DE102019103688A1 - Model-based boost pressure control of an internal combustion engine - Google Patents

Abstract

The invention relates to a control device and a method for regulating the boost pressure of an internal combustion engine (1) with an exhaust gas turbocharger (2), having the steps: - (S210) determining a setpoint (pL, soll) for a boost pressure (pL) downstream of the compressor of the exhaust gas turbocharger, - (S320) Determination of a manipulated variable for a boost pressure regulator (18) on an exhaust gas turbine side of the exhaust gas turbocharger, on the basis of the determined setpoint value for the boost pressure and as a function of an actual value (pL, ist) of the boost pressure (S221) and of at least one modeled influencing variable ( S 222) by means of a model-based boost pressure control (S 220).

Description

The invention relates to a method and a control device for regulating the boost pressure of an internal combustion engine, as well as an internal combustion engine with at least one exhaust gas turbocharger and such a control device. The invention can be applied both to Otto engines and to diesel engines, in particular if these have exhaust gas charging.

In current internal combustion engines, the boost pressure control cannot be operated during higher-load accelerations without limitations on the actuator side, since otherwise the gas exchange losses would be too great and thus the driving dynamics would be adversely affected.

The possibly necessary limitation of the manipulated variable of the actuator (s) of the boost pressure control - for example, a duty cycle of a flap on a turbine bypass of the exhaust gas turbocharger or a setting angle of variably adjustable guide vanes of the exhaust gas turbine - is carried out on the basis of operating point-dependent maps.

In such a characteristic map of a known boost pressure control, for example, a maximum permitted value of the manipulated variable can be specified for different combinations of engine speed and injected fuel quantity per stroke.

During high-load accelerations, the boost pressure regulation is then in principle deactivated and the actuators of the boost pressure regulation are operated in a controlled manner based on the maximum limits from the filled map.

The application of the limiting maps is often essential for the achievable driving dynamics. The attempts to parameterize the maps are very time-consuming and place high demands on the starting conditions. In addition, with this form of maximum limitation with regard to the manipulated variable, no environmental conditions from the operation of the internal combustion engine (e.g. changed air density over altitude or outside temperature) or only with significant additional effort, no component scatter (e.g. on the turbine of the exhaust gas turbocharger) and no aging effects can be taken into account .

A conservative application of the limiting map is therefore necessary in order to maintain a sufficient limitation in all cases, which, however, entails compromises at the expense of the achievable driving dynamics.

An example of such applications of limit maps is in DE 10 2006 009 864 A1 which proposes a method for adjusting a turbine flow cross section of a turbocharger of an internal combustion engine. In unsteady operating states, a lower limit for the turbine flow cross section is determined as a function of an operating parameter of the internal combustion engine and a speed of the internal combustion engine is used as the operating parameter. The dependency can be predetermined in such a way that a scavenging gradient (that is to say a pressure difference between the boost pressure and the exhaust gas back pressure) of the internal combustion engine does not exceed a predetermined maximum value.

Against this background, it is an object of the invention to improve a boost pressure control of an internal combustion engine.

This object is achieved by a method for boost pressure control of an internal combustion engine with the features of claim 1 and by a control unit for boost pressure control of an internal combustion engine with the features of claim 10. An internal combustion engine with an exhaust gas turbocharger is protected in claim 12. The dependent claims relate to advantageous embodiments of the invention.

According to one aspect of the invention, a method for boost pressure control of an internal combustion engine with an exhaust gas turbocharger is provided, comprising the steps: 1) Determining a setpoint value for a boost pressure on a compressor side of the exhaust gas turbocharger, in particular after the compressor. 2) Determining a manipulated variable for a boost pressure actuator (this means: determining a value of an adjusting parameter that results in particular from the type of boost pressure actuator) on an exhaust gas turbine side of the exhaust gas turbocharger, in particular upstream of the exhaust gas turbine of the determined setpoint for the boost pressure and as a function of an actual value of the boost pressure and at least one modeled influencing variable (in particular on the boost pressure and / or a development of the boost pressure) by means of a model-based boost pressure control. The model-based boost pressure control also takes place as a function of a, in particular predetermined, setpoint value for an exhaust gas back pressure. For example, the target value for the exhaust gas back pressure results from the current boost pressure and a previously applied maximum scavenging gradient.

According to a further aspect of the invention, a control device for boost pressure regulation of an internal combustion engine with an exhaust gas turbocharger is provided, which is configured to 1) determine a setpoint value for a boost pressure on a compressor side of the exhaust gas turbocharger, and 2) a manipulated variable for a boost pressure actuator on an exhaust gas turbine side of the To determine the exhaust gas turbocharger on the basis of the determined setpoint for the boost pressure and as a function of an actual value of the boost pressure and at least one modeled influencing variable by means of a model-based boost pressure control. The control unit is set up to also carry out the model-based boost pressure regulation as a function of a setpoint value for an exhaust gas back pressure. For example, the target value for the exhaust gas back pressure results from the current boost pressure and a previously applied maximum scavenging gradient. According to one embodiment, the control device is set up to carry out a method according to individual or any embodiments of the invention.

According to a further aspect of the invention, an internal combustion engine with an exhaust gas turbocharger and a control device according to an embodiment of the invention is provided.

The invention is based, inter alia, on the consideration that with the known boost pressure controls, which are limited with absolute control values in transient high-load operation, the effects of environmental conditions, component scatter and aging on the boost pressure control cannot be mapped well. This makes it more difficult to operate the internal combustion engine that is optimized for environmental conditions and driving dynamics. The inventors noticed that, against this background, it could not make sense to subordinate the model-based boost pressure control for certain operating cases - in particular the transient, higher load operation - to an absolutely limited characteristic value operation, as is the case with common boost pressure controls.

The invention is based, among other things, on the idea of specifying a thermodynamically motivated engine variable such as the scavenging gradient as a function of an engine operating point and introducing this as a suitable variable directly into the model-based boost pressure control, instead of simply using this variable methodically for the data on a characteristic map specifies an absolute value for a manipulated variable restriction for each engine operating point.

The model-based boost pressure control then determines from the variable determined from the flushing gradient and from other parameters, e.g. the exhaust gas back pressure sensor, automatically the maximum pulse duty factor, the minimum turbine area or the minimum bypass area. In the context of the invention, the manipulated variable is calculated as an integral part of the model in the controller, taking into account the maximum permissible flushing gradient.

With known boost pressure controls - for example, according to DE 10 2006 009 864 A1 - on the other hand, the limitation only takes place after the manipulated variable has been calculated by the boost pressure regulator. The solutions known today aim at a meaningful dimensioning of the (necessary) manipulated variable limits following the actual boost pressure control, while the boost pressure control according to embodiments of the invention physically limits the scavenging gradient as an integral part of the boost pressure control.

The boost pressure control according to embodiments of the invention ensures that the boost pressure control or the limitation of the flushing gradient is independent of environmental conditions, component variations, aging, wear, etc. Furthermore, according to one embodiment, the maximum permissible flushing gradient can be achieved exactly, whereas this robustness is not given in known solutions.

Furthermore, this can be used for example in the DE 10 2006 009 864 A1 The switchover described between a limitation for the stationary and dynamic operation of the internal combustion engine is omitted.

In addition, the limitation maps described at the beginning, which are complex to apply, can be dispensed with. The application of a scavenging gradient characteristic map in which, for example, a maximum pressure value for the scavenging gradient is recorded for various combinations of an engine speed and a fuel quantity per stroke, requires significantly less effort. Such a characteristic map can possibly, at least as a first approximation, be determined from data that are already present in the digital operating model of the engine.

According to one embodiment, a maximum permissible, operating point-dependent pressure difference between the engine inlet and outlet is specified. In particular in highly dynamic processes, this operating point-dependent pressure difference can still be corrected according to one embodiment using the gradient of the actual pressure difference.

The maximum permissible exhaust gas back pressure can be determined, for example, from adding the boost pressure and the specified flushing gradient and / or another suitable relationship between these variables. A maximum permissible exhaust back pressure can be taken into account in the boost pressure control of the common system manufacturers so that the maximum permissible differential pressure of the specified flushing gradient is maintained.

The model-based boost pressure control can then remain active even during high-load accelerations. The driving dynamics can be based on a thermodynamically motivated variable be applied. Tests on the applicant's engine test bench or in test vehicles show that the method provided within the meaning of the invention can be applied much more easily. Deviating effects of environmental conditions, component variations and aging can almost be ruled out with a boost pressure control according to one embodiment of the invention, since the boost pressure control remains active. In addition, disruptive influences on the air mass and EGR rate regulation can be reduced.

In order to support boost pressure regulation in various conceivable operating situations of the internal combustion engine, according to one embodiment, the setpoint value for an exhaust gas back pressure in turn depends on an engine operating point.

In order to reduce or exclude a negative effect of the boost pressure regulation on the acceleration behavior of the internal combustion engine, according to one embodiment the setpoint for the exhaust gas back pressure relates to a maximum permissible exhaust gas back pressure. This exhaust gas back pressure determines what compression work the associated piston has to perform when the exhaust gases are pushed out. The higher this compression work, the less torque the piston can deliver to the crankshaft as acceleration work. Consequently, it makes sense to define a maximum for the exhaust gas back pressure in the case of high-load acceleration, at which the pushing-out work to be performed by the piston is still in a non-disruptive range.

Because the acceleration behavior of the internal combustion engine does not depend exclusively on the exhaust back pressure, according to one embodiment the setpoint for the exhaust backpressure is determined on the basis of a predetermined maximum permissible scavenging gradient, so that the relevant influences are included in the determination of the setpoint for the exhaust backpressure.

In order to be able to support the boost pressure regulation in the entire operating spectrum of the internal combustion engine, according to one embodiment the setpoint value for the exhaust gas back pressure, in particular the maximum permissible scavenging gradient, is determined, in particular predetermined, as a function of an engine operating point. A corresponding scavenging gradient map can, for example, record a maximum pressure value for various combinations of an engine speed and a fuel quantity per stroke.

In order to be able to adapt the boost pressure control to real deviations from a digital operating model of the engine (and the operating models stored there for the parameters involved), according to one embodiment, the model-based boost pressure control is carried out, in particular additionally, depending on an actual value of the flushing gradient. In order to be able to better regulate transient operating cases of the internal combustion engine, according to one embodiment the model-based boost pressure regulation takes place, in particular additionally, as a function of a gradient of the actual value and / or the setpoint of the scavenging gradient.

In order to be able to take into account the effects of an operating point-dependent exhaust gas recirculation, according to one embodiment the model-based boost pressure regulation takes place, in particular additionally, as a function of an EGR rate.

In known internal combustion engines, the boost pressure can be regulated by one or more, but in any case by different actuators. According to different embodiments, a closure flap of an exhaust gas bypass and / or a closure flap of an exhaust gas recirculation and / or a guide vane of the exhaust gas turbine can therefore be provided as the charge pressure regulator.

• 1 zeigt schematisch einen Verbrennungsmotor mit einem Abgasturbolader und einem Steuergerät nach einer beispielhaften Ausführung der Erfindung.
• 2 zeigt einen vereinfachten Regelkreis eines bekannten Verfahrens zur Ladedruckregelung des Verbrennungsmotors aus 1.
• 3 zeigt einen vereinfachten Regelkreis eines Verfahrens zur Ladedruckregelung des Verbrennungsmotors aus 1 nach einer beispielhaften Ausführung der Erfindung.

Further advantages and possible applications of the invention emerge from the following description in connection with the figures.

• 1 shows schematically an internal combustion engine with an exhaust gas turbocharger and a control device according to an exemplary embodiment of the invention.
• 2 FIG. 11 shows a simplified control loop of a known method for regulating the boost pressure of the internal combustion engine 1 .
• 3 shows a simplified control loop of a method for regulating the boost pressure of the internal combustion engine 1 according to an exemplary embodiment of the invention.

In 1 is an internal combustion engine 1 with an exhaust gas turbocharger 2 and a control unit 100 an exemplary embodiment of the invention shown.

The internal combustion engine 1 has a plurality of cylinders, each with a combustion chamber 4th on, of which in 1 for the sake of simplicity only one is shown. The combustion chamber 4th is from a piston 6th movably sealed. The internal combustion engine 1 is either a gasoline engine, in which a combustion chamber filling is ignited by a spark plug, not shown, or a diesel engine, which does not need this aid as a compression igniter.

A change of fillings in the combustion chamber 4th is via an inlet valve 8th and a outlet valve 10 controlled, the inlet valve 8th from an inlet valve actuator and the outlet valve 10 is operated by an exhaust valve actuator.

With the inlet valve open 8th air or a mixture of air and fuel flows out of an intake system 12 into the combustion chamber 4th . Depending on the engine concept, the amount of air flowing in or the mixture flowing in can also be adjusted via a throttle valve, not shown, which is actuated by a throttle valve actuator. Regardless of the actuator used, the combustion chamber filling is largely determined by a boost pressure pL upstream of the inlet valve 8th influenced.

The combustion chamber filling can be determined, for example, from a signal from a filling sensor (not shown) and / or by reading from an operating model.

The fuel is either in the intake system 12 metered or directly into the combustion chamber through an injector (not shown) 4th injected. Regardless of the location of the injection, the combustion chamber 4th creates a combustible combustion chamber filling.

Residual gases from the burnt filling of the combustion chamber 4th are via the open outlet valve 10 into an exhaust system 14th pushed out. The exhaust system 14th has a feed line to and away from the exhaust gas turbocharger 2 as well as a turbocharger bypass 16 on. The implementation of the invention is of course not dependent on the exemplary charging topology described here. Rather, the charging can be single or multi-stage and can either have a VNT and bypass or just a bypass at each stage.

The turbocharger bypass 16 is by means of a bypass valve, which is in the internal combustion engine 1 a boost pressure actuator 18th trains, partially or completely closable. The boost pressure actuator 18th can for example be electrically adjustable, in particular at least essentially continuously.

The Indian 1 internal combustion engine shown 1 has an exhaust gas turbocharger 2 on, its turbine wheel 20th is driven by the exhaust gases emitted and that in turn is a compressor wheel 22nd in the intake system 12 drives.

If, for example, a large amount of exhaust gas per time at a high temperature from the combustion chamber during high-load acceleration processes 4th is pushed out, forms in the exhaust system 14th in front of the turbine wheel 20th of the exhaust gas turbocharger 2 a high exhaust back pressure pAG. However, too high an exhaust back pressure pAG is detrimental to the acceleration on the crankshaft. If by means of an exhaust back pressure sensor 28 If such an excessively high pressure is determined, the turbocharger bypass can reduce the exhaust gas back pressure pAG 16 by means of the boost pressure actuator 18th opened to the necessary extent. But that also depends on the exhaust gas turbocharger 2 generated boost pressure pL, among other things, from the position of the boost pressure actuator 18th off and is controlled by a boost pressure sensor 24 detected.

In the exemplary embodiment, the internal combustion engine 1 also an exhaust gas recirculation 13th directly from the exhaust system 14th via an EGR valve 19th into the fresh air duct 12 on, the amount of recirculated exhaust gas through the EGR valve 19th can be controlled, which in one embodiment can also be used as a further boost pressure actuator (not described below).

A driver's torque requests are made by a driver request generator 26th detected, which detects the position of an accelerator pedal of the motor vehicle as a driver's request.

The fresh air inlet into the intake system 12 is just like the exhaust by means of an exhaust aftertreatment 30th purified exhaust gases symbolized by a double-crossed vertical arrow.

Of course, they are used to control and / or regulate the internal combustion engine 1 in modern motor vehicles, various other parameters may be recorded, such as a speed of a crankshaft of the internal combustion engine, as well as pressures, temperatures, angular positions of camshafts and / or other operating parameters of the internal combustion engine. These parameters can be adjusted using suitable sensors and / or using a suitable operating model 32 of the digital twin of the internal combustion engine. The influencing variables that typically flow into a model-based boost pressure control are referred to DE 10 2006 009 864 A1 taken, in which is described as an example for a known boost pressure control, which parameters typically flow into the model-based boost pressure control.

The 2 and 3 show - using the example of the internal combustion engine 1 out 1 - each a simplified control loop of a method for boost pressure control. In addition, the 2 a corresponding known control device 50 while the 3 a control unit 100 shows according to an exemplary embodiment of the invention.

In 2 a known method is shown in which a control value limitation with different absolute values for different engine operating points only takes place after the actual model-based boost pressure control. In 3 is a method for boost pressure control according to an exemplary embodiment of the invention shown, with the differences to the known method according to 2 be clarified.

In the known method for boost pressure control according to 2 takes place first in step S 210 - in particular on the basis of a driver's request by the driver's request generator 26th - the generation of a setpoint pL, should for the boost pressure pL.

In step S 221 is by means of the boost pressure sensor 24 and / or by means of the operating model 32 an actual value pL is the boost pressure pL in the intake system 12 determined.

In step S 222 values of various modeled and / or measured influencing variables on the boost pressure pL are determined or recorded. These influencing variables can be, for example: a positive or negative traction specification by the driver, a speed of the crankshaft, an amount of fuel per stroke and combustion chamber, a throttle valve position and / or a position of the boost pressure actuator 18th .

The setpoint pL, soll flows together with that in step S 221 determined actual value pL, is of the boost pressure and the values of the influencing variables taken into account on the boost pressure in a model-based boost pressure control of step S 220 a.

In the step S 220 a manipulated variable for the boost pressure regulator is determined on the basis of these input variables for all relevant engine operating points. The conventional model-based boost pressure controls for unsteady operating situations in the high-load range (for example, strong acceleration at high speed) regularly supply manipulated variables such that their activation would result in an undesirably high exhaust gas back pressure pAG.

To counteract this, in the known method according to 2 , especially for such operating points, in step S 230 an absolute control value limitation is made, which is derived from a step S 231 provided actuator limitation map results.

The manipulated variable limit according to step S takes effect for a specific engine operating point 230 if the model-based boost pressure control according to step S 220 higher manipulated variables result than those in the actuator limitation maps.

In any case, the manipulated variables are determined by means of an in step S 240 implemented position control implemented in a suitable position of the boost pressure actuator 18th .

From the internal combustion engine 1 At least the following information flows back into the control loop: (a) an identification of the relevant engine operating point; (b) if applicable, the current values of the relevant influencing variables; (c) if applicable, the current actual value pL, is the boost pressure.

With this “overwriting” of the actual, model-based boost pressure control from step S 220 by the absolute signal box limitation from step S 230 the disadvantages stated in the general part of the description are connected.

In 3 is a control device 100 shown according to an exemplary embodiment of the invention. On this control unit 100 a method for boost pressure control can be carried out according to an exemplary embodiment of the invention.

From the known method according to 2 differs the procedure of 3 in particular due to the elimination of the absolute control value limits in accordance with step S 230 . As a result, in the exemplary embodiment, there is also no need to set the actuator limiting characteristic diagram according to step S at great expense 231 to apply.

Instead, according to step S 323 a scavenging gradient limiting map application in which a maximum permissible scavenging gradient (i.e. the maximum permissible difference between the boost pressure pL and the exhaust back pressure pAG) is recorded for all relevant engine operating points.

This map according to step S 323 On the one hand, it can be applied with much less effort and, on the other hand, it is not used to specify absolute limit values, but rather is a supplement to the model-based boost pressure control according to step S 320.

In the exemplary embodiment, for the present engine operating point in step S 324 a maximum allowable exhaust back pressure is calculated. This is obtained, for example, by determining a difference between the maximum permissible flushing gradient and the actual value pL of the boost pressure.

In this way, the model-based boost pressure control according to step S 320 a possibly necessary limitation in the calculation of the manipulated variables are already included in order to ultimately ensure that no excessively high exhaust gas back pressure is reached. The necessity of specifying absolute limit values as in the known methods according to 2 not applicable.

From the internal combustion engine 1 At least the following information flows back into the control loop: An identification of the relevant Engine operating point, for example by selecting the relevant scavenging gradient value in the scavenging gradient limitation map, which is shown in p 323 is provided, and / or a relevant value pAG of the exhaust gas back pressure sensor.

In an exemplary embodiment that is not shown, the actuator limitation map can as in FIG 2 can still be applied, but the effort could then be dramatically reduced by using the invention, in particular because the effects due to environmental conditions etc. are likewise excluded or reduced.

List of reference symbols

1

Internal combustion engine

2

Exhaust gas turbocharger

4th

Combustion chamber

6th

piston

8th

Inlet valves

10

Exhaust valves

12

Suction system

13

Exhaust gas recirculation

14th

Exhaust system

16

Turbocharger bypass

18th

Boost pressure actuator

19th

AGR valve

20th

Turbocharger turbine

22nd

Turbocharger Compressor

24

Pressure sensor

26th

Driver request generator

28

Pressure sensor

30th

Exhaust aftertreatment

32

Operating model

50

known control unit

100

Control device according to one embodiment of the invention

pL

Boost pressure

pAG

Exhaust back pressure

S210 - S240

process steps known per se

S320 - S324

Method steps according to one embodiment of the invention

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102006009864 A1 [0008, 0017, 0019, 0045]

Claims (12)

Method for regulating the boost pressure of an internal combustion engine (1) with an exhaust gas turbocharger (2), comprising the steps: Determination of a manipulated variable for a boost pressure adjuster (18) on an exhaust gas turbine side of the exhaust gas turbocharger, based on the setpoint determined for the boost pressure and as a function of an actual value (pL, ist) of the boost pressure (S221) and of at least one modeled influencing variable (S 222) by means of a model-based boost pressure control (S 320), characterized in that the model-based boost pressure control (S320) also takes place as a function of a target value for an exhaust gas back pressure (S324). Procedure according to Claim 1 , characterized in that the target value for the exhaust gas back pressure depends on an engine operating point. Method according to one of the preceding claims, characterized in that the target value for the exhaust gas back pressure relates to a maximum permissible exhaust gas back pressure. Method according to one of the preceding claims, characterized in that the setpoint value for the exhaust gas back pressure is determined on the basis of a predetermined maximum permissible scavenging gradient (S 323). Method according to one of the preceding claims, characterized in that the target value for the exhaust gas back pressure, in particular the maximum permissible scavenging gradient, is determined, in particular predetermined, as a function of an engine operating point. Method according to one of the Claims 4 or 5 , characterized in that the model-based boost pressure regulation, in particular additionally, takes place as a function of an actual value of the flushing gradient. Procedure according to Claim 6 , characterized in that the model-based boost pressure control (S320), in particular additionally, takes place as a function of a gradient of the actual value and / or the setpoint of the flushing gradient. Method according to one of the preceding claims, characterized in that the model-based boost pressure regulation takes place, in particular additionally, as a function of an EGR rate. Method according to one of the preceding claims, characterized in that a bypass valve (18) of an exhaust gas bypass (16) and / or an EGR valve (19) of an exhaust gas recirculation (13) and / or a guide vane of an exhaust gas turbine ( 20) of the exhaust gas turbocharger (2) is provided. Control device (100) for regulating the boost pressure of an internal combustion engine (1) with an exhaust gas turbocharger (2), which is set up to - determine a setpoint (pL, soll) for a boost pressure on a compressor side of the exhaust gas turbocharger, - a manipulated variable for a boost pressure actuator (18 ) on an exhaust gas turbine side of the exhaust gas turbocharger, based on the determined setpoint value for the boost pressure as well as depending on an actual value (pL, ist) of the boost pressure and at least one modeled influencing variable by means of a model-based boost pressure control (S 320), characterized in that the control unit (100) is set up to also carry out the model-based boost pressure regulation as a function of a setpoint value for an exhaust gas back pressure. Control unit (100) according to Claim 10 , characterized in that it is set up to use a method according to one of the Claims 2 to 9 perform. Internal combustion engine (1) with an exhaust gas turbocharger (2), characterized by a control device (100) according to Claim 10 or 11 .

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