WO2017194183A1 - Procédé et dispositif de détermination d'une capacité d'accumulation d'oxydes d'azote d'un catalyseur d'un véhicule automobile - Google Patents

Procédé et dispositif de détermination d'une capacité d'accumulation d'oxydes d'azote d'un catalyseur d'un véhicule automobile Download PDF

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Publication number
WO2017194183A1
WO2017194183A1 PCT/EP2017/000543 EP2017000543W WO2017194183A1 WO 2017194183 A1 WO2017194183 A1 WO 2017194183A1 EP 2017000543 W EP2017000543 W EP 2017000543W WO 2017194183 A1 WO2017194183 A1 WO 2017194183A1
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WIPO (PCT)
Prior art keywords
catalyst
nitrogen oxides
nitrogen oxide
nitrogen
exhaust gas
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PCT/EP2017/000543
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German (de)
English (en)
Inventor
Thomas Beckmann
Original Assignee
Daimler Ag
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Filing date
Publication date
Application filed by Daimler Ag filed Critical Daimler Ag
Priority to US16/301,206 priority Critical patent/US20190390583A1/en
Priority to CN201780029207.3A priority patent/CN109072748B/zh
Publication of WO2017194183A1 publication Critical patent/WO2017194183A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842—Nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/101—Three-way catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/18—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being an adsorber or absorber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2370/00—Selection of materials for exhaust purification
    • F01N2370/02—Selection of materials for exhaust purification used in catalytic reactors
    • F01N2370/04—Zeolitic material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F01N2550/02—Catalytic activity of catalytic converters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
    • F01N2900/1402—Exhaust gas composition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
    • F01N2900/1614—NOx amount trapped in catalyst
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the invention relates to a method and a device for determining a nitrogen oxide storage capability of a catalytic converter of a vehicle.
  • a concentration of a nitrogen oxide in the exhaust gas downstream of the catalyst is measured.
  • DE 198 52 240 A1 describes a method for monitoring a NOx storage catalytic converter, in which the NOx storage efficiency of the catalytic converter is determined from the NOx exhaust gas concentration before and after the NOx storage catalytic converter.
  • the NOx exhaust gas concentrations before and after the NOx storage catalyst are converted into NOx mass flows, and from these values, the NOx storage efficiency is determined.
  • the NOx trapping catalyst may be a NOx storage catalyst (NSK) or a diesel oxidation catalyst (DOC). Both the generation of an exotherm and the provision of a fat jump are associated with an additional fuel consumption. Therefore, such measures
  • the frequency of the monitoring events ie the respective investigations of the nitrogen oxide storage capacity of the catalyst, is thus limited. If the NOx storage capability of the catalytic converter is to be ascertained in the context of an on-board diagnosis (OBD), then this diagnosis is only possible at this interval or at the expense of additional fuel consumption if the monitoring events are additionally requested.
  • OBD on-board diagnosis
  • the diagnosis of a DOC using exothermicity is carried out as part of a particle filter regeneration. This is usually done in an interval between 500 kilometers and 1500 kilometers of driving distance traveled by the vehicle. In this form of monitoring, a
  • This form of monitoring provides feedback on the nitrogen oxide storage capacity of the catalyst. From the nitrogen oxide storage capacity of the catalyst can in turn on the performance in terms of reducing the content of
  • Hydrocarbons or carbon monoxide are closed in the exhaust.
  • Object of the present invention is therefore to provide an improved method and an improved device of the type mentioned.
  • the nitrogen oxide storage capacity of a catalytic converter of a vehicle is determined.
  • a concentration of nitrogen oxides in the exhaust gas downstream of the catalyst is measured.
  • a concentration of nitrogen oxides in the exhaust gas is set at which the catalyst absorbs nitrogen oxides.
  • a concentration of nitrogen oxides in the exhaust gas is set at which desorption of the nitrogen oxides from the catalyst takes place.
  • the behavior of the catalyst is taken into account, at least during the desorption of the nitrogen oxides.
  • the storage capacity of the catalyst can be determined qualitatively and indirectly also quantitatively without specially initiated measures which a
  • Nitrogen oxide saturation can be produced in the catalyst with nitrogen oxide storage capability.
  • the maximum storage capacity or stored quantity is dependent on the current NOx partial pressure. By lowering the NOx partial pressure so also the maximum storage capacity or stored amount of nitrogen oxides decreases, and NOx is desorbed. Conversely, by raising the NOx partial pressure, the maximum storage capacity or stored amount of nitrogen oxides increases, and NOx is again absorbed by the catalyst.
  • the nitrogen oxide storage capacity of the catalyst can be deduced in an improved manner.
  • the information regarding the nitrogen oxide storage capability of the catalyst enables a diagnosis of the catalyst with regard to the HC / CO / NOx performance. Furthermore, with the information regarding the nitrogen oxide storage capability of the catalytic converter, the operating strategy of the internal combustion engine or the engine of the vehicle can be optimized for the current state of the exhaust system.
  • the vehicle may be in particular a motor vehicle or a
  • Desulfurization of the catalyst (DeSOx strategy) possible.
  • the catalyst is considered to have a NOx storage capability that varies with the age of the exhaust system or with the age of the catalyst.
  • a concentration of nitrogen oxides in the exhaust gas is set, at which the catalyst absorbs the nitrogen oxides up to a saturation of the catalyst with nitrogen oxides.
  • a concentration of nitrogen oxides in the exhaust gas is set in a plurality of first steps, in which the
  • Catalyst absorbs nitrogen oxides.
  • a concentration of nitrogen oxides in the exhaust gas is set, at which the desorption of the nitrogen oxides takes place from the catalyst.
  • the nitrogen oxide storage capacity of the catalytic converter is concluded here.
  • the respectively absorbed amounts of nitrogen oxides and the respectively desorbed amounts of nitrogen oxides can be accumulated separately from one another. From the absorption amounts and the desorption can then be concluded that the storage capacity of the catalyst with respect to nitrogen oxides.
  • respective first gradients of a temporal course of the concentration of nitrogen oxides in the exhaust gas are determined upstream of the catalytic converter and downstream of the catalytic converter.
  • respective second gradients of a time course of the concentration of nitrogen oxides in the exhaust gas are determined upstream of the catalytic converter and downstream of the catalytic converter. Based on the gradient is based on the nitrogen oxide storage capacity of the catalyst
  • an average value is preferably formed from a plurality of amounts of the first gradients and from a plurality of amounts of the second gradients. Based on the average can then be concluded that the nitrogen oxide storage capacity of the catalyst.
  • a corresponding control device or a control device of the vehicle for determining the nitrogen oxide storage capacity of the catalytic converter such a method can be carried out in a particularly simple and low-effort manner.
  • the nitrogen oxide storage capacity of a passive nitrogen oxide absorber of the vehicle and / or an oxidation catalytic converter of the vehicle and / or a passively operated nitrogen oxide storage catalytic converter of the vehicle is determined.
  • a passive nitrogen oxide absorber PNA
  • the storage or sorption of the nitrogen oxides takes place, for example, in the zeolite material of the passive nitrogen oxide absorber.
  • the nitrogen oxides are not chemically bound. It is therefore not necessary to enrich the air-fuel mixture for reducing chemically bound nitrogen oxides in the course of a chemical reaction. Instead, the passive nitrogen oxide absorber undergoes thermal desorption of the nitrogen oxides.
  • an oxidation catalyst in particular diesel oxidation catalyst (DOC)
  • DOC diesel oxidation catalyst
  • DOC diesel oxidation catalyst
  • zeolites as support materials of the catalytically active
  • Nitrogen oxides take place without the need for enrichment of the air-fuel mixture, ie the setting of an air ratio ⁇ greater than 1, needs to be made.
  • a nitrogen oxide storage catalyst can be operated passively, in which the nitrogen oxides are chemically bonded to a corresponding material of the nitrogen oxide storage catalyst. This chemically bound NOx can also be thermally desorbed, for example by raising the temperature of the passively operated nitrogen oxide storage catalytic converter.
  • the device according to the invention for determining a nitrogen oxide storage capability of a catalytic converter of a vehicle comprises a sensor for measuring a concentration of nitrogen oxides in the exhaust gas downstream of the catalytic converter.
  • the device further comprises a control device, which is designed to set in at least a first step, a concentration of nitrogen oxides in the exhaust gas, wherein the catalyst absorbs nitrogen oxides.
  • the control device is further configured to adjust a concentration of nitrogen oxides in the exhaust gas in at least a second step, in which a desorption of the nitrogen oxides takes place from the catalyst.
  • the control device is designed to take into account the behavior of the catalytic converter, at least during the desorption of the nitrogen oxides, in order to determine the nitrogen oxide storage capability of the catalytic converter.
  • Fig. 1 shows the time course of the nitrogen oxide concentrations upstream of a
  • Fig. 2 shows the time course of the NOx mass flows upstream
  • the exhaust system 10 includes an exhaust line 12, in which a catalyst 14 is arranged, which has a nitrogen oxide storage capability.
  • the catalyst 14 may be
  • the catalytic converter 14 may be followed by a particle filter 16 and / or an SCR catalytic converter 18.
  • the particulate filter 16 may further be designed in particular as an SCR-coated particulate filter 16.
  • nitrogen oxides from the exhaust gas may be mixed with ammonia to form water and
  • Nitrogen be implemented.
  • a metering device 20 By means of a metering device 20
  • an aqueous urea solution are introduced into the exhaust gas line 12, wherein the ammonia is formed from the urea in the exhaust gas.
  • a sensor 22 Downstream of the catalyst 14 and in the present case upstream of the metering device 20, a sensor 22 is arranged in the exhaust line 12, by means of which the Concentration of nitrogen oxides in the exhaust gas can be measured downstream of the catalyst 14.
  • a corresponding curve 24 in FIG. 1 illustrates the time profile of the concentration of nitrogen oxides (NOx) in the exhaust gas downstream of the catalytic converter 14.
  • a further curve 26 in FIG. 1 illustrates the raw nitrogen oxide emission, that is to say
  • the raw NOx emission upstream of the catalyst 14 may be detected by a sensor or determined based on a model.
  • Control device approximately in the form of a control device 28 of the vehicle is used in the present case for determining the nitrogen oxide storage capacity of the catalytic converter 14.
  • desorption of the nitrogen oxides from the catalyst 14 is preferably considered in overrun of the vehicle in order to determine the NOx storage capacity of the catalytic converter 14.
  • the NOx storage capability of the catalytic converter 14 changes with the aging of the exhaust system 10, wherein the nitrogen oxide storage capacity of the catalytic converter 14 usually decreases with increasing age of the exhaust system 10.
  • a first step 30 saturation of the catalyst 14 with nitrogen oxides is produced.
  • the fact that there is an at least substantial saturation of the storage or catalyst 14 can be recognized from the fact that in the time interval of step 30, in which the NOx saturation is established, the raw NOx emissions of the internal combustion engine (curve 26) the content of nitrogen oxides in the exhaust gas downstream of the catalyst 14 (curve 24) are the same.
  • a time 34 plotted on a time axis 32 in FIG. 1 for example by means of the control device 28, an operation of the internal combustion engine or of the engine is set, in which the raw NOx emission is zero. This is advantageous because then the raw emission is known without measurement error. Such a condition occurs
  • overrun operation for example, in overrun operation of the vehicle.
  • the overrun operation can also be assisted by an electric motor of the vehicle, so that load requirements can be met even without an engine assist.
  • the nitrogen oxide concentration in the exhaust gas downstream of the Catalyst 14 (curve 24) is not zero in the period following time 34, but the concentration decreases.
  • the behavior of the catalyst 14 during this desorption of the nitrogen oxides is used to determine the nitrogen oxide storage capacity of the catalyst 14.
  • the prerequisites to be met in this case are that the NOx storage, that is, the catalytic converter 14, is saturated and that the temperatures before the catalytic converter 14 and downstream of the catalytic converter 14 neither rise nor fall sharply. It is advantageous if the temperature gradient is not too large. This is due to the fact that the NOx storage capacity of the catalytic converter 14 is generally also dependent on the temperature. At at least substantially constant temperature, therefore, the desired effect of the desorption is not superimposed too strongly by the temperature effect.
  • exhaust gas recirculation in particular high-pressure exhaust gas recirculation
  • the exhaust gas recirculation should advantageously be dispensed with in overrun operation. Otherwise it will circulate
  • the exhaust gas mass flow through the catalytic converter 14 can be changed by suitable engine measures.
  • the exhaust gas mass flow can be reduced in order to increase the measurement accuracy when detecting the nitrogen oxide concentration by means of the sensor 22.
  • the changing of the exhaust gas mass flow can be carried out, for example, by means of a corresponding setting of the engine speed and / or by actuating a throttle valve and / or by changing a high-pressure exhaust gas recirculation rate or low-pressure exhaust gas recirculation rate.
  • the nitrogen oxide concentration behind the catalytic converter 14 is preferably measured with the help of the nitrogen oxide sensor 22. If the catalytic converter 14 still has a nitrogen oxide storage capacity, then the nitrogen oxide concentration downstream of the catalytic converter 14, ie downstream of the catalytic converter 14, decreases more slowly than in front of the catalytic converter 14, that is to say upstream of the catalytic converter 14. Thus, it is desorbed during overrun operation of nitrogen oxides from the catalyst 14 instead. Preferably, the desorbed amount of nitrogen oxides with a modeled, so expected nitrogen oxide amount is adjusted. Such a model can thus indicate how the nitrogen oxide concentration in the exhaust gas downstream of the catalytic converter 1 should decrease from zero in the presence of a raw NOx emission. The model can thus take into account, for example, the decay of the measurements of the sensor 22 or the presence of regions of the exhaust system 10 which are less well flowed through by exhaust gas, which accordingly slows down the decrease in the exhaust gas
  • Nitrogen concentration downstream of the catalyst 14 can lead. Furthermore, the aging of the exhaust system 10, in particular of the model, is preferred in the model
  • Nitrogen decay curve deviates from the target NOx decay curve.
  • This variant is based on the finding that by lowering and raising the NOx partial pressure in the region of the catalyst 14 continuously small
  • FIG. 2 plots, on a first ordinate 38, the NOx mass flow upstream or downstream of the catalyst 14 as a function of time t, which is indicated on the time axis 32.
  • a first curve 40 accordingly illustrates the NOx mass flow upstream of the catalytic converter 14 and a second curve 42 the NOx mass flow downstream of the catalytic converter 14.
  • the emissions upstream of the catalytic converter 14 are higher than the emissions downstream of the catalytic converter 14 Accordingly, it comes here to an absorption of nitrogen oxides.
  • a desorption of the nitrogen oxides from the catalyst 14 takes place in a plurality of second steps 46. This is the case when the emissions downstream of the catalyst 14 are higher than the emissions
  • the time t is in turn plotted on the time axis 32 in the second graph in FIG.
  • This difference 54 is compared with a target value, and based on the comparison, the nitrogen oxide storage capability of the catalyst 14 is concluded.
  • the NOx concentrations are known before the catalyst 14 and after the catalyst 14 with low fault tolerances. If there are measurement errors, these errors should tend in the same direction before the catalyst 14 and after the catalyst 14. The presence of errors can be detected, for example, by observing conditions in which no storage of nitrogen oxides in the catalyst 14 occurs. Then, the measured values upstream of the catalytic converter 14 and downstream of the catalytic converter 14 should correspond to one another or the modeled value upstream of the catalytic converter 14 should correspond to the value measured downstream of the catalytic converter 14 with the sensor 22. Furthermore, the nitrogen oxide concentrations should be present at the right time. For this the values of the
  • the nitrogen oxide absorption and the nitrogen oxide desorption of the catalyst 14 are continuously determined. This is done by subtracting the nitrogen oxide mass flows before the catalyst 14 and the nitrogen oxide mass flows after the catalyst 14 from each other.
  • the NOx sensor 22 is provided for determining the NOx mass flow downstream of the catalyst 14. For the determination of the NOx mass flow upstream of the catalyst 14 may also be
  • Emission model can be used.
  • the nitrogen oxide absorption mass flows and the nitrogen oxide desorption mass flows are accumulated or added up separately. Furthermore, the raw nitrogen oxide emission of the internal combustion engine is accumulated.
  • a characteristic value is preferably determined which is representative of the averaged nitrogen oxide gradient upstream of the catalytic converter 14, which therefore indicates the average gradient of a curve representing the raw nitrogen oxide emissions of the internal combustion engine. Such a characteristic value can be calculated or specified in particular in ppm N o x per second. A high characteristic value is accordingly strong
  • Nitrogen oxides and the total desorbed amount of nitrogen oxides depending on
  • the nitrogen oxide storage capacity of the catalyst 14 typically increases as the temperature of the catalyst 14 drops. Accordingly, the accumulated amount of absorbed nitrogen oxide is larger than the accumulated amount of desorbed nitrogen oxide. Conversely, an increasing temperature of the catalyst 14 causes the accumulated desorption to be generally greater than the accumulated absorption.
  • the difference 54 present at the end of the considered evaluation period is compared with an expected, modeled difference. If the difference 54 is greater or less than the expected difference, this may indicate a drift of the emission model or the sensor 22. This can be compensated by a corresponding new calibration of the emission model or the sensor 22. If none such drift is present, the NOx storage capability of the catalyst 14 can be deduced based on the difference 54.
  • the diagnosis is preferably carried out considering a past time interval. This is because it can be ensured that predetermined boundary conditions have been present within the time interval. As one of these boundary conditions can be provided that the NOx storage, ie the catalyst 14, was sufficiently saturated with nitrogen oxides in the considered, past time interval. For example, a saturation of at least 80 percent may be provided. Furthermore, it is preferable to consider a time interval in which the temperature was sufficiently stable and within an allowable range. For this purpose, it can be considered, for example, whether, with a temperature change of the exhaust gas upstream of the catalytic converter 14, no or at most a slight temperature change has occurred downstream of the catalytic converter 14. The specification of this boundary condition is in turn based on the temperature dependence of the desorption.
  • the characteristic value for the nitrogen oxide gradient upstream of the catalytic converter 14 was within a predetermined range. This area should not be too small. Otherwise, namely the
  • the height of the accumulated absorption and the amount of accumulated desorption are compared with the modeled absorption and the modeled desorption. If the difference between the accumulated absorption amount and the accumulated desorption amount is less than the modeled difference or the modeled quantity, then this is an indication of a reduced nitrogen oxide storage capacity of the catalyst 14. From the absorption amounts and the
  • Desorptionsmengen can therefore be closed by a model on the absolute nitrogen oxide storage capacity of the catalyst 14.
  • the model preferably includes a setpoint value for the absorption amount and a setpoint value for the desorption amount for the given boundary conditions. These Setpoint values are a function of the temperature, the characteristic value of the NOx gradient, the exhaust gas mass flow and the sum of the raw emissions of nitrogen oxide.
  • the currently modeled nitrogen oxide storage capacity of the catalyst 14 may be corrected upwards or downwards if the measured absorption amount and the measured desorption amount deviate from the target absorption amount and the target desorption amount.
  • a first curve 58 represents the course of the raw emission as a function of time
  • a second curve 60 shows the concentration of the nitrogen oxides in the exhaust gas downstream of the
  • Catalyst 14 which is detected by the sensor 22. Again, one makes use of the effect that by lowering and lifting or by
  • the absolute nitrogen oxide storage capacity of the catalytic converter 14 can be concluded by means of a model.
  • the following procedure is used to determine the characteristic value for the NOx gradient.
  • a signal noise of the nitrogen oxide sensor 22 after the catalyst 14 and the (optional) nitrogen oxide sensor upstream of the catalyst 14 is averaged out.
  • Nitrogen oxide concentration upstream of the catalyst 14 is determined, for example, in pprri NOx per second. The basis for this is a (not shown here)
  • the gradient or the slope of the nitrogen oxide concentration downstream of the catalyst 14 is preferably determined in ppm N ox per second. The basis for this is the nitrogen oxide sensor 22.
  • the mean value is formed from the amounts of the nitrogen oxide gradients upstream of the catalytic converter 14 and downstream of the catalytic converter 14. This mean value is a characteristic which is representative of the nitrogen oxide gradient.
  • the diagnosis is preferably carried out on a past time interval.
  • the NOx storage or the catalytic converter 14 was sufficiently saturated with nitrogen oxides in the past time interval.
  • the exhaust gas temperature in the past time interval was sufficiently stable and in the permitted range.
  • the characteristic value for the nitrogen oxide gradient upstream of the catalytic converter 14 was preferably within a predetermined range. If this range is too small, the tolerances and noise of the sensors are too dominant. If the characteristic value is too large, however, the tolerances of the emission model and the tolerances of the sensors become too large.
  • the absolute nitrogen oxide storage capacity of the catalytic converter 14 can be deduced from a model.
  • the model preferably has a desired value for the characteristic value of the nitrogen oxide gradient downstream of the catalyst 14 in the given period. However, this is a function of the temperature,
  • the knowledge about the nitrogen oxide storage capacity of the catalytic converter 14 can be used for the operation of the exhaust system 10. For example, can be adjusted via the engine control, the raw nitrogen oxide emissions of the engine. Furthermore, a fat jump dosing strategy and / or a urea dosing strategy can be adapted, or heating measures of the exhaust gas can be made.
  • From the storage capacity of the catalyst 14 may further on the current performance of the catalyst 14 in terms of reducing the content of
  • HC Hydrocarbons
  • CO carbon monoxide
  • NOx nitrogen oxides

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Materials Engineering (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

L'invention concerne un procédé de détermination d'une capacité d'accumulation d'oxydes d'azote d'un catalyseur (14) d'un véhicule, procédé selon lequel une concentration en oxydes d'azote dans les gaz d'échappement est mesurée en aval du catalyseur (14). Dans au mois une première étape (30), une concentration en oxydes d'azote dans les gaz d'échappement, à laquelle le catalyseur (14) absorbe des oxydes d'azote, est réglée. Dans au moins une deuxième étapes (36), une concentration en oxydes d'azote dans les gaz d'échappement, à laquelle une désorption des oxydes d'azote à partir du catalyseur (14) a lieu, est réglée. Afin de déterminer la capacité d'accumulation d'oxydes d'azote du catalyseur (14), le comportement du catalyseur (14) au moins lors de la désorption des oxydes d'azote est pris en compte. L'invention concerne en outre un dispositif de détermination d'une capacité d'accumulation d'oxydes d'azote d'un catalyseur (14) d'un véhicule.
PCT/EP2017/000543 2016-05-13 2017-05-02 Procédé et dispositif de détermination d'une capacité d'accumulation d'oxydes d'azote d'un catalyseur d'un véhicule automobile WO2017194183A1 (fr)

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US16/301,206 US20190390583A1 (en) 2016-05-13 2017-05-02 Method and Device to Determine the Nitrogen Oxide-Storage Capability of a Catalytic Converter of a Vehicle
CN201780029207.3A CN109072748B (zh) 2016-05-13 2017-05-02 确定车辆催化转化器的氮氧化物-存储能力的方法和装置

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DE102016005968.0A DE102016005968A1 (de) 2016-05-13 2016-05-13 Verfahren und Vorrichtung zum Ermitteln einer Stickoxid-Speicherfähigkeit eines Katalysators eines Fahrzeugs

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US20190390583A1 (en) 2019-12-26

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