EP0987408B1 - Method of operation of an internal combustion engine with sulphur accumulating exhaust gas purification components and an internal combustion engine operable therewith - Google Patents

Method of operation of an internal combustion engine with sulphur accumulating exhaust gas purification components and an internal combustion engine operable therewith Download PDF

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Publication number
EP0987408B1
EP0987408B1 EP99114565A EP99114565A EP0987408B1 EP 0987408 B1 EP0987408 B1 EP 0987408B1 EP 99114565 A EP99114565 A EP 99114565A EP 99114565 A EP99114565 A EP 99114565A EP 0987408 B1 EP0987408 B1 EP 0987408B1
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EP
European Patent Office
Prior art keywords
exhaust gas
gas purification
internal combustion
combustion engine
sulphur
Prior art date
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Expired - Lifetime
Application number
EP99114565A
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German (de)
French (fr)
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EP0987408A3 (en
EP0987408A2 (en
Inventor
Jürgen Dr. Schmidt
Gerd Tiefenbacher
Anton Waltner
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Daimler AG
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DaimlerChrysler AG
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Publication of EP0987408A3 publication Critical patent/EP0987408A3/en
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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
    • F01N3/10—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 operable with such a method engine system according to the preamble of claim 8.
  • Systems of this type are used in particular in motor vehicles and include an exhaust gas cleaning component in which during of the plant enriches sulfur contained in the fuel.
  • Such sulfur-enriching exhaust gas purification components may in particular be nitric oxide (NO x ) storage catalysts or so-called sulfur traps.
  • the sulfur enriching emission control component requires desulphation to free it from the accumulated sulphurous sulphate.
  • sulfur poisoning of NO x storage catalysts reduces their storage capacity.
  • the desulfation preferably proceeds at elevated exhaust gas temperatures and rich exhaust gas compositions.
  • EP 0 636 770 A1 proposes converting 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 required, additionally an electric heater for the NO x storage catalytic converter to activate.
  • the respective Desulfatticiansphase is for a predetermined period of, for example, 10 min. maintained.
  • the setting of a sufficiently rich engine air ratio is accompanied by a metered addition of secondary air into the exhaust line upstream of the NO x storage catalytic converter.
  • a control and not only control of the catalyst air ratio, ie, the air / fuel ratio of the NO x storage-flowing through the exhaust gas may be provided, and the catalyst temperature may be set to a desired value.
  • the object of the invention is a method and an internal combustion engine system specify with which a sulfur-enriching Emission control component as fuel-efficient and odorless as well as avoiding disturbances of the Engine operation can be desulfated.
  • the invention solves this problem by providing a Operating method with the features of claim 1 and an internal combustion engine system with the features of the claim 8th.
  • the method of claim 1 is in each case at a Cold start a desulfating triggered in which the operation of the internal combustion engine system on the corresponding Desulfatticiansmodus is set, wherein the motor vehicle approached before setting the desulfating mode becomes.
  • the combustion engine will not be primary anyway operated according to fuel consumption minimizing criteria, such as for a normal operation mode with warmed up engine application can find because e.g. first in a catalyst heating mode Attempts are made to use existing exhaust gas cleaning components, in particular one or more catalytic converter units, if possible quickly bring to operating temperature.
  • the internal combustion engine is not yet in the so-called operated fuel-efficient stratified charge, and appropriate catalyst heating measures are also in engines with direct injection appropriate.
  • the engine catalytic converter heating measures for example, the setting of a rich engine air ratio include, as far as possible with the motor measures for desulfating the sulfur-enriching Exhaust gas purifying component correspond, arises by the procedure according to the invention no appreciably higher Fuel consumption compared to a plant operation without Desulfatticiansvortician.
  • a further developed according to claim 4 operating method is suitable itself for internal combustion engine plants, which in the exhaust line downstream sulfur-enriching emission control component Oxidation catalyst unit, i. such with oxidizing Function, such as a three-way catalyst., Have.
  • Oxidation catalyst unit i. such with oxidizing Function, such as a three-way catalyst., Have.
  • Oxidation catalyst unit i. such with oxidizing Function, such as a three-way catalyst., Have.
  • This process variant is during desulfation Secondary air in the exhaust line for the oxidation catalyst unit fed, i. directly into this or into the exhaust section between her and the currently desorbing, sulfur enriching emission control component. This allows oxidation of both carbon monoxide and unburned hydrocarbons as well as possibly in the desulfurization resulting hydrogen sulfide.
  • a further developed according to claim 5 operating method is suitable For internal combustion engine systems with two or more serial one after the other, sulfur enriching waste gas purification units.
  • the sulfur-enriching exhaust gas purification units in desulfating mode one after the other Desulfurized, in one of the exhaust gas flow direction corresponding Sequence.
  • This desulfating process is by accompanied by a secondary air supply, with the secondary air respectively only downstream of the sulfur-enriching one Exhaust gas purification unit is fed into the exhaust system, the is being desulfurized.
  • the method according to a cold start activation the catalyst heating mode and then includes the desulfating mode is advantageously the engine air ratio in Desulfatticiansmodus set slightly high, i. fuel-rich than the stoichiometric Ratio, but with less fuel than in the catalyst heating mode, which has a positive effect on fuel consumption.
  • the internal combustion engine system according to claim 8 includes at least two serially connected in the exhaust line, sulfur-enriching Exhaust gas purification units and secondary air supply means, each have their own secondary air supply branch for the sulfur-enriching Exhaust gas purification units included.
  • This is a targeted, procedural secondary air supply to the respective sulfur enriching emission control component possible to For example, to bring these faster to operating temperature or in the supplied exhaust gas contained hydrocarbons, carbon monoxide and / or hydrogen sulfide to oxidize.
  • the internal combustion engine system includes downstream the sulfur enriching emission control component, the comprise one or more serial exhaust gas purification units can, an oxidation catalyst unit.
  • the intended secondary air supply means include adjacent to one or more secondary air supply branches for the sulfur-enriching emission control component additionally a separate secondary air supply branch for the oxidation catalyst unit, so that in this example during a desulfurization process in the upstream, Sulfur enriching emission control component educated Hydrogen sulfide can be oxidized.
  • the exhaust line 2 is associated with an exhaust gas purification system comprising a sulfur-enriching exhaust gas purification component in the form of two series-connected NO x storage K1, K2 and a downstream three-way catalyst K3, which has, inter alia, an oxidizing function and thus acts as an oxidation catalyst 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 catalysts K1, K2 serve to periodically adsorb nitrogen oxides contained in the exhaust gas and desorb for the purpose of conversion, for example by exhaust gas recirculation or catalytic reduction, as is known per se and therefore no further explanation and drawings requirement.
  • the exhaust gas purification system further includes desulfating agent in order to be able to free the NO x storage catalysts K 1, K 2 from the enriched sulfur, more specifically from the sulfate acting poisonous for the nitrogen oxide adsorption function.
  • the secondary air line L1 branches downstream of the pump 5 into three line branches L2, L3, L4, of which a first branch L2 into a first exhaust line section 2a between the engine 1 and the upstream NO x storage catalyst K1, a second leg L3 in a second exhaust line section 2b between the two NO x storage K1, K2 and a third leg L4 in a third Abgasasstangabites 2c between the downstream NO x storage K2 and the three-way catalyst K3 open.
  • 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, preferably as appropriate Control part in software or hardware integrated in an engine control unit is that the engine 1 and the other components of Emission control system 2 controls.
  • a desulfating control unit preferably as appropriate Control part in software or hardware integrated in an engine control unit is that the engine 1 and the other components of Emission control system 2 controls.
  • the relevant components are not shown in Fig. 1, this can the skilled person common, conventional components are used.
  • the control units are to be designed so that they entire internal combustion engine system according to the explained below Can operate procedures. The implementation of these operating procedure steps for example, in the engine control unit is the expert with knowledge of these steps without further possible, so that it will not be discussed here will need.
  • FIG. 2 illustrates in diagrammatic form an example of the operating method according to the invention for the internal combustion engine system of FIG. 1.
  • the method example schematically shows the time-dependent operation in the case of a cold start.
  • the vehicle speed v Fzg , the exhaust gas temperature T, the air / fuel ratio ⁇ and the secondary air mass mL, ie the secondary air quantity fed into the exhaust gas line 2 by the secondary air supply means, are reproduced in their time profile in the diagram of FIG. 2 in four superimposed diagrams.
  • a first, very short phase A 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 in a subsequent phase B is set to a catalyst heating mode.
  • the fastest possible increase in the exhaust gas temperature is effected by appropriate engine control measures and secondary air supply to bring the exhaust gas purification system, especially the exhaust gas catalysts K1, K2, K3, quickly to operating temperature.
  • the air / fuel mixture supplied to the engine 1 is set to be rich, ie to a lambda value of less than one, as shown by a corresponding solid curve ⁇ 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 through, first secondary air characteristic m L2 .
  • the two other secondary air line branches L3, L4 remain closed.
  • the secondary air feed into the exhaust line section 2a emerging 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 shown in FIG dashed characteristic ⁇ K1 , the solid curve ⁇ K2 and the dash-dotted curve ⁇ K3 shown. As further illustrated in FIG.
  • the exhaust gas temperature T K1 in front of the upstream NO x storage catalytic converter increases very rapidly through these measures in the catalyst heating mode and reaches one end for carrying out a heating phase B subsequent Desulfatticiansphase sufficient desulfurization temperature of typically about 550 ° C or more.
  • the exhaust gas temperature T K2 in front of the downstream NO x storage catalyst and the exhaust gas temperature T K3 in front of the three-way catalyst K3 increase to a slightly lesser extent, the three-way catalyst K3 at the end of the heating phase B its light-off temperature for the oxidation of unburned Hydrocarbons and carbon monoxide has reached.
  • v F the vehicle is started in the last half of the heating phase B.
  • the catalyst heating mode B is switched to a desulfurization mode which includes two successive desulfurization phases C, D.
  • the engine operation is primarily adjusted to the desulfation of the upstream NO x storage catalyst K1.
  • the supply of secondary air via the first line branch L2 is turned off to this NO x storage catalytic converter K1, ie the associated air mass characteristic m L2 drops to zero.
  • L3 secondary air is via the second line branch fed into the exhaust section 2b before the downstream NOx storage catalytic converter K2 as appropriate, drawn dashed by the rise of a second secondary air characteristic m L3 to detect.
  • the engine air ratio ⁇ M is raised to a value only slightly below the stoichiometric value, ie the engine 1 is operated slightly rich at the transition to the desulfurization mode.
  • the catalyst air ratio ⁇ K1 in the upstream NO x storage catalyst K1 changes from a lean to a slightly rich, the Desulfatticiansvorgang promotional value, while the catalyst air ratios ⁇ K2 , ⁇ K3 in the other two catalysts K2, K3 does not change significantly and remain in the lean area.
  • this catalyst units K2, K3 can thereby be oxidized both unburned hydrocarbons and carbon monoxide and possibly formed in the desulfurization of the upstream NO x storage K1 hydrogen sulfide.
  • 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 catalyst K3 or one via the second and third line branch L3, L4.
  • the duration of the desulfurization phase C for the upstream NO x storage catalyst is determined by means of a model calculation relating to sulfur poisoning.
  • this model-based estimate of the sulfur present at the beginning of the desorbing NO x storage catalytic converter are the decisive factors of the spent fuel and its sulfur content and the evaluation of natural Desulfatmaschinesvone, as may have occurred during a previous Normalberiebs driving phase with warmed-up engine by at times the favorable conditions have existed. This is the case, for example, for motorway and full-load operating phases.
  • a sensory diagnosis of the NO x storage state may be provided.
  • the system switches to the second desulfurization phase D, in which primarily the next NO x storage catalyst K 2 in the exhaust gas flow direction is desulfated.
  • the secondary air supply via the second line branch L3 for this downstream NO x storage catalyst K2 is terminated, ie the associated characteristic 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 now, as shown in FIG. 2 on the basis of an associated, third air mass characteristic m L4 .
  • the engine-engine air ratio ⁇ M is left unchanged in the slightly rich range.
  • the catalyst air ratio ⁇ K2 for the NO x storage catalytic converter K 2 which is now to be desulfated, drops from the former lean to the slightly rich region, as is favorable for the desulfurization process.
  • the internal combustion engine system is switched over to normal operation for a next phase E, ie to fuel consumption and engine power-optimized operation.
  • the Mo engine air ratio ⁇ M is set as lean as possible in this normal operation.
  • they are subjected to a desorption process in a conventional manner, to which end the secondary air supply means can also be activated if required.
  • the operating method according to the invention can also be applied to Absence of a secondary air supply to be applied, if it Exhaust emissions of unburned hydrocarbons and Allow carbon monoxide in the cold start phase.
  • the appropriate ones Operating conditions are then only by operational control measures on the engine 1 itself and without secondary air supply set in the exhaust system.
  • the Engine during the cold start phase with a rich exhaust gas mixture supplied so that on the one hand a fast Katalysatoretzloomung and on the other hand, a desulfurization of the sulfur-enriching Emission control component is achieved.

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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)

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 operable with such a method engine system according to the preamble of claim 8. Systems of this type are used in particular in motor vehicles and include an exhaust gas cleaning component in which during of the plant enriches sulfur contained in the fuel. Such sulfur-enriching exhaust gas purification components may in particular be nitric 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 Abgaszusammensetzungen abläuft.From time to time, the sulfur enriching emission control component requires desulphation to free it from the accumulated sulphurous sulphate. 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 preferably proceeds 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.Traditionally, desulphurisation operations are performed during ongoing engine operation whenever the sulfur content in the sulfur enriching exhaust gas purifying component has exceeded a certain level. This is assumed, for example, in the case of a NO x storage catalytic converter if its storage capacity noticeably decreases. In processes of this kind, as described in the published patent application EP 0 636 770 A1 and German Patent Application No. 197 47 222.2, this decreasing storage capacity is recognized by the fact that shorten the adsorption and desorption phases. The duration of the adsorption phases can be monitored by a NO x sensor positioned downstream of the NO x storage catalyst and the duration of the desorption phases by a lambda probe positioned there.

Zur Durchführung der Desulfatisierungsphasen wird in der genannten EP 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.In order to carry out the desulfurization phases, EP 0 636 770 A1 proposes converting 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 required, additionally an electric heater for the NO x storage catalytic converter to activate. The respective Desulfatisierungsphase is for a predetermined period of, for example, 10 min. maintained. In the method of said German Patent Application No. 197 47 222.2, the setting of a sufficiently rich engine air ratio is accompanied by a metered addition of secondary air into the exhaust line upstream of the NO x storage catalytic converter. In this case, a control and not only control of the catalyst air ratio, ie, the air / fuel ratio of the NO x storage-flowing through the exhaust gas may be provided, and the catalyst temperature may 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.In the published patent application DE 195 22 165 A1, another such method with periodic desulfurization of a NO x storage catalytic converter during operation of the engine with recognized slackening of its storage capacity and a related internal combustion engine system is known, there for activating a respective Desulfatisierungsphase to a richer engine air ratio and a later Switched ignition timing for the respective engine cylinder and also secondary air is fed into the exhaust line upstream of the NO x storage catalytic converter. This is preferably done so that during the desulfurization, which is maintained for a predetermined period of time, the catalyst temperature is adjusted to a desired, increased setpoint.

Aus der Offenlegungsschrift JP 09291 814 A ist es bekannt, eine Desulfatisierung eines NOx-Speicherkatalysators im Anschluss an einen Start des Verbrennungsmotors vorzunehmen. Unmittelbar nachdem von hierzu vorgesehenen Mitteln festgestellt wird, dass ein Start des Verbrennungsmotors erfolgt ist, wird hierzu der NOx-Speicherkatalysators aufgeheizt und mit einem an Kraftstoff angereicherten Abgas versorgt.From the published patent application JP 09291 814 A it is known to carry out a desulfating of a NO x storage catalytic converter following a start of the internal combustion engine. Immediately after it has been determined by means provided for this purpose that a start of the internal combustion engine has taken place, the NO x storage catalytic converter is heated for this purpose and supplied with a fuel-enriched exhaust gas.

Aufgabe der Erfindung ist es, ein Verfahren und eine Verbrennungsmotoranlage anzugeben, mit welchen eine schwefelanreichernde Abgasreinigungskomponente möglichst kraftstoffsparend und geruchsneutral sowie unter Vermeidung von Störungen des Motorbetriebs desulfatisiert werden kann.The object of the invention is a method and an internal combustion engine system specify with which a sulfur-enriching Emission control component as fuel-efficient and odorless as well as avoiding disturbances of the Engine operation can be desulfated.

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.The invention solves this problem by providing a Operating method with the features of claim 1 and an internal combustion engine system with the features of the claim 8th.

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, wobei das Kraftfahrzeug vor der Einstellung des Desulfatisierungsmodus angefahren 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 is in each case at a Cold start a desulfating triggered in which the operation of the internal combustion engine system on the corresponding Desulfatisierungsmodus is set, wherein the motor vehicle approached before setting the desulfating mode becomes. In the subsequent to a cold start activation period In most cases, the combustion engine will not be primary anyway operated according to fuel consumption minimizing criteria, such as for a normal operation mode with warmed up engine application can find because e.g. first in a catalyst heating mode Attempts are made to use existing exhaust gas cleaning components, in particular one or more catalytic converter units, if possible quickly bring to operating temperature. This can For example, the internal combustion engine is not yet in the so-called operated fuel-efficient stratified charge, and appropriate catalyst heating measures are also in engines with direct injection appropriate. Since the engine catalytic converter heating measures, for example, the setting of a rich engine air ratio include, as far as possible with the motor measures for desulfating the sulfur-enriching Exhaust gas purifying component correspond, arises by the procedure according to the invention no appreciably higher Fuel consumption compared to a plant operation without Desulfatisierungsvorgänge. Because the time intervals to those at the latest a next Desulfatisierungsvorgang necessary is typically significantly larger than the time intervals of successive ones Cold starts are enough, the cold start Desulfatisierungsphasen in general to achieve a timely and adequate desulfurization without additional desulfurization processes with warmed-up engine necessary. This will not normal engine operation disturbed and an 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 according to claim 2 method is after the activation of a cold engine start the operation of the internal combustion engine system initially set to a catalyst heating mode, to the temperature of the sulfur enriching emission control component a predeterminable desulphurisation minimum value exceeds, then the operation on the Desulfatisierungsmodus is converted. The initial catalyst heating mode allows a very quick achievement of sufficient Desulfurization temperature for the exhaust gas purification component to be desulfated. In a further embodiment of this measure may according to claim 3 during the Katalysatorheizmodus secondary air in the sulfur enriching emission control component or upstream of which are fed into the exhaust line, which in conjunction with the choice of a rich engine air ratio the exhaust gas temperature can increase rapidly. at Changing to the desulfating mode, this secondary air supply 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, wie z.B. einen Dreiwege-Katalysator., aufweisen. 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.A further developed according to claim 4 operating method is suitable itself for internal combustion engine plants, which in the exhaust line downstream sulfur-enriching emission control component Oxidation catalyst unit, i. such with oxidizing Function, such as a three-way catalyst., Have. According to this process variant is during desulfation Secondary air in the exhaust line for the oxidation catalyst unit fed, i. directly into this or into the exhaust section between her and the currently desorbing, sulfur enriching emission control component. This allows oxidation of both carbon monoxide and unburned hydrocarbons as well as possibly in the desulfurization resulting hydrogen sulfide.

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 Abgasströmungsrichtung 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.A further developed according to claim 5 operating method is suitable For internal combustion engine systems with two or more serial one after the other, sulfur enriching waste gas purification units. According to the method, the sulfur-enriching exhaust gas purification units in desulfating mode one after the other Desulfurized, in one of the exhaust gas flow direction corresponding Sequence. This desulfating process is by accompanied by a secondary air supply, with the secondary air respectively only downstream of the sulfur-enriching one Exhaust gas purification unit is fed into the exhaust system, the is being desulfurized. This is on the one hand an undesirable Secondary air supply to the exhaust gas purification unit, the desulfurization is avoided and, on the other hand, oxidation of carbon monoxide, unburned hydrocarbons and in the desulfurization possibly arising hydrogen sulfide 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 includes the desulfating mode is advantageously the engine air ratio in Desulfatisierungsmodus set slightly high, i. fuel-rich than the stoichiometric Ratio, but with less fuel than in the 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 according to claim 7 method is the Duration of the respective Desulfatisierungsmodus from a sensory Monitoring the sulfur storage state of sulfur-enriching Emission control component or a model-based Estimate determined. In such an estimate, besides the consumed fuel quantity and the sulfur content of the fuel also occurring in the meantime natural desulphation processes Consideration. Among them are such desulfating processes to understand that when the engine has warmed up Periods take place in which due to the current engine operating condition in the sulfur enriching emission control component desulfating promote conditions prevail, in particular sufficiently high temperature and sufficiently rich air / fuel ratio the exhaust gas, such as at motorway 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 Abgasreinigungseinheiten 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 serially connected in the exhaust line, sulfur-enriching Exhaust gas purification units and secondary air supply means, each have their own secondary air supply branch for the sulfur-enriching Exhaust gas purification units included. This is a targeted, procedural secondary air supply to the respective sulfur enriching emission control component possible to For example, to bring these faster to operating temperature or in the supplied exhaust gas contained hydrocarbons, carbon monoxide and / or hydrogen sulfide to oxidize.

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 emission control component, the comprise one or more serial exhaust gas purification units can, an oxidation catalyst unit. The intended secondary air supply means include adjacent to one or more secondary air supply branches for the sulfur-enriching emission control component additionally a separate secondary air supply branch for the oxidation catalyst unit, so that in this example during a desulfurization process in the upstream, Sulfur enriching emission control component educated 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 illustrated in the drawings and will be described below. Hereby show:
Fig. 1
a schematic block diagram of an internal combustion engine system and
Fig. 2
3 is a schematic operational flowchart of a method for operating the internal combustion engine system of 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 may be provided in particular for a motor vehicle, includes an internal combustion engine 1, to which an exhaust gas line 2 adjoins on the output side. The exhaust line 2 is associated with an exhaust gas purification system comprising a sulfur-enriching exhaust gas purification component in the form of two series-connected NO x storage K1, K2 and a downstream three-way catalyst K3, which has, inter alia, an oxidizing function and thus acts as an oxidation catalyst 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 catalysts K1, K2 serve to periodically adsorb nitrogen oxides contained in the exhaust gas and desorb for the purpose of conversion, for example by exhaust gas recirculation or catalytic reduction, as is known per se and therefore no further explanation and drawings 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 further includes desulfating agent in order to be able to free the NO x storage catalysts K 1, K 2 from the enriched sulfur, more specifically from the sulfate acting poisonous for the nitrogen oxide adsorption function. The secondary air line L1 branches downstream of the pump 5 into three line branches L2, L3, L4, of which a first branch L2 into a first exhaust line section 2a between the engine 1 and the upstream NO x storage catalyst K1, a second leg L3 in a second exhaust line section 2b between the two NO x storage K1, K2 and a third leg L4 in a third Abgasasstangabschnitt 2c between the downstream NO x storage K2 and the three-way catalyst K3 open. 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, preferably as appropriate Control part in software or hardware integrated in an engine control unit is that the engine 1 and the other components of Emission control system 2 controls. As far as the relevant components are not shown in Fig. 1, this can the skilled person common, conventional components are used. there Only the control units are to be designed so that they entire internal combustion engine system according to the explained below Can operate procedures. The implementation of these operating procedure steps for example, in the engine control unit is the expert with knowledge of these steps without further possible, so that it will not be discussed here will need.

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.FIG. 2 illustrates in diagrammatic form an example of the operating method according to the invention for the internal combustion engine system of FIG. 1. The method example schematically shows the time-dependent operation in the case of a cold start. The vehicle speed v Fzg , the exhaust gas temperature T, the air / fuel ratio λ and the secondary air mass mL, ie the secondary air quantity fed into the exhaust gas line 2 by the secondary air supply means, are reproduced in their time profile in the diagram of FIG. 2 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, very short phase A, 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 a cold engine start, the operation in a subsequent phase B is set to a catalyst heating mode. In this, the fastest possible increase in the exhaust gas temperature is effected by appropriate engine control measures and secondary air supply to bring the exhaust gas purification system, especially the exhaust gas catalysts K1, K2, K3, quickly to operating temperature. For this purpose, the air / fuel mixture supplied to the engine 1 is set to be rich, ie to a lambda value of less than one, as shown by a corresponding solid curve 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 through, first secondary air characteristic m L2 . The two other 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 feed into the exhaust line section 2a emerging 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 shown in FIG dashed characteristic λ K1 , the solid curve λ K2 and the dash-dotted curve λ K3 shown. As further illustrated in FIG. 2 by means of corresponding temperature characteristics T K1 , T K2 and T K3 , the exhaust gas temperature T K1 in front of the upstream NO x storage catalytic converter increases very rapidly through these measures in the catalyst heating mode and reaches one end for carrying out a heating phase B subsequent Desulfatisierungsphase sufficient desulfurization temperature of typically about 550 ° C or more. At the same time, the exhaust gas temperature T K2 in front of the downstream NO x storage catalyst and the exhaust gas temperature T K3 in front of the three-way catalyst K3 increase to a slightly lesser extent, the three-way catalyst K3 at the end of the heating phase B its light-off temperature for the oxidation of unburned Hydrocarbons and carbon monoxide has reached. As can be seen from a speed characteristic v F , the vehicle is started in the last half of the 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 to operating temperature in this way, the catalyst heating mode B is switched to a desulfurization mode which includes two successive desulfurization phases C, D. In the first desulfurization phase C, the engine operation is primarily adjusted to the desulfation of the upstream NO x storage catalyst K1. For this purpose, the supply of secondary air via the first line branch L2 is turned off to this NO x storage catalytic converter K1, ie the associated air mass characteristic m L2 drops to zero. At the same time, L3 secondary air is via the second line branch fed into the exhaust section 2b before the downstream NOx storage catalytic converter K2 as appropriate, drawn dashed by the rise of a second secondary air characteristic m L3 to detect. The engine air ratio λ M is raised to a value only slightly below the stoichiometric value, ie the engine 1 is operated slightly rich at the transition to the desulfurization mode.

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. By these measures, the catalyst air ratio λ K1 in the upstream NO x storage catalyst K1 changes from a lean to a slightly rich, the Desulfatisierungsvorgang promotional value, while the catalyst air ratios λ K2 , λ K3 in the other two catalysts K2, K3 does not change significantly and remain in the lean area. In this catalyst units K2, K3 can thereby be oxidized both unburned hydrocarbons and carbon monoxide and possibly formed in the desulfurization of the upstream NO x storage K1 hydrogen sulfide. As an alternative to the shown secondary air supply alone 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 catalyst K3 or one via the second and third line branch 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 desulfurization phase C for the upstream NO x storage catalyst is determined by means of a model calculation relating to sulfur poisoning. In this model-based estimate of the sulfur present at the beginning of the desorbing NO x storage catalytic converter are the decisive factors of the spent fuel and its sulfur content and the evaluation of natural Desulfatisierungsprozesse, as may have occurred during a previous Normalberiebs driving phase with warmed-up engine by at times the favorable conditions have existed. This is the case, for example, for motorway and full-load operating phases. In addition or as an alternative to this model-based estimation, a sensory diagnosis of the NO x storage state may 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 Motor-Motorluftverhältnis λM wird unverändert im leicht fetten Bereich belassen.As soon as the first desulfurization phase C has been carried out for the determined duration, the system switches to the second desulfurization phase D, in which primarily the next NO x storage catalyst K 2 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 catalyst K2 is terminated, ie the associated characteristic 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 now, as shown in FIG. 2 on the basis of an associated, third air mass characteristic m L4 . The engine-engine air ratio λ M is left 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 catalyst air ratio λ K2 for the NO x storage catalytic converter K 2, which is now to be desulfated, drops from the former lean to the slightly rich region, as is favorable for the desulfurization process. The catalyst air ratio λ K3 in the three-way catalyst K3, however, remains in the lean range, so that there further, the oxidation of unburned hydrocarbons, carbon monoxide and optionally formed in the desulfurization hydrogen sulfide is ensured.

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 Mo-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 again suitably ascertained duration of the desulfurization phase D for the downstream NO x storage catalytic converter K 2 has elapsed, the internal combustion engine system is switched over to normal operation for a next phase E, ie to fuel consumption and engine power-optimized operation. The Mo engine air ratio λ M is set as lean as possible in this normal operation. In the engine resulting nitrogen oxides are adsorbed by the NO x storage catalysts K1, K2. As soon as their NO x storage capacity is exhausted, they are subjected to a desorption process in a conventional manner, to which end the secondary air supply means can also be activated if required.

Es versteht sich, daß in der beschriebenen Weise auch mehr als zwei seriell hintereinanderliegende NOx-Speicherkatalysatoren oder andersartige schwefelanreichernde Abgasreinigungskomponenten desulfatisiert werden können.It is understood that in the manner described, more than two series-connected NO x storage catalysts or other sulfur-enriching exhaust gas purification components can be desulfated.

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.Incidentally, the operating method according to the invention can also be applied to Absence of a secondary air supply to be applied, if it Exhaust emissions of unburned hydrocarbons and Allow carbon monoxide in the cold start phase. The appropriate ones Operating conditions are then only by operational control measures on the engine 1 itself and without secondary air supply set in the exhaust system. In particular, the Engine during the cold start phase with a rich exhaust gas mixture supplied, so that on the one hand a fast Katalysatoraufheizung and on the other hand, a desulfurization of the sulfur-enriching Emission control component is achieved.

Claims (9)

  1. Method for the operation of an internal combustion engine system of a motor vehicle, comprising an internal combustion engine (1) with an associated exhaust train (2), a sulphur accumulating exhaust gas purification component located in the exhaust train with at least one sulphur accumulating exhaust gas purification unit (K1, K2) and means for the desulphatisation of the sulphur accumulating exhaust gas purification component, whereby the operation of the internal combustion engine system is, at presettable points in time, set to a desulphatisation mode following a cold start activation of the internal combustion engine prior to a transition to a normal operating mode, characterised in that the motor vehicle is started before the desulphatisation mode is set.
  2. Method according to claim 1, further
    characterised in that the operation of the internal combustion engine system is, following a cold start activation of the engine, first set to a catalyst heating mode for heating the sulphur accumulating exhaust gas purification component and then switched to the desulphatisation mode as soon as the temperature of the sulphur accumulating exhaust gas purification component has exceeded a presettable minimum desulphurisation value.
  3. Method according to claim 2 for the operation of an internal combustion engine system further incorporating means for the supply of secondary air at one or more points of the exhaust train (2), further
    characterised in that secondary air is fed into the sulphur accumulating exhaust gas purification unit or into the exhaust gas train upstream thereof in the catalyst heating mode, and in that this secondary air supply is ended at switch-over to the desulphatisation mode.
  4. Method according to any of claims 1 to 3 for the operation of an internal combustion engine system further incorporating means for supplying secondary air at one or more points of the exhaust train (2) and an oxidising catalyst unit (K3) downstream of the sulphur accumulating exhaust gas purification component, further
    characterised in that secondary air is fed into the oxidising catalyst unit or into the exhaust train section between the sulphur accumulating exhaust gas purification component and the oxidising catalyst unit in the desulphatisation mode.
  5. Method according to claim 3 or 4 for the operation of an internal combustion engine system further incorporating means for the supply of secondary air at one or more points of the exhaust train (2) and wherein the sulphur accumulating exhaust gas purification component incorporates a plurality of exhaust gas purification units (K1, K2) connected in series in the exhaust train, further
    characterised in that the sulphur accumulating exhaust gas purification units (K1, K2) are desulphatised in sequence in the desulphatisation mode in an associated desulphatisation phase, whereby secondary air is, during the relevant desulphatisation phase, exclusively fed into the exhaust train at one or more points downstream of the sulphur accumulating exhaust gas purification unit being currently desulphatised.
  6. Method according to any of claims 2 to 5, further
    characterised in that the air-to-fuel ratio (λM) of the air/fuel mixture supplied to the internal combustion engine (1) in the desulphatisation mode is selected to be richer than the stoichiometric value and leaner than in the catalyst heating mode.
  7. Method according to any of claim 1 to 6, further
    characterised in that the duration of the desulphatisation mode is determined by sensor-monitoring the accumulation state of the sulphur accumulating exhaust gas purification component and/or by the model-based estimation of the accumulated amount of sulphur, whereby the estimation is based at least on the fuel consumed and on its sulphur content and on any natural desulphatisation process completed during previous normal operation.
  8. Internal combustion engine system, in particular for a motor vehicle, comprising
    an internal combustion engine (1) with associated exhaust train (2),
    a sulphur accumulating exhaust gas purification component located in the exhaust train, and
    means for the desulphatisation of the sulphur accumulating exhaust gas purification component, including means for the supply of secondary air,
    characterised in that
    the sulphur accumulating exhaust gas purification component incorporates at least two exhaust gas purification units (K1, K2) connected in series in the exhaust train, and in that
    the means for the supply of secondary air include a separate secondary air supply branch (L2, L3) each for the sulphur accumulating exhaust gas purification units.
  9. Internal combustion engine system according to claim 8, comprising
    an internal combustion engine (1) with associated exhaust train (2),
    a sulphur accumulating exhaust gas purification component located in the exhaust train, and
    means for the desulphatisation of the sulphur accumulating exhaust gas purification component, including means for the supply of secondary air,
    characterised in that
    an oxidising catalyst unit (K3) is provided downstream of the sulphur accumulating exhaust gas purification component, and in that
    the means for the supply of secondary air include at least one secondary air supply branch (L2, L3; L4) for the sulphur accumulating exhaust gas component on the one hand and for the oxidising catalyst unit (K3) on the other hand.
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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DE19842625A1 (en) 2000-03-30
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DE59910440D1 (en) 2004-10-14
EP0987408A3 (en) 2003-01-08
EP0987408A2 (en) 2000-03-22

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