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EP0987408A2 - Method of operation of an internal combustion engine with sulphur accumulated exhaust gas purification components and internal combustion engine operated by using this method - Google Patents

Method of operation of an internal combustion engine with sulphur accumulated exhaust gas purification components and internal combustion engine operated by using this method Download PDF

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Publication number
EP0987408A2
EP0987408A2 EP99114565A EP99114565A EP0987408A2 EP 0987408 A2 EP0987408 A2 EP 0987408A2 EP 99114565 A EP99114565 A EP 99114565A EP 99114565 A EP99114565 A EP 99114565A EP 0987408 A2 EP0987408 A2 EP 0987408A2
Authority
EP
European Patent Office
Prior art keywords
exhaust gas
sulfur
internal combustion
combustion engine
enriching
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP99114565A
Other languages
German (de)
French (fr)
Other versions
EP0987408A3 (en
EP0987408B1 (en
Inventor
Jürgen Dr. Schmidt
Gerd Tiefenbacher
Anton Waltner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mercedes Benz Group AG
Original Assignee
DaimlerChrysler AG
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Publication date
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Publication of EP0987408A2 publication Critical patent/EP0987408A2/en
Publication of EP0987408A3 publication Critical patent/EP0987408A3/en
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Publication of EP0987408B1 publication Critical patent/EP0987408B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • F01N3/10—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
    • F01N3/18—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 characterised by methods of operation; Control
    • F01N3/22—Control of additional air supply only, e.g. using by-passes or variable air pump drives
    • F01N3/222—Control of additional air supply only, e.g. using by-passes or variable air pump drives using electric valves only
    • 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
    • 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
    • F01N13/0093—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 the purifying devices are of the same type
    • 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
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0871—Regulation of absorbents or adsorbents, e.g. purging
    • F01N3/0878—Bypassing absorbents or adsorbents
    • 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
    • F01N3/0871—Regulation of absorbents or adsorbents, e.g. purging
    • F01N3/0885—Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
    • 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
    • F01N3/18—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 characterised by methods of operation; Control
    • F01N3/22—Control of additional air supply only, e.g. using by-passes or variable air pump drives
    • 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
    • F01N3/24—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 characterised by constructional aspects of converting apparatus
    • F01N3/30—Arrangements for supply of additional air
    • 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
    • F02D41/028—Desulfurisation of NOx traps or adsorbent
    • 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
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/06—Introducing corrections for particular operating conditions for engine starting or warming up
    • F02D41/062—Introducing corrections for particular operating conditions for engine starting or warming up for starting
    • F02D41/064—Introducing corrections for particular operating conditions for engine starting or warming up for starting at cold start
    • 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/04—Sulfur or sulfur 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/14—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
    • 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
    • F01N2900/1612—SOx amount trapped in catalyst

Definitions

  • the invention relates to a method for operating an internal combustion engine system according to the preamble of claim 1 and to an internal combustion engine system operable with such a method according to the preamble of claim 8.
  • Systems of this type are used in particular in motor vehicles and contain an exhaust gas cleaning component in which during of the plant enriches sulfur contained in the fuel.
  • Such sulfur-enriching exhaust gas cleaning components can in particular be nitrogen oxide (NO x ) storage catalysts or so-called sulfur traps.
  • the sulfur-enriching exhaust gas cleaning component requires desulfation in order to free it from the accumulated sulfur, which is usually in sulfate form.
  • sulfur poisoning of NO x storage catalysts reduces their storage capacity.
  • desulfation takes place preferably at elevated exhaust gas temperatures and rich exhaust gas compositions.
  • the published patent application DE 195 22 165 A1 discloses a further method of this type with periodic desulfation of a NO x storage catalytic converter during ongoing engine operation when the storage capacity is recognized to be decreasing, as well as an internal combustion engine system in this regard, with activation of a respective desulfation phase to a richer engine air ratio and a later one
  • the ignition timing for the respective engine cylinder is changed and secondary air is also fed into the exhaust line upstream of the NO x storage catalytic converter. This is preferably done in such a way that the catalyst temperature is adjusted to a desired, increased desired value during the desulfation, which is maintained for a predeterminable period of time.
  • the invention is a technical problem of providing a method and an internal combustion engine system of the beginning mentioned type, in which excessive sulfur accumulation in a sulfur-enriching exhaust gas cleaning component is avoided by appropriate desulfation processes, which affect the normal engine operation as little as possible and cause no significant additional fuel consumption.
  • the invention solves this problem by providing a Operating method with the features of claim 1 and one Internal combustion engine system with the features of claim 8 or 9.
  • the internal combustion engine mostly not primarily anyway to minimize fuel consumption
  • Operated criteria as for a normal operating mode can be used with the engine warmed up, e.g. first trying in a catalyst heating mode, existing Exhaust gas cleaning components, in particular one or more exhaust gas catalytic converter units, to operating temperature as quickly as possible bring to.
  • the internal combustion engine for example, can also do this not operated in the so-called, fuel-efficient stratified charge mode be, and are appropriate catalyst heating measures Also useful for engines with direct injection.
  • the motor Catalyst heating measures for example the setting a rich engine air ratio
  • the motor measures for desulfation correspond to the sulfur-enriching exhaust gas cleaning component
  • the time intervals, a next desulfation process at the latest is necessary, typically noticeably larger than the time intervals consecutive cold starts, the cold start desulfation phases are sufficient generally to achieve a timely and sufficient desulfurization without additional Desulfation processes with the engine warmed up are necessary. This will not normal engine operation disturbed and associated fuel consumption avoided.
  • An operating method developed according to claim 4 is suitable for internal combustion engine systems which have an oxidation catalytic converter unit in the exhaust line downstream of the sulfur-enriching exhaust gas purification component, ie one with an oxidizing function, such as a three-way catalytic converter or a NO x storage catalytic converter.
  • secondary air is fed into the exhaust line for the oxidation catalyst unit during the desulfation, ie directly into this or into the exhaust line section between it and the currently desorbing, sulfur-enriching exhaust gas cleaning component. This allows both carbon monoxide and unburned hydrocarbons to be oxidized, as well as hydrogen sulfide which may arise during the desulfation.
  • An operating method developed according to claim 5 is suitable for internal combustion engine systems with two or more serial successive, sulfur-enriching emission control units.
  • the sulfur-enriching exhaust gas purification units in desulfation mode one after the other desulfurized, in a direction corresponding to the exhaust gas flow direction Sequence.
  • This desulfation process is carried out by accompanied by a secondary air supply, with the secondary air in each case only downstream from that sulfur-enriching Exhaust gas purification unit is fed into the exhaust line, which is just desulfurized.
  • the method according to a cold start activation the catalyst heating mode and then which includes the desulfation mode is advantageous the engine air ratio in desulfation mode set slightly bold, i.e. more fuel-rich than the stoichiometric Ratio, but less fuel than in catalyst heating mode, which has a positive effect on fuel consumption.
  • the internal combustion engine system according to claim 8 includes at least two sulfur-enriching series connected in the exhaust line Exhaust gas purification units and secondary air supply means, each with its own secondary air supply branch for the sulfur-enriching Atgas cleaning units included. So that is a targeted, procedural secondary air supply to the respective sulfur-enriching emission control component possible to for example, to bring them up to operating temperature more quickly or hydrocarbons, carbon monoxide contained in the supplied exhaust gas and / or to oxidize hydrogen sulfide.
  • the internal combustion engine system includes downstream the sulfur-enriching exhaust gas purification component, the comprise one or more serial exhaust gas purification units can, an oxidation catalyst unit.
  • the intended secondary air supply means comprise in addition to one or more secondary air supply branches for the sulfur-enriching exhaust gas cleaning component additionally its own secondary air supply branch for the oxidation catalyst unit, so that in this example during a desulfation process in the upstream, sulfur-enriching exhaust gas cleaning component formed Hydrogen sulfide can be oxidized.
  • the internal combustion engine system shown in FIG. 1 which can be provided in particular for a motor vehicle, contains an internal combustion engine 1, to which an exhaust line 2 is connected on the output side.
  • An exhaust gas cleaning system is assigned to the exhaust line 2, which comprises a sulfur-enriching exhaust gas cleaning component in the form of two series-connected NO x storage catalytic converters K1, K2 and a downstream three-way catalytic converter K3, which, among other things, has an oxidizing function and thus functions as an oxidation catalytic converter unit.
  • a bypass line 3 in which a controllable valve 4 is connected, the two NO x storage catalysts can be bypassed if necessary.
  • the two NO x storage catalytic converters K1, K2 are used to periodically adsorb nitrogen oxides contained in the exhaust gas and to desorb them again for conversion, for example by exhaust gas recirculation or a catalytic reduction, as is known per se and therefore no further explanation and graphic representation here requirement.
  • the exhaust gas purification system also contains desulfating agents in order to be able to free the NO x storage catalysts K1, K2 from the enriched sulfur, more precisely from the sulfate which has a poisoning effect on the nitrogen oxide adsorption function.
  • desulfating agents comprise secondary air supply means in the form of a secondary air line L1 with associated secondary air pump 5.
  • the secondary air line L1 branches downstream of the pump 5 into three line branches L2, L3, L4, one of which branches L2 into a first exhaust line section 2a between engine 1 and the upstream NO x storage catalytic converter K1, a second line branch L3 open into a second exhaust line section 2b between the two NO x storage catalytic converters K1, K2 and a third line branch L4 into a third exhaust gas section section 2c between the downstream NO x storage catalytic converter K2 and the three-way catalytic converter K3.
  • Each line branch L2, L3, L4 can be opened and closed by means of an associated, controllable valve 6, 7, 8.
  • the desulfating agents comprise a desulfating control unit, which preferably as a corresponding one Control part integrated in software or hardware in an engine control unit is that the engine 1 and the other components of the Exhaust gas cleaning system 2 controls. So much for the related components 1 are not shown to the person skilled in the art common, conventional components are used.
  • the control units are to be designed so that they Entire internal combustion engine system according to that explained below Can operate procedures. The implementation of these operational steps for example in the engine control unit is known to a person skilled in the art without knowledge of these process steps further possible, so that it is not discussed here are needed.
  • FIG. 2 An example of the operating method according to the invention for the internal combustion engine system of FIG. 1 is illustrated in diagram form in FIG. 2.
  • the process example shows schematically the time-dependent operating sequence in the event of a cold start.
  • the vehicle speed v Fzg , the exhaust gas temperature T, the air / fuel ratio ⁇ and the secondary air mass mL, that is to say the secondary air quantity fed into the exhaust line 2 by the secondary air supply means, are reproduced in their time course in four superimposed diagrams.
  • a first phase A which is very short in time, an engine start is triggered when the engine 1 is cold, ie the vehicle speed v Fzg is zero and the exhaust gas temperature T is at ambient temperature.
  • the operation is set to a catalyst heating mode in a subsequent phase B.
  • Appropriate engine control measures and secondary air supply cause the exhaust gas temperature to rise as quickly as possible in order to quickly bring the exhaust gas cleaning system, especially the exhaust gas catalytic converters K1, K2, K3, up to operating temperature.
  • the air / fuel mixture supplied to engine 1 is set to rich, that is to say to a lambda value of less than one, as shown on a corresponding, continuous line ⁇ M of the engine air ratio.
  • secondary air is fed into the upstream exhaust line section 2a via the first line branch L2, as shown by a corresponding, drawn, drawn, secondary air characteristic curve m L2 .
  • the other two secondary air line branches L3, L4 remain closed.
  • the secondary air supply in the exhaust line section 2a leading from the engine 1 leads to a lean exhaust gas composition, ie the lambda values ⁇ K1 , ⁇ K2 and ⁇ K3 in the three catalyst units K1, K2, K3 are above the stoichiometric value one, as in FIG dashed curve ⁇ K1 , the solid curve ⁇ K2 and the dash-dotted curve ⁇ K3 shown. As further shown in FIG.
  • the exhaust gas temperature T K2 upstream of the downstream NO x storage catalytic converter and the exhaust gas temperature T K3 upstream of the three-way catalytic converter K3 increase to a somewhat lesser extent, the three-way catalytic converter K3 at the end of the heating phase B having its starting temperature for the oxidation of unburned Has reached hydrocarbons and carbon monoxide.
  • a speed characteristic curve v F the vehicle is started in the last half of heating phase B.
  • the catalyst heating mode B is switched to a desulfation mode which includes two successive desulfation phases C, D.
  • engine operation is primarily set to desulfate the upstream NO x storage catalytic converter K1.
  • the supply of secondary air is shut off via the first line branch L2 to this NO x storage catalytic converter K1, ie the associated air mass characteristic curve m L2 drops to zero.
  • a secondary air supply can be provided in this operating phase with essentially the same effect only via the third line branch L4 for the three-way catalytic converter K3 or via the second and third line branches L3, L4.
  • the duration of the desulfation phase C for the upstream NO x storage catalytic converter is determined using a model calculation with regard to the sulfur poisoning.
  • This model-based estimate of the sulfur content in the NO x storage catalytic converter to be desorbed at the beginning is used as the decisive influencing variables, the fuel consumed and its sulfur content, as well as the evaluation of natural desulfation processes, such as may have occurred during a previous normal operating driving phase with the engine warmed up, by at times the conditions were favorable. This is the case, for example, with freeway and full-load operating phases.
  • a sensory diagnosis of the NO x storage state can be provided.
  • the second desulfation phase D in which primarily the next NO x storage catalytic converter K2 in the exhaust gas flow direction is desulfated.
  • the secondary air supply via the second line branch L3 for this downstream NO x storage catalytic converter K2 is ended, ie the associated characteristic curve m L3 drops to zero.
  • the supply of secondary air via the third line branch L4 for the three-way catalytic converter K3 is started at the latest, as shown in FIG. 2 on the basis of an associated third air mass characteristic m L4 .
  • the engine air ratio ⁇ M remains unchanged in the slightly rich range.
  • the catalytic converter air ratio ⁇ K2 for the NO x storage catalytic converter K2 now to be desulphated falls from the previously lean to the slightly rich range, as is favorable for the desulphation process.
  • the catalytic converter air ratio ⁇ K3 in the three-way catalytic converter K3, on the other hand, remains in the lean range, so that the oxidation of unburned hydrocarbons, carbon monoxide and, if appropriate, hydrogen sulfide formed during the desulfation is also ensured there.
  • the internal combustion engine system is switched over to normal operation for a next phase E, ie to operation optimized for fuel consumption and engine power.
  • the engine air ratio ⁇ M is set as lean as possible in this normal operation.
  • Nitrogen oxides generated in the engine are adsorbed by the NO x storage catalytic converters K1, K2.
  • they are subjected to a desorption process in a conventional manner, for which purpose the secondary air supply means can also be activated if necessary.
  • the operating method according to the invention can also be used Absence of a secondary air supply can be applied, provided it exhaust gas emissions from unburned hydrocarbons and Allow carbon monoxide in the cold start phase.
  • the appropriate one Operating conditions are then determined solely by operational control measures on engine 1 itself and without secondary air supply set in the exhaust system.
  • the Engine with a rich exhaust gas mixture during the cold start phase supplied so that on the one hand rapid catalyst heating and on the other hand a desulfurization of the sulfur-enriching Emission control component is reached.

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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)
  • Exhaust Gas After Treatment (AREA)

Abstract

The method of operation includes the operation of the IC engine system so that at specified times a desulfurizing mode is introduced. The operation of the IC engine system is introduced respectively in connection with a cold start activating of the IC engine, before the transition in a normal operating mode.

Description

Die Erfindung bezieht sich auf ein Verfahren zum Betrieb einer Verbrennungsmotoranlage nach dem Oberbegriff des Anspruchs 1 sowie auf eine mit einem solchen Verfahren betreibbare Verbrennungsmotoranlage nach dem Oberbegriff des Anspruchs 8. Anlagen dieser Art werden insbesondere in Kraftfahrzeugen eingesetzt und enthalten eine Abgasreinigungskomponente, in der sich während des Betriebs Schwefel anreichert, der im Kraftstoff enthalten ist. Solche schwefelanreichernde Abgasreinigungskomponenten können insbesondere Stickoxid(NOx)-Speicherkatalysatoren oder sogenannte Schwefelfallen sein.The invention relates to a method for operating an internal combustion engine system according to the preamble of claim 1 and to an internal combustion engine system operable with such a method according to the preamble of claim 8.Systems of this type are used in particular in motor vehicles and contain an exhaust gas cleaning component in which during of the plant enriches sulfur contained in the fuel. Such sulfur-enriching exhaust gas cleaning components can in particular be nitrogen oxide (NO x ) storage catalysts or so-called sulfur traps.

Die schwefelanreichernde Abgasreinigungskomponente bedarf von Zeit zu Zeit einer Desulfatisierung, um sie wieder vom angesammelten, meist in Sulfatform vorliegenden Schwefel zu befreien. So ist beispielsweise bekannt, daß die Schwefelvergiftung von NOx-Speicherkatalysatoren deren Speicherkapazität herabsetzt. Weiter ist bekannt, daß die Desulfatisierung bevorzugt bei erhöhten Abgastemperaturen und fetten Abgaszusammenensetzungen abläuft.From time to time, the sulfur-enriching exhaust gas cleaning component requires desulfation in order to free it from the accumulated sulfur, which is usually in sulfate form. For example, it is known that the sulfur poisoning of NO x storage catalysts reduces their storage capacity. It is also known that the desulfation takes place preferably at elevated exhaust gas temperatures and rich exhaust gas compositions.

Herkömmlicherweise werden Desulfatisierungsvorgänge im laufenden Motorbetrieb immer dann durchgeführt, wenn der Schwefelgehalt in der schwefelanreichernden Abgasreinigungskomponente ein gewisses Maß überschritten hat. Dies wird z.B. im Fall eines NOx-Speicherkatalysators dann angenommen, wenn dessen Speicherkapazität merklich nachläßt. Bei Verfahren dieser Art, wie sie in der Offenlegungsschrift EP 0 636 770 A1 und der deutschen Patentanmeldung Nr. 197 47 222.2 beschrieben sind, wird diese nachlassende Speicherkapazität daran erkannt, daß sich die Adsorptions- und Desorptionsphasen verkürzen. Die Dauer der Adsorptionsphasen kann durch einen stromabwärts des NOx-Speicherkatalysators positionierten NOx-Sensor und die Dauer der Desorptionsphasen durch eine dort positionierte Lambda-Sonde überwacht werden.Conventionally, desulfurization processes are carried out while the engine is running when the sulfur content in the sulfur-enriching exhaust gas cleaning component has exceeded a certain level. This is assumed, for example, in the case of a NO x storage catalytic converter when its storage capacity is noticeably reduced. In methods of this type, as described in published patent application EP 0 636 770 A1 and German patent application No. 197 47 222.2, this diminishing storage capacity is recognized by the fact that the adsorption and desorption phases are shortened. The duration of the adsorption phases can be monitored by a NO x sensor positioned downstream of the NO x storage catalytic converter and the duration of the desorption phases can be monitored by a lambda probe positioned there.

Zur Durchführung der Desulfatisierungsphasen wird in der genannten EF 0 636 770 A1 vorgeschlagen, den Verbrennungsmotor von magerem auf fettes Motorluftverhältnis, d.h. Luft/Kraftstoff-Verhältnis des dem Motor zugeführten Luft/Kraftstoff-Gemischs, umzustellen und bei Bedarf zusätzlich eine elektrische Heizeinrichtung für den NOx-Speicherkatalysator zu aktivieren. Die jeweilige Desulfatisierungsphase wird für einen vorgegebenen Zeitraum von z.B. 10 min. beibehalten. Bei dem Verfahren der genannten deutschen Patentanmeldung Nr. 197 47 222.2 wird die Einstellung eines ausreichend fetten Motorluftverhältnisses von einer Zudosierung von Sekundärluft in den Abgasstrang stromaufwärts des NOx-Speicherkatalysators begleitet. Dabei kann eine Regelung und nicht nur Steuerung des Katalysatorluftverhältnisses, d.h. des Luft/Kraftstoff-Verhältnisses des den NOx-Speicherkatalysator durchströmenden Abgases, vorgesehen sein, und die Katalysatortemperatur kann auf einen gewünschten Wert eingestellt werden.To carry out the desulfation phases, it is proposed in the aforementioned EF 0 636 770 A1 to convert the internal combustion engine from lean to rich engine air ratio, ie air / fuel ratio of the air / fuel mixture supplied to the engine, and, if necessary, an electric heating device for the NO to activate x storage catalytic converter. The respective desulfation phase is for a predetermined period of time, for example 10 minutes. maintained. In the process of the aforementioned German patent application No. 197 47 222.2, the setting of a sufficiently rich engine air ratio is accompanied by an addition of secondary air into the exhaust line upstream of the NO x storage catalytic converter. In this case, regulation and not only control of the catalytic converter air ratio, ie the air / fuel ratio of the exhaust gas flowing through the NO x storage catalytic converter, can be provided, and the catalytic converter temperature can be set to a desired value.

In der Offenlegungsschrift DE 195 22 165 A1 sind ein weiteres derartiges Verfahren mit periodischer Desulfatisierung eines NOx-Speicherkatalysators im laufenden Motorbetrieb bei erkanntem Nachlassen von dessen Speicherkapazität sowie eine diesbezügliche Verbrennungsmotoranlage bekannt, wobei dort zur Aktivierung einer jeweiligen Desulfatisierungsphase auf ein fetteres Motorluftverhältnis und einen späteren Zündzeitpunkt für den jeweiligen Motorzylinder umgestellt und außerdem Sekundärluft in den Abgasstrang stromaufwärts des NOx-Speicherkatalysators zugeführt wird. Dies erfolgt vorzugsweise so, daß während der Desulfatisierung, die für eine vorgebbare Zeitdauer aufrechterhalten wird, die Katalysatortemperatur auf einen gewünschten, erhöhten Sollwert eingeregelt wird.The published patent application DE 195 22 165 A1 discloses a further method of this type with periodic desulfation of a NO x storage catalytic converter during ongoing engine operation when the storage capacity is recognized to be decreasing, as well as an internal combustion engine system in this regard, with activation of a respective desulfation phase to a richer engine air ratio and a later one The ignition timing for the respective engine cylinder is changed and secondary air is also fed into the exhaust line upstream of the NO x storage catalytic converter. This is preferably done in such a way that the catalyst temperature is adjusted to a desired, increased desired value during the desulfation, which is maintained for a predeterminable period of time.

Der Erfindung liegt als technisches Problem die Bereitstellung eines Verfahrens und einer Verbrennungsmotoranlage der eingangs genannten Art zugrunde, bei denen eine übermäßige Schwefelansammlung in einer schwefelanreichernden Abgasreinigungskomponente durch entsprechende Desulfatisierungsvorgänge vermieden wird, die den normalen Motorbetrieb möglichst wenig beeinflussen und keinen nennenswerten Kraftstoffmehrverbrauch verursachen.The invention is a technical problem of providing a method and an internal combustion engine system of the beginning mentioned type, in which excessive sulfur accumulation in a sulfur-enriching exhaust gas cleaning component is avoided by appropriate desulfation processes, which affect the normal engine operation as little as possible and cause no significant additional fuel consumption.

Die Erfindung löst dieses Problem durch die Bereitstellung eines Betriebsverfahrens mit den Merkmalen des Anspruchs 1 sowie einer Verbrennungsmotoranlage mit den Merkmalen des Anspruchs 8 oder 9.The invention solves this problem by providing a Operating method with the features of claim 1 and one Internal combustion engine system with the features of claim 8 or 9.

Gemäß dem Verfahren nach Anspruch 1 wird jeweils bei einem Kaltstart ein Desulfatisierungsvorgang ausgelöst, in welchem der Betrieb der Verbrennungsmotoranlage auf den entsprechenden Desulfatisierungsmodus eingestellt wird. In dem an eine Kaltstartaktivierung anschließenden Zeitraum wird der Verbrennungsmotor meist ohnehin noch nicht primär nach kraftstoffverbrauchsminimierenden Kriterien betrieben, wie sie für einen Normalbetriebsmodus bei warmgelaufenem Motor Anwendung finden können, da z.B. zunächst in einem Katalysatorheizmodus versucht wird, vorhandene Abgasreinigungskomponenten, insbesondere eine oder mehrere Abgaskatalysatoreinheiten, möglichst rasch auf Betriebstemperatur zu bringen. Dazu kann beispielsweise der Verbrennungsmotor noch nicht im sogenannten, verbrauchsgünstigen Schichtladebetrieb gefahren werden, und entsprechende Katalysatorheizmaßnahmen sind auch bei Motoren mit Direkteinspritzung zweckmäßig. Da die motorischen Katalysatorheizmaßnahmen, die beispielsweise die Einstellung eines fetten Motorluftverhältnisses beinhalten, weitestgehend mit den motorischen Maßnahmen zur Desulfatisierung der schwefelanreichernden Abgasreinigungskomponente korrespondieren, entsteht durch die erfindungsgemäße Vorgehensweise kein merklich höherer Kraftstoffverbrauch im Vergleich zu einem Anlagenbetrieb ohne Desulfatisierungsvorgänge. Da die Zeitabstände, zu denen spätestens wieder ein nächster Desulfatisierungsvorgang notwendig ist, typischerweise merklich größer als die Zeitabstände aufeinanderfolgender Kaltstarts sind, reichen die Kaltstart-Desulfatisierungsphasen im allgemeinen zur Erzielung einer rechtzeitigen und ausreichenden Entschwefelung aus, ohne daß zusätzliche Desulfatisierungsvorgänge bei warmgelaufenem Motor notwendig sind. Dadurch werden der normale Motorbetrieb nicht gestört und ein damit einhergehender Kraftstoffmehrverbrauch vermieden.According to the method of claim 1, each time a cold start triggered a desulfation process in which the operation the internal combustion engine system to the corresponding desulfation mode is set. In the cold start activation subsequent period is the internal combustion engine mostly not primarily anyway to minimize fuel consumption Operated criteria as for a normal operating mode can be used with the engine warmed up, e.g. first trying in a catalyst heating mode, existing Exhaust gas cleaning components, in particular one or more exhaust gas catalytic converter units, to operating temperature as quickly as possible bring to. The internal combustion engine, for example, can also do this not operated in the so-called, fuel-efficient stratified charge mode be, and are appropriate catalyst heating measures Also useful for engines with direct injection. Because the motor Catalyst heating measures, for example the setting a rich engine air ratio, as far as possible with the motor measures for desulfation correspond to the sulfur-enriching exhaust gas cleaning component, arises from the procedure according to the invention noticeably higher fuel consumption compared to plant operation without desulfation processes. Because the time intervals, a next desulfation process at the latest is necessary, typically noticeably larger than the time intervals consecutive cold starts, the cold start desulfation phases are sufficient generally to achieve a timely and sufficient desulfurization without additional Desulfation processes with the engine warmed up are necessary. This will not normal engine operation disturbed and associated fuel consumption avoided.

Bei einem nach Anspruch 2 weitergebildeten Verfahren wird nach der Aktivierung eines Motorkaltstarts der Betrieb der Verbrennungsmotoranlage zunächst auf einen Katalysatorheizmodus eingestellt, bis die Temperatur der schwefelanreichernden Abgasreinigungskomponente einen vorgebbaren Entschwefelungsmindestwert überschreitet, wonach dann der Betrieb auf den Desulfatisierungsmodus umgestellt wird. Der anfängliche Katalysatorheizmodus ermöglicht ein sehr rasches Erreichen einer ausreichenden Entschwefelungstemperatur für die zu desulfatisierende Abgasreinigungskomponente. In weiterer Ausgestaltung dieser Maßnahme kann gemäß Anspruch 3 während des Katalysatorheizmodus Sekundärluft in die schwefelanreichernde Abgasreinigungskomponente oder stromaufwärts davon in den Abgasstrang eingespeist werden, wodurch sich in Verbindung mit der Wahl eines fetten Motorluftverhältnisses die Abgastemperatur rasch steigern läßt. Bei Umstellung auf den Desulfatisierungsmodus wird diese Sekundärluftzufuhr beendet.In a further developed method according to claim 2 the activation of an engine cold start the operation of the internal combustion engine system first set to a catalyst heating mode, until the temperature of the sulfur-enriching exhaust gas cleaning component a predefinable minimum desulfurization value then the operation to the desulfation mode is converted. The initial catalyst heating mode enables a sufficient desulfurization temperature to be reached very quickly for the exhaust gas cleaning component to be desulfated. In a further embodiment of this measure according to claim 3 during the catalyst heating mode secondary air into the sulfur-enriching exhaust gas cleaning component or be fed upstream thereof into the exhaust line, whereby in connection with the selection of a rich engine air ratio allows the exhaust gas temperature to rise rapidly. When changing this secondary air supply is switched to the desulfation mode completed.

Ein nach Anspruch 4 weitergebildetes Betriebsverfahren eignet sich für Verbrennungsmotoranlagen, die im Abgasstrang stromabwärts der schwefelanreichernden Abgasreinigungskomponente eine Oxidationskatalysatoreinheit, d.h. eine solche mit oxidierender Funktion, aufweisen, wie z.B. einen Dreiwege-Katalysator oder einen NOx-Speicherkatalysator. Gemäß dieser Verfahrensvariante wird während der Desulfatisierung Sekundärluft in den Abgasstrang für die Oxidationskatalysatoreinheit eingespeist, d.h. direkt in diese oder in den Abgasstrangabschnitt zwischen ihr und der momentan desorbierenden, schwefelanreichernden Abgasreinigungskomponente. Dies erlaubt ein Oxidieren sowohl von Kohlenmonoxid und unverbrannten Kohlenwasserstoffen als auch von eventuell bei der Desulfatisierung entstehendem Schwefelwasserstoff.An operating method developed according to claim 4 is suitable for internal combustion engine systems which have an oxidation catalytic converter unit in the exhaust line downstream of the sulfur-enriching exhaust gas purification component, ie one with an oxidizing function, such as a three-way catalytic converter or a NO x storage catalytic converter. According to this variant of the method, secondary air is fed into the exhaust line for the oxidation catalyst unit during the desulfation, ie directly into this or into the exhaust line section between it and the currently desorbing, sulfur-enriching exhaust gas cleaning component. This allows both carbon monoxide and unburned hydrocarbons to be oxidized, as well as hydrogen sulfide which may arise during the desulfation.

Ein nach Anspruch 5 weitergebildetes Betriebsverfahren eignet sich für Verbrennungsmotoranlagen mit zwei oder mehr seriell hintereinanderliegenden, schwefelanreichernden Abgasreinigungseinheiten. Verfahrensgemäß werden die schwefelanreichernden Abgasreinigungseinheiten im Desulfatisierungsmodus nacheinander entschwefelt, und zwar in einer der Abgasströzaungsrichtung entsprechenden Reihenfolge. Dieser Desulfatisierungsprozeß wird von einer Sekundärluftzuführung begleitet, mit der Sekundärluft jeweils nur noch stromabwärts von derjenigen schwefelanreichernden Abgasreinigungseinheit in den Abgasstrang zugeführt wird, die gerade entschwefelt wird. Damit wird einerseits eine unerwünschte Sekundärluftzufuhr zu derjenigen Abgasreinigungseinheit, die gerade desulfatisiert wird, vermieden und andererseits eine Oxidation von Kohlenmonoxid, unverbrannten Kohlenwasserstoffen und bei der Entschwefelung eventuell entstehendem Schwefelwasserstoff gewährleistet.An operating method developed according to claim 5 is suitable for internal combustion engine systems with two or more serial successive, sulfur-enriching emission control units. According to the method, the sulfur-enriching exhaust gas purification units in desulfation mode one after the other desulfurized, in a direction corresponding to the exhaust gas flow direction Sequence. This desulfation process is carried out by accompanied by a secondary air supply, with the secondary air in each case only downstream from that sulfur-enriching Exhaust gas purification unit is fed into the exhaust line, which is just desulfurized. On the one hand, this becomes an undesirable one Secondary air supply to the exhaust gas purification unit that is desulfated, avoided and on the other hand oxidation of carbon monoxide, unburned hydrocarbons and During the desulfurization, any hydrogen sulfide formed guaranteed.

Bei einem nach Anspruch 6 weitergebildeten Verfahren, das nach einer Kaltstartaktivierung den Katalysatorheizmodus und anschließend den Desulfatisierungsmodus beinhaltet, wird vorteilhafterweise das Motorluftverhältnis im Desulfatisierungsmodus leicht fett eingestellt, d.h. kraftstoffreicher als das stöchiometrische Verhältnis, jedoch kraftstoffärmer als im Katalysatorheizmodus, was sich günstig auf den Kraftstoffverbrauch auswirkt.In a further developed according to claim 6, the method according to a cold start activation the catalyst heating mode and then which includes the desulfation mode is advantageous the engine air ratio in desulfation mode set slightly bold, i.e. more fuel-rich than the stoichiometric Ratio, but less fuel than in catalyst heating mode, which has a positive effect on fuel consumption.

Gemäß einem nach Anspruch 7 weitergebildeten Verfahren wird die Dauer des jeweiligen Desulfatisierungsmodus aus einer sensorischen Überwachung des Schwefelspeicherzustands der schwefelanreichernden Abgasreinigungskomponente oder einer modellbasierten Schätzung ermittelt. In einer solchen Schätzung finden neben der verbrauchten Kraftstoffmenge und dem Schwefelgehalt des Kraftstoffs auch zwischenzeitlich stattgefundene, natürliche Desulfatisierungsvorgänge Berücksichtung. Darunter sind solche Desulfatisierungsprozesse zu verstehen, die bei warmgelaufenem Motor in Zeiträumen stattfinden, in denen aufgrund des aktuellen Motorbetriebszustands in der schwefelanreichernden Abgasreinigungskomponente desulfatisierungsfördernde Bedingungen herrschen, insbesondere ausreichend hohe Temperatur und ausreichend fettes Luft/Kraftstoff-Verhältnis des Abgases, wie z.B. bei Autobahn- und/oder Vollastfahrt.According to a further developed method according to claim 7 Duration of the respective desulfation mode from a sensory Monitoring the sulfur storage status of the sulfur-enriching Emission control component or a model-based Estimate determined. In such an estimate, in addition to the amount of fuel consumed and the sulfur content of the fuel also natural desulfation processes that have taken place in the meantime Consideration. These include such desulfation processes to understand the in with the engine warmed up Periods of time take place due to the current engine operating status in the sulfur-enriching exhaust gas cleaning component Desulfation-promoting conditions prevail, in particular sufficiently high temperature and sufficiently fat Air / fuel ratio of the exhaust gas, e.g. for freeway and / or Full load.

Die Verbrennungsmotoranlage nach Anspruch 8 beinhaltet wenigstens zwei seriell in den Abgasstrang geschaltete, schwefelanreichernde Abgasreinigungseinheiten sowie Sekundärluftzufuhrmittel, die je einen eigenen Sekundärluftzufuhrzweig für die schwefelanreichernden Atgasreinigungseinheiten enthalten. Damit ist eine gezielte, verfahrensgemäße Sekundärluftzufuhr zur jeweiligen schwefelanreichernden Abgasreinigungskomponente möglich, um beispielsweise diese schneller auf Betriebstemperatur zu bringen oder im zugeführten Abgas enthaltene Kohlenwasserstoffe, Kohlenmonoxid und/oder Schwefelwasserstoff zu oxidieren.The internal combustion engine system according to claim 8 includes at least two sulfur-enriching series connected in the exhaust line Exhaust gas purification units and secondary air supply means, each with its own secondary air supply branch for the sulfur-enriching Atgas cleaning units included. So that is a targeted, procedural secondary air supply to the respective sulfur-enriching emission control component possible to for example, to bring them up to operating temperature more quickly or hydrocarbons, carbon monoxide contained in the supplied exhaust gas and / or to oxidize hydrogen sulfide.

Die Verbrennungsmotoranlage nach Anspruch 9 beinhaltet stromabwärts der schwefelanreichernden Abgasreinigungskomponente, die eine oder mehrere serielle Abgasreinigungseinheiten umfassen kann, eine Oxidationskatalysatoreinheit. Die vorgesehenen Sekundärluftzufuhrmittel umfassen neben einem oder mehreren Sekundärluftzufuhrzweigen für die schwefelanreichernde Abgasreinigungskomponente zusätzlich einen eigenen Sekundärluftzufuhrzweig für die Oxidationskatalysatoreinheit, so daß in dieser beispielsweise während eines Desulfatisierungsvorgangs in der stromaufwärtigen, schwefelanreichernden Abgasreinigungskomponente gebildeter Schwefelwasserstoff oxidiert werden kann.The internal combustion engine system according to claim 9 includes downstream the sulfur-enriching exhaust gas purification component, the comprise one or more serial exhaust gas purification units can, an oxidation catalyst unit. The intended secondary air supply means comprise in addition to one or more secondary air supply branches for the sulfur-enriching exhaust gas cleaning component additionally its own secondary air supply branch for the oxidation catalyst unit, so that in this example during a desulfation process in the upstream, sulfur-enriching exhaust gas cleaning component formed Hydrogen sulfide can be oxidized.

Eine vorteilhafte Ausführungsform der Erfindung ist in den Zeichnungen dargestellt und wird nachfolgend beschrieben. Hierbei zeigen:

Fig. 1
ein schematisches Blockdiagramm einer Verbrennungsmotoranlage und
Fig. 2
ein schematisches Betriebsablaufdiagramm eines Verfahrens zum Betrieb der Verbrennungsmotoranlage von Fig. 1.
An advantageous embodiment of the invention is shown in the drawings and is described below. Here show:
Fig. 1
a schematic block diagram of an internal combustion engine system and
Fig. 2
2 shows a schematic operating flow diagram of a method for operating the internal combustion engine system from FIG. 1.

Die in Fig. 1 gezeigte Verbrennungsmotoranlage, die insbesondere für ein Kraftfahrzeug vorgesehen sein kann, beinhaltet einen Verbrennungsmotor 1, an den sich ausgangsseitig ein Abgasstrang 2 anschließt. Dem Abgasstrang 2 ist eine Abgasreinigungsanlage zugeordnet, die eine schwefelanreichernde Abgasreinigungskomponente in Form zweier hintereinandergeschalteter NOx-Speicherkatalysatoren K1, K2 und einen nachgeschalteten Dreiwege-Katalysator K3 umfaßt, der unter anderem eine oxidierende Funktion hat und damit als Oxidationskatalysatoreinheit fungiert. Mit einer Bypassleitung 3, in die ein ansteuerbares Ventil 4 geschaltet ist, können die beiden NOx-Speicherkatalysatoren bei Bedarf umgangen werden. Die beiden NOx-Speicherkatalysatoren K1, K2 dienen dazu, im Abgas enthaltene Stickoxide periodisch zu adsorbieren und zwecks Konvertierung, z.B. durch Abgasrückführung oder eine katalytische Reduktion, wieder zu desorbieren, wie dies an sich bekannt ist und daher hier keiner näheren Erläuterung und zeichnerischen Darstellung bedarf.The internal combustion engine system shown in FIG. 1, which can be provided in particular for a motor vehicle, contains an internal combustion engine 1, to which an exhaust line 2 is connected on the output side. An exhaust gas cleaning system is assigned to the exhaust line 2, which comprises a sulfur-enriching exhaust gas cleaning component in the form of two series-connected NO x storage catalytic converters K1, K2 and a downstream three-way catalytic converter K3, which, among other things, has an oxidizing function and thus functions as an oxidation catalytic converter unit. With a bypass line 3, in which a controllable valve 4 is connected, the two NO x storage catalysts can be bypassed if necessary. The two NO x storage catalytic converters K1, K2 are used to periodically adsorb nitrogen oxides contained in the exhaust gas and to desorb them again for conversion, for example by exhaust gas recirculation or a catalytic reduction, as is known per se and therefore no further explanation and graphic representation here requirement.

Die Abgasreinigungsanlage beinhaltet des weiteren Desulfatisierungsmittel, um die NOx-Speicherkatalysatoren K1, K2 vom angereicherten Schwefel, genauer von dem für die Stickoxid-Adsorptionsfunktion vergiftend wirkenden Sulfat, befreien zu können. Diese Desulfatisierungsmittel umfassen Sekundärluftzuführungsmittel in Form einer Sekundärluftleitung L1 mit zugehöriger Sekundärluftpumpe 5. Die Sekundärluftleitung L1 verzweigt sich stromabwärts der Pumpe 5 in drei Leitungszweige L2, L3, L4, von denen ein erster Zweig L2 in einen ersten Abgasstrangabschnitt 2a zwischen Motor 1 und dem stromaufwärtigen NOx-Speicherkatalysator K1, ein zweiter Leitungszweig L3 in einen zweiten Abgasstrangabschnitt 2b zwischen den beiden NOx-Speicherkatalysatoren K1, K2 und ein dritter Leitungszweig L4 in einen dritten Abgasstangabschnitt 2c zwischen dem stromabwärtigen NOx-Speicherkatalysator K2 und dem Dreiwege-Katalysator K3 münden. Jeder Leitungszweig L2, L3, L4 kann mittels eines zugehörigen, ansteuerbaren Ventils 6, 7, 8 geöffnet und geschlossen werden.The exhaust gas purification system also contains desulfating agents in order to be able to free the NO x storage catalysts K1, K2 from the enriched sulfur, more precisely from the sulfate which has a poisoning effect on the nitrogen oxide adsorption function. These desulfating agents comprise secondary air supply means in the form of a secondary air line L1 with associated secondary air pump 5. The secondary air line L1 branches downstream of the pump 5 into three line branches L2, L3, L4, one of which branches L2 into a first exhaust line section 2a between engine 1 and the upstream NO x storage catalytic converter K1, a second line branch L3 open into a second exhaust line section 2b between the two NO x storage catalytic converters K1, K2 and a third line branch L4 into a third exhaust gas section section 2c between the downstream NO x storage catalytic converter K2 and the three-way catalytic converter K3. Each line branch L2, L3, L4 can be opened and closed by means of an associated, controllable valve 6, 7, 8.

Darüber hinaus umfassen die Desulfatisierungsmittel eine Desulfatisierungssteuereinheit, die vorzugsweise als entsprechender Steuerteil in Software oder Hardware in ein Motorsteuergerät integriert ist, das den Motor 1 und die übrigen Komponenten der Abgasreinigungsanlage 2 steuert. Soweit die diesbezüglichen Komponenten in Fig. 1 nicht gezeigt sind, können hierfür dem Fachmann geläufige, herkömmliche Komponenten verwendet werden. Dabei sind lediglich die Steuereinheiten so auszulegen, daß sie die gesamte Verbrennungsmotoranlage gemäß dem nachfolgend erläuterten Verfahren betreiben können. Die Implementierung dieser Betriebsverfahrensschritte beispielsweise in das Motorsteuergerät ist dem Fachmann bei Kenntnis dieser Verfahrensschritte ohne weiteres möglich, so daß darauf hier nicht näher eingegangen zu werden braucht.In addition, the desulfating agents comprise a desulfating control unit, which preferably as a corresponding one Control part integrated in software or hardware in an engine control unit is that the engine 1 and the other components of the Exhaust gas cleaning system 2 controls. So much for the related components 1 are not shown to the person skilled in the art common, conventional components are used. Here only the control units are to be designed so that they Entire internal combustion engine system according to that explained below Can operate procedures. The implementation of these operational steps for example in the engine control unit is known to a person skilled in the art without knowledge of these process steps further possible, so that it is not discussed here are needed.

In Fig. 2 ist in Diagrammform ein Beispiel des erfindungsgemäßen Betriebsverfahrens für die Verbrennungsmotoranlage von Fig. 1 illustriert. Das Verfahrensbeispiel zeigt schematisch den zeitabhängigen Betriebsablauf für den Fall eines Kaltstarts. Dabei sind im Diagramm von Fig. 2 in vier übereinanderliegenden Diagrammen die Fahrzeuggeschwindigkeit vFzg, die Abgastemperatur T, das Luft/Kraftstoff-Verhältnis λ und die Sekundärluftmasse mL, d.h. die von den Sekundärluftzufuhrmitteln in den Abgasstrang 2 eingespeiste Sekundärluftmenge, in ihrem Zeitverlauf wiedergegeben.An example of the operating method according to the invention for the internal combustion engine system of FIG. 1 is illustrated in diagram form in FIG. 2. The process example shows schematically the time-dependent operating sequence in the event of a cold start. In the diagram of FIG. 2, the vehicle speed v Fzg , the exhaust gas temperature T, the air / fuel ratio λ and the secondary air mass mL, that is to say the secondary air quantity fed into the exhaust line 2 by the secondary air supply means, are reproduced in their time course in four superimposed diagrams.

In einer ersten, zeitlich sehr kurzen Phase A wird ein Motorstart bei kaltem Motor 1 ausgelöst, d.h. die Fahrzeuggeschwindigkeit vFzg ist null und die Abgastempteratur T liegt auf Umgebungstemperatur. Nach dieser Aktivierung eines Motorkaltstarts wird der Betrieb in einer anschließenden Phase B auf einen Katalysatorheizmodus eingestellt. In diesem wird durch entsprechende Motorsteuerungsmaßnahmen und Sekundärluftzuführung eine möglichst rasche Steigerung der Abgastemperatur bewirkt, um die Abgasreinigungsanlage, speziell die Abgaskatalysatoren K1, K2, K3, schnell auf Betriebstemperatur zu bringen. Das dem Motor 1 zugeführte Luft/Kraftstoff-Gemisch wird hierzu fett eingestellt, d.h. auf einen Lambdawert kleiner eins, wie an einer entsprechenden, durchgezogen gezeichneten Kennlinie λM des Motorluftverhältnisses dargestellt. Gleichzeitig wird über den ersten Leitungszweig L2 Sekundärluft in den stromaufwärtigen Abgasstrangabschnitt 2a eingespeist, wie mit einer entsprechenden, durchgezogen gezeichneten, ersten Sekundärluftkennlinie mL2 gezeigt. Die beiden anderen Sekundärluftleitungszweige L3, L4 bleiben geschlossen.In a first phase A, which is very short in time, an engine start is triggered when the engine 1 is cold, ie the vehicle speed v Fzg is zero and the exhaust gas temperature T is at ambient temperature. After this activation of an engine cold start, the operation is set to a catalyst heating mode in a subsequent phase B. Appropriate engine control measures and secondary air supply cause the exhaust gas temperature to rise as quickly as possible in order to quickly bring the exhaust gas cleaning system, especially the exhaust gas catalytic converters K1, K2, K3, up to operating temperature. For this purpose, the air / fuel mixture supplied to engine 1 is set to rich, that is to say to a lambda value of less than one, as shown on a corresponding, continuous line λ M of the engine air ratio. At the same time, secondary air is fed into the upstream exhaust line section 2a via the first line branch L2, as shown by a corresponding, drawn, drawn, secondary air characteristic curve m L2 . The other two secondary air line branches L3, L4 remain closed.

Die Sekundärluftzuführung in den vom Motor 1 abgehenden Abgasstrangabschnitt 2a führt zu einer mageren Abgaszusammensetzung, d.h. die Lambdawerte λK1, λK2 und λK3 in den drei Katalysatoreinheiten K1, K2, K3 liegen über dem stöchiometrischen Wert eins, wie in Fig. 2 durch die gestrichelte Kennlinie λK1, die durchgezogene Kennlinie λK2 und die strichpunktierte Kennlinie λK3 gezeigt. Wie weiter in Fig. 2 anhand entsprechender Temperaturkennlinien TK1, TK2 und TK3 dargestellt, nimmt durch diese Maßnahmen im Katalysatorheizmodus die Abgastemperatur TK1 vor dem stromaufwärtigen NOx-Speicherkatalysator sehr schnell zu und erreicht am Ende dieser Heizphase B eine zur Durchführung einer anschließenden Desulfatisierungsphase ausreichende Entschwefelungstemperatur von typischerweise etwa 550°C oder mehr. Parallel dazu nehmen auch die Abgastemperatur TK2 vor dem stromabwärtigen NOx-Speicherkatalysator und die Abgastemperatur TK3 vor dem Dreiwege-Katalysator K3 in etwas geringerem Maße zu, wobei der Dreiwege-Katalysator K3 am Ende der Heizphase B seine Anspringtemperatur für die Oxidation von unverbrannten Kohlenwasserstoffen und Kohlenmonoxid erreicht hat. Wie anhand einer Geschwindigkeitskennlinie vF zu erkennen, wird das Fahrzeug in der letzten Hälfte der Heizphase B angefahren.The secondary air supply in the exhaust line section 2a leading from the engine 1 leads to a lean exhaust gas composition, ie the lambda values λ K1 , λ K2 and λ K3 in the three catalyst units K1, K2, K3 are above the stoichiometric value one, as in FIG dashed curve λ K1 , the solid curve λ K2 and the dash-dotted curve λ K3 shown. As further shown in FIG. 2 using the corresponding temperature characteristics T K1 , T K2 and T K3 , these measures in the catalytic converter heating mode increase the exhaust gas temperature T K1 upstream of the upstream NO x storage catalytic converter very quickly and at the end of this heating phase B reaches one for carrying out a subsequent desulfation phase, a sufficient desulfurization temperature of typically about 550 ° C. or more. At the same time, the exhaust gas temperature T K2 upstream of the downstream NO x storage catalytic converter and the exhaust gas temperature T K3 upstream of the three-way catalytic converter K3 increase to a somewhat lesser extent, the three-way catalytic converter K3 at the end of the heating phase B having its starting temperature for the oxidation of unburned Has reached hydrocarbons and carbon monoxide. As can be seen from a speed characteristic curve v F , the vehicle is started in the last half of heating phase B.

Nachdem die Katalysatoreinheiten K1, K2, K3 auf diese Weise auf Betriebstemperatur gebracht wurden, wird vom Katalysatorheizmodus B auf einen Desulfatisierungsmodus umgeschaltet, der zwei aufeinanderfolgende Desulfatisierungsphasen C, D beinhaltet. In der ersten Desulfatisierungsphase C wird der Motoranlagenbetrieb primär auf die Desulfatisierung des stromaufwärtigen NOx-Speicherkatalysators K1 eingestellt. Dazu wird die Zuführung von Sekundärluft über den ersten Leitungszweig L2 zu diesem NOx-Speicherkatalysator K1 abgestellt, d.h. die zugehörige Luftmassenkennlinie mL2 fällt auf null ab. Gleichzeitig wird über den zweiten Leitungszweig L3 Sekundärluft in den Abgasstrangabschnitt 2b vor dem stromabwärtigen NOx-Speicherkatalysator K2 zugeführt, wie am Anstieg einer zugehörigen, gestrichelt gezeichneten, zweiten Sekundärluftkennlinie mL3 zu erkennen. Das Motorluftverhältnis λM wird beim Übergang zum Desulfatisierungsmodus auf einen nur noch geringfügig unter dem stöchiometrischen Wert eins liegenden Wert angehoben, d.h. der Motor 1 wird leicht fett betrieben.After the catalyst units K1, K2, K3 have been brought up to operating temperature in this way, the catalyst heating mode B is switched to a desulfation mode which includes two successive desulfation phases C, D. In the first desulfation phase C, engine operation is primarily set to desulfate the upstream NO x storage catalytic converter K1. For this purpose, the supply of secondary air is shut off via the first line branch L2 to this NO x storage catalytic converter K1, ie the associated air mass characteristic curve m L2 drops to zero. At the same time, secondary air is fed into the exhaust line section 2b upstream of the downstream NO x storage catalytic converter K2 via the second line branch L3, as can be seen from the rise of an associated second secondary air characteristic curve m L3 shown in dashed lines. During the transition to the desulfation mode, the engine air ratio λ M is raised to a value only slightly below the stoichiometric value one, ie the engine 1 is operated slightly rich.

Durch diese Maßnahmen ändert sich das Katalysatorluftverhältnis λK1 im stromaufwärtigen NOx-Speicherkatalysator K1 von einem mageren auf einen leicht fetten, den Desulfatisierungsvorgang fördernden Wert, während sich die Katalysatorluftverhältnisse λK2, λK3 in den beiden anderen Katalysatoren K2, K3 nicht wesentlich ändern und im mageren Bereich verbleiben. In diesen Katalysatoreinheiten K2, K3 können dadurch sowohl unverbrannte Kohlenwasserstoffe und Kohlenmonoxid als auch das möglicherweise bei der Desulfatisierung des stromaufwärtigen NOx-Speicherkatalysators K1 entstehender Schwefelwasserstoff oxidiert werden. Alternativ zur gezeigten Sekundärluftzufuhr allein über den zweiten Leitungszweig L3 kann in dieser Betriebsphase mit im wesentlichen gleicher Wirkung eine Sekundärluftzufuhr nur über den dritten Leitungzweig L4 für den Dreiwege-Katalysator K3 oder eine solche über den zweiten und dritten Leitungszweig L3, L4 vorgesehen sein. These measures change the catalytic converter air ratio λ K1 in the upstream NO x storage catalytic converter K1 from a lean to a slightly rich value that promotes the desulfation process, while the catalytic converter air ratios λ K2 , λ K3 in the other two catalysts K2, K3 do not change significantly remain in the lean area. In these catalyst units K2, K3, both unburned hydrocarbons and carbon monoxide and also the hydrogen sulfide which may arise during the desulfation of the upstream NO x storage catalyst K1 can thereby be oxidized. As an alternative to the secondary air supply shown solely via the second line branch L3, a secondary air supply can be provided in this operating phase with essentially the same effect only via the third line branch L4 for the three-way catalytic converter K3 or via the second and third line branches L3, L4.

Die Dauer der Desulfatisierungsphase C für den stromaufwärtigen NOx-Speicherkatalysator wird mittels einer Modellrechnung bezüglich der Schwefelvergiftung ermittelt. In diese modellbasierte Schätzung des zu Beginn vorliegenden Schwefelgehalts im zu desorbierenden NOx-Speicherkatalysator gehen als maßgebende Einflußgrößen der verbrauchte Kraftstoff und dessen Schwefelgehalt sowie die Auswertung natürlicher Desulfatisierungsprozesse ein, wie sie gegebenenfalls während einer vorangegangenen Normalberiebs-Fahrphase mit warmgelaufenen Motor aufgetreten sein können, indem zeitweise die dafür günstigen Bedingungen vorgelegen haben. Dies ist z.B. bei Autobahn- und Vollast-Betriebsphasen der Fall. Zusätzlich oder alternativ zu dieser modellbasierten Schätzung kann eine sensorische Diagnose des NOx-Speicherzustands vorgesehen sein.The duration of the desulfation phase C for the upstream NO x storage catalytic converter is determined using a model calculation with regard to the sulfur poisoning. This model-based estimate of the sulfur content in the NO x storage catalytic converter to be desorbed at the beginning is used as the decisive influencing variables, the fuel consumed and its sulfur content, as well as the evaluation of natural desulfation processes, such as may have occurred during a previous normal operating driving phase with the engine warmed up, by at times the conditions were favorable. This is the case, for example, with freeway and full-load operating phases. In addition or as an alternative to this model-based estimate, a sensory diagnosis of the NO x storage state can be provided.

Sobald dann die erste Desulfatisierungsphase C für die ermittelte Dauer durchgeführt worden ist, wird auf die zweite Desulfatisierungsphase D umgeschaltet, in welcher primär der in Abgasströmungsrichtung nächste NOx-Speicherkatalysator K2 desulfatisiert wird. Hierzu wird die Sekundärluftzufuhr über den zweiten Leitungszweig L3 für diesen stromabwärtigen NOx-Speicherkatalysator K2 beendet, d.h. die zugehörige Kennlinie mL3 fällt auf null ab. Gleichzeitig wird spätestens jetzt mit der Zuführung von Sekundärluft über den dritten Leitungszweig L4 für den Dreiwege-Katalysator K3 begonnen, wie in Fig. 2 anhand einer zugehörigen, dritten Luftmassenkennlinie mL4 dargestellt. Das Motorluftverhältnis λM wird unverändert im leicht fetten Bereich belassen.As soon as the first desulfation phase C has been carried out for the determined duration, a switch is made to the second desulfation phase D, in which primarily the next NO x storage catalytic converter K2 in the exhaust gas flow direction is desulfated. For this purpose, the secondary air supply via the second line branch L3 for this downstream NO x storage catalytic converter K2 is ended, ie the associated characteristic curve m L3 drops to zero. At the same time, the supply of secondary air via the third line branch L4 for the three-way catalytic converter K3 is started at the latest, as shown in FIG. 2 on the basis of an associated third air mass characteristic m L4 . The engine air ratio λ M remains unchanged in the slightly rich range.

Durch diese Maßnahmen fällt das Katalysatorluftverhältnis λK2 für den nun zu desulfatisierenden NOx-Speicherkatalysator K2 vom vormals mageren in den leicht fetten Bereich ab, wie es für den Desulfatisierungsprozeß günstig ist. Das Katalysatorluftverhältnis λK3 im Dreiwege-Katalysator K3 bleibt hingegen im mageren Bereich, so daß dort weiterhin die Oxidation von unverbrannten Kohlenwasserstoffen, Kohlenmonoxid und gegebenenfalls bei der Desulfatisierung entstehendem Schwefelwasserstoff gewährleistet ist.As a result of these measures, the catalytic converter air ratio λ K2 for the NO x storage catalytic converter K2 now to be desulphated falls from the previously lean to the slightly rich range, as is favorable for the desulphation process. The catalytic converter air ratio λ K3 in the three-way catalytic converter K3, on the other hand, remains in the lean range, so that the oxidation of unburned hydrocarbons, carbon monoxide and, if appropriate, hydrogen sulfide formed during the desulfation is also ensured there.

Sobald dann die wiederum geeignet ermittelte Dauer der Desulfatisierungsphase D für den stromabwärtigen NOx-Speicherkatalysator K2 abgelaufen ist, wird die Verbrennungsmotoranlage für eine nächste Phase E auf Normalbetrieb umgestellt, d.h. auf kraftstoffverbrauchs- und motorleistungsoptimierten Betrieb. Das Motorluftverhältnis λM wird in diesem Normalbetrieb möglichst mager eingestellt. Im Motor dadurch entstehende Stickoxide werden von den NOx-Speicherkatalysatoren K1, K2 adsorbiert. Sobald deren NOx-Speicherkapazität erschöpft ist, werden sie in herkömmlicher Weise einem Desorptionsvorgang unterzogen, wozu bei Bedarf auch die Sekundärluftzufuhrmittel aktiviert werden können.As soon as the desulphation phase D for the downstream NO x storage catalytic converter K2, which in turn has been suitably determined, has elapsed, the internal combustion engine system is switched over to normal operation for a next phase E, ie to operation optimized for fuel consumption and engine power. The engine air ratio λ M is set as lean as possible in this normal operation. Nitrogen oxides generated in the engine are adsorbed by the NO x storage catalytic converters K1, K2. As soon as their NO x storage capacity is exhausted, they are subjected to a desorption process in a conventional manner, for which purpose the secondary air supply means can also be activated if necessary.

Es versteht sich, daß in der beschriebenen Weise auch mehr als zwei seriell hintereinanderliegende NOx-Speicherkatalysatoren oder andersartige schwefelanreichernde Abgasreinigungskomponenten desulfatisiert werden können.It goes without saying that more than two NO x storage catalysts or other types of sulfur-enriching exhaust gas purification components can be desulfated in the manner described.

Das erfindungsgemäße Betriebsverfahren kann im übrigen auch bei Fehlen einer Sekundärluftzuführung angewendet werden, sofern es die Abgasemissionen an unverbrannten Kohlenwasserstoffen und Kohlenmonoxid in der Kaltstartphase zulassen. Die jeweils geeigneten Betriebsbedingungen werden dann allein durch Betriebssteuerungsmaßnahmen am Motor 1 selbst und ohne Sekundärluftzuführung in den Abgasstrang eingestellt. Insbesondere wird der Motor während der Kaltstartphase mit einem fetten Abgasgemisch versorgt, so daß einerseits eine schnelle Katalysatoraufheizung und andererseits eine Entschwefelung der schwefelanreichernden Abgasreinigungskomponente erreicht wird.The operating method according to the invention can also be used Absence of a secondary air supply can be applied, provided it exhaust gas emissions from unburned hydrocarbons and Allow carbon monoxide in the cold start phase. The appropriate one Operating conditions are then determined solely by operational control measures on engine 1 itself and without secondary air supply set in the exhaust system. In particular, the Engine with a rich exhaust gas mixture during the cold start phase supplied so that on the one hand rapid catalyst heating and on the other hand a desulfurization of the sulfur-enriching Emission control component is reached.

Claims (9)

Verfahren zum Betrieb einer Verbrennungsmotoranlage, insbesondere eines Kraftfahrzeuges, die einen Verbrennungsmotor (1) mit zugehörigem Abgasstrang (2), eine im Abgasstrang angeordnete, schwefelanreicherne Abgasreinigungskomponente (K1, K2) und Mittel zur Desulfatisierung der schwefelanreichernden Abgasreinigungskomponente umfaßt, wobei der Betrieb der Verbrennungsmotoranlage zu vorgebbaren Zeitpunkten auf einen Desulfatisierungsmodus eingestellt wird,
dadurch gekennzeichnet, daß der Betrieb der Verbrennungsmotoranlage jeweils im Anschluß an eine Kaltstartaktivierung des Verbrennungsmotors vor Übergang in einen Normalbetriebsmodus auf den Desulfatisierungsmodus eingestellt wird. Method for operating an internal combustion engine system, in particular a motor vehicle, comprising an internal combustion engine (1) with an associated exhaust line (2), a sulfur-enriched exhaust gas cleaning component (K1, K2) arranged in the exhaust line and means for desulfating the sulfur-enriching exhaust gas cleaning component, wherein the operation of the internal combustion engine system is set to a desulfation mode at predeterminable times,
characterized in that the operation of the internal combustion engine system is set to the desulfation mode in each case following a cold start activation of the internal combustion engine before transition to a normal operating mode. Verfahren nach Anspruch 1, weiter
dadurch gekennzeichnet, daß
der Betrieb der Verbrennungsmotoranlage nach einer jeweiligen Motorkaltstartaktivierung zunächst auf einen Katalysatorheizmodus zur Aufheizung der schwefelanreichernden Abgasreinigungskomponente eingestellt und dann auf den Desulfatisierungsmodus umgestellt wird, wenn die Temperatur der schwefelanreichernden Abgasreinigungskomponente einen vorgebbaren Entschwefelungsmindestwert überschritten hat.The method of claim 1, further
characterized in that
the operation of the internal combustion engine system after a respective engine cold start activation is first set to a catalyst heating mode for heating the sulfur-enriching exhaust gas cleaning component and then switched to the desulfation mode when the temperature of the sulfur-enriching exhaust gas cleaning component has exceeded a predeterminable minimum desulfurization value. Verfahren nach Anspruch 2 zum Betrieb einer Verbrennungsmotoranlage, die des weiteren Mittel zur Sekundärluftzuführung an einer oder mehreren Stellen des Abgasstrangs (2) beinhaltet, weiter
dadurch gekennzeichnet, daß
im Katalysatorheizmodus Sekundärluft in die schwefelanreichernde Abgasreinigungskomponente oder den Abgasstrangabschnitt stromaufwärts davon zugeführt und diese Sekundärzuluftfuhr bei Umstellung auf den Desulfatisierungsmodus beendet wird.The method of claim 2 for operating an internal combustion engine system, which further includes means for supplying secondary air at one or more locations on the exhaust line (2)
characterized in that
in the catalyst heating mode, secondary air is fed into the sulfur-enriching exhaust gas purification component or the exhaust line section upstream thereof, and this secondary air supply is terminated when the desulfation mode is switched over. Verfahren nach einem der Ansprüche 1 bis 3 zum Betrieb einer Verbrennungsmotoranlage, die des weiteren Mittel zur Sekundärluftzuführung an einer oder mehreren Stellen des Abgasstrangs (2) und stromabwärts der schwefelanreichernden Abgasreinigungskomponente (K1, K2) eine Oxidationskatalysatoreinheit (K3) beinhaltet, weiter
dadurch gekennzeichnet, daß
im Desulfatisierungsmodus Sekundärluft in die Oxidationskatalysatoreinheit oder in den Abgasstrangabschnitt zwischen der schwefelanreichernden Abgasreinigungskomponente und der Oxidationskatalysatoreinheit zugeführt wird.Method according to one of claims 1 to 3 for operating an internal combustion engine system, which further includes means for supplying secondary air at one or more points of the exhaust line (2) and downstream of the sulfur-enriching exhaust gas cleaning component (K1, K2) an oxidation catalyst unit (K3)
characterized in that
in the desulfation mode, secondary air is fed into the oxidation catalyst unit or into the exhaust line section between the sulfur-enriching exhaust gas purification component and the oxidation catalyst unit. Verfahren nach Anspruch 3 oder 4 zum Betrieb einer Verbrennungsmotoranlage, die des weiteren Mittel zur Sekundärluftzuführung an einer oder mehreren Stellen des Abgasstrangs (2) beinhaltet und bei der die schwefelanreichernde Abgasreinigungskomponente mehrere seriell in den Abgasstrang geschaltete Abgasreinigungseinheiten (K1, K2) umfaßt, weiter
dadurch gekennzeichnet, daß
die schwefelanreichernden Abgasreinigungseinheiten (K1, K2) im Desulfatisierungsmodus in Abgasströmungsrichtung nacheinander in einer jeweils zugehörigen Desulfatisierungsphase desulfatisiert werden, wobei während der jeweiligen Desulfatisierungsphase Sekundärluft in den Abgasstrang ausschließlich an einer oder mehreren Stellen stromabwärts der schwefelanreichernden Abgasreinigungseinheit, die momentan desulfatisiert wird, zugeführt wird.Method according to Claim 3 or 4 for operating an internal combustion engine system, which further includes means for supplying secondary air at one or more points on the exhaust line (2) and in which the sulfur-enriching exhaust gas cleaning component comprises a plurality of exhaust gas cleaning units (K1, K2) connected in series in the exhaust line
characterized in that
the sulfur-enriching exhaust gas purification units (K1, K2) in the desulfation mode in the exhaust gas flow direction are successively desulfated in a respectively associated desulfation phase, with secondary air being fed into the exhaust line exclusively at one or more points downstream of the sulfur-enriching exhaust gas purification unit which is currently being desulfated during the respective desulfation phase. Verfahren nach einem der Ansprüche 2 bis 5, weiter
dadurch gekennzeichnet, daß
das Luft-Kraftstoff-Verhältnis (λM) des den Verbrennungsmotor (1) zugeführten Luft-Kraftstoff-Gemischs im Desulfatisierungsmodus kraftstoffreicher als der stöchiometrische Wert und kraftstoffärmer als im Katalysatorheizmodus gewählt wird.Method according to one of claims 2 to 5, further
characterized in that
the air-fuel ratio (λ M ) of the air-fuel mixture supplied to the internal combustion engine (1) is selected to be richer in fuel than the stoichiometric value and lower in fuel than in the catalyst heating mode in the desulfation mode. Verfahren nach einem der Ansprüche 1 bis 6, weiter
dadurch gekennzeichnet, daß
die Dauer des jeweiligen Desulfatisierungsmodus aus einer sensorischen Überwachung des Speicherzustands der schwefelanreichernden Abgasreinigungskomponente und/oder einer modellbasierten Schätzung der gespeicherten Schwefelmenge ermittelt wird, wobei die Schätzung wenigstens in Abhängigkeit vom verbrauchten Kraftstoff und dessen Schwefelgehalt sowie von während eines vorangegangenen Normalbetriebsmodus eventuell stattgefundenen, natürlichen Desulfatisierungsprozessen erfolgt.Method according to one of claims 1 to 6, further
characterized in that
the duration of the respective desulfation mode is determined from a sensory monitoring of the storage state of the sulfur-enriching exhaust gas cleaning component and / or from a model-based estimate of the stored amount of sulfur, the estimate being made at least as a function of the fuel consumed and its sulfur content and of natural desulfation processes that may have taken place during a previous normal operating mode . Verbrennungsmotoranlage, insbesondere für ein Kraftfahrzeug, mit einem Verbrennungsmotor (1) mit zugehörigem Abgasstrang (2), einer im Abgasstrang angeordneten, schwefelanreichernden Abgasreinigungskomponente (K1, K2) und Mitteln zur Desulfatisierung der schwefelanreichernden Abgasreinigungskomponente, die Sekundärluftzufuhrmittel umfassen,
dadurch gekennzeichnet, daß die schwefelanreichernde Abgasreinigungskomponente wenigstens zwei seriell in den Abgasstrang geschaltete Abgasreinigungseinheiten (K1, K2) beinhaltet und die Sekundärluftzufuhrmittel je einen eigenen Sekundärluftzufuhrzweig (L2, L3) für die schwefelanreichernden Abgasreinigungseinheiten aufweisen. Internal combustion engine system, in particular for a motor vehicle, with an internal combustion engine (1) with associated exhaust line (2), a sulfur-enriching exhaust gas cleaning component (K1, K2) arranged in the exhaust line and Means for desulfating the sulfur-enriching exhaust gas purification component, comprising secondary air supply means,
characterized in that the sulfur-enriching exhaust gas cleaning component contains at least two exhaust gas cleaning units (K1, K2) connected in series in the exhaust line and the secondary air supply means each have their own secondary air supply branch (L2, L3) for the sulfur-enriching exhaust gas purification units. Verbrennungsmotoranlage, insbesondere nach Anspruch 8, mit einem Verbrennungsmotor (1) mit zugehörigem Abgasstrang (2), einer im Abgasstrang angeordneten, schwefelanreichernden Abgasreinigungskomponente (K1, K2) und Mitteln zur Desulfatisierung der schwefelanreichernden Abgasreinigungskomponente, die Sekundärluftzufuhrmittel umfassen,
dadurch gekennzeichnet, daß stromabwärts der schwefelanreichernden Abgasreinigungskomponente (K1, K2) eine Oxidationskatalysatoreinheit (K3) vorgesehen ist und die Sekundärluftzufuhrmittel mindestens je einen Sekundärluftzufuhrzweig (L2, L3; L4) für die schwefelanreichernde Abgasreinigungskomponente (K1, K2) einerseits und die Oxidationskatalysatoreinheit (K3) andererseits aufweisen. Internal combustion engine system, in particular according to claim 8, with an internal combustion engine (1) with associated exhaust line (2), a sulfur-enriching exhaust gas cleaning component (K1, K2) arranged in the exhaust line and Means for desulfating the sulfur-enriching exhaust gas purification component, comprising secondary air supply means,
characterized in that an oxidation catalyst unit (K3) is provided downstream of the sulfur-enriching exhaust gas cleaning component (K1, K2) and the secondary air supply means each have at least one secondary air supply branch (L2, L3; L4) for the sulfur-enriching exhaust gas cleaning component (K1, K2) on the one hand and the oxidation catalyst unit (K3) on the other.
EP99114565A 1998-09-17 1999-07-24 Method of operation of an internal combustion engine with sulphur accumulating exhaust gas purification components and an internal combustion engine operable therewith Expired - Lifetime EP0987408B1 (en)

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US6293094B1 (en) 2001-09-25
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EP0987408B1 (en) 2004-09-08
DE59910440D1 (en) 2004-10-14

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