DE102005058299A1 - Method of diagnosing exhaust gas recirculation (EGR) in IC engine e.g. petrol engine, involves determining storage capacities of catalyst during closed and open EGR, and comparing both capacities for EGR abnormalities - Google Patents

Abstract

A storage catalyst (12) is located downstream of an exhaust pipe (11) connected to an EGR line (21). The EGR line is connected to an air intake pipe (31). The storage capacities of the storage catalyst during open and closed EGR operations are determined and then compared. Abnormality of EGR operation can be determined based on the difference between storage capacities.

Description

State of technology

The The invention relates to a method for adapting exhaust gas recirculation systems and / or for the diagnosis of exhaust gas recirculation in internal combustion engines with single or multi-flow exhaust systems, wherein at least a portion of the exhaust banks each having an exhaust gas recirculation line each with an exhaust gas recirculation valve are assigned over the at least a portion of the exhaust gas is supplied to a suction pipe and wherein each exhaust bank with a storage catalyst for receiving at least one exhaust gas component and with a downstream exhaust gas sensor equipped, based on the measuring signals a filled storage catalyst can be recognized.

Internal combustion engines, which are operated at least in phases in lean operation (lambda> 1), feature usually over an external exhaust gas recirculation. through one opening into the suction pipe Exhaust gas recirculation line This burned air-fuel mixture from the exhaust system the supplied to the engine Fresh air mixed. The amount of the supplied exhaust gas is over a Engine control by an exhaust gas recirculation valve controlled.

The external exhaust gas recirculation can of various disorders to be affected. Some errors can by correcting the opening the exhaust gas recirculation valve be compensated. Other disorders can not be compensated and lead to a deterioration the exhaust emissions. In countrys, where an on-board diagnostic (OBD) is required, the Motor control in such a case, issue an error message. In both cases must be the amount of actually recirculated exhaust gas be determined, it being for the OBD is sufficient to detect if the actual amount returned is more than one predetermined value of the desired Quantity deviates.

One example for an error that can be compensated in principle is one Narrowing of the exhaust gas recirculation line by addition of carbon black, oil residues or Condensate (sooting). An example of a bug that generally is not can be compensated but leads to an error message is a leak in the exhaust gas recirculation line.

From the DE 103 27 691 For example, a method of monitoring exhaust gas recirculation of an internal combustion engine by pressure sensing in which exhaust gas is recirculated from an exhaust side of a combustion chamber assembly via an exhaust gas recirculation passage to an intake side of the combustion chamber assembly is known. In this case, a pressure profile is detected in at least one combustion chamber (ZYL 1 ... ZYLn) and from this a thermodynamic parameter is determined as the actual value. Furthermore, a target value of the parameter which takes into account the current operating point of the internal combustion engine is provided, and a deviation between desired value and actual value is determined, and information about the current state of exhaust gas recirculation is obtained from the deviation compared to its standard state.

It is still a method for the adaptation and diagnosis of exhaust gas recirculation known, in which the intake manifold pressure on the one hand by a pressure sensor on the other hand taking into account the position of the Exhaust gas recirculation valve and other parameters such as the speed, the throttle angle, the camshaft position and the tank ventilation is modeled. Out The difference between the measured and the modeled value can be a malfunction of the exhaust gas recirculation closed become. However, this requires that the throttle already with the exhaust gas recirculation valve closed was adapted.

adversely with both procedures is that with internal combustion engines with mehrflutigen Exhaust systems with exhaust gas recirculation from several exhaust banks no assignment of a fault to the respective exhaust gas recirculation is possible.

It It is an object of the invention to provide a method of the type described above To provide species, which in both single and multi-flush Exhaust systems a specific diagnosis and adaptation of exhaust gas recirculation allows.

Advantages of invention

The The object of the invention is achieved in that the storage capacity at least a storage catalyst during a first phase of operation with open exhaust gas recirculation and during one second phase of operation at least largely closed Exhaust gas recirculation is determined and that at differences between the specific storage capacities up a disorder closed in the exhaust gas recirculation becomes.

The determination of the storage capacity with open exhaust gas recirculation is based on the assumption of an intact exhaust gas recirculation. In a disturbance in the exhaust gas recirculation, which leads, for example, to a reduced amount of recirculated exhaust gas, the storage catalytic converter is acted upon in this phase of operation with more exhaust gas and thus a larger amount of at least one exhaust gas component einzubichernden than provided and fills correspondingly faster. Therefore, it becomes too Next assumed a reduced storage capacity of the storage catalytic converter. When determining the storage capacity of the storage catalytic converter in an operating phase with largely closed exhaust gas recirculation the source of exhaust gas recirculation error is excluded, the determination of the storage capacity gives the actual value. The comparison of the specific storage capacities thus leads to the clear detection and assignment of errors in the respective exhaust gas recirculation.

In A preferred embodiment of the invention is the storage capacity of the storage catalyst under consideration modeled the operating conditions of the internal combustion engine and / or becomes the storage capacity determined by measurement. The chosen method is for determination the storage capacity from the available measuring possibilities the respective internal combustion engine, for example, from the built-in Sensors, depending.

A reliable diagnosis of a fault in the recirculated exhaust gas quantity can be achieve that closed on a fault in the exhaust gas recirculation if the difference between the determined storage capacities is a exceeds the specified limit. In this case, the fault tolerance in the determination of the storage capacity is after each one selected To consider methods. The limit should be selected be that the fault tolerances of the respective metrologically or do not overlap modeled values for the storage capacities.

Prefers a first determination of the storage capacity during a Storage phase of the storage catalytic converter until the beginning of a regeneration phase and a second determination of the storage capacity during a regeneration phase of the storage catalyst. These are operating phases, the regularly from to pass through the internal combustion engine. While the storage phase is the exhaust gas recirculation in Generally open, while the regeneration of the storage catalytic converter with the exhaust gas recirculation valve closed carried out becomes.

Become in dual-flow exhaust systems with a first and a second Exhaust bank the storage capacities the respective storage catalysts in a first phase of operation when open Exhaust gas recirculation and in a second phase of operation at least largely closed Exhaust gas recirculation determined, so can for each exhaust bank separately a fault determination of exhaust gas recirculation and a clear assignment of a fault to the respective exhaust bank carried out become. Only this makes it possible an adaptation of the respective exhaust gas recirculation valve. Furthermore, can with a necessary repair of the exhaust gas recirculation system targeted the defective Exhaust gas recirculation servicing be set.

In A preferred embodiment of the invention is based on a disorder in closed at least one exhaust gas recirculation, if for a storage catalyst in an exhaust bank in the first phase of operation a lower storage capacity and in the second phase of operation, an approximately equal or greater storage capacity than at the storage catalyst in the other exhaust bank is determined, being closed to a reduced exhaust gas recirculation from the exhaust bank at which in the first phase of operation when open Exhaust gas recirculation one lower and in the second phase of operation largely closed Exhaust gas recirculation one nearly same or larger storage capacity of the storage catalytic converter was detected as the other exhaust bank. It is assumed that both exhaust banks approximately supplied the same amount of exhaust gas and about that be returned the same amount of exhaust gas should and that in both exhaust banks the same storage catalysts are used. The relative comparison between the two storage catalysts forms a good reference. Sources of error, for example, one based on the operating parameters the internal combustion engine modeled determination of the storage capacity of the Storage catalysts, have frequent the same influence on both exhaust banks, flow accordingly in both values and are thus not considered in the comparison of the two exhaust banks. Only asymmetric influencing parameters, such as a clogged exhaust gas recirculation of one Exhaust bank, find entrance in the rating. The reliability the error determination leaves so opposite significantly improve an individual rating within an exhaust bank.

at The relative rating of two exhaust banks, it has to be advantageous proved when during an operating phase with open Exhaust gas recirculation for the storage catalytic converter a lower storage capacity is assumed, in which a downstream exhaust gas sensor first the achievement of the maximum storage capacity of the storage catalytic converter for the detected to be stored exhaust gas component. The determination of which Storage catalyst is first completely filled, can be easily for example with the storage catalytic converters downstream exhaust gas sensors, realize. In this case, a fast-filled storage catalyst initially on a small storage capacity the storage catalytic converter or a defective exhaust gas recirculation close. Only the comparison with the determined storage capacity with the exhaust gas recirculation valve closed leaves one clear assignment of the cause.

In one embodiment of the invention takes place the detection of a fault in the exhaust gas recirculation according to an alternative method and the assignment of the fault to the respective exhaust gas recirculation of an exhaust bank by evaluating the determined storage capacities of the storage catalytic converters. As alternative methods, the methods known from the prior art may be used which, if appropriate, enable a more precise detection of a deviation in the total exhaust gas quantity, that is to say from a plurality of exhaust gas banks, compared to the proposed method. By determining and evaluating the storage capacities of the storage catalytic converters, it is then only necessary to recognize whether the fault is due to all involved or in only one exhaust gas recirculation and - in the latter case - in which. The adaptation of the exhaust gas recirculation system can then take place via the quan- tity of recirculated exhaust gas quantified in the alternative method. According to this method, the quantification of the shortage of recirculated exhaust gas and, derived therefrom, the adaptation of the exhaust gas recirculation system can be carried out in accordance with the exact method available for the detection of shortcomings in the exhaust gas recirculation.

One Field of application for The method provides that in internal combustion engines with at least a NOx storage catalyst during lean operating phases of the Internal combustion engine stored in the NOx storage catalyst amount NOx is determined to be during a regeneration phase of the NOx storage catalytic converter, the stored amount of nitrogen oxide NOx_Reg is determined and that in case of differences between the given quantities Nitrogen oxides NOx and NOx_Reg are closed to a fault in the exhaust gas recirculation becomes. NOx storage catalysts are used in internal combustion engines that can run in lean operation. This is especially true for Petrol engines with direct injection, in shifts or can be driven in homogeneous-lean operation. Furthermore, such Internal combustion engines over one have external exhaust gas recirculation, wherein the amount of recirculated exhaust gas through an exhaust gas recirculation valve is controlled. The process can thus be based on existing components the internal combustion engine and the exhaust system. The determination of Amount of stored NO x NOx can be determined by known methods, for example by modeling based on the modeled NOx content in raw exhaust gas. Also, the regeneration of the NOx storage catalyst takes place by a known method by periodic short rich operation the internal combustion engine. It is in the lean operation phase the Exhaust gas recirculation open while in the regeneration phase, the exhaust gas recirculation valve is closed.

The Determination of storage capacity a NOx storage catalytic converter with open and closed Exhaust gas recirculation valve This can be done by a filled NOx storage catalytic converter on the basis of the measurement signal of the NOx storage catalytic converter downstream NOx exhaust gas sensor is detected that up to this point in the NOx storage catalyst present quantity of nitrogen oxide NOx is modeled and that in one subsequent Regeneration phase based on the regeneration of the NOx storage catalyst required Amount of rich exhaust gas actually stored in the NOx storage catalyst amount Nitrogen Oxine NOx_Reg is determined. The NOx exhaust gas sensor detects a filled NOx storage catalyst at a high NOx concentration or a high NOx mass flow and dissolves then over a downstream control a regeneration of the NOx storage catalyst out. The by then open Exhaust gas recirculation valve stored amount of NOx can be based on the modeled NOx content be modeled in the raw gas. The determination of NOx storage capacity in the Regeneration phase based on the regeneration consume rich exhaust gas corresponds to a known method, with the modern internal combustion engines and exhaust systems functioning the exhaust gas-relevant component NOx storage catalyst is diagnosed. Here is the needed Quantity of rich exhaust gas equivalent to the total amount of NOx and oxygen at the beginning of the regeneration stored in the NOx storage catalyst were. The oxygen storage capacity of the NOx storage catalyst can be determined by other measurement methods and so on the NOx storage capability the storage catalytic converter are closed. Because the amount of stored NOx once over the entire storage phase until regeneration and then over entire regeneration phase is determined, both quantities are included intact exhaust gas recirculation in principle the same and can be compared accordingly.

A separate diagnosis of exhaust gas recirculation in twin-flow exhaust systems can be achieved by modeling the quantities of nitrogen oxides NOx_B1 and NOx_B2 received in the respective NOx storage catalysts in dual-flow exhaust systems with a first and a second exhaust bank B1 and B2 for each exhaust bank during the lean operating phases and during a regeneration phase, the stored amounts of nitrogen oxide NOx_Reg_B1 and NOx_Reg_B2 are determined in the respective NOx storage catalytic converters. In this case, it can be concluded that there is a fault in at least one exhaust gas recirculation if, for a NOx storage catalytic converter in an exhaust gas bank, a smaller NOx storage capacity during the lean operating phases and approximately during the regeneration phase same or greater NOx storage capacity than the NOx storage catalyst in the other exhaust bank is determined, which is a reduced exhaust gas recirculation from the exhaust bank is closed, in which in the lean operating phases a lower and in the regeneration phase, an approximately equal or greater NOx storage capacity of the NOx storage catalyst was detected as the other exhaust bank. For example, if one of the two exhaust gas recirculation lines, for example, from the exhaust bank B1, clogged, less exhaust gas is returned from the exhaust bank B1 in the common intake manifold than from the exhaust bank B2. Accordingly, more NOx-containing exhaust gas remains on the exhaust bank B1. As a result, the storage catalyst in the exhaust bank B1 is filled faster than that in the exhaust bank B2. This diagnosis is initially based on a smaller NOx storage capacity of the NOx storage catalyst from exhaust bank B1 close. With a regeneration of the NOx storage catalytic converters triggered by a filled NOx storage catalyst, which takes place together and at the same time, at least in internal combustion engines with a common intake manifold, the measurement of the required regeneration gas can be concluded that more NOx was stored in the storage catalytic converter on the exhaust gas bank B1 as in the on exhaust bank B2. From this discrepancy can be concluded that an asymmetry of the exhaust gas recirculation and thus a fault in an exhaust gas recirculation. The assignment of the fault to an exhaust bank is clear.

A Assignment of a fault to an exhaust gas recirculation of An exhaust bank can take place in that at differences between the specific amounts of nitrogen oxide NOx_B1 and NOx_Reg_B1 and / or at Differences between the specific amounts of nitrogen oxide NOx_B2 and NOx_Reg_B2 on a fault in the exhaust gas recirculation in the respective exhaust bank B1 and / or B2 is closed. From the stored values can be an asymmetry between the two exhaust banks be quantified. Because of inaccuracies especially in one Modeling NOx storage is the advantage of this evaluation However, in a qualitative statement, which exhaust gas recirculation faulty is.

Corresponding another evaluation option can in a dual-flow exhaust system with an exhaust gas recirculation of each exhaust bank then to an asymmetric amount of recirculated exhaust gas for certain quantities of nitrogen oxide NOx_Reg_B1> NOx_B1 and NOx_Reg_B2 ≤ NOx_B2 or at NOx_Reg_B1 ≤ NOx_B1 and NOx_Reg_B2> NOx_B2 is detected.

A another possibility the error detection is possible by the fact that at approximately the same certain amounts of nitrogen oxide NOx_B1 and NOx_B2 at the same time strong difference of the specific amounts of nitrogen oxide NOx_Reg_B1 and NOx_Reg_B2 on a fault the exhaust gas recirculation closed becomes. Here, only the relation of the specific amounts of NOx on exhaust bank becomes B1 and B2 judged what has the advantage, regardless of the uncertainty in the modeling of the absolute amounts of NOx stored be.

drawing

The Invention will be described below with reference to one shown in the figures embodiment explained in more detail. It demonstrate:

1 a schematic representation of an internal combustion engine with a single-flow exhaust system with an exhaust bank and exhaust gas recirculation,

2 a schematic representation of an internal combustion engine with a dual-flow exhaust system with two exhaust banks, each with an exhaust gas recirculation,

3 a flowchart for determining a fault in an exhaust gas recirculation,

4 an alternative evaluation for determining a fault in an exhaust gas recirculation,

5 an alternative evaluation to determine a fault in an exhaust gas recirculation.

description the embodiments

1 shows a schematic representation of an internal combustion engine 30 with a single-flow exhaust system 10 with an exhaust bank 11 and an exhaust gas recirculation 20 , The internal combustion engine 30 is via a suction pipe 31 Fresh air supplied. The exhaust gases are in the exhaust system 10 on the one hand a storage catalytic converter 12 and subsequently an exhaust gas sensor 13 fed, on the other hand, at least part of the exhaust gas by means of the external exhaust gas recirculation 20 via an exhaust gas recirculation line 21 and an exhaust gas recirculation valve 22 in the suction pipe 31 passed back and mixed there with the fresh air. In this case, the amount of recirculated exhaust gas from a control unit, not shown, with the aid of the exhaust gas recirculation valve 21 according to the respective operating parameters of the internal combustion engine 30 set.

In the illustrated embodiment, the internal combustion engine corresponds 30 a gasoline engine with gasoline direct injection, which operated in shift operation or in homogeneous-lean operation can be and at least phased in lean operation (lambda> 1) is operated. The storage catalyst 12 is as a (NOx) storage catalyst 12 Running as it is today for internal combustion engines 30 the type described is common. The exhaust gas sensor 13 is as a (NOx) exhaust gas sensor 13 executed.

Faults in exhaust gas recirculation 20 which, for example, by addition of carbon black, oil residues or condensate in the exhaust gas recirculation line 21 and the exhaust gas recirculation valve 22 or by a leak in the exhaust gas recirculation line 21 be caused and lead to a change in the amount of recirculated exhaust gas, have a negative impact on the NOx emissions and the torque of the internal combustion engine 30 , This can be achieved by adapting the exhaust gas recirculation valve 22 , So by a correction of the opening of the exhaust gas recirculation valve 22 to be compensated. For this purpose, the amount of actually recirculated exhaust gas must be determined.

In internal combustion engines 30 with (NOx) storage catalysts 12 the stored NOx must be discharged by periodic short rich operation. This process, referred to as regeneration, is triggered by the engine control, not shown, according to various criteria. In addition, particularly regenerations are of interest, which are triggered because the engine control has detected a filled NOx storage of the storage catalytic converter. A filled (NOx) storage catalyst 12 detects the engine control when the downstream of the (NOx) storage catalytic converter 12 installed (NOx) exhaust gas sensor 13 in which the (NOx) storage catalyst 12 leaving exhaust gas detects a high NOx concentration or a high NOx mass flow. The regenerator also depends on the signal of the (NOx) exhaust gas sensor 13 from. Alternatively, the regenerator may also be from the signal of the (NOx) storage catalyst 12 downstream, not shown lambda probe with two-point characteristic can be detected.

Furthermore, in internal combustion engines 30 with (NOx) storage catalysts 12 as exhaust gas-relevant components a diagnosis of the (NOx) storage catalytic converters 12 be performed. This is the NOx storage capacity of the (NOx) storage catalytic converters 12 certainly. For this purpose, basically two methods are known which are used alternatively: Method I: With the aid of the (NOx) exhaust gas sensor 13 becomes a filled NOx storage catalyst 12 recognized. The at that time in the (NOx) storage catalytic converter 12 The present NOx level is modeled by the engine controller based on the modeled NOx content in the raw exhaust gas.

Method II: The amount of rich exhaust gas required for regeneration is measured. This is equivalent to the total amount of NOx and oxygen present at the beginning of the regeneration in the (NOx) storage catalyst 12 stored. The oxygen storage capacity of the (NOx) storage catalytic converter 12 can be determined by other measuring methods. Thus, the NO x storage capability of the (NO x) storage catalyst 12 getting closed.

According to the method of the invention, by combining the methods I and II, which are used today for the diagnosis of (NOx) storage catalysts 12 be used on a fault in the exhaust gas recirculation 20 getting closed. It is exploited that, in method I, in the (NOx) storage catalytic converter 12 stored amount of NOx in lean operating phases of the internal combustion engine 30 and thus with the exhaust gas recirculation valve open 22 during process II during regeneration of the (NOx) storage catalyst 12 and thus with the exhaust gas recirculation valve closed 22 the stored amount of NOx is determined. Is, for example due to deposits or a leak in the exhaust gas recirculation line 21 During the lean operating phases of the internal combustion engine 30 a reduced amount of exhaust gas compared to the setpoint in the intake manifold 31 led back, so is the (NOx) storage catalytic converter 12 Accordingly, more exhaust gas and NOx supplied as in the modeling of the stored amount of NOx by the engine control, which of an intact exhaust gas recirculation 20 goes out, is determined. The modeling thus results in a smaller amount in the (NOx) storage catalyst 12 stored NOx than is actually stored. When determining the amount of NOx stored during regeneration, the source of the error is exhaust gas recirculation 20 excluded because the exhaust gas recirculation valve 22 at least largely closed during this phase. The determination of in the (NOx) storage catalytic converter 12 stored amount of NOx therefore corresponds - apart from measurement errors - the actual amount. At a difference between the determined according to method I and method II amounts of in the (NOx) storage catalytic converter 12 stored NOx can thus clearly on a fault in the exhaust gas recirculation 20 getting closed.

Based the determined difference, the engine control an adaptation in the Exhaust gas recirculation system carry out or output a corresponding error message.

The method can also be correspondingly in a dual-flow exhaust system 10 perform, in which only by an exhaust bank 11 an exhaust gas recirculation 20 in the suction pipe 31 is provided.

2 shows a schematic representation of an internal combustion engine 30 with a dual-flow exhaust system 10 with two exhaust banks 11.1 . 11.2 and in each case an exhaust gas recirculation 20.1 . 20.2 in a common intake manifold 31 lead. Every exhaust bank 11.1 . 11.2 is a storage catalyst 12.1 . 12.2 and a downstream exhaust gas sensor 13.1 . 13.2 assigned. Every exhaust gas recirculation 20.1 . 20.2 contains an exhaust gas recirculation line 21.1 . 21.2 and an exhaust gas recirculation valve 22.1 . 22.2 , About the at least part of the exhaust gas of the internal combustion engine 30 , controlled by the exhaust gas recirculation valves 22.1 . 22.2 , the fresh air in the suction pipe 31 can be supplied.

Also in this embodiment corresponds to the internal combustion engine 30 a gasoline engine with gasoline direct injection, which can be operated in shift operation or in homogeneous-lean operation and which is operated at least in phases in lean operation (lambda> 1). The storage catalysts 12.1 . 12.2 are as (NOx) storage catalysts 12.1 . 12.2 Running as it is today for internal combustion engines 30 the type described is common. The exhaust gas sensors 13.1 . 13.2 are as (NOx) exhaust gas sensors 13.1 . 13.2 executed.

In such dual-flow exhaust systems 10 is also a regeneration of filled (NOx) storage catalysts 12.1 . 12.2 provided according to the described method. In this case, the regeneration by the first-filled (NOx) storage catalyst 12.1 . 12.2 based on the measuring signals of the (NOx) exhaust gas sensors 12.1 . 12.2 triggered by the engine control, not shown, and takes place for both (NOx) storage catalytic converters 12.1 . 12.2 simultaneously.

In such dual-flow exhaust systems 10 each with an exhaust gas recirculation 20.1 . 20.2 in a common intake manifold 31 the process of the invention can be used particularly advantageously. Clogged one of the two exhaust gas recirculation lines 21.1 . 21.2 , for example, the exhaust bank (B1) 11.1 , so from the exhaust bank (B1) 11.1 less exhaust gas in the intake manifold 31 returned as from exhaust bank (B2) 11.2 , Accordingly, more NOx-containing exhaust gas remains on exhaust bank (B1) 11.1 as on exhaust bank (B2) 11.2 , As a result, the (NOx) storage catalyst 12.1 faster filled with NOx than its counterpart. From this fact, according to the method I described above, for diagnosing (NOx) storage catalysts 12.1 . 12.2 to a smaller storage capacity of the (NOx) storage catalytic converter 12.1 closed. In a through a filled (NOx) storage catalytic converter 12.1 . 12.2 However, triggered regeneration leaves the measurement of the required Regeniergases, as in the method II for the diagnosis of (NOx) storage catalysts 12.1 . 12.2 to conclude that in the (NOx) storage catalyst 12.1 more NOx was stored than in the (NOx) storage catalytic converter 12.2 on exhaust bank (B2) 11.2 , This discrepancy points to an asymmetry in the exhaust gas recirculation 20.1 . 20.2 and thus to a fault in the exhaust gas recirculation 20.1 . 20.2 shut down. The fault can clearly be an exhaust gas recirculation 20.1 . 20.2 , in the example of exhaust gas recirculation shown 20.1 , be assigned. A targeted adaptation of the affected exhaust gas recirculation valve 22.1 . 22.2 or one of the respective exhaust gas recirculation 20.1 . 20.2 assigned error message is now possible.

This distinguishes the method of the invention from the known methods, which only a total error in the exhaust gas recirculation 20.1 . 20.2 can determine, but no assignment of the error to the respective exhaust gas recirculation 20.1 . 20.2 enable. Nevertheless, it can be advantageous to use the method according to the invention with conventional methods for detecting errors in exhaust gas recirculation 20.1 . 20.2 in particular, when the conventional methods allow a more accurate quantification of the total shortage of recirculated exhaust gas. The inventive method is then used to disturb the respective exhaust gas recirculation 20.1 . 20.2 assigned. The targeted adaptation of the affected exhaust gas recirculation valve 22.1 . 22.2 can then take place on the basis of the determined by the conventional method default amount of exhaust gas recirculated.

Furthermore, it can be provided, the inventive method for the diagnosis of exhaust gas recirculation 20.1 . 20.2 only if an error in the total amount of recirculated exhaust gas has already been detected by a conventional method.

In 3 is a flowchart of the way to determine a fault in an exhaust gas recirculation in a dual-flow exhaust system 10 represented according to the inventive method.

In a first functional block, during a lean operating phase, the gas is introduced into the storage catalytic converters 12.1 . 12.2 stored NOx_B1 and NOx_B2 modeled. In this case, as with the following designations, the indices B1 and B2 refer to the respective exhaust gas bank (B1) 11.1 and (B2) 11.2 , Furthermore, the exhaust gas mass flows m_Abg_B1 and m_Abg_B2 and the masses of recirculated exhaust gas m_AGR_B1 and m_AGR_B2 are integrated. Depending on the signal of the (NOx) exhaust gas sensors 13.1 and 13.2 will be in the first query 41 checked by the engine control if a (NOx) storage catalytic converter 12.1 . 12.2 is filled. Once a (NOx) storage catalytic converter 12.1 . 12.2 is filled in a second function block 42 the values NOx_B1 and NOx_B2 are stored. It then begins in a third function block 43 the regeneration of the (NOx) storage catalysts. During regeneration is in a fourth function block 44 the amount of regeneration required exhaust gas for the exhaust bank (B1) 11.1 , NOx_Reg_B1, and for the exhaust bank (B2), NOx_Reg_B2.

Based on a second query 45.1 the evaluation takes place, whether an asymmetry in the exhaust gas recirculation 20.1 . 20.2 is present. The criteria for this are the queries NOx_Reg_B1> NOx_B1 and NOx_Reg_B2 ≤ NOx_B2 or NOx_Reg_B1 ≤ NOx_B1 and NOx_Reg_B2> NOx_B2. The query first compares the quantities of stored NOx determined within the two operating phases within an exhaust gas bank 11.1 . 11.2 and then performs a comparison of these relations between the two exhaust banks 11.1 and 11.2 by. Are the conditions of the query 45.1 not met, so is the exhaust gas recirculation 20.1 . 20.2 according to a fifth functional block 47.1 okay. On the other hand, there was an asymmetry between the amounts of stored NOx in the two (NOx) storage catalytic converters determined by the two methods 12.1 . 12.2 determined, ie, are the conditions of the query 45.1 fulfilled, so is according to a sixth function block 46.1 to a fault in an exhaust gas recirculation 20.1 . 20.2 closed. Thereupon, the engine control unit can adapt the respective exhaust gas recirculation valve 22.1 . 22.2 or an error message is issued.

4 shows another possible evaluation for determining a fault in an exhaust gas recirculation 20.1 . 20.2 , A query 45.2 closes as an alternative to query 45.1 to the function block 44 out 3 at. The query criterion here is: NOx_B1 ≠ NOx_Reg_B1 and / or NOx_B2 ≠ NOx_Reg_B2. The query 45.2 therefore compares only the for an exhaust bank 11.1 . 11.2 determined values and can therefore also for exhaust systems 10 with only one exhaust bank 11 be used. The query NOx_B2 ≠ NOx_Reg_B2 then disappears accordingly. If the conditions are met, function block can be used accordingly 46.2 be concluded on a discrepancy between the nominal and the actual amount of recirculated exhaust gas. The stored values can be achieved with dual-flow exhaust systems 10 the asymmetry between the two exhaust gas recirculations 20.1 . 20.2 quantify. In practice, however, account must be taken of the inaccuracy, particularly in the modeling of NOx storage, so that the benefit of the method lies mainly in a qualitative statement for large deviations.

In 5 is another alternative evaluation for determining a fault in an exhaust gas recirculation 20.1 . 20.2 shown. Here, too, closes a query 45.3 as an alternative to the query 45.1 to the function block 44 , as in 3 shown on. The query criterion NOx_Reg_B1 ≠ NOx_Reg_B2 can be used for dual-flow exhaust systems 10 used where an equal NOx flow in both exhaust banks 11.1 . 11.2 that is, where NOx_B1 is approximately equal to NOx_B2. In the case of strongly deviating values NOx_Reg_B1 and NOx_Reg_B2, an asymmetrical exhaust gas recirculation and thus a fault in the exhaust gas recirculation can be assumed. This leads to function block 46.3 , while a symmetrical exhaust gas extraction from the two exhaust banks 11.1 . 11.2 an intact exhaust gas recirculation 20.1 . 20.2 signaled and to function block 47.3 leads. The logic only judges the relation of the in the (NOx) storage catalysts 12.1 . 12.2 stored NOx quantities on exhaust bank 11.1 and exhaust bank 11.2 and thus has the advantage of being independent of the uncertainty of the modeling of the absolute amounts of stored NOx, ie of NOx_B1 and NOx_B2. The amount of the necessary difference between the amounts of NOx NOx_Reg_B1 and NOx_Reg_B2, which leads to a fault message can be specified by a minimum value, as due to measurement uncertainties even with intact exhaust gas recirculation 20.1 . 20.2 from a difference of the specific values NOx_Reg_B1 and NOx_Reg_B2 is assumed. In the case of a determined error difference between NOx_Reg_B1 and NOx_Reg_B2, the engine control, not shown, can output a corresponding error message or an adaptation of the exhaust gas recirculation valve concerned 22.1 . 22.2 carry out. It is in case of a fault in an exhaust gas recirculation 20.1 . 20.2 in general, assume a reduced amount of recirculated exhaust gas, that is, the disturbance is in the exhaust gas recirculation 20.1 . 20.2 from the exhaust bank 11.1 . 11.2 with the smaller amount of in the (NOx) storage catalyst 12.1 . 12.2 stored NOx.

Claims (15)

Method for adapting exhaust gas recirculation systems and / or for the diagnosis of exhaust gas recirculation ( 20 . 20.1 . 20.2 ) in internal combustion engines ( 30 ) with single or multi-flow exhaust systems ( 10 ), wherein at least part of the exhaust banks ( 11 . 11.1 . 11.2 ) each an exhaust gas recirculation line ( 21 . 21.1 . 21.2 ) each with an exhaust gas recirculation valve ( 13 . 13.1 . 13.2 ) is assigned, via which at least a portion of the exhaust gas to a suction pipe ( 31 ), and wherein each exhaust bank ( 11 . 11.1 . 11.2 ) with a storage catalyst ( 12 . 12.1 . 12.2 ) for receiving at least one exhaust gas constituent and with a downstream exhaust gas sensor ( 13 . 13.1 . 13.2 ), on the basis of which measuring signals a filled storage catalytic converter ( 12 . 12.1 . 12.2 ), characterized in that the storage capacity of at least one storage catalytic converter ( 12 . 12.1 . 12.2 ) during a first phase of operation with open exhaust gas recirculation ( 20 . 20.1 . 20.2 ) and during a second operating phase with at least largely closed exhaust gas recirculation ( 20 . 20.1 . 20.2 ) and that, in the case of differences between the specific storage capacities, a fault in the exhaust gas recirculation ( 20 . 20.1 . 20.2 ) is closed. Method according to Claim 1, characterized in that the storage capacity of the storage catalytic converter ( 12 . 12.1 . 12.2 ) taking into account the operating conditions of the internal combustion engine ( 30 ) is modeled and / or that the storage capacity is determined metrologically. A method according to claim 1 or 2, characterized in that a fault in the exhaust gas recirculation ( 20 . 20.1 . 20.2 ) is closed when the difference between the determined storage capacities exceeds a predetermined limit. Method according to one of claims 1 to 3, characterized in that a first determination of the storage capacity during a storage phase of the storage catalytic converter ( 12 . 12.1 . 12.2 ) until the beginning of a regeneration phase and a second determination of the storage capacity during a regeneration phase of the storage catalytic converter ( 12 . 12.1 . 12.2 ) respectively. Method according to one of claims 1 to 4, characterized in that in double-flow exhaust systems ( 10 ) with a first and a second exhaust bank ( 11.1 . 11.2 ) the storage capacities of the respective storage catalysts ( 12.1 . 12.2 ) in a first operating phase with open exhaust gas recirculation ( 20.1 . 20.2 ) and in a second operating phase with at least largely closed exhaust gas recirculation ( 20.1 . 20.2 ). A method according to claim 5, characterized in that a fault in at least one exhaust gas recirculation ( 20.1 . 20.2 ) is closed when, for a storage catalytic converter ( 12.1 . 12.2 ) in an exhaust gas bank ( 11.1 . 11.2 ) in the first operating phase, a lower storage capacity and in the second operating phase, an approximately equal or greater storage capacity than in the storage catalyst ( 12.1 . 12.2 ) in the other exhaust bank ( 11.1 . 11.2 ), wherein a reduced exhaust gas recirculation from the exhaust gas bank ( 11.1 . 11.2 ) is closed, in which in the first phase of operation with open exhaust gas recirculation ( 20.1 . 20.2 ) a lower and in the second phase of operation with largely closed exhaust gas recirculation ( 20.1 . 20.2 ) an approximately equal or greater storage capacity of the storage catalyst ( 12.1 . 12.2 ) than at the other exhaust bank ( 11.1 . 11.2 ) was detected. Method according to one of claims 5 and 6, characterized in that during an operating phase with open exhaust gas recirculation ( 20.1 . 20.2 ) for the storage catalyst ( 12.1 . 12.2 ) a lower storage capacity is assumed, in which a downstream exhaust gas sensor ( 13.1 . 13.2 ) first reaching the maximum storage capacity of the storage catalytic converter ( 12.1 . 12.2 ) detected for the exhaust gas component to be stored. Method according to one of claims 5 to 7, characterized in that the detection of a fault in the exhaust gas recirculation ( 20.1 . 20.2 ) takes place according to an alternative method and the assignment of the disturbance to the respective exhaust gas recirculation ( 20.1 . 20.2 ) an exhaust bank ( 11.1 . 11.2 ) by evaluation of the determined storage capacities of the storage catalysts ( 12.1 . 12.2 ) he follows. Method according to one of claims 1 to 8, characterized in that in internal combustion engines ( 30 ) with at least one NOx storage catalyst ( 12 . 12.1 . 12.2 ) which during lean operating phases of the internal combustion engine ( 30 ) in the NOx storage catalyst ( 12 . 12.1 . 12.2 ) stored amount of nitrogen oxide NOx is determined that during a regeneration phase of the NOx storage catalyst ( 12 . 12.1 . 12.2 ) the stored amount of nitrogen oxide NOx_Reg is determined and that in the case of differences between the specific amounts of nitrogen oxide NOx and NOx_Reg, a fault in the exhaust gas recirculation ( 20 . 20.1 . 20.2 ) is closed. Method according to one of claims 1 to 9, characterized in that a filled NOx storage catalyst based on the measurement signal of the NOx storage catalyst ( 12 . 12.1 . 12.2 ) downstream NOx exhaust gas sensor ( 13 . 13.1 . 13.2 ) is detected that up to this point in the NOx storage catalytic converter ( 12 . 12.1 . 12.2 ) amount of nitrogen oxide NOx is modeled and that in a subsequent regeneration phase on the basis of the regeneration of the NOx storage catalyst ( 12 . 12.1 . 12.2 ) required amount of rich exhaust gas in the NOx storage catalyst ( 12 . 12.1 . 12.2 ) actually stored amount of nitrogen oxide NOx_Reg is determined. Method according to one of claims 1 to 10, characterized in that in double-flow exhaust systems ( 10 ) with a first and a second exhaust bank ( 11.1 . 11.2 ) B1 and B2 for each exhaust bank during the lean operating phases that in the respective NOx storage catalytic converters ( 12.1 . 12.2 Nitrogen oxides NOx_B1 and NOx_B2 are modeled and that during a regeneration phase the stored amounts of nitrogen oxide NOx_Reg_B1 and NOx_Reg_B2 in the respective NOx storage catalysts ( 12.1 . 12.2 ). A method according to claim 11, characterized in that a fault in at least one exhaust gas recirculation ( 20.1 . 20.2 ) is closed when, for a NOx storage catalyst ( 12.1 . 12.2 ) in an exhaust bank during the lean operating phases a lower NOx storage capacity and during the regeneration phase a larger NOx storage capacity than in the NOx storage catalyst ( 12.1 . 12.2 ) in the other exhaust bank ( 11.1 . 11.2 ), wherein a reduced exhaust gas recirculation from the exhaust gas bank ( 11.1 . 11.2 ) is closed, in which in the lean operating phases a lower and in the regeneration phase a larger NOx storage capacity of the NOx storage catalyst ( 12.1 . 12.2 ) than at the other exhaust bank ( 11.1 . 11.2 ) was detected. A method according to claim 11, characterized in that in differences between the specific amounts of nitrogen oxides NOx_B1 and NOx_Reg_B1 and / or differences between the specific amounts of nitrogen oxide NOx_B2 and NOx_Reg_B2 on a fault in the exhaust gas recirculation ( 20.1 . 20.2 ) in the respective exhaust bank ( 11.1 . 11.2 ) B1 and / or B2 is closed. A method according to claim 11, characterized in that at certain amounts of nitrogen oxide NOx_Reg_B1> NOx_B1 and NOx_Reg_B2 ≤ NOx_B2 or NOx_Reg_B1 ≤ NOx_B1 and NOx_Reg_B2> NOx_B2 to a fault in the exhaust gas recirculation ( 20.1 . 20.2 ) is closed. A method according to claim 11, characterized in that at approximately the same specific amounts of nitrogen oxide NOx_B1 and NOx_B2 with simultaneous large difference of the specific amounts of nitrogen oxides NOx_Reg_B1 and NOx_Reg_B2 to a fault in the exhaust gas recirculation ( 20.1 . 20.2 ) is closed.