DE102020211925A1 - Internal combustion engine with exhaust gas recirculation and actuator for influencing the filling, and control of such an internal combustion engine - Google Patents

Abstract

Control for an internal combustion engine (110) with exhaust gas recirculation (109) and at least one actuator (113) for influencing the filling of the internal combustion engine (110), the control being designed to load or filling-dependent desired values (EGR2) for the at least one actuator ( 113) and the EGR rate (AGR2) of the exhaust gas recirculation (109) in such a way that the target values (AGR2) for the EGR rate are reduced quickly or abruptly with increasing load (L) or filling.

Description

The invention relates to an internal combustion engine with exhaust gas recirculation.

In an internal combustion engine, the fresh air filling is decisive for the torque delivered. Stable combustion and the functionality of the exhaust aftertreatment can only be guaranteed within a narrow fuel-air ratio. Therefore, measures to increase the charge, such as an exhaust gas turbocharger (ATL) or compressors, are often used.

A measure to increase efficiency or to improve emission behavior is the use of exhaust gas recirculation (EGR). Exhaust gas is added to the fresh air in order to achieve a better combustion process. The exhaust gas recirculation replaces part of the fresh air and thus has a filling-reducing effect.

A further measure to increase the efficiency of combustion engines is a fuel-reduced combustion process. In practice, this is done by changing the control times, for example by closing the intake valve well before or after bottom dead center during the gas exchange. The effective compression is reduced during compression and undesirable combustion phenomena (e.g. knocking) are avoided. High compression can still be used during expansion. The disadvantage is that the filling and thus the torque is reduced by a deviation from dead center. Since exhaust gas is not replaced by air (or air-fuel mixture) in the cylinder during the gas exchange between combustions, this measure of changing the valve timing is also referred to as internal exhaust gas recirculation. In addition to the control time of the intake valve, the control time of the exhaust valve or the combination of the times from "exhaust valve closes" and "intake valve opens" as well as their common position relative to bottom dead center also influences the internal exhaust gas recirculation.

Both measures - external exhaust gas recirculation and influencing the control times - are limited in total by the charge that can still be displayed. As soon as the filling is no longer sufficient for the target torque (e.g. in the event of a sudden change in load), the measures must be restricted or the more efficient of the two measures must be switched to as quickly as possible. However, this is countered by the fact that the fresh air side has a sluggish control behavior.

The object of the present invention is to achieve an increase in the efficiency or an improvement in the emission behavior of an internal combustion engine.

This object is achieved by the control according to claim 1 according to the invention or the method according to claim 11 . Further advantageous refinements of the invention result from the dependent claims and the following description of preferred exemplary embodiments of the present invention.

The exemplary embodiments show a controller for an internal combustion engine with exhaust gas recirculation and at least one actuator for influencing the filling of the internal combustion engine, the controller being designed to specify load- or filling-dependent setpoint values for the at least one actuator and load- or filling-dependent setpoint values for the EGR rate to specify the exhaust gas recirculation in such a way that the target values for the EGR rate of the exhaust gas recirculation are reduced quickly or abruptly with increasing load or filling.

The internal combustion engine can in particular be an internal combustion engine with a charge-reduced combustion process, with external exhaust gas recirculation and at least one actuator for influencing the charge of the internal combustion engine, e.g. an intake camshaft phaser, which can change the control times of the intake valves. The internal combustion engine is preferably an Otto engine or else a diesel engine.

The exhaust gas recirculation can be, for example, high-pressure exhaust gas recirculation, low-pressure exhaust gas recirculation, or a combination of high-pressure exhaust gas recirculation and low-pressure exhaust gas recirculation. The control unit can variably set the EGR rate, i.e. the proportion of the recirculated exhaust gas in the total filling, for example with an EGR valve.

The controller can be an engine control unit, for example. A control according to the invention can be used in any internal combustion engine that is equipped with exhaust gas recirculation, in particular in an internal combustion engine with external exhaust gas recirculation, in which the exhaust gas is taken from the exhaust tract and fed to the intake tract via a line, a cooler and a valve. and at least one actuator for influencing the filling of the internal combustion engine, for example an intake camshaft phaser, which can change the control times of the intake valves.

The target values for the at least one actuator can be target values for any components which, in addition to an external exhaust gas recirculation have an influence on the filling of the internal combustion engine, for example control times for an intake valve (eg by means of a camshaft phaser). However, the target values for the at least one actuator can also be control times of an exhaust valve or control times for an intake valve and an exhaust valve. It can also involve other settings that have an impact on internal exhaust gas recirculation.

The target values for the EGR rate and actuator position can, for example, be specified as a function of the load. However, the invention is not limited to a load-dependent representation, but can also be implemented in an equivalent manner by referring to the cylinder filling, or by referring to any variable that expresses the load, for example any variable that is proportional to the torque (e.g driver request, pedal angle, etc.). In the context of these exemplary embodiments, the term load-dependent is to be understood as meaning any variable which expresses the load and is, for example, proportional to the torque or equivalent engine operating points.

According to one exemplary embodiment, the controller is set up to reduce the EGR rate quickly or abruptly from a predetermined load or corresponding charge, so that a range without exhaust gas recirculation arises. This range in which no exhaust gas recirculation is operated can begin, for example, 1 bar, preferably 2 bar and even more preferably 3 bar before the maximum load, with the load-dependent engine operating point being described here by reference to the effective mean pressure, but alternatively by corresponding reference to Torque or engine filling can be expressed.

The specified load, from which the target EGR rate is reduced quickly or abruptly, is selected, for example, in such a way that a shift to a higher load or corresponding filling no longer generates any further advantage in consumption.

The gradient of the jump in the EGR rate can be, for example, 7% per bar, preferably 10% per bar, and even more preferably 12% per bar mean effective pressure.

According to one exemplary embodiment, the controller is set up to place the actuator in a reduced-fill position in opposition to the reduction in the EGR rate. This can happen, for example, just as quickly or abruptly as changing the EGR rate.

The controller is set up, for example, to set a target position of the actuator to a position that is optimal for filling. This filling-optimal position of the actuator has the advantage that it results in a larger mass in the cylinder.

According to one exemplary embodiment, the controller is set up to hold the actuator in the fill-optimized position from the rapid or abrupt reduction in the EGR rate until a maximum load is reached. This can be achieved, for example, by constantly maintaining the optimal filling. In a phase without exhaust gas recirculation, the actuator is thus held in a position with a greater charge. This also allows the advantages to be retained, but the sudden change only occurs in the EGR rate.

According to one exemplary embodiment, the controller is set up to keep the EGR rate (AGR2) as high as possible before the rapid or abrupt reduction in the EGR rate. This has the advantage that the EGR rate is as high as possible, particularly in the optimal filling position. For example, the controller may be configured to maintain the EGR rate at least 7%, more preferably at least 10%, and even more preferably at least 12% prior to rapidly or ramping down. A limitation results from several factors, which occur simultaneously with an optimal design, for example the limits of the fresh air supply (e.g. consumption disadvantage due to increasing back pressure in front of the turbine of the exhaust gas turbocharger greater than gain due to EGR), instability of the combustion (strong cyclical scattering of the combustion or misfires). ) due to an excessively high EGR rate and exceeding thermal component limits (heat input increases with higher EGR mass flow).

Also according to the invention is an internal combustion engine which is equipped with the control system described here and a vehicle which is equipped with the engine control system described here or an internal combustion engine according to the invention.

The exemplary embodiments also show a method for operating an internal combustion engine with exhaust gas recirculation and at least one actuator for influencing the filling of the internal combustion engine, the method including specifying load-dependent or filling-dependent setpoint values for the at least one actuator and the EGR rate of the exhaust gas recirculation such that that with increasing load or filling, the target values for the EGR rate are reduced quickly or abruptly.

• 1 schematisch ein Ausführungsbeispiel für eine Anordnung eines Verbrennungsmotors mit Niederdruck-Abgasrückführung, Hochdruck-Abgasrückführung und Abgasturbolader zeigt;
• 2 schematisch ein Ausführungsbeispiel für eine Anordnung eines Verbrennungsmotors mit Niederdruck-Abgasrückführung und Abgasturbolader zeigt;
• 3 schematisch ein Ausführungsbeispiel für eine Anordnung eines Verbrennungsmotors mit Hochdruck-Abgasrückführung und Abgasturbolader zeigt;
• 4 schematisch ein Ausführungsbeispiel für eine Anordnung eines Verbrennungsmotors mit Hochdruck-Abgasrückführung ohne Aufladung zeigt;
• 5 schematisch ein Ausführungsbeispiel einer Motorsteuerung zur Steuerung, Regelung und Überwachung von Funktionen der erfindungsgemäßen Anordnung zeigt;
• 6 beispielhaft für eine bestimmte, konstante Drehzahl die Soll-Werte der AGR-Rate und der Position des Aktors über einer ansteigenden Last bis hin zur maximalen Last (statischer Lastschnitt) darstellt;
• 7 beispielhaft einen dynamischen Lastsprung gemäß dem herkömmlichen Verfahren und dem erfindungsgemäßen Verfahren zeigt; und
• 8 einen realitätsnäheren Verlauf der Aktors, gegenüber der konstanten Betrachtung aus 6 zeigt.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

• 1 schematically shows an embodiment of an arrangement of an internal combustion engine with low-pressure exhaust gas recirculation, high-pressure exhaust gas recirculation and exhaust gas turbocharger;
• 2 schematically shows an embodiment of an arrangement of an internal combustion engine with low-pressure exhaust gas recirculation and exhaust gas turbocharger;
• 3 schematically shows an embodiment of an arrangement of an internal combustion engine with high-pressure exhaust gas recirculation and exhaust gas turbocharger;
• 4 schematically shows an embodiment of an arrangement of an internal combustion engine with high-pressure exhaust gas recirculation without supercharging;
• 5 schematically shows an embodiment of an engine control for controlling, regulating and monitoring functions of the arrangement according to the invention;
• 6 shows the setpoint values of the EGR rate and the position of the actuator over an increasing load up to the maximum load (static load section) for a specific, constant speed as an example;
• 7 shows an example of a dynamic load jump according to the conventional method and the method according to the invention; and
• 8th a more realistic course of the actuator compared to the constant view 6 displays.

In the following exemplary embodiments, a method is presented with which there is a quick and efficient change from exhaust gas recirculation to a reduced-charge combustion method as soon as a performance limit for the fresh air supply is reached.

1 shows schematically an embodiment of an arrangement of an internal combustion engine with low-pressure exhaust gas recirculation, high-pressure exhaust gas recirculation and exhaust gas turbocharger. The arrangement 100 includes an air filter 101, an exhaust gas turbocharger (ATL) 102, a low-pressure EGR valve 103, an ATL intercooler 104, an EGR filter 105, an outlet 107, a catalyst with particle filter 108 for exhaust gas aftertreatment, a high-pressure EGR valve 109, an internal combustion engine 110 with camshaft phaser 113, an engine intercooler 111 and an air control valve (throttle valve) 112. The exhaust gas turbocharger (ATL) 102 includes a compressor 102-1, an exhaust gas turbine 102-2 and a variable compressor geometry ( VTG). The exhaust gas turbine 102-2 uses the residual energy of the exhaust gases to drive the compressor 102-1. The compressor 102 - 1 driven by the exhaust gas turbine 102 - 2 draws in fresh air (cold air), which is filtered by the air cleaner 101 . Therefore, the turbocharger 102 increases the air flow rate and decreases the induction work of a piston. The air compressed by exhaust gas turbocharger 102 is routed to air control flap 112 . The air control flap 112 regulates the amount of air that is forwarded to the internal combustion engine 110 . The air allowed from the air control door 112 to the engine 110 is cooled by the engine charge air cooler 111 and then directed to the engine 110 . The internal combustion engine 110 converts energy from the fuel into mechanical action. For this purpose, in a combustion chamber (in 1 not shown) burned a combustible mixture of fuel and air. The thermal expansion of the hot gases generated is used to move the piston. A camshaft opens and closes the intake and exhaust valves of the internal combustion engine according to design control times and according to the specifications of a camshaft phaser 113. The adjustment of the valve opening times by means of the camshaft phaser 113 allows an increase in engine efficiency, depending on the respective load behavior.

The exhaust gases generated in the combustion process of the internal combustion engine 110 are partially recirculated to the high-pressure EGR valve 109 and partially directed to the exhaust gas turbocharger 102 . The recirculation of low-oxygen exhaust gas containing carbon dioxide suppresses fresh air in the intake manifold and reduces the oxygen content of the fresh gas and thus the burning rate. Since the carbon dioxide present absorbs part of the heat of combustion, the combustion temperature decreases as the heat capacity of the exhaust gas via the fresh air increases. A lowering of the combustion temperature reduces the formation of nitrogen oxides and reduces the tendency of the combustible mixture to undesirably, uncontrolled self-ignition. As mentioned above, the residual energy of the exhaust gases is used to drive the compressor 102 - 1 and is passed on to the catalytic converter 108 . Depending on the exhaust gas composition and thus the fuel-air ratio, the catalytic converter 108 removes carbon monoxide and hydrocarbons from the exhaust gas of the internal combustion engine by oxidation with the residual oxygen or with the nitrogen oxides and nitrogen oxides by reduction with carbon monoxide and hydrocarbons. The exhaust gas after the catalytic converter 108 is partially routed to the EGR filter 105 and partially to the outlet 107 . The exhaust gas filtered by the EGR filter 105 is passed through the EGR cooler 104 and routed to compressor 102-1 of exhaust gas turbocharger 102 and compressed with new fresh air and reused to refill internal combustion engine 110 with air.

2 shows schematically an embodiment of an arrangement of an internal combustion engine with low-pressure exhaust gas recirculation and exhaust gas turbocharger. The arrangement includes an air filter 101, an exhaust gas turbocharger 102 with a compressor 102-1 and an exhaust gas turbine 102-2, a low-pressure EGR valve 103 in a low-pressure exhaust gas recirculation system, an exhaust gas aftertreatment system 108, an internal combustion engine 110 with a camshaft phaser 113 and an air control flap ( Throttle valve) 112. In contrast to the embodiment of 1 the arrangement has no high-pressure exhaust gas recirculation.

3 shows schematically an embodiment of an arrangement of an internal combustion engine with high-pressure exhaust gas recirculation and exhaust gas turbocharger. The arrangement includes an air filter 101, an exhaust gas turbocharger 102 with a compressor 102-1 and an exhaust gas turbine 102-2, a high-pressure EGR valve 109 in a high-pressure exhaust gas recirculation system, an exhaust gas aftertreatment system 108, an internal combustion engine 110 with a camshaft phaser 113 and an air control flap ( Throttle valve) 112. In contrast to the embodiment of 1 the arrangement has no low-pressure exhaust gas recirculation.

4 shows schematically an embodiment of an arrangement of an internal combustion engine with high-pressure exhaust gas recirculation without supercharging. The arrangement includes an air filter 101, an exhaust gas treatment 108, an internal combustion engine 110 with a camshaft phaser 113 and an air control valve (throttle valve) 112. In contrast to the embodiment of FIG 1 the arrangement has no exhaust gas turbocharger and no low-pressure exhaust gas recirculation.

5 shows schematically an embodiment of an engine control for controlling, regulating and monitoring functions of the arrangement according to the invention. Engine control 201 controls, for example, an internal combustion engine 110, in particular its camshaft phaser 113, an exhaust gas turbocharger 102 (e.g. the variable compressor geometry), a low-pressure EGR valve 103, a high-pressure EGR valve 109 and an air control flap 112 in order to operate the Internal combustion engine, for example, to regulate the air path. After starting the cold engine, the engine management system requests a high high-pressure EGR rate. For example, the engine control activates the variable compressor geometry of the exhaust gas turbocharger 102 in order to provide the required pressure drop for the high-pressure EGR and the charge pressure required to achieve the required cylinder charge.

By controlling the camshaft phaser 113, the engine controller 201 changes the control times of the intake valves and thus influences the filling of the internal combustion engine. By controlling the variable compressor geometry of the exhaust gas turbocharger 102, the low-pressure EGR valve 103, the high-pressure EGR valve 109 and the air control flap 112, the engine controller 201 controls the external EGR, in particular the EGR rate. Both measures - controlling the EGR rate and influencing the filling - aim to optimize the combustion process in terms of efficiency and emissions. Both influence the gas exchange and thus the filling in terms of quantity, composition, pressure, temperature and caloric properties. Interactions between the two measures therefore inevitably occur. This applies in particular to modern combustion processes. Atkinson or Miller combustion processes, which end the intake process well after or before bottom dead center, give up part of the fresh air filling and thus part of the maximum torque in favor of better efficiency. HCCI combustion processes that perform (partial) combustion through self-ignition of the fuel-air mixture are dependent on a defined heat input from internally or externally recirculated exhaust gas for self-ignition. The amount of recirculated exhaust gas is in turn determined by the external EGR and the control times (internal EGR).

If both measures - controlling the EGR rate and influencing the control times - are used to their full extent, the maximum charge that can be displayed is limited. In supercharged engines, the performance of the supercharging system is limited, i.e. it is not possible to increase the boost pressure. In non-supercharged engines, all throttles are fully open, i.e. almost ambient pressure is present in the cylinder. As soon as the fresh air charge is no longer sufficient to provide the required torque, at least one of the measures to increase efficiency must be abandoned in favor of a higher charge. An unacceptable deterioration in combustion behavior can also mean that the measures can no longer be used to their full extent. For example, the necessary boost pressure could only be achieved with major efficiency disadvantages in charging, which overcompensated for the increase in efficiency. A selection between the two measures is therefore usually made, such as a continuous crossfade.

The method described in the following exemplary embodiments enables a quick and efficient change from one measure to the other measure. The method achieves this through an advantageous selection of the target values for the actuator and the EGR rate. 6 represents this as an example.

In 6 a static load section is shown, i.e. for a specific, constant speed, the target values EGR1, EGR2 of the EGR rate and the position POS1, POS2 of the actuator are plotted against an increasing load L up to the maximum load Lmax, as you can see, for example, in stored in a characteristic curve of the motor control. The representation applies analogously to any other speeds, with the specific values and curves differing quantitatively but being qualitatively similar. The optimum position of the actuator for the case without EGR is shown as POSO, with a constant value over the load L being assumed here for the sake of simplicity. Without EGR, the actuator is in the charge-reducing position POSred. In this charge-reducing position POSred, the camshaft is in an advanced position. the intake valve then closes well before bottom dead center. For example, this could be at 130° CA (relative to 1 mm valve lift), with the gas exchange BDC corresponding to 180° CA.

Static load cutting, here means that as the load is slowly varied, the actual rate/actual position are adjusted according to the target values. Conventionally, steady progressions of the setpoints over the load L with low gradients are selected because the actuators then reach the setpoint position more quickly and can be controlled well, and there is no jumping between setpoints if the load L changes only slightly. The curves of the actuator or the EGR rate according to this conventional method are shown here as solid lines POS1 and AGR1. With no load, the EGR rate AGR1 is at a low value (or zero) according to these conventional methods. Without load L, the actuator POS1 is initially in the filling-reducing position POSred. With increasing load L, the EGR rate AGR1 is increased up to a maximum possible rate AGRmax (gasoline engines currently achieve a maximum EGR rate of around 25-30%) and takes part of the volume of the fresh air, so it has a filling-reducing effect with regard to the fresh air and has to go through a higher total filling can be compensated. The charge provided is increased, for example, via a throttle valve or an exhaust gas turbocharger and is achieved by increasing the pressure in front of the cylinder. With increasing load L, the total charge cannot be sufficiently increased solely by increasing the pressure in front of the cylinder, so the charge reduction is slightly reduced via the actuator position POS1 in order to maintain the EGR rate AGR1. With a high EGR rate, the fresh air charge required to achieve the maximum load cannot be achieved (or only with a disadvantage in terms of efficiency). With an even further increase in load, the EGR rate AGR1 is steadily reduced again (in this example to zero), while the actuator returns to the charge-reducing position POSred.

According to this exemplary embodiment, an alternative profile POS2 and AGR2 of the setpoint values of the actuator or of the EGR rate is selected compared to the conventional profile POS1, AGR1 of the setpoint values. With this alternative course, the combination of EGR and control times that is most advantageous in terms of efficiency can be selected. The position POS2 of the actuator can be selected in such a way that the maximum value is set at Lmax - regardless of continuity or maximum gradients of actuator position POS2 and AGR rate AGR2. Instead of the previous, continuous curve POS1, the actuator POS2 is moved even further into a filling-optimal position POSopt, and the EGR rate AGR2 is kept as high as possible for as long as it is still advantageous. As a result, a higher fuel consumption advantage can be achieved than with the continuous curve POS1, AGR1. Above a certain load Lh, the EGR rate AGR2 is reduced ("switched off") very quickly or abruptly. At high loads Lh to Lmax, a range without EGR occurs. In this exemplary embodiment, the actuator (cf. POS2) reacts in the opposite direction and is set to the reduced-fill position POSred.

The gradient of the jump in the EGR rate can be, for example, 7% per bar, more preferably 10% per bar, and even more preferably 12% per bar mean effective pressure. For example, the EGR rate may be maintained at at least 7%, more preferably at least 10%, and even more preferably at least 12% prior to being reduced very rapidly or abruptly.

The parameter Lh (or characteristic curve point) can be freely selected with regard to efficiency and can be selected, for example, in such a way that when the load L is shifted to a higher level, no further consumption advantage can be generated. For example, it can describe a limit of the performance of the fresh air supply. Aspects such as the smooth running of the internal combustion engine and the limits of the EGR system can also be taken into account when selecting Lh. The range in which no exhaust gas recirculation is operated can begin, for example, 1 bar, preferably 2 bar and even more preferably 3 bar before the maximum load Lmax. From the point of view of control technology, a continuous course with low gradients would be preferable in order to achieve high control quality and to avoid desired multiple switchovers. According to the invention, use is made of the fact that in certain engine operating ranges (above a certain load, depending on the engine speed), the output power is significantly higher than is required for the propulsion of the vehicle. This means that a request for such high loads is due to a desire to accelerate, ie it is desired to produce the highest possible power output in the shortest possible time. In vehicles in this area, where the focus is not on fine power dosing but on fast, high power output, the accelerator pedal characteristic curve, i.e. the conversion of the accelerator pedal actuation angle by the driver to the resulting load request, is often designed to be correspondingly steep. A small increase in activity therefore leads to a high increase in performance.

In 6 the load L designates a target load, as expressed, for example, by a driver's request or corresponding desired torque, and the dashed vertical lines indicate an initial load L1 and a target load L2 of a load step. Such an example load jump from load L1 to load L2 is in 7 shown.

7 shows a dynamic load jump according to the conventional method and the method according to the invention. The load jump, ie the increase in the setpoint load Ls over time t, from an initial load L1 to a target load L2, is shown in the top area. The two lower areas show how the static load section of the 6 , Target values of the EGR rate AGR1, AGR2 and the position POS1, POS2 of the actuator over time t according to the conventional method (AGR1, POS1) or according to an exemplary inventive method (AGR2, POS2).

Initially (t=0), for the initial load L1, the EGR rates AGR1, AGR2 and the actuator positions POS1, POS2 correspond to their respective values from the static load section 6 . After the load jump, i.e. the increase in the target load LS to the target value L2, the actual load LI1 or LI2 is built up with a physically caused time delay. The aim is to follow the target load LS as closely as possible. The limiting factor here is the available fresh air charge, which must be increased to achieve the new target load LS=L2. The charge provided is increased, for example, via a throttle valve or an exhaust gas turbocharger. This is achieved, for example, by increasing the pressure in front of the cylinder. The pressure increases as soon as the target load increases, since the pressure equalization takes place at the speed of sound. The reduction in the EGR rate, on the other hand, is delayed because the air already in the intake manifold and mixed with EGR first has to be displaced by the newly provided air without EGR. The load jump therefore consists of two phases, first phase P1-1 with EGR and then phase P2-1 without EGR.

For a dynamic load build-up that is as fast as possible, the filling provided should arrive in the cylinder as unhindered as possible, so it makes sense to position the actuator POSopt optimally for filling. As a result of the method according to the invention, the actuator (cf. POS2) is already in an advantageous position POSopt at low loads L and can be held in this position for the duration of the sudden change in load. The conventional POS1, ARG1 method does not offer this advantage to the same extent. This means that an increase in the filling of the method according to the invention in this exemplary embodiment results in a greater mass in the cylinder due to the advantageous position POSopt of the actuator. In the first phase of the load build-up using the method according to the invention, this results in the advantage that the actual load LI2 increases more quickly than with the conventional method (cf. L11). The higher EGR rate AGR2 of the method according to the invention compared to the EGR rate AGR1 of the conventional method in this first phase is not a hindrance here, since both starting points in state Z1 have the same performance.

Furthermore, the EGR rate should be reduced as quickly as possible for the fastest possible load build-up. The volume of the intake manifold, which is filled with the mixture of air and recirculated exhaust gas, can be selected in the method according to the invention just as in the conventional method. Likewise, the increase in pressure can be the same as in the conventional method. The position of the actuator therefore decides how much mixture volume per unit of time is consumed by the cylinder. The EGR rate therefore has no influence on how long the phase lasts in which recirculated exhaust gas arrives in the cylinder. According to the invention, the duration of phase P1-2 with exhaust gas recirculation is thus shortened compared to the known methods (cf. P1-1). According to the invention, phase P2-2 without exhaust gas recirculation, in which only air arrives in the cylinder and the load increase is therefore greater, begins earlier than in the known methods (cf. P2-1).

Finally, according to the invention, in phase P2-2 without EGR, the actuator is in a position POSopt with greater filling until the target load L2 is reached. The increase in load is therefore greater than with the conventional method. After reaching the target load LS, the state Z2, no further increase in performance is desired and in both cases (Z2-1, Z2-2) the actuators are in the same, stationary, reduced-fill position POS red off 6 brought. In the method according to this exemplary embodiment, the load jump is therefore ended more quickly, is more efficient with higher EGR rates, and the most efficient setting for steady-state operation can be adopted more quickly.

In the method according to the invention described here, it is advantageous that the actuator moves to an optimized position according to the method according to the invention (POSopt in 6 ) is provided. However, there is still a time delay because the actuator must first be used in position. The structural design of the intake manifold is the same as with the conventional method.

8th shows a more realistic progression POS1, POS2 of the actuator compared to the previous consideration 6 . The optimum position of the actuator for the case without EGR is shown as POSO, with a more realistic curve than the constant curve of the 6 Is accepted. The optimal position POSO of the actuator for the case without EGR is closer to the optimized actuator position POSopt for the target load L2 than for the initial load L1. With increasing load L, the filling cannot be increased to a sufficient extent, the actuator is therefore advantageously clearly shifted in the direction of the optimal filling position POSopt with increasing load (L>Lh) even without EGR. This makes it clear that it is also advantageous, when the second state Z2 is reached, to shift the actuator significantly in the direction of optimum filling, even in the stationary case. A backward displacement of the actuator when state Z2 (target load L2) is reached may only be necessary to a small extent or not at all. The dot-dash line POS3 shows a further possible advantageous form of the target actuator position, in which the advantages are retained, but the abrupt change only occurs in the EGR rate.

In a further development, depending on the direction, the transition can be different. In the event of a load increase, the POS2 trajectory with an advantageous actuator position POSopt can be used, and in the event of a load decrease, the conventional POS1 trajectory can be used without a sudden change. Alternatively, the abrupt transition POS2 can be provided with a hysteresis, so that it occurs at a different load depending on the load increase or decrease. This means that the advantages can be used as required and at the same time good controllability can be maintained where necessary.

In a further form, it is possible to design the form of the curves as a function of the engine speed.

In a further embodiment, it is possible in a vehicle with a manual transmission (manual or automatic) to design the characteristics of the curves as a function of the selected gear.

In a further form, it is possible in a vehicle with an automatically shifting transmission to design the form as a function of the transmission shift behavior (e.g. normal or sport).

In a further embodiment, it is possible to combine the method with a vehicle with a continuously variable transmission (e.g. mechanical CVT transmission) or a continuously variable hybrid drive train (e.g. serial-parallel hybrid). The advantageous method is used to its full extent, and good controllability is achieved by adjusting the speed using the infinitely variable adjustability. For example, the jump can only be carried out if the load requirements are very high, while only a speed adjustment takes place with moderate load requirements and the advantages of an increased EGR rate in L1 can be used.

The processing of target values for the EGR rate and the actuator, as indicated by the exemplary embodiments above, in an engine controller can be performed according to methods well known to those skilled in the art. For example, one or more maps, which the course of the target values according to the embodiments 6 and 8th be stored in the motor control. During the operation of the internal combustion engine, the engine control system knows the current engine load or filling, takes the corresponding target values from the map or maps and makes the appropriate settings using standard methods, so that the corresponding actual variables achieve the target specifications as optimally as possible. As an alternative to using characteristic diagrams, the person skilled in the art can also implement an algorithmic conversion of the curves.

In the exemplary embodiments above, in order to make the driving-dynamic relationships easier to see, the course of the setpoint values for the EGR rate and actuator position is plotted as a function of the load, ie the torque of the internal combustion engine. In the implementation of the invention, however, it is preferred to describe the course of the target values directly as a function of the filling of the internal combustion engine, for example in one or more characteristic curves, which assign the desired target filling to the respective target values for EGR rate and actuator position, while the Load (expressed as, for example, torque) is modeled based on charge and other parameters. The invention is therefore not limited to a load-dependent representation, but can also be implemented in an equivalent manner by referring to the filling, or by referring to any variable that expresses the load, for example any variable that is proportional to the torque. For example, the load is expressed by the driver's request, which is given by the setting of the accelerator pedal (angle, etc.). The driver's request conveyed by means of the gas pedal is converted into a target load or a torque request. This load or this torque request corresponds (via the known model relationship) to a setpoint charge, which is converted, for example, by means of characteristic curves into setpoint values for the EGR rate and actuator position, which are implemented as well as possible.

Reference List

101

air filter

102

exhaust gas turbocharger

103

Low pressure EGR valve

104

intercooler

105

EGR filter

107

outlet

108

catalytic converter (exhaust aftertreatment)

109

High pressure EGR valve

110

combustion engine

111

engine intercooler

112

air control flap (throttle flap)

113

Camshaft phasing

201

engine control

ITEM1

load-dependent target values for the position of the actuator (conventional)

POS2

load-dependent target values for the position of the actuator (example)

POS3

load-dependent target values for the position of the actuator (example)

POSred

filling-reduced actuator position

POSopt

filling-optimized actuator position

EGR1

load-dependent target values for EGR rate (conventional)

EGR2

load-dependent target values for EGR rate (example)

EGR max

maximum EGR rate

L1

Output load in load step

L2

Target load in the load jump

Lh

Load for sudden reduction in EGR rate

Lmax

maximum load

L, LI1, LI2

actual load

LS

dynamic load specification

t

Time

Z1-1, Z1-2

State before load jump

Z2-1, Z2-2

State after load jump

P1-1, P1-2

Phase with exhaust gas recirculation

P2-1, P2-2

Phase without exhaust gas recirculation

Claims (11)

Control for an internal combustion engine (110) with exhaust gas recirculation (109) and at least one actuator (113) for influencing the filling of the internal combustion engine (110), the control being designed to load or filling-dependent desired values (EGR2) for the at least one actuator ( 113) and the EGR rate (AGR2) of the exhaust gas recirculation (109) in such a way that the target values (AGR2) for the EGR rate are reduced quickly or abruptly with increasing load (L) or filling. control after claim 1 , which is set up to reduce the EGR rate (AGR2) quickly or abruptly from a predetermined load (Lh) or corresponding filling, so that a range (Lh to Lmax) without exhaust gas recirculation is created. control after claim 2 , the range in which no exhaust gas recirculation is operated begins 1 bar, preferably 2 bar and even more preferably 3 bar before the maximum load (Lmax). control after claim 2 , whereby the specified load (Lh) or corresponding charge, from which the target EGR rate (AGR2) is reduced quickly or abruptly, is selected in such a way that a shift to a higher load (L) or Filling can no longer generate any further consumption benefit. Control according to one of the preceding claims, wherein the gradient of the jump in the EGR rate is, for example, 7% per bar, preferably ter is 10% per bar, and more preferably 12% per bar mean effective pressure. Controller according to one of the preceding claims, which is set up to place the actuator (113) in a charge-reduced position (POSred) opposite to the reduction in the EGR rate (AGR2). Controller according to one of the preceding claims, which is set up to set a target position (POS2) of the actuator (113) to a filling-optimal position (POSopt). control after claim 7 , which is set up to hold the actuator (113, POS3) in the filling-optimized position (POSopt) from the rapid or abrupt reduction in the EGR rate (AGR2) until a maximum load (Lmax) is reached. Control according to one of the preceding claims, which is set up to keep the EGR rate (AGR2) as high as possible before the rapid or abrupt reduction in the EGR rate (AGR2). The controller of any of the preceding claims, wherein the controller is configured to maintain the EGR rate at least 7%, more preferably at least 10%, and even more preferably at least 12% prior to the rapid or ramped reduction. Method for operating an internal combustion engine (100) with exhaust gas recirculation (109) and at least one actuator (113) for influencing the filling of the internal combustion engine (110), the method prescribing load-dependent or filling-dependent desired values (EGR2) for the at least one actuator ( 113) and the EGR rate (AGR2) of the exhaust gas recirculation (109) in such a way that the target values (AGR2) for the EGR rate are reduced rapidly or abruptly as the load (L) or charge increases.

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