CN109072797B

CN109072797B - Method for determining an energy state of an electrical energy supply system

Info

Publication number: CN109072797B
Application number: CN201780024159.9A
Authority: CN
Inventors: 亚尼克·博特肖恩; 文森特·鲁多
Original assignee: PSA Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2016-04-19
Filing date: 2017-03-15
Publication date: 2021-12-17
Anticipated expiration: 2037-03-15
Also published as: WO2017182722A1; FR3050160B1; FR3050160A1; EP3445962A1; CN109072797A

Abstract

Method for determining an energy state of an electric energy supply system, which is connected to an internal combustion engine (4), to an electric consumer (3) and comprises an electric machine (2) and an electric energy storage (1), wherein a current charge level of the storage (1) is determined, characterized in that the method further comprises the steps of: -determining the current electrical energy production capacity of the electrical machine (2), -determining that the electrical energy supply system is in a current energy state, called nominal current energy state, and that the current electrical energy production capacity of the electrical machine (2) is below a determined threshold value for which the electrical machine (2) can only ensure supply of electrical energy, if the current charge level of the storage (1) is higher than a determined charge level for which it is determined that the storage (1) has sufficient reserve.

Description

Method for determining an energy state of an electrical energy supply system

Technical Field

The invention relates to the field of automobiles, in particular to the rotational speed management and the electric energy production management of a vehicle internal combustion engine.

The engine speed of a vehicle affects its emissions and its fuel consumption, but also its ability to produce the electrical energy necessary for the operation of various electrical consumers.

Background

Intelligently reducing and manipulating the engine speed of a vehicle enables reducing its polluting emissions, as well as its fuel consumption, which represents a major challenge in the automotive industry.

However, reducing the engine speed in order to reduce emissions and fuel consumption also has the consequence of reducing the amount of maximum electrical energy that can be produced by the vehicle, which can be problematic in situations where electrical consumers in activity on the vehicle have a high demand.

From document EP2138711 a system for automatically stopping and restarting an internal combustion engine of a vehicle is known, which takes into account the state of charge of the battery to decide to stop or restart the internal combustion engine of the vehicle. However, considering only the state of charge of the battery is not sufficient to know whether the vehicle is in a state of supplying electric energy sufficient to meet the needs of the electric consumers in various activities.

Disclosure of Invention

The object of the invention is therefore to predict at every moment whether the vehicle is in a state of supplying electric energy sufficient to meet the requirements of the electric consumers in various activities, in particular in case the engine speed of the vehicle should be reduced.

In order to achieve this object, according to the invention a method is provided for determining an energy state of an electrical energy supply system connected to an internal combustion engine and to an electrical consumer, the system comprising:

an electric machine capable of extracting mechanical energy of the internal combustion engine to produce electric energy,

-an electric energy storage means,

the method comprises the steps of determining a current charge level of the reservoir, and:

-determining a current power production capacity of the electrical machine, which capacity represents a current fraction of the electrical power production of the electrical machine relative to its maximum capacity,

-determining that the electrical energy supply system is in a current energy state, referred to as nominal current energy state, which ensures that the electrical energy is supplied to the active electrical power consuming devices in a nominal manner, if the current charge level of the accumulator is higher than a determined charge level for which it is determined that the accumulator has a reserve sufficient to mitigate the load increase of the electrical power consuming devices and determining whether the current electrical energy production capacity of the electrical machine is below a determined threshold for which the electrical machine can only ensure that the electrical energy is supplied to the active electrical power consuming devices in a nominal manner.

Various additional features may be provided, either alone or in combination:

in one variant, the method further comprises the steps of:

-determining a target engine speed,

-determining a maximum electrical energy that the electrical machine can produce at the target engine speed,

-determining that the system is in a predicted operating state, called nominal predicted operating state, which guarantees a nominal supply of electrical energy to the active electrical consumers for the target engine speed, if the electrical energy consumed by the active electrical consumers is below the determined maximum electrical energy,

-determining that the system is in a power starvation condition, referred to as a critical power starvation condition, if the system is not in a nominal current operating condition and/or is not in a nominal predicted operating condition.

The invention also relates to a method of controlling a vehicle comprising an electric energy supply system connected to an internal combustion engine and to an electric power consuming device, said method comprising the aforementioned method and wherein the internal combustion engine is allowed to be operated at a determined target engine speed if it is determined that the system is not in a power deficit condition, referred to as a critical power deficit condition.

In one variation, if it is continuously determined during a predetermined validation time window that the system is not in a power starvation condition, referred to as a critical power starvation condition, then the internal combustion engine is allowed to operate at the determined target engine speed.

Advantageously, the duration of the confirmation time window is between 1 and 10 seconds.

In a variation in which the vehicle may be moved in a free-wheel mode, the target engine speed is an idle engine speed associated with movement of the vehicle in the free-wheel mode.

In another variation during which the vehicle is in free-wheel mode,

-detecting the current power production capacity of the electrical machine,

-increasing the idle engine speed associated with the movement of the vehicle in the free-wheel mode by the determined value if the maximum electrical energy production capacity of the electrical machine at the idle engine speed is reached.

Advantageously, the increase in idle engine speed associated with the movement of the vehicle in free-wheel mode is between 100 and 150 revolutions per minute.

The invention also relates to an electronic computer, characterized in that it comprises acquisition means, processing means by means of software instructions stored in a memory and control means necessary to implement the method of the invention.

The invention also relates to a vehicle comprising an electric energy supply system connected to an internal combustion engine and to an electric consumer, the system comprising:

-an electric machine capable of extracting mechanical energy of the engine to produce electric energy,

-an electric energy storage means,

the vehicle also includes an electronic computer having the above-described features.

Drawings

Other features and advantages will be apparent from reading the following description of particular embodiments, which are not limiting of the invention, made with reference to the accompanying drawings, in which:

fig. 1 is a schematic representation of an electrical configuration of a vehicle equipped with an internal combustion engine, for which the invention may be implemented.

Fig. 2 is a schematic representation of the power starvation predictor of the present invention.

Fig. 3 is a schematic representation of the adaptation of the inventive electric energy starvation predictor to vehicle driving in free wheel mode.

Detailed Description

Fig. 1 shows an electrical configuration of a vehicle, comprising an electrical energy storage 1, such as for example a battery, for example an electrochemical cell; an electric machine, such as an alternator 2; an on-board network 3 of vehicles, which aggregates the devices of the vehicles as electrical energy consumption devices, which may each be active or inactive, as required. The electrical energy storage 1 is electrically connected to the electrical machine and the vehicle electrical system and has a ground M. The on-board network 3 is electrically connected to the electric machine 2 and to the electrical ground M.

The electric machine 2 is mechanically connected to the combustion engine 4 so that it can pick up mechanical energy of the combustion engine 4 to produce electric energy. The assembly of electric machine 2 and electric energy storage 1 forms an electric energy supply system of an on-board network 4 of the vehicle. The electrical energy supply system thus makes it possible to supply electrical consumers on the basis of electrical energy stored beforehand in the electrical energy storage 1 or by converting mechanical energy produced by the internal combustion engine 4 into electrical energy by means of the electric machine 2.

The invention can be mainly broken down into three modules depicted in fig. 2:

the first module 20 has the function of calculating the current energy state, that is to say the energy state at the moment of operation of the vehicle.

The electric energy supply system is considered to be in a "nominal" state when the following two conditions are fulfilled:

the electrical energy stored in the storage 1 is above a predefined threshold. For example, the predetermined threshold may be that the charge level of the reservoir 1 is above 80%.

The electrical energy supply system is able to ensure the supply of electrical energy to the electrical consumers in the various activities by merely converting mechanical energy into electrical energy.

In the opposite case, that is to say in the following case, the electric energy supply system is considered to be in a "degraded" state:

the stored electrical energy is below a predefined threshold or the system cannot guarantee the supply of electrical energy to the electrical consumers in the various activities by merely converting mechanical energy into electrical energy.

The first module 20 uses the following information as input:

information 20a representative of the current charge level of the vehicle electrical energy storage 1. This information may be the State Of Charge Of the storage 1, generally indicated as SOC (acronym for "State Of Charge" in english).

Information 20b representative of the current power production capacity of the electric machine 2 and its saturation. The current capacity represents the current fraction of the electrical energy production of the electrical machine 2 relative to its maximum capacity. In the case where the electrical machine 2 is an alternator, this information may be the open-circuit duty cycle (RCO) of the excitation circuit of the alternator. This information enables the current capacity of the alternator and its saturation to be determined (for example, a 70% RCO indicates that the current power production capacity of the alternator is 70% of its maximum, so 30% still needs to be reserved to reach its 100% saturation).

The first module 20 determines information 20c representing the current energy state of the electrical energy supply system and supplies this information 20c as output, for example in boolean form, to translate the state into a "nominal" or "degraded". In the case where the information 20a representative of the current charge level of the electric energy storage 1 of the vehicle is the state of charge SOC of the vehicle battery and the information 20b representative of the current electric energy production capacity of the electric machine 2 and its saturation is the open-circuit duty cycle RCO, the module 20 therefore continuously verifies:

the current state of charge of the storage 1 is higher than a predefined state of charge level SOC _ lim. The state of charge threshold SOC _ lim, for example 80%, is a threshold for which it is determined that the battery has a power reserve sufficient to mitigate an unexpected load increase of the power consuming device (e.g. a new power consuming device is turned on).

The electric machine 2 of the vehicle is able to guarantee the supply of electric energy to the various electric consumers by merely converting mechanical energy into electric energy. This is verified if the current duty cycle RCO is below a threshold RCO _ alt _ lim for which the electrical machine 2 can ensure that only nominal electrical energy is supplied to the active electrical consumers, that is to say without resorting to the energy stored in the storage 1. The threshold may be a 100% saturation threshold or, better, a safety margin is taken into account and may therefore be 80% in this case.

If these two conditions are met, the vehicle's electrical energy supply system will be considered to be in a current energy state (as already defined above) referred to as the "nominal" energy state, otherwise it will be referred to as being in a current "degraded" state.

The second module 21 has the function of calculating the energy state of the electrical energy supply system for a target engine speed, i.e. at which the engine of the vehicle is intended to be operated from the point of view of reducing CO2 emissions and/or reducing fuel consumption. The module aims to predict whether the electric energy supply system is still able to supply active electric consumers at the target engine speed merely by converting mechanical energy into electric energy supplied by the electric machine without having to resort to the energy stored in the electric power storage 1.

The purpose of this second module 21 is to determine whether the electric energy supply system of the vehicle is able to meet its various needs on electric energy in the event of a transition to a phase characterized by a reduction in the maximum potential of mechanical energy available for conversion into electric energy. This phase is represented by a reduction in the engine speed of the vehicle, which means that the maximum mechanical energy that can be extracted by the electric machine 2 (for example an alternator) is reduced.

The second module 21 calculates at each instant the current electrical energy required to power the various electrical consumers in the activity on the vehicle at that instant in time of calculation.

The second module 21 also predicts a maximum electrical energy that the vehicle's electrical energy supply system can provide for a given target engine speed that is lower than the vehicle's current engine speed.

The possibility of comparing these two electrical energy values in order to arbitrate the electrical energy supply system of the vehicle: whether it is still possible to guarantee the supply of electrical energy to the electrical consumer merely by converting the available mechanical energy into electrical energy in the event of a reduction of the engine speed of the vehicle towards the desired target engine speed.

The second module 21 uses the following information as input:

information 21a representative of the target engine speed for which it is desired to predict the maximum electrical energy that can be produced.

-information representative of the current electrical energy required to power electrical consumers in various activities on the vehicle. This information may be obtained based on the output voltage information 21b of the motor 2 and the current intensity information 21c provided by the motor 2.

The second module 21 determines information 21d indicative of an energy state prediction of the electrical energy supply system for a future target engine speed at which it is desired to operate the engine of the vehicle and provides this information as an output.

The predicted energy state is referred to as a "nominal" predicted energy state when the maximum electrical energy that the electrical energy supply system of the vehicle can provide at the desired target engine speed is higher than the electrical energy required to power the various electrical consumers that are active at the time of calculation.

The predicted energy state is referred to as a "degraded" predicted energy state when the maximum electrical energy that the vehicle's electrical energy supply system can provide at the desired engine speed is lower than the electrical energy required to power the various electrical consumers that are active at the time of calculation.

This information 21c may be represented, for example, in boolean form, to translate the state into "nominal" or "degraded".

In the case where information representing the present electrical energy required to power electrical consumers in various activities on the vehicle is obtained based on the output voltage information 21b of the electrical machine 2 and the amperage information 21c provided by the electrical machine 2, this second module determines:

current electrical power consumed by the electrical consumers in the respective activity, Pelec _ conso:

Pelec_conso＝|u_Prod＊i_Prod|＊facteur_correction_P_conso

wherein:

u _ Prod: the output voltage of the motor 2 is,

i _ Prod: the intensity of the current supplied by the motor 2,

factor _ correction _ P _ conso: adjustment factors to account for uncertainty of u _ Prod and i _ Prod. This factor may be a constant chosen to compensate for the maximum uncertainty, or may be determined and calibrated through mapping.

Maximum electric power that the electric machine 2 can provide to the electric energy supply system at the target engine speed at which the engine of the vehicle is intended to be changed, Pelec _ Max _ dispo:

Pelec_Max_dispo＝|Rend_Alt_débit_Max＊Couple_Alt_débit_Max＊2π/60＊Rapport_Demul_Alt＊N_mot_cible|＊facteur_correction_P_max

wherein:

n _ mot _ cible: the target engine speed at which the vehicle is intended to be operated, in other words, the information 21a,

rend _ Alt _ d _ bit _ Max: the productivity of the machine 2 associated with the maximum current that can be supplied at a given target speed N _ mot _ cible,

couple _ Alt _ d bit _ Max: the torque drawn by the electric machine 2 associated with the maximum current that can be supplied at a given target speed N _ mot _ cible,

report _ Demul _ Alt: so that the reduction ratio of the rotational speed of the motor 2 can be calculated from the given target rotational speed N _ mot _ cible,

factor _ correction _ P _ max: an adjustment factor is calculated that takes into account the uncertainty of the above parameters. This factor may be a constant chosen to compensate for the maximum uncertainty, or may be determined and calibrated through mapping.

For this step, a running map using the electric machine 2 may be provided, in which the amperage, the torque and the yield thereof are given according to the engine speed.

The two electrical power values are then compared and the predicted energy state of the electrical energy supply system will be referred to as the "nominal" predicted energy state for the target speed under consideration if:

Pelec_conso≤Pelec_Max_dispo

in the opposite case, the predicted energy state of the electric energy supply system will be referred to as "downgrading" the predicted energy state for the target rotational speed under consideration.

In the case where it is desired to manipulate the engine speed of a vehicle, in particular to reduce the engine speed of a vehicle in order to reduce, inter alia, the consumption of the vehicle and the CO2 emissions, it is necessary to anticipate the effect of this speed reduction on the capacity of the electrical energy production system of the vehicle in order to always produce sufficient electrical energy to power the various electrical consumers in motion.

The third module 22 therefore has the function of determining whether a risk of electrical shortage of the electrical energy supply system is possible. The third module 22 uses for this purpose the

information

20c and 21d provided by the first and

second modules

20 and 21, respectively, as input.

The third module 22 determines and provides as output:

information 22a representative of the occurrence of an electrical energy deficit of the electrical energy supply system of the vehicle. This information is a map of its ability to guarantee the supply of electrical energy to electrical consumers at the present engine speed of the vehicle and at a future target engine speed at which the vehicle is expected to operate.

If the electric energy supply system of the vehicle cannot meet the needs of the active electricity consumers for the current engine speed and/or the target engine speed for which it is desired to change the vehicle to, or if the electric energy supply system is in a current operating state called "degraded" and/or in a predicted operating state called "degraded", the occurring shortage of electric energy will be called "critical".

In the opposite case, the occurring shortage of electric energy will be called "uncritical" if the electric energy supply system is in a current operating state, called "nominal", and in a predicted operating state, called "nominal", i.e. if the electric energy supply system of the vehicle is able to meet the needs of the electric consumers in motion for the current engine speed and the target engine speed for which it is desired to change the vehicle to.

This information 22a may be presented, for example, in boolean form to translate states into "critical" or "non-critical".

This information 22a, determined in real time, may then be used to make decisions regarding engine speed management in terms of decisions to reduce CO2 emissions and reduce vehicle fuel consumption.

For example, during the phase of free-wheeling, the clutch of the vehicle is open, which enables the internal combustion engine to be disconnected from the wheels, and it is desirable to maintain the internal combustion engine at an idling speed, for example around 800 to 900tr/min for a motor vehicle. This has the effect of enabling better use of the kinetic energy of the vehicle and reducing its fuel consumption. In fact, during this phase, the vehicle consumes only little fuel, since the engine is at idle and so far it is only advancing with accumulated kinetic energy. This is favored by decoupling the engine/wheels, which reduces engine drag against the motion of the vehicle.

However, running at such a speed means that the capacity of the electric machine 2 to produce electric energy is reduced, which may cause problems if an electric consumer consuming more energy than the vehicle at this engine speed can provide is active, in particular an electric consumer connected to the vehicle's protective equipment. Furthermore, a decrease in electrical energy production may result in a decrease in battery charge level, which will affect the availability of functions such as engine shut down and auto restart.

To this end, fig. 3 presents a complement to the module shown in fig. 2. The supplement presents two additional modules.

The fourth module 30 has the function of determining to allow the vehicle to run in free-wheel mode, which ensures that the active power consumers will always be properly powered at constant power consumption before and during the phase of running in free-wheel mode.

The fourth module 30 uses the following information as input:

information 22a representative of the occurrence of an electrical energy deficit of the electrical energy supply system of the vehicle.

The fourth module 30 determines and provides as output:

information 30a, for example in boolean form, for translation into whether the vehicle is allowed to run in free-wheel mode.

The allowance is thus based on information 22a representing the occurrence of an electrical energy shortage of the electrical energy supply system of the vehicle, which information 22a is calculated for the engine speed associated with free-wheeling. The target speed generally corresponds to an engine idle speed.

Thus, for a target engine speed associated with running the vehicle in free-wheeling mode, information 22a is calculated indicating the occurrence of an electrical energy shortage of the electrical energy supply system of the vehicle, and one or the other of the already explained states can be taken: "critical" or "non-critical".

The third module 30 then verifies whether the message 22a is continuously in the "non-critical" state during the validation time window. The duration of the confirmation window is advantageously between 1 and 10 seconds. The minimum duration is selected in order to filter the transient "non-critical" state in order to ensure that the vehicle is able to supply sufficient electrical energy to the active electrical consumers in the current state, that is to say at the engine speed at which the instant in time is calculated. The maximum duration of the acknowledgement time window is chosen so that it is higher than the duration of the corresponding transient phase of the parameters used by the method.

If the message 22a remains in the "non-critical" state for the entire validation time window duration, the third module 30 provides the vehicle, via the message 30a, with permission to enter a phase of free-wheeling travel at the associated target engine speed. This permission remains valid as long as the information 22a remains in the "non-critical" state.

If the message 22a goes to the "critical" state before the end of the duration of the confirmation time window, the third module 30 does not provide the vehicle with permission to enter the phase of free-wheel travel via the message 30 a.

In the event that permission is obtained, the engine is separated from the wheels by the gearbox, thereby reducing the frictional resistance on the wheels connected to the engine. This reduces the fuel consumption and pollutant emissions of the vehicle.

When the vehicle is in the process of running in the free wheel manner, the engine speed is also reduced to the target engine speed (idling speed) associated with this stage. The end of this phase is only declared by the driver's intention, for example, an acceleration intention or a deceleration intention.

This means that once the vehicle is given permission to travel in free-wheel mode and is actually in a state of travel in free-wheel mode, it is not possible to directly end the phase.

A problem that may then arise is that of changing the power consumption of the power consumer after allowing free-wheeling. For example, after allowing free-wheeling, the driver may activate a new power consumer, possibly affecting the overall energy balance (constant production/higher power demand).

The fifth module 31 has the function of determining whether it is necessary to provide an increase in the engine speed associated with the free-wheel mode of travel when the vehicle is in this mode of travel.

The fifth module 31 uses the following information as input:

information 20b representative of the current power production capacity of the electric machine 2 and its saturation. In the case where the electrical machine 2 is an alternator, this information may be the open-circuit duty cycle (RCO) of the excitation circuit of the alternator.

The fifth module 31 determines and provides as output:

information 31a representative of the need or lack thereof to increase the engine speed associated with the mode of free-wheeling travel of the vehicle.

In the case where the information 20b representing the current electrical energy production capacity of the electric machine 2 and its saturation is the open-circuit duty cycle RCO, the module 31 detects whether the electric machine 2 becomes saturated with respect to the engine speed (idle speed) at which the internal combustion engine 4 is operated during free-wheeling, i.e. RCO equals 100%.

In case saturation of the electric machine 2 is detected during the free-wheeling phase, this means that the vehicle is no longer able to supply sufficient electrical energy to the electrical consumers in various activities due to an increase in the electrical energy demand of the electrical consumers (e.g. a new electrical consumer is activated). The fifth module 31 sends via the information 31a an increase of the idle speed of the internal combustion engine 4 in order to increase the electric energy production of the electric machine 2 while maintaining the phase of free-wheel travel. This increase in the idle speed of the internal combustion engine 4 associated with the movement of the vehicle in the free-wheel mode is preferably between 100 and 150tr/min, which limits the perception by the driver.

All the modules of the invention can be housed in an electronic calculator comprising acquisition means, processing means by software instructions stored in a memory and control means necessary to implement the invention.

The invention enables to predict from the engine speed whether the production of electrical energy of the vehicle will enable to guarantee the supply of electrical energy to all active electrical consumers when the vehicle will reduce its engine speed. It depends on the one hand on the current energy state of the vehicle, which depends on its ability to provide the electrical energy required by the electrical consumers at each instant, and on the other hand on a prediction of the evolution of this energy state to be achieved for a new target engine speed.

The invention makes it possible to determine in the case of a desire to reduce its engine speed, for example for reducing CO₂Emissions considerations, whether the vehicle is exposed to a condition of electrical energy scarcity.

The invention thus makes it possible to intelligently manipulate the engine speed of the vehicle from the point of view of the electrical energy supply, in order to safely reduce its consumption and its emissions.

Claims

1. A method for determining an energy status of an electric energy supply system connected to an internal combustion engine (4) and to an electric consumer (3), the system comprising:

-an electric machine (2) able to extract the mechanical energy of the internal combustion engine (4) to produce electric energy,

-an electric energy storage (1),

the method comprises the step of determining a current charge level (20a) of the reservoir (1),

characterized in that the method further comprises the steps of:

-determining a current power production capacity of the electrical machine (2), which capacity represents a current fraction of the electrical power production of the electrical machine (2) relative to its maximum capacity,

-if the current charge level (20a) of the accumulator (1) is higher than a determined charge level, determining (20) that the electric energy supply system is in a current energy state, referred to as nominal current energy state, which ensures that electric energy is supplied in a nominal manner to active electric power consuming devices, the determined charge level determining that the accumulator (1) has a reserve sufficient to mitigate load increase of the electric power consuming devices and that the current electric energy production capacity of the electric machine (2) is below a determined threshold for the electric machine (2) to ensure only that electric energy is supplied in a nominal manner to active electric power consuming devices.

2. The method according to claim 1, characterized in that the method further comprises the steps of:

-determining a target engine speed (21a),

-determining a maximum electrical energy (21b, 21c) that the electrical machine (2) is capable of producing at the target engine speed (21a),

-determining (21) that the system is in a predicted operating state, referred to as nominal predicted operating state, if the electrical energy consumed by the active electrical consumer is below the determined maximum electrical energy, said nominal predicted operating state ensuring that the electrical energy is supplied to the active electrical consumer in a nominal manner for said target engine speed,

-determining (22) that the system is in a power starvation condition, referred to as a critical power starvation condition, if the system is not in a nominal current operating condition and/or not in a nominal predicted operating condition.

3. A method of controlling a vehicle comprising an electric energy supply system connected to an internal combustion engine (4) and to an electric power consuming device (3), characterized in that the method comprises a method according to claim 2, and wherein the internal combustion engine (4) is allowed (30) to be operated at a determined target engine speed (21a) if it is determined that the system is not in a power deficit condition, referred to as a critical power deficit condition.

4. A method according to claim 3, characterized by allowing the internal combustion engine (4) to be operated at the determined target engine speed (21a) if it is continuously determined during a predetermined validation time window that the system is not in a power starvation condition, referred to as a critical power starvation condition.

5. The method of claim 4, wherein the duration of the acknowledgement time window is between 1 and 10 seconds.

6. The method according to one of claims 3 to 5, characterized in that the vehicle is movable in a free wheel mode, the target engine speed being an idle engine speed associated with the movement of the vehicle in free wheel mode.

7. The method of claim 6, wherein during the vehicle being in free-wheel mode,

-detecting a current power production capacity of the electrical machine (2),

-increasing the idle engine speed associated with the movement of the vehicle in free wheel mode by the determined value if said maximum electrical energy of said electrical machine (2) at idle engine speed is reached.

8. The method of claim 7, wherein the increase in idle engine speed associated with movement of the vehicle in free-wheel mode is between 100 and 150 revolutions per minute.

9. Electronic computer, characterized in that it comprises acquisition means, processing means by software instructions stored in a memory and control means necessary to implement the method according to one of the preceding claims.

10. A vehicle comprising an electric energy supply system connected to an internal combustion engine (4) and to an electric consumer (3), the system comprising:

-an electric machine (2) able to extract the mechanical energy of the internal combustion engine to produce electric energy,

-an electric energy storage (1),

the vehicle further comprising an electronic computer according to the preceding claim.