Method, calculation unit and computer program for operating an internal combustion engine

Abstract

The invention relates to a method (200) for operating an internal combustion engine (110), comprising: providing and burning an air-fuel mixture having a first composition; determining (210) a current composition of combustion exhaust gases generated during combustion; determining (220) an emissions set from a plurality of successively determined current compositions of the combustion exhaust gases, the emissions set comprising, for at least one component of the combustion exhaust gases, a total amount emitted within a predetermined interval; and setting (250) a second composition of the air-fuel mixture in accordance with the determined emissions set. Furthermore, the invention relates to a computing unit and a computer program product for carrying out the method.

Description

Technical Field

[0001] The invention relates to a method for operating an internal combustion engine, as well as to a computing unit and a computer program for carrying out the method. Background Art

[0002] In order to purify the exhaust gas of pollutants, catalytic converters and sensors, in particular exhaust gas sensors such as lambda probes, are generally installed in the exhaust system of vehicles with internal combustion engines. Since these components are mandatory to comply with predefined limit values, they are usually monitored through various diagnostic methods.

[0003] To keep pollutant emissions low, it is generally preferred to strive for a stoichiometric air-fuel ratio (λ=1), particularly in systems with gasoline engines. This means that exactly as much oxygen is available as is required for complete combustion of the fuel into carbon dioxide and water. Even in other engine concepts, operating strategies exist that require operation with an exhaust gas λ of 1 (e.g., particle filter regeneration, heating strategies, etc.).

[0004] For diagnostic purposes, it may be necessary to actively adjust the desired value for the combustion lambda in order to evaluate the reaction of components in the exhaust system to the lambda adjustment. This may involve, for example, dynamic or offset diagnostics of lambda sensors or, in the case of catalytic converters, diagnostics of the oxygen storage capacity. Summary of the Invention

[0005] According to the present invention, a method for operating an internal combustion engine, as well as a computing unit and a computer program for carrying out the method are proposed. Advantageous embodiments are the subject of the following description.

[0006] The method for operating an internal combustion engine according to the present invention comprises: providing and combusting an air-fuel mixture having a first composition; determining the current composition of the combustion exhaust gas produced during the combustion; determining an emissions set from a plurality of successively determined current compositions, the emissions set comprising the total amount emitted within a predetermined interval for at least one component of the combustion exhaust gas; and setting a second composition of the air-fuel mixture in accordance with the determined emissions set. This allows not only the current emission characteristics to be taken into account when controlling the internal combustion engine (as is customary in conventional methods), but also monitoring compliance with limit values, for example, over the entire operating or driving cycle, thereby enabling an overall reduction in emissions.

[0007] Advantageously, the emissions set relates to the work performed by the internal combustion engine and / or the operating time of the internal combustion engine and / or the route traveled by the vehicle driven by the internal combustion engine. These are used as a basis, for example, in legal requirements regarding maximum emissions and thus form particularly important reference variables.

[0008] The second component is set, in particular, by reducing the fuel proportion in the air-fuel mixture if a rich component predominates in the emission profile and / or by increasing the fuel proportion if a lean component predominates in the emission profile. This prevents the emission characteristics from being altered in the direction of averaging overrepresented components.

[0009] Within the scope of the present invention, rich gas components are understood to be any chemical compounds produced by the combustion of fuel in the presence of a substoichiometric amount of oxygen, i.e., in particular hydrocarbons or partially oxidized hydrocarbons (e.g., monohydric or polyhydric alcohols, aldehydes, ketones, carboxylic acids, their respective derivatives, and combinations thereof), carbon monoxide, ammonia, and hydrogen. Lean gas components are generally understood to be such compounds, in particular nitrogen oxides, formed when the fuel is combusted in the presence of a superstoichiometric amount of oxygen.

[0010] The predominance of a component is characterized in particular by the fact that the distance between the proportion of the predominant component in the emission set and the threshold value assigned to the predominant component is smaller than the distance between all proportions of the other components and the threshold values ​​assigned to the other components. This offers the advantage that, for example, different threshold values ​​can be assigned depending on the risk potential of the respective component. The aforementioned distances can be calculated, in particular, as relative distances from the respective threshold values.

[0011] The second component is preferably set based on the necessity of at least one of the multiple measures. In this way, in principle, the emission-optimal component can be selected and the change of the component can be performed only when there is a need.

[0012] These measures include, in particular, diagnosis and / or maintenance of at least one component of the internal combustion engine and / or an exhaust gas aftertreatment system connected downstream thereof. Examples of such measures include, in particular, catalytic converter diagnosis, lambda sensor diagnosis, so-called catalytic converter cleaning, regeneration of the particle filter, so-called catalytic converter heating, and the like.

[0013] In particular, these measures are carried out successively, and the method further comprises specifying the order in which these multiple measures are carried out based on the dominant component. This allows, for example, the storage capacity of the catalytic converter to be optimally utilized and overall the emission of pollutants downstream of the catalytic converter to be avoided or at least reduced.

[0014] Generally, by using sensors and models in the exhaust system it is possible to infer the emissions currently occurring. Examples of such emissions are nitrogen oxides (NO x ), ammonia (NH3), carbon monoxide (CO), hydrocarbons (HC), hydrogen (H2) and carbon dioxide (CO2) as a measure of fuel consumption.

[0015] In particular, the present invention enables early detection of (imminent) exceeding of legal exhaust gas limit values. By integrating the current emission values ​​over (particularly time) intervals and, if necessary, weighting the integral values ​​over the route traveled in the current driving cycle, the current cumulative emissions (i.e., the emission aggregate) can be compared with the respectively applicable threshold values. The information obtained about the cumulative emissions allows, in particular, the general lambda target value and, in the case of unavoidable active adjustments, the lambda value to be influenced in a targeted manner, so that the emissions of exhaust gas components with already high cumulative values ​​or emission aggregates do not increase further and all emission requirements are met in the current driving cycle.

[0016] Preferably, the target value for the lambda control is selected such that the emission of certain exhaust gas components is avoided in a targeted manner. For example, if nitrogen oxide emissions have already been high, a slightly rich target value is selected (i.e., the oxygen content in the air-fuel mixture may be lower than that required for complete combustion of the fuel); or if, for example, hydrocarbon and / or carbon monoxide (or other exhaust gas components that are increasingly formed due to a lack of oxygen during combustion or in downstream exhaust gas aftertreatment processes, such as ammonia) emissions are expected to be high compared to a threshold value, a rich target value is avoided in a targeted manner.

[0017] Furthermore, the concept provides for a targeted adaptation of the exhaust gas composition diagnostics process strategy, taking into account the cumulative emissions. For example, in markets where only symmetrical dynamic faults of the lambda sensor are to be detected, it can be determined whether the dynamic diagnosis should be performed with preliminary conditioning for rich gas and a subsequent measurement jump to lean gas, or vice versa.

[0018] Preferably, such a system includes sensors that provide information about the current exhaust gas composition. Such sensors may be, for example, lambda sensors, nitrogen oxide sensors, temperature sensors, and the like.

[0019] Preferably, a (mathematical) model is also provided that converts the measured data into the actual raw emissions at the exhaust port of the combustion engine or into the actual emissions after the catalytic converter. Such a model is described, for example, in DE 10 2016 222 418 A1.

[0020] In addition to the distance covered in the driving cycle and the lambda value of the exhaust gas, other measured or modeled variables can be used to weight the results or to increase the accuracy. Examples of such variables are, in particular, temperature, mass flow and pressure.

[0021] It should be emphasized that while the present invention is particularly advantageous for use in vehicles, where particularly stringent legal requirements regarding permissible emissions apply, this is not the only possible application. Rather, other applications are also envisioned, particularly with stationary internal combustion engines. The internal combustion engine used can, in principle, be any type of internal combustion engine, such as a gasoline engine, a diesel engine, a lean-gas engine with spark ignition (magermotor), a rotary piston engine, and the like. The present invention can also be advantageously used in conjunction with multiple internal combustion engines, particularly with coupled exhaust systems.

[0022] The computing unit according to the present invention, for example a control unit of a motor vehicle, is configured, in particular in terms of programming, to carry out the method according to the present invention.

[0023] It is also advantageous to implement the method according to the invention in the form of a computer program or computer program product having program code for executing all method steps, as this results in particularly low costs, especially when the implementing control device is also used for other tasks and is therefore already available. Suitable data carriers for providing computer programs are, in particular, magnetic, optical, and electronic storage media, such as hard drives, flash memories, EEPROMs, DVDs, and others. It is also possible to download the program via a computer network (Internet, intranet, etc.).

[0024] Further advantages and embodiments of the invention are apparent from the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention is schematically illustrated by means of embodiments in the drawings and is described below with reference to the drawings.

[0026] Figure 1 An advantageous embodiment of a device for carrying out the method according to the invention is shown in the form of a schematic block diagram, comprising an internal combustion engine.

[0027] Figure 2 The simplified illustration in the form of a flow chart shows an advantageous embodiment of the method according to the invention. DETAILED DESCRIPTION

[0028] exist Figure 1In FIG. 1 , a device having an internal combustion engine 110 , which can be used to carry out an advantageous embodiment of the method according to the invention, is schematically illustrated in the form of a block diagram and designated overall by 100 .

[0029] In addition to internal combustion engine 110 , which may be designed as a gasoline engine, a diesel engine, or a rotary piston engine, device 100 includes an injection system 120 , an exhaust gas catalytic converter 130 , and a computing unit 140 (a so-called engine control unit, ECU).

[0030] Internal combustion engine 110 includes a plurality of combustion chambers 1-6, which are supplied with fuel by injection system 120 during operation of internal combustion engine 110. The number of combustion chambers is not critical to the present invention. For example, the injection system may be a direct injection system, although the present invention is equally applicable to intake manifold injection systems. A computing unit 140 monitors and controls the operation of device 100 and receives control signals from outside device 100, for example, via an operating unit such as a pedal, switch, or the like. For example, the computing unit may be configured to, based on the received control signals, cause the injection system to meter fuel into each combustion chamber 1-6 or specific ones of these combustion chambers 1-6, set the ignition timing for the combustion chambers 1-6 of the internal combustion engine, receive signals from components of device 100, and / or determine operating parameters of internal combustion engine 110, injection system 120, and / or exhaust gas catalytic converter 130.

[0031] The injection system 120 is configured to deliver fuel to each of the combustion chambers 1-6 individually at defined times in an amount defined by the control signal and at defined times, depending on the control signal it receives from the computing unit 140. In principle, this can occur in any desired manner suitable for such defined metering. For example, a fuel pump can load one or more distributors (rails) with fuel at a defined pressure, each of which supplies multiple combustion chambers 1-6, wherein the pressure can be predetermined, controlled, or regulated. The timing and amount of the respective metering can then be controlled via the controlled individual injection valves of the combustion chambers. Another example might be an injection device assigned to only one combustion chamber, such as a conventional pump-nozzle combination or a separate injection pump for each combustion chamber. This list clearly represents only exemplary embodiments and does not guarantee completeness.

[0032] Exhaust gas catalytic converter 130 is configured to react exhaust gas components generated during operation of internal combustion engine 110 to convert harmful substances into less harmful compounds. For example, exhaust gas catalytic converter 130 can be implemented as a conventional three-way catalytic converter. In particular, when internal combustion engine 110 is configured as a diesel engine, an oxidation catalytic converter and / or an SCR catalytic converter can also be used as exhaust gas catalytic converter 130. For illustrative purposes, a three-way catalytic converter is assumed below.

[0033] In principle, exhaust gas catalytic converter 130 is particularly effective within a defined catalytic converter window, which describes the range of exhaust gas compositions. In particular, the components oxygen, rich gas components, and carbon monoxide play a significant role in this context. Therefore, during normal operation, the operation of internal combustion engine 110 is generally controlled so that it produces exhaust gas with a composition corresponding to an air number of 1. If internal combustion engine 110 is operated, for example, in so-called boost mode (Schubbetrieb), i.e., so that internal combustion engine 110 applies a deceleration torque to the downstream drive train, particularly to the clutch input shaft and / or vehicle transmission, the exhaust gas is generally devoid of rich gas components and carbon monoxide because little or no fuel is injected into combustion chambers 1-6 of internal combustion engine 110. This reduces fuel consumption and corresponding exhaust emissions in this operating phase, but this subsequently negatively impacts the conversion capacity of exhaust gas catalytic converter 130, as it then stores too much oxygen. Therefore, conventionally, after such a boost operating phase has ended, a rich air-fuel mixture can be injected into the combustion chambers 1-6 of the internal combustion engine 110 to generate rich exhaust gas. This allows the exhaust gas catalyst 130 to be returned to the catalyst window relatively quickly. This is a conventional measure for quickly resuming catalyst operation after a boost operating phase.

[0034] During operation of internal combustion engine 110, the composition of the exhaust gas generated by internal combustion engine 110 and converted by the exhaust catalytic converter is determined, particularly using exhaust gas sensors 142, 144, 146, which can be provided, for example, as broadband lambda sensors, skip lambda sensors, and / or nitrogen oxide sensors. To this end, the signals of sensors 142, 144, 146 are transmitted to and evaluated by a computing unit 140. Based on the received signals, the composition of the air-fuel mixture injected into combustion chambers 1-6 of internal combustion engine 110 is controlled. For example, a throttle valve can be set in the air path of injection system 120 or the delivery capacity of the fuel pump can be controlled accordingly. Such control of the composition of the air-fuel mixture is a conventional method for regulating the exhaust gas composition.

[0035] Within the scope of the present invention, the calculation unit also records how the current composition of the exhaust gas develops over time, or how the current composition is summed up, averaged, and / or integrated over intervals (e.g., time or by operating or route). An emissions set is determined for at least one, and preferably multiple, components of the exhaust gas. This set includes, for example, the total amount of exhaust gas components emitted during a driving cycle (e.g., the current period of a driving route). Components such as nitrogen oxides, hydrocarbons, and carbon monoxide are particularly important in this regard, as they are subject to particularly strict legal scrutiny. The emissions set is then corrected using threshold values ​​for the respective exhaust gas components. For example, the threshold values ​​can be stored in control unit 140 itself or retrieved or received from outside the device, particularly via a wireless connection. In the latter case, the currently valid limit values ​​(locally or at the time) can be taken into account.

[0036] During calibration, for example, for each monitored exhaust gas component, the distance between the total amount determined in the emission set and the maximum amount permitted according to the threshold value can be determined. Further control of internal combustion engine 110 or injection system 120 can then take these distances into account by adjusting the composition of the air-fuel mixture only in a direction that causes a change in the exhaust gas composition in such a way that components that are already close to their permitted limits are generated to a lesser extent, while components whose total amount is still far from the corresponding maximum amount can be increasingly formed.

[0037] This is particularly advantageous in connection with diagnostic or maintenance functions for individual elements 130, 142, 144, and 146. These diagnostic and maintenance functions often require a non-stoichiometric composition of the air-fuel mixture. For example, so-called catalytic converter cleaning may require rich exhaust gas, while some diagnostic functions that detect malfunctioning lambda sensors require lean exhaust gas. Thus, depending on how many emission profiles are acquired at a specific time during the operation of internal combustion engine 110, a diagnostic function requiring lean exhaust gas can be performed, for example, if the total amount of rich components in the emission profile is close to an assigned threshold value, while nitrogen oxides (a typical lean component) play a minor role in terms of quantity. This ensures that limit values ​​are adhered to throughout the entire operating period without having to abandon the required diagnostic functions. Conversely, measures requiring rich exhaust gas, as explained above, can only be performed if the lean component predominates in the emission profile.

[0038] exist Figure 2 In FIG. 1 , an advantageous embodiment of the method according to the invention is shown in the form of a simplified flow chart and is designated overall by 200. Figure 2 References in the description (especially to parts of the device) may also refer to Figure 1 The reference numerals in .

[0039] In a first step 210 of method 200, the current exhaust gas composition downstream of internal combustion engine 110 is determined. For this purpose, in particular the information about lambda sensors and / or nitrogen oxide sensors 142, 144, 146 is determined. Figure 1 The described signals can be evaluated by control device 140 .

[0040] In step 220, an emission aggregate is determined from the current composition of the exhaust gas in combination with the composition determined previously in time. To this end, the respective current composition can be integrated over time or over the route traveled, for example.

[0041] Furthermore, the respective total amounts of the exhaust gas components listed in the emission set can be corrected to one or more corresponding threshold values ​​in step 220. For example, the relative distance of the currently determined total amount of a component from its respective threshold value or its maximum permissible amount can be determined.

[0042] In step 230 , it is determined whether an adjustment of the composition of the air-fuel mixture is necessary. If this is not the case, method 200 returns to step 210 and continues recording the exhaust gas composition.

[0043] If, however, it is determined in step 230 that an adjustment of the composition of the air-fuel mixture and thus also of the exhaust gas composition is necessary in order to carry out one or more measures, the method continues with step 240 in which the sequence of the necessary measures or the mode of execution of the necessary measures is specified as a function of the emission set determined in step 220 (or in particular the determined distance of the component quantity from its corresponding threshold value).

[0044] In a next step 250, the one or more measures are executed according to the sequence or in the execution mode specified in step 240. Thereafter, the method can return to step 210.

[0045] It should be clearly emphasized here that Figure 2 The method described is an exemplary embodiment of the present invention, from which complete deviations are possible within the scope of the present invention. In particular, several steps can be performed in a different order, for example, in a reverse order. If necessary, some of these steps can also be performed in parallel or combined with one another.

[0046] It should be clearly stated again here. Figure 1The device 100 is shown only schematically and may also include other or additional components, such as one or more additional catalytic converters, sensors, particle filters, or the like. If necessary, these additional or alternative components may also be controlled within the scope of the present invention, or the signals provided by them may be used to determine the emission set (step 220) or to specify the measures to be performed or their sequence (step 250).

Claims

1. A method (200) for operating an internal combustion engine (110), comprising: providing and combusting an air-fuel mixture having a first composition, determining (210) the current composition of the combustion exhaust gases produced during combustion, determining (220) an emissions set from a plurality of successively determined current compositions of the combustion exhaust, the emissions set comprising, for at least one component of the combustion exhaust, a total amount emitted within a predetermined interval, and setting (250) a second composition of the air-fuel mixture according to the determined emissions set, wherein said setting (250) of said second component is performed based on the necessity (230) of at least one measure among a plurality of measures, The measures are performed sequentially, and the method further comprises specifying (240) an order in which the plurality of measures are performed based on the predominant component.

2. The method (200) according to claim 1, wherein: The emission set relates to the work performed by the internal combustion engine (110) and / or the operating time of the internal combustion engine (110) and / or the road section traveled by the vehicle driven by the internal combustion engine (110).

3. The method (200) according to claim 1 or 2, wherein: If a rich component predominates in the emissions set, setting (250) the second component includes decreasing a fuel fraction in the air-fuel mixture; and / or if a lean component predominates in the emissions set, setting (250) the second component includes increasing the fuel fraction.

4. The method (200) according to claim 3, wherein: The dominance of a component is characterized in that the distance of the proportion of the dominant component in the emission set from the threshold value assigned to the dominant component is smaller than the distances of all proportions of the other components from the threshold values ​​respectively assigned to the other components.

5. The method (200) according to claim 1 or 2, wherein: The measures include diagnosing and / or maintaining at least one component of the internal combustion engine and / or an exhaust gas aftertreatment system (130) connected downstream of the internal combustion engine.

6. A computing unit (140) configured to execute all method steps of the method (200) according to any one of claims 1 to 5.

7. A computer program product comprising a computer program which, when executed on a computing unit (140), causes the computing unit (140) to perform all method steps of the method according to any one of claims 1 to 5.

8. A machine-readable storage medium having a computer program stored thereon, which, when executed on a computing unit (140), causes the computing unit (140) to perform all method steps of the method according to any one of claims 1 to 5.

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