WO2016156699A1

WO2016156699A1 - Method for automatically starting a spark-ignition internal combustion engine

Info

Publication number: WO2016156699A1
Application number: PCT/FR2016/050625
Authority: WO
Inventors: Ludovic Lefebvre; Xiao Mei JIANG
Original assignee: Peugeot Citroen Automobiles Sa
Priority date: 2015-04-02
Filing date: 2016-03-22
Publication date: 2016-10-06
Also published as: FR3034468A1; FR3034468B1

Abstract

The invention relates to an internal combustion engine automatic start method including steps that involve controlling the power-up of an electrical machine; setting, on an air actuator, a lower opening cross-section value to a reference value (S1'); comparing the speed (N) of the engine with a speed threshold (N1) and comparing a pressure (P) in the intake manifold with a threshold (P1); controlling injection of a fuel load (M) and ignition advance to a maximum value (AA1) when the engine speed (N) rises above the speed threshold (N1) and the pressure (P) in the intake manifold falls below the threshold (P1); turning off the electrical machine when a first combustion occurs; and controlling the operation parameters of the engine.

Description

METHOD FOR AUTOMATICALLY STARTING AN INTERNAL COMBUSTION ENGINE WITH COMMAND IGNITION

The invention relates to a method of automatic starting of an internal combustion engine in a motor vehicle, in order to reduce the fuel consumption during the start-up phases.

[0002] The evolution of environmental regulations towards lower and lower levels of pollutant emissions and greenhouse gases, as well as the increasing demand from customers for motor vehicles with reduced fuel consumption, have led to in recent years, the electrification of powertrains. These powertrains can be electrified at different levels. Thus, some of these powertrains are hybrid and include an automatic start and stop function, commonly referred to as the "Stop and Start", of the internal combustion engine, also referred to as "heat engine" in this document.

The "Stop and Start" function allows the stopping and restarting of the engine of a vehicle according to predefined strategies, for example in case of prolonged stopping of the vehicle or when receiving a command from starting, following the automatic shutdown of the engine. Advantageously, such a function makes it possible to reduce fuel consumption in an urban environment. This function is particularly found in motor vehicles

- "micro-hybrid". In these vehicles, the powertrain comprises a heat engine, as well as an automatic start and stop function, which can be performed by an electric machine, such as a starter (possibly reinforced compared to conventional starters), or an alternator -starter ;

- "mild-hybrid". In these vehicles, the powertrain is equipped with an electric machine that performs better than "micro-hybrid" systems. Thus, in addition to the automatic stop and start function, the electric machine participates in the movement of the vehicle by providing an additional mechanical power to that of the heat engine during the acceleration phases, and allows, moreover, the recovery of energy kinetics of the vehicle (via transformation into electrical energy and storage in batteries) during deceleration and braking phases;

"Full-hybrid". In these vehicles, the powertrain is equipped with an electric machine that performs better than "mild-hybrid" systems. In particular, the use of higher power and energy batteries allows driving in pure electric mode, generally from 1 to 20 km, the heat engine then being cut during this phase;

- "full hybrid plug-in". These vehicles include, compared to full-hybrid vehicles, a battery of higher capacity, allow to store / release more power and electrical energy and propose, moreover, a connection to the electric network to recharge the battery between two rollings. It thus becomes possible, in pure electric mode, to travel distances ranging from 15 to 50 km and to reach a speed of 130 km / h.

Currently, "micro-hybrid" motor vehicles have, compared to vehicles with unhybridized powertrains, fuel consumption gains of up to 15 to 20% in urban traffic.

However, the automatic start and stop functions of these vehicles, have penalties in terms of electricity consumption, fuel, and emission of pollutants at each restart of the engine. Thus, during the application of an approval cycle, such as the European ECE-EUDC driving cycle, the mass of fuel consumed during the restart phase by the automatic start and stop function, currently represents 1% of the fuel consumption. total mass of fuel consumed over the entire cycle.

This justifies the implementation of strategies to optimize the conditions

automatic shutdown of the engine, ensuring, for example: stable combustion, controlled acoustic and vibration levels, primed decontamination elements, a sufficiently long vehicle stopping time;

- starting or restarting phases of the engine after stopping, for example by checking: o fuel consumption and pollutant emissions via the various components and parameters accessible for the air loop and for combustion;

o the restarting quality, such as the time to reach the stabilized engine idling speed, the values of the exceeded engine idle speed (so-called "over shoot" values), the total duration of (re) start, as well as the resulting acoustic and vibratory levels.

An example of a strategy for optimizing a start function is described in document FR2797473. This document proposes a method of starting a spark ignition internal combustion engine, consisting, during a motor start command, of controlling the starting of an electric machine, and imposing on the adjustment member of intake manifold airflow, and ignition advance, minimum positions. When a speed threshold of the electric machine is crossed by the top, and a pressure threshold in the inlet distributor is crossed by the bottom, fuel is then injected. The electric machine is thereafter cut off, and the engine operating parameters are regulated to establish its idle speed, the advance is notably increased when the engine enters an idle control phase.

Such a strategy remains however perfectible in many points. It is particularly necessary, given current regulations, to further reduce fuel consumption, pollutant emissions, as well as improve the acoustic and vibration of the powertrain. It would also be particularly advantageous, after receiving a start command, to be able to reach the stabilized engine idling speed more quickly, and thus allow the vehicle to be started more quickly.

A first object is to meet all the aforementioned drawbacks.

A second object is to propose a strategy optimizing the start or restart of a petrol engine with or without an automatic start and stop function, and this for any type of vehicle, hybrid or not.

A third object is to reduce fuel consumption during the startup or restart phases. A fourth object is to improve the acoustic and vibration behavior of the powertrain.

For this purpose, it is proposed, in a first aspect, a method for automatically starting a spark ignition internal combustion engine for a motor vehicle, the engine being coupled to an electric machine capable of allowing its driving, the motor being connected at the input to an intake distributor and at the outlet to an exhaust manifold, an air actuator being arranged upstream of the intake distributor, in particular so as to regulate the flow of air through that - ci, this method comprising steps of:

when receiving a start command, controlling the powering up of the electrical machine, in particular so as to start the motor drive;

when the starting of the motor starts, to impose on the air actuator a first value of opening section, less than a reference value, this reference value being calculated according to the thermal state of the engine and being in particular able to guarantee the success of a first combustion from the occurrence of a first combustion cycle in a cylinder of the engine;

comparing the engine speed with a first speed threshold, and comparing the pressure in the intake distributor with a first pressure threshold;

controlling the injection of a mass of fuel into the engine and controlling the ignition advance from a zero initial value to a maximum value, when the first speed threshold is crossed upwards by the engine speed and that the first pressure threshold is crossed down by the pressure in the intake manifold;

cutting the electric machine, following the occurrence of a first combustion in a cylinder of the engine;

- Then regulate the engine operating parameters to converge to a set idle speed, including able to allow the establishment of engine idling speed.

Within the meaning of the invention, the term "control the ignition advance from a zero initial value to a maximum value" is understood to mean that the ignition advance is controlled first at a value initial zero then progressively to a maximum value. [0015] Advantageously, this method further comprises the steps of:

counting the number of top engine points for each cylinder of the engine and compare that number with a predefined number;

when the number of motor points measured reaches the predetermined number and in the absence of a first combustion, to impose on the air actuator the reference value for opening section, so as to carry out a first combustion in a cylinder of the engine, then to control a gradual decrease of this reference value of opening section to the first value of opening section.

Advantageously, in this method, the fuel mass is injected for a duration, this duration being controlled so as to:

being held constant at a first value when the value of the ignition advance is controlled between its initial null value and its maximum value;

being progressively decreased from the first value to a second value corresponding to the injection duration applied for the engine idling speed, as soon as the value of the ignition advance has reached its maximum value.

Advantageously, in this method, the fuel mass is injected at a constant value from the start of its injection to the occurrence of a first combustion in a cylinder of the engine. As further detailed with the aid of the figures, the mass of fuel injected is preferably injected at a constant value until the occurrence of the first combustion and then varies throughout the start-up phase, until the regulation phase idle speed of the engine, where the injected fuel mass converges gradually and quickly to another value.

Advantageously, in this method, between an instant of occurrence of a first combustion in a cylinder of the engine and a moment of crossing up the idle speed set by the engine speed.

the opening section value of the air actuator is progressively controlled to a second opening section value smaller than the first opening section value; the injected fuel mass is gradually increased until reaching a maximum value.

Advantageously, in this process, as soon as the maximum value of fuel mass is reached, the mass of fuel is controlled so as to progressively converge towards a lower value, this lower value corresponding to the mass of fuel injected during the idle speed of the engine.

Advantageously, in this process, when a second pressure threshold, lower than the first pressure threshold is crossed down by the pressure in the intake manifold,

the opening section value of the air actuator is progressively controlled to a third opening section value smaller than the second opening section value;

the value of the ignition advance is progressively controlled from its maximum value to a second value less than the maximum value.

Advantageously, this process comprises

detecting a control phase of the engine idling speed by comparing the engine speed with a set value crossed down;

the progressive control of the ignition advance towards a final value, lower than the second value, as soon as the occurrence of the regulation phase of the engine idling speed is detected.

It is proposed, according to a second aspect, a computer fitted to a motor vehicle, configured to apply the automatic starting method of an engine summarized above.

Other objects and advantages of the invention will become apparent in the light of the description of embodiments, given below with reference to the accompanying drawings in which:

- Figure 1 illustrates a motor vehicle comprising a motor and a computer programmed to regulate operating parameters of an engine according to various embodiments;

FIG. 2 illustrates the regulation of an opening value of the air actuator of an intake distributor of an engine according to various embodiments; FIG. 3 illustrates the regulation of operating parameters of an engine according to various embodiments.

In Figure 1 is shown a vehicle 100 automobile comprising a spark ignition internal combustion engine 1 (designation referring to the combustion that characterizes it) or more commonly called engine 1 gasoline. The engine 1 comprises at least one cylinder defining a combustion chamber, which is associated in an upper portion, an ignition device, such as a spark plug, to produce the spark necessary for the combustion of an air / fuel mixture . The cylinder is on the one hand associated with an intake valve which controls an intake of air or air / fuel mixture inside the combustion chamber, and on the other hand, with an exhaust valve which controls the evacuation, out of the combustion chamber, of exhaust gases resulting from the combustion of the air / fuel mixture.

Each cylinder of the engine 1 is connected to the intake manifold and the exhaust manifold, respectively via an intake manifold and an exhaust manifold, allowing the admission of air or of the air / fuel mixture and the exhaust of the combustion gases through each cylinder. The exhaust manifold is, for its part, connected to a catalyst for which there are arranged upstream and downstream probes for determining the flow of air through and the mass of oxygen present in the latter. In the case of an indirect injection engine, the fuel mass is injected by injectors into the intake manifolds, while in the case of a direct injection the fuel mass is directly injected into each cylinder. Furthermore, an air actuator, such as a motorized throttle valve, is arranged upstream of the intake distributor of the engine 1 so as to regulate the flow of air through it, and therefore the mass of circulating air to the different cylinders of the engine 1.

The engine 1 spark ignition is controlled by a computer 2 (also called engine control), the computer 2 being programmed to best meet the will of the driver, retransmitted including via an accelerator pedal. Thus, the computer 2 receives various information, and in particular that from a sensor positioned on the accelerator pedal, this information allowing it to control in particular the operating speed of the engine 1. The spark ignition engine 1 operates in a four-stroke cycle defined in the following order: an intake, a compression at the end of which take place the ignition and combustion of the air / fuel mixture, a relaxation and a exhaust.

The work produced by the spark ignition engine 1 comes from the combustion, initiated by the ignition device of the air / fuel mixture compressed within the cylinder by an alternately moving piston, between an extreme high position and a low extreme position, relative to the cylinder, respectively called position High Dead Point (PMH) and position Dead Point Low (PMB). The reciprocating movement of the piston allows the rotation of a crankshaft by means of a connecting rod connecting the piston to the crankshaft, the movement of the crankshaft being then transmitted to the wheels via different mechanisms.

During an engine cycle, ignition of the air / fuel mixture, via the ignition device, occurs upstream of the piston position PMH at the end of the compression phase. In order to calibrate the ignition, the engine manufacturers define a parameter called "ignition advance" corresponding to an angular difference (expressed for example in degrees), having for reference the crankshaft, between the moment of ignition and the ignition. moment of the passage of the piston to the top dead center (TDC) position, the top dead center position (TDC) of the piston corresponding to the reference position.

Advantageously, the computer 2 is connected with different sensors that provide real-time data on the vehicle 100 automobile, and in particular on the engine 1. Among these data, we find in particular:

the speed N of the engine: it corresponds to the number of rotation performed by the engine 1, and more precisely by the crankshaft, per unit of time. It is generally expressed in rpm and is measured by a rotational speed sensor;

the engine temperature: it corresponds to the coolant temperature (for example a water / antifreeze mixture), or the temperature of the lubricating oil at the cylinder, or the temperature of the material of a sensitive component of the engine 1 (eg an area of the breech). It is generally measured by a temperature probe; the position of the accelerator: it corresponds to the level of depression of the accelerator pedal, this depression being generally measured by a position sensor on the accelerator pedal;

the pressure P in the intake manifold: it corresponds to the pressure of the air in this element, the latter being measured by a sensor placed in the intake manifold;

the air flow through the catalyst and the oxygen content in the catalyst: they are measured by the probes placed upstream and downstream of the catalyst, and allow the computer 2 to evaluate the mass of oxygen stored in the catalyst; catalyst.

An electric machine is, moreover, coupled to the motor 1 to allow its drive and its rotation when receiving a start command or restart by the computer 2. A start command is, to As an example, generated when the ignition key is pressed or by pressing a start button. A restart command is, for example, generated when the brake pedal is released, when the accelerator pedal is depressed or when the clutch pedal is depressed, or when the lever position is changed. of gear change, following a stop of the vehicle 100 automobile. The electric machine is, for example, a starter or an alternator-starter. In the latter case, the electric machine supplies electrical energy to different electrical consumers of the automobile vehicle 100 (for example: pumps, compressors, sensors, actuators) once the start-up process has been finalized. All or part of these consumers can also be powered electrically by an external power source, independent of the alternator-starter, such as a high or low voltage electric battery.

Advantageously, thanks to the feedback of the various sensors, the computer 2 develops and controls control strategies of the engine 1, in particular via

the generation of control signals controlling the injection (for example: mass of fuel injected, duration of the injection);

generating control signals controlling the start-up or shutdown of the electric machine driving the engine 1 during start-up; generating control signals controlling each ignition device, for independently controlling the ignition of each cylinder, and therefore the ignition timing;

the generation of control signals controlling the air actuator (for example: motorized throttle valve) upstream of the intake distributor, thus allowing the regulation of the air pressure in this member.

FIG. 2 shows, by way of example, two diagrams a), b), each illustrating on the ordinate the evolution of the opening section S (also called passage section) of the air actuator. of the intake distributor, driven by the computer 2, as a function of the time t on the abscissa. Diagram a) illustrates the state of the art for the sake of understanding, while Diagram b) illustrates exemplary embodiments, having various advantages with respect to this state of the art.

With reference to diagram a), at a time t0, the computer 2 receives a start command, and then controls the driving of the motor 1 by the electric machine. The calculator 2 furthermore calculates, at this instant, an opening value / section for the air actuator, such as an effective passage section in degrees or in square millimeters, in order to regulate the flow of air entering towards the air actuator. intake distributor and the various cylinders of the engine 1. In the state of the art, this value is a reference value S1 ', able to guarantee the success of a first combustion from the occurrence of a first cycle of combustion in a cylinder of the engine 1. The value S1 'referential is a value calculated in particular according to the thermal state of the engine 1 and the depression of the accelerator pedal, and can therefore vary depending on the engine. Likewise, depending on the temperature of the engine 1, and the nature of the fuel (for example: alcohol content in gasoline), the computer 2 determines a period T of application for this value S1 'referential. Generally, the calculation of the reference value S1 'by the calculator 2 is based on the information reported by the various sensors, mathematical models and / or prerecorded measurement tables, and takes into account for its calculation: the calculation of a opening value (arrow 21) of the air actuator (throttle passage section) to compensate for overall engine losses, for example friction;

the calculation of a value (arrow 22) for opening the air actuator making it possible to generate a reserve of torque. Such a reserve of torque, generally takes into account, during its calculation, the torque taken by each electrical consumer, and a couple to ensure the takeoff of the vehicle 100 automobile;

the calculation of a value (arrow 23) for opening the air actuator allowing the realization of the High Pressure Indicated Middle Torque, commonly referred to as the CMI HP acronym, which is a function of the engine speed N 1 and the position of the accelerator pedal;

the calculation of a value (arrow 24) of opening correction of the air actuator, as a function of the thermal state of the engine 1. This value is determined by the computer 2 for injection parameters (ex : injection time / injection time, ignition advance value) and air circulation management (opening of the throttle valve, air volume in the intake manifold), these operating parameters of the engine 1 being fixed during an open loop phase by the computer 2. The open loop here corresponds to a period during the start of the vehicle 100, for which the parameters of injections and management of the air flow do not do not self-regulate between each other: the computer 2 sends setpoint values, and the results obtained via the application of these instructions do not affect the control strategy at the next time step.

In contrast, during a subsequent closed-loop phase, the computer 2 jointly takes into account the results obtained via the application of the different operating parameters of the engine 1, in order to compute at the time step following the values of these parameters; - The calculation of a compensation value (arrow 25), commonly referred to as the "offset" anglicism, for opening the air actuator according to the thermal state of the engine 1.

Thus, in the diagram a) representing the state of the art, the reference value S1 'is controlled by the computer 2, as the opening section of the air actuator during the predetermined period T . Advantageously, the period T is determined so as to cover the occurrence of a first combustion (not shown), as well as the instant ti where the motor 1 rotates autonomously, that is to say without training the electric machine, which is then cut. At the end of this period T, the value (arrow 25) of compensation ("offset") opening of the air actuator is then gradually reduced (arrow 26) to a second value S2, corresponding to a cancellation of this offset. Commonly, the progressive reduction of the offset is determined by the computer 2 as a function of the thermal state of the engine 1. The opening section S of the air actuator is then kept constant at the second value S2, until at a predetermined time tii from which the transition from the open loop control of the injection parameters and the management of the air flow begins, to a closed-loop management of these parameters carried out from a moment predetermined tiii. Thus, between times tii and tiii, the computer 2 progressively reduces the opening section of the air actuator to a third value S3 relating to an opening of the air actuator in steady-state idle speed. At time tiii, the parameters are then regulated in a closed loop by the computer 2 in order to converge towards the stabilized engine idling speed.

The stabilized engine idling speed is, for example, determined by the computer 2 during startup as a function of the thermal engine 1, and the stopping time of the vehicle 100. Thus, according to various modes of realization, the computer 2 calculates an idle N3 of idle speed, able to allow the establishment of the idle speed of the engine 1, by estimating the mass of oxygen present in the catalyst connected to the exhaust manifold at the output of the engine 1. Such an estimation by the computer 2 notably takes into account the calculation of the fuel injection duration during the start-up or restart phase. For example, at each start, the computer 2 makes an estimate of the mass of oxygen, as soon as the probes placed upstream and downstream of the catalyst have operating conditions in accordance with preconfigured thresholds (for example: voltages, temperatures ). As the oxygen mass is initially set to a default value, this value is then updated according to whether the engine is running or stopped. In the case of a rotating engine 1, the mass of oxygen stored in the catalyst is calculated from the integral of the cylinder air flow converted by the computer 2 in mass of oxygen. This flow rate is then weighted by a multiplicative factor, calculated according to the state of the probes. Advantageously, this makes it possible to identify the different transitions of rich / poor or poor / rich mixtures at the level of the catalyst, to deduce the evolution of the oxygen mass. In stop phase, the last Oxygen mass value in the catalyst is stored in memory. Thus, in the case of a stationary engine, the mass of oxygen stored in the catalyst is calculated from the last updated value in phase of rotating motor 1, weighted by a configurable offset value. The duration of fuel injection during the start-up or automatic restart phase ("Stop and Start" function) is then adjusted by the computer 2, via a factor calculated as a function of the estimated mass of oxygen in the catalyst, the N speed of the engine 1, its thermal state (for example: coolant temperature, lubricating oil, intake air), atmospheric pressure and the time spent at a standstill.

It is also observed, in the diagram a) of Figure 2, at time tiii a value (arrow 27) residual opening of the air actuator relative to the third value S3. The amplitude of this arrow 27 is here given by way of purely illustrative example. This residual value tends generally to zero, and is calculated so as to anticipate the difference in dynamic behavior between the injection parameters and the parameters of management of the air circulation in the engine 1.

Referring now to the diagram b) of Figure 2, in a first embodiment shown in solid line, at time tO, when receiving a start command, the computer 2 calculates the value S1 'referential, and then imposes on the air actuator a first opening value S1, reduced compared to the value S1' referential. Advantageously, this first value S1 reduced opening is determined, in particular, depending on the depression of the accelerator pedal, the thermal state of the engine 1 (for example: coolant temperature), and the sampling torque of different consumers (for example: alternator, injection pump, air conditioning compressor). Thus, in this diagram, the first value S1 of reduced opening, can be seen as a value (arrow 28) offset offset from the value (dashed arrow fine line) of the opening offset of the air actuator calculated for the reference value S1 '.

By way of example, the reference angle, the opening angle of the air actuator, is reduced compared with the reference value S1 by a value between one and four degrees. The aerodynamics of the air are therefore temporarily degraded in the intake distributor and in the various cylinders. Advantageously, this accelerates the depression of the intake manifold. The first value S1 of reduced opening is then kept constant during preferentially the same period T determined for the state of the art of the diagram a). Alternatively, this period T can be reduced.

In one embodiment, when the heat engine is in the automatic stop phase by the "Stop and Start" function, a first specific change in the opening angle of the air actuator is carried out. during the next restart of the engine 1, according to the evolution of the engine speed. When the heat engine is in the stop phase by the ignition key, a second specific change in the opening angle of the air actuator is performed, at the next start of the engine 1, depending on the evolution of the engine speed. Thus, in this embodiment, these changes in the opening angle of the air actuator are different depending on the situation: restart after an automatic stop phase and start or restart by the ignition key.

In another embodiment, for automobile vehicles of the "flex-fuel" type, a negative offset is also added during the start-up phase, then progressively reduced to 0 when the engine runs autonomously (after obtaining a first combustion), in order to avoid any risk of stalling the engine 1.

In another embodiment, illustrated in thick dashed lines on the same diagram, the computer 2 calculates an instant tiv, occurring during the predetermined period T, this instant corresponding to a predetermined number of High Dead Point PMH (or a predetermined number of engine times), for which a first combustion has not yet been performed with the first reduced opening value S1. For example, the computer 2 counts the number of High Engine Point for each cylinder of the engine 1 and compares this number with a predefined number (configurable). In order to guarantee this first combustion during the period T, the computer 2 then applies, from the instant tiv, an offset value (arrow 29), in order to bring the opening value of the air actuator the first opening value S1 reduced to the referential value S1. At the instant ti, when the motor 1 turns autonomously, the computer 2 then decreases progressively (dashed slope 30) the opening of the air actuator from the value S1 'referential to the first value S1 of opening reduced, and if it is reached before the end of the predetermined period T, maintains it until the end of this period T.

The various embodiments of the diagram b) then follow the same strategy driven by the computer 2 (common curve solid line from the end of the predetermined period T). At the end of the predetermined period T, the computer 2 progressively reduces (arrow 31) the opening section of the air actuator, from the first value S1, until reaching the second value S2. This progressive reduction is determined by the computer 2 as a function of the thermal state of the motor 1. The opening section S of the air actuator is then kept constant at the second value S2, until a predetermined time tii . From this moment tii 'then begins the transition of the open loop control of the operating parameters of the engine 1 (injection parameters and management of the air flow) to a closed-loop control of these parameters, effective from a predetermined time tiii '. For this time tiii ', the opening section S is then at the third value S3 relating to an opening of the air actuator in stabilized idle mode. Thus, between times tii 'and tiii', the computer 2 progressively reduces (as a function of the temperature of the engine 1) the opening value of the air actuator from the second value S2 to the third value S3 relating to when the air actuator is opened in steady-state idling mode. At time tiii ', the operating parameters of the engine 1 are then regulated in a closed loop by the computer 2: these parameters then converge to values ensuring the stabilized engine idling speed. Moreover, for illustrative purposes, there is still here, by way of example, a value (arrow 27) of residual opening of the air actuator with respect to the third value S3 at time tiii '.

The embodiments described in the diagram b) have several advantages over the state of the art. First, the first value S1 being reduced compared to the value S1 'referential. This accelerates the depression of the intake manifold. This makes it possible to advance the open-loop control transition time of the operating parameters of the engine 1 (for example: parameters for injection and management of the air flow) towards a closed-loop regulation, and thus also obtain an early closed loopback loop. We thus see on the diagram b) that the moment tii 'is advanced with respect to the instant tii, so for the moment tiii 'with respect to the instant tiii. It is therefore faster to enter the engine idle speed control phase, compared to the state of the art, which thus reduces the total startup time. In addition, the acceleration of the intake manifold depression contributes to reducing the fuel consumption associated with starting or restarting. Next, the embodiment shown in dashed lines (increasing the offset to the reference value S1) is not limited to detecting and overcoming a simple late combustion beyond a predetermined number of High Motor Point. This number is indeed parameterizable and takes into account parameters such as the type of vehicle start-up 100 (eg automatic start via the "Stop and Start" function, key start, key restart), its altitude (for example: atmospheric pressure, pressure in the intake distributor), or the thermal state of the engine 1. Thus, if a start is not possible with the first value S1, the computer 2 is able to anticipate the fact that start will not occur either at a given number of High Motor Point, and preventfully raise this value to the value S1 'referential, to ensure a first combustion in a cylinder of the engine 1. The computer 2 does not wait so necessarily the occurrence of this determined number of High Dead Point (or engine time) in the cylinders of the engine 1. For example, depending on the external conditions (pressures, temperatures), the calculator 2 little t anticipate the fact that at time ti, that is to say at the end of a predefined number of Top Dead Center (TDC), the application of the first value S1 will not make it possible to reach a first combustion. In this case, it can apply from the time of start T0 the value S1 'referential, it then decreases gradually (depending on the thermal motor 1) to the first value S1 reduced as soon as the engine 1 rotates so autonomous. Therefore, thanks to this preventive action, it is guaranteed to start the engine 1 under all pressure, altitude and temperature conditions, while ensuring a shorter start-up time compared to the state of the art. According to another strategy, the number of High Dead Point (TDC) being configurable, one can also voluntarily choose to delay the moment of first combustion of one or two High Motor Point. Although the start of the engine 1 thermal is then delayed, such a delay remains imperceptible to the driver and allows the establishment of better starting conditions: optimized engine speed, air pressure in the intake manifold, pressure and temperature in the combustion chamber. Advantageously, this contributes to improving the vibratory conditions (shaking of the engine 1) during successive starts or restarts, these conditions being perceptible by the driver. The comfort of the latter is therefore improved.

In parallel with the control of the opening section S of the air actuator, the computer 2 controls various operating parameters of the engine 1, such as the value of the ignition advance and the control parameters. injection (fuel mass injected, injection time). As will now be seen in FIG. 3, these parameters are notably regulated by the computer 2 as a function of the air pressure in the intake distributor (or in the combustion chambers), as well as the speed of the engine 1 .

In FIG. 3, there are seven diagrams showing one for the same abscissa scale, temporal evolutions of different operating parameters of the engine 1:

diagram a) illustrates in the ordinate the speed N of the motor 1 as a function of the time t on the abscissa, during a start-up (or restart) phase of the motor 1;

b) illustrates on the ordinate the binary state E of the electrical machine as a function of the time t on the abscissa, during a start-up (or restart) phase of the motor 1;

the diagram c) shows on the ordinate the pressure P in the inlet distributor (or in the combustion chambers) as a function of the time t on the abscissa, during a start-up (or restart) phase of the engine 1;

the diagram d) illustrates on the ordinate the section S of opening, also called passage section, of the air actuator (ex: butterfly) as a function of the time t on the abscissa during a starting phase (or restarting ) of the engine 1;

the diagram e) shows on the ordinate the value of the ignition advance AA as a function of the time t on the abscissa, during a start-up (or restart) phase of the motor 1; the diagram f) shows on the ordinate the fuel injection duration D as a function of the time t on the abscissa, during a start-up (or restart) phase of the engine 1;

the diagram g) shows on the ordinate the mass M of fuel injected as a function of time t on the abscissa, during a start-up (or restart) phase of the engine 1.

On the diagrams of this figure 3, the embodiments are illustrated in solid thick lines, or dashed thick lines. The state of the art is illustrated in mixed fine lines, in order to observe the advantages of the embodiments with respect to it.

At time t0, the computer 2 receives a start command (or restart), and then controls the drive of the motor 1 by the electric machine. The start command is, for example, performed following a driver action taken into account by the computer 2: via the ignition key, by pressing a start button, a release of the brake pedal, a depression of the clutch pedal, a passage of the first gear, or a depression of the accelerator pedal. The engine speed N is then zero, the electric machine is turned on but does not work yet (binary state E at "0"). The pressure P in the intake manifold is equal to a value of atmospheric pressure P0 outside the vehicle 100, the opening section S of the air actuator is at a value S0 of rest taken when the engine 1 is at the stop (here, in the open position as positive value) and the ignition advance AA is zero. At this time, the fuel injection has not yet started, the values of injection duration D as well as mass M of fuel injected are therefore zero.

At time t1, the electric machine is started, in starter mode, to drive the engine 1: its binary state E therefore passes to the value "1". Immediately following this instant t1, the electrical machine rotates the engine 1 thermal, which sees its N speed increase. The setting in motion of the internal organs of the engine 1 (rotation of the crankshaft, distribution, translation of the pistons and the valves) then causes a depression of the air in the intake manifold: the pressure P of the air in the It begins to decrease. The air actuator adopts a position such that its opening section is at the first value S1, lower than the reference value S1 beforehand determined by the computer 2. The other operating parameters of the engine 1 remain, for their part, unchanged.

At time t2, the motor is still driven via the electric machine (starter mode), the N speed of the engine reaches then upward (that is to say from below) a first threshold N1 of known regime (preconfigured) of the computer 2. By way of example, the computer 2 determines the achievement of the first threshold N1 by comparison with the current value of the speed N of the engine 1. At the same time, the pressure P in the splitter Admission continues to decline. This pressure value P is, in addition, compared by the computer 2 with a first preset pressure threshold P1, known to it. In the example illustrated in the diagram c), this first pressure threshold P1 is here not yet reached downwards (that is to say from above). However, in another example, this first pressure threshold P1 can be reached before reaching the first threshold N1. Here, at time t2, the electric machine remains in operating state (binary state E at "1") in starter mode, and the speed N of the motor 1 therefore continues to increase. The other operating parameters of the engine 1 (position of the air actuator, zero injection) are controlled by the computer 2 so as to remain unchanged. The computer 2 ensures, in fact, to keep these parameters constant, as long as it does not detect that the thresholds N1 diet and P1 pressure are both reached.

At time t3, the electric machine drives at its maximum rotational speed the engine 1. The engine 1 thus reaches a second speed threshold N2, referring to the maximum speed of the electric machine according to the gear ratio reduction. rotation between the electric machine and the motor 1. The motor 1, under the drive of the electric machine, and in the absence of first combustion, therefore remains driven constantly to this second threshold N2. At this time, the pressure P in the intake manifold continues to decrease, but does not yet reach the first pressure threshold P1. Once again, the other operating parameters of the engine 1 (position of the air actuator, zero injection) are controlled by the computer 2 so as to remain unchanged.

At time t4, the pressure P in the intake manifold continues to decrease and reaches down the pressure threshold P1. The achievement of the first engine speed threshold N1 has already occurred (here at time t2), the electric machine is kept in operation in starter mode and the computer 2 then controls the injection of fuel: by direct or indirect injection via the intake manifolds according to the structure of the engine 1. More specifically, the computer 2 controls:

injecting a mass M1 of fuel into the engine 1 during a duration D1;

the ignition advance AA from its zero initial value to a maximum value AA1.

The computer 2 also maintains the passage section S (that is to say the opening) the air actuator at the first value S1. In one embodiment, if a first combustion is still not detected after a predetermined number of High Motor Point, the computer 2 controls the opening of the air actuator to the reference value S1, which it then progressively reduces towards the first value S1 as soon as the first combustion is completed (here at time t5). This embodiment is here illustrated in thick dashed lines on the diagram d) and was previously explained during the description of FIG. 2. It should be noted, moreover, that the instants are given here by way of purely illustrative example. : the thresholds N1 of regime and P1 of pressure in the intake distributor can indeed occur before or after one with respect to the other, or even at the same time and in this case the instants t2, t3, t4 are simultaneous .

At time t5 occurs a first combustion in a cylinder of the engine 1. The electric machine is then deactivated (binary state E at "0") by the computer 2 of its starter mode, and stops driving the engine 1 thermal, which then turns autonomously. If this electric machine can also operate in alternator mode, it is then controlled by the computer 2 in this mode to electrically power the various electrical consumers of the vehicle 100. Otherwise, it is completely disabled until the receipt of the next start or restart command. Moreover, between moments t4 and t5:

the pressure P in the intake manifold continues to decrease under the effect of the rotation of the engine 1;

the ignition advance AA gradually reaches the value AA1 controlled at time t4, then is kept constant during this time interval by the computer 2; the duration D of injection is kept constant at a first value D1, the time that the ignition advance AA reaches the maximum value AA1: that is to say when the value of the ignition advance AA still transits between its initial null value and its maximum AA1 value. The injection time D is subsequently progressively decreased from the first value D1 to a second value D2, corresponding to the injection duration applied for the idling speed of the engine 1. This decrease in the injection duration D starts as soon as that the value of the ignition advance AA reaches its maximum value AA1 and takes place as the pressure P decreases within the intake distributor;

the mass M of fuel is injected at a constant value M1, from the beginning of the injection until the occurrence of the first combustion in a cylinder of the engine 1, carried out at time t5.

At time t6, the speed N of the engine 1 passes upward the set point N3 of idle speed of the engine. The time of exceeding this set point N3 corresponds to the beginning of a phase of exceeding the engine idling speed, commonly known as the "over shoot" phase. In parallel, the pressure P in the intake manifold continues to decrease, as well as the duration D of fuel injection, in connection with the evolution of the vacuum in the intake manifold. Also between t5 and t6

the section S opening value of the air actuator is progressively controlled by the computer 2 to a second value S2 of opening section less than the first value S1 of opening section;

the pressure P in the intake manifold and the fuel injection time D continue to decrease;

the injected fuel mass M is progressively increased, as a consequence of the evolution of the preceding parameters, until a maximum value M2 is reached. The mass M of fuel injected is subsequently gradually decreased from the maximum value M2 to a lower value M3, this lower value M3 corresponding to the mass M of fuel injected during the idling speed of the engine 1. This mass decrease M injected fuel is controlled by the computer 2, as soon as the maximum value M2 is reached. At time t7, the pressure P in the intake distributor reaches a second threshold P2 of pressure. Advantageously, this instant corresponds to the beginning of the transition of the operating parameters of the motor 1, from an open-loop control to a closed loop progressive control (see FIG. 2 previously described). At this moment, the duration D of injection continues to decrease and the computer 2 orders progressively

the opening section S of the air actuator to the third opening section S3 value lower than the second opening section S2 value;

the value of the ignition advance AA from its maximum value AA1 to a second value AA2 lower than the maximum value AA1.

The control by the computer 2 of the operating parameters of the engine 1, in particular the reduction of the opening section S of the air actuator, the injection duration, the ignition timing, coupled with the gradual and continuous decrease of the pressure P within the intake distributor, then causes the N regime of the thermal engine 1 to continue to increase up to a maximum value N5, commonly known as the "over shoot. This maximum value N5 ("over shoot" regime) is here reached at time t8. Moreover, between instants t7 and t8, via the application of the commands coming from the calculator 2

the injection duration D reaches the second value D2, corresponding to the injection time applied for the idling speed of the engine 1, and is kept constant;

the opening section S of the air actuator reaches the third value S3, corresponding to the opening of the air actuator applied during the engine idling speed, and is kept constant;

the value of the ignition advance AA reaches the second value AA2; the mass M of fuel injected converges to the value M3, which is the mass of fuel consumed during the idling speed of the engine 1.

At time t9, the N speed of the heat engine passes down a set point N4. According to various embodiments, the set point N4 corresponds to the value of the idle speed reference N3 added to a predefined number of engine speeds (for example: 50 rpm) or multiplied by a predefined parameterizable factor (for example: 1.1). Advantageously, the achievement of this instruction N4 downwards corresponds to the end of the phase of "over shoot" of the engine 1. From this moment, then begins the control phase of the engine idling speed and the ignition advance AA is gradually controlled to a final value AA3 of setpoint. The computer 2 can, for example, detect the beginning of the regulation phase of the engine idling speed at the instant t9, by comparison between the engine speed N and the setpoint value N4 which is previously parameterized or estimated by the calculator 2.

Finally, at time t10, the engine speed N is stabilized at the set point N3, corresponding to the constant value of engine idle speed 1. The pressure P in the intake manifold has reached a stabilized value P3. , the advance ignition has converged to the final value AA3 setpoint. All the other parameters are kept constant except for the mass M of injected fuel, which gradually decreases, as the heat transfer towards the walls of the combustion chamber decreases under the effect of the temperature rise of the walls, of the coolant and the engine lubricating oil 1. The starting phase of the thermal engine 1 is then completed.

Advantageously, thanks to the embodiments illustrated in this figure and vis-à-vis the state of the art (in phantom), it is found that the pressure P in the intake manifold converges more rapidly to the minimum pressure value P3 due to the S1 value of opening section S then taken by the air actuator, lower than the reference value S1 '. Indeed, an opening section S of the larger air actuator, implies a lower increase in ignition advance AA, and therefore a later loopback of the operating parameters of the engine 1. In contrast, in the illustrated embodiments, the convergence of the ignition advance AA to a final target value AA3 is effected from above, thanks to a reduced opening of the air actuator and to a depression Faster of the intake manifold, the pressure P in the intake manifold converging more rapidly to the value P3. This makes it possible to reach the closed-loop control regime of the operating parameters of the engine 1 more quickly. As a result, the mass of fuel consumed in the proposed embodiments is reduced.

Advantageously, the previously described embodiments allow, during a start-up phase, to empty the air more rapidly. initially contained in the intake manifold and in the cylinder combustion chamber. From the moment of start of the starting operation, under the action of the electric machine, some pistons begin their descent phase in their corresponding cylinder, the air intake valves being open. The air pressure in the intake manifold therefore decreases more rapidly, and its minimum pressure value P3 (low point) is reached between at least 0.5 and 1 second faster. The quantity of fuel injected follows in parallel the same evolution. It thus becomes possible, during the start-up phase, to start reducing the quantity of fuel injected earlier, without degrading the engine speed overrun regime ("over shoot" regime). The closed-loop control of the injection and air flow management parameters is indeed anticipated, which makes it possible to lower the various engine speed thresholds, in particular the engine speed at which the transition to regulation occurs. closed-loop injection and airflow management parameters, as well as the "over shoot" regime by reducing, during the whole start-up or restart phase, the quantities of air and fuel allowed in the combustion chambers. The phase of exceeding the engine idle setpoint is thus also improved, via a decrease in the maximum amplitude of the engine rotational speed during this phase. The anticipation of the closed-loop regulation of the injection parameters and the management of the air circulation also makes it possible to optimize the control of the opening section S of the air actuator and of the advance to the ignition AA, which allows a further reduction in fuel consumption.

Furthermore, the injected fuel reduction is variable according to the thermal engine 1 at the time of its start or restart, and is a function of the priming state of the various bodies of post-treatment of the polluting emissions of the engine. engine 1, such as the three-way catalyst, the nitrogen oxide traps, combined or not with the exhaust gas recirculation loop (EGR). Thus, for a start or a restart, the computer 2 may decide to apply the previously described embodiments, only if one or more of the following conditions are met: the temperature of the engine 1 (for example: the temperature of its coolant) exceeds a preconfigured temperature set point, for example 30 to 40 ° C;

the temperature of the air in the intake manifold at the inlet of the combustion chambers exceeds a preconfigured temperature setpoint;

all the pollution control members are primed, for example by evaluating the temperature of the exhaust gas or the temperature in the catalyst.

Advantageously, for the previously described embodiments, the computer 2 differentiates the different types of startup or restart, such as automatic startups via the "Stop and Start" function or keyed starts, and takes into account the thermal of the engine 1 as well as its altitude, to control the various parameters of injection and management of the air circulation. The previously described embodiments are therefore applicable to any automobile vehicle 100 equipped with an electric machine for driving its engine 1 during a start, with or without the "Stop and Start" function.

Advantageously, the previously described embodiments make it possible to save a fuel mass of between 0.7 and 1 g when applying an ECE-EUDC driving cycle (European driving cycle), and between 0.3 and 0.6g for the application of a WLTC driving cycle (acronym for "Wor / d Harmonized Light Vehicle Test Cycle").

These embodiments also make it possible to improve the acoustic and vibratory behavior of the powertrain, thanks to the control by the computer 2 of the number of top dead spots before a first combustion in a cylinder of the engine 1.

More generally, all of the proposed embodiments contribute to the reduction of polluting emissions of a vehicle 100 automobile.

Claims

1. A method for automatically starting a spark ignition internal combustion engine (1) for a motor vehicle (100), the motor (1) being coupled to an electric machine capable of allowing its driving, the motor (1) being connected at an intake manifold and at an exhaust manifold outlet, an air actuator being arranged upstream of the intake manifold, in particular so as to regulate the flow of air therethrough, this method being characterized in that it comprises steps of:

when receiving a start command, controlling the powering up of the electric machine, in particular so as to start driving the motor (1);

when the driving of the motor (1) starts, to impose on the air actuator a first value (S1) of opening section less than a referential value (S1 '), this reference value (S1') being calculated as a function of the thermal state of the engine (1) and being particularly adapted to guarantee the success of a first combustion from the occurrence of a first combustion cycle in a cylinder of the engine (1);

comparing the speed (N) of the engine (1) with a first threshold (N1) of speed, and compare the pressure (P) in the intake manifold at a first threshold (P1) of pressure;

controlling the injection of a mass (M) of fuel into the engine (1) and controlling the ignition timing from a zero initial value to a maximum value (AA1) when the first speed threshold ( N1) is crossed upwards by the engine speed (N) and that the first pressure threshold (P1) is crossed down by the pressure (P) in the intake distributor;

- To cut the electric machine following the occurrence of a first combustion in a cylinder of the engine (1);

subsequently regulating the operating parameters of the engine (1) to converge towards a setpoint (N3) of idle speed, in particular able to allow the establishment of the engine idling speed (1).

The method of claim 1, further comprising steps of: counting the number of top engine points for each cylinder of the engine (1) and comparing that number with a predefined number;

when the number of motor peaks reached reaches the preset number and in the absence of a first combustion, to impose on the air actuator the value (S1 ') referential for opening section, so as to realize a first combustion in a cylinder of the engine (1), then to control a gradual decrease of this value (S1 ') of opening section reference to the first value (S1) of opening section.

3. Method according to claim 1 or 2, wherein the mass (M) of fuel is injected during a duration (D), this duration (D) being controlled so as to:

being held constant at a first value (D1) when the value of the ignition advance is controlled between its initial null value and its maximum value (AA1);

being progressively decreased from the first value (D1) to a second value (D2) corresponding to the injection duration applied for the engine idle speed (1), as soon as the value of the ignition advance has reached its maximum value (AA1).

4. Method according to any one of claims 1 to 3, wherein the mass (M) of fuel is injected at a value (M1) constant from the start of its injection to the occurrence of a first combustion in a cylinder of motor (1).

5. Method according to any one of claims 1 to 4, wherein, between a moment of occurrence of a first combustion in a cylinder of the engine (1) and a moment of crossing up the set point (N3). reduced speed by engine speed (N) (1)

the opening section value of the air actuator is progressively controlled to a second opening section value (S2) smaller than the first opening section value (S1); the mass (M) of injected fuel is progressively increased until reaching a maximum value (M2).

6. The method of claim 5, wherein upon reaching the maximum value (M2) mass (M) of fuel, the mass (M) of fuel is controlled so as to gradually converge to a value (M3). lower, this lower value (M3) corresponding to the mass (M) of fuel injected during the idling speed of the engine (1).

7. The method of claim 5 or 6, wherein when a second pressure threshold (P2), lower than the first pressure threshold (P1) is crossed down by the pressure (P) in the intake manifold, the opening section value of the air actuator is progressively controlled to a third opening section value (S3) smaller than the second opening section value (S2);

the value of the ignition advance is progressively controlled from its maximum value (AA1) to a second value (AA2) lower than the maximum value (AA1).

The process of claim 7 comprising

detecting a phase of regulation of the engine idling speed (1) by comparing the speed (N) of the engine (1) with a setpoint value (N4) crossed downwards;

the progressive control of the ignition advance to a final value (AA3), lower than the second value (AA2), as soon as the occurrence of the regulation phase of the engine idling speed is detected (1) -

9. Computer (2) equipping a vehicle (100) automobile, configured to apply a method of automatic start of an engine (1) according to any one of claims 1 to 8.