DE102022000509A1 - Process for improving gas exchange in internal combustion engines and internal combustion engines suitable for this - Google Patents

Abstract

The invention relates to internal combustion engines and to a method for operating internal combustion engines in which first exhaust gas and then fresh gas are pushed into the cylinders by changing the phases of the opening and closing times of valves with respect to the crankshaft. In a cylinder, there is an exhaust gas layer above the piston head and a fresh gas layer above it, the relationship between which determines the performance of the internal combustion engine. The amount of fresh gas that is pushed in is determined by the amount of exhaust gas previously sucked in and not by the vacuum generated by the throttle valve. The gas exchange losses caused by the throttle valve are eliminated. Since the components of the fresh gas are in a stoichiometric ratio (lambda=1) to one another in the gasoline engines according to the invention, both with intake manifold and direct injection, the harmful exhaust gas components can be almost completely reduced by using a 3-way catalytic converter become. In diesel engines, the excess air is significantly reduced, so that the reduction of nitrogen oxides is significantly simplified.

Description

The invention relates to the optimization of the gas exchange of internal combustion engines with changing performance, for example by changing the phases of the intake and exhaust valves in relation to the crankshaft. This makes it possible, separately from each other, to insert first inert gas, such as exhaust gas, and then fresh gas into the cylinder. This means that petrol engines can be de-throttled and the excess air in diesel engines can be significantly reduced.

In the last few decades, gas exchange and thus mixture formation have been significantly improved in internal combustion engines.

In conventional internal combustion engines, two valves were installed per cylinder. The use of four valves made it possible to increase the cross-sectional area through which the gas exchange took place, while at the same time reducing the mass of the individual valves. This reduced the inertial forces and improved the speed stability. In addition, with four valves, the spark plug in petrol engines and the injection nozzle in diesel engines could be arranged centrally above the combustion chamber, which significantly improved combustion and thus reduced fuel consumption.

A distinction is made between two types of mixture formation: external, which takes place outside the cylinder and was typical of early Otto engines, and internal, in which mixture formation takes place inside the cylinder and is an inherent property of a diesel engine. In the course of further development, internal mixture formation was also introduced in petrol engines.

In the early petrol engines, the mixture was formed by means of a carburetor, which was located in front of the throttle valve. The mixture could be improved by replacing it with an injection valve. With increased pressure, the fuel could now be injected into the air in a finely atomized form. Due to the increased surface area of the injected fuel, it forgot faster, which led to better mixing with the air, more complete combustion and more favorable exhaust gas values.

In the course of development, the mixture formation was moved to the intake manifolds. A separate injection valve was assigned to each cylinder, which was usually located directly in front of the intake valve. The injection took place shortly before the inlet valve, which was still closed at the start of injection. The time elapsed during the intake and compression of the fuel-air mixture was sufficient to produce a homogeneous mixture.

A characteristic variable of a fuel-air mixture is the ratio of the proportion of fuel to the proportion of air. This ratio is called stoichiometric when all the oxygen in the air is consumed during complete combustion of the fuel contained in the mixture. If the proportion of fuel is larger, it cannot be burned completely. The mixture is referred to as "rich", it is unwilling to ignite and even incapable of igniting if the fuel content is too high. If the proportion of air is greater, the oxygen contained in it is not burned completely, the mixture is referred to as “lean”, it is unwilling to ignite and, if the proportion of air is too large, it cannot be ignited.

The lambda parameter was introduced to describe the composition of a fuel-air mixture. This is the ratio of the actual air mass supplied for combustion to the air mass required for complete combustion: $$\text{lambda}=\text{Air mass in kg}/\text{theoretical air requirement in kg}$$

If lambda > 1, then the air mass is greater than the theoretical air requirement, so the mixture is lean. If lambda < 1, the air mass supplied is less than the theoretical air requirement, and the mixture is consequently rich. When lambda = 1, the mixture is stoichiometric.

In an internal combustion engine at operating temperature, the fuel, which mainly consists of hydrocarbons (HC) in a stoichiometric ratio to air, is burned under ideal conditions to form carbon dioxide (CO ₂ ) and water (H ₂ O). Due to the incomplete combustion of the fuel under real conditions, however, carbon monoxide (CO), unburned hydrocarbons (HC) and nitrogen oxides (NOx) are also produced. With an air/fuel ratio of lambda = 1, these pollutants can be almost completely converted into nitrogen (N ₂ ), carbon dioxide (CO ₂ ) and water (H ₂ O) by a 3-way catalytic converter. In this operating state, the internal combustion engine is practically emission-free.

In temporary operating states with an air/fuel ratio lambda < 1, such as during a cold start and in the warm-up phase of the engine, hydrocarbons (HC) and carbon monoxide (CO) are produced in the exhaust gas. Suitable measures can be taken to reduce these pollutants in the exhaust gas during these operating states until the 3-way catalytic converter has reached the temperature required to convert these pollutants into carbon dioxide (CO ₂ ) and water (H ₂ O).

In operating modes with a lambda air ratio > 1, the nitrogen oxides (NOx) cannot be reduced by a 3-way catalytic converter because of the excess air. A NOx storage catalytic converter is used for after-treatment, which adsorbs the nitrogen oxides in the lean phase. After the storage capacity has been exhausted, the nitrogen oxides NOx are released again by enrichment and converted into N ₂ , H ₂ O and CO ₂ together with the unburned exhaust gas components HC and CO. In order to extend the lean operating time of the catalytic converter, exhaust gas recirculation (EGR) is used, in which exhaust gas is mixed with the fresh gas. This reduces the amount of air in the fresh gas and the inert exhaust gas reduces the combustion temperature. Both lead to an increase in the lean operating time of the NOx storage catalytic converter.

In conventional petrol engines with external mixture formation, the quantity of mixture is adjusted to the power requirement of the engine via the throttle valve. Since there is less fuel requirement in the lower and middle engine speed and power range, the throttle valve has to be partially closed, which leads to a vacuum in the cylinder and thus to higher gas exchange losses and higher fuel consumption. At full load, the engine is operated with an open throttle.

Since the beginning of the century, most manufacturers have switched to using gasoline engines with internal mixture formation, in which pure air is introduced into the combustion chamber and only there is the fuel injected into the air under high pressure through an injection nozzle. This direct injection into the cylinder leads to a significant reduction in fuel consumption and an increase in performance. There are essentially two types of gasoline direct injection, homogeneous and stratified operation.

In homogeneous operation, the fuel is injected during the intake stroke and the amount of fuel is metered in such a way that the mixture is formed in a stoichiometric ratio (lambda = 1) when the engine is warm. The period of time during which the fuel-air mixture is sucked in and compressed is sufficient to produce a homogeneous mixture. As with the external mixture formation, the mixture quantity is adjusted to the power requirement of the engine via the throttle valve, which causes high fuel consumption in low-load operation. However, homogeneous operation has prevailed because in operation with lambda = 1, the harmful residual gases can be reduced almost completely with a 3-way catalytic converter and a NOx storage catalytic converter is not required.

In stratified charge operation, the full amount of air is always introduced into the combustion chamber and the fuel is injected during compression in such a way that an ignitable mixture forms in the area of the spark plug, which is surrounded by the remaining air. The amount of fuel injected is determined by the torque required in each case. Since the air is not throttled, the fuel-air mixture is lean and the excess air prevents the conversion of the nitrogen oxides by a 3-way catalytic converter. Exhaust gas cleaning with an additional NOx storage catalytic converter is therefore necessary, and this additional effort means that this shift drive does not pay off. At high speeds, it is also not possible to generate an ignitable mixture in the area of the spark plug in the time available. A homogeneous combustion process with a partially closed throttle valve is therefore used. However, this requires a not inconsiderable control effort.

A diesel engine always works with excess air. At full load, the excess air is low (lambda = approx. 1.3), while idling and in the partial load range it is very high. The proportion of hydrocarbons is lower and the proportion of nitrogen oxides is greater than in a petrol engine. Exhaust gas recirculation (EGR) is used to reduce the proportion of nitrogen oxides in the exhaust gases. Due to the low valve overlap, the internal exhaust gas recirculation is meaningless and external exhaust gas recirculation is used, in which an additional exhaust pipe is connected to the exhaust manifold, which directs the exhaust gases into the intake pipe via a control valve, where they are mixed with the fresh air. This reduces the proportion of air in the fuel-air mixture and significantly fewer nitrogen oxides are produced, but their reduction is necessary.

In diesel engines, the exhaust gases are first passed through the oxidation catalytic converter for exhaust gas treatment, where the unburned hydrocarbons (HC) and carbon monoxide (CO) oxidize to form carbon dioxide (CO ₂ ) and water vapor (H ₂ O). Due to the high residual oxygen content, the nitrogen oxides cannot be reduced, but NO is oxidized to NO ₂ , so that the ratio of NO ₂ to NO is increased, which is important for the function of some downstream components (particle filter, NOx storage catalytic converter, SCR catalytic converter). is.

The exhaust gas then flows through the diesel particulate filter where it is efficiently filtered. The soot particles produced by the combustion slowly clog the pores of the filter walls, increase the back pressure and must be burned to regenerate the filter. This requires an increased temperature, but can also be achieved with lower temperatures if additives are used The ash from additives, engine oil and fuel residues also slowly clogs the filter and increases the back pressure. If a defined value is exceeded, mechanical cleaning must be carried out.

After exiting the diesel particulate filter, there are still nitrogen oxides in the exhaust gas that must be reduced. In engines with smaller displacements, NOx storage catalytic converters are used in which the nitrogen oxides are stored on the surface of the catalytic converter. The NOx storage catalytic converters are regenerated at successive time intervals by enriching the exhaust gases. The nitrogen oxides are reduced to nitrogen and water. The low storage capacity of these catalytic converters limits their use to smaller displacements.

The continuously working SCR catalytic converters are used in engines with large displacements. Part of this SCR system is a dosing device that is supplied from an Adblue tank and finely atomized Adblue (aqueous solution of urea and water) is sprayed into a hydrolysis section, where ammonia and carbon dioxide are produced by heating. After leaving the diesel particulate filter, the exhaust gas flows into this hydrolysis section, where it is mixed with the ammonia and carbon dioxide using a mixer and then fed into the SCR catalytic converter. There, the nitrogen oxides in the exhaust gas react with the ammonia to form nitrogen and water.

A blocking catalytic converter is located behind the SCR catalytic converter, which prevents possible ammonia emissions into the outside air and converts the carbon monoxide produced during the regeneration of the diesel particulate filter into carbon dioxide.

The object of the invention is to decisively improve the gas exchange of internal combustion engines.

This problem is solved by a method for operating an internal combustion engine in which two separate gases or gas mixtures are pushed into the cylinder during the intake process, one of which consists of an inert gas and the other of fresh gas or a precursor of fresh gas, see above that in the cylinder there is a layer of inert gas and a layer of fresh gas or a precursor of fresh gas.

In the context of this description, an inert gas is to be understood as meaning a gas or gas mixture with such a composition that no combustion can take place under the operating conditions of the internal combustion engine. A non-flammable gas mixture is preferably used, in particular exhaust gas.

In the context of this description, fresh gas is to be understood as meaning a gas or gas mixture with such a composition that combustion can take place under the operating conditions of the internal combustion engine.

A preliminary stage of fresh gas is understood to mean a gas or gas mixture which, after being introduced into the cylinder through the addition of fuel, has such a composition that combustion can take place under the operating conditions of the internal combustion engine.

The fresh gas is preferably a mixture of air and fuel or a mixture of air, fuel and exhaust gas.

Preferably, the fresh gas precursor is air.

Preferred variants of the method are presented in subclaims 2 to 6.

In a particularly preferred variant of the method according to the invention, the ratio of inert gas and fresh gas or the preliminary stage of fresh gas to one another is determined by the instantaneous power requirement; in this way a negative pressure in the cylinder is avoided.

In a further particularly preferred variant of the method according to the invention, the fresh gas consists of a stoichiometric mixture of air and fuel.

In a further particularly preferred variant of the method according to the invention, air, into which fuel is injected, is present in the cylinder as a preliminary stage of fresh gas. The intake air and the injected fuel preferably form a stoichiometric mixture.

The invention also relates to internal combustion engines that are equipped with at least one cylinder, valves, pistons and a crankshaft and in which the valves are set so that during the intake process first inert gas and then fresh gas or a precursor of fresh gas is pushed into the cylinder that in the cylinder there is a layer of inert gas and a layer of fresh gas or a precursor of fresh gas.

Preferred variants of the internal combustion engine according to the invention are presented in subclaims 8 to 10.

The valves can be adjusted by changing the phases of the opening and closing times with respect to the crankshaft, for example by changing the phases of the camshafts with respect to the crankshaft. Other adjustment options are also possible, for example electronic regulation of the opening and closing times.

The internal combustion engine according to the invention is preferably a two-stroke Otto engine, a four-stroke Otto engine or a diesel engine.

Among other things, a two-stroke gasoline engine is also preferred in which valves for the intake of fresh gas and valves for the intake of exhaust gas are located at the upper end of the cylinder, and in which slots are located at the lower end of the cylinder through which exhaust gas is expelled.

In a preferred variant, in Otto engines with external mixture formation, exhaust gas is introduced first and then the fuel-air mixture is introduced into the cylinder, with the ratio of both gas components (i.e. inert gas to fresh gas) being regulated in such a way that complete combustion of the fuel takes place currently required performance guaranteed. Since the fuel-air mixture is in a stoichiometric ratio, there is no excess air during combustion and hardly any nitrogen oxides are formed. By sucking in exhaust gas, a vacuum in the cylinder is not required to regulate the amount of fuel-air mixture, a throttle valve is not required and the charge losses are significantly reduced.

In a further preferred variant, in engines with internal mixture formation, first exhaust gas and then air is introduced into the cylinder, with fuel being injected in a stoichiometric ratio in the Otto engine and with lambda=approx. 1.3 in the diesel engine. Here, too, the throttle valve can be dispensed with in the petrol engine and the formation of nitrogen oxides can be almost completely prevented. A small amount of excess air is unavoidable in a diesel engine.

The principle of reducing the formation of nitrogen oxides by introducing exhaust gas into the cylinder and bringing about dethrottling in petrol engines is carried out in today's engines by means of exhaust gas recirculation (EGR). However, since the exhaust gas is mixed with the fresh gas or the air, this affects the combustion and there is a limit to the amount of exhaust gas mixed in. As a result, petrol engines can only be partially de-throttled and the formation of nitrogen oxides in petrol or diesel engines can only be partially avoided.

In the case of the exhaust gas intake (AGA) according to the invention, the exhaust gas is not mixed with the fresh gas or the air and there is no limit to the intake exhaust gas quantity. The petrol engine can be completely de-throttled and operated without excess air.

With the exhaust gas intake (AGA), an exhaust gas charge is first sucked in, which is stored above the piston crown, and then a fresh gas or air charge, which fills the space above up to the cylinder head.

The exhaust gas intake (AGA) can be implemented according to the invention, for example, by adjusting the angular position of a camshaft relative to the crankshaft. To do this, stepless angular position adjusters can be used (e.g. from the VANOS brand from BMW) which fulfill this task using helical gearing or vane cells. The phases of the valves are also adjusted synchronously with the angular position of the camshaft. With two angle adjusters installed one behind the other or acting in parallel on two camshafts, you can double the adjustment angle and the adjustment speed. Other technical solutions are also possible.

The functioning of the exhaust gas intake (AGA) is explained using the control diagrams of a 4-stroke petrol engine, a 4-stroke diesel engine and a 2-stroke petrol engine.

1

Drehrichtung Kurbelwelle

2

oberer Totpunkt (OT)

3

unterer Totpunkt (UT)

4

Zündzeitpunkt

5

Ansaugen

6

Verdichten

7

Verbrennen

8

Ausstoßen

9

Ansaugen Abgas

10

Trennmarkierungen

11

1. Einlassventil

12

2. Einlassventil

13

1. Auslassventil

14

2. Auslassventil

15

Einlassventile Frischgas

16

Einlassventile Abgas

17

Auslassschlitze

18

Vorauslass

The abbreviations used mean:

1

Direction of rotation of the crankshaft

2

top dead center (TDC)

3

bottom dead center (UT)

4

ignition timing

5

suction

6

compacting

7

Burn

8th

expel

9

intake exhaust gas

10

Separation marks

11

1. Inlet valve

12

2. Inlet valve

13

1. Exhaust valve

14

2. Exhaust valve

15

Fresh gas inlet valves

16

Intake valves exhaust

17

exhaust slots

18

advance

The control diagram for a 4-stroke engine is represented by a spiral diagram consisting of two merging circles and sweeping a total angle of 720°, corresponding to the two crankshaft revolutions of the working cycle. On the solid line of this diagram, the individual takes suction (5), compression (6), combustion (7) and ejection (8) are separated from each other by separating marks (10).

In the control diagram for idling, between the exhaust (8) and intake (5) strokes there is also the exhaust gas intake (9) work step. The valves actuated at these crankshaft angles are indicated on the separation marks. The directional arrows indicate the function of the valves. Arrows pointing away from the separation marks indicate an opening valve, arrows pointing to the separation marks indicate a closing valve.

• 1 zeigt das Steuerdiagramm bei Volllast. Die beiden Nockenwellen werden synchron von der Kurbelwelle angetrieben, die Ventilüberschneidung der Einlassvon und Auslassventile am OT ist klein und die Einlassventile schliessen weit nach dem UT.
• 2 zeigt das Steuerdiagramm bei Leerlauf. Die Nockenwelle welche das 1. Auslassventil (13) steuert wird synchron von der Kurbelwelle angetrieben, während die zweite um 60 KW° phasenverzögert angetrieben wird. Das 2. Auslassventil (14) schließt und die beiden Einlassventile (11), (12) öffnen weit nach OT. Dadurch wird zuerst Abgas und anschließend Frischgas angesaugt. Am UT befindet sich folglich oberhalb des Kolbenbodens eine Schicht Abgas und darüber eine Schicht Frischgas. Bewegt sich der Kolben über den UT hinweg und bewegt sich dann in Richtung des OT, dann wird ein Teil des Frischgases zurück in den Einlasskanal geschoben, da durch die Phasenverschiebung der Nockenwelle bezüglich der Kurbelwelle die Einlassventile (11), (12) sehr viel weiter hinter dem UT schließen. Gleichzeitig setzt die Kompression später ein. Die beschriebene Abgasansaugung (AGA) kann auch bei Einspritz-Ottomotoren eingesetzt werden, statt Frischgas wird nunmehr Luft angesaugt. Mit Hilfe des Winkellagenverstellers läßt sich die Frischgasmenge im Leerlauf einstellen und mit einem Bowdenzug kann man, beginnend beim Leerlauf, ohne den Rückgriff auf eine Elektronik, die Frischgasmenge stufenlos dem Leistungsbedarf des Motors anpassen. Der untersuchte 4-Takt-Dieselmotor verfügt über 2 Einlass- und 2 Auslassventile. Das 1. Einlassventil (11) und das 1. Auslassventil (13) werden von einer mit der Kurbelwelle synchron umlaufenden Nockenwelle gesteuert. Das 2. Einlassventil (12) und das 2. Auslassventil (14) werden von einer Nockenwelle gesteuert deren Phasenlage zur Kurbelwelle stufenlos verändert werden kann.
• 3 zeigt das Steuerdiagramm bei Volllast. Die Ventilüberschneidung von Einlass und Auslass am OT ist gering und der Einlass schließt weit hinter dem UT. Der Einlass wird insgesamt von den beiden Einlassventilen (11) und (12) gesteuert, die sich im Bereich zwischen 90° KW und 140° KW nach OT überschneiden. Das 1. Einlassventil (11) öffnet bei 90° KW nach OT und das 2. Einlassventil (12) schließt bei 140° KW nach OT.
• 4 zeigt die Verhältnisse im Leerlauf. Die Steuerzeiten des 2. Einlassventils (12) und des 2. Auslassventils (14) haben sich um 100° KW in Drehrichtung verschoben, die Einlassventile (11) und (12) arbeiten jetzt synchron und öffnen 90° KW nach OT und das 2. Auslassventil (14) schließt 110° KW nach OT. Aus dem Steuerdiagramrn sieht man, dass zuerst Abgas und anschließend Luft angesaugt wird, wobei bei der Aufwärtsbewegung des Kolbens nach UT wieder ein Teil der Luft aus dem Zylinder geschoben wird. Eine Verringerung der Kompression findet nicht statt, da sowohl bei Volllast wie auch bei Leerlauf, die beiden Einlassventile beim gleichen KW-Winkel nach UT geschlossen sind. Der untersuchte 2-Takt-Ottomotor verfügt am oberen Zylinderende über Ventile für den Einlass von Frischgas und Abgas und am unteren Zylinderende über Schlitze für den Auslass. Die hiermit bedingte Gleichstromspülung in der Zylinderachse, das in der selben Richtung expandierende Verbrennungsgas, sowie die großen Strömungsquerschnitte beim Ein- und Auslass bedingen sehr geringe Strömungsverluste. Die maximale Drehzahl ist ca. halb so hoch wie die eines üblichen 4-Takt Ottomotors, Leistungsgewicht und Wärmebelastung sind folglich diesem sehr ähnlich. Der gezielte Betrieb mit niedrigeren Drehzahlen führt zu günstigeren spezifischen Kraftstoffverbräuchen und verlängert entscheidend die für den Gasaustausch zur Verfügung stehenden Zeit. Beim Einlass wird zuerst Abgas und dann Frischgas in den Zylinder eingeschoben, in einem Verhältnis zueinander, das dem Leistungsbedarf des Motors entspricht. Die Einleitung von Abgasen erübrigt die Drosselung des Frischgases. Der Gasaustausch erfolgt mittels der kinetischen Energie der ausströmenden Abgase und eventuell eines zusätzlichen Gebläses.
• 5 zeigt das Steuerdiagramm bei Volllast. Das kurz vor dem OT entzündete Frischgas verbrennt und drückt den Kolben abwärts, bis nach einer definierten Wegstrecke die Auslassschlitze (17) freigegeben werden. Bei ausreichendem Vorauslass (18) sinkt der Druck in dem Zylinder schnell ab und durch die kinetische Energie des ausströmenden Abgases wird das Frischgas nach Öffnung der Einlassventile (15) in den Zylinder gesaugt. Nach Überschreitung des UT bewegt sich der Kolben wieder aufwärts und schließt die Auslassschlitze (17). Die Einlassventile für das Frischgas (15) werden mit einer zeitlichen Verzögerung geschlossen, um dem Frischgas ein Nachströmen in den Zylinder zu ermöglichen und so die Füllung zu verbessern.
• 6 zeigt das Steuerdiagramm bei Leerlauf. Hier werden nach der Abwärtsbewegung des Kolbens, der Freigabe der Auslassschlitze (17) und nach dem Vorauslass (18) zuerst die Einlassventile für das Abgas (16) geöffnet. Nachdem in den Zylinder eine definierte Menge an Abgas eingeströmt ist, schliessen sich die zugehörigen Einlassventile (16), nachdem kurz davor die Einlassventile für das Frischgas (15) geöffnet wurden. Die angesaugte Frischgasmenge wird durch den Leerlaufbetrieb bestimmt und durch die angesaugten Abgase verhindert man die Drosselung der Frischgase. Anhand des Arbeitsspiels eines 4-Takt-Ottomotors mit Abgasansaugung (AGA) wird die Funktionsweise im Leerlauf dargestellt. Die bezeichneten Teile sind: Einlassventil (21), Auslassventil (22), Zündkerze (23), Kolben (24), Zylinder (25), Pleuelstange (26) und Kurbelwelle (27). Der Pfeil gibt die Drehrichtung der Kurbelwelle (1) vor, (2) ist der obere Totpunkt (OT) und (3) der untere Totpunkt (UT).
• Die 7 bis 12 geben die Funktionsweise der vier Takte wieder:
• 7: Die Ansaugung (1. Takt) hat begonnen, der Kolben (24) befindet sich 60° KW nach OT, das Einlassventil (21) hat gerade geöffnet, das Auslassventil (22) ist geschlossen und der Zylinder (25) ist mit altem Abgas (29) aus dem vorangegangenen Arbeitsspiel gefüllt.
• 8: Die Ansaugung ist beendet, der Kolben befindet sich 20° KW nach UT, das Auslassventil (22) ist geschlossen, das Einlassventil (21) geöffnet, und in den oberen Bereich des Zylinders ist Frischgas (28) eingeströmt. Im unteren Bereich des Zylinders befindet sich eine Schicht altes Abgas (29).
• 9: Der Kolben befindet sich 90° KW nach UT und hat gerade einen Teil des Frischgases (28) zurück in das Ansaugrohr geschoben. Das Einlassventil schließt bei ca. 100° KW nach UT und die Verdichtung (2. Takt) beginnt.
• 10: Der Kolben befindet sich 20° KW vor OT und das Frischgas (28) wird gerade gezündet. Die oberhalb des Kolbenbodens liegende Abgasschicht (29) ist inert und ist an der Verbrennung nicht beteiligt.
• 11: Das Frischgas verbrennt und leistet Arbeit (3. Takt). Im Zylinder befinden sich zwei Abgaswolken, eine alte (29) über dem Kolbenboden, die aus vorherigen Arbeitsspielen stammt, und eine frische (30) darüber liegende, die gerade abbrennt.
• 12: Der Kolben befindet sich 50° KW nach UT, bewegt sich aufwärts und schiebt die Abgase aus. Zuerst wird das frische Abgas (30) ausgeschoben und anschließend das alte Abgas (29), das beim folgenden Arbeitsspiel im 1. Takt wieder in den Zylinder eingesaugt wird. Über einen Bypass am Auslassrohr kann dieses Abgas gekühlt werden.

The examined 4-stroke gasoline engine has 2 intake and 2 exhaust valves. The first exhaust valve (13) is controlled by a camshaft rotating synchronously with the crankshaft. The second exhaust valve (14) and the two intake valves (11) and (12) are jointly controlled by a camshaft, the phase of which with respect to the crankshaft can be continuously varied so that the engine operation can be adapted to the load requirements.

• 1 shows the control diagram at full load. The two camshafts are driven synchronously by the crankshaft, the valve overlap of the intake and exhaust valves at TDC is small and the intake valves close well after BDC.
• 2 shows the control diagram at idle. The camshaft which controls the 1st exhaust valve (13) is driven synchronously by the crankshaft, while the second is driven with a phase delay of 60 KW°. The 2nd outlet valve (14) closes and the two inlet valves (11), (12) open well after TDC. As a result, exhaust gas is sucked in first and then fresh gas. Consequently, at BDC there is a layer of exhaust gas above the piston crown and a layer of fresh gas above it. If the piston moves past BDC and then moves in the direction of TDC, part of the fresh gas is pushed back into the intake port because the phase shift of the camshaft with respect to the crankshaft causes the intake valves (11), (12) to move much further close behind the UT. At the same time, the compression sets in later. The exhaust gas intake (AGA) described can also be used with injection gasoline engines, instead of fresh gas air is now sucked in. With the help of the angular position adjuster, the amount of fresh gas can be adjusted when idling and with a Bowden cable, starting with idling, the amount of fresh gas can be infinitely adjusted to the power requirement of the engine without resorting to electronics. The examined 4-stroke diesel engine has 2 intake and 2 exhaust valves. The 1st intake valve (11) and the 1st exhaust valve (13) are controlled by a camshaft rotating synchronously with the crankshaft. The 2nd inlet valve (12) and the 2nd outlet valve (14) are controlled by a camshaft whose phase position to the crankshaft can be changed steplessly.
• 3 shows the control diagram at full load. Intake and exhaust valve overlap at TDC is low and intake closes well past BDC. The intake is controlled overall by the two intake valves (11) and (12), which overlap in the range between 90° CA and 140° CA after TDC. The 1st inlet valve (11) opens at 90° CA after TDC and the 2nd inlet valve (12) closes at 140° CA after TDC.
• 4 shows the conditions at idle. The control times of the 2nd inlet valve (12) and the 2nd outlet valve (14) have shifted by 100° CA in the direction of rotation, the inlet valves (11) and (12) now work synchronously and open 90° CA after TDC and the 2nd Exhaust valve (14) closes 110° CA after TDC. The control diagram shows that exhaust gas is sucked in first and then air, with the upward movement of the piston to BDC pushing some of the air out of the cylinder again. There is no reduction in compression, since the two inlet valves are closed at the same crank angle after BDC, both at full load and at idle. The examined 2-stroke gasoline engine has valves for the intake of fresh gas and exhaust gas at the upper end of the cylinder and slots for the exhaust at the lower end of the cylinder. The concurrent scavenging in the cylinder axis that this causes, the combustion gas expanding in the same direction, and the large flow cross sections at the inlet and outlet result in very low flow losses. The maximum speed is about half that of a standard 4-stroke petrol engine, Power-to-weight ratio and heat load are consequently very similar to this. Targeted operation at lower speeds leads to more favorable specific fuel consumption and significantly increases the time available for gas exchange. At intake, first exhaust gas and then fresh gas are pushed into the cylinder in a ratio to each other that corresponds to the power requirements of the engine. The introduction of exhaust gases makes throttling of the fresh gas unnecessary. The gas exchange takes place by means of the kinetic energy of the outflowing exhaust gases and possibly an additional fan.
• 5 shows the control diagram at full load. The fresh gas ignited just before TDC burns and pushes the piston down until the exhaust ports (17) are released after a defined distance. If the pre-release (18) is sufficient, the pressure in the cylinder drops quickly and the fresh gas is sucked into the cylinder by the kinetic energy of the outflowing exhaust gas after the inlet valves (15) open. After exceeding BDC, the piston moves upwards again and closes the outlet slots (17). The inlet valves for the fresh gas (15) are closed with a time delay in order to allow the fresh gas to flow into the cylinder and thus improve filling.
• 6 shows the control diagram at idle. Here, after the downward movement of the piston, the release of the outlet slots (17) and after the pre-outlet (18), the inlet valves for the exhaust gas (16) are first opened. After a defined amount of exhaust gas has flowed into the cylinder, the associated intake valves (16) close, after the intake valves for the fresh gas (15) were opened shortly before. The amount of fresh gas sucked in is determined by the idling operation and the sucked-in exhaust gases prevent the throttling of the fresh gases. The working cycle of a 4-stroke gasoline engine with exhaust gas intake (AGA) is used to show how it works when idling. The designated parts are: intake valve (21), exhaust valve (22), spark plug (23), piston (24), cylinder (25), connecting rod (26) and crankshaft (27). The arrow indicates the direction of rotation of the crankshaft (1), (2) is top dead center (TDC) and (3) bottom dead center (UT).
• The 7 until 12 show how the four bars work:
• 7 : The intake (1st stroke) has started, the piston (24) is 60° CA after TDC, the inlet valve (21) has just opened, the outlet valve (22) is closed and the cylinder (25) is filled with old exhaust gas (29) filled from the previous working cycle.
• 8th : Intake is complete, the piston is 20° CA after BDC, the exhaust valve (22) is closed, the intake valve (21) is open and fresh gas (28) has flowed into the upper area of the cylinder. At the bottom of the cylinder is a layer of old exhaust (29).
• 9 : The piston is 90° CA after BDC and has just pushed some of the fresh gas (28) back into the intake manifold. The inlet valve closes at approx. 100° CA after BDC and compression (2nd stroke) begins.
• 10 : The piston is 20° CA before TDC and the fresh gas (28) is just being ignited. The exhaust gas layer (29) above the piston head is inert and does not participate in the combustion.
• 11 : The fresh gas burns and does work (3rd stroke). There are two plumes of exhaust gas in the cylinder, an old one (29) above the piston crown from previous work cycles and a fresh one (30) on top that is in the process of burning off.
• 12 : The piston is at 50° CA after BDC, moves up and pushes the exhaust gases out. First the fresh exhaust gas (30) is pushed out and then the old exhaust gas (29), which is sucked back into the cylinder in the first stroke of the following working cycle. This exhaust gas can be cooled via a bypass on the outlet pipe.

The number of valves and the type of control, e.g. via a camshaft, electromechanically or electrohydraulically, must be determined individually for each type of construction.

Claims (10)

Method for operating an internal combustion engine, characterized in that two separate gases or gas mixtures are pushed into the cylinder during the intake process, one of which consists of an inert gas and the other of fresh gas or a precursor of fresh gas, so that in the cylinder a Stratification of inert gas and a stratification of fresh gas or a precursor of fresh gas is formed. procedure after claim 1 , characterized in that the inert gas consists of a non-combustible gas mixture, preferably exhaust gas. Procedure according to one of Claims 1 until 2 , characterized in that the fresh gas or the precursor of fresh gas is selected from the group of air, mixture of air and fuel or mixture of air, fuel and exhaust gas. Procedure according to one of Claims 1 until 3 , characterized in that the ratio of inert gas and fresh gas or the precursor of fresh gas to each other is determined by the current power requirement and a negative pressure in the cylinder is avoided. Procedure according to one of Claims 1 until 4 , characterized in that the fresh gas consists of a stoichiometric mixture of air and fuel. Procedure according to one of Claims 1 until 5 , characterized in that the precursor of fresh gas in the cylinder is air into which fuel is injected, the intake air and the injected fuel preferably forming a stoichiometric mixture. Internal combustion engine equipped with at least one cylinder, valves, pistons and a crankshaft, characterized in that during the intake process, by adjusting the valves, first inert gas and then fresh gas or a precursor of fresh gas is pushed into the cylinder, so that a layer of inert gas is created in the cylinder Gas and a stratification of fresh gas or a precursor of fresh gas is formed. combustion engine after claim 7 , characterized in that the valves are adjusted by changing the phases of the camshafts with respect to the crankshaft. combustion engine after claim 7 or 8th , characterized in that it is a two-stroke gasoline engine, a four-stroke gasoline engine or a diesel engine. combustion engine after claim 9 , characterized in that it is a two-stroke gasoline engine in which there are valves for the intake of fresh gas and valves for the intake of exhaust gas at the upper end of the cylinder and in which slots are located at the lower end of the cylinder through which exhaust gas is expelled .

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