US20040250531A1 - Method for estimating the degradation of the trapping capacity of NOx-Trap type catalytic converter - Google Patents
Method for estimating the degradation of the trapping capacity of NOx-Trap type catalytic converter Download PDFInfo
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- US20040250531A1 US20040250531A1 US10/800,416 US80041604A US2004250531A1 US 20040250531 A1 US20040250531 A1 US 20040250531A1 US 80041604 A US80041604 A US 80041604A US 2004250531 A1 US2004250531 A1 US 2004250531A1
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- nox
- catalytic converter
- regeneration process
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- trap catalytic
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- 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
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- 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
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
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- 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
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
- F01N11/007—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
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- 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
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
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- 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
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/021—Introducing corrections for particular conditions exterior to the engine
- F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
- F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
- F02D41/0275—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a NOx trap or adsorbent
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- 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
- F01N2550/03—Monitoring or diagnosing the deterioration of exhaust systems of sorbing activity of adsorbents or absorbents
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- 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
- F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
- F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
- F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
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- 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
- F01N2900/04—Methods of control or diagnosing
- F01N2900/0421—Methods of control or diagnosing using an increment counter when a predetermined event occurs
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- 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
- F01N2900/04—Methods of control or diagnosing
- F01N2900/0422—Methods of control or diagnosing measuring the elapsed time
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/08—Exhaust gas treatment apparatus parameters
- F02D2200/0808—NOx storage capacity, i.e. maximum amount of NOx that can be stored on NOx trap
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/08—Exhaust gas treatment apparatus parameters
- F02D2200/0811—NOx storage efficiency
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- 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
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- 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
- Y02T10/40—Engine management systems
Definitions
- the present invention relates to a method for estimating the degradation of the trapping capacity of a NOx-Trap type catalytic converter.
- a direct injection petrol engine comprises an exhaust manifold, which communicates with the cylinders by means of the respective exhaust valves and terminates in an exhaust pipe equipped with a precatalytic converter capable of promoting the conversion of the NO groups produced during combustion into NO 2 and a subsequent NOx-Trap catalytic converter capable of trapping the NO x groups and so preventing their release into the atmosphere.
- the NOx-Trap catalytic converter traps within itself both the NO x groups produced during combustion and the sulfur (in the form of SO x ) that is contained in the fuel and is released during combustion; moreover, the NOx-Trap catalytic converter itself has a limited trapping capacity (generally of between 3 and 5 grams) and when said trapping capacity is exhausted, the NOx-Trap catalytic converter must be cleaned by a regeneration process.
- FIG. 1 denotes the overall internal combustion engine equipped with four cylinders 2 (only one of which is shown in FIG. 1), each of which is connected to an intake manifold 3 via at least one respective intake valve 4 and to an exhaust manifold 5 via at least one respective exhaust valve 6 .
- the intake manifold 3 receives fresh air (i.e., air originating from the outside environment) via a throttle valve 7 that is adjustable between a closed position and a maximally open position.
- Petrol is injected directly into each cylinder 2 by a respective injector 8 .
- an exhaust pipe 9 which comprises a catalytic preconverter 10 and a subsequent NOx-Trap catalytic converter 11 ; inside the exhaust pipe 9 there is installed a UEGO probe 12 , which is arranged upstream from the catalytic preconverter 10 and is capable of detecting the quantity of oxygen present in the exhaust gases entering the catalytic preconverter 10 , a temperature sensor 13 , which is arranged between the catalytic preconverter 10 and NOx-Trap catalytic converter 11 and is capable of detecting the temperature of the gases entering the NOx-Trap catalytic converter 11 , and a multisensor 14 , which is arranged downstream from the NOx-Trap catalytic converter 11 and is capable of detecting either the presence of NO x groups (nitrogenous group sensor) or the quantity of oxygen present relative to stoichiometric conditions (lambda probe) in the exhaust gases leaving the NOx-Trap catalytic converter 11 (i.e.
- the engine 1 furthermore comprises a control unit 15 which, inter alia, on each cycle controls the throttle valve 7 and the injector 8 to fill the cylinder 2 with a quantity of combustion agent (fresh air) and fuel in a specific ratio as a function of the operating conditions of the engine 1 and as a function of the commands received from the driver; in particular, the control unit 15 is capable of causing the engine 1 to operate by combustion with a lean mixture and stratified charge.
- the control unit 15 is connected to the UEGO probe 12 , the temperature sensor 13 and the multisensor 14 .
- the total mass of NO x groups produced during combustion is much greater than the mass of sulfur released during combustion, and moreover the regeneration process to remove NO x groups (a few seconds of rich combustion of the engine) is much shorter than the regeneration process to remove sulfur (indicatively 30-60 seconds of rich combustion combined with an internal temperature in the NOx-Trap catalytic converter 11 that is very much higher than the normal operating temperature).
- the regeneration process to remove NO x groups is normally carried out every 45-75 seconds of operation of the engine 1
- the regeneration process to remove sulfur also known as the desulfation process
- the control unit 15 estimates the quantity of NO x groups stored in the NOx-Trap catalytic converter 11 ; when said quantity of stored NO x groups exceeds a predetermined threshold, the control unit 15 triggers performance of the NO x regeneration process.
- the NO x regeneration process is of a predetermined duration (stored in the memory 16 ) such that the NO x regeneration process is performed only for the time required to remove the NO x groups stored in the NOx-Trap catalytic converter 11 .
- the control unit 15 monitors the signal from the multisensor 14 ; in particular, if no transition in the signal from the multisensor 14 from lean to rich is detected during the NO x regeneration process, then it is assumed that the actual duration of the NO x regeneration process matches the predetermined duration and that thus the storage capacity C of the NOx-Trap catalytic converter 11 is unchanged whereas, if a transition in the signal from the multisensor 14 from lean to rich is detected during the NO x regeneration process, then the actual duration of the NO x regeneration process was less than the predetermined duration and thus the NO x storage capacity C has clearly diminished.
- the signal from the multisensor 14 is significant because, while the reduction process of the NO x groups stored in the NOx-Trap catalytic converter 11 is under way, there is an excess of oxygen (relative to the stoichiometric value) in the exhaust gases downstream from the NOx-Trap catalytic converter 11 , said excess arising from the reduction of the NO x groups, whereas once the reduction process of the NO x groups stored in the NOx-Trap catalytic converter 11 is complete, there is a deficit of oxygen (relative to the stoichiometric value) in the exhaust gases downstream from the NOx-Trap catalytic converter 11 because a rich mixture is supplied to the cylinders 2 during the regeneration process.
- control unit 15 If, during the NO x regeneration process of the NOx-Trap catalytic converter 11 , the control unit 15 detects the above-described anomalous transition in the signal from the multisensor 14 , then the control unit 15 attempts to determine the cause that led to the degradation of the trapping capacity C of the NOx-Trap catalytic converter 11 and thus attempts, if possible, to remedy such degradation.
- control unit 15 when the control unit 15 detects the anomalous transition in the signal from the multisensor 14 , then the control unit 15 increases the operating temperature (indicatively by a step of 20-40° C.) of the NOx-Trap catalytic converter 11 by acting in known manner on the control of the throttle valve 7 and the injector 8 and awaits performance of the subsequent NO x regeneration process; if, during the subsequent NO x regeneration process, the control unit 15 again detects the anomalous transition in the signal from the multisensor 14 , then the control unit 15 further increases the operating temperature (indicatively by a step of 20-40° C.) of the NOx-Trap catalytic converter 11 and awaits performance of the subsequent NO x regeneration process.
- Said process of increasing the operating temperature of the NOx-Trap catalytic converter 11 is continued in cycles not until the operating temperature of the NOx-Trap catalytic converter 11 reaches a predetermined limiting value, but instead until the control unit 15 ceases to detect the anomalous transition in the signal from the multisensor 14 ; in this latter case, i.e., if the increase in the operating temperature of the NOx-Trap catalytic converter 11 has led to the disappearance of the anomalous transition in the signal from the multisensor 14 , then the control unit 15 increases the minimum value of the operating temperature of the NOx-Trap catalytic converter 11 stored in the memory 16 by a predetermined quantity because the reduction in the trapping capacity C of the NOx-Trap catalytic converter 11 is essentially due to thermal degradation and can be at least partly offset by increasing the operating temperature of the NOx-Trap catalytic converter 11 . Obviously, the control unit 15 does not increase the minimum value of the operating temperature of the NOx-Trap catalytic converter 11 beyond a predetermined threshold value
- the control unit 15 increments the temperature value of the NOx-Trap catalytic converter 11 and decrements the average value for ratio used during future desulfation processes because the reduction in the trapping capacity C of the NOx-Trap catalytic converter 11 is essentially due to the formation of particularly tenacious sulfur crystals.
- the control unit 15 does not increase the temperature value for the NOx-Trap catalytic converter 11 nor does it decrement the average value for ratio used during desulfation processes beyond the respective predetermined thresholds.
Abstract
A method for estimating the degradation of the trapping capacity of a NOx-Trap catalytic converter, in accordance with which, if the actual duration of a first NOx regeneration process is equal to the predetermined duration, it is assumed that the trapping capacity is unchanged; if the actual duration of the first NOx regeneration process is less than the predetermined duration, at least one corrective action is performed in order to attempt to counteract the degeneration of the NOx-Trap catalytic converter, a subsequent NOx regeneration process is performed, if the actual duration of the subsequent NOx regeneration process is equal to the predetermined duration, then new characteristic operating parameters for the corrective action are used for the subsequent life of the NOx-Trap catalytic converter whereas, if the actual duration of the subsequent NOx regeneration process is less than the predetermined duration, the estimated trapping capacity of the NOx-Trap catalytic converter is reduced.
Description
- This application claims priority from Italian patent application No. BO2003A filed on Mar. 13, 2003, which is incorporated herein by reference.
- The present invention relates to a method for estimating the degradation of the trapping capacity of a NOx-Trap type catalytic converter.
- The present invention is advantageously applied to an internal combustion automotive engine supplied with fuel by direct injection of petrol into the cylinders and having combustion with a lean mixture and stratified charge, to which the following description will make explicit reference without thereby restricting the general scope.
- A direct injection petrol engine comprises an exhaust manifold, which communicates with the cylinders by means of the respective exhaust valves and terminates in an exhaust pipe equipped with a precatalytic converter capable of promoting the conversion of the NO groups produced during combustion into NO2 and a subsequent NOx-Trap catalytic converter capable of trapping the NOx groups and so preventing their release into the atmosphere. The NOx-Trap catalytic converter traps within itself both the NOx groups produced during combustion and the sulfur (in the form of SOx) that is contained in the fuel and is released during combustion; moreover, the NOx-Trap catalytic converter itself has a limited trapping capacity (generally of between 3 and 5 grams) and when said trapping capacity is exhausted, the NOx-Trap catalytic converter must be cleaned by a regeneration process.
- The total mass of NOx groups produced during combustion is much greater than the mass of sulfur released during combustion; moreover the regeneration process to remove NOx groups (a few seconds of rich combustion) is much shorter than the regeneration process to remove sulfur (of the order of 30-60 seconds of rich combustion combined with an internal temperature in the catalytic converter that is very much higher than the normal operating temperature). For the reasons stated above, the regeneration process to remove NOx groups is normally carried out every 45-75 seconds of engine operation, whereas the regeneration process to remove sulfur is normally carried out every 6-12 hours of engine operation.
- The regeneration processes are scheduled by a central control unit using a storage model for the NOx-Trap catalytic converter, said model being based on a knowledge of the estimated trapping capacity of the NOx-Trap catalytic converter, and using a model of the production of NOx and SOx group by the engine. Each time NOx regeneration of the NOx-Trap catalytic converter is performed, the central control unit checks, using the signal from a lambda probe and/or a NOx probe provided downstream from the NOx-Trap catalytic converter, whether the actual duration of the NOx regeneration process is less than a predetermined value on the basis of the current model; if this is the case, i.e. if the actual duration of the NOx regeneration process is less than the predetermined value, it is clear that the NOx-Trap catalytic converter has trapped a smaller quantity of NOx than predicted and the central control unit accordingly assumes that said phenomenon is due to degradation of the NOx-Trap catalytic converter and reduces the estimate of the trapping capacity of the NOx-Trap catalytic converter used in the storage model for the NOx-Trap catalytic converter.
- However, experimental trials have revealed that, when the above-described method is used, there is a tendency to underestimate the actual trapping capacity of the NOx-Trap catalytic converter, with a consequent increase in fuel consumption (and thus in the level of atmospheric emissions), due to the fact that underestimating the actual trapping capacity of the NOx-Trap catalytic converter results in NOx regeneration processes being carried out more frequently.
- The object of the present invention is to provide a method for estimating the degradation of the trapping capacity of a NOx-Trap type catalytic converter, which method does not have the above-described disadvantages and, in particular, is simple and economical to implement.
- The present invention provides a method for estimating the degradation of the trapping capacity of a NOx-Trap type catalytic converter as defined in claim1 and, preferably, in any one of the subsequent claims directly or indirectly subordinate to claim 1.
- The present invention will now be described with reference to the attached drawing, which illustrates a non-limiting embodiment; in particular, the attached figure is a schematic view of an internal combustion engine, which is controlled by a control unit that implements the estimation method provided by the present invention.
- In the attached FIG. 1 denotes the overall internal combustion engine equipped with four cylinders2 (only one of which is shown in FIG. 1), each of which is connected to an
intake manifold 3 via at least onerespective intake valve 4 and to anexhaust manifold 5 via at least one respective exhaust valve 6. Theintake manifold 3 receives fresh air (i.e., air originating from the outside environment) via athrottle valve 7 that is adjustable between a closed position and a maximally open position. Petrol is injected directly into eachcylinder 2 by arespective injector 8. - From the
exhaust manifold 5 there leaves anexhaust pipe 9, which comprises acatalytic preconverter 10 and a subsequent NOx-Trapcatalytic converter 11; inside theexhaust pipe 9 there is installed a UEGOprobe 12, which is arranged upstream from thecatalytic preconverter 10 and is capable of detecting the quantity of oxygen present in the exhaust gases entering thecatalytic preconverter 10, atemperature sensor 13, which is arranged between thecatalytic preconverter 10 and NOx-Trapcatalytic converter 11 and is capable of detecting the temperature of the gases entering the NOx-Trapcatalytic converter 11, and amultisensor 14, which is arranged downstream from the NOx-Trapcatalytic converter 11 and is capable of detecting either the presence of NOx groups (nitrogenous group sensor) or the quantity of oxygen present relative to stoichiometric conditions (lambda probe) in the exhaust gases leaving the NOx-Trap catalytic converter 11 (i.e., in the exhaust gases released from theexhaust pipe 9 into the atmosphere). - The engine1 furthermore comprises a
control unit 15 which, inter alia, on each cycle controls thethrottle valve 7 and theinjector 8 to fill thecylinder 2 with a quantity of combustion agent (fresh air) and fuel in a specific ratio as a function of the operating conditions of the engine 1 and as a function of the commands received from the driver; in particular, thecontrol unit 15 is capable of causing the engine 1 to operate by combustion with a lean mixture and stratified charge. In order to allow thecontrol unit 15 to capture the data required for correct operation thereof, thecontrol unit 15 is connected to the UEGOprobe 12, thetemperature sensor 13 and themultisensor 14. - In service, the NOx-
Trap catalytic converter 11 stores either the NOx groups produced during combustion or the sulfur (in the form of SOx) contained in the fuel and released during combustion, in order to prevent said constituents from being released directly into the atmosphere. The NOx-Trapcatalytic converter 11 has a limited trapping capacity C for NOx groups and sulfur (normally amounting to 4 grams) and when said trapping capacity C is exhausted the NOx-Trapcatalytic converter 11 must be cleaned by means of a regeneration process. The total mass of NOx groups produced during combustion is much greater than the mass of sulfur released during combustion, and moreover the regeneration process to remove NOx groups (a few seconds of rich combustion of the engine) is much shorter than the regeneration process to remove sulfur (indicatively 30-60 seconds of rich combustion combined with an internal temperature in the NOx-Trapcatalytic converter 11 that is very much higher than the normal operating temperature). For the reasons stated above, the regeneration process to remove NOx groups is normally carried out every 45-75 seconds of operation of the engine 1, whereas the regeneration process to remove sulfur (also known as the desulfation process) is normally carried out every 6-12 hours of operation of the engine 1. - The regeneration processes are scheduled by the
central control unit 15 using a storage model for the NOx-Trapcatalytic converter 11, said model being stored in amemory 16 and based on a knowledge of the estimated trapping capacity C of the NOx-Trapcatalytic converter 11, and using a model of the production of NOx and SOx groups by the engine 1, said model being stored in thememory 16. In particular, the quantity of NOx produced by the engine 1 is obtained in known manner by thecontrol unit 15 using maps that state the specific quantity (i.e., the quantity per unit of fuel injected into the cylinders 2) of NOx and SOx groups produced by the engine 1 as a function of engine status (typically as a function of engine speed and as a function of delivered torque). As is known, the above-mentioned models are determined by means of a theoretical analysis of the systems and by means of a series of laboratory tests carried out on the engine 1 equipped with a series of auxiliary measurement sensors, which are capable of providing an instantaneous and accurate measurement of all the parameters involved in the operation of the engine 1 itself. - During normal operation of the engine1 and using the storage model for the NOx-Trap
catalytic converter 11, thecontrol unit 15 estimates the quantity of NOx groups stored in the NOx-Trapcatalytic converter 11; when said quantity of stored NOx groups exceeds a predetermined threshold, thecontrol unit 15 triggers performance of the NOx regeneration process. The NOx regeneration process is of a predetermined duration (stored in the memory 16) such that the NOx regeneration process is performed only for the time required to remove the NOx groups stored in the NOx-Trapcatalytic converter 11. - During the NOx regeneration process of the NOx-Trap
catalytic converter 11, thecontrol unit 15 monitors the signal from themultisensor 14; in particular, if no transition in the signal from themultisensor 14 from lean to rich is detected during the NOx regeneration process, then it is assumed that the actual duration of the NOx regeneration process matches the predetermined duration and that thus the storage capacity C of the NOx-Trapcatalytic converter 11 is unchanged whereas, if a transition in the signal from themultisensor 14 from lean to rich is detected during the NOx regeneration process, then the actual duration of the NOx regeneration process was less than the predetermined duration and thus the NOx storage capacity C has clearly diminished. The signal from themultisensor 14 is significant because, while the reduction process of the NOx groups stored in the NOx-Trapcatalytic converter 11 is under way, there is an excess of oxygen (relative to the stoichiometric value) in the exhaust gases downstream from the NOx-Trapcatalytic converter 11, said excess arising from the reduction of the NOx groups, whereas once the reduction process of the NOx groups stored in the NOx-Trapcatalytic converter 11 is complete, there is a deficit of oxygen (relative to the stoichiometric value) in the exhaust gases downstream from the NOx-Trapcatalytic converter 11 because a rich mixture is supplied to thecylinders 2 during the regeneration process. It is clear from the above description that the signal from themultisensor 14 can also be used for estimating the actual duration of a NOx regeneration process, because, if no transition in the signal from themultisensor 14 from lean to rich is detected during the NOx regeneration process, then it is assumed that the actual value of the duration of the NOx regeneration process matches the predicted value whereas, if a transition in the signal from themultisensor 14 from lean to rich is detected during the NOx regeneration process, then the actual value of the duration of the NOx regeneration process is less than the calculated value and is equal to the period of time that has elapsed between the moment at which the regeneration process was initiated and the moment at which the transition in the signal from themultisensor 14 occurred. - If, during the NOx regeneration process of the NOx-Trap
catalytic converter 11, thecontrol unit 15 detects the above-described anomalous transition in the signal from themultisensor 14, then thecontrol unit 15 attempts to determine the cause that led to the degradation of the trapping capacity C of the NOx-Trapcatalytic converter 11 and thus attempts, if possible, to remedy such degradation. In particular, when thecontrol unit 15 detects the anomalous transition in the signal from themultisensor 14, then thecontrol unit 15 increases the operating temperature (indicatively by a step of 20-40° C.) of the NOx-Trapcatalytic converter 11 by acting in known manner on the control of thethrottle valve 7 and theinjector 8 and awaits performance of the subsequent NOx regeneration process; if, during the subsequent NOx regeneration process, thecontrol unit 15 again detects the anomalous transition in the signal from themultisensor 14, then thecontrol unit 15 further increases the operating temperature (indicatively by a step of 20-40° C.) of the NOx-Trapcatalytic converter 11 and awaits performance of the subsequent NOx regeneration process. Said process of increasing the operating temperature of the NOx-Trapcatalytic converter 11 is continued in cycles not until the operating temperature of the NOx-Trapcatalytic converter 11 reaches a predetermined limiting value, but instead until thecontrol unit 15 ceases to detect the anomalous transition in the signal from themultisensor 14; in this latter case, i.e., if the increase in the operating temperature of the NOx-Trapcatalytic converter 11 has led to the disappearance of the anomalous transition in the signal from themultisensor 14, then thecontrol unit 15 increases the minimum value of the operating temperature of the NOx-Trapcatalytic converter 11 stored in thememory 16 by a predetermined quantity because the reduction in the trapping capacity C of the NOx-Trapcatalytic converter 11 is essentially due to thermal degradation and can be at least partly offset by increasing the operating temperature of the NOx-Trapcatalytic converter 11. Obviously, thecontrol unit 15 does not increase the minimum value of the operating temperature of the NOx-Trapcatalytic converter 11 beyond a predetermined threshold value in order to maintain an acceptably wide operating temperature range for the NOx-Trapcatalytic converter 11. - If, on the other hand, the increase in the operating temperature of the NOx-Trap
catalytic converter 11 did not lead to the disappearance of the anomalous transition in the signal from themultisensor 14, then thecontrol unit 15 performs an unscheduled desulfation process with a temperature value for the NOx-Trapcatalytic converter 11 and an average value for ratio equal to the corresponding values used during the preceding desulfation processes. On completion of the unscheduled desulfation process, thecontrol unit 15 awaits performance of the subsequent NOx regeneration process. - If, during the subsequent NOx regeneration process, the anomalous transition in the signal from the
multisensor 14 no longer occurs, then thecontrol unit 15 increments the temperature value of the NOx-Trapcatalytic converter 11 and decrements the average value for ratio used during future desulfation processes because the reduction in the trapping capacity C of the NOx-Trapcatalytic converter 11 is essentially due to the formation of particularly tenacious sulfur crystals. Obviously, thecontrol unit 15 does not increase the temperature value for the NOx-Trapcatalytic converter 11 nor does it decrement the average value for ratio used during desulfation processes beyond the respective predetermined thresholds. - If, on the other hand, the anomalous transition in the signal from the
multisensor 14 still occurs in the subsequent NOx regeneration process, then thecontrol unit 15 assumes that this phenomenon is due to irreversible degradation of the NOx-Trapcatalytic converter 11 and thus reduces the estimated trapping capacity C of the NOx-Trapcatalytic converter 11 used in the storage model for the NOx-Trapcatalytic converter 11 by a predetermined amount. - According to another embodiment, the predicted duration of the NOx regeneration process of the NOx-Trap
catalytic converter 11 is not assumed to be equal to a predetermined value stored in thememory 16, but is calculated before performing the NOx regeneration process by using the storage model for the NOx-Trapcatalytic converter 11 and using the model of the production of NOx and SOx group by the engine 1 in such a manner that the NOx regeneration process only lasts for the time strictly necessary to remove the NOx groups trapped in the NOx-Trapcatalytic converter 11. - From the above explanation, it is clear the
control unit 15, before reducing the estimated trapping capacity C of the NOx-Trapcatalytic converter 11 used in the storage model for the NOx-Trapcatalytic converter 11, attempts to identify the cause of the degradation of the trapping capacity C of the NOx-Trapcatalytic converter 11 and attempts, if possible, to remedy such degradation; by using this method, it is possible to avoid underestimating the actual trapping capacity C of the NOx-Trapcatalytic converter 11 and thus to avoid increasing the frequency of NOx regeneration processes beyond what is strictly necessary.
Claims (13)
1. Method for estimating the degradation of the trapping capacity of a NOx-Trap catalytic converter, which method provides for performing a first NOx regeneration process of a predetermined duration, determining whether the actual duration of the first NOx regeneration process is equal to the predetermined duration and assuming that the trapping capacity is unchanged if the actual duration of the first NOx regeneration process is equal to the predetermined duration; the method being characterised in that, if the actual duration of the first NOx regeneration process is less than the predetermined duration, at least one corrective action is performed in order to attempt to counteract the degeneration of the NOx-Trap catalytic converter, a subsequent NOx regeneration process is performed, it is determined whether the actual duration of the subsequent NOx regeneration process is equal to the predetermined duration, if the actual duration of the subsequent NOx regeneration process is equal to the predetermined duration, then new characteristic operating parameters for the corrective action are used for the subsequent life of the NOx-Trap catalytic converter whereas, if the actual duration of the subsequent NOx regeneration process is less than the predetermined duration, the estimated trapping capacity (C) of the NOx-Trap catalytic converter is reduced.
2. Method according to claim 1 , in which the signal of an ON/OFF type lambda sensor arranged upstream from the NOx-Trap catalytic converter is used to determine whether the actual duration of a NOx regeneration process is equal to the predetermined duration.
3. Method according to claim 2 , in which, if no transition in the signal from the lambda sensor is detected during the NOx regeneration process, then it is assumed that the actual duration of the NOx regeneration process is equal to the predetermined duration whereas, if a transition in the signal from the lambda sensor is detected during the NOx regeneration process, then it is assumed that the actual duration of the NOx regeneration process is less than the predetermined duration.
4. Method according to claim 1 , in which the corrective action provides for increasing the operating temperature of the NOx-Trap catalytic converter; if the actual duration of the subsequent NOx regeneration process is equal to the predetermined duration, then the minimum value of the operating temperature of said NOx-Trap catalytic converter is increased for the subsequent life of the NOx-Trap catalytic converter.
5. Method according to claim 4 , in which the minimum value of the operating temperature of the NOx-Trap catalytic converter is not increased beyond a respective predetermined threshold value.
6. Method according to claim 4 , in which the operating temperature of the NOx-Trap catalytic converter is increased by means of a number of successive increments of a determined size; after each increment, the performance of a subsequent NOx regeneration process is awaited and, if the actual duration of the subsequent NOx regeneration process is less than the predetermined duration, then a further increment is performed whereas, if the actual duration of the subsequent NOx regeneration process is equal to the predetermined duration, then incrementation of the operating temperature of the NOx-Trap catalytic converter is ceased and the minimum value of the operating temperature of said NOx-Trap catalytic converter is increased.
7. Method according to claim 6 , in which the value of the operating temperature of the NOx-Trap catalytic converter is not increased beyond a respective predetermined threshold value.
8. Method according to claim 1 , in which the corrective action provides for performing an unscheduled desulfation process and, on completion of the unscheduled desulfation process, awaiting performance of a subsequent NOx regeneration process; if the actual duration of the subsequent NOx regeneration process is equal to the predetermined duration, then the temperature value of the NOx-Trap catalytic converter is incremented and the average value for ratio used during future desulfation processes is decremented.
9. Method according to claim 8 , in which the temperature value of the NOx-Trap catalytic converter and the average value for ratio used during the desulfation processes are not modified beyond respective predetermined threshold values.
10. Method according to claim 1 , in which the corrective action provides for increasing the operating temperature of the NOx-Trap catalytic converter; if the actual duration of the subsequent NOx regeneration process is equal to the predetermined duration, then the minimum value of the operating temperature of said NOx-Trap catalytic converter is increased for the subsequent life of the NOx-Trap catalytic converter; if the actual duration of the subsequent NOx regeneration process is less than the predetermined duration, then an unscheduled desulfation process is performed and, on completion of the unscheduled desulfation process, performance of a subsequent NOx regeneration process is awaited; if the actual duration of the subsequent NOx regeneration process is equal to the predetermined duration, then the temperature value of the NOx-Trap catalytic converter is incremented and the average value for ratio used during future desulfation processes is decremented; if the actual duration of the subsequent NOx regeneration process is less than the predetermined duration, then the estimated trapping capacity of the NOx-Trap catalytic converter is reduced.
11. Method according to claim 10 , in which the operating temperature of the NOx-Trap catalytic converter is increased by means of a number of successive increments of a determined size; after each increment, the performance of a subsequent NOx regeneration process is awaited and, if the actual duration of the subsequent NOx regeneration process is less than the predetermined duration, then a further increment is performed whereas, if the actual duration of the subsequent NOx regeneration process is equal to the predetermined duration, then incrementation of the operating temperature of the NOx-Trap catalytic converter is ceased and the minimum value of the operating temperature of the NOx-Trap catalytic converter is increased.
12. Method according to claim 11 , in which the value of the operating temperature of the NOx-Trap catalytic converter is not increased beyond a respective predetermined threshold value.
13. Method according to claim 1 , in which the predicted value for the duration of the NOx regeneration process is calculated using a storage model of the NOx-Trap catalytic converter, said model being based on an estimate of the trapping capacity of the NOx-Trap catalytic converter, such that the NOx regeneration process only lasts for the time that is strictly necessary to remove the NOx groups trapped in the NOx-Trap catalytic converter.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
ITBO2003A000136 | 2003-03-12 | ||
IT000136A ITBO20030136A1 (en) | 2003-03-13 | 2003-03-13 | METHOD FOR ESTIMATING THE DEGRADATION OF THE CAPACITY OF |
Publications (1)
Publication Number | Publication Date |
---|---|
US20040250531A1 true US20040250531A1 (en) | 2004-12-16 |
Family
ID=32800663
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/800,416 Abandoned US20040250531A1 (en) | 2003-03-12 | 2004-03-12 | Method for estimating the degradation of the trapping capacity of NOx-Trap type catalytic converter |
Country Status (6)
Country | Link |
---|---|
US (1) | US20040250531A1 (en) |
EP (1) | EP1460246B1 (en) |
BR (1) | BRPI0400986B1 (en) |
DE (1) | DE602004011131T2 (en) |
ES (1) | ES2298679T3 (en) |
IT (1) | ITBO20030136A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20070089401A1 (en) * | 2005-10-24 | 2007-04-26 | Nieuwstadt Michiel V | Method for controlling an internal combustion engine during regeneration of an emission after treatment device |
US20070130920A1 (en) * | 2005-12-12 | 2007-06-14 | Nam Gun W | Method for regenerating NOx absorbing catalyst |
US20120311995A1 (en) * | 2011-06-10 | 2012-12-13 | Waratt Rattasiri | NOx ADSORBER CATALYST CONDITION EVALUATION APPARATUS AND ASSOCIATED METHODS |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
BRPI0520348A2 (en) | 2005-07-07 | 2009-05-05 | Volvo Lastvagnar Ab | computer program method, device and product for diagnosing at least one exhaust emission control unit |
US8701390B2 (en) * | 2010-11-23 | 2014-04-22 | International Engine Intellectual Property Company, Llc | Adaptive control strategy |
GB2502797A (en) * | 2012-06-06 | 2013-12-11 | Gm Global Tech Operations Inc | Method of assessing the thermal ageing of a catalyst in an exhaust system |
FR2999233B1 (en) * | 2012-12-11 | 2018-10-19 | Renault S.A.S. | DEVICE AND METHOD FOR DIAGNOSING AN OXIDE TRAPPER OF NITROGEN |
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DE10023060B4 (en) * | 2000-05-11 | 2009-12-24 | Volkswagen Ag | Method for determining the state of aging and for carrying out the NOx regeneration of a NOx storage catalytic converter |
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2003
- 2003-03-13 IT IT000136A patent/ITBO20030136A1/en unknown
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- 2004-03-11 ES ES04101011T patent/ES2298679T3/en not_active Expired - Lifetime
- 2004-03-11 EP EP04101011A patent/EP1460246B1/en not_active Expired - Fee Related
- 2004-03-11 DE DE602004011131T patent/DE602004011131T2/en not_active Expired - Lifetime
- 2004-03-12 US US10/800,416 patent/US20040250531A1/en not_active Abandoned
- 2004-03-12 BR BRPI0400986-0A patent/BRPI0400986B1/en not_active IP Right Cessation
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US5771685A (en) * | 1996-10-16 | 1998-06-30 | Ford Global Technologies, Inc. | Method for monitoring the performance of a NOx trap |
US6345498B2 (en) * | 1999-06-03 | 2002-02-12 | Mitsubishi Denki Kabushiki Kaisha | Exhaust gas purifier for internal combustion engine |
US6327848B1 (en) * | 1999-09-07 | 2001-12-11 | Magneti Marelli S.P.A | Self-adapting control method for an exhaust system for internal combustion engines with controlled ignition |
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US20070089401A1 (en) * | 2005-10-24 | 2007-04-26 | Nieuwstadt Michiel V | Method for controlling an internal combustion engine during regeneration of an emission after treatment device |
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Also Published As
Publication number | Publication date |
---|---|
EP1460246B1 (en) | 2008-01-09 |
DE602004011131T2 (en) | 2009-01-02 |
BRPI0400986B1 (en) | 2012-10-02 |
DE602004011131D1 (en) | 2008-02-21 |
EP1460246A2 (en) | 2004-09-22 |
BRPI0400986A (en) | 2005-01-18 |
EP1460246A3 (en) | 2005-10-26 |
ITBO20030136A1 (en) | 2004-09-14 |
ES2298679T3 (en) | 2008-05-16 |
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Owner name: MAGNETI MARELLI POWERTRAIN S.P.A., ITALY Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:PALMA, ALESSANDRO;GORGORETTI, LORENZO;LAMBERTINI, LORIS;REEL/FRAME:015632/0878 Effective date: 20040608 |
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