EP2472088A1 - Engine control method which ensures an oil dilution which does not exceed a a maximum oil dilution at the next service - Google Patents

Abstract

The method involves determining remaining distance to be traveled (100) till next lubricating oil change in an internal combustion engine. Concentration of fuel in the oil expectable at the next oil change is calculated (102) based on current frequency of regeneration fuel injections. A regeneration fuel injection frequency, for which the concentration of fuel expectable at the next oil change is less than a preset threshold (104), is calculated (106) if the calculated concentration exceeds the threshold. The regeneration fuel injections (108) are carried out with the calculated frequency.

Description

The invention relates to particulate filters, and in particular to processes for regenerating a particle filter by injecting diesel fuel into the exhaust gas.

The exhaust gases from internal combustion engines in most motor vehicles contain a number of pollutants that are expected to reduce releases to the atmosphere (including nitrogen oxides, carbon monoxide, unburned hydrocarbons , particles and carbon dioxide). The regulations applicable to pollution by motor vehicles regularly lower the limits of acceptable discharges.

A large part of the pollutants generated by an internal combustion engine is due to incomplete combustion of the fuel. A first strategy to reduce pollutant emissions is to reduce the amount of pollutants entering the exhaust system. A second strategy for reducing pollutant emissions is to carry out a post-treatment of gases passing through the exhaust line.

Most vehicles are now equipped with a catalytic converter that includes an oxidation catalyst (to oxidize carbon monoxide and unburned hydrocarbons) and a reduction catalyst (to reduce nitrogen oxides). ).

The oxidation catalyst consists of a casing mounted in the exhaust line. The housing encloses a support or substrate coated with an active material. The substrate generally consists of a monolithic ceramic honeycomb body forming channels to be traversed by the exhaust gas. The main components of the body are usually alumina or alumino-silicates doped with zirconia (cordierite, mullite, mullite-zirconia). The coating of active materials may be composed of combined precious metals such as platinum, palladium or rhodium.

Because diesel engines produce more particulate matter, exhaust systems most often include a particulate filter for trapping solid or liquid particles consisting essentially of soot or oil droplets. To prevent clogging of the particulate filter, it must be regenerated episodically by burning the trapped particles. Burning is achieved by increasing the temperature of the exhaust gas above 550 ° C.

To increase the temperature of the exhaust gas, it is in particular known to inject diesel fuel into the exhaust gas. The combustion of this gas oil in an oxidation catalyst upstream of the filter makes it possible to heat the exhaust gases and to temporarily carry the filter to 600 ° C. This temperature must be regulated to maintain a temperature as stable as possible, to ensure a fast and efficient regeneration. More specifically, it is known to carry out post-injections of fuel in the combustion chamber, that is to say the injection of fuel after the top dead center.

Post-injections induce an increase in the fuel dilution in the engine lubricating oil. Indeed, these injections being performed after the explosion, a large part of the injected fuel is deposited on the wall of the combustion chamber. The passage of fuel to the crankcase via the piston rings is then facilitated.

As a result, an increased amount of fuel is diluted in the lubricating oil. Even using a good quality lubricating oil, the presence of fuel in this oil causes the drop in its viscosity and therefore its lubricating properties. In addition, the oil pressure also drops. In addition, the additives present in the lubricating oil undergo premature dilution and aging. To avoid altering the operation and life of the engine, the frequency of emptying the lubricating oil must be increased, which is poorly perceived by the user.

The patent application FR2866927 discloses a motor control method for maintaining a satisfactory interval between the draining of the lubricating oil. This document describes the measurement of fuel dilution in the lubricating oil. The control method regulates fuel dilution using a degraded mode during a NOx trap regeneration phase when the dilution level exceeds a high threshold. In degraded mode, the richness of the mixture air / fuel is lowered. In this way, the dilution level is maintained at a relatively low level during regeneration, and the evaporation of the fuel occurring outside the regeneration phases reduces the dilution to a satisfactory level. In this way, the level of dilution of the fuel in the oil can be maintained at a sufficiently low level to maintain a long interval between oil changes without the properties of the lubricating oil being too heavily altered.

However, it would be desirable to avoid as much as possible to use a degraded mode of operation when too much concentration of diluted gasoline in the lubricating oil.

• déterminer la distance restant à parcourir jusqu'à la prochaine vidange de l'huile de lubrification du moteur;
• sur la base de la fréquence actuelle des injections de carburant de régénération, calculer la concentration de carburant dans l'huile prévisible à la prochaine vidange ;
• si la concentration calculée dépasse un seuil prédéterminé, calculer une fréquence d'injection de régénération pour laquelle la concentration de carburant dans l'huile prévisible à la prochaine vidange est inférieure audit seuil prédéterminé, réaliser des injections de régénération avec ladite fréquence calculée.

The invention aims to solve this drawback. The invention thus relates to a control method of an internal combustion engine provided with an exhaust gas depollution device, the depollution device being regenerated periodically by fuel injection into the combustion chamber of the engine, the method comprising the steps of:

• determine the distance remaining until the next oil change of the engine lubricating oil;
• based on the current frequency of regeneration fuel injections, calculate the expected fuel oil concentration at the next oil change;
• if the calculated concentration exceeds a predetermined threshold, calculating a regeneration injection frequency for which the fuel concentration in the oil to be expected at the next oil change is below said predetermined threshold, performing regeneration injections with said calculated frequency.

• pour plusieurs composés du carburant, le calcul d'une quantité prévisible du composé dans le carburant à la prochaine vidange en fonction d'un modèle d'évaporation de ce composé ;
• le cumul des quantités prévisibles calculées pour les différents composés ;
• le calcul de la concentration prévisible de carburant dans l'huile en fonction des quantités prévisibles cumulées.

According to one variant, the calculation of the fuel concentration in the oil comprises:

• for several fuel compounds, calculating a predictable amount of the compound in the fuel at the next oil change based on an evaporation model of that compound;
• the sum of the foreseeable quantities calculated for the different compounds;
• the calculation of the foreseeable fuel concentration in the oil according to the foreseeable cumulative quantities.

According to another variant, the calculation of the predicted concentration of fuel in the oil includes the calculation of the amount of oil expected at the next oil change according to an oil consumption model.

• le calcul de la quantité de carburant susceptible d'être diluée dans l'huile jusqu'à la prochaine vidange ;
• le calcul de la quantité de carburant ayant déjà été diluée dans l'huile depuis la précédente vidange.

According to another variant, the calculation of the fuel concentration in the oil that can be expected at the next oil change comprises:

• calculating the amount of fuel that can be diluted in the oil until the next oil change;
• the calculation of the quantity of fuel already diluted in the oil since the previous emptying.

• déterminer la distance restant à parcourir jusqu'à la prochaine vidange de l'huile de lubrification du moteur;
• sur la base d'une fréquence actuelle d'injection de carburant de régénération, calculer la concentration de carburant dans l'huile prévisible à la prochaine vidange ;
• comparer la concentration de carburant prévisible à un seuil prédéterminé ;
• si la concentration calculée dépasse ledit seuil, calculer une fréquence d'injection de régénération pour laquelle la concentration de carburant dans l'huile prévisible à la prochaine vidange est inférieure audit seuil prédéterminé ;
• commander des injections de régénération avec ladite fréquence calculée.

The invention also relates to an engine control computer, configured to control regeneration fuel injections of a pollution control device attached to the engine, the computer being able to:

• determine the distance remaining until the next oil change of the engine lubricating oil;
• based on a current regeneration fuel injection frequency, calculating the fuel concentration in the predictable oil at the next oil change;
• compare the predicted fuel concentration with a predetermined threshold;
• if the calculated concentration exceeds said threshold, calculating a regeneration injection frequency for which the predicted oil fuel concentration at the next oil change is below said predetermined threshold;
• control regeneration injections with said calculated frequency.

• la figure 1 est une représentation schématique d'un moteur et de sa ligne d'échappement ;
• la figure 2 est un diagramme illustrant la dilution de gazole dans l'huile de lubrification ;
• la figure 3 est un logigramme illustrant le fonctionnement d'un procédé selon un mode de réalisation de l'invention.

Other characteristics and advantages of the invention will emerge clearly from the description which is given hereinafter, by way of indication and in no way limitative, with reference to the appended drawings, in which:

• the figure 1 is a schematic representation of an engine and its exhaust line;
• the figure 2 is a diagram illustrating the dilution of diesel fuel in the lubricating oil;
• the figure 3 is a logic diagram illustrating the operation of a method according to an embodiment of the invention.

The figure 1 illustrates a diesel engine 1 having a cylinder block 2 fixed on a low engine oil sump 3. The low engine oil sump 3 contains a reserve of oil used to lubricate in a manner known per se different engine components 1 Combustion chambers 4 are formed in the cylinder block 2. Injectors 5 are configured to be able to carry out fuel injections in the combustion chambers 4. A control module 9, implemented in the form of a control unit motor control, controls injections by injectors 5.

The engine 1 also comprises an exhaust line. The exhaust line comprises an exhaust manifold 6. The exhaust gas passes through the manifold 6. The exhaust line further comprises an oxidation catalyst 7. The catalyst 7 is placed upstream of a filter to particles 8.

The control module 9 is advantageously configured to carry out late injections in the combustion chambers in order to obtain regenerations of the particulate filter 8. The temperature of the exhaust gases entering the particulate filter 5 must be maintained at a temperature of the order of 600 ° C during regeneration to allow the combustion of soot formed by the capture of particles. The computer 9 comprises a temperature control loop in the particulate filter 8, in order to control the temperature induced by the regeneration injections. The computer 9 determines a temperature set point for this regulation loop and consequently determines the optimum moments and quantities of fuel for performing the regeneration injections.

The figure 2 illustrates the principle of the dilution of fuel in the lubricating oil of the engine 1. Following a regeneration, the amount of fuel diluted in the lubricating oil is at a certain level Q0. In the absence of regeneration during an IR interregeneration interval, fuel evaporates from the oil. The amount of fuel in the oil then decreases. A regeneration then occurs and a late injection is performed for a duration RG. The amount of fuel in the oil then increases to a level Q1. After an alternation of regenerations and inter-regeneration intervals, the amount of fuel in the oil reaches a level QN when the vehicle has traveled a mileage requiring the draining of the lubricating oil.

The logigram of the figure 3 details an example of implementation of the motor control method 1.

At different times of operation of the engine 1 between two oil changes, the computer 9 checks the fuel concentration in the lubricating oil to determine whether the vehicle can continue to operate unhindered until the next oil change. Such verification can be carried out at regular intervals, for example at regular mileage intervals, at regular time intervals of operation, or after each regeneration.

During a step 100, the computer 9 determines that a check must be made. The computer 9 determines the remaining distance to be traveled until the next oil change of the engine lubricating oil.

The computer 9 also has a history of the regeneration of the particulate filter 8 since the last emptying. The computer 9 can thus determine the duration and the spacing between the regenerations of the particle filter 8 already intervened. The computer 9 can then determine the fuel concentration currently present in the lubricating oil on the basis of this history. The computer 9 can also store a quantity of fuel diluted in the lubricating oil and calculated previously.

Starting from the quantity of fuel currently diluted in the oil, the computer 9 calculates in step 102 the fuel concentration in the oil expected at the next oil change, on the basis of the current frequency of the filter regeneration injections. with particles. The computer 9 determines that a number N of regenerations of the particle filter 8 will be made on the basis of the current frequency.

Avec :

• Q(N) = quantité de carburant présente dans l'huile de lubrification dans N régénérations ;
• Qlni = quantité de carburant initialement présente dans l'huile de lubrification ;
• Qlntro = quantité moyenne de carburant introduite dans l'huile de lubrification durant les régénérations ;
• n = 3600/T*Tps_Evap
• Tps_Evap = intervalle moyen mesuré entre les régénérations ;
• T = temps d'échantillonnage de l'historique ;
• q= 1 +alpha* T
• alpha = facteur d'évaporation moyen du carburant.

Initially, the computer 9 calculates the amount of fuel in the lubricating oil expected at the next oil change. The calculation of this diluted fuel quantity can be based on the following formula: $$\mathit{Q}\left(\mathit{NOT}\right)\mathit{=}{\mathit{Q}}_{\mathit{Intro}}\left(\mathit{1}\mathit{+}{\mathit{q}}^{\mathit{not}}\mathit{x}\left(\mathit{1}\mathit{-}{\mathit{q}}^{\left(\mathit{NOT}\mathit{-}\mathit{1}\right)\mathit{xn}}\right)\mathit{/}\left(\mathit{1}\mathit{-}{\mathit{q}}^{\mathit{not}}\right)\right)\mathit{+}{\mathit{Q}}_{\mathit{ini}}x{\mathit{q}}^{\mathit{N\; xn}}$$

With:

• Q (N) = amount of fuel present in the lubricating oil in N regenerations;
• Qlni = amount of fuel initially present in the lubricating oil;
• Qlntro = average amount of fuel introduced into the lubricating oil during regenerations;
• n = 3600 / T * Tps_Evap
• Tps_Evap = average interval measured between regenerations;
• T = sampling time of the history;
• q = 1 + alpha * T
• alpha = average evaporation factor of the fuel.

This model thus takes into account the total number of regenerations envisaged until the next oil change, as well as the evaporation of the fuel occurring during the operation of the vehicle between two regenerations. The evaporation of the fuel is obtained during the operation of the engine 1 during the inter-regeneration intervals, because of the temperature of the oil during this operation.

Advantageously, the calculation of the amount of diluted fuel that can be envisaged is made from such a formula for different compounds having different evaporation properties. The distinct amounts of the various compounds introduced will also be taken into account. The amount of fuel diluted in the lubricating oil will be the sum of the calculated amounts for the different compounds.

The concentration of fuel in the oil is then calculated by dividing the envisaged fuel quantity calculated by the amount of lubricating oil present in the crankcase 3. The amount of oil present in the crankcase 3 can take in account the quantity introduced during the previous emptying (filled for example by the technician performing the emptying), as well as the estimated oil consumption for the engine 1. A model of calculation of oil consumption can be taken into account for adjust the amount of oil present, and can for example take into account the oil consumption measured during the previous emptying. A calculation of fuel concentration in the particularly precise oil can thus be obtained.

In step 104, the fuel concentration in the oil contemplated for the next oil change is compared to a maximum threshold. If the calculated concentration is below this maximum threshold, the computer 9 determines that the operation of the engine 1 can continue normally in step 110, without risking a mechanical breakage by deterioration of the lubricating properties due to the presence of diluted fuel .

If the calculated concentration is greater than this maximum threshold, the computer 9 determines a risk for the operation of the engine 1 before reaching the next emptying. The computer 9 then decrements during a step 106 the number of regenerations to consider until the next emptying. The fuel concentration calculation of step 102 is performed again with the decremented value of the number of regenerations. Thus, the number of regenerations to be considered is decremented until the foreseeable fuel concentration at the next emptying is below the maximum threshold. Advantageously, the decrementation of the number of regenerations to be performed may be proportional to the difference between the predicted concentration and the maximum threshold, in order to allow a faster convergence of the calculation of the number of regenerations to be performed. The decrementation may be performed based on a spacing of the kilometric interval between regenerations, or based on a spacing of the time interval between regenerations. The time spacing between the future regenerations can for example be calculated based on the average distance between the regenerations and on the average speed of the vehicle between the regenerations, this information being able to be stored in a history of the computer 9.

In step 108, the operation of the engine 1 continues, the computer 9 imposing a maximum regeneration spacing corresponding to the number of regenerations determined during the decrementation of the last step 106. Such operation of the engine 1 ensures that the fuel concentration in the lubricating oil will be lower than said maximum threshold during the next emptying.

The invention advantageously makes it possible to protect the engine from deterioration related to a too high dilution ratio, to protect the vehicle from a risk of fire by overheating, or to identify a failure leading to an excessive concentration of fuel and compensated by a failure to comply with the standards of depollution. The invention makes it possible to guarantee such operating conditions, without requiring the operation of the motor in a degraded mode.

Claims (5)

A method of controlling an internal combustion engine equipped with an exhaust gas depollution device, the depollution device being periodically regenerated by fuel injection into the engine combustion chamber, the method comprising the steps of: - determining (100) the distance remaining until the next oil change of the engine lubricating oil; - based on the current frequency of regeneration fuel injections, calculate (102) the expected fuel oil concentration at the next oil change; - if the calculated concentration exceeds a predetermined threshold (104), calculating a regeneration injection frequency (106) for which the fuel concentration in the oil to be expected at the next oil change is below said predetermined threshold, performing injections (108) ) regeneration with said calculated frequency. The method of claim 1, wherein calculating the fuel concentration in the oil comprises: for several fuel compounds, calculating a foreseeable quantity of the compound in the fuel at the next oil change according to an evaporation model of this compound; - the sum of the foreseeable quantities calculated for the different compounds; - the calculation of the foreseeable fuel concentration in the oil according to the foreseeable cumulative quantities. A method according to claim 1 or claim 2, wherein calculating the predicted fuel oil concentration includes calculating the amount of oil expected at the next oil change based on an oil consumption pattern. A method as claimed in any one of the preceding claims, wherein calculating the predicted fuel oil concentration at the next oil change comprises: - the calculation of the quantity of fuel that can be diluted in the oil until the next oil change; - the calculation of the quantity of fuel already diluted in the oil since the previous emptying. Engine control computer, configured to control regeneration fuel injections of a pollution control device attached to the engine, the computer being characterized in that it is capable of: - determine the distance remaining until the next oil change of the engine lubricating oil; - on the basis of a current regeneration fuel injection frequency, calculate the fuel concentration in the predictable oil at the next oil change; compare the predicted fuel concentration with a predetermined threshold; if the calculated concentration exceeds said threshold, calculating a regeneration injection frequency for which the oil concentration predicted at the next oil change is below said predetermined threshold; - control regeneration injections with said calculated frequency.

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