DE102008036733A1 - Emission control device diagnosing method for conversion of e.g. nitric dioxide pollutant, in exhaust gas flow of internal combustion engine of motor vehicle, involves determining parameter to characterize aging condition of control device - Google Patents

Abstract

The method involves determining a parameter using a sensor device (11) provided downstream to an emission control device (5), where the parameter characterizes presence of nitric oxide and nitrogen dioxide pollutants. Another parameter is determined using the former parameter, where the latter parameter characterizes an aging condition of the emission control device. A diagnostic signal is generated by comparison of the latter parameter with a threshold value, and the diagnostic signal is set when the threshold value exceeds.

Description

The The invention relates to a method for diagnosing a in an exhaust stream an internal combustion engine of a motor vehicle arranged exhaust gas purification device for converting pollutants entrained in the exhaust stream.

method for diagnosis of an exhaust gas purification device are known. These can be part of a so-called self-diagnosis (on-board diagnosis, OBD). Such a diagnosis can be a statement about a state of the exhaust gas purification device, such as a Catalyst, allow. These may include the emission control device For example, temperature sensors for determining a temperature measurement be assigned.

The document DE 10 2006 034 234 A1 relates to a method for monitoring an exhaust gas purification component of an internal combustion engine by means of a temperature sensor. By detecting and evaluating a temperature transition associated with a modification transition, the exhaust gas purification component can be monitored for an aging state.

The document DE 10 2006 016 906 A1 relates to a device for monitoring an exhaust gas catalyst in the exhaust system of an internal combustion engine. For this purpose, a measuring arrangement is provided which is arranged in the exhaust system such that it assumes a correlated with the temperature of the catalytic converter temperature in most of the operating range of the internal combustion engine, with a cause of thermal damage can be determined.

The document DE 10 2005 056 312 A1 relates to a method for checking the conversion capability of a catalytic converter of an internal combustion engine at least one pollutant component of a lean exhaust gas with λ> 1. From a measurement value _deviation with respect to Δλ a probe signal λ _probe of a downstream of the catalyst disposed High-λ-probe from a λ-actual value λ the exhaust gas downstream of the catalyst, the conversion ability of the catalyst is derived.

task The invention is an improved, in particular as possible exact, monitoring of a working method and / or a condition, in particular aging condition, an exhaust gas purification device, in particular an oxidation catalyst.

The Task is with the features of the independent claim solved.

Thereafter, in a method for diagnosing a disposed in an exhaust gas stream of an internal combustion engine of a motor vehicle exhaust gas purification device for converting entrained in the exhaust gas pollutants determining a presence of at least one pollutant pollutants NO and NO ₂ characteristic first characteristic by means of a downstream of the exhaust gas purification device sensor device and a Determining a state of the emission control device characterizing second characteristic provided by means of the first characteristic. The exhaust gas purification device may be an oxidation catalyst that oxidizes nitrogen oxide (NO) to nitrogen dioxide (NO ₂ ). By means of the sensor device can downstream of the exhaust gas purification device by means of the first characteristic to a state, such as an activity of a noble metal coating, be closed, so that can be derived from this the state characterizing second characteristic.

at An embodiment of the method is generating a diagnostic signal for indicating an aging of the exhaust gas purification device by means of the second characteristic and / or generating the diagnostic signal by means of a comparison of the second characteristic with a threshold value and / or a setting of the diagnostic signal when exceeding the Threshold provided. For example, a diagnostic signal may be to act as a binary signal representing the emission control device as okay or not in order. The second parameter can, in particular via a calculation rule, the diagnostic signal be assigned, wherein on the calculation rule, the diagnostic signal settable, in particular also resettable, is. In the calculation rule This can be, for example, the comparison of the second parameter act with a threshold, the diagnostic signal when exceeded of the threshold is settable. It is possible the diagnostic signal set once the threshold is exceeded to keep. However, it is also possible, with only one-time, for example, briefly exceeding the threshold to reset this again.

In a further embodiment of the method, a determination of a presence of at least one pollutant of the pollutants NO and NO ₂ characteristic third characteristic by means of a exhaust gas purification device upstream further sensor device and / or determining the second characteristic by means of the first characteristic and the third characteristic is provided. The pollutants NO and / or NO ₂ can be determined upstream and downstream of the exhaust gas purification device or measured by means of the further sensor device and the sensor device. In the third parameter and the first parameter For example, each may be the sensor signal of the sensor devices. However, it is also possible to convert the sensor signals into a further variable, for example a concentration of the pollutants. The parameters may therefore be any characteristic variable characterizing a presence of the pollutants, for example sensor raw signals and / or derived variables, for example a concentration or absolute values, for example in grams or moles, for example per unit time or distance of a predefinable driving cycle. Advantageously, the first and the third parameter can be offset from each other, for example by a comparison, wherein an activity of the exhaust gas purification device or the state of the exhaust gas purification device for determining the third characteristic can be concluded. Under state can be understood in particular a functional state and / or an aging state of the exhaust gas purification device. Aging can be caused for example by poisoning and / or washing out a catalytically active material in the exhaust gas purification device. Thermal overloads can also lead to aging or to a reduction in a conversion capability of the exhaust gas purification device.

at Another embodiment of the method is determining the third characteristic by means of a stored Characteristic map of the internal combustion engine provided. Can be advantageous by means of the map known operating conditions of the Internal combustion engine, for example, a known mixture formation and / or load emission levels of pollutants are assigned. The assigned values can be in the third parameter Find entrance.

at Another embodiment of the method is a Determining a correlation relationship of the first characteristic with the third parameter for determining the second Characteristic and / or a consideration a temperature of the exhaust gas purification device in the correlation relationship and / or taking into account a historical value of the second Characteristic provided. The temperature of the exhaust gas purification device affects the conversion ability. Advantageously this influence is taken into account by means of the correlation relationship become. Advantageously, in addition by means of Past value of the second parameter already detected changes in the state of the exhaust gas purification device, For example, an already partially occurred aging, also be considered in the correlation relationship. Advantageous is thereby a more precise determination of the condition, for example a slowly progressive aging, detectable.

at Another embodiment of the method is determining the second parameter depending an operating point of the internal combustion engine is provided. Advantageous can when determining the second characteristic one dependent on the operating point of the internal combustion engine Conversion performance taken into account or compensated become. This can advantageously provide a more accurate statement about the state of the exhaust gas purification device are taken. at An operating point may, for example, be a stationary one Operation of the internal combustion engine, for example with a predefinable Speed and load, act. However, under operating point can also be a specifiable load and speed range are understood. Further By means of an operating point, further environmental parameters, such as a temperature and / or an air pressure defined become. In the broadest sense, under operating point also a predefinable Operation of the internal combustion engine, such as during a Acceleration phase or a coasting operation of the motor vehicle occur, be understood.

In a further embodiment of the method, a first partial variable cNO characterizing a presence of a first pollutant NO of the pollutants in the exhaust gas flow and a second partial variable cNO ₂ characterizing a presence of a second pollutant NO _{2 of} the pollutants in the exhaust gas flow by means of a calculation rule and a one of the part sizes applied inverse operator of the calculation rule for determining the second characteristic and / or determining the second characteristic by means of dividing the second part cNO ₂ by the first part cNO cNO (cNO ₂ / cNO) and / or determining the second characteristic by dividing the second part size by the first part size added with the second part size (cNO ₂ / (cNO + cNO ₂ )) provided. Advantageously, the second characteristic by means of application of the inverse operator is a measure of a conversion capability of the exhaust gas purification device. If it is an oxidation catalyst in the exhaust gas purification device, this NO can convert into NO ₂ , wherein, for example, with increasing aging, ie decreasing conversion ability of the NO ₂ content in the exhaust stream decreases. Thus, as the aging increases, an increase in the second characteristic becomes observable. Advantageously, the diagnostic signal can be set, for example, when the threshold value is reached or exceeded. An inverse operator can be understood to mean an arithmetic operation which, with respect to the associated calculation rule and applied to identical operands, results in the neutral element of the arithmetic operation writing supplies. In the case of an addition, then the calculation rule and the inverse operator in the form of a multiplication of one of the operands with (-1) result in the neutral element zero and in the case of a multiplication in a sweep break the neutral element 1.

at Another embodiment of the method is determining at least one of the parameters by means of a solid electrolyte in at least one of the sensor devices according to a Nernst principle intended. Advantageously, sensor devices can after the Nernst principle also to monitor another, the emission control device downstream components for converting the exhaust stream entrained pollutants are used. The exhaust gas purification device can For example, a storage catalyst and / or on the principle downstream of a selective catalytic reduction (SCR) based catalyst be. Advantageously, the sensor device for control, control and / or monitoring be provided downstream of the components. Advantageously the sensor signal at the same time also for the diagnosis of the upstream Exhaust gas purification device, such as an oxidation catalyst, be used. Additional sensors are not necessary.

Further Advantages, features and details emerge from the following Description, in reference to the drawing, an embodiment is described in detail. Same, similar and / or functionally identical parts are provided with the same reference numerals. Show it:

1 a schematic view of an arranged in an exhaust gas stream of an internal combustion engine of a motor vehicle exhaust gas purification device;

2 a block diagram of in 1 shown arrangement;

3 another block diagram of in 2 shown arrangement, but with a map;

4 another block diagram of in 2 shown arrangement, but with the exhaust gas purification device upstream and downstream sensor devices; and

5 a graph of NO ₂ -Anteils the exhaust stream after the exhaust gas purification device in% above a temperature of the exhaust gas purification device.

1 shows a schematic view of a partially illustrated motor vehicle 1 with an internal combustion engine 3 and an exhaust purification device arranged downstream of this 5 , The exhaust gas purification device 5 has an oxidation catalyst 7 on. The oxidation catalyst 7 is one by means of arrows 9 symbolized exhaust gas flow of the internal combustion engine 3 assigned and designed for converting entrained in the exhaust stream pollutants.

The pollutants may be, for example, hydrocarbons (HC) and nitrogen oxides (NOX). In the internal combustion engine 3 it can be a Überstoecheometrisch, ie with λ values> 1, operable internal combustion engine. By means of the oxidation catalyst 7 can the pollutants with the entrained also in the exhaust stream residual oxygen catalytically converted, oxidized. In particular, by means of the oxidation catalyst 7 a first pollutant NO be converted into a second pollutant NO ₂ . In another, in 1 not shown components for converting entrained in the exhaust gas pollutants pollutants NO and NO _{2 can be} removed from the exhaust stream. These components can be, for example, an NOX storage catalyst and / or an SCR catalyst operating on the principle of selective catalytic reduction.

For controlling, monitoring and / or regulating these components, not shown, the oxidation catalyst 7 a sensor device 11 be downstream. The sensor device 11 is also the means of arrows 9 indicated exhaust gas flow of the internal combustion engine 3 assigned. The sensor device 11 is designed to detect at least one of the pollutants NO and NO ₂ . Advantageously, it is possible by means of the sensor device 11 not only to obtain measured values for the control, monitoring and / or regulation of downstream components, but also a diagnosis of the oxidation catalyst 7 to enable. Alternatively, however, it is also conceivable to use the sensor device 11 only for the diagnosis of the oxidation catalyst 7 to use and independently of downstream components to provide additional sensors. Advantageously, the sensor device 11 differentiate between the first pollutant NO and the second pollutant NO ₂ and a corresponding sensor signal 13 to a control unit 15 hand off.

By means of the control unit 15 For example, a first partial variable cNO and a second partial variable cNO ₂ can be determined from the sensor signal, which represent a corresponding concentration of the first pollutant NO and of the second pollutant NO ₂ . For example, it is advantageously possible to relate the part sizes to one another and from this to an aging state of the part oxidation catalyst 7 close. The sensor device 11 can be designed as a so-called ratio probe, where already the sensor signal 13 a ratio of the pollutants NO and NO ₂ reflects. However, it is also conceivable, this ratio only in the downstream control unit 15 to form, wherein the sensor device is sensitive to each one of the pollutants. With a minimal design, the sensor device 11 be sensitive only to at least one of the pollutants NO and NO ₂ .

The internal combustion engine 3 can be an exhaust gas turbocharger 17 , a charge air cooling 19 , a mixture forming unit 21 for filling a combustion chamber 23 with an ignitable fuel-air mixture. The combustion chamber 23 is an exhaust system 25 downstream, in which the exhaust gas turbocharger 17 and the oxidation catalyst 7 and the sensor device 11 are switched. In addition, the internal combustion engine 3 an exhaust gas recirculation 27 with an exhaust gas recirculation cooling system 29 exhibit. The exhaust gas turbocharger 17 is a suction unit 31 upstream of the intake of fresh air.

2 shows a block diagram of in 1 shown arrangement of the internal combustion engine 3 and this downstream exhaust system 25 of the motor vehicle 1 , The sensor device 11 is a unit 33 the control unit 15 for processing the sensor signal 13 downstream. At the unit 33 For example, it may be a control and / or regulation of at least one parameter of the exhaust gas flow of the internal combustion engine 3 act. The unit 33 can realize, for example, a λ control. Alternatively and / or additionally, it is conceivable by means of the unit 33 a control and / or regulation downstream components, such as a dosage of an additional reagent, for example, for a selective catalytic reduction to realize. Accordingly, the unit 33 for processing a target value 35 be designed. The unit 33 is a mixture control 36 , in particular for driving the mixture-forming unit 21 , the control unit 15 downstream. The unit 33 can be controlling on the mixture control 36 act. Mixture formation unit 21 is part of the internal combustion engine 3 or assigned upstream of this and controls a mixture composition of the internal combustion engine 3 ,

By means of the mixture composition of the internal combustion engine 3 can also be a composition of the exhaust stream 3 of the internal combustion engine 3 to be influenced. In the broadest sense, the mixture control 36 the control unit 15 all for mixture preparation of the internal combustion engine 3 control relevant units or parameters. This can, for example, the exhaust gas turbocharger 17 , the mixture forming unit 21 , the exhaust gas recirculation 27 and / or the suction unit 31 be. By means of the mixture control 3 may be a composition of the exhaust gas flow of the internal combustion engine 3 be adjusted or influenced.

The unit 33 can also be used to process a temperature signal 37 of the oxidation catalyst 7 be designed. The temperature signal 37 can with a temperature of the oxidation catalyst 7 and / or the exhaust gas flow of the internal combustion engine passed through this 3 correlate. To determine the temperature signal 37 can an in 2 not shown temperature sensor the oxidation catalyst 7 be assigned.

The control unit 15 also has a diagnostic unit 39 on that on data 41 the control unit 15 can access. Alternatively and / or additionally, it is possible for the diagnostic unit 39 independent of the control unit 15 to realize as a separate entity. The diagnostic unit 39 For example, the sensor signal 13 and / or the temperature signal 37 evaluate. In particular, from the sensor signal 13 For example, a first parameter characterizing the presence of at least one pollutant of the pollutants NO and NO ₂ can be determined. The sensor signal 13 can represent this characteristic. However, it is also possible to use the sensor signal 13 continue to process first and derive from this the first parameter. By means of this first parameter can by means of the diagnostic unit 39 a second characteristic is generated, which is a state of the oxidation catalyst 7 indicates, for example, a functional state or aging state. The second parameter may be, for example, a diagnostic signal 43 which, in the sense of an on-board diagnosis (OBD), has an oxidation catalyst aged beyond an intolerable level 7 displays. However, the second parameter may also be a derived quantity which, for example by means of a comparison with a threshold value, sets the diagnostic signal 43 can trigger.

3 shows a further block diagram of the in 2 shown arrangement, but in addition with a map 45 of the internal combustion engine 3 , By means of the map 45 of the internal combustion engine 3 can the diagnostic unit 39 additional sizes are provided. This can be, for example, calculated, in particular by means of the map 45 detectable, concentrations of pollutants NO and NO ₂ upstream of the oxidation catalyst 7 act. By comparing the values of the map 45 with the measured sensor signal 13 and a calculation rule, the second characteristic can be determined.

4 shows another graph of the in the 2 and 3 shown arrangement, but in contrast with a further sensor device 47 , The further sensor device 47 is also in the exhaust system 25 guided exhaust gas flow of the internal combustion engine 3 assigned. The further sensor device 47 generates another sensor signal 49 which characterizes the presence of at least one pollutant of the pollutants NO and NO ₂ . Compared to the representation according to 3 Thus, the presence of the pollutants NO and / or NO ₂ upstream of the oxidation catalyst 7 by means of the further sensor device 47 be measured. In addition, it is possible to measure the measured values of the further sensor device 47 also with the means of the map 45 according to 3 compare values to be calculated, in particular to charge, or both equally take into account and the diagnostic unit 39 to make available to be determined second characteristic.

5 shows a diagram 51 with an x-axis 53 and a y-axis 59 , The diagram 51 gives measured values of an emission control device 5 , for example, in the 1 - 4 shown oxidation catalyst 7 again.

On the x-axis 53 is a temperature of the exhaust gas flow of the internal combustion engine 3 and / or the oxidation catalyst 7 applied, such as by means of the temperature signal 37 winnable. The temperature can be on the x-axis 53 For example, be applied between 0 ° and 700 ° Celsius. On the y-axis, a proportion of the pollutant NO _{2 is shown} after the Oxidati onskatalysator, for example in a range between 0 and 100 percent. In this case, the NO ₂ content may be based on a total of the pollutants NO ₂ + NO.

A graph 61 who in 5 is symbolized by a solid line, shows that the NO ₂ content is temperature-dependent and at about 380 ° C assumes a maximum. The graph 61 For example, by means of the sensor signal 13 by means of the diagnostic unit 39 the control unit 15 be determinable. At least, depending on an operating point of the internal combustion engine 3 single points of the graph 61 be determinable.

By dotted lines are in the diagram 51 an upper limit curve 63 and a lower limit curve 65 located. Between the limit curves 63 and 65 results in a means of a double arrow 67 indicated spreading area 69 in which the graph 61 scatters. The scatter depends on production-related different conversion capabilities of the oxidation catalyst 7 from. The lower limit curve 65 For example, it may correspond to a boundary catalyst whose deviation in a production of the oxidation catalyst 7 is still being accepted. However, it may also be an independent lower limit curve 65 act, which falls below the diagnostic signal 43 is set.

The lower limit curve 65 thus represents a plurality of lower thresholds, wherein when falling below a corresponding point of the graph 61 the diagnostic signal 43 is triggerable. By means of an arrow 71 is an aging area 73 of the diagram 51 indicated. The aging area 73 is below the lower limit curve 65 and gets from this as well as from the x-axis 53 limited. Once for a given temperature of the oxidation catalyst 7 a measured actual value 55 of the graph 61 the means of the lower limit curve 65 predetermined threshold 57 below the diagnostic signal 43 be set. The setting of the diagnostic signal 43 is synonymous with an unacceptable aging, so deterioration of the conversion performance of the oxidation catalyst 7 ,

Advantageously, a self-diagnosis or on-board diagnosis or OBD of the oxidation catalyst 7 by means of the sensor device 11 and / or the further sensor device 47 respectively. Advantageous is the conversion performance or an aging behavior of the oxidation catalyst 7 directly on the basis of exhaust components of the exhaust gas flow of the internal combustion engine 3 measured and determined.

Advantageously, the sensor device can do this 11 and / or the further sensor device 47 be designed so that they can distinguish between NO and NO ₂ . The sensor device 11 is to the downstream of the oxidation catalyst 7 arranged and can be a function of the temperature of the oxidation catalyst 7 determine the NO / NO ₂ conversion, that is, the conversion of NO to NO ₂ . This degree of conversion of the oxidation catalyst is advantageous 7 a very accurate measure of the state of the oxidation catalyst 7 , in particular the aging state or a poisoning state of the oxidation catalyst 7 ,

In the internal combustion engine 3 it may be, for example, a diesel engine whose exhaust gas flow in practice has comparatively large temperature fluctuations. Advantageously, in comparison of a sole temperature measurement by means of the evaluation of the sensor signal 13 the sensor device 11 and / or the further sensor signal 49 the further sensor device 47 a much more accurate determination of the state of the oxidation catalyst 7 respectively. Advantageously, a very accurate statement about the state of the oxidation catalyst 7 be obtained, so that even the strictest emission standards can be maintained. Advantageously can be dispensed with complex catalyst temperature models. Alternatively and / or additionally, however, it is possible to take this into account additionally.

About the ratio of the pollutants NO ₂ / NO or NO ₂ / NOX can on the aging state of the oxidation catalyst 7 be inferred. To generate the ratio, the sensor signal 13 the sensor device 11 be used. Advantageously, the determination of the aging state can be done very accurately, since the aging of the oxidation catalyst 7 directly measured and evaluated. Furthermore, unnecessary and / or incorrect fault memory entries can be avoided by means of very accurate aging detection. Advantageously, if necessary, additional temperature sensors can be saved if an already necessary NOX sensor is fitted as standard to the oxidation catalytic converter 7 is arranged downstream.

Also advantageous is a determination during an entire operating life of the internal combustion engine 3 and for all operating points possible, wherein advantageously independent of the measurement of temperatures in transient operating conditions or by a light-off behavior, the determination of the state of the exhaust gas purification device 5 is possible. Advantageously, the sensor device 11 , which may be present, for example, for monitoring and operating a NOX aftertreatment system, not shown, also for monitoring the upstream oxidation catalyst 7 be used. Advantageously, by means of the sensor device 11 for monitoring or diagnosis of the operation or activity of the emission control device 5 or of the oxidation catalyst 7 downstream of the exhaust gas purification device 5 a concentration of at least one of the exhaust gas components NO and / or NO ₂ in the exhaust gas flow of the internal combustion engine 3 measured and from the measured concentration a state, in particular functional state, or aging state, of the oxidation catalyst 7 be determined.

Advantageously, the relationship can be used that over an oxidation catalyst 7 NO is oxidized to NO ₂ . The ratio of NO ₂ to NOX, as in 5 shown downstream of the oxidation catalyst 7 , can metrologically via the sensor device 11 , in particular designed as NOX sensor and / or NOX sensor ratio sensor, are detected and evaluated. With increasing aging or poisoning of the oxidation catalyst 7 takes the ratio NO ₂ / NO respectively. NO ₂ / NOX due to the decreasing activity of a noble metal coating of the oxidation catalyst 7 steadily off. The NO ₂ content downstream of the oxidation catalyst 7 depends on the specific properties of the noble metal coating as well as the temperature. Advantageously, once a correlation can be measured and by means of a characteristic curve or the characteristic field 45 in the control unit 15 be filed. The lower limit curve 65 for example, can represent such a correlation. As by means of the sensor device 11 directly the activity of the noble metal coating can be measured, can advantageously a more accurate and much more reliable determination of the state of the oxidation catalyst 7 occur, as would be possible, for example, in a determination of characteristic temperature sizes.

The sensor device 11 can specifically distinguish between NO and NO ₂ .

Advantageously, a further increase in accuracy can be achieved when upstream of the oxidation catalyst 7 the concentration of at least one of the exhaust gas components NO and NO ₂ by means of the further sensor device 47 measured and in addition to determining the condition or aging determination of the oxidation catalyst 7 is used, since thus also a relative change in the NO and / or NO ₂ concentration can be measured and determined directly ( 4 ).

A cost-effective alternative is the concentration or proportion of at least one of the exhaust gas components NO or NO ₂ in the engine exhaust gas or the exhaust gas flow of the internal combustion engine 3 by means of the map 45 to investigate ( 3 ).

Advantageously, it is conceivable to determine the state of the oxidation catalyst 7 a correlation relationship between a NO concentration (cNO) before and after the oxidation catalyst 7 depending on the catalyst temperature and / or a space velocity. It is possible, for example, to determine a relative concentration of NO ₂ to NO x as a function of the catalyst temperature based on the catalyst volume. Advantageously, a determined NO ₂ : NOX ratio then corresponds to a value of the state of the oxidation catalytic converter correlating therewith 7 or a catalyst aging. Advantageously, this correlation can be measured once for a given catalyst and, for example, in the control unit 15 be deposited.

Furthermore, it is advantageously conceivable to achieve increased accuracy, a dependence of the proportion NO ₂ : NOX in the exhaust gas flow of the internal combustion engine 3 additionally from operating points of the internal combustion engine 3 to take into account. This advantageously also an operating point-dependent Change in a NOX raw emission of the internal combustion engine 3 berücksichtigbar. In particular, it can be advantageous in a measurement of the correlation relationship between NO and / or NO ₂ before and after the oxidation catalyst 7 a determination made for different operating conditions and thus one to the dynamic in-stationary operation of the internal combustion engine 3 adapted correlation relationship are established.

Advantageously, the process can be carried out with any selective NO or NO ₂ sensor. For example, a working according to the Nernst principle sensor for the sensor device 11 and / or further sensor device 47 be provided. In particular, a sensor operating according to the Nernst principle can advantageously be used, which has a solid-state electrolyte membrane which is selectively sensitive to NO ₂ in a ppm concentration range.

The 1 - 4 show a device for monitoring the operation or the state of the exhaust system or the exhaust system 25 of the internal combustion engine 3 arranged oxidation catalyst 7 or the exhaust gas purification device 5 , It is advantageous in the exhaust system 25 downstream of the oxidation catalyst 7 the sensor device 11 arranged to measure the concentration of NO and / or NO ₂ , that of the control unit 15 upstream of the sensor signal 13 the state, in particular functional state and / or aging state of the oxidation catalyst 7 , certainly.

1

motor vehicle

3

internal combustion engine

5

exhaust gas purification device

7

oxidation catalyst

9

arrow

11

sensor device

13

sensor signal

15

control unit

17

turbocharger

19

Intercooling

21

Mixture formation unit

23

combustion chamber

25

exhaust system

27

Exhaust gas recirculation

29

Exhaust gas recirculation cooling

31

suction

33

unit

35

Target value

36

mixture control

37

temperature signal

39

diagnostic unit

41

dates

43

diagnostic signal

45

map

47

sensor device

49

sensor signal

51

diagram

53

X axis

55

Actual value

57

threshold

59

y-axis

61

graph

63

upper limit curve

65

lower limit curve

67

double arrow

69

stray field

71

arrow

73

aging range

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 102006034234 A1 [0003]
• DE 102006016906 A1 [0004]
• - DE 102005056312 A1 [0005]

Claims (8)

Method for the diagnosis of an exhaust gas flow in an internal combustion engine ( 3 ) of a motor vehicle ( 1 ) arranged exhaust gas purification device ( 5 ) for converting pollutants entrained in the exhaust gas flow, with determination of a first parameter characterizing the presence of at least one pollutant of the pollutants nitrogen oxide (NO) and nitrogen dioxide (NO ₂ ) by means of one of the exhaust gas purification device (US Pat. 5 ) downstream sensor device ( 11 ), Determining a state of the exhaust gas purification device ( 5 ) Characterizing second characteristic by means of the first characteristic. The method of claim 1, comprising at least one of the following: generating a diagnostic signal ( 43 ) for indicating an aging of the exhaust gas purification device ( 5 ) by means of the second parameter, - generation of the diagnostic signal ( 43 ) by means of a comparison of the second parameter with a threshold value, - setting of the diagnostic signal ( 43 ) when the threshold is exceeded. Method according to one of the preceding claims, with at least one of the following: Determining a third parameter indicative of the presence of at least one pollutant of the pollutants NO and NO ₂ by means of one of the exhaust gas purification device (US Pat. 5 ) upstream further sensor device ( 47 ), - determining the second parameter by means of the first parameter and the third parameter. Method according to the preceding claim, with - determining the third parameter by means of a stored characteristic map ( 45 ) of the internal combustion engine ( 3 ). Method according to one of the preceding claims, with at least one of the following: determining a correlation relationship of the first parameter with the third parameter for determining the second parameter, taking into account a temperature of the exhaust gas purification device 5 ) in the correlation relationship, - taking into account a past value of the second characteristic. Method according to one of the preceding claims, comprising: determining the second parameter as a function of an operating point of the internal combustion engine ( 3 ). Method according to one of the preceding claims, comprising at least one of the following: - offsetting a first partial variable (cNO) characterizing a presence of a first pollutant of the pollutants in the exhaust gas flow and a second partial variable (cNO ₂₎ characterizing a presence of a second pollutant of the pollutants in the exhaust gas flow ) by means of a calculation rule and an inverse operator of the calculation rule applied to one of the part sizes for determining the second parameter, determining the second parameter by dividing the second component by the first component (cNO ₂ / cNO), determining the second parameter by dividing the second component second part size by the first part size added to the second part size (cNO ₂ / (cNO + cNO ₂ )). Method according to one of the preceding claims, comprising: determining at least one of the characteristic quantities by means of a solid state electrolyte of at least one of the sensor devices ( 11 . 47 ) according to a Nernst principle.