EP2084379A1 - Method for estimating the flow rate of gas entering an engine - Google Patents

Abstract

The invention relates to a method for controlling an internal combustion vehicle engine, in which the flow rate of gas (Qengine) entering the engine (Qengine) is estimated using the following formulation: Qengine Vcyl /2*N/60*ρintake * ηintake (N,ρintake) *ηexhaust (N,ρ exhaust )* n Π i=1 fi (αi) (1), in which Vcyl is the engine cylinder capacity, N is the engine speed, ρintake is the density of the gases entering the engine, ηintake is the intake performance of the gases entering the engine, ρexhaust is the density of the exhaust gases, ηexhaust is the exhaust performance of the gases leaving the engine and n Π i=1 fi(αi) is a product of correction functions f(αi) dependent respectively on another parameter αi, wherein 1 ≤ i ≤ n.

Description

 Method for estimating the flow rate of αaz entering an engine

The invention relates to a method for controlling a vehicle engine.

The invention more specifically relates to a method of controlling a vehicle engine for estimating the flow rate of gas entering the engine.

The invention applies in particular to a turbocharged supercharger diesel engine.

Internal combustion engines are often equipped with an exhaust gas recirculation (EGR) circuit from the engine outlet to the air intake circuit, for example to reduce the production of nitrogen oxides. This recirculation can, however, increase the amount of exhaust fumes if not properly adjusted. It is therefore necessary to accurately determine the amount of gas passing through the recirculation circuit.

To know precisely, it is possible to measure the flow of gases passing through the recirculation circuit (Q _EGR ), OR to measure the flow of fresh air admitted into the engine (Q _AF ) and to regulate accordingly (by a calculator) the flow of the gases passing through the recirculation circuit, or to estimate the flow of fresh air admitted into the engine (Q _AF ) and the flow rate of the gases passing through the control circuit (QEGR), from of the total quantity (Q _mo tor = QAF + QEGR) of the gases admitted to the engine without measuring one (Q _AF ) or the other

Most often, the total amount of the gases admitted into the engine is determined to deduce the fresh air flow rate and the flow rate of gas passing through the recirculation circuit (EGR).

Processes are already known for determining the total amount of gases admitted to the engine.

Of these, document FR 2789731 is known in which the total air flow entering the engine is estimated from the knowledge of the temperature and the air pressure in the collector. intake and engine speed. However, this method is approximate in the case where there is an exhaust back pressure that is variable, which is typically the case when the turbine of the turbocharger used is variable geometry or when systems are used. after-treatment in the exhaust line (catalyst, particulate filter, ...).

In such a case, it has therefore been proposed an improvement by the document FR 2824596, but which does not work optimally in all situations. An object of the invention is therefore to improve existing processes, in particular by providing a method in which it is possible to obtain a robust estimate of the total quantity of gas admitted to the engine, in at least one of the cases following:

- existence of an exhaust back pressure, in particular variable in time;

- significant thermal variations in the motor (due for example to the use of particular injection modes);

- significant variations in ambient temperature or atmospheric pressure; - variation of the amount of gas passing through the recirculation circuit (EGR).

The invention may also allow a robust estimation, even for the addition in the exhaust line of new after-treatment systems, involving a modified back pressure and a modified thermal behavior at the exhaust.

In order to achieve this objective, a method of controlling an internal combustion engine engine is provided in the context of the invention, in which the flow of gas (Q _mo tor) entering the engine (Q _mo tor ) in the following wording:

/>)

(1) where V _cy ι is the engine capacity, N the engine speed, p _is dmιssιon the density of the gas entering the engine, η _has dmιssιon the gas intake efficiency within the engine, PECHA _PP ement the density of exhaust gas ηécha _PP ement the exhaust performance of engine output gas and which is a produced of correction functions f (α,) depending respectively on another parameter α, with l≤i≤n.

The method according to the invention may furthermore have at least one of the following characteristics: the parameters α, where l≤i≤n are the ambient temperature T _amb

(ai = T _amb) and / or the temperature of cooling water of the engine _water T (α ₂ = T _water);

a mapping of the intake efficiency of the gases entering the engine η _aJmmon (N, p _aJmilum ) is determined by varying the range of possible values for the engine speed N and the density of the gases at the intake p _adm ιssιon, the other parameters of equation (1) being known or maintained at constant value;

- a mapping of yield η _x is determined by varying the range of possible values for the engine speed N and the density of the exhaust gases Péch _app ly, other parameters of the equation (1) is known or maintained at constant value;

the mapping of the exhaust efficiency of the gases leaving the _exhaust engine ( _exhaust , N, _exhaust ) is determined by the relationship η _x = i exhaust 'exhaust JI admission> admission)

a mapping of a yield η _{2 is determined} , by varying the range of possible values the ambient temperature T _amb , the other parameters of equation (1) being known or maintained at a constant value; - U a correction function is calculated dependent on parameter ai = T _amb, by the relation: J ₁ [CC ₁ 1 _amb ) ï / '21 XfI intake V * 'P intake)' l exhaust Λ 'P * exhaust))'

a mapping of a yield η _{3 is determined} , by varying the range of possible values for the cooling temperature of the water T _ea u, the other parameters of equation (1) being known or maintained at a constant value ;

a correction function f ₂ dependent on the parameter α ₂ = T _water is calculated by the relation f ₂ (α ₂ = T _water ) = η ₃ / [η _aJm∞on (N, p _aJmilum y

I exhaust 1 'exhaust J 1 J'

- is determined in any order the exhaust performance ηécha _PP ement gases leaving the engine, a correction function \ _λ dependent on the ambient temperature (T _amb = X ₁ and a correction function f ₂ dependent on temperature cooling water α ₂ = T _ea u, after a step of determining the admission efficiency η _adm ιssιo _n gas.

Other features, objects and advantages of the present invention will appear on reading the detailed description which follows, and with reference to the appended drawings, given as non-limiting examples and in which: FIG. supercharged internal combustion engine equipped with an exhaust gas recirculation circuit (EGR), and in this example a variable geometry turbo and a plurality of aftertreatment devices; - Figure 2 illustrates an exemplary mapping of the intake efficiency, determined based on the engine speed N and the density of the gas admission p _adm ιssιon

In FIG. 1, there is shown a motor 1 with an EGR circuit 4 conventionally comprising a bypass 41, a cooler 42 and a valve 43. The engine 1 also comprises a turbocharger 2 formed of a compressor 21 and a a variable geometry turbine 22, and a plurality of post-processing devices 300, 301, 302 arranged in the exhaust line 3. These elements (typically a precatalyst 300, a particulate filter 301 and a muffler 302) involve in particular a modified back pressure and thermal behavior at the exhaust. According to the method of the invention, the gas flow rate is estimated within the Q _Engine by the following formulation:

) / * n I exhaust (\ N 'ro exhaust J) * r IT IJ fΛ (a I)'

(1)

where V _cy , is the engine displacement (liters), Ν the engine speed (rev / min), p _a dmιssón the density of the gases entering the engine (kg / m ³ ), ηadmission the gas intake efficiency entering the engine, _{pe P} c ement the density of the exhaust gas (kg / m ^3), ηéchappement the gas exhaust performance at the engine outlet and n where P [Z ₁ Ca ₁₎ is a product of correction functions f (α,) dependent

I = I respectively of another parameter α, with l≤i≤n.

Admission efficiency is determined by the relation p

P _adm i _ss i _on = ~ - ^{or 'adm} is \ constant Ά ideal gas admission, RADM * 23 percent and exhaust efficiency is determined _échaDBement p = - where r _ec h

'Jl scale ¹ is the gas constant perfect exhaust.

The parameters α, with l≤i≤n are, for example, the ambient temperature T _am b (= = T _am b) and / or the temperature of the engine cooling water T _e at (α ₂ = T _water ) - To correctly identify the different terms and parameters of formula (1) above, it is necessary to follow a specific process, an embodiment of which is presented below.

In the first place (step 1), a mapping of the intake efficiency of the gases entering the engine is determined ri _{rg, ss, is} {N> P _{adm, ss, on)>} ^by varying the range of possible values for the engine speed N and the density of gas in the admission inlet, the other parameters of the equation ( 1) being known or maintained at constant value. To vary the density of the gas per _a dmιssιon at the entrance of the engine 1 is varied preferably in the engine inlet pressure, the temperature T ₂₃ in motor input also being known by a temperature sensor.

In practice, this identification of the intake efficiency is carried out at constant _water motor cooling temperature T (hot engine), at a constant ambient temperature T _amb .

In addition, the operating conditions of the engine must be as close as possible to those encountered by the driver, namely in particular in the context of the invention: a conventional combustion mode, a mean exhaust back pressure.

An example of mapping the intake efficiency is shown in Figure 2. The zone 10 corresponds to the usual operating zone of the engine 1, the zone 11 to a zone difficult to reach by a vehicle, and finally the zone 12 a corresponding zone at a very low pressure on the accelerator pedal with the vehicle launched.

Is then determined (step 2) a mapping of yield η _x, by varying the range of possible values for the engine speed N and the density of the exhaust gas transgressed _PP ement, other parameters of the equation (1) being known or maintained at constant value.

In particular, once determined the mapping of the intake efficiency, fixed on this intake efficiency η _has ιssιo d _{m n} to a known value.

Again, the identification of the exhaust ηécha _PP ement efficiency is carried out at cooling water temperature of the engine T constant _water (hot engine) and an ambient temperature T _amb constant. In addition, to vary the density of the exhaust gas transgressed _PP ement, it runs through all possible injection modes and all possible against exhaust pressures. It is thus possible to vary the temperature at the engine output T ₃ 1 or the engine output pressure P ₃₁ . Practically, the different possible back-pressures are obtained with different loadings of the particulate filter 301 or with fouling in the exhaust line 3.

The mapping of the exhaust efficiency of the gases leaving the engine is then calculated η _echappemeΛ {N, p _echappemeΛ ) by the relation η _λ =

I exhaust \ '' exhaust J I intake \> r intake / V / '

Then, a mapping of a yield η ₂ is determined (step 3), by varying the range of possible values for the ambient temperature T _am b, the other parameters of equation (1) being known or maintained at a constant value. . In particular, in this step, the intake efficiency η _has ιssιo d _{m n,} the exhaust performance ηécha _PP ement and the _water temperature T of cooling water are fixed.

On the basis of this yield η _2, it calculates a U correction function depends on parameter ai = T _amb, by the relationship: f A ^a i ^{= T} _mb) = ^ 2l ^ a _{dm, S} ^ _^ Pa _{dm, SS} , it) * ^ EXCHA _PP e _m eA _^ ^N PECHA _PP e _m,)) (3) - U Cθttθ correction function thus makes it possible to take into account the influence of the ambient temperature to the engine.

A mapping of a yield η _{3 is} then determined (step 4), by varying the range of possible values for the cooling temperature of the water T _water , the other parameters of equation (1) being known or maintained. constant value.

In particular, in this step 4, the admission admission efficiency, the exhaust efficiency ηécha _PP PPEMENT and the ambient temperature T _amb are frozen. On the basis of this efficiency η ₃ , a correction function f ₂ dependent on the parameter α ₂ = T _water is calculated by the relation f ₂ (α ₂ = Cake) = τ] 3 / [η _admιssιon {N, p _admιssιon Y η _echappemem (N, p _echappemem Y f 1 (i = T _amb)] (4).

This correction function f ₂ thus makes it possible to take into account the influence of the temperature of the cooling water of the engine.

The embodiment presented above, presenting four successive steps, is not the only possible mode. Indeed, once step 1 performed, it is quite possible to reverse steps 2, 3 and 4 in no particular order.

In other words, it is of little importance in the context of the invention to establish the correction function U, the correction function f ₂ , or the exhaust efficiency ηécha _PP in a particular order, since when determining the one of these terms, the others are frozen.

For example, once step 1 has been carried out, it is possible to perform a step 2 consisting in determining the escapement exhaust efficiency, and then a step 3 consisting of establishing a function f _{1 =} f ^ on = T _water ) according to a formulation analogous to that of formula (3), step 4 thus constituting a function f ₂ = f ₂ (α ₂ = T _am b) according to a formulation similar to that of formula (4).

For example also, once step 1 is performed, it is possible to perform a step 2 of establishing the function _Am = T b) according to equation (3) by fixing the _parameters η and η _e dmιssιon _P c ement and then determine (step 3) a mapping of the exhaust performance ηéc _h appe _m e _n t according to the formulation from equation (2) and finally (step 4) to establish a correction function f ₂ = f ₂ (α ₂ = T _water ) according to equation (4).

Claims

1. A method of controlling an internal combustion vehicle engine, wherein it is estimated the gas flow (Q _mo tor) entering the engine (Q _mo tor) by the following formulation:

I> Λ

(1) where V _cy is the engine capacity, N the engine speed, p _is dmιssιon the density of the gas entering the engine, η _has dmιssιon the gas intake efficiency within the engine, the PECHA _PP ement Density of the exhaust gas, η éc ha _PP le le le le le le le le le le le le le le le le et et et et et produced of correction functions f (α,) depending respectively on another parameter α, with l≤i≤n.

2. Method according to claim 1, characterized in that the parameters α, with l≤i≤n are the ambient temperature T _amb (α _! = T _amb ) and / or the temperature of the cooling water of the engine T _water (α ₂

3. Method according to one of the preceding claims, characterized in that a map of the intake efficiency of the gases entering the engine is determined η _aΛaimn (N, p _aΛaumn ), by varying the range of possible values for the engine speed N and the density of the gases at intake p _a dmιssιon, the other parameters of equation (1) being known or maintained at constant value.

4. Method according to one of the preceding claims, characterized in that a mapping of a yield η _{λ is determined} , by varying the range of possible values for the engine speed N and the density of the exhaust gases PECHA _PP ement, other parameters of the equation (1) are known or maintained at a constant value.

5. Method according to the preceding claim, characterized in that the mapping of the exhaust efficiency of the gases leaving the engine η _exhaust (N, _exhaust ) by the relationship η _λ = is determined.

/ exhaust \ 'r exhaust J I intake \> P intake / V / "

6. Method according to one of the preceding claims, characterized in that it determines a mapping of a yield η ₂ , by varying the range of possible values for the ambient temperature Tamb, the other parameters of the equation (1 ) being known or maintained at constant value.

7. Method according to the preceding claim, characterized in that calculates a correction function ^ dependent on the parameter α _{1 =} T _amb , by the relation: V * 'P exhaust JJ (^) ^•

8. Method according to one of the preceding claims, characterized in that it determines a mapping of a yield η ₃ , by varying the range of possible values for the water cooling temperature T _ea u, the others parameters of equation (1) being known or maintained at constant value.

9. Method according to the preceding claim, characterized in that calculates a correction function f ₂ dependent on the parameter α ₂

= T _water , by the relation f ₂ (α ₂ = T _water ) = η ₃ / [ * 7 _escape A ^N _> P _escape ) * ^ (Ui = T _amb )] (4).

10. A method according to claim 1, characterized in that in any order determines the exhaust efficiency η exhaust gases leaving the engine, a correction function U dependent on the ambient temperature on = T _am b and a function correction coefficient f ₂ dependent on the temperature of the cooling water α ₂ = water, after a step of determining the admission efficiency ηadmission dβS gθZ.