阅读说明：本技术 用于控制内燃发动机的燃烧的方法 (Method for controlling combustion of internal combustion engine ) 是由 M·潘奇罗利 M·德切萨雷 R·兰佐尼 A·齐托 于 2020-03-31 设计创作，主要内容包括：一种用于控制内燃发动机(1)的燃烧的方法,所述方法包括：根据表示低压EGR回路的影响的量的目标值(R<Sub>EGR</Sub>)、旋转速度(n)、进气效率(η<Sub>ASP</Sub>)和燃烧指数(MFB50)的开环贡献(MFB50<Sub>OL</Sub>)来确定提供火花提前值(SA<Sub>model</Sub>)的燃烧模型；根据燃烧指数(MFB50)来计算火花提前的第一闭环贡献(ΔSA<Sub>MFB50</Sub>)；根据指示爆震能量的量来计算火花提前的第二闭环贡献(ΔSA<Sub>KNOCK</Sub>)；并通过由燃烧模型提供的火花提前值(SA<Sub>model</Sub>)和第一闭环贡献(ΔSA<Sub>MFB50</Sub>)或替代地第二闭环贡献(ΔSA<Sub>KNOCK</Sub>)之和来计算将被操作的火花提前角的目标值(SA<Sub>obj</Sub>)。(A method for controlling combustion of an internal combustion engine (1), the method comprising: according to a target value (R) representing the amount of influence of the low-pressure EGR circuit EGR ) Rotational speed (n), intake efficiency (η) ASP ) And open-loop contribution (MFB50) of combustion index (MFB50) OL ) To determine a value for providing Spark Advance (SA) model ) The combustion model of (1); calculating a first closed-loop contribution to spark advance (Δ SA) from a combustion index (MFB50) MFB50 ) (ii) a Calculating a second closed loop contribution to spark advance (Δ SA) from an amount indicative of knock energy KNOCK ) (ii) a And by the spark advance value (SA) provided by the combustion model model ) And a first closed loop contribution (Δ SA) MFB50 ) Or alternativelySurrogate secondary closed loop contribution (Δ SA) KNOCK ) To calculate a target value (SA) of the spark advance angle to be operated obj )。)

1. A method for controlling combustion of an internal combustion engine (1), the internal combustion engine (1) having a plurality of cylinders (3) and a low pressure EGR circuit (EGR)_LP) The method comprises the following steps:

obtaining a rotational speed (n) and an intake efficiency (η) of an internal combustion engine (1)_ASP)；

By controlling the map and according to the rotational speed (n) and the intake efficiency (η)_ASP) To determine a representative low pressure EGR circuit (EGR)_LP) A first amount of opening (R) affecting the mixture flowing in the intake pipe (6)_EGR-OL)；

According to the quantity (E) indicative of the knock energy_detMAPO) to determine a value representative of a low pressure EGR loop (EGR)_LP) A first closed-loop quantity (Delta R) influencing the gas mixture flowing in the gas inlet line (6)_EGR-KNOCK)；

By a first ring opening amount (R)_EGR-OL) And a first closed-loop quantity (Δ R)_EGR-KNOCK) Sum to calculate a value indicative of a low pressure EGR circuit (EGR)_LP) Target value (R) of said quantity for influencing the gas mixture flowing in the gas inlet duct (6)_EGR-obj)；

According to a target value (R) of said quantity_EGR-obj) To determine a representative low pressure EGR circuit (EGR)_LP) Quantity (R) of influence on the gas mixture flowing in the gas inlet duct (6)_EGR)；

By controlling the map and according to the rotational speed (n) and the intake efficiency (η)_ASP) To determine an open-loop combustion index (MFB50) representing an engine angle at which 50% of the fuel mass is combusted in the cylinder;

in the design phase, according to said quantity (R)_EGR) Rotational speed (n), intake efficiency (η)_ASP) And an open-loop combustion index (MFB50) to determine a spark advance value (SA)_model) The combustion model of (1);

calculating a first closed loop spark advance (Δ SA) suitable for optimizing the efficiency of the internal combustion engine (1) from the open loop combustion index (MFB50)_MFB50)；

According to the quantity (E) indicative of the knock energy_det`MAPO) to calculate a second closed-loop spark advance (Δ SA) suitable for avoiding the occurrence of knock phenomena_KNOCK) (ii) a And

by spark advance value (SA) provided by combustion model_model) First closed loop spark advance (Δ SA)_MFB50) And a second closed loop spark advance (Δ SA)_KNOCK) To calculate a target value (SA) of the spark advance angle to be operated_obj)。

2. The method of claim 1, wherein said second closed loop spark advance (Δ SA)_KNOCK) Reducing spark advance values provided by combustion models(SA_model) And the first closed loop spark advance (Δ SA)_MFB50) Increasing or decreasing the spark advance value (SA) provided by the combustion model_model) (ii) a The method comprises the following steps: when the second closed loop spark advance (Δ SA)_KNOCK) Beginning to reduce spark advance value (SA) provided by combustion model_model) While, the first closed loop spark is advanced (Δ SA)_MFB50) Zeroed, frozen, or rounded to the current value.

3. The method of claim 1, further comprising the steps of:

according to a first closed loop quantity (Delta R) in a static state_EGR-KNOCK) Intake efficiency (eta) of the integral part of the PID/PI controller used in the method_ASP) And a rotation speed (n) by means of which a second opening quantity (R) is determined by means of an adaptive control map_EGR-ADT) (ii) a And

by a first amount of ring opening (RE)_GR-OL) Second amount of ring opening (R)_EGR-ADT) And a first closed-loop quantity (Δ R)_EGR-KNOCK) Sum to calculate a target value (R) for said quantity_EGR-obj)。

4. The method of claim 1, wherein the indication is used to determine a second closed loop spark advance (Δ SA)_KNOCK) Amount of knock energy (E)_detMAPO) is the knock energy (E) defined by the difference between the combustion noise and the limit value of the combustion noise_det)。

5. The method of claim 1, wherein the indication is used to determine a second closed loop spark advance (Δ SA)_KNOCK) Amount of knock energy (E)_detMAPO) is the Maximum Amplitude (MAPO) of the intensity of the pressure wave generated by combustion in the cylinder (3).

6. The method of claim 1, further comprising the steps of:

calculating the amount of knock energy (E) at the time of indicating the combustion cycle that has just occurred_detMAPO) and corresponding knock energyThe difference between the limit values; and

determining a first closed-loop quantity (Δ R) in case the difference or the contribution is smaller than a first threshold (S3)_EGR-KNOCK) (ii) a Or

Determining a second closed-loop spark advance (Δ SA) in case the difference or the contribution is greater than or equal to a first threshold (S3)_KNOCK)。

7. Method according to claim 6, characterized in that the difference is multiplied by an intervention constant of a PID or PI regulator, which intervention constant varies as a function of the difference.

8. The method according to claim 6, characterized in that it further comprises the steps of: advancing a second closed loop spark (Δ SA) in the event of a detected knock event_KNOCK) Rounded to a minimum.

9. The method of claim 1, wherein the combustion model is represented by a parabola whose formula is as follows:

SA_model＝a₂*MFB50²+a₁*MFB50+a₀

MFB50 flammability index;

SA_modela spark advance value provided by the combustion model.

10. The method of claim 9, wherein a is_iThe coefficients are expressed as follows:

a_i＝f_i(η_ASP,n)*g_i(R_EGR,η_ASP)[i＝0,1,2]

R_EGRindicating a low pressure EGR circuit (EGR)_LP) The amount of influence of (c);

n rotation speed;

η_ASPand (4) air intake efficiency.

11. The method of claim 1, wherein the combustion model is represented by a parabola whose formula is as follows:

SA_model＝a₅*MFB50²+a₄*MFB50+a₃+f_EGR(R_EGR,η_ASP)

MFB50 flammability index;

R_EGRindicating a low pressure EGR circuit (EGR)_LP) The amount of influence of (c);

η_ASPthe air intake efficiency; and

SA_modela spark advance value provided by the combustion model.

12. The method of claim 11, wherein a is_iThe coefficients are expressed as follows:

a_i＝f_i(η_ASP,n)[i＝3,4,5]

n rotation speed; and

η_ASPand (4) air intake efficiency.

13. The method of claim 1, wherein the combustion model is represented as follows:

SA_model＝MFB50+f₆(η_ASP,n)+f₇(R_EGR,η_ASP)*f₈(η_ASP,n)

MFB50 flammability index;

R_EGRindicating a low pressure EGR circuit (EGR)_LP) The amount of influence of (c);

η_ASPthe air intake efficiency;

n rotation speed; and

SA_modela spark advance value provided by the combustion model.

Technical Field

The invention relates to a method for controlling combustion of an internal combustion engine.

Background

As is known, in an internal combustion heat engine, it is also proposed to supply water other than fuel into a combustion chamber defined in a cylinder.

In internal combustion engines, water injection systems involve introducing water into the engine through an intake duct or directly into the combustion chamber, in the form of a spray or mixed with fuel, to cool the air/fuel mixture and thus increase resistance to knock phenomena. Typically, the water supply system comprises a tank filled with demineralized water (to avoid scale formation). Typically, the tank may be refilled from outside the vehicle, or the tank may also be refilled with condensed water from the air conditioning system, with condensed water from the exhaust gas or even by conveying rainwater. Furthermore, the tank is preferably provided with electrical heating means (i.e. with an electrical resistance which generates heat by joule effect when an electrical current flows) for melting any ice when the external temperature is particularly severe.

Water has a high latent heat of vaporization; in other words, the water changes from the liquid state to the gaseous state requiring a large amount of energy. When water at room temperature is injected into the intake duct, it absorbs heat from the incoming air and metal walls, evaporating, thereby cooling the feed. Thus, the engine draws cooler air, in other words, richer air, improving volumetric efficiency and reducing the likelihood of knocking, and in addition, may inject more fuel. During compression, water in the form of very small droplets evaporates and absorbs heat from the compressed air, thereby cooling and reducing the pressure of the compressed air. After compression, combustion occurs and produces further benefits: during combustion, a large amount of heat is formed, which is absorbed by the water, thereby lowering the peak temperature of the cycle and thereby reducing the formation of nitrogen oxides (NOx) and the heat that must be absorbed by the engine walls. This evaporation also converts a portion of the heat of the engine (which would otherwise be wasted) into pressure, which is caused precisely by the steam formed, thus increasing the thrust on the piston, and also increasing any energy flow into the turbine to the exhaust (moreover, the turbine will benefit from a reduction in the exhaust gas temperature, since the heat is absorbed by the additional water).

However, there is still an increasing need to avoid the presence of an excessively bulky water supply system on the vehicle without compromising thermodynamic efficiency.

Disclosure of Invention

It is therefore an object of the present invention to provide a method for controlling the combustion of an internal combustion engine which does not have the above-mentioned disadvantages and which is particularly easy and inexpensive to implement.

According to the invention, a method for controlling combustion in an internal combustion engine having a plurality of cylinders and a low-pressure EGR circuit is provided with the steps of:

acquiring the rotating speed and the air intake efficiency of the internal combustion engine;

determining a first open loop amount representing an influence of the low-pressure EGR circuit on the mixture gas flowing in the intake pipe, by controlling the map and according to the rotation speed and the intake efficiency;

determining a first closed-loop quantity representing an effect of the low-pressure EGR circuit on a gas mixture flowing in the intake conduit, from the quantity indicative of knock energy;

calculating a target value of the amount representing the influence of the low-pressure EGR circuit on the gas mixture flowing in the intake pipe by the sum of the first open-loop amount and the first closed-loop amount;

determining an amount representing the influence of the low-pressure EGR circuit on the gas mixture flowing in the intake conduit, from a target value of said amount;

determining an open-loop combustion index representing an engine angle at which 50% of the fuel mass is combusted in the cylinder, based on the rotational speed and the intake efficiency, by controlling the map;

determining a combustion model providing a spark advance value based on the quantity, the rotational speed, the intake efficiency, and the open-loop combustion index during a design phase;

calculating a first closed loop spark advance suitable for optimizing the efficiency of the internal combustion engine based on the open loop combustion index;

calculating a second closed loop spark advance adapted to avoid occurrence of the knock phenomenon based on the amount of the indicated knock energy; and

a target value of the spark advance angle to be operated is calculated by a sum of the spark advance value provided by the combustion model, the first closed-loop spark advance and the second closed-loop spark advance.

Drawings

The invention will now be described with reference to the accompanying drawings, which illustrate non-limiting embodiments of the invention, and in which:

figure 1 is a schematic view of an internal combustion engine provided with an electronic control unit implementing the subject of the combustion control method of the invention; and

figure 2 is a block diagram representing a combustion control strategy implemented by the engine control unit of figure 1.

Detailed Description

In fig. 1, reference numeral 1 denotes as a whole an internal combustion engine for a road vehicle (automobile or motorcycle) (not shown) provided with a plurality of cylinders 2, in particular four cylinders, defining in the cylinders 2 respective variable-volume combustion chambers and four injectors 3 which inject fuel, preferably gasoline, directly into the cylinders 2, each cylinder 2 being connected to an intake manifold 4 via at least one respective intake valve (not shown) and to an exhaust manifold 5 via at least one respective exhaust valve (not shown).

The intake manifold 4 receives a gas mixture comprising exhaust gases (as better described below) and fresh air, i.e. air coming from the outside environment through an intake duct 6, the intake duct 6 being provided with an air filter 7 for the flow of fresh air and being controlled by a throttle valve 8. Downstream of the air filter 7, there is also arranged along the intake duct 6 a mass flow sensor 7 (better known as an air flow meter).

An intercooler 9 (the function of which is to cool the intake air) is arranged along the intake duct 6 (preferably integrated into the intake manifold 4). The intercooler 9 is connected to a coolant conditioning circuit used in the intercooler 9, which includes a heat exchanger, a feed pump, and a regulating valve arranged along a pipe parallel to the intercooler 9. The exhaust manifold 5 is connected to an exhaust pipe 10, which exhaust pipe 10 supplies exhaust gas produced by combustion to an exhaust system, which exhaust system releases the gas produced by combustion into the atmosphere, and typically comprises at least one catalyst 11 and at least one muffler (not shown) arranged downstream of the catalyst 11.

The supercharging system of the internal combustion engine 1 includes: a turbocharger 12 provided with a turbine 13, the turbine 13 being arranged along the exhaust pipe 10 to rotate at a high speed by the exhaust gas discharged from the cylinders 3; and a turbocharger 14, which is arranged along the intake duct 6 and is mechanically connected to the turbine 13 to be driven in rotation by the turbine 13 itself to increase the air pressure in the intake duct 6.

The internal combustion engine 1 is controlled by an ECU electronic control unit that monitors the operation of all the components of the internal combustion engine 1.

According to a preferred variant, the internal combustion engine 1 finally comprises low-pressure EGR_LPCircuit of low pressure EGR_LPThe circuit in turn comprises a bypass duct 15, which originates from the exhaust duct 10, preferably downstream of the catalyst 11 and flows into the intake duct 6 downstream of the air flow meter 7; the bypass conduit 15 is connected in parallel with the turbocharger 12. An EGR valve 16 is arranged along the bypass duct 15, the former EGR valve 16 being adapted to regulate the flow of exhaust gas flowing through the bypass duct 15. A heat exchanger 17 is also arranged along the bypass conduit 15 upstream of the valve 16, the function of the heat exchanger 17 being to cool the gases leaving the exhaust manifold 5 and entering the supercharger 14.

The strategy implemented by the ECU electronic control unit for optimizing the combustion inside the internal combustion engine 1 is described below.

Specifically, the following amounts are defined:

η_ASPintake efficiency (and representing engine load or alternatively representing indicated mean pressure or indicated drive torque or drive brake torque) and from the mass m of air trapped in the cylinder 2 for each combustion cycle_AIRAnd the mass m of air trapped in the cylinder 2 for each combustion cycle under reference conditions (i.e. at a temperature of 298 ° K and a pressure of one atmosphere)_{AIR_REF}The ratio therebetween;

n the rotational speed of the internal combustion engine 1;

E_detknock energy (preferably defined by the difference between the combustion noise determined by appropriate processing of the microphone or accelerometer signal in the angle detection window near the top dead center, TDC, point and the limit combustion noise corresponding to the ninety-eight percent of the non-knocking combustion cycle and provided by the map stored inside the ECU electronic control unit as a function of the engine point and the cylinder 2);

E_det-obja limit value of knock energy determined from the engine point;

maximum amplitude of the intensity of the pressure wave generated by combustion in the cylinder 2 by MAPO (maximum amplitude pressure oscillation);

MAPO_obja limit value of the maximum amplitude of the intensity of the pressure wave generated by combustion in the cylinder 2 determined in accordance with the engine point;

MFB50 represents the combustion index (50% burned mass fraction) at engine angle (i.e., crank angle) at which 50% of the fuel mass is burned in cylinder 2;

SA spark advance angle; and

SA_obja target value of the spark advance angle to be operated.

Indicating (representing) low-pressure EGR circuit EGR_LPR of influence on the gas mixture flowing in the inlet duct 6_EGRThe amount (or ratio) is also defined as follows:

R_EGR＝M_{EGR_LP}/M_TOT

M_TOTmass of mixed gas flowing in the intake duct 6, whichCalculated as mass M of fresh air from the outside environment flowing in the intake duct 6_AIRAnd EGR flowing in intake pipe 6 through a low-pressure circuit_LPMass M of recirculated exhaust gas_{EGR_LP}Summing; and

M_{EGR_LP}EGR flowing in intake pipe 6 through low-pressure circuit_LPMass of recirculated exhaust gas.

In the following description, R_EGRThe quantities (used for example in combustion models, as better described in the following description) can alternatively be determined by the documents EP-a1-3040541, EP-B1-3128159, IT2016000115146, IT2016000115205 or by the outflow model of the EGR valve 16.

In more detail, as shown in FIG. 2, R_EGRThe quantity represents the EGR from the low-pressure circuit relative to the (total) gas mixture flowing in the intake conduit 6_LPDirect measurement or estimation of the influence of the gas flow; EGR from low pressure loop_LPIs defined by the position of the EGR valve 16 and the conditions (in particular pressure, temperature) of the internal combustion engine 1; the position of the EGR valve 16 is calculated by the engine control unit based on R as shown below_{EGR_OBJ}A target value for the quantity (or ratio). In the alternative, according to R_{EGR_OBJ}Target value of quantity (e.g. by pair R by first order filter_{EGR_OBJ}Filtering the target value of the quantity) to determine (estimate) R_EGRAmount of the compound (A).

As shown in fig. 2, the combustion model used is based on the (known) intake efficiency η_ASPSpeed n (known) of internal combustion engine 1, combustion indices MFB50 and R_EGRQuantity to calculate spark advance SA_model. In other words, the spark advance SA is calculated_modelThe combustion model of (a) may be expressed as:

SA_model＝f(MFB50，η_ASP，n，R_EGR)

according to a first embodiment, the combustion model may be represented by a parabola whose formula is as follows:

SA_model＝a₂*MFB50²+a₁*MFB50+a₀

wherein SA_modelAnd MFB50 have the meaning previously described, and a_iThe coefficients can be expressed as follows:

a_i＝f_i(η_ASP,n)*k_i(R_EGR,η_ASP)[i＝0,1,2]

wherein R is_EGRN and η_ASPHave the previously introduced meanings. The electronic control unit knows n and eta_ASPThe value is obtained.

And f_iAnd k_iRepresents a map experimentally established at an initial stage, which may be relative to η_ASPN and R_EGRA change is made.

According to a second embodiment, the combustion model may be represented by a parabola whose formula is as follows:

SA_model＝a₅*MFB50²+a₄*MFB50+a₃+f_EGR(R_EGR,η_ASP)

wherein SA_modelAnd MFB50 have the meaning previously described, and a_iThe coefficients can be expressed as:

a_i＝f_i(η_ASP,n)[i＝3,4,5]

wherein R is_EGRN and η_ASPHave the previously introduced meanings. The electronic control unit knows n and eta_ASPA value; f. of_iRepresents a map experimentally established at an initial stage, which may be relative to a_iThe coefficients are changed.

f_EGRThe function also represents a map experimentally established in the initial phase, which may be relative to R_EGRAnd η_ASPThe amount is varied.

According to a third embodiment, the combustion model may be represented as follows:

SA_model＝MFB50+f₆(η_ASP,n)+f₇(R_EGR,η_ASP)*f₈(η_ASP,n)

wherein SA_model，MFB50，R_EGRN and η_ASPHave the previously introduced meaningsAnd n and eta are known to the electronic control unit_ASPThe value is obtained.

f₆And f₈The function represents a map experimentally established at an initial stage, which may be relative to n e and η_ASPThe amount is varied.

f₇The function also represents a map experimentally established in the initial phase, which may be relative to R_EGRAnd η_ASPThe amount is varied.

Now, how to determine the combustion indices MFB50 and R will be described_{EGR_OBJ}Amount of the compound (A).

The combustion index MFB50 is determined by the open-loop contribution; specifically, MFB50_OLA map according to the intake efficiency η of the internal combustion engine 1 is stored in the ECU electronic control unit_ASPAnd rotational speed n provides a combustion index MFB 50.

Instead, the quantity R is determined by adding the open-loop contribution and the closed-loop contribution (i.e. in the feedback)_{EGR_OBJ}。

Open loop contribution providing amount R_{EGR_OL}(ii) a In particular, REGR_OLA map according to the intake efficiency η of the internal combustion engine 1 is stored in the ECU electronic control unit_ASPAnd a rotational speed n providing R_{EGR_OL}Amount of the compound (A).

According to a first variant, the energy E of the knock is obtained by subtracting the energy E of the combustion cycle that has just taken place_detLimit value E related to knock energy_det-objMaking a comparison to obtain R_{EGR_OBJ}The closed-loop contribution of the quantity.

Alternatively, by comparing the maximum amplitude MAPO of the intensity of the pressure wave generated by combustion in the cylinder 3 with the limit value MAPO of the maximum amplitude of the intensity of the pressure wave generated by combustion in the cylinder 3_objMaking a comparison to obtain R_{EGR_OBJ}The closed-loop contribution of the quantity.

Knock energy E from the combustion cycle just taking place_detAnd limit value E of knock energy_det-objThe result of the comparison therebetween (or correspondingly the maximum amplitude MAPO of the intensity of the pressure wave generated by combustion in the cylinder 3 and the maximum amplitude of the intensity of the pressure wave generated by combustion in the cylinder 3Limit value MAPO_objMaking a comparison) to distinguish the type of control to be implemented; for example, the control type is accomplished by differentiating the intervention constants of a PID (or PI) regulator (PID (or PI) regulator).

In particular, the strategy comprises a regulator block (governor block)3, the regulator block 3 receiving the knock energy E through the combustion cycle that has just taken place_detAnd limit value E of knock energy_det-objThe difference between (or respectively at the maximum amplitude MAPO of the intensity of the pressure wave to be generated by combustion in the cylinder 3 and the limit value MAPO of the maximum amplitude of the intensity of the pressure wave to be generated by combustion in the cylinder 3_objThe difference between) multiplied by the corresponding intervention constant of the PID regulator, as an input. Based on the value of said contribution, the regulator block 3 decides how to intervene to reduce the risk of knocking. In particular, if the contribution is less than the threshold S3 (preferably adjustable and variable according to the engine point), this means that reduced corrections are required to avoid the occurrence of knock phenomena. In this case, the regulator block 3 calculates Δ R_EGR-KNOCKA differentiation of the quantity adapted to avoid the occurrence of knocking phenomena.

On the other hand, if the contribution exceeds the threshold value S3, this means that a large correction is required to avoid the occurrence of the knocking phenomenon. In this case, the adjuster block calculates the spark advance Δ SA_KNOCKIs adapted to avoid the occurrence of knocking phenomena. In this case, R, as better described in the following description_EGR-OBJThe amounts are rounded to the limit.

Finally, if a knock event (DET) is detected, it is immediately rounded to a maximum value without waiting for the response of the PID regulator, so that the regulator block 3 calculates the spark advance Δ SA_KNOCKIs adapted to avoid the occurrence of knocking phenomena.

One preferred variant comprises a further open-loop contribution, which provides an adaptation quantity R_EGR-ADT(ii) a Specifically, a map according to the intake efficiency η of the internal combustion engine 1 is stored in the ECU electronic control unit_ASPAnd speed n to provide an adaptive quantity R_EGR-ADT. Preferably, the REGR is updated according to the integral part of the PID or PI controller used in the closed-loop contribution_ADTMap to determine Δ R under static conditions_EGR-KNOCKThe differential of the quantity.

Thus, by contributing R to the two open loops_EGR-ADT(if present) and R_EGR-OLContribution to the closed loop Δ R_EGR-KNOCKAdd to determine R_{EGR_OBJ}Amount of the compound (A).

The strategy also includes a closed loop contribution that optimizes efficiency. In particular, by comparing the combustion index MFB50 determined by means of the open-loop contribution with the estimated value of the combustion index MFB50_estTo achieve said closed-loop contribution.

According to the combustion index MFB50 and the estimated value of the combustion index MFB50_estThe comparison therebetween distinguishes the type of control to be implemented. For example, the type of control is accomplished by differentiating the intervention constants of the PID (or PI) regulator.

Specifically, the strategy includes a regulator block 4, the regulator block 4 receiving a signal passing through a combustion index MFB50 (or more specifically, an open-loop combustion index MFB50)_OL) And an estimate of the flammability index MFB50_estThe difference between the two is multiplied by the intervention constant of the PID or PI regulator to calculate the contribution as an input. Depending on the value of said contribution, the regulator block 4 decides how to intervene to optimize the efficiency of the internal combustion engine 1. In particular, if the contribution is greater than the threshold S4 (which is preferably adjustable and variable according to the engine point), this means that a large correction is required to optimize the efficiency of the internal combustion engine 1. In this case, governor block 4 calculates spark advance Δ SA_MFB50Is adapted to optimize the efficiency of the internal combustion engine 1.

Obviously, in this case, too, in order to control knocking and avoid the occurrence of the knocking phenomenon, the spark advance Δ SA_KNOCKDifferential reduction of spark advance SA provided by the combustion model_model. Conversely, to optimize the efficiency of the internal combustion engine 1, the spark advance Δ SA_MFB50Differential increase of spark advance SA provided by the combustion model_model. Protection of the internal combustion engine 1 is preferred over internal combustion engines in order to avoid the occurrence of knocking phenomenaThe efficiency of the engine 1; therefore, the spark advance Δ SA when it is appropriate to avoid the occurrence of the knocking phenomenon_KNOCKTo reduce the spark advance SA provided by the combustion model_modelWill be adapted to optimize the spark advance Δ SA of the efficiency of the internal combustion engine 1_MFB50The differential of (a) is set to zero (or is greatly reduced). In other words, the strategy includes that Δ SA is achieved once spark advance_KNOCKBegins to reduce the spark advance value SA provided by the combustion model_modelSpark is advanced by Δ SA_MFB50The differential of (a) is zeroed (or rounded to a value close to zero).

Thus, the target to be achieved advances SA_objBy two different contributions (spark advance SA provided by the combustion model_modelAnd a spark advance Δ SA suitable for optimizing the efficiency of the internal combustion engine 1_MFB50Or alternatively a spark advance Δ SA adapted to avoid the occurrence of knock phenomena_KNOCKDifferential of (d) is calculated.

As expected from the foregoing discussion, the intake efficiency η_ASPInstead, it may be replaced by an indicated mean pressure or an indicated driving torque or driving braking torque or generally by any quantity indicative of the engine load.

The combustion control method described above has many advantages, since it does not require a high computational burden, is robust, and allows in particular to avoid the presence of water on the vehicle without compromising thermodynamic efficiency, while allowing to avoid the occurrence of knock phenomena in a reliable manner.