FR3062163A1 - METHOD FOR ACTIVATING A COMBUSTION MODE OF AN ENGINE PROMOTING THERMAL EXHAUST AT THE BEGINNING OF RUNNING - Google Patents

Abstract

The invention relates primarily to a method for controlling a motor vehicle engine, characterized in that it comprises: a step (101) for comparing a measured temperature (Tmes) of an exhaust line with a threshold temperature (Ts), - a step (104) for calculating the duration of a carbon dioxide window, - a step (106, 107) for comparing a power received by a pollution control system during said window of carbon dioxide (Pf) with a minimum threshold (Smin) and a maximum threshold (Smax), and - a step (108) of activation of a specific combustion mode (M spe) in the case where the temperature of said exhaust line is lower than said threshold temperature (Ts) and wherein said power received by said pollution control system during the carbon dioxide window (Pf) is between said minimum threshold (Smin) and said maximum threshold (Smax) .

Description

Holder (s): PEUGEOT CITROËN AUTOMOBILES SA Société anonyme.

O Extension request (s):

® Agent (s): PEUGEOT CITROËN AUTOMOBILES SA Public limited company.

® METHOD OF ACTIVATING A COMBUSTION MODE OF AN ENGINE PROMOTING THE EXHAUST THERMAL ENGINE AT THE BEGINNING OF TRAVEL.

FR 3,062,163 - A1 (57) The invention relates mainly to a method for controlling a heat engine of a motor vehicle, characterized in that it comprises:

a step (101) of comparing a measured temperature (Tmes) of an exhaust line with a threshold temperature (Ts),

a step (104) for calculating the duration of a window of carbon dioxide,

a step (106, 107) of comparing a power received by a depollution system during said window of carbon dioxide (Pf) with a minimum threshold (Smin) and a maximum threshold (Smax), and

a step (108) of activation of a specific combustion mode (M spe) in the case where the temperature of said exhaust line is lower than said threshold temperature (Ts) and where said power received by said system of depollution during the carbon dioxide window (Pf) is between said minimum threshold (Smin) and said maximum threshold (Smax).

The present invention relates to a method for activating a mode of combustion of an engine which favors the thermal exhaust at the start of travel. The invention finds a particularly advantageous, but not exclusive, application for increasing the temperature in the exhaust line of a diesel type engine in order to reach a minimum operating temperature of a pollution control system.

In a context of depollution of exhaust gases from a diesel engine, use is made in particular of selective catalytic reduction systems (or SCR for Selective Catalyst Reduction) aimed at reducing the nitrogen oxides (NOx) contained in the exhaust gases. The functioning of the SCR system is based on a chemical reaction between nitrogen oxides and a reducing agent conventionally taking the form of ammonia. The injection of ammonia into the exhaust line is generally carried out by means of another chemical species, such as urea dissolved in water.

More specifically, the urea solution injected into the exhaust line first vaporizes to transform into solid urea and water vapor. Then, the urea turns into ammonia inside a catalyst installed on the exhaust line. The ammonia can then reduce the nitrogen oxides released by the engine to nitrogen and water.

It is necessary to wait until the exhaust gases reach a certain temperature at the level of the injector, in particular greater than 150 degrees, before being able to ensure under good conditions the vaporization of the urea solution in the exhaust line. Before this temperature is reached, the nitrogen oxides are not treated, which poses problems of efficiency of the depollution system.

In certain life situations, the so-called nominal combustion mode does not allow this temperature to be reached quickly enough, especially during urban driving. To overcome this, there are specific combustion modes which degrade combustion and allow an increase in the exhaust thermal.

These specific modes of combustion, however, have the disadvantage of increasing fuel consumption, and diluting the gas oil in the oil. It is therefore important to use these methods sparingly.

The existing strategies based on the activation of the specific combustion mode for a predetermined period at the start of taxiing are however not optimal, this specific combustion mode can be used when it is not efficient or on a duration too long, strongly penalizing in both cases the consumption of the vehicle without changing the efficiency of the depollution line.

The invention aims to remedy these drawbacks effectively by proposing a method for controlling a heat engine of a motor vehicle equipped with an exhaust gas pollution control system installed in an exhaust line, characterized in that that it includes:

a step of comparing a measured temperature of the exhaust line with a threshold temperature,

a step for calculating the duration of a time window corresponding to a given quantity of carbon dioxide emitted, known as the carbon dioxide window,

a step of comparing a power received by the depollution system during the carbon dioxide window with a minimum threshold corresponding to an activation potential of a specific combustion mode and a maximum threshold corresponding to a capacity of sufficient heating of the exhaust line, and

- a step of activation of the specific combustion mode allowing the heating of the exhaust line in the case where the temperature of the exhaust line is lower than the threshold temperature and where the power received by the depollution system during the carbon dioxide window is between the minimum threshold and the maximum threshold.

The invention thus makes it possible to promote the rise in temperature of the exhaust line at the start of taxiing, in order to obtain the maximum efficiency of the pollution control system as quickly as possible. The invention also makes it possible to guarantee the activation of the specific combustion mode favoring the thermal necessary. This optimizes fuel consumption and reduces the dilution of diesel in the oil, while achieving the maximum efficiency of the pollution control system as quickly as possible.

According to one implementation, the threshold temperature is between 100 ° C and 130 ° C.

According to one implementation, the carbon dioxide window is between 50g and 100g of carbon dioxide.

According to one implementation, the power received by the pollution control system during the carbon dioxide window is defined by an energy received by the pollution control system during the carbon dioxide window divided by a duration of the window of carbon dioxide.

According to one implementation, the minimum threshold corresponding to the activation potential of the specific combustion mode of the exhaust line is between 1kW and 3kW.

According to one implementation, the minimum threshold is preferably equal to 2kW.

According to one implementation, the maximum threshold corresponding to the sufficient heating capacity of the exhaust line is between 5kW and 7kW.

According to one implementation, the maximum threshold is preferably equal to 5kW.

According to one implementation, the threshold temperature, the minimum threshold, and the maximum threshold depend on an aging of the exhaust line.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given only by way of illustration but in no way limit the invention.

Figure 1 is a schematic representation of an exhaust line comprising an exhaust gas pollution control system controlled by the method according to the present invention;

Figure 2 is a diagram of the steps implemented in the process for controlling the heat engine according to the present invention.

Figure 1 shows an exhaust line 1 of a heat engine 2 on which is installed a pollution control system 5 incorporating for example a catalyst 51 catalytic reduction system (SCR) and a particulate filter 52. A reducing agent injector 6 is positioned upstream of the pollution control system 5.

A mixing box 4 may preferably be positioned upstream of the catalyst 51. This mixing box 4 makes it possible to increase the distance traveled by the exhaust gases between the injection point and the catalyst 51 via the establishment of a spiral-shaped trajectory. This facilitates mixing with the exhaust gases as well as evaporation of the droplets from the reducing agent solution.

The SCR system is suitable for injecting a solution of reducing agent into the exhaust line 1 in order to transform the nitrogen oxides (NOx) released by the engine into nitrogen and water. The reducing agent solution consists of urea solubilized in water.

A computer 8 provides in particular the control of the heat engine 2, as well as management of the various after-treatment elements of the exhaust gases. In particular, the computer 8 manages the injection of the quantity of reducing agent into the exhaust line 1 as a function of the operating conditions of the engine 2 as well as the different modes of combustion of the heat engine 2. The computer 8 includes a memory storing software instructions for implementing the method according to the present invention.

Described below, with reference to Figure 2, the steps of the control method of the engine 2 according to the invention to promote the rise in temperature of the exhaust line 1 at the start of travel in order to '' obtain the maximum efficiency of the pollution control system as quickly as possible 5.

In a step 101, a measured temperature Tmes of the exhaust line 1 is compared with a threshold temperature Ts of the cold exhaust line 1, for example between 100 ° C and 130 ° C, to determine whether the vehicle is in an operating phase at the start of taxiing or equivalent, such as for example a phase of taxiing downhill without requesting engine power. In the case where the measured temperature Tmes is greater than the threshold temperature Ts, this means that the vehicle is not in a start-of-travel phase, and a so-called nominal combustion mode M nom is therefore activated in a step 102. The nominal combustion mode M nom is the normal mode of use of the engine 2 making it possible to have the best compromise in particular in terms of emissions, consumption, performance and noise.

In the case where the measured temperature Tmes is lower than the threshold temperature Ts, this means that the vehicle is in a start-of-travel phase. The computer 8 then determines whether sufficient power has been supplied to the exhaust line 1 in a step 103.

For this purpose, the computer 8 calculates, in a step 104, a duration of a time window, called the carbon dioxide window, corresponding to the duration over which a given quantity of carbon dioxide is emitted. This amount of carbon dioxide per window is for example between 50g and 100g, which corresponds to a given energy. Then, in a step 105, the computer 8 calculates a power Pf received by the depollution system during a window of carbon dioxide by dividing the energy received by the depollution system during the window of carbon dioxide by a duration of the previously calculated carbon dioxide window.

The computer 8 then performs, in a step 106 a comparison between the power Pf with a maximum threshold Smax corresponding to a sufficient heating capacity of the exhaust line 1. The maximum threshold Smax is for example between 5kW and 7kW, and is preferably worth 5kW.

In the case where the power Pf is greater than the maximum threshold Smax, the nominal mode M name is activated in step 102, because this means that the taxiing is dynamic enough for the exhaust line 1 to be able to heat any alone pretty quickly.

In the case where the power Pf is less than the maximum threshold Smax, the computer 8 determines whether there is a potential for activating the specific combustion mode Mspe. The specific combustion mode Mspe is a combustion mode degraded compared to the nominal combustion mode M nom making it possible to increase the temperature of the exhaust line 1 by playing on the patterns of the injection train so as to apply a post -injection which does not provide torque but only thermal.

To this end, the computer 8 compares, in a step 107, the power Pf with a minimum threshold Smin of activation potential of the specific combustion mode M spe, which is for example between 1 kW and 3kW, and preferably worth 2kW.

In the case where the power Pf is less than the minimum threshold Smin, this means that the power of the motor 2 is too low for the specific mode Mspe to be able to develop its thermal potential. An activation under these conditions is therefore ineffective, so that the computer 8 commands the activation of the nominal mode M nom in step 102.

In the case where the power Pf is greater than the minimum threshold Smin, this means that the taxiing is sufficiently dynamic. The specific combustion mode M spe is then activated in a step 108.

Thus, the specific combustion mode M spe is activated in the case where the temperature Tmes of the exhaust line 1 is lower than the threshold temperature Ts and where the power Pf received by the depollution system during a window of carbon dioxide is between the minimum threshold Smin of activation potential of the specific combustion mode M spe and the maximum threshold Smax of sufficient heating capacity of the exhaust line 1.

The behavior of the exhaust line 1 degrades as it ages, the activation criteria as well as the activation times of the specific mode M spe depend on this aging. Thus, the threshold temperature Ts, the minimum threshold Smin, the maximum threshold Smax and the activation times of the specific combustion mode M spe depend on the vehicle mileage in order to take into account the aging of the exhaust line 1 and therefore the theoretical drop in efficiency of the pollution control system 5.

Claims (10)

Claims: 1. Method for controlling a heat engine (2) of a motor vehicle equipped with an exhaust gas pollution control system (5) installed in an exhaust line (1), characterized in that it comprises: a step (101) of comparing a measured temperature (Tmes) of said exhaust line (1) with a threshold temperature (Ts), a step (104) for calculating the duration of a time window corresponding to a given quantity of carbon dioxide emitted, known as the carbon dioxide window, - a step (106, 107) of comparing a power received by said depollution system during said window of carbon dioxide (Pf) with a minimum threshold (Smin) corresponding to a potential for activating a combustion mode specific (M spe) and a maximum threshold (Smax) corresponding to a sufficient heating capacity of said exhaust line (1), and a step (108) of activating said specific combustion mode (M spe) allowing the heating of said exhaust line (1) in the case where the temperature of said exhaust line (1) is lower than said threshold temperature (Ts) and where said power received by said pollution control system during the carbon dioxide window (Pf) is between said minimum threshold (Smin) and said maximum threshold (Smax). 2. Method according to claim 1, characterized in that said threshold temperature (Ts) is between 100 ° C and 130 ° C. 3. Method according to claim 1 or 2, characterized in that said window of carbon dioxide is between 50g and 100g of carbon dioxide. 4. Method according to any one of claims 1 to 3, characterized in that said power received by said pollution control system during said window of carbon dioxide (Pf) is defined by an energy received by said pollution control system during said window of carbon dioxide divided by a duration of said window of carbon dioxide. 5. Method according to any one of claims 1 to 4, characterized in that said minimum threshold (Smin) corresponding to the activation potential of said specific combustion mode (M spe) of said exhaust line (1) is understood between 1kW and 3kW. 6. Method according to claim 5, characterized in that said minimum threshold (Smin) is preferably equal to 2kW. 7. Method according to any one of claims 1 to 6, characterized in that said maximum threshold (Smax) corresponding to the sufficient heating capacity of 5 said exhaust line (1) is between 5 kW and 7 kW. 8. Method according to claim 7, characterized in that said maximum threshold (Smax) is preferably equal to 5kW. 9. Method according to any one of claims 1 to 8, characterized in that said threshold temperature (Ts), said minimum threshold (Smin), and said maximum threshold 10 (Smax) depend on an aging of said exhaust line (1). 1/1