DE102022126276B3 - Method for operating an internal combustion engine of a motor vehicle - Google Patents

Abstract

The invention relates to a method for operating an internal combustion engine (1) of a motor vehicle, in which the internal combustion engine (1) is operated in a high-load range of the internal combustion engine (1) extending from at least 80% to 100% of the full load of the internal combustion engine (1), wherein Within a respective working cycle of the internal combustion engine (1) taking place in high-load operation, at least two injections (E1, E2) are carried out one after the other, namely a main injection (E1), by means of which a first amount of fuel is injected into a combustion chamber (4) of the internal combustion engine (1 ) is introduced, and a post-injection (E2) following the main injection (E1), by means of which a second amount of fuel is introduced into the combustion chamber (4). The post-injection (E2) begins at most 20 degrees crank angle after the main injection (E1).

Description

The invention relates to a method for operating an internal combustion engine of a motor vehicle according to the preamble of patent claim 1.

The JP 2005 - 155 601 A a method for operating an internal combustion engine can be seen as known, in which injections are carried out. Furthermore, the reveals US 9,599,058 B2 a control device for a gasoline engine with direct injection. From the DE 10 2016 105 883 B4 a vehicle engine control device is known. In addition, the reveals JP 5370243 B2 a method for operating an internal combustion engine. Furthermore, from the DE 10 2014 019 359 A1 a diesel engine is known. The DE 10 2012 022 156 A1 discloses a method for fuel injection into a diesel engine. From the DE 10 2020 100 535 A1 a method for controlling combustion of a direct injection diesel engine is known. Furthermore, the reveals DE 10 2018 003 999 A1 a diesel engine. Furthermore, from the DE 102 49 755 A1 Method for exhaust gas aftertreatment by post-injection of fuel in an internal combustion engine is known.

The object of the present invention is to create a method for operating an internal combustion engine so that particularly low-emission operation of the internal combustion engine can be achieved.

This object is achieved according to the invention by a method with the features of patent claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

The invention relates to a method for operating an internal combustion engine designed as a reciprocating piston engine or reciprocating piston engine and also referred to as an internal combustion engine or internal combustion engine of a motor vehicle, also simply referred to as a vehicle, which is preferably designed as a motor vehicle, in particular as a passenger car. The motor vehicle can be driven by the internal combustion engine. In particular, in the method the motor vehicle is driven by means of the internal combustion engine. In the method, the internal combustion engine is operated, based on its full load, in a high-load range of the internal combustion engine that extends from at least 80% to 100% of the full load of the internal combustion engine. In other words, in the method the internal combustion engine is operated in what is also known as an operating range, the operating range being the high-load range mentioned. Operating the internal combustion engine in the high-load range, i.e. in the operating range, means that the internal combustion engine is operated in an operating or load point in which the internal combustion engine is operated at at least 80% of its full load. Thus, in the method according to the invention, the high-load range extends, in particular at most, over the top 20% of the entire core field or of the entire load range of the internal combustion engine, which extends from 0% to 100% of full load. Expressed again in other words, if (any) internal combustion engine of a motor vehicle is operated at an operating point in which this internal combustion engine is operated with a load that is at least 80% of the full load of this internal combustion engine, then this internal combustion engine is in the high-load range according to the method according to the invention operated.

In order to be able to realize a particularly low-emission operation of the internal combustion engine, it is provided according to the invention that exactly three injections are carried out one after the other within a respective working cycle of the internal combustion engine that takes place in the high-load operation of the internal combustion engine, namely a main injection, a post-injection following the main injection and one the main injection or the start of the pre-injection. By means of or during the main injection, a first quantity of a particularly liquid fuel is introduced, in particular injected directly, into a combustion chamber of the internal combustion engine. By means of or during the post-injection, a second amount of fuel, in particular different from the first amount, is introduced into the combustion chamber, in particular injected directly. When we talk about injections below, unless otherwise stated, this means the injections that are carried out within the respective work cycle that takes place, that is, takes place in the high-load operation. In particular, it is preferably provided that the injections are carried out using an injector, in particular using the same injector. The injections are individual injections. This means in particular that the injections are spaced apart in time. This means that, for example, if within the respective working cycle, which takes place in the high-load operation, a first of the injections and then a second of the injections are carried out, the first injection ends before the second injection begins, that is to say the second injection begins only after the first injection, that is, only after the first injection has ended. If the respective work cycle is discussed below, this is to be understood as meaning the respective work cycle of the internal combustion engine that takes place in high-load operation, unless otherwise stated.

The internal combustion engine has an output shaft designed as a crankshaft, via which the internal combustion engine can provide drive torque for driving the motor vehicle. In particular, the output shaft is rotatable about a shaft rotation axis relative to a housing element of the internal combustion engine. The housing element is in particular a crankcase, in particular a cylinder crankcase. The combustion chamber mentioned is, for example, partially delimited by a cylinder which is formed by the housing element. Furthermore, for example, the combustion chamber is partially delimited by a piston, which is arranged on the cylinder in a translationally movable manner. The piston is articulated to the output shaft via a connecting rod, so that translational movements of the piston in the cylinder can be converted into a rotational movement of the output shaft. The internal combustion engine is designed, for example, as a four-stroke engine, so that the respective working cycle, in particular precisely, comprises two complete revolutions of the output shaft, therefore, in particular precisely, 720 degrees crank angle (°KW) crank angle.

According to the invention, it is further provided that the post-injection begins at most 20 degrees crank angle, in particular at most 15 degrees crank angle, after the main injection, that is to say after its end. As a result, the post-injection is very close to the main injection, which means that nitrogen oxide (NOx) and soot emissions from the internal combustion engine in particular can be kept to a particularly low level. In addition, excessive entry of soot or soot particles into an oil provided for lubricating the internal combustion engine, in particular the piston, also known as engine oil, can be avoided, which can result in a particularly long service life of the internal combustion engine and / or long maintenance intervals.

A fuel-air mixture, also known as a mixture, is formed from the fuel and air, which is ignited in the combustion chamber within the respective working cycle and subsequently burned as part of a combustion process. This creates an exhaust gas from the internal combustion engine from the mixture. During the combustion process, soot can arise or remain in the combustion chamber, also known as the combustion chamber, with the method according to the invention making it possible to keep the amount of soot resulting from the combustion process particularly low in high-load operation. This means that the introduction of soot into the engine oil can be reduced compared to conventional solutions.

By means of the pre-injection, a third amount of fuel, which is smaller than the first amount, is introduced into the combustion chamber, in particular injected directly. The third quantity may correspond to the second quantity, or the third quantity may be greater or less than the second quantity. In this way, nitrogen oxide and soot emissions in particular and thus also the soot entry can be kept particularly low. Also with regard to the main injection, the post-injection and, in particular, a pre-injection, it is provided that the main injection begins after the pre-injection, that is after its end, so that the pre-injection ends before the main injection begins.

In order to be able to realize a particularly low-emission operation of the internal combustion engine, particularly with regard to the nitrogen oxide and soot emissions, it is provided in one embodiment of the invention that within the respective working cycle of the internal combustion engine that takes place in high-load operation, the post-injection has at least 12 degrees of crank angle, most preferably at least 15 degrees crank angle, after the main injection, i.e. after the end of which begins.

The invention is based on the following findings and considerations: Internal combustion engines are limited by various mechanical component limits such as exhaust gas temperatures, turbocharger speeds, peak cylinder pressures, opacity level in the exhaust gas, soot entry into the engine oil, etc. The soot level in the exhaust gas of the internal combustion engine resulting from the combustion process can contaminate various components such as an intake section, an exhaust gas recirculation system, a valve train and the engine oil and lead to high levels of pollution if no appropriate countermeasures are taken. Therefore, the goal is to keep the soot level, that is, the amount of soot resulting from the combustion process within the respective work cycle, low, which is now possible through the method according to the invention. Nitrogen oxides and soot in the exhaust gas interact with each other. The method according to the invention now makes it possible to reduce soot emissions as well also reduce nitrogen oxide emissions compared to conventional solutions. For this purpose, the method according to the invention is a combustion process through which particularly low-emission operation of the internal combustion engine can be achieved, particularly with regard to soot and nitrogen oxides. In addition, the entry of soot into the engine oil can be advantageously kept to a minimum. The injector, also known as an injection nozzle, can have an influence on the soot entry into the engine oil, particularly with regard to hydraulics for introducing the fuel into the combustion chamber and the soot produced during the combustion process, also known as combustion. In conventional processes or engine developments, the reduction in nitrogen oxide emissions results in higher soot emissions, also known as particulate emissions, especially during high-load engine operation. The emissions behavior of the internal combustion engine usually moves along a so-called soot particle-nitrogen oxide target conflict or compromise. The increased particle emissions in the exhaust gas can lead to the intake system, the exhaust gas recirculation system, injection nozzles, an oil switch-off and the valve train being subjected to severe mechanical stress, as these systems become sooted and/or sooted. The method according to the invention can now avoid these disadvantages, since the soot level or soot emissions can be reduced by the method according to the invention compared to conventional solutions. So that high specific outputs can be achieved in modern internal combustion engines, for example designed as diesel engines, a high degree of charging may be required. Typically, a sufficiently high, specific performance level could only be achieved in combination with high loading pressures. In order to ensure that the mechanically limited cylinder peak pressure is not violated by the high degrees of supercharging, it is necessary in conventional methods to place the injections, also known as injection events, and therefore the main injections in post-injection, a little later with optimal efficiency and/or to space them apart from one another in such a way that, in particular the post-injection starts very late and far later than 20 degrees crank angle after the main injection. However, this delayed injection event can lead to increased soot emissions and thus to increased soot entry into the engine oil. The soot in the engine oil can cause wear. In contrast, the method according to the invention now makes it possible to advantageously keep the nitrogen oxide and soot emissions and thus also the soot entry into the engine oil low, especially in high-load operation, which is also referred to as high-load operation. At the same time, because the post-injection is very close to the main injection, a very high specific output of the internal combustion engine can be achieved. Because the post-injection, which represents an additional injection event with respect to the main injection, is located very close to the main injection, i.e. begins at most 20 degrees crank angle after the main injection, in particular after its end, the main injection can, in particular completely and therefore 100% , remain torque effective, which means that particularly low-emission operation and a particularly high specific output of the internal combustion engine can be achieved. The post-injection, which is carried out after the main injection, can avoid excessive soot formation in the combustion chamber, since the post-injection creates a further pulse in the combustion chamber, especially compared to the main injection. This results in an advantageously high level of turbulence, which means that the air in the combustion chamber can be used much better, especially for burning the fuel. In addition to the reduced soot production, existing soot levels can also be better oxidized. Overall, a significantly lower level of soot can be found in the exhaust gas compared to conventional solutions. The ingress of soot into the engine oil can also be significantly reduced by the method according to the invention compared to conventional solutions. This was confirmed by emissions measurements on an engine test bench and in a motor vehicle equipped with the internal combustion engine.

It has proven to be particularly advantageous if an additional injection, through which the fuel is introduced into the combustion chamber, is not carried out within the respective working cycle of the internal combustion engine between the main injection and the post-injection that takes place in high-load operation. In other words, it is preferably provided that the main injection and the post-injection are immediately adjacent. This means that no other further injection of fuel takes place within the respective working cycle between the main injection and the post-injection. This allows particularly low-emission operation to be achieved.

In order to be able to keep the nitrogen oxide and soot emissions as well as the soot entry particularly low, it is provided in a further embodiment of the invention that the second amount is less than the first amount.

In order to achieve particularly low-emission operation, it has proven to be particularly advantageous if the second amount is in a range of 1% to 5% of the first amount.

Finally, in order to achieve particularly low-emission operation, it has proven to be particularly advantageous if a diesel engine is used as the internal combustion engine. In other words, it is preferably provided that the internal combustion engine is a diesel engine. The fuel is therefore preferably a diesel fuel.

A second aspect of the invention relates to an internal combustion engine which is designed to carry out a method according to the invention according to the first aspect of the invention. Advantages and advantageous embodiments of the first aspect of the invention are to be viewed as advantages and advantageous embodiments of the second aspect of the invention and vice versa.

• 1 eine schematische Darstellung einer Verbrennungskraftmaschine eines Kraftfahrzeugs;
• 2 ein Diagramm zum Veranschaulichen einer ersten Ausführungsform eines Verfahrens zum Betreiben der Verbrennungskraftmaschine;
• 3 ein Diagramm zum Veranschaulichen einer zweiten Ausführungsform des Verfahrens; und
• 4 ein Diagramm zum Veranschaulichen einer dritten Ausführungsform des Verfahrens.

Further details of the invention result from the following description of preferred exemplary embodiments with the associated drawings. This shows:

• 1 a schematic representation of an internal combustion engine of a motor vehicle;
• 2 a diagram for illustrating a first embodiment of a method for operating the internal combustion engine;
• 3 a diagram illustrating a second embodiment of the method; and
• 4 a diagram to illustrate a third embodiment of the method.

In the figures, identical or functionally identical elements are provided with identical reference symbols. 1 shows a schematic representation of an internal combustion engine 1 for a motor vehicle, also referred to as an internal combustion engine or combustion machine and designed, for example, as a diesel engine. 1 to 4 a method for operating the internal combustion engine 1 is described, which, for example, drives the motor vehicle in the method. In the method, the internal combustion engine 1 is operated in its fired mode and the internal combustion engine 1 has a housing element 2, designed, for example, as a crankcase, in particular as a cylinder crankcase, through which cylinders 3 are formed. The respective cylinder 3 partially delimits a respective combustion chamber 4 of the internal combustion engine 1. When the internal combustion engine 1 is fired, combustion processes take place in the respective combustion chamber 4, which are also referred to as combustion processes. A respective piston is accommodated in the respective cylinder 3 so that it can move in translation. The pistons are articulated via respective connecting rods to an output shaft 5 of the internal combustion engine 1, designed as a crankshaft. The output shaft 5 is thus rotatable on the shaft axis of rotation relative to the housing element 2. The combustion processes drive the pistons and, via the connecting rods, the output shaft 5, whereby the output shaft 5 is rotated about the shaft rotation axis relative to the housing element 2.

In the method, the internal combustion engine 1 is operated, based on its full load, in a high-load range of the internal combustion engine 1 that extends from at least 80% to 100% of the full load of the internal combustion engine. This means that the full load range begins at least at 80% of the full load of the internal combustion engine 1 and ends at 100% of the full load of the internal combustion engine 1. Thus, every operating point in which the internal combustion engine 1 is operated with a load that is at least 80% of the full load is in the high-load range. Conversely, for example, every operating point in which the internal combustion engine 1 is operated with a load that is less than 80% of the full load of the internal combustion engine 1 is outside the high-load range.

Based on 2 A first embodiment of the method is described below. In the first embodiment, within a respective working cycle of the internal combustion engine taking place in high-load operation, exactly two injections E1 and E2 are carried out using the same injector. The respective injection E1, E2 is a fuel injection designed as a single injection, in which or by means of which a fuel, in particular a liquid fuel, designed as diesel fuel, is injected directly into the respective combustion chamber 4 by means of the injector and thereby introduced. Thus, for example, on the abscissa designated 6 of the 2 degrees crank angle (°CA) are plotted on the ordinate 7 of the diagram shown in 2 For example, in the diagram shown, a value is plotted which is explained in more detail below. It can be seen that the injections in E1 and E2 are carried out one after the other within the respective working cycle, such that the injection E2 following the injection E1 only begins after the injection E1 has ended. A start of the injection E1 is designated with B1, and a start of the injection E2 is designated with B2. An end of the injection E1 is designated with EN1 and an end of the injection E2 is designated with EN2. It can be seen that within the respective working cycle, which takes place in high-load operation, the injection E1 begins at its start B1 and ends at its end EN1. Accordingly, within the respective working cycle, which takes place in the high-load operation takes place, the injection E2 at its beginning B2, and within the respective working cycle, which takes place in the high-load operation, the injection E2 ends at its end EN2. It can be seen that the end EN1 and the beginning B2 are different, and are therefore spaced apart in time.

The injection E1 is a main injection, by means of which, in particular precisely, a first amount of fuel is injected directly into the combustion chamber 4 and thereby introduced. The injection E2 following the main injection is a post-injection, by means of which, in particular, a second amount of fuel that is smaller than the first amount is directly injected into the combustion chamber 4 and thereby introduced.

In order to be able to realize a particularly low-emission operation of the internal combustion engine 1, particularly with regard to soot and nitrogen oxide emissions, the method provides that the post-injection (injection E2) begins at a maximum of 20 degrees crank angle after the main injection (injection E1). In other words, it is intended that the start B2 is at most 20 degrees crank angle after the end EN1. Besides, it's over 2 recognizable that within the respective, in 2 illustrated and taking place in the high-load operation cycle of the internal combustion engine 1 between the injections E1 and E2, an additional injection through which the fuel is introduced into the combustion chamber 4 is not carried out, so that the injections E1 and E2 are immediately adjacent within the respective cycle. Furthermore, it is preferably provided that the post-injection begins at least 15 degrees crank angle after the main injection within the respective working cycle.

The quantity plotted on the ordinate 7 is or characterizes or describes the respective amount of fuel. So it's over 2 It can be seen that the first amount is larger than the second amount, in particular such that the second amount is in a range of 1% to 5% of the first amount.

In 3 a second embodiment of the method is illustrated. In the second embodiment, if exactly three injections E1, E2 and E3 are carried out within the respective working cycle of the internal combustion engine 1 taking place in high-load operation, by means of which the fuel is injected directly into the combustion chamber 4 and thus introduced. In the second embodiment, the injection E1 is the one already referred to 2 main injection described, and in the second embodiment the injection E2 is the one already referred to 2 post-injection described. The injection E3 is a pre-injection preceding the main injection or its start B1, by means of which, in particular precisely, a third amount of fuel that is smaller than the first amount is directly injected into the combustion chamber 4 and thus introduced. It can be seen that the pilot injection (injection E3) begins at a third start B3 and ends at a third end EN3, with the injection E3 ending before the injection E1 begins. The start B1 and the end EN3 are therefore spaced apart in time.

Finally, 4 a third embodiment of the method. In the fourth embodiment, within the respective working cycle of the internal combustion engine 1 taking place in high-load operation, exactly four injections E1, E2, E3 and E4 are carried out one after the other, namely the injection E1 designed as the main injection, the injection E2 designed as the post-injection and a first pre-injection in the form of the injection E3 and a second pre-injection in the form of the injection E4. It can be seen that the first pre-injection (injection) E3 precedes the main injection and the second pre-injection (injection E4) precedes the first pre-injection. As in the second embodiment, the first pre-injection (injection E3) begins at a third start B3 and the injection E3 ends at a third end EN3. The end EN3 and the start B1 are spaced apart from one another in time. The second pre-injection (injection E4) begins at a fourth start B4 and ends at a fourth end EN4. It can be seen that the fourth end EN4 and the third start B3 are spaced apart in time, so that injection E4 ends before injection E3 begins. By means of the first pre-injection, a third amount of fuel, which is smaller than the first amount, is injected directly into the combustion chamber 4 and thus introduced, in order to ensure that the fuel is supplied to the combustion chamber 4 at the same time. At or by means of the second pre-injection, a fourth amount of fuel, which is smaller than the first amount, is injected directly into the combustion chamber 4 and thus introduced. This makes it possible to keep nitrogen and soot emissions particularly low. In addition, excessive soot entry into the engine oil can be avoided.

Reference symbol list

1

Internal combustion engine

2

Housing element

3

cylinder

4

combustion chamber

5

output shaft

6

abscissa

7

ordinate

B1

beginning

B2

beginning

B3

Start

B4

beginning

E1

injection

E2

injection

E3

injection

E4

injection

EN1

End

EN2

End

EN3

End

EN4

End

Claims (6)

Method for operating an internal combustion engine (1) of a motor vehicle, in which the internal combustion engine (1) is operated in a high-load range of the internal combustion engine (1) extending from at least 80% to 100% of the full load of the internal combustion engine (1), characterized in that within of a respective working cycle of the internal combustion engine (1) taking place in high-load operation: - exactly three injections (E1, E2, E3) are carried out one after the other, namely: ◯ a main injection (E1), by means of which a first amount of fuel is injected into a combustion chamber (4 ) is introduced into the internal combustion engine (1); ◯ a post-injection (E2) following the main injection (E1), by means of which a second amount of fuel is introduced into the combustion chamber (4); and ◯ a pre-injection (E3) preceding the main injection (E2), by means of which a third amount of fuel, which is smaller than the first amount, is introduced into the combustion chamber (4); and - the post-injection (E2) begins at most 20 degrees crank angle after the main injection (E1). Procedure according to Claim 1 , characterized in that within the respective working cycle of the internal combustion engine (1) taking place in high-load operation, the post-injection (E2) begins at least 15 degrees crank angle after the main injection (E2). Procedure according to Claim 1 or 2 , characterized in that within the respective working cycle of the internal combustion engine (1) taking place in high-load operation between the main injection (E1) and the post-injection (E2), an additional injection is carried out, through which the fuel is introduced into the combustion chamber (4), omitted. Method according to one of the preceding claims, characterized in that the second amount is less than the first amount. Procedure according to Claim 4 , characterized in that the second amount is in a range of 1% to 5% of the first amount. Method according to one of the preceding claims, characterized in that a diesel engine is used as the internal combustion engine (1).

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