EP3358171B1 - Method for controlling a pollutant emission component present in the gases discharged from a heat engine - Google Patents

Description

The present invention relates to a method for controlling the emission of a pollutant present in the gases evacuated from a heat engine via an exhaust line, this pollutant being, for example, nitrogen oxides also referred to under their chemical formula. NOx. The control method is applied for alternative settings different from those applied during current mode.

The present invention falls within the technical field of controlling a traction chain with a powertrain as a function of the combustion modes of the thermal engine, in particular a diesel engine. The present invention intends to estimate the NOx which would be produced at the outlet of the combustion chamber with settings different from the current settings, these settings being called alternative.

The powertrain comprises a computer having memorized several distinct operating modes of the powertrain, including at least one current mode and at least one alternating mode giving rise to emissions of respective quantity of pollutant. A quantity of pollutant according to the current mode is measured or estimated. In what follows, it will be taken as an example of a pollutant of nitrogen oxides or NOx, which is not limiting.

The knowledge of the NOx at the outlet of the combustion chamber can be done either by measurement or by estimation. In the latter case, this estimate is made from numerous physical quantities directly influencing the formation of the pollutant, in particular the mass of air trapped in the chamber, the rate of exhaust gases recirculated at the engine intake, the oxygen level in the exhaust line, the outside temperature and the temperature of the heat engine known according to the temperature of the coolant in the cooling system, the injection phasing and pressure, the engine speed and the engine torque. All these parameters are not limiting and may include the oxygen level in the intake line or in the combustion chamber, the ambient humidity, the quantity of water injected.

Most of these parameters are only accessible for adjustment according to a current mode and it is not possible to use them to estimate the NOx for other alternative adjustments. However, in order to be able to manage compromises between vehicle performance and regulatory constraints, it is necessary to project the NOx that would be produced at the outlet of the combustion chamber for the various accessible combustion settings. This is not currently possible, given that the current system only allows access to the NOx at the output of the heat engine for adjustment according to a current mode.

The document FR-A-3 031 764 describes a method of controlling a power train with a heat engine connected to an exhaust line comprising a pollution control system and a control computer. The control computer stores several distinct operating modes of the powertrain allowing distinct fuel consumptions for the same reference life situation.

In this document, it is determined a target content of a pollutant to be monitored in the exhaust gases not to be exceeded and it is estimated for each of the predetermined operating modes the content of the pollutant produced by the heat engine, the efficiency maximum depollution of the pollutant by the depollution system, the expected content of the pollutant downstream of the depollution system, from the expected content at the source and the associated maximum depollution efficiency.

The estimated contents for each of the predetermined operating modes are then compared with the target content and it is applied, among the operating modes for which the estimated content is lower than the target content, the one which allows the least fuel consumption.

This document does not specifically deal with alternative modes and the difficulty of evaluating the emissions of a specific pollutant during such an alternative mode. It is attempted in this document to find a compromise between respect for the emissions emitted at the exit of the exhaust line on all the life situations of the vehicle with a minimized fuel consumption and not to know exactly the quantity of pollutant released for alternative modes.

The problem at the basis of the present invention is to estimate precisely and quickly the emissions of a specific pollutant at the outlet of the heat engine of a powertrain in an exhaust line for one or more alternative operating modes of the engine. engine.

To achieve this objective, there is provided according to the invention a method for monitoring an emission according to claim 1.

The technical effect is to obtain engine control as a function of an estimate of a quantity of nitrogen oxides for an alternating mode, which was not possible precisely according to the state of the art, the parameters for such an estimate in analogy with what is done for a current mode not all being available for an alternating mode. Thanks to this, it is possible to take into account a transient effect on the basis of the quantity of pollutants according to a current mode.

The estimation of the pollutant for alternative modes or settings can be done by using functions for transferring the quantity of current pollutant to the quantity of pollutant according to an alternative mode or setting. These transfer functions are based on the parameters used to control the engine and which are common to all current and alternative combustion settings and therefore accessible. This represents a simplification of the estimate, since there are fewer parameters to consider.

The main engine control parameters identified for an alternative mode are in fact reduced in number compared to all those physically involved in the formation of the pollutant, namely nitrogen oxides. As will be seen below, it is possible to limit oneself to the engine speed, the engine torque, the engine temperature, the air temperature or the outside temperature and the atmospheric pressure, this preferably for a correction of the ratio of the quantities of pollutant.

Advantageously, before estimating the quantity of pollutant according to said at least one alternative mode, the ratio of the quantity of pollutants is modified into a ratio corrected as a function of the outside temperature and of the altitude then in force.

Advantageously, the group of accessible parameters comprises an engine speed, an engine torque, an engine temperature and a temperature of the air admitted to the heat engine. This list can be adapted according to the level of performance expected from the model thus created.

Advantageously, the ratio of quantities of pollutant is estimated as a function of engine speed and engine torque.

Advantageously, the ratio of quantities of pollutant is estimated according to a map selected from maps produced on an engine test bench during a prior tuning of the powertrain.

Advantageously, the quantity of pollutant according to said at least one current mode is estimated according to operating parameters of the engine taken, individually or in combination, from a quantity of air mass enclosed in the heat engine, a rate of gas recirculation d '' exhaust at the air intake of the heat engine, an oxygen level in the exhaust line, in the intake line or in the combustion chamber, the ambient hygrometry, an outside temperature, a temperature of the engine, injection phasing and pressure, engine speed and engine torque, the quantity of water injected. These parameters can be obtained directly, by measurement or estimation, or indirectly, by measurement or estimation of the main influencing factors. For example, the position of an exhaust gas recirculation valve can give a sensitivity of the rate of recirculated gases, or the activation of a distribution event can give a sensitivity of the rate of burnt gases trapped in the chamber. combustion.

Advantageously, when the powertrain comprises transmission means, parameters for adjusting the transmission means are taken into account for estimating the quantity of pollutant according to said at least one current mode.

The pollutant is formed from nitrogen oxides.

The invention also relates to a powertrain control computer, characterized in that it comprises means of acquisition, processing by software instructions stored in a memory and control required for an implementation of such. process.

The invention finally relates to a power train comprising a heat engine connected to transmission means, characterized in that it comprises such a control computer. All this does not require new specific characterizations of the engine and therefore does not entail any additional costs. It is important to note that these advantages remain compatible with the regulations in force, in particular for a Diesel engine.

• la figure 1 est une représentation schématique de trois logigrammes d'un procédé d'estimation de la quantité de polluant évacué par une ligne d'échappement d'un moteur thermique, le premier logigramme en partant du haut de la figure étant pour un mode courant, le deuxième selon la présente invention pour un mode alternatif et le troisième étant un logigramme pour un mode alternatif établi en analogie avec le logigramme pour un mode courant mais ne pouvant être mis en oeuvre, (ce 3^ème logigramme pouvant techniquement être mis en œuvre, mais nécessitant plus de ressources du calculateur que les autres logigrammes)
• la figure 2 est une représentation schématique d'un logigramme d'un procédé d'estimation selon la présente invention avec l'estimation d'un ratio entre quantités courante et alternative puis une estimation de la quantité alternative de polluant en fonction de la quantité courante et du ratio.

Other characteristics, aims and advantages of the present invention will emerge on reading the detailed description which follows and with regard to the appended drawings given by way of non-limiting examples and in which:

• the figure 1 is a schematic representation of three flowcharts of a method for estimating the quantity of pollutant discharged by an exhaust line of a heat engine, the first flowchart starting from the top of the figure being for a current mode, the second according to the present invention for an alternative mode and the third being a flowchart for an alternative mode established in analogy with the logic diagram for a current mode but can not be implemented (this ^3rd flowchart can technically be implemented, but requiring more calculator resources than the other flowcharts)
• the figure 2 is a schematic representation of a flowchart of an estimation method according to the present invention with the estimation of a ratio between current and alternative quantities then an estimation of the alternative quantity of pollutant as a function of the current quantity and of the ratio .

It should be kept in mind that the figures are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention.

In what follows, reference is made to all the figures taken in combination. When reference is made to one or more specific figures, these figures are to be taken in combination with the other figures for the recognition of the designated reference numerals.

The figure 1 shows a flowchart of a method for estimating the quantity of NOx evacuated by the exhaust line of a heat engine for a current mode of operation. In dotted lines, there is shown a method of estimating the quantity of NOx evacuated by the exhaust line of a heat engine for an alternating mode, which is not feasible, given that the operating parameters of the engine thermal are not available. The engine control can thus control the operation of the heat engine and it decides to switch between the different memorized operating modes, according to the quantities of NOx estimated for the current mode and the memorized alternative mode (s), for example by targeting the mode on. least NOx emitting operation. The operating mode chosen to operate the heat engine becomes the current mode.

The quantity of NOx evacuated with the exhaust gases via the exhaust line is estimated at the outlet of the heat engine, therefore upstream of any element for selective depollution of this pollutant present in the exhaust line. In addition, the quantity of NOx can also be estimated or measured downstream of the pollution control element to verify the effectiveness of the pollution control.

At the top of the figure 1 , starting from parameters for controlling the PAR engine, the current combustion adjustment 1 is defined, mainly relating to the fuel injection and the air loop. For an adjustment according to a current REG court mode, it is estimated or measured in 2 the quantity of current NOx NOx court at the outlet of the combustion chamber for the adjustment according to a current REG court mode.

Down the figure 1 , by analogy with what is done for an adjustment according to a current REG court mode while being impossible to implement, an amount of alternative NOx NOx alt is estimated for an alternative adjustment REG alt. The steps for adjusting alternative combustion 1a and for measuring or estimating the quantity of alternative NOx NOx alt are difficult to implement and are therefore indicated in dotted lines. This is technically possible but requires more computer resources than the invention.

In the middle of the figure 1 , the flowchart according to the present invention provides for establishing a transfer function of current NOx quantity NOx court in quantity of NOx in alternative NOx alt control. This is done by function 3 and will be better seen next to the figure 2 .

To the figure 2 , there is illustrated the flowchart of an embodiment of a control method according to the invention. This process controls the emission of a pollutant present in the gases evacuated from a heat engine of a powertrain via an exhaust line.

In a known manner, the powertrain comprises a computer having memorized several distinct operating modes of the powertrain, including at least one current mode REG running and at least one alternative mode REG alt giving rise to emissions of respective quantity of pollutant.

As it has been shown at the figure 1 , a quantity of current NOx pollutant run according to said at least one current mode is measured or estimated. The estimation can be done given that all the parameters for its establishment are available for a current REG court mode while this is not the case for an alternative REG alt mode.

According to the invention, with regard to the figure 2 , it is estimated a ratio ratio b, called gross ratio, of quantities of pollutant between said at least one current mode REG court and said at least one alternative mode REG alt as a function of a group of parameters accessible during said at least one mode alternative REG alt.

This ratio can be a ratio of the quantity of current NOx pollutant yard on the quantity of NOx alt pollutant according to an alternative REG alt mode or vice versa.

The next step is the estimation of a quantity of NOx pollutant alt according to said at least one alternative mode as a function of the quantity of NOx pollutant according to said at least one current mode and said ratio ratio b of quantities of pollutants. It is then carried out a multiplication X of the quantity of current pollutant by the ratio or a division according to whether the ratio is a ratio of the quantity of pollutant NOx alt according to an alternative mode REG alt on the quantity of current pollutant NOx yard or the reverse.

To the figure 2 , it is shown first of all a gross ratio ratio b of the quantity of current pollutant NOx yard on the quantity of NOx pollutant alt according to an alternative mode REG alt. Before estimating the quantity of pollutant according to an alternative REG alt mode, the gross ratio ratio b can be modified into a corrected ratio according to the outside temperature T ° and the Altit altitude then in force to give a corrected ratio ratio corr, for example a corrected ratio ratio corr of the quantity of NOx NOx alt according to the alternative mode REG alt on the quantity of current NOx NOx court or vice versa.

The group of parameters accessible for calculating the gross ratio ratio b for an alternative REG alt mode comprises an engine speed R, an engine torque C, an engine temperature and a temperature of the air admitted to the heat engine. The engine temperature may be the temperature of the coolant in the engine cooling circuit.

As shown in figure 2 , the ratio ratio b of quantities of pollutant can be estimated as a function of engine speed R and engine torque C. The ratio ratio b of quantities of pollutant can be estimated according to a map selected from maps produced on an engine test bench during a Prior tuning of the powertrain. This is valid for the gross ratio ratio b then for the corrected ratio ratio corr.

As previously mentioned, the quantity of yard NOx pollutant according to a running REG yard mode can be estimated or measured. When the quantity of NOx pollutant run according to the current REG run mode is estimated, this estimation can be done according to the operating parameters of the engine taken, individually or in combination, from a quantity of air mass enclosed in the heat engine, a rate of recirculation of exhaust gas at the air intake of the heat engine, rate of oxygen in the exhaust line, outside temperature T °, engine temperature, injection phasing and pressure , an engine speed R and an engine torque C. This is not limiting.

The power train can include auxiliary means such as a turbocharger, an automatic or manual gearbox and a clutch so that, for example, when the power train includes transmission means, parameters for adjusting the transmission means can be taken. taken into account for estimating the quantity of pollutant according to the current mode REG yard.

For all the characteristics described above, the pollutant can be formed from nitrogen oxides. In this case, the exhaust line may include, as a pollution control element, a selective catalytic reduction system, a passive or active nitrogen oxide trap or any other system for neutralizing nitrogen oxides or NOx.

The invention also relates to a power train control computer. The control computer comprises means of acquisition, of processing by software instructions stored in a memory and control required for an implementation of such a method. In particular, the control computer can store maps of alternative modes to determine the ratio ratio b, corr ratio of quantities of pollutant.

Finally, the invention relates to a powertrain comprising a heat engine connected to transmission means comprising such a control computer.

Claims (9)

1. Method of controlling an emission of nitrogen oxide present in the gases discharged from a heat engine of a powertrain via an exhaust line, the powertrain comprising an engine control and a computer having memorized several separate operating modes of the powertrain including at least one current mode (REG cour) and at least one alternating mode (REG alt) giving rise to emissions of the respective quantity of nitrogen oxide t, a quantity of oxide of nitrogen t (NOx cour) according to said at least one current mode being estimated, characterized in that a ratio (ratio b) of quantities of nitrogen oxide between said at least one current mode (REG cour) and said at least one alternative mode (REG alt) as a function of a group of parameters accessible during said at least one current mode (Par), a quantity of nitrogen oxide (NOx alt) according to said at least one alternative mode being estimated according to the quantity of nitrogen oxide (NOx cour) according to said at least one mode and said ratio (ratio b) of quantities of nitrogen oxide, the motor control switching between the different operating modes stored as a function of the quantities of nitrogen oxide estimated for said at least one current mode (REG cour) and said at least one alternative mode (REG alt) stored.
2. Method according to the preceding claim, in which, before estimating the quantity of pollutant (NOx alt) according to said at least one alternative mode, the ratio (ratio b) of quantities of nitrogen oxide is modified into a corrected ratio (cor ratio) according to the outside temperature (T °) and the altitude (Altit) then in force.
3. Method according to claim 1 or 2, in which the group of accessible parameters comprises an engine speed (R), an engine torque (C), an engine temperature and a temperature of the air admitted to the heat engine.
4. Method according to claim 3, in which the ratio (ratio b) of quantities of nitrogen oxide is estimated as a function of the engine speed (R) and the engine torque (C).
5. Method according to any one of the preceding claims, in which the ratio (ratio b) of quantities of nitrogen oxide is estimated according to a map selected from maps produced on an engine test bench during a prior tuning of the powertrain.
6. Method according to any one of the preceding claims, in which the quantity of nitrogen oxide t (NOx cour) according to said at least one current mode is estimated to be according to operating parameters of the engine taken, individually or in combination, among a quantity of air mass enclosed in the heat engine, a rate of recirculation of exhaust gas at the air intake of the heat engine, a rate of oxygen, an outside temperature (T °), a temperature the engine, a phasing and an injection pressure, an engine speed (R) and engine torque (C).
7. Method according to the preceding claim, wherein when the powertrain include an d means of transmission of the parameters transmission means setting are taken into account for estimating the amount of nitrogen oxide (NOx cour) according to said at least one current mode.
8. Computer for controlling a powertrain, characterized in that it comprises acquisition means, processing by software instructions stored in a memory and control required for implementing the method according to any one of claims previous ones.
9. Powertrain comprising an engine connected to transmission means, characterized in that it comprises a computer control according to the preceding claim.

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