WO2000065207A1 - Method for controlling the richness of the air/fuel mixture of an internal combustion engine fitted with a hydrocarbon trap - Google Patents

Method for controlling the richness of the air/fuel mixture of an internal combustion engine fitted with a hydrocarbon trap Download PDF

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Publication number
WO2000065207A1
WO2000065207A1 PCT/FR2000/001037 FR0001037W WO0065207A1 WO 2000065207 A1 WO2000065207 A1 WO 2000065207A1 FR 0001037 W FR0001037 W FR 0001037W WO 0065207 A1 WO0065207 A1 WO 0065207A1
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WO
WIPO (PCT)
Prior art keywords
richness
trap
fuel
engine
mixture
Prior art date
Application number
PCT/FR2000/001037
Other languages
French (fr)
Inventor
Cathy Batisson
Denis Levasseur
Original Assignee
Renault
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Filing date
Publication date
Application filed by Renault filed Critical Renault
Priority to EP00920853A priority Critical patent/EP1173660A1/en
Priority to JP2000613929A priority patent/JP2002543322A/en
Publication of WO2000065207A1 publication Critical patent/WO2000065207A1/en

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828Exhaust 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
    • F01N3/0835Hydrocarbons
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00Exhaust 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
    • F01N13/009Exhaust 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
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0814Exhaust 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
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/021Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/027Introducing 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
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/14Introducing closed-loop corrections
    • F02D41/1401Introducing closed-loop corrections characterised by the control or regulation method
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/14Introducing closed-loop corrections
    • F02D41/1401Introducing closed-loop corrections characterised by the control or regulation method
    • F02D2041/1433Introducing closed-loop corrections characterised by the control or regulation method using a model or simulation of the system
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D2200/00Input parameters for engine control
    • F02D2200/02Input parameters for engine control the parameters being related to the engine
    • F02D2200/08Exhaust gas treatment apparatus parameters
    • F02D2200/0802Temperature of the exhaust gas treatment apparatus
    • F02D2200/0804Estimation of the temperature of the exhaust gas treatment apparatus

Definitions

  • the present invention relates to a method for controlling the richness of the air / fuel mixture of an internal combustion engine and, more particularly, to such a method applied to an engine delivering exhaust gases in a line where these these pass successively through an oil trap and a catalytic converter for treating said gases, the fuel richness of the mixture being regulated in a closed loop at a predetermined set richness by means of a signal delivered by an oxygen sensor placed in line d exhaust between the engine and the oil trap.
  • FIG. 1 of the accompanying drawing an internal combustion engine 1 placed in the environment described above, the engine exhaust passing through a line 2 successively passing through an oil trap 3 and a catalytic converter 4 , for example of the "trifunctional" type capable of oxidizing unburnt hydrocarbons and carbon monoxide contained in the exhaust gases and of reducing the nitrogen oxides contained in these gases, so as to transform these harmful chemical species into species less harmful, even harmless chemicals (nitrogen).
  • a catalytic converter 4 for example of the "trifunctional" type capable of oxidizing unburnt hydrocarbons and carbon monoxide contained in the exhaust gases and of reducing the nitrogen oxides contained in these gases, so as to transform these harmful chemical species into species less harmful, even harmless chemicals (nitrogen).
  • This regulation is commonly provided by closed-loop control of the opening time ti of fuel injectors (not shown) in the engine cylinders, this time being commonly called “injection time”.
  • the regulation makes use of a signal delivered by an oxygen probe, commonly called lambda probe, sensitive to the richness in oxygen of the exhaust gases, richness which one knows that it makes it possible to follow the evolutions, around the stoechio etrie , the fuel richness of the air / fuel mixture which powers the engine.
  • the signal delivered by the probe 5 "beats” thus between two levels “high” and “low” representative of a mixture called “rich” or “poor”, respectively.
  • the computer uses this information to adjust the injection time. If it perceives a lean mixture, it increases the injection time until the probe switches back to the level representative of a rich mixture. Thus the probe "beats" permanently. A certain beat frequency is necessary to obtain a fine regulation of the richness.
  • Regulation is commonly performed by a digital computer 6 duly programmed for this purpose.
  • the computer 6 moreover generally ensures complete management of the engine and then controls other operating parameters of the latter, such as the angle ⁇ of advance when the air / fuel mixture is ignited, for example.
  • the probe 5 In its position shown in FIG. 1, the probe 5 is not sensitive to the release of hydrocarbons by the trap 3, placed downstream of the probe, release which enriches the exhaust gases with hydrocarbons, the composition of these gases no longer corresponding to that which results from the combustion by the engine of an air / fuel mixture of fuel richness included in the "window" mentioned above, for which the operation of the pot 4 is optimal.
  • the object of the present invention is precisely to provide a method for controlling the richness of the air / fuel mixture of an internal combustion engine capable of maintaining the optimal operation of a catalytic converter for treating the exhaust gases of the engine during periods of release of oil by an oil trap.
  • this compensates for the excess hydrocarbons present in the exhaust gases due to the release of the hydrocarbons contained in the trap and an efficient operation of the catalytic converter placed downstream of the hydrocarbon trap is maintained. .
  • step a) described above the quantity of fuel contained in the trap is estimated and an operation of the trap in the release of hydrocarbons is detected when said quantity is positive and that the temperature of the trap is higher than a predetermined temperature.
  • the quantity of fuel stored is estimated using a model of the current value (MHCi) of this quantity such as:
  • Ki and K 2 are coefficients and DGE the exhaust gas flow.
  • the estimated quantity of trapped fuel is decremented, in proportion to the flow rate of the exhaust gases.
  • step b) described above we reduces the setpoint richness of the closed-loop regulation of the richness of the air / fuel mixture supplying the engine, by acting on a richness loop correction coefficient, involved in the calculation of the time of injection of said fuel into said engine. More particularly, action is taken on a proportional correction of said coefficient so as to regulate said air / fuel mixture into a "lean" mixture.
  • FIG. 1 is a diagram of a device for implementing the method according to the invention, partially described in the preamble to this description, and
  • an operation of the unburnt hydrocarbon trap 3 is detected by estimation in releasing said hydrocarbons into the exhaust line 2. To do this it is necessary to determine, on the one hand, whether the trap 3 contains hydrocarbons and, on the other hand, if the temperature of this trap is high enough for the trapped hydrocarbons to be released into the exhaust line 2.
  • the temperature of the trap 3 is known either by a temperature sensor 7 delivering to the computer 6 a signal representative of this temperature, or by a model making it possible to calculate this temperature.
  • F a filter coefficient, a function of the DGE flow rate of the exhaust gases.
  • the offset being a function of the flow rate DGE of the exhaust gases.
  • the computer 6 is duly programmed to execute the estimation strategy detailed below.
  • the evolution of the mass MHCi of hydrocarbons stored in the trap is followed at the current sampling instant i, at using the model:
  • - Ki constant coefficient, or resulting from a mapping involving the temperature of the trap and the quantity of hydrocarbons stored in this trap, for example,
  • This model ceases to be applied as soon as the temperature T p of the trap 3 exceeds a temperature T s predetermined above which stored hydrocarbons are released into the exhaust line, and therefore pass into the catalytic converter 4 in addition to the unburnt hydrocarbons in the engine.
  • T p of the trap 3 exceeds a temperature T s predetermined above which stored hydrocarbons are released into the exhaust line, and therefore pass into the catalytic converter 4 in addition to the unburnt hydrocarbons in the engine.
  • the DHC flow rate of the hydrocarbons then released by the trap 3 into the exhaust line 2 is therefore equal to:
  • the richness of the air / fuel mixture entering the engine is reduced when the trap 3 releases hydrocarbons into the exhaust line 2, by acting on the duration of the injection time t lr calculated by the computer 6 .
  • t x A + F. (P + P 0 )
  • A, F and Po are coefficients and P the pressure d admission of morality 1.
  • the coefficient F in particular, consists of a set of multiplicative terms such as, for example:
  • F (1 + Fi / 256) (1 + F 2/256) (1 + ALPHA CL / 256)
  • F ⁇ , F 2, etc .. are scaling correction coefficients, air temperature, water temperature, etc.
  • ALPHA CL a correction coefficient known as a "richness regulation loop" which occurs when the computer 6 provides closed loop regulation of the richness of the air / fuel mixture supplying the engine.
  • ALPHA CL first receives a "proportional correction” CP then a "full correction” CI, up to what these corrections cause a new tilting of the signal delivered by the probe 5, and so on.
  • the known oxygen probes have switching times which differ slightly depending on whether one goes from a rich mixture to a lean mixture or, on the contrary, from a lean mixture to a rich mixture, and that the richness at which the probe switches is not exactly equal to 1. These differences mean that, unless an adequate correction is provided, a particular probe ensures regulation around a richness slightly greater or slightly less than 1. This phenomenon is conventionally corrected by acting on the proportional correction CP, so as to rebalance the aforementioned areas.
  • the setpoint richness of the regulation provided by the computer 6, nominally equal to 1 is reduced by acting on the value of the proportional correction CP applied to ALPHA CL, as shown in Figure 3 of the accompanying drawing.
  • This action consists in increasing the absolute value of the proportional correction when the probe 5 detects a rich mixture and in reducing the absolute value of this correction when the probe detects a lean mixture.
  • the nominal value of the proportional correction CP is modified by adding or subtracting an "offset" 0.
  • the offset 0 is added or subtracted, to the absolute value of the correction, depending on whether one is mixing rich or poor mixture, respectively.
  • the offset 0 is advantageously a function of the DHC flow rate of hydrocarbons released by the trap 3, this flow rate being known to the computer 6 by the relation (2) given above.

Abstract

The exhaust gas successively flows through a hydrocarbon trap (3) and a catalytic converter (4) for the treatment of said gas, whereby the richness of the fuel in the mixture is regulated in a closed loop according to a predetermined set value by means of a signal delivered by an oxygen probe (5) placed in the exhaust line (2) between the engine (1) and the hydrocarbon trap (3). According to the invention, a) operation of the hydrocarbon trap (3) is detected by means of estimation by hydrocarbon release in the exhaust line (2) and b) during said operation, the richness of the set value for the regulation of the richness in a closed loop is reduced. In step a) the amount of fuel (MHC) contained in the trap is estimated and operation of the trap by hydrocarbon release is detected when said amount is positive and the temperature of the trap rises to beyond a set temperature (Ts).

Description

PROCEDE DE COMMANDE DE LA RICHESSE DU MELANGE AIR/CARBURANT D'UN MOTEUR A COMBUSTION INTERNE DEBITANT DES GAZ D'ECHAPPEMENT DANS UNE LIGNE EQUIPEE D'UN PIEGE A HYDROCARBURESMETHOD FOR CONTROLLING THE RICHNESS OF THE AIR / FUEL MIXTURE OF AN INTERNAL COMBUSTION ENGINE DELIVERING EXHAUST GASES IN A LINE EQUIPPED WITH A HYDROCARBON TRAP
La présente invention est relative à un procédé de commande de la richesse du mélange air/carburant d'un moteur à combustion interne et, plus particulièrement, à un tel procédé appliqué à un moteur débitant des gaz d'échappement dans une ligne où ceux-ci traversent successivement un piège à hydrocarbures et un pot catalytique de traitement desdits gaz, la richesse en carburant du mélange étant régulée en boucle fermée à une richesse de consigne prédéterminée au moyen d'un signal délivré par une sonde à oxygène placée dans la ligne d'échappement, entre le moteur et le piège à hydrocarbures. On a représenté à la figure 1 du dessin annexé un moteur à combustion interne 1 placé dans l'environnement décrit ci-dessus, les gaz d'échappement du moteur passant dans une ligne 2 traversant successivement un piège à hydrocarbures 3 et un pot catalytique 4, par exemple du type "trifonctionnel" capable d'oxyder les hydrocarbures imbrûlés et le monoxyde de carbone contenu dans les gaz d'échappement et de réduire les oxydes d'azote contenus dans ces gaz, de manière à transformer ces espèces chimiques nocives en espèces chimiques moins nocives, voire inoffensives (azote) .The present invention relates to a method for controlling the richness of the air / fuel mixture of an internal combustion engine and, more particularly, to such a method applied to an engine delivering exhaust gases in a line where these these pass successively through an oil trap and a catalytic converter for treating said gases, the fuel richness of the mixture being regulated in a closed loop at a predetermined set richness by means of a signal delivered by an oxygen sensor placed in line d exhaust between the engine and the oil trap. There is shown in Figure 1 of the accompanying drawing an internal combustion engine 1 placed in the environment described above, the engine exhaust passing through a line 2 successively passing through an oil trap 3 and a catalytic converter 4 , for example of the "trifunctional" type capable of oxidizing unburnt hydrocarbons and carbon monoxide contained in the exhaust gases and of reducing the nitrogen oxides contained in these gases, so as to transform these harmful chemical species into species less harmful, even harmless chemicals (nitrogen).
On sait qu'un tel pot catalytique ne traite correctement les hydrocarbures imbrûlés contenus dans les gaz d'échappement que lorsqu'il a atteint une température prédéterminée assez élevée, de l'ordre de 300 degrés environ. Au démarrage à froid du moteur, cette température n'est pas atteinte immédiatement. En outre, lors d'un tel démarrage, le mélange air/carburant d'alimentation du moteur est enrichi en carburant et on retrouve donc davantage d'hydrocarbures dans les gaz d'échappement du moteur. On a proposé alors de disposer un piège à hydrocarbures entre le moteur et le pot, pour stocker les hydrocarbures en dessous de cette température et éviter ainsi leur passage dans le pot 4. Dès qu'une température de 200° environ est atteinte dans le piège 3, celui-ci libère ou "relargue" dans la ligne 2 les hydrocarbures stockés pour que ces hydrocarbures soient ensuite réduits dans le pot 4, essentiellement sous la forme de gaz carbonique et d'eau, espèces chimiques qui sont déchargées ensuite dans l'atmosphère.It is known that such a catalytic converter does not correctly treat unburnt hydrocarbons contained in the exhaust gases until it has reached a fairly high predetermined temperature, of the order of approximately 300 degrees. When the engine is started cold, this temperature is not reached immediately. In addition, during such a start-up, the air / fuel mixture supplying the engine is enriched with fuel and therefore more hydrocarbons are found in the engine exhaust gases. It was then proposed to have an oil trap between the engine and the pot, to store the hydrocarbons below this temperature and thus avoid their passage into the pot 4. As soon as a temperature of about 200 ° is reached in the trap 3, this releases or "releases" in line 2 the stored hydrocarbons so that these hydrocarbons are then reduced in the pot 4, essentially in the form of carbon dioxide and water, chemical species which are then discharged into the atmosphere.
On sait aussi que l'utilisation d'un tel pot exige une régulation très fine de la richesse en carburant du mélange air/carburant d'alimentation du moteur, le pot 4 ne fonctionnant avec un bon rendement que dans une "fenêtre" de richesse de ce mélange centrée sur la richesse 1, c'est-à-dire sur la richesse correspondant à un mélange stoechio étrique.It is also known that the use of such a pot requires very fine regulation of the fuel richness of the air / fuel mixture supplying the engine, the pot 4 operating with good efficiency only in a richness "window" of this mixture centered on the richness 1, that is to say on the richness corresponding to a stoechio etric mixture.
Cette régulation est couramment assurée par commande en boucle fermée du temps d'ouvertures ti d'injecteurs (non représentés) de carburant dans les cylindres du moteur, ce temps étant couramment appelé "temps d'injection". La régulation fait usage d'un signal délivré par une sonde à oxygène, couramment appelée sonde lambda, sensible à la richesse en oxygène des gaz d'échappement, richesse dont on sait qu'elle permet de suivre les évolutions, autour de la stoechio étrie, de la richesse en carburant du mélange air/carburant qui alimente le moteur. Le signal délivré par la sonde 5 "bat" ainsi entre deux niveaux "haut" et "bas" représentatifs d'un mélange dit "riche" ou "pauvre", respectivement.This regulation is commonly provided by closed-loop control of the opening time ti of fuel injectors (not shown) in the engine cylinders, this time being commonly called "injection time". The regulation makes use of a signal delivered by an oxygen probe, commonly called lambda probe, sensitive to the richness in oxygen of the exhaust gases, richness which one knows that it makes it possible to follow the evolutions, around the stoechio etrie , the fuel richness of the air / fuel mixture which powers the engine. The signal delivered by the probe 5 "beats" thus between two levels "high" and "low" representative of a mixture called "rich" or "poor", respectively.
Le calculateur exploite cette information pour régler le temps d'injection. S'il perçoit un mélange pauvre, il accroît le temps d'injection jusqu'à ce que la sonde bascule de nouveau vers le niveau représentatif d'un mélange riche. Ainsi la sonde "bat" en permanence. Une certaine fréquence de battement est nécessaire pour obtenir une régulation fine de la richesse.The computer uses this information to adjust the injection time. If it perceives a lean mixture, it increases the injection time until the probe switches back to the level representative of a rich mixture. Thus the probe "beats" permanently. A certain beat frequency is necessary to obtain a fine regulation of the richness.
Lorsqu'un piège à hydrocarbures tel que le piège 3 est placé dans la ligne d'échappement 2, il faut disposer la sonde 5 entre le moteur 1 et le piège 3. En effet, quand on dispose la sonde à oxygène en aval du piège 3, la fréquence de battement est trop faible pour que l'information délivrée soit prise en compte valablement dans une régulation de richesse en boucle fermée de ce mélange air/carburant.When an oil trap such as trap 3 is placed in the exhaust line 2, it is necessary to have the probe 5 between the engine 1 and the trap 3. In fact, when the oxygen probe is placed downstream of the trap 3, the beat frequency is too low for the information delivered to be validly taken into account in a closed loop richness regulation of this air / fuel mixture.
La régulation est couramment exécutée par un calculateur numérique 6 dûment programmé à cet effet. Le calculateur 6 assure d'ailleurs généralement la gestion complète du moteur et commande alors d'autres paramètres de fonctionnement de celui-ci, tels que l'angle α d'avance à l'allumage du mélange air/carburant, par exemple .Regulation is commonly performed by a digital computer 6 duly programmed for this purpose. The computer 6 moreover generally ensures complete management of the engine and then controls other operating parameters of the latter, such as the angle α of advance when the air / fuel mixture is ignited, for example.
Dans sa position représentée à la figure 1, la sonde 5 n'est pas sensible au relargage d'hydrocarbures par le piège 3, placé en aval de la sonde, relargage qui enrichit les gaz d'échappement en hydrocarbures, la composition de ces gaz ne correspondant alors plus à celle qui résulte de la combustion par le moteur d'un mélange air/carburant de richesse en carburant comprise dans la "fenêtre" mentionnée ci-dessus, pour laquelle le fonctionnement du pot 4 est optimal.In its position shown in FIG. 1, the probe 5 is not sensitive to the release of hydrocarbons by the trap 3, placed downstream of the probe, release which enriches the exhaust gases with hydrocarbons, the composition of these gases no longer corresponding to that which results from the combustion by the engine of an air / fuel mixture of fuel richness included in the "window" mentioned above, for which the operation of the pot 4 is optimal.
La présente invention a précisément pour but de fournir un procédé de commande de la richesse du mélange air/carburant d'un moteur à combustion interne propre à maintenir le fonctionnement optimal d'un pot catalytique de traitement des gaz d'échappement du moteur pendant les périodes de relargage d'hydrocarbures par un piège à hydrocarbures .The object of the present invention is precisely to provide a method for controlling the richness of the air / fuel mixture of an internal combustion engine capable of maintaining the optimal operation of a catalytic converter for treating the exhaust gases of the engine during periods of release of oil by an oil trap.
On atteint ce but de l'invention, ainsi que d'autres qui apparaîtront à la lecture de la description qui va suivre, avec un procédé de commande du type décrit en préambule de la présente description, remarquable en ce que a) on détecte par estimation un fonctionnement du piège à hydrocarbures en relargage d'hydrocarbures dans la ligne d'échappement, et b) lors d'un tel fonctionnement, on réduit la richesse de consigne de la régulation de richesse en boucle fermée.This object of the invention is achieved, as well as others which will appear on reading the description which will follow, with a control method of the type described in the preamble to the present description, remarkable in that a) an operation is detected by estimation of the operation of the oil trap in releasing hydrocarbons into the exhaust line, and b) during 'such an operation, the setpoint richness of the closed-loop richness regulation is reduced.
Comme on le verra plus loin en détail, on compense ainsi le surcroît d'hydrocarbures présents dans les gaz d'échappement du fait du relargage des hydrocarbures contenus dans le piège et on maintient un fonctionnement efficace du pot catalytique placé en aval du piège à hydrocarbures .As will be seen below in detail, this compensates for the excess hydrocarbons present in the exhaust gases due to the release of the hydrocarbons contained in the trap and an efficient operation of the catalytic converter placed downstream of the hydrocarbon trap is maintained. .
Suivant une autre caractéristique du procédé selon l'invention, à l'étape a) décrite ci-dessus, on estime la quantité de carburant contenue dans le piège et on détecte un fonctionnement du piège en relargage d'hydrocarbures quand ladite quantité est positive et que la température du piège est supérieure à une température prédéterminée. Quand la température du piège est inférieure à ladite température prédéterminée, on estime la quantité de carburant stockée à l'aide d'un modèle de la valeur courante (MHCi) de cette quantité tel que :According to another characteristic of the process according to the invention, in step a) described above, the quantity of fuel contained in the trap is estimated and an operation of the trap in the release of hydrocarbons is detected when said quantity is positive and that the temperature of the trap is higher than a predetermined temperature. When the temperature of the trap is lower than said predetermined temperature, the quantity of fuel stored is estimated using a model of the current value (MHCi) of this quantity such as:
MHCi = MHCi-.! + ΔMHC avec . î (1)MHCi = MHCi-. ! + ΔMHC with . î (1)
ΔMHC = Kτ • K2 • DGE JΔMHC = K τ • K 2 • DGE J
où Ki et K2 sont des coefficients et DGE le débit des gaz d' échappement .where Ki and K 2 are coefficients and DGE the exhaust gas flow.
Lorsque la température du piège est supérieure à la température prédéterminée, on décrémente la quantité estimée de carburant piégé, proportionnellement au débit des gaz d'échappement.When the temperature of the trap is higher than the predetermined temperature, the estimated quantity of trapped fuel is decremented, in proportion to the flow rate of the exhaust gases.
Suivant encore une autre caractéristique de la présente invention, à l'étape b) décrite ci-dessus, on réduit la richesse de consigne de la régulation en boucle fermée de la richesse du mélange air/carburant d'alimentation du moteur, en agissant sur un coefficient de correction de boucle de richesse, intervenant dans le calcul du temps d'injection dudit carburant dans ledit moteur. Plus particulièrement, on agit sur une correction proportionnelle dudit coefficient de manière à réguler ledit mélange air/carburant en mélange "pauvre".According to yet another characteristic of the present invention, in step b) described above, we reduces the setpoint richness of the closed-loop regulation of the richness of the air / fuel mixture supplying the engine, by acting on a richness loop correction coefficient, involved in the calculation of the time of injection of said fuel into said engine. More particularly, action is taken on a proportional correction of said coefficient so as to regulate said air / fuel mixture into a "lean" mixture.
D'autres caractéristiques et avantages de la présente invention apparaîtront à la lecture de la description qui va suivre et à l'examen du dessin annexé dans lequel :Other characteristics and advantages of the present invention will appear on reading the description which follows and on examining the appended drawing in which:
- la figure 1 est un schéma d'un dispositif pour la mise en oeuvre du procédé suivant l'invention, partiellement décrit dans le préambule de la présente description, etFIG. 1 is a diagram of a device for implementing the method according to the invention, partially described in the preamble to this description, and
- les figures 2 et 3 sont des graphes utiles à la description du procédé suivant la présente invention.- Figures 2 and 3 are graphs useful for describing the process according to the present invention.
Ainsi qu'on l'a indiqué ci-dessus, dans une première étape du procédé selon l'invention, on détecte par estimation un fonctionnement du piège 3 à hydrocarbures imbrûlés en relargage desdits hydrocarbures dans la ligne d'échappement 2. Pour ce faire il faut déterminer, d'une part, si le piège 3 contient des hydrocarbures et, d'autre part, si la température de ce piège est suffisamment élevée pour que les hydrocarbures piégés puissent être relarguer dans la ligne d'échappement 2.As indicated above, in a first step of the method according to the invention, an operation of the unburnt hydrocarbon trap 3 is detected by estimation in releasing said hydrocarbons into the exhaust line 2. To do this it is necessary to determine, on the one hand, whether the trap 3 contains hydrocarbons and, on the other hand, if the temperature of this trap is high enough for the trapped hydrocarbons to be released into the exhaust line 2.
Suivant l'invention, la température du piège 3 est connue soit par un capteur de température 7 délivrant au calculateur 6 un signal représentatif de cette température, soit par un modèle permettant de calculer cette température.According to the invention, the temperature of the trap 3 is known either by a temperature sensor 7 delivering to the computer 6 a signal representative of this temperature, or by a model making it possible to calculate this temperature.
A titre d'exemple, ce modèle de la température T du piège à l'instant i peut prendre la forme : T = Tpd-D + F(Tpstab - p(i-i)) où Tpstab est la température atteinte par le piège au terme d'un fonctionnement en régime stabilisé suffisamment long pour que la température du piège n'évolue plus, etFor example, this model of the temperature T of the trap at time i can take the form: T = T p dD + F (T pstab - p (ii)) where T pstab is the temperature reached by the trap at the end of a steady state operation long enough for the temperature of the trap to no longer change, and
F un coefficient de filtrage, fonction du débit DGE des gaz d'échappement.F a filter coefficient, a function of the DGE flow rate of the exhaust gases.
En variante, on peut partir de la température Tap des gaz d'échappement en sortie du piège, connue à l'aide d'un capteur ou d'un modèle, et on tire Tpi de la relation : Tpi = Tapi ± offsetAs a variant, it is possible to start from the temperature T ap of the exhaust gases leaving the trap, known using a sensor or a model, and we draw T p i from the relation: T pi = Tapi ± offset
"l'offset" étant fonction du débit DGE des gaz d' échappement ."the offset" being a function of the flow rate DGE of the exhaust gases.
Suivant la présente invention encore, le calculateur 6 est dûment programmé pour exécuter la stratégie d'estimation détaillée ci-dessous. Lors d'un démarrage à froid du moteur, par exemple, alors que le piège se charge en hydrocarbures imbrûlés, on suit l'évolution de la masse MHCi d'hydrocarbures stockés dans le piège à l'instant d'échantillonnage courant i, à l'aide du modèle :According to the present invention also, the computer 6 is duly programmed to execute the estimation strategy detailed below. During a cold start of the engine, for example, while the trap is loaded with unburnt hydrocarbons, the evolution of the mass MHCi of hydrocarbons stored in the trap is followed at the current sampling instant i, at using the model:
Figure imgf000008_0001
Figure imgf000008_0001
- Ki = coefficient constant, ou issu d'une cartographie faisant intervenir la température du piège et la quantité d'hydrocarbures stockés dans ce piège, par exemple,- Ki = constant coefficient, or resulting from a mapping involving the temperature of the trap and the quantity of hydrocarbons stored in this trap, for example,
- K2 = coefficient égal à 1 en fonctionnement du moteur à richesse 1, supérieur à 1 en fonctionnement à richesse supérieure à 1, inférieur à 1 en fonctionnement à richesse inférieure à 1, - DGE = débit des gaz d'échappement calculé à partir de la pression d'admission et du régime du moteur, classiquement connus du calculateur β.- K 2 = coefficient equal to 1 in engine operation with richness 1, greater than 1 in operation with richness greater than 1, less than 1 in operation with richness less than 1, - DGE = exhaust gas flow rate calculated from the intake pressure and the engine speed, conventionally known from the β computer.
Ce modèle cesse d'être appliqué dès que la température Tp du piège 3 dépasse une température Ts prédéterminée au-dessus de laquelle des hydrocarbures stockés sont relargués dans la ligne d'échappement, et passent donc dans le pot catalytique 4 en plus des hydrocarbures imbrûlés dans le moteur. On continue ensuite à suivre l'évolution de la quantité d'hydrocarbures stockés dans le piège en décrémentant la masse MHCX par des décréments successifs proportionnels au débit DGE des gaz d'échappement DGE.This model ceases to be applied as soon as the temperature T p of the trap 3 exceeds a temperature T s predetermined above which stored hydrocarbons are released into the exhaust line, and therefore pass into the catalytic converter 4 in addition to the unburnt hydrocarbons in the engine. We then continue to follow the evolution of the quantity of hydrocarbons stored in the trap by decreasing the mass MHC X by successive decrements proportional to the flow rate DGE of the exhaust gas DGE.
Le débit DHC des hydrocarbures alors relargués par le piège 3 dans la ligne d'échappement 2 est donc égal à :The DHC flow rate of the hydrocarbons then released by the trap 3 into the exhaust line 2 is therefore equal to:
DHCj. ≈ MHC3. - MHC.-1 (2)DHCj . ≈ MHC 3. - MHC.- 1 (2)
A l'arrêt du moteur, le calculateur garde en mémoire la dernière valeur calculée de MHC. Celle-ci deviendraWhen the engine is stopped, the computer keeps in memory the last calculated value of MHC. This will become
MHCo, valeur initiale de MHC, au démarrage suivant du moteur, dans le nouveau calcul de MHC à l'aide du modèleMHCo, initial value of MHC, at the next engine start, in the new calculation of MHC using the model
(1) décrit ci-dessus.(1) described above.
Ainsi, grâce au modèle utilisé dans le procédé suivant l'invention, il est possible de savoir à tout instant si des hydrocarbures sont relargués par le piège dans la ligne 2, et en quelle quantité.Thus, thanks to the model used in the process according to the invention, it is possible to know at any time whether hydrocarbons are released by the trap in line 2, and in what quantity.
On décrit maintenant comment, suivant l'invention, on utilise ces informations pour maintenir la quantité totale d'hydrocarbures passant dans le pot 4, en correspondance avec celle définie par la "fenêtre" mentionnée plus haut.We will now describe how, according to the invention, this information is used to maintain the total quantity of hydrocarbons passing through the pot 4, in correspondence with that defined by the "window" mentioned above.
Suivant l'invention, on réduit la richesse du mélange air/carburant entrant dans le moteur quand le piège 3 relargue des hydrocarbures dans la ligne d'échappement 2, en agissant sur la durée du temps d'injection tl r calculée par le calculateur 6.According to the invention, the richness of the air / fuel mixture entering the engine is reduced when the trap 3 releases hydrocarbons into the exhaust line 2, by acting on the duration of the injection time t lr calculated by the computer 6 .
On sait que ce calcul fait intervenir un modèle du temps d'injection tx, par exemple de la forme : tx = A + F. (P + P0) où A, F et Po sont des coefficients et P la pression d'admission du moreur 1. Le coefficient F, en particulier, est constitué par un ensemble de termes multiplicatifs tels que, par exemple :We know that this calculation involves a model of the injection time t x , for example of the form: t x = A + F. (P + P 0 ) where A, F and Po are coefficients and P the pressure d admission of morality 1. The coefficient F, in particular, consists of a set of multiplicative terms such as, for example:
F = (1 + Fi/256) (1 +F2/256) (1 + ALPHA CL/256) où Fι,F2, etc.. sont des coefficients de correction d'échelle, de température d'air, de température d'eau, etc.. et ALPHA CL un coefficient de correction dit de "boucle de régulation de richesse" qui intervient quand le calculateur 6 assure une régulation en boucle fermée de la richesse du mélange air/carburant d'alimentation du moteur.F = (1 + Fi / 256) (1 + F 2/256) (1 + ALPHA CL / 256) where Fι, F 2, etc .. are scaling correction coefficients, air temperature, water temperature, etc. and ALPHA CL a correction coefficient known as a "richness regulation loop" which occurs when the computer 6 provides closed loop regulation of the richness of the air / fuel mixture supplying the engine.
Dans cette situation, on peut faire théoriquement évoluer le coefficient ALPHA CL dans le temps comme illustré à la figure 2 du dessin annexé, pour maintenir la richesse en carburant du mélange air/carburant à la richesse 1, sous la commande des basculements du signal délivré par la sonde à oxygène 5.In this situation, we can theoretically change the ALPHA CL coefficient over time as illustrated in Figure 2 of the accompanying drawing, to maintain the fuel richness of the air / fuel mixture at richness 1, under the control of the switching of the signal delivered by the oxygen sensor 5.
C'est ainsi que, quand la sonde 5 détecte un passage du mélange de "riche" à "pauvre", ou inversement, ALPHA CL reçoit d'abord une "correction proportionnelle" CP puis une "correction intégrale" CI, jusqu'à ce que ces corrections provoquent un nouveau basculement du signal délivré par la sonde 5, et ainsi de suite.Thus, when the probe 5 detects a change in the mixture from "rich" to "poor", or vice versa, ALPHA CL first receives a "proportional correction" CP then a "full correction" CI, up to what these corrections cause a new tilting of the signal delivered by the probe 5, and so on.
On obtient ainsi théoriquement une richesse moyenne égale à 1 puisque les aires des surfaces situées de part et d'autre de l'axe des temps, sous la courbe représentant ALPHA CL, se compensent exactement.We thus theoretically obtain an average richness equal to 1 since the areas of the surfaces located on either side of the time axis, under the curve representing ALPHA CL, compensate each other exactly.
En pratique, on constate que les sondes à oxygène connues présentent des temps de basculement qui diffèrent légèrement suivant qu'on passe d'un mélange riche à un mélange pauvre ou, au contraire, d'un mélange pauvre à un mélange riche, et que la richesse à laquelle la sonde bascule n'est pas exactement égale à 1. Ces écarts font que, sauf à prévoir une correction adéquate, une sonde particulière assure une régulation autour d'une richesse légèrement supérieure ou légèrement inférieure à 1. On corrige classiquement ce phénomène en agissant sur la correction proportionnelle CP, de manière à rééquilibrer les aires précitées. Suivant la présente invention, lorsque le piège 3 relargue des hydrocarbures imbrûlés dans la ligne d'échappement, on réduit la richesse de consigne de la régulation assurée par le calculateur 6, nominalement égale à 1, en agissant sur la valeur de la correction proportionnelle CP appliquée à ALPHA CL, comme représenté à la figure 3 du dessin annexé. Cette action consiste à accroître la valeur absolue de la correction proportionnelle quand la sonde 5 détecte un mélange riche et à réduire la valeur absolue de cette correction quand la sonde détecte un mélange pauvre.In practice, it is found that the known oxygen probes have switching times which differ slightly depending on whether one goes from a rich mixture to a lean mixture or, on the contrary, from a lean mixture to a rich mixture, and that the richness at which the probe switches is not exactly equal to 1. These differences mean that, unless an adequate correction is provided, a particular probe ensures regulation around a richness slightly greater or slightly less than 1. This phenomenon is conventionally corrected by acting on the proportional correction CP, so as to rebalance the aforementioned areas. According to the present invention, when the trap 3 releases unburnt hydrocarbons into the exhaust line, the setpoint richness of the regulation provided by the computer 6, nominally equal to 1, is reduced by acting on the value of the proportional correction CP applied to ALPHA CL, as shown in Figure 3 of the accompanying drawing. This action consists in increasing the absolute value of the proportional correction when the probe 5 detects a rich mixture and in reducing the absolute value of this correction when the probe detects a lean mixture.
En pratique, on modifie la valeur nominale de la correction proportionnelle CP par addition ou soustraction d'un "offset" 0. L'offset 0 est ajouté ou retranché, à la valeur absolue de la correction, suivant que l'on est en mélange riche ou en mélange pauvre, respectivement .In practice, the nominal value of the proportional correction CP is modified by adding or subtracting an "offset" 0. The offset 0 is added or subtracted, to the absolute value of the correction, depending on whether one is mixing rich or poor mixture, respectively.
Il est clair sur la figure 3 que cet "offset" a pour effet d'accroître l'aire située entre la courbe et l'axe des temps, sous cet axe, par rapport à l'aire correspondante située au-dessus de cet axe. On réduit ainsi artificiellement la valeur de la consigne de richesse prise en compte par la régulation.It is clear in Figure 3 that this "offset" has the effect of increasing the area between the curve and the time axis, below this axis, relative to the corresponding area located above this axis . The value of the richness setpoint taken into account by the regulation is thus artificially reduced.
La réduction de la quantité de carburant injecté dans le moteur ainsi obtenue permet, suivant la présente invention, de compenser la quantité de carburant relarguée par le piège 3 dans la ligne d'échappement 2, et donc de maintenir la richesse en hydrocarbures des gaz d'échappement du moteur dans des limites propres à permettre au pot catalytique d'assurer un traitement efficace des hydrocarbures contenus dans ces gaz. Comme on l'a vu plus haut, cet "offset" 0 peut s'ajouter à un autre, rendu nécessaire pour corriger un écart de la richesse de consigne du côté d'un mélange pauvre ou riche, résultant des caractéristiques particulières de la sonde à oxygène utilisée.The reduction in the amount of fuel injected into the engine thus obtained makes it possible, according to the present invention, to compensate for the amount of fuel released by the trap 3 into the exhaust line 2, and therefore to maintain the richness in hydrocarbons of the gases d 'engine exhaust within limits suitable for enabling the catalytic converter to efficiently process the hydrocarbons contained in these gases. As we saw above, this "offset" 0 can be added to another, made necessary to correct a difference in the setpoint richness on the side of a lean or rich mixture, resulting from the particular characteristics of the probe. oxygen used.
Suivant une autre caractéristique de la présente invention, l'offset 0 est avantageusement fonction du débit DHC d'hydrocarbures relargués par le piège 3, ce débit étant connu du calculateur 6 par la relation (2) donnée plus haut.According to another characteristic of the present invention, the offset 0 is advantageously a function of the DHC flow rate of hydrocarbons released by the trap 3, this flow rate being known to the computer 6 by the relation (2) given above.
Il apparaît maintenant que l'invention permet bien d'atteindre le but annoncé et ceci, avantageusement, sans recourir à des moyens matériels autres que ceux normalement présents dans l'environnement d'un moteur à combustion interne raccordé à une ligne d'échappement équipée d'un piège à hydrocarbures et d'un pot catalytique de traitement des gaz d'échappement. It now appears that the invention makes it possible to achieve the announced goal and this, advantageously, without resorting to material means other than those normally present in the environment of an internal combustion engine connected to an exhaust line equipped an oil trap and a catalytic converter for treating exhaust gases.

Claims

REVENDICATIONS
1. Procédé de commande de la richesse du mélange air/carburant d'un moteur (1) à combustion interne débitant des gaz d'échappement dans une ligne (2) où ceux-ci traversent successivement un piège (3) à hydrocarbures et un pot catalytique (4) de traitement desdits gaz, la richesse en carburant dudit mélange étant régulée en boucle fermée à une richesse de consigne prédéterminée au moyen d'un signal délivré par une sonde à oxygène (5) placée dans ladite ligne (2) entre ledit moteur (1) et ledit piège (3) à hydrocarbures, caractérisé en ce que : a) on détecte par estimation un fonctionnement du piège (3) à hydrocarbures en relargage d'hydrocarbures dans la ligne (2) , et b) lors d'un tel fonctionnement, on réduit la richesse de consigne de la régulation de richesse en boucle fermée .1. Method for controlling the richness of the air / fuel mixture of an internal combustion engine (1) delivering exhaust gases in a line (2) where these successively pass through an oil trap (3) and a catalytic converter (4) for treating said gases, the fuel richness of said mixture being regulated in a closed loop at a predetermined set richness by means of a signal delivered by an oxygen sensor (5) placed in said line (2) between said engine (1) and said hydrocarbon trap (3), characterized in that: a) an operation of the hydrocarbon trap (3) is released by estimation in the release of hydrocarbons in line (2), and b) during from such an operation, the setpoint richness of the closed-loop richness regulation is reduced.
2. Procédé conforme à la revendication 1, caractérisé en ce que à l'étape a), on estime la quantité de carburant (MHC) contenue dans le piège (3) et on détecte un fonctionnement du piège (3) en relargage d'hydrocarbures quand ladite quantité est positive et que la température (Tp) du piège (3) est supérieure à une température (Ts) prédéterminée.2. Method according to claim 1, characterized in that in step a), the quantity of fuel (MHC) contained in the trap (3) is estimated and an operation of the trap (3) in salting out is detected. hydrocarbons when said quantity is positive and the temperature (T p ) of the trap (3) is higher than a predetermined temperature (T s ).
3. Procédé conforme à la revendication 2, caractérisé en ce que, quand la température du piège (3) est inférieure à ladite température prédéterminée (T3) , on estime ladite quantité de carburant (MHC) à l'aide d'un modèle de la valeur courante (MHCi) de cette quantité tel que :3. Method according to claim 2, characterized in that, when the temperature of the trap (3) is lower than said predetermined temperature (T 3 ), said quantity of fuel (MHC) is estimated using a model the current value (MHCi) of this quantity such that:
MHCi ≈ MHCi-i + ΔMHC avec ΔMHC = Kι.K2.DGE où Ki et K2 sont des coefficients et DGE le débit des gaz d' échappement . MHCi ≈ MHCi-i + ΔMHC with ΔMHC = Kι.K 2 .DGE where Ki and K 2 are coefficients and DGE the flow of exhaust gases.
4. Procédé conforme à la revendication 3, caractérisé en ce que ledit coefficient (K2) est fonction de la richesse du mélange air/carburant d'alimentation du moteur (1) . 4. Method according to claim 3, characterized in that said coefficient (K 2 ) is a function of the richness of the air / fuel mixture supplying the engine (1).
5. Procédé conforme à l'une quelconque des revendications 3 et 4, caractérisé en ce que, lorsque la température (Tp) du piège (3) est supérieure à Ts, on décrémente la quantité estimée (MHC) de carburant piégé proportionnellement au débit (DGE) des gaz d'échappement. 5. Method according to any one of claims 3 and 4, characterized in that, when the temperature (T p ) of the trap (3) is greater than T s , the estimated quantity (MHC) of trapped fuel is decreased proportionally the exhaust gas flow rate (DGE).
6. Procédé conforme à l'une quelconque des revendications 3 à 5, caractérisé en ce que, lorsque le moteur (1) cesse de fonctionner, on mémorise la valeur estimée de la quantité de carburant piégé pour l'initialisation du calcul de cette quantité, au démarrage suivant du moteur.6. Method according to any one of claims 3 to 5, characterized in that, when the engine (1) stops operating, the estimated value of the quantity of trapped fuel is memorized for the initialization of the calculation of this quantity , the next time the engine is started.
7. Procédé conforme à l'une quelconque des revendications 1 à 6, caractérisé en ce que, à l'étape b) on réduit la richesse de consigne de la régulation en boucle fermée de la richesse du mélange air/carburant d'alimentation du moteur, en agissant sur un coefficient de correction (ALPHA CL) de boucle de régulation de richesse, intervenant dans le calculateur du temps d'injection ( t_ ) dudit carburant dans ledit moteur.7. Method according to any one of claims 1 to 6, characterized in that, in step b) the setpoint richness of the closed-loop regulation is reduced by the richness of the air / fuel mixture supplying the engine, by acting on a richness control loop correction coefficient (ALPHA CL), involved in the injection time calculator (t_) of said fuel in said engine.
8. Procédé conforme à la revendication 7, caractérisé en ce qu'on agit sur une correction proportionnelle (CP) dudit coefficient (ALPHA CL) de manière à réguler ledit mélange air/carburant en mélange pauvre .8. Method according to claim 7, characterized in that one acts on a proportional correction (CP) of said coefficient (ALPHA CL) so as to regulate said air / fuel mixture in lean mixture.
9. Procédé conforme à la revendication 8, caractérisé en ce que ladite action consiste à ajouter ou retrancher un offset (0) à la valeur absolue de ladite correction (CP) , en mélange riche ou en mélange pauvre, respectivement . 9. Method according to claim 8, characterized in that said action consists in adding or subtracting an offset (0) to the absolute value of said correction (CP), in rich mixture or in lean mixture, respectively.
10. Procédé conforme à la revendication 9, caractérisé en ce que ledit offset (0) est fonction du débit (DHC) du piège (3) en hydrocarbures. 10. Method according to claim 9, characterized in that said offset (0) is a function of the flow rate (DHC) of the trap (3) in hydrocarbons.
PCT/FR2000/001037 1999-04-27 2000-04-20 Method for controlling the richness of the air/fuel mixture of an internal combustion engine fitted with a hydrocarbon trap WO2000065207A1 (en)

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