EP3221573B1 - Control device for an internal combustion engine - Google Patents

Description

The present invention relates to a control device for an internal combustion engine for determining at least one reference variable for an internal combustion engine.

Control units are used to control important engine functions in the vehicle area. In particular, they also serve to complement structural measures such as combustion chamber design and the influence of mixture formation through injection systems and injection processes, engine operation, fuel consumption and the associated CO ₂ emissions as well as essential exhaust gas components such as carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides ( NOx) as well as soot and particles.

Known functions of a control unit receive information about an operating state of the engine (for example speed, torque, desired torque, temperature, DPF (diesel particle filter) loading and determine reference variables that influence consumption and emissions during operation.

Engine control maps stored in the control unit, in which, for example, a target exhaust gas recirculation rate or a target boost pressure as a function of the above-mentioned operating state are stored, are often used to determine these reference variables.

Suitable command variables are, for example, exhaust gas recirculation rate, exhaust gas recirculation distribution, filling, injection timing, ignition timing. Control variables are then derived from these reference variables (for example throttle valve position, position of a VTG (variable turbine geometry)).

In this context, the term “internal combustion engine” encompasses the complete internal combustion engine system with all of its units, auxiliary units and adjusting elements.

This strategy can be used to ensure that the emission limits in defined speed profiles are not exceeded by an optimized allocation of certain reference variables. An example of such speed profiles are normalized Driving cycles, for example the NEDC (new European driving cycle), which are used to determine the exhaust gas and / or consumption values. For such cycles, global optimization approaches are known, for example, as specified in Heiko Sequence: Emission Modeling and Model-Based Optimization of the Engine Control, D17 Darmstadt Dissertations 2012.

Furthermore reveal DE 10 2006 007122 A1 and US 2011/264353 A1 Approaches for optimizing emission values. Optimization procedures, for example based on pareto-optimal alternatives, are also in R. Timothy Marler ET AL: "The weighted sum method for multi-objective optimization: new insights", Structural and Multidisciplinary Optimization, Vol. 41, No. 6, pp. 853-862 described.

Any number of different speed profiles and operating states that are not known before and during the trip now occur in real driving mode (and possibly in so-called real driving emissions test methods).

Since the individual operating states already have different emission values regardless of the engine control system, the consumption and emission values (l / 100km or mg / km) can deviate significantly upwards or downwards in some of these different driving profiles. A global optimization of, for example, fuel consumption or CO2 emissions when the emission limits are not exceeded is therefore no longer provided by the known control strategies.

Particularly in the case of competing emission values, such as those that occur in soot (particulate) emissions and nitrogen oxide emissions in a diesel engine, situations can arise in which, for example, the permissible nitrogen oxide emissions are exceeded in a speed profile and the permissible soot emissions are clearly undercut.

It is therefore the task of providing a control unit for an internal combustion engine with a function that at least partially solves the problems described above and is suitable, the reference variables such as exhaust gas recirculation rate (EGR rate) and EGR distribution in real driving emission test methods (High pressure / low pressure), filling, rail pressure, but also the use of exhaust gas aftertreatment systems such as diesel particulate filter and SCR (selective catalytic reduction) with regard to fuel and AdBlue consumption as well as the emission variables.

This object is achieved by the control device according to the invention according to claim 1, an internal combustion engine according to claim 6 and a vehicle according to claim 7.

Further advantageous embodiments of the invention result from the subclaims and the following description of preferred exemplary embodiments of the present invention.

A control device of an internal combustion engine according to the invention determines a reference variable (for example EGR rate, EGR distribution, charge), which is output to the internal combustion engine, taking into account operating status information, upper emission limits and a cumulative actual emission quantity.

The operating status information includes, for example, the speed, the current torque, the desired torque, the temperature, the DPF loading and other variables.

The cumulative actual emission size comprises the sum of all emissions emitted by the internal combustion engine in a certain operating period.

At least one operating state of the internal combustion engine is set via this reference variable (s) in such a way that a plurality of actual emission variables are influenced in such a way that the cumulative actual emission variables in a specific operating period with a combination of any operating states of the internal combustion engine emission limits set in a random order for this operating period do not exceed (mg / km) and a target function is reduced as much as possible. Here, a size to be minimized or optimized is referred to as the objective function (e.g. fuel consumption or the CO ₂ emissions dependent on it, regeneration intervals of various exhaust gas aftertreatment systems such as soot particle filters, AdBlue consumption, NOx emissions etc. or a combination of such sizes).

The term “any” operating states is intended to encompass all technically sensible operating states that can occur in the normal operation of an internal combustion engine.

Such a control concept has the advantage that, for example, a non-critical actual emission quantity is increased by changing the reference quantity to such an extent that a critical actual emission quantity is reduced to such an extent that it is ensured that the emission limit level (emission limit value) of an emission quantity for the critical one Emission size not reached or not exceeded in a period.

One or more reference variables are selected using an indifference curve from pareto-optimal alternatives - for example, the injection quantity, actual emissions and / or AdBlue dosing. This is done according to a heuristic that takes into account the distances between the accumulated actual emissions and their limit level. The In this process, the command variable is determined and adapted dynamically and depending on the situation.

There are versions in which the operating status information includes at least one speed (n) and a target torque (M).

In one embodiment, the actual emission quantities include at least two of the following quantities. Sizes include NOx emissions, HC emissions, CO emissions, CO ₂ emissions, combined HC and NOx emissions, number of soot particles, soot particle mass, condition of a diesel particle filter, condition of a NOx storage catalytic converter.

The command variable comprises at least one of the following variables that affect the emission behavior, namely EGR rate, EGR distribution, filling, ignition timing. The manipulated variables derived therefrom include one of the following variables, by means of which the desired command variable can be achieved in modern engines, namely throttle valve position; Setting the variable turbine geometry, injection timing, camshaft adjustment.

In another embodiment, two actual emission quantities are considered, in particular nitrogen oxide emissions and soot emissions, which are competingly related to diesel engines.

With the help of an internal combustion engine with a control device according to the invention, improved consumption values and emission values can be realized. Such an internal combustion engine is particularly suitable for vehicles.

Fig. 1

schematisch ein Motorsystem mit einem erfindungsgemäßen Steuergerät;

Fig. 2

eine schematische Darstellung von Input- und Output-Größen, sowie der Informationsverarbeitung eines erfindungsgemäßen Steuergeräts;

Fig. 3

ein Diagramm, in dem Ruß- und NOx-Emissionen in Abhängigkeit der AGR-Rate dargestellt sind;

Fig. 4

pareto-optimale Arbeitspunkte, für die eine bestimmte Rußemission und eine bestimmte NOx-Emission gilt;

Fig. 5

Auswahl einer Führungsgröße durch eine Indifferenzkurve basierend auf dem Zusammenhang von Rußemissionen und NOx-Emissionen bei einer bestimmten (erhöhten) kumulierten NOx-Emission;

Fig. 6

die in Fig. 5 dargestellte Auswahl für eine niedrigere kumulierte NOx-Emission;

Fig. 7

die in Fig. 5 dargestellte Auswahl für eine überhöhte kumulierte NOx-Emission;

Fig. 8

die in Fig. 5 dargestellte Auswahl basierend auf dem Zusammenhang von CO2- und NOx-Emissionen;

Fig. 9

die in Fig. 5 dargestellte Auswahl durch eine nichtlineare Indifferenzkurve;

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings. It shows:

Fig. 1

schematically an engine system with a control device according to the invention;

Fig. 2

a schematic representation of input and output variables, and the information processing of a control device according to the invention;

Fig. 3

a diagram showing soot and NOx emissions as a function of the EGR rate;

Fig. 4

pareto-optimal operating points for which a specific soot emission and a specific NOx emission apply;

Fig. 5

Selection of a reference variable by means of an indifference curve based on the relationship between soot emissions and NOx emissions for a specific (increased) cumulative NOx emission;

Fig. 6

in the Fig. 5 illustrated selection for a lower accumulated NOx emission;

Fig. 7

in the Fig. 5 illustrated selection for an excessive cumulative NOx emission;

Fig. 8

in the Fig. 5 Selection shown based on the relationship between CO2 and NOx emissions;

Fig. 9

in the Fig. 5 selection represented by a nonlinear indifference curve;

In Fig. 1 An engine diagram is shown, which is regulated or controlled via a control device 1 according to the invention. Shown is an internal combustion engine designed as a reciprocating piston engine 2 (diesel or Otto engine), which is filled via valves 3 and via a charge air line 4 and is emptied via an exhaust line 5. The supply air passes through an air filter 6 and an exhaust gas turbocharger 7 with adjustable turbine geometry through an intercooler 8 via an inlet valve 3 into the cylinder, where fuel may be supplied via an injection system. After the compression and combustion of the air-fuel mixture, the exhaust gas formed is discharged through an exhaust valve 3 via the exhaust line.

The compressed exhaust gas passes the exhaust gas turbocharger 7, drives it and thus compresses the charge air. It then passes through a nitrogen storage catalytic converter 10 and a diesel particle filter 11 and finally reaches the exhaust pipe 13 through an exhaust gas flap 12.

The valves 3 are driven by an adjustable camshaft 14. The adjustment takes place via a camshaft adjusting device 15, which can be controlled by control unit 1.

Part of the exhaust gas can be introduced into the charge air duct 4 via a high-pressure exhaust gas recirculation valve 16. An exhaust gas-treated partial flow can in the low pressure area after the exhaust gas turbocharger 7 via a corresponding exhaust gas cooling 17 and an exhaust gas recirculation low pressure valve 18 are guided in the charge air line 4. The turbine geometry of the exhaust gas turbocharger 7 can be adjusted via an adjusting device 19. The charge air supply ("gas") is regulated via the main throttle valve 20.

The control unit 1 includes the exhaust gas recirculation low pressure valve 18, the actuating device 19, the main throttle valve 20, the exhaust gas recirculation high pressure valve 16, the camshaft adjusting device 15 and the exhaust gas flap 12 can be controlled (solid lines).

Furthermore, the control unit 1 is supplied via sensors and setpoint devices, for example with temperature information (intercooler 8, exhaust gas cooling 17) and with actual emission values (e.g. from a sensor or physical / empirical model).

In addition, there may be additional operating status information such as: accelerator pedal position, throttle valve position, air mass, battery voltage, engine temperature, crankshaft speed and top dead center, gear stage, vehicle speed.

There is therefore a complex control system that is intended to set, regulate and optimize engine operation in a wide variety of operating states with regard to different target variables.

The following exemplary embodiments relate to the control and regulation of emission values as a function of predefined upper emission limits and cumulative actual values.

Such a basic system is in Fig. 2 shown. The control unit 1 determines one or more effective and effective reference variables x (t) required to influence the emissions.

From this, manipulated variables are derived which in the internal combustion engine 2 or its components (for example position of the main throttle valve 20, camshaft setting, setting of the turbine geometry of the exhaust gas turbocharger 7, setting of the exhaust gas valve 12, etc.) are the emissions (for example NOx, HC, CO, soot ) of the internal combustion engine. These are recorded as mass flows (emission rates) Em ^DS (for example mass per time [mg / s]). Cumulative actual values Em ^{K of} the emissions are derived from these emissions (integration of the emission rates over time).

These cumulative actual values Em ^K are used in control unit 1 together with the elapsed operating time t or the distance s traveled, known or specified upper emission limits Em ^G and information about the driver's request FW (eg acceleration: a ^target ; torque: M ^target ) and other operating conditions SB (eg speed: v; speed: n) of the internal combustion engine 2 determines the reference variable (n) x (t).

Fig. 3 shows an example of the relationship between NOx emissions and soot emissions as a function of the exhaust gas recirculation rate (EGR), which forms a reference variable x (t) here. The diagram shows that increasing the EGR can reduce the NOx emissions, but increase the soot emissions.

Fig. 4 shows a diagram with reference variable combinations of certain soot emissions, which are plotted against certain NOx emissions. If, for example, there is now the task of minimizing / reducing the soot emissions in an (any) operating state, while maintaining a (cumulative) NOx limit value, the emission history (cumulative actual values Em ^G ) for past (possibly any, in different operating states).

Pareto-optimal target size combinations, in which soot emissions can only be further reduced if the NOx emission is increased, are identified by the points x. All Pareto-optimal target size combinations form the so-called pareto front, which connects the points x to one another. In the event of a minimization problem, points to the left below the Pareto front (hatched area) cannot be realized and all target size combinations provided to the right above are not Pareto-optimal, since there are combinations (points x) in each case that relate to soot emission and NOx emission can be realized more cheaply on the pareto front.

The selection from pareto-optimal target size combinations of two target sizes (NOx emissions and soot emissions) is shown in Fig. 5 . A NOx limit value NOx-G (dashed line) is shown in the right column as the upper emission limit Em ^G and the column shown below shows the accumulated actual NOx emissions NOx-K ₁ in the shaded area as the accumulated actual value Em ^K. Since the cumulative NOx emissions NOx-K _{1 are} already relatively close to the NOx limit value NOx-G, a relatively high exchange ratio between the target values soot emissions and NOx emissions (increased soot emissions in favor of low NOx) has been chosen around the NOx - NOx-G limit not To exceed. This exchange rate desired here is indicated by the indifference curve I, which is shown here to decrease relatively steeply, and is then shifted to the closest target size combination, in which a specific soot emission and a specific NOx emission can be realized for this operating point. This target size combination is then determined using the in the diagram Fig. 3 known information is assigned an EGR as a suitable pareto-optimized reference variable x (t).

Fig. 6 shows an example in which the accumulated NOx emissions (NOx-K ₂ ) are further below the NOx limit value NOx-G. Here the exchange ratio of the indifference curve I is smaller (the straight line falls flat). A higher NOx emission can therefore be accepted here without there being any risk that the NOx limit value NOx-G will be exceeded. The soot emission can thus be kept lower. The flatter straight line is shifted to the next target size combination, on which a certain NOx emission and a corresponding soot emission with an associated reference variable x (t) (here the corresponding EGR) Fig. 3 ) can be realized.

Fig. 7 shows an example in which the accumulated NOx emissions (NOx-K ₃ ) have exceeded the NOx limit value NOx-G. Here the exchange ratio of the straight line I (vertical indifference curve) is almost infinite. Regardless of the level of soot emissions, the reference variable x (t) is selected for minimal NOx emissions.

Fig. 8 shows analog to Fig. 5 an example in which CO ₂ should be minimized depending on the accumulated NOx emissions.

Fig. 9 shows analog to Fig. 5 an example in which the indifference curve is not linear.

With the approach shown, the emission values (target functions) can be improved in operation and depending on changing boundary conditions. In addition to the problems presented here, in which emission quantities were taken into account in pairs, the method can also be extended to multidimensional problems. For example, it is possible to determine pareto-optimized reference variables x (t) for multiple combinations (e.g. for CO ₂ emissions, soot emissions and NOx emissions). In addition to the reference variable AGR, other reference variables x (t) pareto-optimized can also be determined for control purposes (e.g. VTG position or rail pressure).

Reference list

1

Control unit

2nd

Reciprocating engine

2a

transmission

3rd

Valves

4th

Charge air line

5

Exhaust line

6

Air filter

7

Exhaust gas turbocharger

8th

Intercooler

9

cylinder

10th

NOx storage catalytic converter

11

Diesel particulate filter

12th

Exhaust flap

13

Exhaust

14

camshaft

15

Camshaft adjustment device

16

EGR high pressure valve

17th

Exhaust cooling

18th

EGR low pressure valve

19th

Actuator

20th

Main choke

x (t)

Leadership variable

NOx-G

limit

NOx-K ₁

accumulated actual value

FW

Driver request

SB

Other operating conditions

EM ^G

Emission ceiling

EM ^K

cumulative emission values

EM ^DS

Throughputs

I.

Indifference curve

Claims (7)

1. Control unit (1) for an internal combustion engine (2), with a function which determines, with consideration of an operating state information item (FW, SB)

   - of an upper limit and

   - of a cumulative actual variable, the cumulative actual variable comprising the sum of all the emissions emitted by the internal combustion engine in a defined operating time period,
   a command variable (x(t)) which comprises at least one of the variables of EGR rate, EGR distribution, filling, boost pressure, injection time, ignition time or rail pressure and influences an operating state of the internal combustion engine (2) in such a way that a plurality of actual variables are set in such a way that cumulative actual variables in an operating time period with a combination of any desired different operating states of the internal combustion engine (2) which are set in a random sequence do not exceed upper limits for the said operating time period, a target function which comprises at least one actual emissions variable (Em^DS), a fuel consumption and/or a CO₂ emission, by the command variable (x(t)) being selected from pareto-optimal alternatives by means of an indifference curve (1) with consideration of a separation of the cumulative actual variable from the upper limit.
2. Control unit (1) according to Claim 1, the operating state information item (SB, FW) comprising a rotational speed (n(t)) and a setpoint torque (MSoll(t)).
3. Control unit (1) according to Claim 1 or 2, the operating time period and the different operating states of a journey being known.
4. Control unit (1) according to Claim 1, 2 or 3, the actual emissions variables (Em^DS) comprising at least two of the following variables: NOx emission, HC emission, CO emission, CO₂ emission, combined HC and NOx emission, soot particle quantity, soot particle mass, AdBlue consumption.
5. Control unit (1) according to Claim 1, 2, 3 or 4, at least two actual emissions variables (Em^DS), in particular NOx emission and soot emission, being considered.
6. Internal combustion engine (2) with a control unit (1) according to Claim 5.
7. Vehicle with an internal combustion engine (2) according to Claim 6.

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