DE102017211131A1 - Method for monitoring an exhaust gas purification device - Google Patents

Abstract

The invention relates to a method for monitoring a second exhaust gas purification device (14) of an exhaust system (2) for an internal combustion engine (4), with which a mixture of air and fuel is burned to exhaust gas, wherein the internal combustion engine (4) in a flow direction of exhaust gas at least a first exhaust gas purification device (8, 12) of the exhaust system (2) is connected downstream of the second exhaust gas purification device (14), wherein the internal combustion engine (4) is provided in normal operation, a normal mixture of air and fuel, which is a superstoichiometric combustion air ratio , which is burned by the internal combustion engine (4) to a normal exhaust gas, the internal combustion engine (4) for monitoring the second exhaust gas purification device (14) from a first predetermined time a monitoring mixture of air and fuel is provided, which is a stoichiometric Combustion air ratio, the vo n the internal combustion engine (4) is burned to a monitoring exhaust gas, wherein fuel of the monitoring exhaust gas in the monitoring in the second exhaust gas purification device (14) burned and a reaction of the second exhaust gas purification device (14) is detected.

Description

The invention relates to a method for monitoring an exhaust gas purification device of an exhaust system and a system for monitoring an exhaust gas purification device of an exhaust system.

An exhaust gas purification system for an internal combustion engine is adapted to reduce its emission of nitrogen oxides. For this purpose, it is possible that with the exhaust gas purification system using an aqueous urea solution, a selective catalytic reduction of burned exhaust gases is performed. It is further contemplated that such an exhaust gas purification system comprises a NOx storage catalytic converter, which is designed to store nitrogen oxides (NOx) catalytically.

It is also possible that an exhaust gas purification system comprises two catalysts, which are arranged one behind the other along a flow direction of the exhaust gas. It is u. a. necessary to regularly check these catalysts for their functionality. If the second catalyst behind the exhaust valve of the internal combustion engine and another catalytic converter is to be monitored in the flow direction, hydrocarbon compounds which are introduced via a post-injection are oxidized in a diagnosis only from the first downstream catalyst. By analyzing an oxidation of the hydrocarbon compounds carried out by the first catalyst, it is possible to diagnose this first catalyst. However, it is not possible to monitor the downstream of the second catalyst arranged in the flow direction, since the hydrocarbon compound are already burned before they reach the second catalyst. In this regard, it is, for example, necessary to integrate in the exhaust gas purification system additionally a dosing device for hydrocarbon compounds, which is adapted to meter exhaust gas flowing from the first catalyst before the second catalyst to be monitored and introduce hydrocarbon compounds, wherein such additional hydrocarbon compounds for monitoring the second catalyst are oxidized by this. This usually results in a temperature rise of the second catalyst, which is evaluated and monitored in the context of the diagnosis.

A method for operating a lambda probe arrangement in an exhaust gas purification system of an internal combustion engine is disclosed in the publication DE 10 2013 201 734 A1 known. This exhaust gas purification system comprises two catalysts arranged one behind the other, between which a lambda probe is arranged.

A method for mixture control of an internal combustion engine is in the document DE 103 39 063 A1 described. Again, a lambda probe is arranged between two catalysts of an exhaust system.

The publication DE 100 41 891 A1 describes an emission control system with an internal reduction agent generation. This exhaust gas purification system comprises two catalysts arranged one behind the other, between which a sensor is arranged, which is designed to detect nitrogen oxides and ammonia.

Against this background, it was an object to monitor a catalyst in an exhaust system, which is located within the exhaust system behind another catalyst.

This object is achieved by a method and a system having the features of the independent patent claims. Embodiments of the method and the system are evident from the dependent claims and the description.

The inventive method is for monitoring a second exhaust gas purification device of an exhaust system for an internal combustion engine or an internal combustion engine, for example. A vehicle provided, with which a mixture of air and fuel is burned to exhaust gas. In the exhaust gas system, at least one first exhaust gas purification device, downstream of which the second exhaust gas purification device is connected, is connected downstream of the combustion engine in a flow direction of exhaust gas. Accordingly, exhaust gas from the internal combustion engine initially flows through the at least one first exhaust gas purification device, ie only through a first exhaust gas purification device or through a plurality of first exhaust gas purification devices, which is arranged in the exhaust gas system in the flow direction of the exhaust gas upstream of the second exhaust gas purification device. In normal operation, the internal combustion engine is provided with a normal mixture of air and fuel, which has a lean of stoichiometric combustion air ratio and is burned by the internal combustion engine into a superstoichiometric normal exhaust gas. To monitor the second emission control device, the internal combustion engine is provided with a monitoring mixture of air and fuel from a first point in time which has a substoichiometric combustion air ratio that is burned by the internal combustion engine into a substoichiometric monitoring exhaust gas. The monitoring exhaust gas, usually located therein excess, unburned fuel is burned in the monitoring in the second exhaust gas purification device, for example. Afterburning and a Reaction of the second exhaust gas purification device detected.

In the monitoring, to detect the reaction of the second exhaust gas purifier, a temperature of purified exhaust gas exiting the second exhaust gas purifier is detected and measured, and this exhaust gas is exhausted by the second exhaust gas purifier arises.

In addition, the internal combustion engine is provided with the normal mixture again from a second point in time as soon as the monitoring exhaust gas flows through the at least one first exhaust gas purification device and has reached the second exhaust gas purification device. Thus, it is possible to operate the engine again in normal operation. The monitoring exhaust gas fuel contained in the second exhaust gas purifier is burned therefrom to perform the monitoring, which is possible even after the second time point. In this case, an adjustable amount of substoichiometric monitoring exhaust gas is provided to the second exhaust gas purification device, which is set by selecting a time period between the first and second time. In an embodiment, it is possible that the internal combustion engine from the second time an amount of modified normal mixture is provided which has a greater proportion of air and thus oxygen than the usual normal mixture and thus is even leaner than this. Consequently, a modified normal exhaust gas, which arises during the combustion of the modified normal mixture, also has a higher proportion of air than the normal exhaust gas. This excess oxygen is burned as part of the monitoring in the second exhaust gas purification device with stored therein monitoring exhaust gas fuel.

In an embodiment, the combustion air ratio of the exhaust gas is detected and measured in the flow direction upstream of the second exhaust gas purification device and behind the at least one first exhaust gas purification device. In this case, the second time occurs as soon as the monitoring mixture with the substoichiometric combustion air ratio is detected in the exhaust system at a position behind the at least one first exhaust gas purification device and before the second exhaust gas purification device. At this position, a sensor is arranged in an embodiment. Alternatively or additionally, it is possible that the second time is determined by a model. With the model, for example, a speed of the exhaust gas is taken into account, the u. a. is dependent on a speed and / or power as operating parameters of the internal combustion engine.

With the method, a second exhaust gas purification device is monitored, which is designed as a catalyst and / or as a particle filter. The at least one first exhaust gas purification device is designed as a catalyst and / or particle filter. Accordingly, it is possible that an exhaust purification device is formed as a combination of a catalyst and a particulate filter.

In general, the monitoring exhaust gas, i. H. Fuel of the monitoring exhaust gas, from the second exhaust gas purification device from the second time, at the earliest from a third time with air burned, for example. Afterburned as soon as the normal exhaust gas is detected before the second exhaust gas purification device.

Accordingly, the exhaust system comprises a plurality of successively arranged exhaust gas purification devices, which are usually connected to each other by exhaust ducts or exhaust pipes. At least one of the exhaust gas purification devices is designed as a catalyst or as a particle filter. However, it is also possible that at least one such exhaust gas purification device of the exhaust system acts on exhaust both as a catalyst and as a particle filter. With the internal combustion engine, behind which the at least one first exhaust gas purification device of the exhaust system is arranged, the mixture of air and fuel is burned to exhaust gas. In this case, the fuel is usually formed as a hydrocarbon compound (HC). Furthermore, the air contains oxygen, with which the fuel is burned. During operation of the internal combustion engine, exhaust gas flows in the intended flow direction first through the at least one first exhaust gas purification device and then through the second exhaust gas purification device.

During normal operation of the internal combustion engine, the mixture of air and fuel is provided with the normal mixture having the superstoichiometric combustion air ratio.

The combustion air ratio is also referred to as lambda value. The lambda value λ = m _tat / m _st corresponds to the ratio of the actual air mass m _{tat of} a currently combustible mixture of air and fuel divided by the stoichiometric air mass m _st required for complete combustion of the mixture of air and fuel. If the combustion air ratio and thus the lambda value is equal to 1, the mixture has a stoichiometric combustion air ratio at which all molecules of the fuel fully react with the oxygen from the air, whereby the fuel is completely burned. If the combustion air ratio, as in the normal mixture, is more than stoichiometric, the lambda value is greater than 1, which is why Normal mixture has an excess of air and is also referred to as a lean mixture. For monitoring or for the diagnosis of the second exhaust gas purification device, the combustion mixture is provided for combustion, the substoichiometric, wherein the lambda value is less than 1 and has a lack of air, wherein such a mixture is referred to as rich.

Exhaust gas from the internal combustion engine flows sequentially through the exhaust gas purification devices of the exhaust system, wherein the exhaust gas is purified successively according to a respective embodiment of a respective exhaust gas purification device. In the exhaust gas purification devices arranged one behind the other, it is possible to successively clean the exhaust gas produced in the internal combustion engine in succession. In this case, exhaust gas flowing directly from the internal combustion engine to the at least one first exhaust gas purification device is unpurified, but is purified by the at least one first exhaust gas purification device in at least a first step, which is why the exhaust gas flowing from the at least one first exhaust gas purification device to the second exhaust gas purification device , has already been partially cleaned by this. This already partially purified exhaust gas is further purified by the second exhaust gas purification device in a further step. In this case, nitrogen oxides and / or particles, for example soot and / or dust, are removed from the exhaust gas by a respective exhaust gas purification device. As a rule, different measures for purifying exhaust gas are carried out by the exhaust gas purifications, with exhaust gas being purified by catalysis and / or filtering.

It is necessary to regularly monitor and diagnose the exhaust gas purification facilities in terms of their functionality. The monitoring of the at least one first exhaust gas purification device is regularly feasible in design, since this is supplied directly from the engine unpurified exhaust gas, which is burned in the context of a diagnosis of the at least one first exhaust gas purification device.

However, since exhaust gas from the at least one first exhaust gas purification device flowing to the second exhaust gas purification device is already at least partially cleaned, its monitoring is more difficult than the monitoring of the at least one first exhaust gas purification device. Therefore, as part of the method for carrying out the monitoring of the second exhaust gas purification device, the monitoring mixture with the substoichiometric combustion air ratio is provided to the internal combustion engine, whereby the resulting monitoring exhaust gas is not completely purified by the at least one first exhaust gas purification device, and accordingly a higher proportion of fuel than the usual normal exhaust gas has. On the basis of this, excess exhaust gas burns this monitoring exhaust gas, which has already passed through the at least one first exhaust gas purification device, for carrying out the monitoring of the second exhaust gas purification device, the reaction of the second exhaust gas purification device being checked. For this purpose, it is possible in an embodiment to directly monitor the second exhaust gas purification device with a sensor provided for this purpose and, for example, to measure its temperature as an operating parameter. Alternatively or additionally, it is also possible to detect at least one parameter, for example the temperature, of purified outlet gas which flows out of the second exhaust gas purification device as part of the monitoring carried out.

The system according to the invention is designed to monitor a second exhaust gas purification device of an exhaust system for an internal combustion engine with which a mixture of air and fuel is burnt to form exhaust gas. In the exhaust gas system, at least one first exhaust gas purification device of the exhaust gas system, which is connected downstream of the second exhaust gas purification device, is connected downstream of the combustion engine in a flow direction of exhaust gas. In normal operation, the internal combustion engine is provided with a normal mixture of air and fuel, which has a lean of lean air ratio, which is burned by the internal combustion engine to a superstoichiometric or lean normal exhaust gas. The system includes a controller and at least one first sensor. The control unit is configured to adjust the combustion air ratio of the mixture to be combusted and to provide the internal combustion engine for monitoring the second exhaust gas purification device from a first time a monitoring mixture of air and fuel having a stoichiometric or rich combustion air ratio, the combustion engine of the fat monitoring exhaust gas is burned. The monitoring exhaust gas is burned during the monitoring in the second exhaust gas purification device, for example afterburning, wherein the at least one first sensor is configured to detect a reaction of the second exhaust gas purification device.

The at least one first sensor is arranged downstream of the second exhaust gas purification device in the flow direction and is designed to detect at least one parameter of exhaust gas, ie of completely purified exhaust gas, which flows out of the second exhaust gas purification device. It is alternatively or additionally also possible for the at least one first sensor to be assigned to the second exhaust gas purification device and configured to detect at least one parameter which is designed as an operating parameter, for example temperature, of the second exhaust gas purification device and during combustion of the fuel of the Monitoring exhaust gas results or sets. The at least one first sensor is formed, for example, as a thermometer or temperature sensor.

In one embodiment, the system has at least one second sensor, which is arranged in the flow direction behind the at least one first exhaust gas purification device and upstream of the second exhaust gas purification device and configured to detect at least one parameter of exhaust gas upstream of the second exhaust gas purification device. This at least one second sensor is designed, for example, as a lambda probe, with which the combustion air ratio of exhaust gas is detected, which flows from the at least one first exhaust gas purification device to the second exhaust gas purification device. Thus u. a. check whether exhaust gas flowing to the second exhaust gas purification device is formed as lean normal exhaust gas or rich monitoring exhaust gas.

Furthermore, the system comprises a storage system, which is associated with the second exhaust gas purification device, usually arranged therein, and is adapted to store excess fuel of the same monitoring exhaust gas in the second exhaust gas purification device until it is completely burned in the context of the monitoring thereof is, in which case air from the subsequent normal exhaust gas is used.

With the presented method as well as with the presented system it is possible to carry out an alternative onboard diagnosis (OBD) for the second exhaust gas purification device. For this purpose, the monitoring exhaust gas with the rich combustion air ratio is provided for carrying out the monitoring or diagnosis of the second exhaust gas purification device, which is burned by this and thus oxidized. Thus, to carry out the monitoring of the proportions, a fuel in the mixture of air and fuel is increased compared to the normal mixture and thus a fat jump is generated for the exhaust gas, by which the monitoring mixture and furthermore the monitoring exhaust gas is provided.

When carrying out the method, it is no longer necessary, for monitoring the second exhaust gas purification device, to connect it to a metering device with which additional fuel is additionally supplied to the second exhaust gas purification device solely for the purpose of monitoring it.

In a refinement, the second exhaust gas purification device is designed as a catalyst, for example as a blocking catalytic converter, with a catalytically active oxidation zone. By generating the monitoring mixture and thus the monitoring exhaust gas of the second exhaust gas purification device is additionally transported unburned hydrocarbon compared to the normal exhaust gas and thus generates a specially tuned and / or metered fat pulse or fat jump for exhaust gas.

In normal operation, the internal combustion engine is provided with the superstoichiometric lean normal mixture, whereas the monitoring engine is provided with the substoichiometric combustion air ratio to the internal combustion engine for carrying out the monitoring, the internal combustion engine being regulated accordingly. If the internal combustion engine is designed, for example, to burn diesel fuel, the additional fuel is to be provided, for example, via a post-injection. The monitoring exhaust gas resulting from the combustion has a much higher proportion of unburned fuel and carbon monoxide in relation to the normal exhaust gas.

Generation of the monitoring mixture and thus of the monitoring exhaust gas as part of the monitoring is terminated only when the monitoring exhaust gas has flowed through the at least one first monitoring device, which is arranged within the exhaust system before the second exhaust gas purification device. Since the monitoring exhaust gas contains only a small proportion of air and thus of oxygen, the additional fuel in the monitoring exhaust gas does not react to the at least one first exhaust gas purification device before the second exhaust gas purification device during the rich pulse and is incompletely combusted. Thus, it is possible for this unburned fuel to flow through the at least one first exhaust gas purification device to the second exhaust gas purification device to be monitored.

As soon as a sufficient quantity of monitoring exhaust gas has flowed through the at least one first exhaust gas purification device and has reached the second exhaust gas purification device, the normal mixture with a superstoichiometric combustion air ratio is again generated and provided for the internal combustion engine, which provides an excess compared to the monitoring mixture Having oxygen. During the monitoring, unburned fuel of the monitoring exhaust gas is stored and burned in the second exhaust gas purification device to be monitored, wherein this excess fuel is exothermic. As a result, a temperature of the second exhaust gas purification device and of the purified exhaust gas from the second exhaust gas purification device is increased, wherein an increase in the temperature is detected and evaluated as a parameter. If the increase in temperature is less than an applied limit value, it is determined in the course of the diagnosis that a function of the second exhaust gas purification device is impaired. In this case, a driver of a vehicle, which has the internal combustion engine and the exhaust system, acoustically and / or optically via a display, eg. A fault lamp informed. If, in the course of the monitoring, it turns out that the increase in the temperature of the second exhaust-gas purification device and / or the outlet gas is greater than the applied limit value, it is determined that the function of the second exhaust-gas purification device is in order.

By using the second sensor as a component of the system, which is usually designed as a lambda probe and disposed in front of the second exhaust gas purification device to be monitored, it is determined whether either the superstoichiometric normal exhaust gas or the substoichiometric monitoring exhaust gas flows to the second exhaust gas purification device. In this case, it is possible to determine with the second sensor when a quantity of monitoring exhaust gas intended and / or required for monitoring and thus of excess fuel has reached the second exhaust gas purification device. As soon as the amount provided for this is sufficient, a signal is provided by the second sensor, which usually informs the control unit to switch the internal combustion engine back to normal operation and to provide it with the superstoichiometric normal mixture. It is also possible to describe a quantity of monitoring exhaust gas via the model by which, depending on at least one operating parameter of the internal combustion engine, for example its rotational speed, a length of the time span between the first and the second time is set. With the first sensor, usually the thermometer, arranged downstream of the second exhaust gas purification device, the increase in temperature due to the exothermic reaction is determined by combustion of the fuel of the monitoring exhaust gas by the second exhaust gas purification device. In this case, a signal is usually provided by the first sensor, which is evaluated by the control unit.

In an embodiment, the second exhaust gas purification device, usually a catalyst, is equipped with a coating which is designed to store unburned fuel, for example unburned hydrocarbon compounds of the rich monitoring exhaust gas in the second exhaust gas purification device until sufficient air or Oxygen has flowed, which is located in the superstoichiometric normal exhaust gas. Such a coating of the second exhaust gas purification device is, for example, designed as a zeolite and thus as an aluminum silicate.

In one embodiment of the method, it is conceivable to provide the internal combustion engine, after it has been provided with the rich monitoring mixture for carrying out the monitoring of the second exhaust gas purification device, a modified normal mixture which has a higher lambda value and thus a higher combustion air ratio than the otherwise usual one Normal mixture. Thus, the second exhaust gas purification device is provided for a short time a larger amount of oxygen than usual, with which the additional excess fuel of the monitoring exhaust gas is also burned to carry out the monitoring of the second exhaust gas purification device, previously provided with the monitoring exhaust gas and stored therein is.

The exhaust system or a corresponding exhaust aftertreatment system comprises at least two successively arranged exhaust gas purification devices, d. H. the at least one first exhaust gas purification device arranged behind the internal combustion engine in the flow direction and the second exhaust gas purification device arranged behind it, whose function is monitored in the context of the method. It is possible that one of the two exhaust gas purification devices is designed to carry out a selective catalytic reduction using an aqueous urea solution for exhaust gas to be cleaned, with the nitrogen oxides are removed from the exhaust gas. A second exhaust gas purification device is designed to store nitrogen oxides (NOx) catalytically, such an exhaust gas purification device being designed and / or designated as a NOx storage catalyst. Thus, it is possible that two technologies are combined in the exhaust system and therefore a combined system for purifying exhaust gas is realized.

As a rule, the internal combustion engine is designed to drive or to move a vehicle, for example a motor vehicle. Accordingly, the internal combustion engine and the exhaust system are formed as components of the vehicle. Increased demands are placed on the exhaust gas purification devices of the exhaust system, whereby it is taken into account that in the case of a legally prescribed on-board diagnosis or monitoring of the emission-reducing exhaust gas purification devices, it is checked whether their functions deteriorate For example, caused due to aging of the exhaust gas purification devices. If, in the context of the method, it is determined that the function of the second exhaust-gas purification device is deteriorating so that statutory limits for a composition of the exit gas are no longer met, a corresponding visual and / or acoustic signal is provided to the driver of the vehicle. informing him of this fact and instructing him to take the vehicle to a workshop for inspection and / or repair.

In an embodiment, it is possible that the second exhaust gas purification device is designed as a catalyst and has an oxygen storage for storing oxygen. If an amount of oxygen that can be stored in the second exhaust gas purification device falls below a limit provided for this purpose, its function is impaired and inform the driver about it. The amount of storable oxygen in the second exhaust gas purification device is to be determined as part of the monitoring based on a capability of oxidation of fuel by the second exhaust gas purification device. For this purpose, it is provided that the at least one sensor, for example, is designed as a lambda probe and monitors a profile of a lambda value, which is further evaluated within the scope of the monitoring. The second exhaust gas purification device is embodied as a catalyst for the oxidation of fuel. In this case, an exothermic reaction of air and fuel is analyzed by the second exhaust gas purification device for monitoring, wherein in the context of monitoring by oxidation of unburned fuel from the monitoring exhaust gas from the second exhaust gas purification device a post-oxidation is performed. This additional unburned fuel, which is supplied to perform the monitoring of the second exhaust gas purification device with the monitoring exhaust gas is supplied in the internal combustion engine, for example. Via a post-injection to provide the monitoring mixture, said additional unburned fuel continues via the monitoring exhaust gas Exhaust system is supplied. This additional unburned fuel of the rich monitoring exhaust gas is oxidized to water and carbon dioxide by the second exhaust gas purifier by burning it with oxygen from the air. In this case, the temperature of the second exhaust gas purification device and / or the purified outlet gas increases, wherein a resulting increase in the temperature is evaluated in the context of the monitoring. If the increase in the temperature is greater than an applied limit value intended for this purpose, the function of the second exhaust gas purification device is in order. However, if the increase in temperature is less than the applied limit value, the function of the second exhaust gas purification device is impaired, whereby the driver of the vehicle is informed about the visual and / or acoustic signal.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

• 1 zeigt in schematischer Schnittdarstellung eine erste Ausführungsform einer Abgasanlage bei Durchführung einer ersten Ausführungsform des erfindungsgemäßen Verfahrens.
• 2 zeigt in schematischer Schnittdarstellung eine zweite Ausführungsform einer Abgasanlage bei Durchführung einer zweiten Ausführungsform des erfindungsgemäßen Verfahrens.
• 3 zeigt in schematischer Schnittdarstellung eine dritte Ausführungsform einer Abgasanlage bei Durchführung einer dritten Ausführungsform des erfindungsgemäßen Verfahrens.

The invention is schematically illustrated by means of embodiments in the drawings and will be described schematically and in detail with reference to the drawings.

• 1 shows a schematic sectional view of a first embodiment of an exhaust system when carrying out a first embodiment of the method according to the invention.
• 2 shows a schematic sectional view of a second embodiment of an exhaust system when carrying out a second embodiment of the method according to the invention.
• 3 shows a schematic sectional view of a third embodiment of an exhaust system when carrying out a third embodiment of the method according to the invention.

The figures are described coherently and comprehensively, the same components are assigned the same reference numerals.

The following 1 . 2 . 3 each show an example of an internal combustion engine 4 . 30 . 50 for a vehicle, each one embodiment 2 . 32 . 52 an exhaust system of this vehicle is connected downstream. To operate the internal combustion engine 4 . 30 . 50 This is a mixture of air containing oxygen, and fuel, usually a hydrocarbon compound provided. This mixture is from the internal combustion engine 4 . 30 . 50 burned, being by the internal combustion engine 4 . 30 . 50 an exhaust gas is generated. This exhaust gas flows in a flow direction starting from the internal combustion engine 4 . 30 . 50 individual components of the exhaust system described in more detail below 2 . 32 . 52 , This includes each exhaust system 2 . 32 . 52 including several emission control devices 8th . 12 . 14 . 36 . 38 . 40 . 56 . 58 . 64 , where exhaust gas from the internal combustion engine 4 . 30 . 50 these emission control devices 8th . 12 . 14 . 36 . 38 . 40 . 56 . 58 . 64 flows through successively, the exhaust gas from said exhaust gas purification devices 8th . 12 . 14 . 36 . 38 . 40 . 56 . 58 . 64 by catalysis and / or filtering successively is cleaned. After each exhaust one last exhaust purification device 14 . 40 . 64 has reached, in which it is finally cleaned, exits from this last exhaust gas purification device 14 . 40 . 64 purified exit gas.

1 shows a schematic representation of the first embodiment of the exhaust system 2 here a combustion engine 4 downstream, which is designed here for driving a vehicle. This exhaust system 2 includes a sequential turbocharger 6 and a primary primary exhaust purification device 8th , which is designed here as a combination of a nitrogen oxide storage catalyst and diesel oxidation catalyst (NSC / DOC). Behind this primary first emission control device 8th is a metering device 10 downstream, which is designed here, the exhaust system 2 to provide a urea solution (AdBlue). Behind it is inside the exhaust system 2 a secondary first exhaust gas purification device 12 arranged as a combination of a catalyst for performing a selective catalytic reduction (SCR) and a diesel particulate filter (DPF) is formed. Behind this secondary first exhaust gas purification device 12 is in the flow direction of the exhaust gas, a second exhaust gas purification device 14 arranged as a combination of a catalyst for performing the selective catalytic reduction and a catalyst for diesel oxidation. Furthermore, it is provided that this first exhaust system 2 two sensors 16 . 18 which are also formed as components of a first embodiment of a system according to the invention, with which the first embodiment of the method according to the invention is feasible. Here is the first sensor 16 in the flow direction behind the second exhaust gas purification device 14 arranged and formed as a thermometer or temperature probe. The second sensor 18 is inside the exhaust system 2 behind the secondary first exhaust purification device 12 and before the second exhaust purification device 14 arranged. These two sensors 16 . 18 are just like a control unit 20 formed as components of the system according to the invention, wherein this control device 20 is further adapted to control the first embodiment of the method according to the invention.

2 shows another example of an internal combustion engine 30 for driving a vehicle to which the second embodiment of the exhaust system 32 is downstream. This second exhaust system 2 also includes a turbocharger as components 34 and a first exhaust gas purification device 36 , which is designed here as a combination of a nitrogen oxide storage catalyst and diesel oxidation catalyst. Behind this first exhaust gas purification device 36 is in the flow direction of the exhaust gas as a second exhaust gas purification device 38 a catalytic soot filter arranged. Furthermore, this exhaust system includes 32 a dosing device 42 with which the exhaust system 32 Urea is supplied. This dosing device 42 is still a third emission control device 40 downstream, which is designed as a catalyst for carrying out a selective catalytic reduction. A second embodiment of the system according to the invention comprises a control unit 44 for controlling the second embodiment of the method according to the invention as well as a first sensor 46 and a second sensor 48 , Here is the first sensor 46 as a thermometer in the flow direction behind the second exhaust gas purification device 38 arranged. The second sensor 48 is designed here as a lambda probe and in the flow direction behind the first exhaust gas purification device 36 and before the second exhaust purification device 38 arranged.

3 shows a third example of an internal combustion engine 50 a vehicle, the second embodiment of the exhaust system 52 is downstream. This second exhaust system 52 includes a turbocharger 54 that is inside the exhaust system 52 behind the combustion engine 50 is arranged, a primary primary exhaust gas purification device 56 , which is formed here as a combination of a nitrogen oxide storage catalyst and a diesel oxidation catalyst, a secondary first exhaust gas purification device 58 , which is configured here as a catalyst for filtering soot, and a second exhaust gas purification device 60 , which is designed here as a diesel oxidation catalyst. Within this third embodiment of the exhaust system 52 is in the flow direction of the exhaust gas behind the second exhaust gas purification device 60 a dosing device 62 downstream, which is designed to the exhaust system 52 to provide a urea solution. Behind this metering device 62 is a third exhaust gas purification device 64 arranged to perform a selective catalytic reduction. 3 also shows components of a third embodiment of the system according to the invention for carrying out the third embodiment of the method according to the invention. This system includes a controller 66 for controlling the third embodiment of the method according to the invention as well as a first sensor 68 and a second sensor 70 , where the first sensor 68 in the flow direction behind the second exhaust gas purification device 60 arranged and designed as a thermometer. The second sensor 70 is inside the exhaust system 52 behind the secondary first exhaust purification device 58 and before the second exhaust purification device 70 arranged.

All embodiments of the method according to the invention for monitoring the second exhaust gas purification device 14 . 38 . 60 a respective exhaust system 2 . 32 . 52 for one internal combustion engine 4 . 30 . 50 have in common that with the internal combustion engine 4 . 30 . 50 a mixture of air and fuel is burned to exhaust gas. In normal operation, the internal combustion engine 4 . 30 . 50 provided a normal mixture of air and fuel, which has a superstoichiometric combustion air ratio with an excess of air and of the internal combustion engine 4 . 30 . 50 is burnt to a normal exhaust gas. For monitoring the second emission control device 14 . 38 . 60 becomes the internal combustion engine 4 . 30 . 50 from a first point in time, a monitoring mixture of air and fuel is provided which has a substoichiometric combustion air ratio with an excess of fuel from that of the internal combustion engine 4 . 30 . 50 is burned to a monitoring exhaust gas. Fuel of the monitoring exhaust gas is from the at least one first exhaust gas purification device 8th . 12 . 36 . 56 . 58 incomplete, but in the monitoring in the second flue gas cleaning device 14 . 38 . 60 completely burned, wherein a reaction of the second exhaust gas purification device 14 . 38 . 60 is detected.

Further, for detecting the reaction of the second exhaust gas purification device 14 . 38 . 60 with the first sensor 16 . 46 . 68 a temperature of exit gas measured from the second exhaust gas purification device 14 . 38 . 60 exit.

After that, the internal combustion engine 4 . 30 . 50 from a second point in time, the normal mixture or optionally a modified normal mixture provided, which has a greater proportion of air than normal mixture, as soon as the monitoring exhaust gas, the at least one first exhaust gas purification device 8th . 12 . 36 . 56 . 58 flows through and the second exhaust gas purification device 14 . 38 . 60 has reached. Fuel of the monitoring exhaust gas, in the second exhaust gas purification device 14 . 38 . 60 is stored and in it is burned during the monitoring with air or oxygen from the possibly modified normal exhaust gas.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102013201734 A1 [0004]
• DE 10339063 A1 [0005]
• DE 10041891 A1 [0006]

Claims (10)

A method for monitoring a second exhaust gas purification device (14, 38, 60) of an exhaust system (2, 32, 52) for an internal combustion engine (4, 30, 50), with which a mixture of air and fuel is burned to exhaust gas, wherein in a flow direction at least one first exhaust gas purification device (8, 12, 36, 56, 58) of the exhaust system (2, 32, 52) is connected downstream of exhaust gas to the internal combustion engine (4, 30, 50) downstream of the second exhaust gas purification device (14, 38, 60) is, wherein the internal combustion engine (4, 30, 50) is provided in a normal operation, a normal mixture of air and fuel having a stoichiometric combustion air ratio, which is burned by the internal combustion engine (4, 30, 50) to a normal exhaust gas , wherein the internal combustion engine (4, 30, 50) for monitoring the second exhaust gas purification device (14, 38, 60) from a first predetermined time point a monitoring mixture of air and fuel is provided, the unt having a first-order combustion air ratio burned by the internal combustion engine (4, 30, 50) into a monitoring exhaust gas, wherein fuel of the monitoring exhaust gas is burned in the second exhaust gas purification device (14, 38, 60) and a reaction of the second exhaust gas purification device (14, 38, 60) is detected. Method according to Claim 1 in which the monitoring to detect the response of the second exhaust gas purifier (14, 38, 60) detects and measures a temperature of exhaust gas exiting the second exhaust gas purifier (14, 38, 60). Method according to Claim 1 or 2 in which the normal mixture is provided back to the internal combustion engine (4, 30, 50) from a presettable second point in time as soon as the monitoring exhaust gas flows through the at least one first exhaust gas purification device (8, 12, 36, 56, 58) and the second Exhaust gas purification device (14, 38, 60) has reached. Method according to Claim 3 in which the combustion air ratio of the exhaust gas is detected and measured upstream of the second exhaust gas purification device (14, 38, 60), the second time occurring as soon as before the second exhaust gas purification device (14, 38, 60) the monitoring mixture with the substoichiometric combustion air ratio is detected. Method according to Claim 3 or 4 , where the second time is determined by a model. Method according to one of the preceding claims, in which a second exhaust gas purification device (14, 38, 60) is monitored, which is designed as a catalyst and / or as a particle filter. A system for monitoring a second exhaust gas purification device (14, 38, 60) of an exhaust system (2, 32, 52) for an internal combustion engine (4, 30, 50), with which a mixture of air and fuel is burned to exhaust gas, wherein in a flow direction at least one first exhaust gas purification device (8, 12, 36, 56, 58) of the exhaust system (2, 32, 52) is connected downstream of exhaust gas to the internal combustion engine (4, 30, 50) downstream of the second exhaust gas purification device (14, 38, 60) is, wherein the internal combustion engine (4, 30, 50) is provided in a normal operation, a normal mixture of air and fuel having a stoichiometric combustion air ratio, which is burned by the internal combustion engine (4, 30, 50) to a normal exhaust gas wherein the system (2, 32, 52) comprises a control device (20, 44, 66) and at least one first sensor (16, 46, 48), wherein the control device (28, 44, 66) is adapted to the combustion air ratio of the mixture to be burned hes set and the internal combustion engine (4, 30, 50) for monitoring the second emission control device from a predetermined first time point to provide a monitoring mixture of air and fuel having a substoichiometric combustion air ratio, of the internal combustion engine (4, 30, 50) a monitoring exhaust gas is burned, wherein fuel of the monitoring exhaust gas is burned in the monitoring in the second exhaust gas purification device (14, 38, 60), wherein the at least one first sensor (8, 12, 36, 56, 58) is formed to detect a reaction of the second exhaust gas purification device (14, 38, 60). System after Claim 7 in which the at least one first sensor (16, 46, 48) is arranged in the flow direction behind the second exhaust gas purification device (14, 38, 60) and is adapted to detect at least one parameter of exit gas that is from the second exhaust gas purification device (14, 38, 60) flows. System after Claim 7 or 8th , comprising at least one second sensor (18, 48, 70) downstream of the at least one first exhaust gas purification device (8, 12, 36, 56, 58) and in front of the second exhaust gas purification device (8, 12, 36, 56, 58) arranged and adapted to detect at least one parameter of exhaust gas before the second exhaust gas purification device (8, 12, 36, 56, 58). System according to one of Claims 7 to 9 comprising a storage system associated with the second exhaust gas purification device (8, 12, 36, 56, 58) and adapted to store fuel in the second exhaust gas purification device (8, 12, 36, 56, 58) until it is burned.

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