DE102014017829A1 - Method for checking a metering device for functionality and exhaust aftertreatment device for a vehicle - Google Patents

Abstract

The invention relates to a method for checking a dosing device (16) for functionality, which is designed to introduce a reducing agent (18) for the exhaust aftertreatment in an exhaust line (20) of a vehicle. In this case, at least one measured value relating to the reducing agent (18) is detected. Based on the at least one measured value, an amount of the reducing agent (18) introduced into the exhaust gas line (20) is determined. The quantity determined on the basis of the at least one measured value is compared with a quantity taken from a storage container (12) for the reducing agent (18), the functionality of the metering device (16) being assessed on the basis of the comparison. Furthermore, the invention relates to an exhaust gas aftertreatment device for a vehicle.

Description

The invention relates to a method for checking a metering device for proper functioning. The metering device is designed to introduce a reducing agent for the exhaust aftertreatment in an exhaust system of a vehicle. In the method, at least one measured value is detected, which relates to the reducing agent. Based on the at least one measured value, an amount of the reducing agent introduced into the exhaust gas line is determined. Furthermore, the invention relates to an exhaust gas aftertreatment device for a vehicle.

Legal regulations such as the EC 692/2008 make it necessary to check dosing devices for their function, which are designed to introduce a reducing agent for reducing the nitrogen oxide content in the exhaust gas in the exhaust gas of a vehicle. The monitoring of the accuracy in the metering of the reducing agent in the exhaust line, however, can not be guaranteed at present certainly under all circumstances. Thus, it is difficult to determine, for example, in the short-distance operation and at very low metering amounts of reducing agent, whether there is a deviation between a desired amount of the reducing agent to be introduced into the exhaust gas and an actual amount.

In this context, the describes DE 10 2011 113 552 A1 a method for estimating the amount of a reducing agent injected into the exhaust gas passage of a vehicle, which serves to reduce the nitrogen oxide content in the exhaust gas. Here, a first amount of the introduced into the exhaust reducing agent is estimated by a pulse width modulated control signal is evaluated, with which an injector is controlled, which emits the reducing agent in the exhaust gas. This pulse width modulated control signal correlates with a mass flow of the introduced into the exhaust reducing agent, so that due to this relationship, the amount of reducing agent introduced into the exhaust gas can be estimated. In a second estimation method for determining the amount of reducing agent injected into the exhaust gas, the pressure in a pipe between a pump and the injector is monitored. Based on the pressure is closed on the injected into the exhaust gas amount of reducing agent. The estimated amounts of the reducing agent introduced into the exhaust gas in these two ways are compared. If the difference in the quantities is too great, an error of the reducing agent injection system is inferred.

In the DE 10 2011 113 552 A1 Thus, two measured values relating to the reducing agent are detected in order to be able to estimate the amount of reducing agent introduced into the exhaust gas in two different ways. However, such a method is susceptible to errors and is inaccurate, especially at low doses.

Furthermore, the describes EP 1 860 294 A1 a method for checking the introduction of a reducing agent into an exhaust gas aftertreatment device, wherein the consumed amount of reducing agent is determined by monitoring the level in a tank for the reducing agent. The consumption of reducing agent is related to a traveled distance, a certain fuel consumption, a certain travel time or a consumption of air. The air is thereby mixed with a urea-water solution, and a mixture of droplets of the urea-water solution in the air is introduced into the exhaust gas via an injection nozzle.

A disadvantage here is the fact that a Dosiermengenbestimmung, which is based on the distance covered, the fuel consumption, the travel time or the consumption of air is not effective. Namely, in the real use of vehicles longer lasting driving conditions may occur in which no metering of reducing agent into the exhaust gas takes place. This is the case, for example, when the vehicle is mainly operated on short distances, since in such a short-distance operation, the exhaust system remains relatively cold and consequently no dosage of the reducing agent takes place. The same applies if a hybrid vehicle is partially operated purely electrically. Even then, neither the distance covered nor the travel time allow conclusions to be drawn about the amount of reducing agent introduced into the exhaust gas.

Object of the present invention is therefore to provide an improved method of the type mentioned above and an exhaust gas aftertreatment device designed for carrying out the method.

This object is achieved by a method having the features of patent claim 1 and by an exhaust gas aftertreatment device having the features of patent claim 10. Advantageous embodiments with expedient developments of the invention are specified in the dependent claims.

In the method according to the invention, the amount determined on the basis of the at least one measured value is compared with an amount taken from a storage container for the reducing agent. On the basis of the comparison of the amounts determined in these different ways, the functionality of the metering device is assessed. This is based on the knowledge that especially in the case of very small doses the test for the Dosiermengengenauigkeit is particularly difficult. If, however, the quantity removed from the storage container corresponds at least essentially to that quantity which was determined on the basis of the at least one measured value, it can be concluded that the dosing device is in satisfactory working order. While many single, small doses are difficult to determine each individually, a dosing sum value can be more easily provided and compared with the consumption of the reducing agent, ie with the amount of reducing agent removed from the storage container.

Thus, regardless of the driving style and the associated consumption of reducing agent and regardless of the duration of a driving cycle, the duration of engine operation during a driving cycle and the type of driving reliable monitoring of the metering device can be achieved. And in particular a legally compliant monitoring of the consumption of reducing agent is guaranteed. Consequently, an improved method for checking the metering device for serviceability is provided.

In this case, in particular, a satisfactory functioning of the metering device can be inferred if the quantity determined on the basis of the at least one measured value and the quantity taken from the storage ratio differ by no more than a predetermined value. This predetermined value may in particular correspond to a legally permitted deviation and be, for example, 50%. However, in such a case, if the quantity determined on the basis of the measured value and the quantity withdrawn from the storage container differ from one another by more than the predetermined value, then a negative diagnosis result is output, that is to say an inadequate functioning of the metering device.

The at least one measured value, which relates to the reducing agent, preferably comprises an opening period during which a closing element is in an open position, wherein the closing element is designed to close and open an outlet of the metering device. If the closure element is transferred to the open position, then the reducing agent can exit via the outlet from the metering device, that is to say be introduced into the exhaust gas. Such opening periods can be determined very precisely, so that it is particularly easy to deduce the amount determined on the basis of the measured value over the opening periods.

In this case, it has proven to be advantageous if the respective opening period is correlated with a respective metered quantity. Such a correlation can be derived in particular from a characteristic curve or the like previously determined dependence of these two parameters. Then can be closed very quickly and easily from the opening period on the dosing.

It is furthermore advantageous if a total metering quantity is determined from a plurality of temporally successive opening periods, which is introduced into the exhaust gas line in a period comprising the opening periods. In this case, therefore, the metering quantities correlating with the respective opening periods are preferably summed up and the total metered quantity thus obtained. The total metering quantity then corresponds to the quantity determined on the basis of measured values, the measured values relating to the reducing agent.

In this case, it advantageously does not matter whether the opening periods occur within a driving cycle, ie between the starting and stopping of the vehicle, or whether the opening periods occurring in several consecutive driving cycles are used to determine the total metering. Thus, in particular with each short driving cycles, during which only very small amounts of reducing agent are introduced into the exhaust gas, nevertheless, the functionality of the metering device to be checked. As a result, an integrated, legally compliant monitoring of the metering device with regard to the metering quantity accuracy can be achieved, even if only very small amounts of reducing agent are introduced into the exhaust gas during very short driving cycles with partially still cold exhaust system.

Preferably, the total dosage amount is then determined as soon as a sum of the opening periods exceeds a predetermined threshold. Predetermining such a threshold increases reliability in determining the total dosage amount and thus in checking the metering device for functionality. The predetermined threshold may be, for example, about 30 minutes. For then there is a sufficiently long total opening time of the closure element, which allows the determination of the amount of reducing agent based on the at least one measured value with particularly high accuracy.

It is particularly advantageous if the quantity removed from the storage container is determined by evaluating measured values which are provided by at least one fill level sensor. That's the way to be special reliably and accurately determine the amount of reducing agent removed from the storage container. The at least one fill level sensor can, in particular at the beginning and at the end of a period of time encompassing the opening periods of the closure element, measure the respective fill level in the storage container and thus make it possible to determine the amount removed.

In this case, it has proven to be advantageous if, when determining the amount taken from the storage container, it is taken into account whether reducing agent has been added to the storage container within the period comprising the opening periods. Such refilling operations or refueling operations increase the total quantity of reducing agent removed from the storage container.

In order to be able to use low refueling quantities in the diagnosis, a separate, separate integrator is preferably used in determining the withdrawn from the storage container amount of reducing agent, which is used only in the context of reviewing the metering on the functionality. By means of such an own integrator, namely very small refueling quantities can be detected.

This is not the case with another integrator which, for example, serves to determine a remaining range, that is to say a route length for which the amount of reducing agent present in the storage container is presumably sufficient. This further integrator, which can be used, for example, to warn a vehicle driver when the storage container is nearly empty or even cause the vehicle to be switched off, usually has a lower temporal resolution than that which is preferably used for checking the dosing device for functionality , separate integrator.

The further integrator used to determine the remaining range or for the warning scenario or Abschaltszenario, which may also be coupled with a display in the instrument cluster of the vehicle, can also be used in the context of an Inducementsystems (incentive system) are used, in which the driver is advised, the storage container to fill with reducing agent, so refuel.

It has also proven to be advantageous if the quantity determined on the basis of the at least one measured value is compared with the quantity taken from the storage container only if a value of the quantity determined on the basis of the at least one measured value is less than a predetermined threshold value. This is based on the finding that with a comparatively large metering quantity of the reducing agent, the checking of the metering device for functionality is possible with high accuracy and reliability. Then no adjustment with the withdrawn from the storage container amount needs to be made. However, if dosing below the predetermined threshold, so it is advantageous for reasons of reliability and accuracy in monitoring the dosing to make an adjustment with the withdrawn from the storage container amount.

The predetermined threshold may be, for example, 8 grams of reductant. If, in fact, reducing agent of this order of magnitude is introduced into the exhaust gas within one driving cycle, it can be ascertained with comparatively good accuracy whether the amount of reducing agent actually introduced into the exhaust gas corresponds to this setpoint quantity. The method is particularly simple because not always the consumption of the reducing agent needs to be taken into account based on the amount withdrawn from the storage container, but only if this is advantageous due to the accuracy in determining the Dosiermengen.

The functionality of the metering device is preferably assessed by taking the at least one value of the quantity determined on the basis of the at least one measured value, if within a predetermined period of time there is at least one value which is greater than the predetermined threshold value. If, therefore, within the predetermined period of time at least one value is present which is greater than the predetermined threshold value, then this at least one value is considered decisive and used to assess the functionality of the metering device. This makes the process particularly easy.

In order to be able to carry out a particularly reliable diagnosis of the metered quantities, it may be provided, in particular, to take into account two or more values, for example up to six values which are greater than the predetermined threshold value and which were determined within the predetermined period of time. This allows a dispersion of measured values to be taken into account, thus improving the accuracy of the diagnosis.

However, if within the predetermined period of time no value is present which is greater than the predetermined threshold value, then the quantity determined on the basis of the at least one measured value is compared with the quantity withdrawn from the storage container and thus the functionality of the metering device with regard to the accuracy during Introducing the reducing agent in the exhaust gas checked.

The exhaust gas aftertreatment device according to the invention for a vehicle comprises a storage container for a reducing agent, which is used in the exhaust gas aftertreatment, in particular for reducing a nitrogen oxide content in the exhaust gas. The exhaust aftertreatment device comprises a metering device for introducing the reducing agent into an exhaust gas system of the vehicle. Furthermore, a control device is provided which is designed to determine an amount of the reducing agent introduced into the exhaust gas line based on at least one measured value relating to the reducing agent. The control device is furthermore designed to compare the amount determined on the basis of the at least one measured value with a quantity taken from a storage container and to judge the functional efficiency of the metering device on the basis of the comparison.

The advantages and preferred embodiments described for the method according to the invention also apply to the exhaust aftertreatment device according to the invention.

The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention. Thus, embodiments are also included and disclosed by the invention, which are not explicitly shown or explained in the figures, however, emerge and can be produced by separated combinations of features from the embodiments explained.

Further advantages, features and details of the invention will become apparent from the claims, the following description of preferred embodiments and from the drawings. Showing:

1 schematically an exhaust aftertreatment device for a vehicle, by means of which the accuracy can be determined when dosing a urea solution in the exhaust gas;

2 a flowchart with two variants of the method for determining the accuracy of the dosing;

3 a flowchart in which one of the two variants of the method according to 2 is shown in detail;

4 Activation signals as a function of time, which cause opening of a valve needle of an injector, which introduces the urea solution in the exhaust gas; and

5 a characteristic which indicates a dependence of the amount of urea solution introduced into the exhaust gas from the opening time of the valve needle.

An in 1 shown exhaust aftertreatment device 10 for a vehicle includes a storage container in the form of a tank 12 in which a reducing agent 18 stockpiled for exhaust aftertreatment. In the reducing agent 18 it is, for example, an aqueous urea solution, which is available under the brand name AdBlue ^® .

The urea solution is pumped 14 to a metering device in the form of an injector 16 promoted, which is the reducing agent 18 in an exhaust system 20 injects the vehicle. The pump 14 can be designed in particular as a reciprocating pump. Downstream of the injector 16 is in the exhaust system 20 an SCR catalyst 22 arranged. From that in the urea solution or such a reducing agent 18 contained urea is released in the hot exhaust ammonia, which in the SCR catalyst 22 in a selective catalytic reduction reaction (SCR = selective catalytic reduction), which converts the nitrogen oxides contained in the exhaust gas to nitrogen and water.

The Tank 12 has at least one level sensor 24 on, by means of which the level of urea solution in the tank 12 and record overnight refills. The metering system is preferably designed as a return-free metering system, in which the pump 14 no more urea to the injector 16 supplies, as by means of this in the exhaust system 20 is metered. The injector 16 is preferably designed as a needle valve, which is an example electromagnetically actuated valve needle 26 as a closure element comprises.

For differently designed injectors 16 can as a closure element for closing and opening an outlet of the injector 16 a differently designed component are used, such as a slider or the like. The valve needle 26 is preferably operated clocked and with a definable depending on a desired Dosiermengenstrom open-to-duty ratio. The valve needle 26 is thus operated pulse width modulated and this from a control device 28 controlled accordingly.

By means of in 1 exhaust gas aftertreatment device shown 10 can be the injector 16 or such a metering device for its accuracy when introducing the urea solution in the exhaust line 20 check out. Here, a first variant of the method 30 and a second method variant 32 run parallel in time (cf. 2 ).

The first process variant 30 is particularly suitable for a first diagnostic result 34 to provide with a certain accuracy or reliability. This first process variant 30 is preferably used when a lot of the exhaust gas 20 introduced reducing agent 18 above a predefinable limit or threshold. The limit value may in this case describe an absolute metering quantity and / or a metered quantity stream.

For technical reasons such as leakage of the pump 14 and tolerances of the components of the dosing system, however, is the accuracy or reliability of the first diagnostic result 34 then lower, if the absolute metered quantities and / or the Dosiermengenströme are small. Such small doses or Dosiermengenströme are less than the absolute Dosiermengen or Dosiermengenströme, which are above the limit and the first diagnostic result 34 to lead.

The limit value can be, for example, 8 grams and it can be provided that within a driving cycle sixteen times each 0.5 grams of reducing agent 18 in the exhaust system 20 at successive metering events to reach this absolute amount of 8 grams.

So is an above the limit or threshold amount of the reducing agent 18 in the exhaust system 20 introduced, so can be by means of the first method variant 30 a reliable first diagnostic result 34 receive. For carrying out the first method variant 30 can in the controller 28 a monitoring unit 36 be provided, which determines the Dosiermengengenauigkeit dynamically and therefore as a dynamic monitoring of a consumption deviation designed device (Dynamic Consumption Deviation Monitor, CDM) can be designated.

In the first process variant 30 can the monitoring unit 36 the first diagnostic result 34 for example, based on an evaluation of the pressure of the reducing agent 18 in a section of a pipe 44 the dosing system between the pump 14 and the injector 16 provide. For this purpose, for example, the pressure of the reducing agent 18 with an operating characteristic of the pump 14 be matched, such as with a number of pump strokes per unit time in a reciprocating pump, with a pump speed or the like. The in the exhaust system 20 Amount introduced can also be based on the volume of the pipe 44 between the pump 14 and the injector 16 and the number of fillings of the line 44 be determined per unit of time. The first diagnostic result 34 can be provided continuously or permanently and / or from time to time.

At the beginning of the basis of 2 illustrated method is a time counter or timer 38 started. After a predetermined period of time is checked, whether by means of the monitoring unit 36 when carrying out the first process variant 30 at least one valid diagnostic result 34 could be determined. If not, what is in 2 through an arrow 40 is illustrated, so by means of the second variant of the method 32 certain second diagnostic result 42 considered authoritative.

The second process variant 32 is particularly suitable at below the predetermined limit or threshold absolute Dosiermengen and / or Dosiermengenströmen the second diagnostic result 42 to provide with a desired accuracy or reliability.

The second process variant 32 So it is especially used with a small amount of dosage. Such small below-threshold absolute dosing and / or dosing flow rates may result, for example, during low engine load vehicle operating periods or at low exhaust gas temperatures. At low exhaust gas temperatures namely a dosage, ie an introduction of the reducing agent 18 in the exhaust system 20 locked as long as the SCR catalyst 22 still can not ensure a sufficient reduction of the nitrogen oxide content in the exhaust gas. This is the case, for example, for short journeys. Even with a vehicle with hybrid drive and high proportions of time with electric drive within a drive cycle can result in low absolute Dosiermengen.

To determine the second diagnostic result 42 If the amounts of reductant metered in each case immediately after each other in the metering operating phases are added up to a metered-dose sum value. Thus, the metering operating phases are taken into account, in which actually the reducing agent 18 discharged into the exhaust becomes. In this case, it may be provided to add up so many individually metered amounts of reducing agent until the total duration of the associated successive metering operating phases reaches a predefinable time span, for example a period of 30 minutes. Even when dosing small quantities in the respective individual dosing operating phase, a sufficiently large total dosing quantity thus results over the predeterminable time span.

The second diagnostic result 42 is due to the operation of another monitoring unit 46 provided, whose operation is based on the in 3 illustrated flowchart is explained. This monitoring unit 46 can be referred to as a device for static monitoring of a consumption deviation, ie as a static consumption deviation monitor (CDM).

In the second variant of the method 32 Namely, the Dosiermengensummenwert or the total dosage is compared with a consumption value, which from the tank 12 taken amount of the reducing agent 18 equivalent. This consumption value is determined by the control device 28 determined by measuring the level sensor 24 be evaluated. For determining the fill level values in the tank 12 can also be based on readings from multiple level sensors 24 in the tank 12 be resorted to.

It becomes a beginning 48 the diagnosis of the level in the tank 12 measured. Likewise will end up 50 the diagnosis of the level in the tank 12 by means of the level sensor 24 recorded (compare 3 ). The beginning 48 the diagnosis is in an in 4 shown graphs 52 denoted by t ₀ . The end 50 the diagnosis is in the graph 52 denoted by t _end . Accordingly, in 4 a period ranging from t ₀ to t _end 54 specified. At the beginning 48 and at the end 50 this period 54 So in each case the level in the tank 12 certainly. The beginning 48 and at the end 50 measured levels in the tank 12 be according to 3 in one step 56 used to get out of the tank 12 to determine the amount of reducing agent removed.

If in the period 54 or time interval reducing agent in the tank 12 is refilled, so this is in a further step 58 considered. According to the in 3 Thus, the process flow illustrated is the sum of any refueling 60 or refills in step 58 considered. Refueling 60 corresponding values are preferably from a nonvolatile memory, such as an EEPROM of the controller 28 based.

In this case, a separate integrator is preferably used which is capable of recognizing even very small refueling quantities. In step 58 is so in the period 54 from the tank 12 taken amount of the reducing agent 18 as data value. If necessary, this data value takes into account in the period 54 carried out refueling or refueling 60 ,

In a further step 62 becomes a flow 64 of the reducing agent 18 through the injector 16 determined. This happens as based on 4 is illustrated by taking into account opening periods 66 , ie of times in which the valve needle 26 an outlet of the injector 16 releases and thus the introduction of the reducing agent 18 in the exhaust system 20 allows (cf. 1 ).

Because the injector 16 preferably as a needle valve with the clocked actuated valve needle 26 is formed, are the Dosierbetriebsphasen, ie the phases of introduction of the reducing agent 18 in the exhaust system 20 through the opening times of the valve needle 26 , so the opening periods 66 Are defined. The opening periods 66 can preferably be determined from the time pattern of a drive signal for the needle valve, which in the graph 52 in 4 is shown. The duration of the respective opening periods 66 corresponds to the times in which the valve needle 26 is controlled and is in 4 exemplified by the values t ₁ , t ₂ , t ₅ , t ₆ and t _n .

The with the opening periods 66 corresponding dosing operating phases of duration t _i let on the respective amounts of the exhaust gas into the line 20 metered reducing agent 18 shut down. For this purpose, preferably a previously determined dependence can be used, for example in the form of a 5 shown characteristic 68 ,

In one the characteristic 68 comprehensive graph 70 in 5 is on an ordinate 72 the dosage is plotted and on an abscissa 74 the duration t _{i of} the opening periods 66 , According to the characteristic 68 leads a longer duration of the respective opening period 66 to a larger within this opening period 66 metered amount of reducing agent 18 in the exhaust system 20 , This example, based on the in the control device 28 stored characteristic 68 derivable dependence of the variables mentioned is characteristic of the metering system and in particular of the metering pressure and the injector 16 dependent.

The total dosing or dosing sum is thus in the present case as the sum of all individual, in the successive opening periods 66 with the respective duration t _i , ie with the valve needle open 26 determined in the exhaust gas introduced individual quantities m _i . This can be provided in particular that the sum of the opening periods 66 , So the accumulated duration of the considered Dosierbetriebsphasen is a predetermined period of, for example, 30 minutes. This time span of 30 minutes is appropriate 4 however shorter than the period 54 in which the individual opening periods 66 to come to rest.

In a next step 76 in the 3 shown flow chart are the Dosiermengen total, ie in the period 54 in the exhaust system 20 introduced total metering, compared with the consumption value of the reducing agent, ie with the difference of the levels of the tank 12 at the times t ₀ and t _end . If necessary, refueling operations taking place in the period t _End - t ₀ are taken into account.

Dodge those in the crotch 76 Compared to each other by more than a predetermined amount from each other, an appropriate error message is issued or generated. This will be done in a further step 78 checked whether the difference in quantities is lower than, for example, a lower statutory limit 80 , Furthermore, in one step 82 checks if the difference is greater than an upper legal limit 84 , According to this in the steps 78 . 82 The second test result is the second diagnostic result 42 receive.

Lies within the time period (for example, 30 minutes) assigned to the predetermined time period 54 a predetermined number of after the first process variant 30 determined first diagnostic results 34 before, these are considered authoritative. It can be provided that at least one valid value exists. On the other hand, lies within the period associated with the total operating time with the predefinable time period 54 no valid value for the first diagnostic result 34 before or are less initial diagnostic results 34 before than required, it will be after the second process variant 32 determined second diagnosis result 42 considered authoritative.

After the expiration of the period of time assigned to the predeterminable time period, that is to say at the time t _End , a new diagnostic cycle is set by resetting the time counter or timer 38 started. The first diagnostic cycle may begin, for example, with the first dosing pulse after the vehicle is put into service.

The method described above ensures that after a certain dosing period, for example after a dosing time of 30 minutes, a valid diagnosis result 34 . 42 with regard to quantity accuracy. In the case of low metered quantities delivers namely the second process variant 32 such a result. For this, the value of the level in the tank 12 at the beginning of the diagnostic period in the non-volatile memory of a controller, so the controller 28 written and compared with a value at the end of the time. Also, the value of the level in the tank measured at the end of each drive cycle 12 is stored in the non-volatile controller memory. Any replenished quantities are cumulated and also saved. If that's about refueling 60 corrected difference between the starting value and the final value of the tank level and the opening periods 66 determined amount of the introduced reducing agent 18 to differentiate more than a certain deviation from each other, will be a negative diagnostic result 42 output. To determine the permissible deviation, in particular the currently legally permitted deviation can be used, which is 50%.

Regardless of the driving style and the exhaust system 20 introduced amount of reducing agent 18 and also regardless of the duration of a respective driving cycle and the engine operating time and the type of driving operation (in particular a purely electric driving in a hybrid vehicle) can thus a deviation of the intended for exhaust aftertreatment target consumption of the actual consumption of reducing agent 18 be monitored in accordance with the law.

LIST OF REFERENCE NUMBERS

10

exhaust treatment device

12

tank

14

pump

16

injector

18

reducing agent

20

exhaust gas line

22

SCR catalyst

24

level sensor

26

valve needle

28

control device

30

process variant

32

process variant

34

diagnostic result

36

monitoring unit

38

timer

40

arrow

42

diagnostic result

44

management

46

monitoring unit

48

beginning

50

The End

52

graph

54

Period

56

step

58

step

60

refueling

62

step

64

flow

66

Opening period

68

curve

70

graph

72

ordinate

74

abscissa

76

step

78

step

80

limit

82

step

84

limit

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

• EC 692/2008 [0002]
• DE 102011113552 A1 [0003, 0004]
• EP 1860294 A1 [0005]

Claims (10)

Method for checking a metering device ( 16 ), which is designed to be a reducing agent ( 18 ) for the exhaust aftertreatment in an exhaust line ( 20 ) of a vehicle in which at least one of the reducing agent ( 18 ) ( 66 ), and in which, based on the at least one measured value ( 66 ) one in the exhaust line ( 20 ) introduced amount of the reducing agent ( 18 ) is determined, characterized in that the basis of the at least one measured value ( 66 ) determined quantity with one from a storage container ( 12 ) for the reducing agent ( 18 ) is compared, whereby the functionality of the metering device ( 16 ). Method according to Claim 1, characterized in that the at least one measured value contains an opening period ( 66 ) during which a closure element ( 26 ) is in an open position, which for closing and opening an outlet of the metering device ( 16 ) is trained. Method according to claim 2, characterized in that the respective opening period ( 66 ) is correlated with a respective dosage amount. A method according to claim 2 or 3, characterized in that from a plurality of chronologically successive opening periods ( 66 ) a total dosage amount is determined, which in one of the opening periods ( 66 ) ( 54 ) is introduced into the exhaust system. A method according to claim 4, characterized in that the total dosage amount is determined when a sum of the opening periods ( 66 ) exceeds a predetermined threshold. Method according to one of claims 1 to 5, characterized in that the from the storage container ( 12 ) is determined by evaluating measured values, which of at least one level sensor ( 24 ) to be provided. Method according to Claim 6, in which reference is again made to Claim 4 or 5, characterized in that in determining the product from the storage container ( 12 ), whether within the opening periods ( 66 ) comprehensive period ( 54 ) Reducing agent ( 18 ) in the storage container ( 12 ) was refilled. Method according to one of claims 1 to 7, characterized in that based on the at least one measured value ( 66 ) determined quantity then with the from the storage container ( 12 ) is compared, if a value of the basis of the at least one measured value ( 66 ) is less than a predetermined threshold. A method according to claim 8, characterized in that the functionality of the metering device ( 16 ) by taking the at least one value based on the at least one measured value ( 66 ) is determined, if within a predetermined period of time there is at least one value which is greater than the predetermined threshold value. Aftertreatment device for a vehicle, with a storage container ( 12 ) for a reducing agent ( 18 ) for exhaust aftertreatment, with a metering device ( 16 ) for introducing the reducing agent ( 18 ) in an exhaust line ( 20 ) of the vehicle, and with a control device ( 28 ), which is designed based on at least one of the reducing agent ( 18 ) ( 66 ) one in the exhaust line ( 20 ) amount of the reducing agent, characterized in that the control device ( 28 ) is designed to be based on the at least one measured value ( 66 ) determined quantity with one from a storage container ( 12 ) and the comparison of the functionality of the metering device ( 16 ) to judge.

Images