CN112983606A

CN112983606A - Method for operating an internal combustion engine having an exhaust gas aftertreatment system with a soot particle filter

Info

Publication number: CN112983606A
Application number: CN202011476628.0A
Authority: CN
Inventors: C·奥斯曼; D·斯蒂芬
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-12-16
Filing date: 2020-12-15
Publication date: 2021-06-18
Also published as: DE102019219646A1

Abstract

The invention relates to a method for operating an internal combustion engine (100) associated with an exhaust gas aftertreatment system (140) associated with the internal combustion engine, the exhaust gas aftertreatment system having means (150, 151) for reducing nitrogen oxides in the exhaust gas and a An oxidizing carbon black particle filter ( 160 ) downstream of the mechanism ( 150 , 151 ), wherein during a first operating mode ( 201 ) a situation ( 220 ) is checked, wherein the internal combustion engine ( 100 ) can be operated such that in advance Passive carbon black oxidation ( 231 ) with the aid of an oxidation particle filter ( 160 ) under the given boundary conditions ( 225 ), if this is the case ( 220 ), it is switched to two operating modes ( 202 ) in which the The internal combustion engine is operated with the predetermined operating parameters ( 230 ) such that passive carbon black oxidation ( 231 ) is carried out by means of the oxidizing carbon black particle filter ( 150 ), and the mechanisms ( 150 , 151 ) are operated such that the A mode of operation (201) reduces nitrogen oxides to a low degree.

Description

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

Technical Field

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 and having a soot particulate filter for an exhaust system of the internal combustion engine, and to a computing unit and a computer program for carrying out the method.

Background

The exhaust gas of an internal combustion engine ignited with a carbonaceous fuel, such as is used in motor vehicles, usually contains nitrogen oxides (nitrogen oxides) in addition to water, oxygen and nitrogen and, due to an incomplete combustion process, a mixture of hydrocarbons, carbon monoxide and soot particles and motor dust. In order to reduce such substances contained in the exhaust gas, exhaust aftertreatment systems with different specific means or catalysts can be used, which generally reduce or remove different mentioned substances in the exhaust gas.

Due to the increasingly stringent legislation relating to the permitted emissions of pollutants or particles in the exhaust gas, in particular, different means, catalysts or filters are increasingly used in exhaust gas aftertreatment systems. Particulate filters, in particular soot particulate filters, are typically used for reducing undesirable soot in the exhaust gas, in particular when using diesel fuel.

In particular, the so-called SCR method (Selective Catalytic Reduction) is used to reduce nitrogen oxides (NOx) or nitrogen oxides (NOx). Here, an aqueous urea solution (HWL) is added as a reducing agent solution to the exhaust gas, which typically contains oxygen. For this purpose, a metering module or metering valve can be used, which comprises an injection nozzle for injecting or adding the aqueous urea solution into the exhaust gas stream. Upstream of the SCR catalyst, the aqueous urea solution reacts to produce ammonia, which then combines with nitrogen oxides on the SCR catalyst, producing water and nitrogen therefrom. This causes significant reduction of the nitrogen oxides in the exhaust gas.

Disclosure of Invention

According to the invention, a method for operating an internal combustion engine having an exhaust gas aftertreatment system, a computing unit and a computer program for carrying out the method are proposed with the features of the independent claims. Advantageous embodiments are the subject matter of the dependent claims and the following description.

The invention relates to a method for operating an internal combustion engine and an exhaust gas aftertreatment system associated with the internal combustion engine for an exhaust gas system of the internal combustion engine. The exhaust gas aftertreatment system has a device for reducing nitrogen oxides in the exhaust gas system and a soot particulate filter for oxidation downstream of the device for reducing nitrogen oxides in the exhaust gas. The internal combustion engine can be provided here, optionally together with one or more electric machines or drives, as a drive for the vehicle, but it is also conceivable to use it as a so-called Range Extender (Range Extender) for a vehicle which is itself driven exclusively by electricity.

The means for reducing nitrogen oxides in the exhaust gas are preferably means for carrying out the SCR method mentioned at the outset, i.e. means which enable an aqueous urea solution to be added to the exhaust gas or exhaust gas stream and have a corresponding SCR catalyst downstream. Also, as an alternative or in addition, such a mechanism can be provided for binding or storing the nitrogen oxide without chemically converting it if necessary. In this way, nitrogen oxides in the exhaust gas can also be reduced.

The oxidizing soot particle filter is preferably a noble metal-coated soot particle filter, for example, such a soot particle filter, in particular such a soot particle filter for use in diesel fuel. Such soot particle filters for oxidation allow a passive soot oxidation by means of nitrogen dioxide at least for the respective boundary conditions or operating parameters of the internal combustion engine. In this way, the soot collected in the soot particle filter can be burned off and thus removed, which saves or reduces maintenance work, for example, and likewise saves or reduces an early change of the soot particle filter. Suitable operating parameters are, for example, an exhaust gas temperature of between 270 ℃ and 400 ℃, a proportion of nitrogen dioxide in the exhaust gas of (total) nitrogen oxides of at least 50%, and a proportion of nitrogen oxides in the exhaust gas to fines (sum of particles produced in the incomplete combustion of hydrocarbons) or soot (corresponding substances, for example, expressed in mass per time) of at least 15, preferably at least 20. By means of the nitrogen oxide/soot ratio, the "quality" or effectiveness of the passive soot oxidation in the respective operating point can be evaluated, since a certain excess of nitrogen oxide must be present in the exhaust gas in order to be able to perform the passive soot oxidation. The following two reactions are carried out, the first of which clearly predominates:

。

the complete and meaningful (because of the passive) reduction of soot is achieved by means of an oxidizing soot particle filter, but this reduction can hardly be used any longer due to the use of the named means for reducing nitrogen oxides in the exhaust gas upstream of the oxidizing soot particle filter, since the nitrogen dioxide is already at least largely converted beforehand and can no longer be used for the oxidation of soot present in the filter.

In the proposed method, it is now checked during the first operating mode whether there is a situation in which the internal combustion engine can be operated such that a passive soot oxidation is or can be carried out by means of the oxidation particle filter under predetermined boundary conditions. In this case, the first operating mode should be understood in particular in such a way that the means for reducing nitrogen oxides in the exhaust gas, which are located upstream of the soot particulate filter, are operated normally, i.e., with the usual efficiency, which accordingly at least generally leads to the following result: no or little passive oxidation of more soot by nitrogen dioxide takes place on the oxidation soot particle filter. It goes without saying that the actual task of filtering soot particles out of the exhaust gas naturally continues with the aid of the soot particle filter. It should also be mentioned that sufficient nitrogen oxides can also be reduced in the first operating mode by means of the described means for reducing nitrogen oxides in the exhaust gas.

However, under certain boundary conditions, passive soot oxidation can be performed despite the upstream located mechanism for reducing nitrogen oxides in the exhaust. These predefined boundary conditions can include, for example: at least for a certain period of time, some of the previously mentioned operating parameters for the internal combustion engine can be set or made available.

If this is the case, a transition is made to a second operating mode in which the internal combustion engine is operated with the specified operating parameters in such a way that passive soot oxidation takes place by means of the soot particle filter for oxidation, and more precisely in particular to a greater extent than in the first operating mode. These predefined operating conditions comprise at least one of the following operating parameters: preferably, the exhaust gas temperature lies between 270 ℃ and 400 ℃, the moderate temperature of the oxidation particle filter, the preferably at least 50% proportion of nitrogen dioxide in the exhaust gas in nitrogen oxides, the preferably at least 15, in particular at least 20, proportion of nitrogen oxides in the exhaust gas relative to fine dust, and the load distribution between the internal combustion engine and the at least one electric drive (if such an electric drive is present).

Furthermore, the means for reducing nitrogen oxides in the exhaust gas present in the exhaust gas system, which means are located upstream of the soot particle filter, are nevertheless operated in such a way that said nitrogen oxides are reduced to a lesser extent than in the first operating mode. This is achieved in that: sufficient nitrogen dioxide is present on the soot particulate filter for oxidation, which nitrogen dioxide is capable of allowing passive soot oxidation. If the situation no longer exists during the second operating mode, a switch to the first operating mode is expediently made (again).

In this way, the particularly advantageous action of the oxidation soot particle filter can be used as optimally as possible for passive soot oxidation in the exhaust gas, while the best possible further principle of nitrogen oxides in the exhaust gas is maintained.

The check as to whether the situation exists is advantageously carried out on the basis of current operating conditions of the internal combustion engine and/or the exhaust gas aftertreatment system, wherein the current operating conditions preferably comprise at least the current particle loading of the oxidation soot particulate filter. This involves, for example, the identification or query of the current operating state and fault memory of the drive train comprising the internal combustion engine and the current particle or soot loading of the soot particle filter, for example by means of a model, and optionally also the prioritization of the need for passive soot oxidation. For electrified drive trains, for example, the battery charge state can also be of interest.

It is also particularly preferred that the check as to whether the situation exists is carried out on the basis of 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, in particular, on the basis of the expected course, preferably by means of a so-called electronic horizon and/or a course history. This makes it possible to identify road sections which are advantageous for the use of passive soot oxidation, preferably on the basis of a real-time electronic horizon and/or a route history available on board and/or externally. It is also conceivable for an algorithm to recognize routes that are frequently traveled and to actively store them in a storage medium or to use these data in order to recognize in advance a situation with the possibility of adjusting the operating parameters necessary for this or the corresponding boundary conditions. In this case, the background is, for example, that the operating parameters of the internal combustion engine should be maintained constant (in the sense of a boundary condition) for a certain period of time, i.e. no tilting and/or curvature should occur.

There is a particularly preferred application of the proposed method if a further means for reducing nitrogen oxides in the exhaust gas present in the exhaust gas system is arranged in the exhaust gas system downstream of the oxidizing soot particle filter. The same type of mechanism as the one arranged upstream may be referred to here, but other types can also be considered. In the second operating mode, the additional means for reducing nitrogen oxides in the exhaust gas present in the exhaust gas system are then operated in such a way that the nitrogen oxides are reduced to a greater extent than in the first operating mode. In this way, nitrogen dioxide which is also present in excess can be used particularly effectively for carrying out passive soot oxidation, if necessary as a result of the reduction by the upstream (first) means.

It is expedient to operate the (first) means and the further means in the first and second operating modes, respectively, such that the nitrogen oxides in the exhaust gas are reduced together at least substantially to the same extent in the first and second operating modes. In other words, the action of the further means is increased by the reduced degree of action of the (first) means. For example, it is expedient if in the second operating mode the nitrogen oxides in the exhaust gas are reduced by the further means by at least 70%, preferably by at least 90%. In the case of two systems with SCR methods, it is possible, for example, to dispense correspondingly different amounts of the entire predefined urea aqueous solution.

As already mentioned, the proposed method can preferably be applied in a vehicle having the internal combustion engine, an exhaust gas system and an exhaust gas aftertreatment system. Such vehicles can be, for example, passenger cars, commercial vehicles, trucks, but also vehicles for so-called off-road use, such as agricultural machines (e.g. combine harvesters, tractors, etc.). However, use outside of the vehicle, for example in a generator (for generating electricity by means of an internal combustion engine) or in marine applications, for example in internal combustion engines on ships, is likewise conceivable.

A computing unit according to the invention, for example a control unit of a motor vehicle or in general a control and/or regulating unit, is provided, in particular in terms of program technology, for carrying out the method according to the invention.

It is also advantageous to implement the method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps, since this results in particularly low costs, in particular if the controller for fruit application is also used for other tasks and is therefore already present. Suitable data carriers for providing the computer program are, inter alia, magnetic, optical and electrical memories, such as, for example, a hard disk, a flash disk, an EEPROM, a DVD, etc. The program can also be downloaded via a computer network (internet, intranet, etc.).

Further advantages and embodiments of the invention emerge from the description and the drawing.

Drawings

The invention is schematically illustrated in the drawings by means of an embodiment and is described below with reference to the drawings. Wherein:

FIG. 1 shows a schematic illustration of a device with an internal combustion engine, in which a method according to the invention can be carried out;

fig. 2 schematically shows a flow chart of a preferred embodiment of the method according to the invention.

Detailed Description

Fig. 1 schematically shows an arrangement with an internal combustion engine 100 and associated exhaust gas system 120 and exhaust gas aftertreatment system 140, in which the method according to the invention can be implemented.

The exhaust gas aftertreatment system 140 has, for example, means 150, 151 for reducing nitrogen oxides in the exhaust gas system, an oxidizing or oxidizing soot particulate filter 160 arranged downstream of the means, and further means 170, 171 for reducing nitrogen oxides in the exhaust gas system arranged downstream of the soot particulate filter.

The means 150, 151 here comprise a dosing module 150 (only shown here by means of an arrow) for adding an aqueous urea solution to the exhaust gas and an SCR catalyst 151 arranged downstream thereof. Accordingly, the further means 170, 171 comprise a dosing module 170 and an SCR catalyst 171 arranged downstream thereof.

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

Fig. 2 schematically shows a flow diagram of a preferred embodiment of the method according to the invention, such as can be implemented in the device shown in fig. 1.

The internal combustion engine and the exhaust gas aftertreatment system are first operated in a first operating mode 201 with operating parameters that are suitable or set for them. In this case, it is preferably checked repeatedly or continuously whether there is a situation 220 in which the internal combustion engine can be operated such that, for example, a certain degree of soot oxidation or a passive soot oxidation can take place with the aid of the soot particle filter for oxidation under predefined boundary conditions 225. For this purpose, in particular the current operating conditions, such as the particle loading 210 of the soot particle filter and the expected operating parameters 211 of the internal combustion engine, are checked, which can be carried out in particular on the basis of an expected course 212.

If it is determined 220 that such a situation exists, a transition is made to the second operating mode 202, in which the mentioned boundary conditions 225 then exist. Here, predetermined operating parameters 230, such as the exhaust gas temperature or the intermediate temperature of the oxidation soot particle filter, are then set (by suitable control of the internal combustion engine) such that a passive soot oxidation 231 is or can be carried out by means of the oxidation soot particle filter.

Furthermore, the distribution 240 in terms of the reduction of the nitrogen oxides in the exhaust gas is changed by means of the

means

150, 151 or 170, 171 in such a way that the nitrogen oxides are reduced to a lesser extent by means of the

means

150, 151 than before, while the nitrogen oxides are reduced to a greater extent by means of the

means

170, 171. For this purpose, for example, the proportion of the urea aqueous solution distributed to the two

metering modules

150 and 170 can be changed accordingly.

During the second operating mode 202, it is preferably checked repeatedly or continuously whether the situation 220 exists (continues). If this is not the case (any more), a transition is again made back to the first operating mode 201. Where the check is then carried out again.

Claims

1. Method for operating an internal combustion engine (100) and an exhaust gas aftertreatment system (140) associated with said internal combustion engine for which exhaust gas aftertreatment system (120) is used, wherein said exhaust gas aftertreatment system (120) The treatment system (140) has means (150, 151) for reducing nitrogen oxides in the exhaust gas in the exhaust system (120) and char for oxidation downstream of the means (150, 151) black particle filter (160),

In this case, during the first operating mode ( 201 ), it is checked whether there is a situation ( 220 ) in which the internal combustion engine ( 100 ) can be operated in such a way that under predetermined boundary conditions ( 225 ) Passive carbon black oxidation (231) by means of the carbon black particle filter for oxidation (160),

In this case, if this is the case ( 220 ), a transition is made to a second operating mode ( 202 ), in which the internal combustion engine is operated with predetermined operating parameters ( 230 ) such that Passive carbon black oxidation ( 231 ) is carried out by means of the oxidizing carbon black particle filter ( 150 ), and thus operates the mechanism ( 150 , 151) so that the nitrogen oxides are reduced to a lower degree than in the first operating mode (201).

2. The method of claim 1, wherein the exhaust aftertreatment system (140) has an exhaust downstream of the oxidizing carbon black particle filter (160) for removing the exhaust gas in the exhaust system Further means ( 170 , 171 ) for the reduction of nitrogen oxides in the gas, and wherein in the second operating mode ( 202 ) the further means for the reduction of nitrogen oxides in the exhaust gas in the exhaust system are operated as such. The mechanisms (170, 171) of the nitric oxides are reduced to a higher degree than in the first mode of operation (201).

3. The method according to claim 2, wherein the mechanism (150, 151 ) and the further mechanism (170, 171 ) are operated in the first and second operating modes, respectively, such that at least substantially The nitrogen oxides in the exhaust gas are reduced together to the same extent.

4. The method according to claim 2 or 3, wherein nitrogen oxides in the exhaust gas are reduced by at least 70% by the further mechanism (170, 171 ) in the second operating mode (202) %, preferably at least 90%.

5. The method according to any of the preceding claims, wherein if the situation (220) no longer exists during the second mode of operation (202), switching to the first operation Mode (201).

6. The method according to any one of the preceding claims, wherein checking whether the situation (202) exists is performed on the basis of current operating conditions of the internal combustion engine and/or the exhaust gas aftertreatment system, wherein the current Operating conditions preferably include at least the current particulate loading of the oxidizing carbon black particulate filter (210).

7. The method according to any of the preceding claims, wherein checking whether the situation (202) exists is performed on the basis of expected operating parameters (211) of the internal combustion engine.

8. The method according to claim 7, wherein, if the internal combustion engine is part of a vehicle, the expected route course (212) is known on the basis, preferably by means of an electronic horizon and/or route history Run Parameters (211).

9. The method according to any one of the preceding claims, wherein the predetermined operating parameters (230) in the second operating mode (202) comprise at least one operating parameter of the following operating parameters : exhaust gas temperature, medium temperature of the oxidizing carbon black particle filter, proportion of nitrogen dioxide in the exhaust gas to nitrogen oxides, ratio of nitrogen oxides in the exhaust gas to fine dust, and the internal combustion engine and at least one Load distribution between electric drives.

10. A computing unit (190) arranged to carry out all method steps of the method according to any of the preceding claims.

11. A computer program which, when implemented on a computing unit (190), causes the computing unit (190) to perform all method steps of the method according to any one of claims 1 to 9.

12. A machine-readable storage medium having the computer program according to claim 11 stored thereon.