). forms, the ignition jet of which causes the rotational flow (20) in the combustion chamber (15). 8. Two-stroke double-piston engine according to one of claims 1- 7, characterized in that the spark plug (7) is in the region of the pre-combustion chamber (l4). 9. Two-stroke double-piston engine according to one of claims 1-8, characterized in that a second spark plug (31) is arranged in the region of the flow arc (32) in the cylinder head (6). 10. Two-stroke double-piston engine according to claim 9, characterized in that the second spark plug (31) ignites later than the first spark plug (7). 11. Two-stroke twin-piston engine according to one of claims 1-10, characterized in that the outlet slot (5) controlling piston (2) has the piston arch (12) and the straight line (21) and that the inlet slot (4) controlling piston (3, 3a) which has the oblique piston top edge (10) producing the pinch gap (19) or the recess (straight line 22) forming the pre-combustion chamber (14). 12. Two-stroke double-piston engine according to one of claims 1-11, characterized in that the fuel is injected into the channel of the inlet slot (4). 13. Two-stroke double-piston engine according to one of claims 1-12, characterized in that the fuel is then injected into the channel of the inlet slot (4) when part of the inflowing air has already passed the inlet slot (4). 14. Two-stroke twin-piston engine according to claim 13, characterized in that the fuel is only injected into the channel of the inlet slot (4) when the air has already passed the inlet slot (4) by a quarter to a half of the total amount of air .

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