Method, control device and computer program product for operating an internal combustion engine having an exhaust-gas aftertreatment device

Abstract

The invention relates to a method for operating an internal combustion engine (1) having an exhaust-gas aftertreatment device (2) which has at least one first oxygen-storing-capable exhaust-gas catalytic converter (3) and an electronic control unit (7) with the aid of which lambda control is carried out. The invention furthermore relates to an electronic control unit (7) and a computer program product for carrying out the method. For lambda control, first direct control interventions are carried out by means of a first control unit (RE_1) on the basis of the first sensor signal (Sig1), which is representative of a first oxygen fraction in the exhaust gas mass flow (11a) directly upstream of the first exhaust-gas catalytic converter (3), and second temporary direct control interventions by means of a second control unit (RE_2) on the basis of the second sensor signal (Sig2), which is representative of a second oxygen fraction in the exhaust gas mass flow (11a) directly downstream of the first exhaust-gas catalytic converter (3). In this case, a remaining I fraction, including an adaptation fraction (AD), which remaining I fraction is determined on the basis of the second sensor signal (Sig2) by means of an I controller unit (RE_1), is fed to the first controller unit (RE_1), for permanent offset correction, wherein an adaptation of the adaptation fraction (AD) is carried out on the basis of an ongoing evaluation (Aw) of the second temporary control interventions with regard to the frequency and / or intensity and / or duration thereof.

Description

[0001] Description

[0002] Method, control device and computer program product for operating an internal combustion engine with an exhaust gas aftertreatment device

[0003] The invention relates to a method, a control device, and a computer program product for operating an internal combustion engine, in particular a gasoline internal combustion engine, with an exhaust gas aftertreatment device. The exhaust gas aftertreatment device comprises at least one first exhaust gas catalyst, in particular a three-way catalyst, arranged close to the internal combustion engine. The catalyst is to be operated under the most optimal operating conditions possible by means of a lambda control based on a sensor signal representative of a first oxygen content in the exhaust gas mass flow immediately upstream of the exhaust gas catalyst and a second sensor signal representative of a second oxygen content in the exhaust gas mass flow immediately downstream of the exhaust gas catalyst.

[0004] The increasingly strict European legislation regarding pollutant emissions from internal combustion engines, particularly combustion engines in motor vehicles, requires not only the use and increasingly comprehensive design of exhaust gas aftertreatment devices, but also the constant monitoring of the proper functioning of all device components that influence pollutant emissions.

[0005] To ensure compliance with the required limits, exhaust aftertreatment systems are therefore equipped with combinations of multiple catalytic converters and particulate filters. These include exhaust gas sensors, such as lambda sensors for determining the oxygen content in the exhaust gas, or NOx sensors, whose signals can be used to determine a lambda value in addition to the NOx and NH3 concentrations.

[0006] The values ​​provided by the various sensors are used, on the one hand, to control and regulate the internal combustion engine, particularly with regard to pollutant emissions, and to monitor pollutant emissions, but on the other hand, they are also used to monitor the functionality of the individual components of the exhaust aftertreatment system. In today's exhaust aftertreatment systems for gasoline engines, at least one exhaust catalyst, usually designed as a three-way catalyst, is used to comply with emission limits, together with a lambda sensor upstream in the exhaust stream and a lambda sensor downstream of the exhaust catalyst. The dynamic and static properties of the lambda sensor upstream of the three-way catalyst are altered, for example, by aging and poisoning. This shifts the position of the signal level corresponding to A=1 (stoichiometric fuel-oxygen ratio).Since a three-way catalyst shows optimal catalytic properties with a raw exhaust gas with A=1, the predetermined assigned signal level of the lambda sensor should actually correspond to A=1.

[0007] For this reason, the fuel-air mixture is typically cascaded to A=1. This cascade control consists of a lambda control as an inner control loop based on the signal from the lambda sensor located upstream of the catalytic converter (pre-catalytic converter signal) and an outer control loop based on the signal from the lambda sensor located immediately downstream of the catalytic converter (post-catalytic converter signal). Due to its oxygen storage capacity, the catalytic converter acts as a buffer between the two control loops.

[0008] Due to malfunctions in the system that cannot be immediately corrected by the lambda control (e.g., large, sudden malfunctions or even small deviations in the measured pre-catalyst signal), the post-catalyst signal may deviate from the target value, depending on the magnitude and / or duration of the malfunction. This occurs when the buffering effect of the catalytic converter is insufficient to counteract the induced malfunction. If, for example, a small deviation in the measured pre-catalyst signal causes the catalytic converter to be permanently "loaded" with a slight excess of oxygen or nitrogen oxides, the oxygen storage of the catalytic converter continuously fills. At some point, the catalytic converter can no longer process or store the excess oxygen. As a result, an excess of oxygen or an oxygen breakthrough is also indicated in the post-catalyst signal.

[0009] Since any measured deviation of the downstream catalytic converter signal from the target value can have a direct impact on vehicle emissions (NOx, HC, CO), especially if no additional second catalytic converter, also known as an underbody catalytic converter, is installed downstream of the primary catalytic converter, it is important to avoid these deviations as much as possible. Even with an underbody catalytic converter, deviations of the downstream catalytic converter signal from the target value must be corrected as quickly as possible to avoid exceeding the underbody catalytic converter's reserves.

[0010] The lambda sensor installed downstream of the three-way catalytic converter serves as a monitor for catalytic conversion and enables fine adjustment of the mixture by correcting the signal level associated with A=1 via the external control loop so that the lambda value most favorable for conversion can be more effectively maintained. This process is referred to as trim control.

[0011] Document FR 2 746 851 B1 discloses a corresponding lambda control system with an exhaust gas catalytic converter and an exhaust gas sensor located upstream and downstream of the exhaust gas catalytic converter. In a first control loop, the air-fuel mixture supplied to the internal combustion engine is controlled based on the signal from the upstream exhaust gas sensor. A second control loop adapts at least one parameter of the first control loop based on the signal from the downstream exhaust gas sensor.

[0012] A trim control is also presented, for example, in document DE 198 19 461 A1 for which another lambda probe is arranged downstream of the three-way catalytic converter, which is used as a monitor probe to monitor the catalytic conversion and enables fine regulation of the mixture by correcting the signal level assigned to A = 1 in such a way that the most favorable lambda value for the conversion can always be maintained.

[0013] For trim control as an external control loop based on the signal from the lambda sensor located immediately downstream of the catalytic converter, a PID controller (with proportional (P), integral (I), and differential (D) behavior) is typically used. In this controller, the P & D component is designed to react relatively slowly to short-term disturbances, and the I component, adapted to the exhaust catalyst acting as an oxygen storage device (dead-time element), is designed to react relatively slowly in order to compensate for stationary disturbances. Due to increasingly strict emissions regulations, the storage capacity and size of the installed exhaust catalysts must also increase. This means that a larger dead-time element must also be taken into account in the control loop, which means that the I component of the PID controller must be further slowed down and the defined blocking time after transient operation of the internal combustion engine must be further extended.

[0014] To prevent the I-component from "unlearning" due to unrepresentative operating conditions, which could negatively impact emissions in other operating conditions, the I-component's operating range is limited to typical operating conditions. For this reason, the I-component is generally blocked for the duration of a defined air mass integral after transient engine operation, when the vehicle is moving too dynamically and is continuously operating between overrun cut-off (injection and lambda control off) and normal operation.

[0015] This can lead to small deviations of the level of the post-catalyst signal from the setpoint not being able to be permanently corrected via the I component of the PID controller, since there is not enough time for the I component to learn the small deviation.

[0016] Previous solutions react in the situation described above with permanent control intervention according to the P / D component of the PID controller, but without a learning effect, for example in the form of an adaptation of a permanent control intervention according to an I component of the PID controller.

[0017] In order to comply with the pollutant limits based on the latest legislation, it may be necessary, in addition to a first exhaust catalytic converter located close to the internal combustion engine, at the upstream end of the exhaust aftertreatment device, to install at least one second exhaust catalytic converter (underbody catalytic converter, UbKat) closer to the downstream end of the exhaust aftertreatment device, usually on the underbody of the vehicle, in order to eliminate pollutant components that could not previously be eliminated due to malfunctions or inadequate functioning of the upstream catalytic converters in relation to the exhaust gas mass flow. For the final monitoring of the exhaust aftertreatment device, a further exhaust gas sensor can then be installed downstream of the second exhaust catalytic converter. This sensor detects a breakthrough of pollutants, in particular NOx or NH3, but also an oxygen breakthrough, and provides a corresponding signal.

[0018] The present invention is therefore based on the object of providing an improved lambda control for an internal combustion engine with an exhaust gas aftertreatment device, which in particular makes it possible to react to slight, permanent deviations of the pre-catalyst signal and to permanently avoid the resulting continuously required P / D controller interventions of the trim control.

[0019] This object is achieved by the method according to the invention, the electronic control device according to the invention and the computer program product according to the invention according to the independent patent claims.

[0020] The advantages of the invention lie in the fact that even minor, permanent deviations in the pre-catalyst signal can be detected based on the resulting control interventions based on the post-catalyst signal, and can be avoided by means of a permanent corrective intervention "learned" from this. This sustainably improves the emissions behavior of the exhaust aftertreatment device, as recurring target value deviations in the post-catalyst signal, which negatively impact emissions behavior, can be avoided.

[0021] Advantageous embodiments, developments and details of the present invention emerge from the dependent claims, the description and the drawing.

[0022] The method according to the invention serves to operate an internal combustion engine with an exhaust gas aftertreatment device, wherein the exhaust gas aftertreatment device has at least one first oxygen-storage-capable exhaust gas catalyst. Lambda control of the fuel-air mixture supplied to the internal combustion engine during operation is carried out by means of an electronic control unit assigned to the internal combustion engine, with the aim of permanently ensuring a stoichiometric fuel-air mixture, A=1.

[0023] For lambda control, a first sensor signal and a second sensor signal are used, whereby the first sensor signal is representative of a first oxygen content in the exhaust gas mass flow immediately before the first exhaust gas catalyst and is also referred to here as the pre-catalyst signal and the second sensor signal is representative of a second oxygen content in the exhaust gas mass flow immediately after the first exhaust gas catalyst and is also referred to here as the post-catalyst signal.

[0024] For lambda control, first direct control interventions are carried out by a first controller unit based on the first sensor signal, and second temporary direct control interventions are carried out by a second controller unit based on the second sensor signal. Furthermore, for permanent offset correction, a permanent I component (integral component) including an adaptation component, determined on the basis of the second sensor signal by an I controller unit (integral controller), is fed to the first controller unit. To determine or adjust the adaptation component added to the I component of the I controller unit, a continuous evaluation of the second temporary control interventions is carried out with regard to their frequency, intensity, and / or duration, and the adaptation component is determined or adjusted depending on the result of this evaluation.

[0025] During the evaluation, the aforementioned characteristics of the control interventions—frequency, intensity, and duration—can be considered individually or in any combination, for example, statistically evaluated, and, if necessary, combined to form a single result by weighting the individual results. Based on this result, the adaptation component to be added to the I component is then determined. In this way, even small, permanent deviations in the signal level of the pre-catalyst signal can be permanently corrected, and the number of control interventions based on the post-catalyst signal can be significantly reduced.

[0026] In a first embodiment of the method according to the invention, the first controller unit, which carries out direct control interventions based on the first sensor signal (pre-catalyst signal), is designed as a PID controller (proportional-integral-derivative controller), and the second controller unit, which carries out temporary direct control interventions based on the second sensor signal (post-catalyst signal), is designed as a PD controller (proportional-derivative controller). The PD controller only carries out control interventions when and for as long as an oxygen breakthrough is indicated by the post-catalyst signal, i.e., temporarily. This combination of PID controller and PD controller is characterized by a simple and proven design and stable control behavior over a wide range.In a further refinement of the aforementioned first embodiment, a second embodiment of the method according to the invention results, wherein the second controller unit, i.e. the PD controller, is combined with the I controller unit (integral controller) to form a further PID controller. In this case, the second temporary direct control interventions are carried out solely by means of the P components (proportional components) or the D components (differential components), or by means of a combination of the P components and the D components of the further PID controller. A permanent I component (integral component) of the further PID controller, including the adaptation component, which was determined by evaluating the control interventions of the aforementioned PD controller and added to the I component, is fed to the first controller unit, i.e. the first PID controller, for the permanent offset correction.

[0027] Building on one of the aforementioned embodiments, a third embodiment of the method according to the invention results. This embodiment requires that the exhaust gas aftertreatment device has a second oxygen-storage-capable exhaust gas catalyst arranged downstream of the first exhaust gas catalyst in the exhaust gas mass flow. In this case, a third sensor signal (downstream of the UbKat signal), which is representative of a third oxygen content in the exhaust gas mass flow immediately downstream of the second exhaust gas catalyst, can be used to regulate the lambda of the fuel-air mixture supplied to the internal combustion engine during operation. This measure further increases the functional reliability of the exhaust gas aftertreatment device.If, despite the improved lambda control according to the previously described embodiments of the method, oxygen supersaturation of the second exhaust gas catalyst occurs and the downstream UbKat signal indicates an oxygen breakthrough, this can be taken into account in the lambda control and the fuel-air mixture can be regulated in such a way that such oxygen breakthroughs are reduced to a minimum or permanently avoided.

[0028] The terms "first catalytic converter" and "second catalytic converter" refer to two catalytic converters arranged consecutively in the exhaust gas mass flow, between which further components of the exhaust gas aftertreatment device, such as a particulate filter, may be arranged, but no further oxygen-storage-capable component may be arranged. However, these terms are not intended to limit the total number of catalytic converters arranged in the exhaust gas aftertreatment device to two. In a common configuration, however, the first catalytic converter is a three-way catalytic converter (TWC) located close to the engine, i.e. in the immediate vicinity of the internal combustion engine, and the second catalytic converter is a so-called underbody catalytic converter (UbKat) located remote from the engine on the underbody of a motor vehicle powered by the internal combustion engine.

[0029] In a fourth embodiment of the method, in a refinement of the third embodiment described above, controlled variables generated on the basis of the third sensor signal (post-UbKat signal) are fed to the second controller unit (PD controller, possibly as part of the further PID controller) by means of a third controller unit and are thus included in the ongoing evaluation of the second temporary control interventions with regard to their frequency and / or intensity and / or duration. The third controller unit can be designed either as a simple P controller (proportional controller), as a PD controller or as a PID controller. The second control unit (PD controller, possibly as part of the further PID controller) is only supplied with the P component or the D component, or with a combination of the P component and the D component. In this way, these control interventions of the third controller unit are incorporated into the adaptation component and, together with the I component of the I control unit, are processed.the I component of the further PID controller into the permanent correction of the air-fuel mixture supplied to the internal combustion engine and thus further improves the emission behavior of the exhaust gas aftertreatment device.

[0030] In a further fifth embodiment, in addition to the third or fourth embodiment, third temporary direct control interventions are carried out by a fourth controller unit based on the third sensor signal (downstream of the UbKat signal). These control interventions occur in parallel to the first and second direct control interventions in response to an oxygen breakthrough at the second exhaust catalyst. The fourth controller unit can be designed either as a simple P controller, a PD controller, or even a PID controller. This enables a rapid response of the controlled system to temporarily occurring disturbances and minimizes the associated negative impacts on emissions behavior.

[0031] According to a further sixth embodiment, fourth direct control interventions are carried out by a fifth controller unit, parallel to the first and second, and possibly also to the third, direct control interventions, based on an oxygen loading state of the first exhaust catalyst determined using an oxygen storage model. The oxygen storage model is configured to determine the oxygen loading state of the first exhaust catalyst. The fifth controller unit can optionally be designed as a simple P controller (proportional controller), as a PD controller, or as a PID controller. This enables predictive, preventive control intervention based on the determined oxygen loading value, even before an oxygen breakthrough at the first exhaust catalyst becomes visible in the downstream signal.

[0032] In a seventh embodiment of the method according to the invention, it can be provided that the first sensor signal (pre-catalyst signal) is the signal of an exhaust gas sensor designed as a linear lambda probe, and the second sensor signal (post-catalyst signal) is the signal of an exhaust gas sensor designed as a binary lambda probe. If, according to the third embodiment, a further exhaust gas catalytic converter and a third sensor signal (post-UbKat signal) are present, the third sensor signal is a signal representing the oxygen content in the exhaust gas from an exhaust gas sensor designed as a NOx sensor. This configuration is advantageously based on the selection and arrangement of exhaust gas sensors commonly used in exhaust gas aftertreatment devices with one or two exhaust gas catalytic converters, and the signals of any exhaust gas sensors already present can be used.

[0033] In a further embodiment, both the first exhaust catalyst and the second exhaust catalyst are designed as three-way catalysts (TWC). This ensures that exhaust gas components that may have slipped through the first three-way catalyst due to malfunctions can be reliably converted in the second three-way catalyst located downstream.

[0034] The electronic control device according to the invention for operating an internal combustion engine with an exhaust gas aftertreatment device has at least one electronic storage device in which at least one computer program product with program instructions for carrying out the method is provided. Furthermore, the electronic control device has an input / output interface configured to receive and output electrical signals, as well as an electronic computing unit (processor) for executing program instructions with access to the at least one electronic storage device and the input / output interface. The program instructions, when executed by means of the electronic computing unit, cause the electronic control device to carry out the method according to the invention according to one of the previously described embodiments.

[0035] The computer program product according to the invention for operating an internal combustion engine with an exhaust gas aftertreatment device comprises program instructions for execution by the computing unit of the electronic control device described above, wherein the program instructions, when executed by the electronic computing unit, cause the electronic control device to carry out the method according to one of claims 1 to 9.

[0036] The advantages of the electronic control device according to the invention and the computer program product according to the invention, as with the method according to the invention, lie in the fact that even minor, permanent deviations in the pre-catalyst signal can be detected based on the resulting control interventions based on the post-catalyst signal and can be avoided by means of a permanently adapted corrective intervention "learned" from this. This sustainably improves the emissions behavior of the exhaust gas aftertreatment device, since recurring target value deviations of the post-catalyst signal, which negatively impact emissions behavior, can be avoided.

[0037] The features and combinations of features of the embodiments of the subject matter according to the invention mentioned above in the description or below in the description of the figures are to be used individually, in part or in whole, also in mutual combination or mutual supplementation, in further development of the subject matter according to the invention, without departing from the scope of the invention, unless they are applicable alternatively or even mutually exclusive.

[0038] Features and details that are described in connection with the method naturally also apply in connection with the electronic control device and the computer program product, and vice versa, so that with regard to the disclosure of this invention, reference can always be made to the individual aspects of the invention.

[0039] The term controller unit is to be understood as a generic term for the well-known P-controllers, I-controllers, PD-controllers or PID-controllers, whereby these controller units are not to be understood as physical components in the conventional sense, but as calculation algorithms stored in the electronic control unit by programming or functionalities implemented in the form of microelectronic circuits.

[0040] Particularly advantageous embodiments, details or developments of the invention are explained in more detail below with reference to the figures, although the subject matter of the invention is not intended to be limited to these examples.

[0041] They show:

[0042] Fig. 1 is a simplified schematic representation of an internal combustion engine with exhaust gas aftertreatment device.

[0043] Fig. 2 is a simplified block diagram showing the controller units and their interconnection to explain the method according to the invention.

[0044] Fig. 3 is a simplified block diagram like Fig. 2 but extended by further embodiments

[0045] The figures in the drawings of this application are to be viewed merely as schematic, and the proportions of the individual figures and the elements depicted in the figures are not to be considered to scale. Rather, individual elements may be exaggerated for clarity and / or clarity. Elements with the same function, designation, type, or effect are identified by the same reference numerals throughout the figures. Individual reference numerals may be omitted in individual figures to improve clarity.

[0046] Figure 1 shows an internal combustion engine 1, which can be designed, for example, as a reciprocating piston internal combustion engine with four cylinders (indicated). The internal combustion engine 1 is supplied with an air-fuel mixture 10a from the intake side via an air-fuel mixture supply unit 10. The air-fuel mixture supply unit 10 represents, for example, a fuel injection system in conjunction with a throttle valve, which is connected to the electronic control device 7 via signal lines 8 and is controlled such that an air-fuel mixture 10a in a predetermined quantity and composition is supplied to the combustion chambers of the internal combustion engine 1.Thus, the electronic control device can, in accordance with the program instructions executed therein, influence both the power provided and the composition of the exhaust gas mass flow 11a, in particular the so-called lambda value, which provides information about the oxygen content in the exhaust gas.

[0047] Connected to the exhaust side of the internal combustion engine 1 is an exhaust gas aftertreatment device 2 comprising a first exhaust gas catalyst 3, a second exhaust gas catalyst 4, and a particulate filter 5, which are connected to the internal combustion engine 1 and interconnected via an exhaust pipe 11. The exhaust gas mass flow 11a is guided through the exhaust pipe 11 to the aforementioned components of the exhaust gas aftertreatment device 2. The exhaust gas mass flow 11a is represented by arrow symbols that indicate the flow direction of the exhaust gas mass flow 11a. The first exhaust gas catalyst 3 is arranged close to the engine, directly at the exhaust outlet of the internal combustion engine 1, and is designed here, for example, as a three-way catalyst (TWC).The first exhaust gas catalyst 3 is followed downstream of the exhaust gas mass flow 10a by a particle filter 5, which is designed, for example, as a gasoline particle filter (GPF), and then by the second exhaust gas catalyst 4, which can also be designed as a three-way catalyst (TWC) and can be arranged, for example, as a so-called underbody catalyst (UbKat) on the underbody of a motor vehicle.

[0048] In the exhaust pipe 11, a first exhaust gas sensor 6a is arranged upstream of the first exhaust gas catalytic converter 3, a second exhaust gas sensor 6b is arranged downstream of the first exhaust gas catalytic converter 3, and a third exhaust gas sensor 6c is arranged downstream of the second exhaust gas catalytic converter 4. A temperature sensor 9 for measuring the temperature of the exhaust gas mass flow 11a is also arranged in the exhaust pipe 11 between the first exhaust gas catalytic converter 3 and the particulate filter 5.

[0049] The aforementioned sensors 6a-c and 9 are connected via electrical signal lines 8 to the input / output interface 7c of an electronic control device 7 according to the invention for transmitting the sensor signals to the control device 7. The air-fuel mixture supply unit 10 of the internal combustion engine 1 is also connected via electrical signal lines 8 to the input / output interface 7c of the electronic control device 7 according to the invention.

[0050] The electronic control device 7 has an electronic processing unit 7a, also referred to as a processor, an electronic storage device 7b, and an input / output interface 7c. In this embodiment, the electronic storage device 7b comprises a program memory 7b1 in which a computer program product 20 according to the invention with program instructions is available. Furthermore, the electronic storage device 7b has an operating data memory 7b2 in which predefined operating data 21 as well as operating data acquired during operation are stored, for example, organized in characteristic maps.

[0051] The electronic processing unit 7a is configured to carry out the method according to the invention in the embodiments described above and, if applicable, in addition thereto. For this purpose, the electronic processing unit 7a has access to, or is in data communication with (symbolized by connecting arrows) the input / output interface 7c, the program memory 7b1, and the operating data memory 7b2. Upon execution of the program instructions by means of the electronic processing unit 7a, using the relevant operating data 12 and various threshold values ​​for the oxygen content in the exhaust gas mass flow, the electronic control device 7 is prompted to execute the method according to the invention for operating the internal combustion engine 1, executing a lambda control of the fuel-air mixture 10a supplied to the internal combustion engine 1 during operation.

[0052] According to the program instructions, sensor data or operating data 12, for example, the signals from exhaust gas sensors 6a-c, which represent the oxygen content in exhaust gas mass flow 10a, and signals from temperature sensor 9, are received via the input / output interface 7c, and the program-specified arithmetic operations for lambda control are executed according to the method according to the invention. Based on this, control commands, for example, for controlling the air-fuel mixture 10a, are then output to the air-fuel mixture supply unit 10 of the internal combustion engine 1.

[0053] Figure 2 shows a simplified block diagram showing the controller units and their interconnection to explain the method according to the invention. The basis is the representation of the internal combustion engine 1 with air-fuel mixture supply unit 10 and exhaust gas aftertreatment device 2, however initially only with a first oxygen-storage-capable exhaust gas catalyst 3 and a particulate filter 5, as well as the exhaust gas sensors 6a and 6b, which are arranged along the exhaust pipe 11, as already explained in relation to Fig. 1. Furthermore, the controller units RE_1, RE_2 and RE_I are symbolically represented as individual units with dashed borders. The signal transmissions between the exhaust gas sensors 6a, 6b and the controller units RE_1, RE_2 and RE_I are shown with dotted lines.

[0054] For lambda control, a first sensor signal Sig1, which is provided by the first exhaust gas sensor 6a and is representative of a first oxygen content in the exhaust gas mass flow 11a immediately upstream of the first exhaust gas catalyst 3, is fed to the first control unit RE_1.

[0055] Furthermore, a second sensor signal Sig2, which is provided by the second exhaust gas sensor 6b and is representative of a second oxygen content in the exhaust gas mass flow 11a immediately after the first exhaust gas catalyst (3), is supplied in parallel to the second controller unit RE_2 and the I controller unit RE_I.

[0056] In addition, a permanent I component, including an adaptation component AD, determined by the I control unit RE_I on the basis of the second sensor signal Sig2, is supplied to the first control unit RE_1 for permanent offset correction. On this basis, a first direct control intervention, corrected by the I component of the I control unit RE_I and the adaptation component AD, is then performed on the air-fuel mixture supply unit 10 by the first control unit RE_1.

[0057] In addition, a second temporary direct control intervention on the air-fuel mixture supply unit 10 is carried out by the second controller unit RE_2, for rapid lambda correction of the air-fuel mixture 10a in the event of an oxygen breakthrough detected by the second exhaust gas sensor 6b. Furthermore, a continuous evaluation of the second temporary control interventions of the second controller unit RE_2 takes place, with the adaptation component AD added to the I component of the I controller unit RE_I being adjusted depending on the result of this evaluation. This is symbolized in Fig. 2 by an evaluation unit, Aw>>AD, which can be implemented, for example, as the evaluation algorithm Aw>>AD in the electronic processing unit 7a of the electronic control device and transmits the result of the evaluation to the I controller unit RE_I.

[0058] The evaluation of the control interventions of the second control unit RE_2 can be carried out with respect to at least one of the characteristics frequency, intensity, and duration of the control interventions, or even a combination of these characteristics. For example, both statistical evaluation methods and a weighted combination of the individual characteristics can be used.

[0059] In this way, repeatedly forced control interventions of the second control unit RE_2 are included in a permanent correction of the control interventions of the first control unit RE_1 and the frequency of oxygen breakthroughs at the first exhaust gas catalyst is significantly reduced.

[0060] The first controller unit RE_1 can be designed as a so-called PID controller, and the second controller unit RE_2 can be designed as a so-called PD controller. The second controller unit RE_2 can be combined with the I controller unit RE_I to form a further PID controller RE_2', as symbolically represented in Fig. 2 by a dashed border around the second controller unit RE_2 and the I controller unit RE_I. The I component, supplemented by the adaptation component AD, is then transmitted from the further PID controller RE_2' to the first controller unit RE_1, and the P components and / or D components are used for the second direct control interventions and their ongoing evaluation.

[0061] Fig. 3 shows the block diagram similar to Fig. 2, but expanded to include further embodiments. The exhaust aftertreatment device 2 here has a second oxygen-storage-capable exhaust catalyst 4, which is arranged downstream of the particulate filter 5 in the exhaust pipe 11. This can be designed as a three-way catalyst (TWC) and, due to its location, usually on the underbody of a motor vehicle powered by the internal combustion engine, is also referred to as an underbody catalyst (UbKat). A further exhaust gas sensor 6c is arranged directly downstream of the second exhaust catalyst 4.This exhaust gas sensor 6c can, for example, be designed as a NOx sensor which provides a third sensor signal Sig3 which is representative of the oxygen content in the exhaust gas mass flow 11a immediately downstream of the second exhaust gas catalyst 4 and which is used in addition for the lambda control of the fuel-air mixture 10a supplied to the internal combustion engine 1 during operation.

[0062] For this purpose, the third sensor signal Sig3 is fed to a third controller unit RE_3, and controlled variables or control interventions generated by the third controller unit RE_3 on the basis of the third sensor signal Sig3 are fed to the second controller unit RE_2 or the further PID controller RE_2'. In this way, the temporary control interventions of the second controller unit RE_2 are forced, and the likewise temporary control interventions of the third controller unit RE_3 are included in the ongoing evaluation of the second temporary control interventions with regard to their frequency, intensity, and / or duration, thus affecting the adaptation component AD and the permanent correction of the first control interventions. The third controller unit RE_3 can be designed as a simple P controller, a PD controller, or even a PID controller.

[0063] Also shown in Fig. 3 is a fourth controller unit RE_4, which also receives the third sensor signal Sig3. The fourth controller unit RE_4 performs third temporary direct control interventions on the air-fuel mixture supply unit 10 based on the third sensor signal Sig3. This serves to provide immediate, rapid lambda correction of the air-fuel mixture 10a in the event of an oxygen breakthrough at the second exhaust gas catalytic converter 4. The fourth controller unit RE_4 can also be designed as a simple P controller, a PD controller, or even a PID controller.

[0064] Also shown in Fig. 3 is a fifth controller unit RE_5 with which fourth direct control interventions on the air-fuel mixture supply unit 10 can be carried out. In this case, these interventions are carried out on the basis of an oxygen loading state of the first exhaust gas catalytic converter 3 determined using an oxygen storage model L-Mod. The oxygen storage model L-Mod is symbolically represented in Fig. 2 by a box labeled L-Mod that is connected to the first exhaust gas catalytic converter on the one hand and to the fifth controller unit RE_5 on the other. The oxygen storage model L-Mod can also be provided as a calculation algorithm in the electronic computing unit 7a of the electronic control device and serves to determine the oxygen loading state of the first exhaust gas catalytic converter 3, the value of which is then fed to the fifth controller unit RE_5.The fifth controller unit RE_5 can also be designed as a simple P controller, a PD controller, or even a PID controller. List of reference symbols.

[0065] 1 internal combustion engine

[0066] 2 exhaust aftertreatment device

[0067] 3 first exhaust catalyst

[0068] 4 second exhaust catalyst

[0069] 5 particle filters

[0070] 6a - c Exhaust gas sensors

[0071] 7 electronic control device

[0072] 7a Electronic computing unit

[0073] 7b Electronic storage device

[0074] 7b1 Program memory

[0075] 7b2 Operating data memory

[0076] 7c Input / output interface

[0077] 8 signal lines

[0078] 9 Temperature sensor

[0079] 10 Air-fuel mixture supply unit

[0080] 10a Air-fuel mixture

[0081] 11 Exhaust pipe

[0082] 11 a Exhaust gas mass flow

[0083] 20 Computer program product

[0084] 21 Operating data

[0085] GPF Gasoline Particulate Filter

[0086] Ap pressure difference sensor

[0087] TWC three-way catalyst

[0088] UbKat underbody catalyst

[0089] RE_1 first controller unit

[0090] RE_2 second controller unit

[0091] RE_2' additional PID controller

[0092] RE_3 third controller unit

[0093] RE_4 fourth controller unit

[0094] RE_5 fifth controller unit

[0095] Sig1 first sensor signal

[0096] Sig2 second sensor signal

[0097] Sig3 third sensor signal

[0098] L-Mod oxygen storage model

[0099] Aw»AD evaluation unit / evaluation algorithm

[0100] AD adaptation share

Claims

Patent claims 1. A method for operating an internal combustion engine (1) with an exhaust gas aftertreatment device (2), wherein the exhaust gas aftertreatment device (2) has at least one first oxygen-storage-capable exhaust gas catalyst (3), and a lambda control of the fuel-air mixture (10a) supplied to the internal combustion engine (1) during operation is carried out by means of an electronic control unit (7) assigned to the internal combustion engine (1), wherein a first sensor signal (Sig1), which is representative of a first oxygen content in the exhaust gas mass flow (11a) immediately upstream of the first exhaust gas catalyst (3), and a second sensor signal (Sig2), which is representative of a second oxygen content in the exhaust gas mass flow (11a) immediately downstream of the first exhaust gas catalyst (3), are used for the lambda control, wherein first direct control interventions are carried out by means of a first control unit (RE_1) on the basis of the first sensor signal (Sig1),and second temporary direct control interventions are carried out by means of a second controller unit (RE_2) on the basis of the second sensor signal (Sig2), and a permanent I component determined on the basis of the second sensor signal (Sig2) by means of an I controller unit (RE_I), including an adaptation component (AD), is fed to the first controller unit (RE_1) for the permanent offset correction, wherein a continuous evaluation (Aw) of the second temporary control interventions is carried out with regard to their frequency and / or intensity and / or duration, and the adaptation component (AD) assigned to the I component of the I controller unit (RE_I) is adjusted depending on the result of this evaluation (Aw).

2. The method according to claim 1, wherein the first controller unit (RE_1) is designed as a PID controller and the second controller unit (RE_2) is designed as a PD controller.

3. The method according to claim 2, wherein the second controller unit (RE_2) is combined with the I controller unit (RE_I) to form a further PID controller (RE_2') and the second temporary direct control interventions are carried out by means of the P and / or D components of the further PID controller (RE_2') and a permanent I component of the further PID controller (RE_2'), including the adaptation component (AD), is fed to the first controller unit (RE_1) for the permanent offset correction.

4. Method according to one of claims 1 to 3, wherein the exhaust gas aftertreatment device (2) has a second oxygen-storage-capable exhaust gas catalyst (4) arranged downstream of the first exhaust gas catalyst (3) in the exhaust gas mass flow (11 a), and a third sensor signal (Sig3), which is representative of a third oxygen content in the exhaust gas mass flow (11 a) immediately downstream of the second exhaust gas catalyst (4), is used for lambda control of the fuel-air mixture (10 a) supplied to the internal combustion engine (1) during operation.

5. The method according to claim 4, wherein control variables generated by a third control unit (RE_3) on the basis of the third sensor signal (Sig3) are fed to the second control unit (RE_2) and are thus included in the ongoing evaluation of the second temporary control interventions with regard to their frequency and / or intensity and / or duration.

6. The method according to claim 4 or 5, wherein third temporary direct control interventions are carried out by means of a fourth controller unit (RE_4) on the basis of the third sensor signal (Sig3).

7. The method according to one of claims 1 to 6, wherein fourth direct control interventions are carried out by means of a fifth controller unit (RE_5) on the basis of an oxygen loading state of the first exhaust gas catalyst (3), which is determined by means of an oxygen storage model (L-Mod).

8. Method according to one of the preceding claims, wherein the first sensor signal (Sig1) is the signal of an exhaust gas sensor (6a) designed as a linear lambda probe and the second sensor signal (Sig2) is the signal of an exhaust gas sensor (6b) designed as a binary lambda probe and the optionally present third sensor signal (Sig3) is a signal representing the oxygen content in the exhaust gas from an exhaust gas sensor (6c) designed as a NOx sensor.

9. Method according to one of claims 4 to 8, wherein the first exhaust gas catalyst (3) and the second exhaust gas catalyst (4) are designed as three-way catalysts (TWC1, TWC2).

10. Electronic control device (7) for operating an internal combustion engine (1) with an exhaust gas aftertreatment device (2), with at least - an electronic storage device (7b) in which at least one computer program product (20) with program instructions for carrying out the method is provided and - an input / output interface (7c) configured to receive and output electrical signals, and - an electronic processing unit (processor) (7a) for executing program instructions, with access to the at least one electronic memory device (7b) and the input / output interface (7c); wherein the program instructions, when executed by means of the electronic processing unit (7a), cause the electronic control device (7) to execute the method according to one of the preceding claims.

11. Computer program product (20) for operating an internal combustion engine (1) with an exhaust gas aftertreatment device (2), comprising program instructions for execution by the electronic computing unit (7a) of the electronic control device (7) according to claim 10, wherein the program instructions, when executed by the electronic computing unit (7a), cause the electronic control device (7) to carry out the method according to one of claims 1 to 9.

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