Method for operating an internal combustion engine having an exhaust gas aftertreatment system with a soot particle filter

Abstract

The present invention relates to a method for operating an internal combustion engine (100) associated with an exhaust gas aftertreatment system (140) of the internal combustion engine, the exhaust gas aftertreatment system having a device (150, 151) for reducing nitrogen oxides in the exhaust gas and an oxidizing soot particle filter (160) located downstream of the device (150, 151), wherein during a first operating mode (201) a check is performed to determine whether a situation (220) exists in which the internal combustion engine (100) can be operated such that passive soot oxidation (231) occurs with the aid of the oxidizing soot particle filter (160) under predetermined boundary conditions (225), and if this situation (220) exists, a switch is made to a second operating mode (202), wherein the internal combustion engine is operated with predetermined operating parameters (230) such that passive soot oxidation (231) occurs with the aid of the oxidizing soot particle filter (150), and the device (150, 151) is operated such that the nitrogen oxides are reduced to a lower degree than in the first operating mode (201).

Description

Technical Field

[0001] The invention relates to a method for operating an internal combustion engine and an exhaust gas aftertreatment system assigned to the internal combustion engine and having a soot particle filter for the exhaust gas system of the internal combustion engine, as well as a computing unit and a computer program for implementing the method. Background Art

[0002] The exhaust gas of internal combustion engines ignited with carbon-containing fuels (such as those used in motor vehicles) generally contains, in addition to water, oxygen, and nitrogen, nitrogen oxides (NOx), and, due to incomplete combustion processes, a mixture of hydrocarbons, carbon monoxide, and soot particles, as well as motor dust. To reduce these substances contained in the exhaust gas, exhaust gas aftertreatment systems with various specific mechanisms or catalysts can be used, which generally reduce the various aforementioned substances in the exhaust gas or remove them from the exhaust gas.

[0003] In particular, due to increasingly stringent requirements regarding the permissible emission of pollutants or particles in the exhaust gas, various devices, catalytic converters, or filters are increasingly used in exhaust gas aftertreatment systems. Typically, particle filters, in particular soot particle filters, are used to reduce undesirable soot in the exhaust gas, which is produced in particular when using diesel fuel.

[0004] The so-called SCR method (Selective Catalytic Reduction) is used, in particular, to reduce nitrogen oxides or nitrogen oxides (NOx). Here, a urea-water solution (HWL) is added as a reducing agent solution to the typically oxygen-containing exhaust gas. For this purpose, a metering module or a metering valve can be used, which includes a nozzle for injecting or adding the urea-water solution into the exhaust gas flow. Upstream of the SCR catalyst, the urea-water solution reacts to form ammonia, which then combines with the nitrogen oxides in the SCR catalyst, producing water and nitrogen. This results in a significant reduction of nitrogen oxides in the exhaust gas. Summary of the Invention

[0005] According to the present invention, a method for operating an internal combustion engine having an exhaust gas aftertreatment system, as well as a computing unit and a computer program product for implementing the method are proposed. Advantageous embodiments are the subject of the following description.

[0006] The present invention relates to a method for operating an internal combustion engine and an exhaust gas aftertreatment system associated with the internal combustion engine for its exhaust system. The exhaust gas aftertreatment system comprises a first reduction device for reducing nitrogen oxides in the exhaust gas in the exhaust system and a soot particle filter for oxidation downstream of the first reduction device for reducing nitrogen oxides in the exhaust gas. The internal combustion engine can optionally be configured as a drive for a vehicle together with one or more electric machines or drives, but can also be used as a so-called range extender for vehicles that are driven solely electrically.

[0007] The first reduction device for reducing nitrogen oxides in the exhaust gas is preferably a device for implementing the aforementioned SCR method, that is, a device that can add a urea-water solution to the exhaust gas or the exhaust gas flow and has a corresponding SCR catalyst downstream. Alternatively or additionally, such a device can also be configured to bind or store nitrogen oxides, possibly without chemically converting them. This also allows nitrogen oxides in the exhaust gas to be reduced.

[0008] The oxidizing (oxidizing) soot particle filter is preferably, for example, a precious metal-coated soot particle filter, in particular such a soot particle filter for use with diesel fuel. Such an oxidizing soot particle filter allows passive soot oxidation using nitrogen dioxide, at least under appropriate boundary conditions or operating parameters of the internal combustion engine. This allows soot collected in the soot particle filter to be burned off and thus removed, which, for example, saves or reduces maintenance work and also saves or reduces premature replacement of the soot particle filter. Suitable operating parameters include, for example, an exhaust gas temperature between 270° C. and 400° C., a nitrogen dioxide content of at least 50% of the (total) nitrogen oxides in the exhaust gas, and a ratio of nitrogen oxides to dust (the sum of particles produced during incomplete combustion of hydrocarbons) or soot (e.g., the respective substances expressed as mass per time) in the exhaust gas of at least 15, preferably at least 20. The ratio of nitrogen oxides to soot allows the "quality" or effectiveness of passive soot oxidation at the respective operating point to be assessed, since a certain excess of nitrogen oxides must be present in the exhaust gas in order for passive soot oxidation to occur. The following two reactions occur, with the first reaction being significantly predominant:

[0009]

[0010] A completely effective and meaningful (because passive) reduction of soot is achieved by means of an oxidizing soot particle filter, but due to the use of the aforementioned first reduction device for reducing nitrogen oxides in the exhaust gas upstream of the oxidizing soot particle filter, this reduction can hardly be utilized anymore, since the nitrogen dioxide has at least been converted in advance and can no longer be utilized for the oxidation of the soot present in the filter.

[0011] In the proposed method, a check is now performed during the first operating mode to determine whether a situation exists in which the internal combustion engine can be operated such that, under predefined boundary conditions, passive soot oxidation occurs or is possible with the aid of the oxidizing particle filter. The first operating mode should be understood in particular to mean that the first reduction device, located upstream of the soot particle filter and intended for reducing nitrogen oxides in the exhaust gas, is operated normally, i.e., with typical efficiency. This, in turn, typically results in no or almost no further soot being passively oxidized with the aid of nitrogen dioxide at the oxidizing soot particle filter. Of course, the soot particle filter naturally continues to perform its original task of filtering soot particles from the exhaust gas. It should also be noted that sufficient nitrogen oxides can also be reduced in the first operating mode by the first reduction device for reducing nitrogen oxides in the exhaust gas.

[0012] However, under certain boundary conditions, passive soot oxidation can also take place despite the presence of an upstream first reduction device for reducing nitrogen oxides in the exhaust gas. These predetermined boundary conditions can include, for example, the ability to adjust or provide some of the previously mentioned operating parameters for the internal combustion engine, at least for a certain period of time.

[0013] If such a situation exists, a switch is made to a second operating mode in which the internal combustion engine is operated using predetermined operating parameters such that passive soot oxidation occurs by means of the oxidizing soot particle filter, and more specifically, to a greater extent than in the first operating mode. These predetermined operating conditions include at least one of the following operating parameters: an exhaust gas temperature, preferably between 270° C. and 400° C., an average temperature of the oxidizing particle filter, a proportion of nitrogen dioxide in nitrogen oxides in the exhaust gas, preferably at least 50%, a ratio of nitrogen oxides to particulate matter in the exhaust gas, preferably at least 15, in particular at least 20, and a load distribution between the internal combustion engine and at least one electric drive (if such an electric drive is present).

[0014] Furthermore, a first reduction device located upstream of the soot particle filter for reducing nitrogen oxides in the exhaust gas in the exhaust system is operated such that the nitrogen oxides are reduced to a lesser extent than in the first operating mode. This ensures that sufficient nitrogen dioxide is present at the oxidizing soot particle filter to allow passive soot oxidation. If this situation no longer exists during the second operating mode, a switch back to the first operating mode is expedient.

[0015] In this way, the particularly advantageous effect of the oxidizing soot particle filter can be utilized as optimally as possible for the passive soot oxidation in the exhaust gas, while the best possible concentration of nitrogen oxides in the exhaust gas is maintained.

[0016] The check to determine whether this situation exists is advantageously performed based on the current operating conditions of the internal combustion engine and / or exhaust gas aftertreatment system, wherein the current operating conditions preferably include at least the current particle loading of the oxidizing soot particle filter. This involves, for example, identifying or querying the current operating state of the drive train including the internal combustion engine and a fault memory, as well as the current particle or soot loading of the soot particle filter, using a model, and optionally also prioritizing the need for passive soot oxidation. For electrified drive trains, for example, the battery charge state may also be relevant.

[0017] It is also particularly preferred that the check as to whether the situation exists is carried out on the basis of the expected operating parameters of the internal combustion engine. If the internal combustion engine is part of a vehicle, the expected operating parameters can be determined based on the expected route, preferably with the help of a so-called electronic horizon and / or route history. This makes it possible to identify sections of road that are advantageous for the use of passive soot oxidation, preferably based on a real-time electronic horizon and / or route history available on board and / or externally. It is also conceivable that an algorithm identifies frequently traveled routes and actively stores them in a storage medium or uses this data to identify in advance a situation with the possibility of adjusting the operating parameters required for this or the corresponding boundary conditions. The background here is, for example, that (in the sense of boundary conditions) the operating parameters of the internal combustion engine should be maintained constant for a certain period of time, that is, no inclinations and / or curves should occur.

[0018] A particularly preferred application of the proposed method occurs when a second reduction device for reducing nitrogen oxides in the exhaust gas in the exhaust system is arranged downstream of the oxidizing soot particle filter in the exhaust system. This may be of the same type as the first reduction device arranged upstream, but other types are also conceivable. In the second operating mode, the second reduction device for reducing nitrogen oxides in the exhaust gas in the exhaust system is then operated such that the nitrogen oxides are reduced to a greater extent than in the first operating mode. In this way, nitrogen dioxide, which may still be present in excess due to the reducing action of the upstream first reduction device, can be used particularly effectively for passive soot oxidation.

[0019] It is advantageous to operate the first and second reduction mechanisms in the first and second operating modes, respectively, such that nitrogen oxides in the exhaust gas are reduced to at least substantially the same extent in both the first and second operating modes. In other words, the effect of the second reduction mechanism is increased by the extent to which the effect of the first reduction mechanism is reduced. For example, it is advantageous to reduce nitrogen oxides in the exhaust gas by at least 70%, preferably at least 90%, in the second operating mode by the second reduction mechanism. For example, the total predetermined amount of urea-water solution can be easily distributed differently between the two mechanisms having the SCR method.

[0020] As already mentioned, the proposed method can preferably be used in a vehicle having the internal combustion engine, the exhaust system, and the exhaust aftertreatment system. Such vehicles can be, for example, passenger cars, commercial vehicles, trucks, but also so-called off-road vehicles, such as agricultural machinery (e.g., combine harvesters, tractors, etc.). However, external use of the internal combustion engine, such as in a generator (generating electricity using the internal combustion engine) or in maritime applications, such as on ships, is also conceivable.

[0021] A computing unit according to the present invention, for example a control unit of a motor vehicle or generally a control and / or regulating unit, is provided, in particular in terms of programming, to carry out the method according to the present invention.

[0022] It is also advantageous to implement the method according to the present invention in the form of a computer program or computer program product having program code for carrying out all method steps, since this results in particularly low costs, especially if the implementing controller is also used for other tasks and is therefore already available. Suitable data carriers for providing the computer program are, in particular, magnetic, optical, and electronic storage media, such as hard drives, flash drives, EEPROMs, DVDs, etc. The program can also be downloaded via a computer network (Internet, intranet, etc.).

[0023] Further advantages and embodiments of the invention are apparent from the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention is schematically illustrated in the drawings by means of an exemplary embodiment and will be described below with reference to the drawings.

[0025] Figure 1 A device having an internal combustion engine is schematically shown, in which the method according to the invention can be carried out;

[0026] Figure 2 The sequence of a preferred embodiment of the method according to the invention is schematically shown. DETAILED DESCRIPTION

[0027] exist Figure 1 Schematically shows a device having an internal combustion engine 100 and an associated exhaust system 120 and an exhaust gas aftertreatment system 140 , in which the method according to the present invention can be carried out.

[0028] The exhaust gas aftertreatment system 140 exemplarily comprises a first reduction device for reducing nitrogen oxides in the exhaust gas in the exhaust system, an oxidizing or oxidizing soot particle filter 160 arranged downstream of the first reduction device, and a second reduction device arranged downstream of the soot particle filter for reducing nitrogen oxides in the exhaust gas in the exhaust system.

[0029] The first reduction mechanism comprises a dosing module 150 (here only indicated by arrows) for adding urea-water solution to the exhaust gas and an SCR catalyst 151 arranged downstream thereof. Accordingly, the second reduction mechanism comprises a dosing module 170 and an SCR catalyst 171 arranged downstream thereof.

[0030] Furthermore, a computing unit 190 is shown, by means of which, for example, exhaust gas aftertreatment system 140 and its components can be controlled. It is also conceivable to use this computing unit to control the internal combustion engine. In this regard, computing unit 190 can be, for example, an exhaust gas aftertreatment controller or an engine controller, or a combination thereof.

[0031] exist Figure 2 In the figure, it is shown schematically that, for example, Figure 1 The same sequence of a preferred embodiment of the method according to the invention can be implemented in the device shown.

[0032] Initially, the internal combustion engine and the exhaust gas aftertreatment system are operated in a first operating mode 201 with suitable or set operating parameters. A check is preferably repeated or continuously performed to determine whether a situation 220 exists in which the internal combustion engine can be operated such that, under predefined boundary conditions 225, passive soot oxidation, for example to a specific extent, occurs or is possible with the aid of the oxidizing soot particle filter. For this purpose, in particular, current operating conditions, such as the particle loading 210 of the soot particle filter and expected operating parameters 211 of the internal combustion engine are checked, which can be performed based on an expected trajectory 212.

[0033] If such a situation is determined 220, a switch is made to the second operating mode 202, in which the aforementioned boundary conditions 225 then prevail. Predefined operating parameters 230, such as the exhaust gas temperature or the average temperature of the oxidizing soot particle filter, are then adjusted (by suitable control of the internal combustion engine) so that passive soot oxidation 231 occurs or can occur with the aid of the oxidizing soot particle filter.

[0034] Furthermore, the distribution 240 of the reduction of nitrogen oxides in the exhaust gas by means of the first reduction mechanism or the second reduction mechanism is modified such that nitrogen oxides are reduced to a lesser extent by means of the first reduction mechanism and to a greater extent by means of the second reduction mechanism. For example, the ratio of the urea-water solution distributed between the two dosing modules 150 and 170 can be modified accordingly for this purpose.

[0035] During the second operating mode 202, it is preferably checked repeatedly or continuously whether the situation 220 is (still) present. If it is not (any longer) the case, the switch is back to the first operating mode 201. There, the check is then repeated.

Claims

1. A method for operating an internal combustion engine (100) and an exhaust gas aftertreatment system (140) associated with the internal combustion engine, the exhaust gas aftertreatment system being for an exhaust gas system (120) of the internal combustion engine, wherein the exhaust gas aftertreatment system (140) comprises a first reduction device for reducing nitrogen oxides in the exhaust gas in the exhaust gas system (120) and an oxidizing soot particle filter (160) downstream of the first reduction device, in, During a first operating mode (201), it is checked whether the following situation (220) exists in which the internal combustion engine (100) can be operated in such a way that, under predetermined boundary conditions (225), passive soot oxidation (231) takes place by means of the oxidizing soot particle filter (160), wherein in the first operating mode (201), the first reduction device is operated with such an efficiency that no further soot is passively oxidized by means of nitrogen dioxide at the oxidizing soot particle filter, In this case, if such a situation (220) exists, a switch is made to a second operating mode (202), in which the internal combustion engine is operated with predetermined operating parameters in such a way that passive soot oxidation (231) is carried out with the aid of the soot particle filter (160) for oxidation, and a first reduction device for reducing nitrogen oxides in the exhaust gas in the exhaust system is operated in such a way that the nitrogen oxides are reduced to a lower extent than in the first operating mode (201).

2. The method according to claim 1, wherein The exhaust aftertreatment system (140) has a second reduction mechanism for reducing nitrogen oxides in the exhaust gas in the exhaust system downstream of the oxidizing soot particle filter (160), and the second reduction mechanism for reducing nitrogen oxides in the exhaust gas in the exhaust system is operated in the second operating mode (202) so that the nitrogen oxides are reduced to a higher degree than in the first operating mode (201).

3. The method according to claim 2, wherein: In the first and second operating modes, the first reduction device and the second reduction device are each operated in such a way that nitrogen oxides in the exhaust gas are reduced to the same extent.

4. The method according to claim 2 or 3, wherein: In the second operating mode (202), nitrogen oxides in the exhaust gas are reduced by at least 70% by the second reduction mechanism.

5. The method according to claim 4, wherein In the second operating mode (202), nitrogen oxides in the exhaust gas are reduced by at least 90% by the second reduction mechanism.

6. The method according to any one of claims 1 to 3, wherein: If the situation (220) no longer exists during the second operating mode (202), a switch is made to the first operating mode (201).

7. The method according to any one of claims 1 to 3, wherein Based on the current operating conditions of the internal combustion engine and / or the exhaust gas aftertreatment system, a check is performed to determine whether the situation (220) exists.

8. The method according to claim 7, wherein: Current operating conditions of the internal combustion engine and / or the exhaust gas aftertreatment system include at least a current particle loading of the oxidizing soot particle filter ( 210 ).

9. The method according to any one of claims 1 to 3, wherein Based on expected operating parameters of the internal combustion engine, a check is performed to determine whether the situation (220) exists.

10. The method according to claim 9, wherein: If the internal combustion engine is part of a vehicle, expected operating parameters of the internal combustion engine are determined based on the expected route course (212).

11. The method according to claim 10, wherein: If the internal combustion engine is part of a vehicle, expected operating parameters of the internal combustion engine are determined based on the expected route course (212) with the aid of an electronic horizon and / or a route history.

12. The method according to any one of claims 1 to 3, wherein In the second operating mode (202), the predetermined operating parameters include at least one of the following operating parameters: exhaust gas temperature, average temperature of the soot particle filter for oxidation, the proportion of nitrogen dioxide to nitrogen oxide in the exhaust gas, the ratio of nitrogen oxide to particulate matter in the exhaust gas, and load distribution between the internal combustion engine and at least one electric drive.

13. A computing unit (190) configured to carry out all method steps of the method according to any one of claims 1 to 12.

14. A computer program product comprising a computer program which, when executed on a computer unit (190), causes the computer unit (190) to carry out all method steps of the method according to any one of claims 1 to 12.

15. A machine-readable storage medium having a computer program stored thereon, which, when executed on a computer unit (190), causes the computer unit (190) to carry out all method steps of the method according to any one of claims 1 to 12.

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