METHOD AND SYSTEM FOR MONITORING ELECTRIC ENERGY CONSUMERS AND FOR CONTROLLING THE ENGINE SPEED OF A MOTOR VEHICLE

Description

[0001] The present invention relates to the field of internal combustion engines, and more particularly to exhaust gas aftertreatment systems equipped with a particulate filter and arranged in the exhaust line.

[0002] Particulate filters are used to treat particles contained in the combustion gases of internal combustion engines, including soot particles in diesel engines or so-called fine particles in spark-ignition engines.

[0003] As is well known, a particulate filter operates sequentially. During normal engine operation, the particulate filter traps particles without processing them, at a rate close to 100%. Then, sequentially, for example, when the particle mass reaches a threshold value, it is necessary to regenerate or purge the particulate filter to remove the accumulated particles. This is because the accumulation of particles generates back pressure in the vehicle's exhaust, which significantly reduces engine performance. Furthermore, as the mass of particles trapped in the particulate filter increases, its filtration capacity decreases. In other words, during normal engine operation, the particulate filter retains a progressively smaller proportion of particles.

[0004] The regeneration of the particulate filter involves switching the engine's operating mode to a specific setting that burns off accumulated particles in the filter when their mass reaches a threshold value. More precisely, the combustion of these particles is achieved through a specific combustion setting that provides sufficient oxygen concentration and temperature at the particulate filter inlet to allow for efficient combustion.

[0005] However, depending on the mass of particles accumulated in the particulate filter, it is necessary to control the oxygen concentration and regulate the temperature of the exhaust gases upstream of the particulate filter so that they do not exceed thresholds beyond which the combustion reaction could run away and irreversibly damage the particulate filter.

[0006] The regeneration of a particulate filter is also known to generate increased fuel consumption. Indeed, the exhaust gas temperature required for regeneration, for example, around 650°C in a diesel engine, is obtained by reducing the engine's combustion efficiency compared to its normal operating efficiency and by adding fuel, through late injections in the engine cycles, upstream of the particulate filter.

[0007] The more the vehicle is driven under load and / or at high engine speeds, the higher the particulate filter temperature. The temperature difference required to initiate particulate filter regeneration is therefore smaller. Consequently, it is less fuel-intensive, in terms of the amount of fuel needed to regenerate the particulate filter, to perform regeneration at high speed rather than at low speed.

[0008] It is known to use a particulate filter regeneration process in which the mass threshold values ​​for triggering regeneration are different depending on the speed of the motor vehicle.

[0009] For example, it is possible to use four distinct particle mass thresholds. The lowest mass threshold triggers particulate filter regeneration at high vehicle speeds, such as on a highway. A second mass threshold, higher than the lowest, triggers particulate filter regeneration at a second vehicle speed, lower than the highest speed. A third mass threshold, higher than the second, triggers particulate filter regeneration at a third vehicle speed, lower than the second, such as when driving in the city. A fourth mass threshold, higher than the third, triggers particulate filter regeneration at a fourth vehicle speed, lower than the third.

[0010] In some cases, for example during short daily journeys, exclusively urban driving at very low speeds or journeys at high altitude, the soot loading level can be high and the autonomous active regenerations, which are triggered by a switch in the engine's combustion setting mode independently of any action by the vehicle driver, are no longer sufficient to guarantee the regeneration of the particulate filter.

[0011] It is known to apply a driving recommendation process, called "driving recommendation" in Anglo-Saxon terms, by the engine computer capable of making other changes to the vehicle's operation in order to achieve the regeneration of the particulate filter.

[0012] Such a process usually occurs during the autonomous regeneration phase just before the mass of particles exceeds the threshold value indicating that the particulate filter is clogged.

[0013] The driving recommendation mode consists of informing the vehicle driver, for example, via a warning light on the dashboard, that the mass of fine particles contained in the particulate filter is abnormally high and that a regeneration of the particulate filter is in progress.

[0014] The efficiency of regeneration is improved through two combined measures. First, the engine load, i.e., the torque, is increased by activating multiple actuators or electrical power consumers capable of drawing high torque from the engine. Such electrical power consumers might include, for example, immersion heaters and a fan assembly configured to cool the engine and draw high torque from it. The heated rear window is also an actuator capable of drawing torque from the engine.

[0015] Such concepts are disclosed for example in documents FR 2920474 A1, US 2018086332 A1, DE 102019202210 A1 or DE 102007015875 A1.

[0016] The torque delivered by the engine corresponds to the sum of the torque command from the depressing of the accelerator pedal to drive the vehicle, and the torque(s) of the various electrical energy consumers drawing torque from the engine.

[0017] The increase in engine torque leads to an increase in heat emissions from the exhaust. On the other hand, the engine idle speed is also increased.

[0018] Indeed, engine idle speed regulation is achieved by modulating the amount of fuel injected into the engine in order to regulate, in a closed loop, on an engine speed setpoint, and not on a torque setpoint.

[0019] However, depending on the electrical energy consumers drawing torque from the engine, the torque drawn from the engine is more or less significant, so that engine speed regulation involves more or less significant amounts of fuel injected and a higher or lower torque to maintain the engine speed.

[0020] However, if one of the electrical energy consumers, for example the motor-fan unit, cannot be activated, for example it is unavailable or it is faulty, the fast idle speed must not be activated under penalty of damaging the particulate filter by thermal runaway due to uncontrolled combustion of particles.

[0021] Electrical continuity diagnostics for cooling fan assemblies are known. However, detecting the unavailability or failure of the cooling fan assembly is not possible with a fault detector because no fault or electrical diagnostic information is transmitted to the engine control unit.

[0022] Furthermore, electrical continuity diagnosis is insufficient because it does not allow for the detection of potential mechanical problems.

[0023] The object of the present invention is therefore to provide a method and a system for controlling the engine speed based on monitoring the state of electrical energy consumers, and in particular the motor-fan unit which is generally the largest electrical energy consumer of the vehicle, during the driving recommendation mode, called "driving recommendation" in Anglo-Saxon terms, in order to reduce the number of cloggings of the particulate filter and guarantee the integrity of the particulate filter, by maintaining a nominal idle speed in the event of detection of a failure of said motor-fan unit.

[0024] The object of the present invention is therefore to detect the failure of any electrical energy consumer capable of drawing torque from the motor and to control the motor speed according to the detection of such a failure.

[0025] The invention relates to a method for controlling an internal combustion engine comprising a fresh air intake manifold, an exhaust manifold and a pollution control system comprising at least a first pollution control device and a particulate filter, known as a "catalytic soot filter", acronymed as "CSF" in Anglo-Saxon terms, disposed in the exhaust line downstream of an oxidation catalyst, the pollution control system further comprising a differential pressure sensor located upstream and downstream of the particulate filter and a temperature sensor disposed upstream of said particulate filter.

[0026] According to the process, the state of electrical energy consumers is monitored during an engine operating mode in driving recommendation mode, configured to detect the failure of any electrical energy consumer capable of drawing torque from the engine and to control the engine speed accordingly during an autonomous regeneration phase of the particulate filter, in order to detect the failure of any electrical energy consumer capable of drawing torque from the engine and the engine speed is controlled according to the detection of the failure of any electrical energy consumer.

[0027] Advantageously, when monitoring the status of electrical energy consumers, the mass of particles present in the particle filter is compared with a first threshold value.

[0028] The differential pressure, in association with the gas flow rate through the filter, allows us to determine the mass of particles stored in the particle filter.

[0029] The first threshold value corresponds to the highest threshold that allows active regeneration of the particulate filter to be triggered at the lowest speed threshold value by only modifying the combustion mode. This first threshold value is used to activate the engine's recommended driving mode.

[0030] Advantageously, when monitoring the status of electrical energy consumers, the engine alternator load is continuously compared with a second threshold value. When the alternator load is less than or equal to the second threshold value, a nominal idle speed command is sent to the engine control unit, and when the alternator load is greater than the second threshold value, a fast idle speed command is sent to the engine control unit.

[0031] This allows us to detect whether the torque is normal or too low, which is the case when an electrical power consumer fails. High torque results in a high alternator load; monitoring the alternator load is used to determine the torque level and, indirectly, the failure of an electrical consumer.

[0032] For example, when monitoring the status of electrical energy consumers, the status of the engine's alternator is checked.

[0033] According to a second aspect, the invention relates to an electronic control system or unit for an internal combustion engine comprising a fresh air intake manifold, an exhaust manifold and a pollution control system comprising at least a first pollution control device and a particulate filter disposed in the exhaust line downstream of an oxidation catalyst, the pollution control system further comprising a differential pressure sensor located upstream and downstream of the particulate filter and a temperature sensor disposed upstream of said particulate filter.

[0034] The electronic control unit includes a system for monitoring the status of electrical energy consumers during an engine operating mode in driving recommendation mode, configured to detect the failure of any electrical energy consumer capable of drawing torque from the engine and to control the engine speed accordingly during an autonomous regeneration phase of the particulate filter.

[0035] Said system for monitoring the status of electrical energy consumers during an engine operating mode in driving recommendation mode being configured to detect the failure of any electrical energy consumer capable of drawing torque from the engine.

[0036] The electronic control unit also includes a system for controlling the engine speed based on the detection of the failure of any electrical power consumer by the supervisory system.

[0037] Advantageously, the system for monitoring the status of electrical energy consumers includes a module for comparing the mass of particles present in the particle filter with a first threshold value.

[0038] The differential pressure, in association with the gas flow rate through the filter, allows us to determine the mass of particles stored in the particle filter.

[0039] The first threshold value corresponds to the highest threshold that allows active regeneration of the particulate filter to be triggered at the lowest speed threshold value by only modifying the combustion mode. The first threshold value, S1, is used to activate the engine's driving recommendation mode.

[0040] Advantageously, the electrical energy consumer status monitoring system includes a module for continuously comparing the engine alternator load with a second threshold value.

[0041] The comparison module is configured to detect whether the torque is normal or too low, which is the case when an electrical power consumer fails. High torque results in a high alternator load; monitoring the alternator load is used to determine the torque level and, indirectly, the failure of an electrical consumer.

[0042] When the alternator load is less than or equal to the second threshold value, the engine speed control system is configured to transmit a nominal idle speed command to the engine control unit, and when the alternator load is greater than the second threshold value, the engine speed control system is configured to transmit a fast idle speed command to the engine control unit.

[0043] For example, the electrical energy consumer status monitoring system includes a module for checking the status of the engine alternator.

[0044] According to another aspect, the invention relates to a motor vehicle comprising an electronic control unit as described above.

[0045] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which: [ Fig 1 ] represents, in a very schematic way, an example of the structure of an internal combustion engine of a motor vehicle equipped with an exhaust system having an exhaust gas aftertreatment system and a control unit according to the invention; Fig 2 ] represents a graph illustrating engine torque on the x-axis with oxygen levels on the y-axis; [ Fig 3 ] represents a graph illustrating engine torque on the x-axis with temperature on the y-axis; and [ Fig 4 ] represents the synoptic diagram of a control method according to the invention implemented by the control unit of the figure 1 .

[0046] On the figure 1 , we have represented, in a schematic way, the general structure of an internal combustion engine 10, in particular of the Diesel type, of a motor vehicle.

[0047] This architecture is given by way of example and does not limit the invention to the single configuration to which the supervision of electrical consumers and the control of the motor speed according to the invention can be applied.

[0048] In the illustrated example, the internal combustion engine 10 comprises, but is not limited to, four inline cylinders 12, a fresh air intake manifold 14, an exhaust manifold 16 and a turbocharger system 18.

[0049] The cylinders 12 are supplied with air via the intake manifold 14, or intake distributor, itself supplied by a pipe 20 equipped with an air filter 22 and the compressor 18b of the turbocharger 18 of the engine 10.

[0050] As illustrated, each cylinder 12 is supplied with fuel, of the diesel type, via a fuel injector Ic.

[0051] As is known, the turbocharger 18 essentially comprises a turbine 18a driven by the exhaust gases and a compressor 18b mounted on the same axis or shaft as the turbine 18a and ensuring compression of the air distributed by the air filter 22, in order to increase the quantity (mass flow) of air admitted into the cylinders 12 of the engine 10. The turbine 18a may be of the "variable geometry" type, that is to say that the turbine wheel is equipped with variable inclination blades in order to modulate the amount of energy taken from the exhaust gases, and thus the boost pressure.

[0052] A heat exchanger 24 is placed after the outlet of the compressor 18b equipping the supply line 14a of the intake manifold 14 with fresh air.

[0053] The internal combustion engine 10 thus includes an intake circuit Ca and an exhaust circuit Ce.

[0054] The intake circuit Ca comprises, from upstream to downstream in the direction of airflow: the air filter 22 or air box; the compressor 18b of the turbocharger 18 configured to compress air taken from the outside atmosphere and, where applicable, low-pressure recycled exhaust gases, as will be described later; the heat exchanger 24 configured to cool the intake gases corresponding to a mixture of fresh air and recycled gases, after their compression in the compressor 18b; a regulating valve 28 disposed in the supply line 14a of the intake manifold 14, downstream of the heat exchanger 24 and upstream of the intake manifold 14, said valve 28 being configured to regulate the flow of air and low-pressure recycled gases entering the cylinders 12; and the intake manifold 14.

[0055] The exhaust system includes, from upstream to downstream in the direction of flow of the burnt gases: the exhaust manifold 16; the turbine 18a of the turbocharger 18 configured to extract energy from the exhaust gases passing through it, said expansion energy being transmitted to the compressor 18b via the common shaft, for the compression of the intake gases; a combustion gas aftertreatment system 40 for the engine.

[0056] As regards the exhaust manifold 16, it recovers the exhaust gases from the combustion and expels them to the outside, via an exhaust gas duct 30 opening onto the turbine 18a of the turbocharger 18 and via an exhaust line 32 mounted downstream of said turbine 18a.

[0057] By way of non-limitation, the engine 10 includes two partial recirculation circuits 34, 36 of exhaust gases to the intake, known as "exhaust gas recirculation" or "EGR" in Anglo-Saxon terms.

[0058] The first high-pressure exhaust gas recirculation circuit 34, known as "EGR HP", originates at a point in the exhaust duct 30 upstream of the turbine 18a and returns the exhaust gases to a point in the supply duct 14a downstream of the compressor 18b and in particular downstream of the heat exchanger 24 and the regulating valve 28. The first recirculation circuit 34 includes a first "V EGR HP" valve configured to regulate the flow of the recycled high-pressure exhaust gases.

[0059] The first exhaust gas recirculation circuit 34 is configured to recover a portion of the exhaust gases and reintroduce them into the air intake manifold 14, in order to limit the amount of nitrogen oxides produced by combustion while preventing the formation of smoke in the exhaust gases. The first recirculation circuit 34 could, for example, include a heat exchanger (not shown).

[0060] The second low-pressure exhaust gas recirculation circuit 36, known as "EGR BP", originates at a point in the exhaust line 32, downstream of said turbine 18a, and in particular downstream of the gas aftertreatment system 40, and returns the exhaust gases to a point in the fresh air supply line 20, upstream of the compressor 18b of the turbocharger 18.

[0061] As illustrated, the second recirculation circuit 36 ​​comprises, in the direction of recirculated gas flow, a filter 36a, a cooler 36b, and a second "V EGR BP" valve configured to regulate the flow of recirculated exhaust gases at low pressure. The second "V EGR BP" valve is located downstream of the cooler 36b, downstream of the flow meter 26, and upstream of the compressor 18b.

[0062] By way of non-limiting example, the engine combustion gas depollution system 40 includes an oxidation catalyst 42 located in the exhaust line 32 directly downstream of the turbine 18a, and a particulate filter 44, known as a "catalytic soot filter", acronymed "CSF" in Anglo-Saxon terms, disposed in the exhaust line 32 downstream of the oxidation catalyst 42.

[0063] A proportional-type oxygen probe (not shown in the figure 1 ) is mounted upstream of the oxidation catalyst 42. As is known, it serves to regulate the richness of the air-fuel mixture.

[0064] The system 40 further includes a differential pressure sensor 46 P_diff located upstream and downstream of the particle filter 44 and a temperature sensor T1 located directly upstream of the particle filter 44.

[0065] The differential pressure, in association with the gas flow rate through the filter, allows us to determine the mass of particles stored in the particle filter 44.

[0066] The engine includes an electronic control unit 50 configured to control the various elements of the internal combustion engine and in particular the engine speed.

[0067] The electronic control unit 50 could receive other data, such as temperatures at different locations in the engine, or other pressures.

[0068] The electronic control unit 50 includes a system 60 for monitoring the status of electrical energy consumers, and in particular the motor-fan group, during an engine operating mode called driving recommendation, configured to detect the failure of any electrical energy consumers capable of drawing torque from the engine and to control the engine speed accordingly.

[0069] Thus, the number of times the particulate filter clogging can be reduced and the integrity of the particulate filter is guaranteed while maintaining a nominal idle speed in the event of a failure detected in the said motor-fan assembly.

[0070] The recommended driving mode is applied by the engine control unit in order to make other changes to the vehicle's operation with the aim of achieving particulate filter regeneration.

[0071] This type of engine operation occurs during the autonomous regeneration phase just before the mass of particles exceeds the threshold value indicating that the particulate filter is clogged.

[0072] The driving recommendation mode consists of informing the vehicle driver, for example, via a warning light on the dashboard, that the mass of fine particles contained in the particulate filter is abnormally high and that a regeneration of the particulate filter is in progress.

[0073] The driver is advised not to interrupt the particulate filter regeneration process and to avoid using certain gear ratios.

[0074] The driving recommendation mode helps to improve the efficiency of particulate filters by increasing the engine load, for example by switching on immersion heaters and the cooling fan assembly, and by increasing the engine idle speed, for example around 1050 rpm.

[0075] The system 60 for monitoring the status of electrical energy consumers includes a module 62 for comparing the mass of particles present in the particle filter 44 with a first threshold value S1.

[0076] The first threshold value, S1, corresponds to the highest threshold that allows active regeneration of the particulate filter 44 to be triggered at the lowest speed threshold value by modifying only the combustion mode. The first threshold value, S1, is used to activate the engine's recommended driving mode.

[0077] We can refer to figures 2 et 3 which represent graphs illustrating engine torque on the x-axis with oxygen levels and temperature respectively on the y-axis.

[0078] State E1 corresponds to a reference state in which electrical energy consumers are active and functional. The internal temperature of particulate filter 44 is approximately 700°C and the oxygen level is 6%. The particulate filter regeneration conditions are monitored and controlled by the engine control unit.

[0079] State E2 corresponds to a critical state in which the electrical power consumers fail and therefore no longer draw torque from the engine, and the engine operates at a fast idle speed, maintained with reduced torque. The internal temperature of the particulate filter 44 is higher than the temperature corresponding to the reference state E1, and the oxygen level is double that of the reference state E1. These thermal gradients can cause irreversible damage to the particulate filter.

[0080] State E3 corresponds to a controlled state in which electrical power consumers are not operating and therefore no longer draw torque from the engine, and the engine is running at its nominal idle speed. The internal temperature of the particulate filter 44 is between the temperature at the reference state E1 and the temperature at the critical state E2, and the oxygen level is closer to the oxygen level at the reference state E1 than to that corresponding to the critical state E2. State E3 prevents thermal runaway and damage to the particulate filter.

[0081] In the event of an unavailability of an electrical energy consumer during the recommended driving mode, under high mass of fine particles, the engine computer must be able to apply a nominal idle speed in order to limit the oxygen supply during a return to idle which could lead to thermal runaway of the particulate filter.

[0082] Indeed, generally speaking, for a given mass of particles in a particle filter, it is necessary to remain below a threshold value for the oxygen level and temperature to avoid a risk of runaway.

[0083] The 60 system for monitoring the status of electrical energy consumers includes a 64 module for checking the status of the engine alternator (not shown).

[0084] The system 60 for monitoring the status of electrical energy consumers includes a module 66 for continuously comparing the load of the engine alternator with a second threshold value S2.

[0085] The 66 comparison module is configured to detect whether the torque is normal or too low, which is the case when an electrical load fails. High torque results in a high alternator load; monitoring the alternator load is used to determine the torque level and, indirectly, the failure of an electrical load.

[0086] The electronic control unit 50 further includes a system 68 for controlling the engine speed according to the detection of the failure of any electrical energy consumers by the supervisory system 60.

[0087] When the alternator load is less than or equal to the second threshold value S2, the engine speed control system 68 transmits a nominal idle speed command to the engine computer.

[0088] When the alternator load is greater than the second threshold value S2, the engine speed control system 68 transmits a fast idle speed command to the engine control unit.

[0089] Monitoring the alternator's load makes it possible to detect a failure of any electrical energy consumer in the vehicle and therefore to do away with a fault detection device specific to the operating mode in driving recommendation.

[0090] As illustrated on the figure 4 , a 100 control process configured to control the various elements of the internal combustion engine and in particular the engine speed.

[0091] In a first step 102, the mass of particles present in the particle filter 44 is compared with a first threshold value S1.

[0092] The first threshold value, S1, corresponds to the highest threshold that allows active regeneration of the particulate filter 44 to be triggered at the lowest speed threshold value by modifying only the combustion mode. The first threshold value, S1, is used to activate the engine's recommended driving mode.

[0093] In a second step 104, the condition of the engine's alternator (not shown) is checked.

[0094] When the alternator is operating and the engine operating mode is in driving recommendation mode, the engine alternator load is continuously compared in step 106 with a second threshold value S2.

[0095] This allows us to detect whether the torque is normal or too low, which is the case when an electrical power consumer fails. High torque results in a high alternator load; monitoring the alternator load is used to determine the torque level and, indirectly, the failure of an electrical consumer.

[0096] Steps 102, 104, 106 correspond to the supervision of the alternator charge and indirectly of the state of electrical energy consumers in order to detect a failure of any electrical energy consumer of the vehicle during an engine operating mode in driving recommendation.

[0097] The process further includes a step 108 of controlling the motor speed according to the detection of the failure of any electrical energy consumer by the supervisory system 60.

[0098] When the alternator's load C is less than or equal to the second threshold value S2, a nominal idle speed command is sent to the engine computer.

[0099] When the alternator's load C is greater than the second threshold value S2, a fast idle speed command is sent to the engine computer.

[0100] The strategy for monitoring electrical energy consumers is autonomous and transparent to the driver, and it requires no mechanical intervention on the engine.

[0101] The time between two vehicle services is thus extended and the cost of vehicle maintenance is reduced by lower fuel consumption and reduced dilution of diesel in the engine oil.

Claims

1. A method (100) for controlling an internal combustion engine comprising a fresh air intake manifold (14), an exhaust manifold (16) and a pollution control system (40) comprising at least a first pollution control device (42) and a particulate filter (44) positioned in the exhaust line (32) downstream of an oxidation catalyst (42), the pollution control system (40) further comprising a differential pressure sensor (P_diff) (46) located upstream and downstream of the particulate filter (44), and a temperature sensor (T1) positioned upstream of said particulate filter (44), characterized in that: - the status of electrical energy consumers is monitored during an engine operating mode corresponding to a driving recommendation, during an autonomous regeneration phase of the particulate filter, in order to detect the failure of any electrical energy consumer capable of drawing torque from the engine; the mass of particles present in the particulate filter (44) is compared with a first threshold value (S1); and - the engine speed is controlled based on the detection of the failure of any electrical energy consumer, such that the load of the engine alternator is continuously compared with a second threshold value (S2), wherein, when the alternator load is less than or equal to the second threshold value (S2), a nominal idle speed command is transmitted to the engine control unit, and when the alternator load exceeds the second threshold value (S2), an accelerated idle speed command is transmitted to the engine control unit.

2. The method according to claim 1, wherein, when monitoring the status of the electrical energy consumers, the status of the engine alternator is checked.

3. An electronic control unit (50) for an internal combustion engine comprising a fresh air intake manifold (14), an exhaust manifold (16) and a pollution control system (40) comprising at least a first pollution control device (42) and a particulate filter (44) positioned in the exhaust line (32) downstream of an oxidation catalyst (42), the pollution control system (40) further comprising a differential pressure sensor (46) (P_diff) positioned upstream and downstream of the particulate filter (44) and a temperature sensor (T1) positioned upstream of said particulate filter (44), characterized in that it comprises: - a system (60) for monitoring the status of the electrical energy consumers during an engine operating mode corresponding to a driving recommendation, during an autonomous regeneration phase of the particulate filter, said system (60) for monitoring the status of the electrical energy consumers during an engine operating mode corresponding to a driving recommendation being configured to detect the failure of any electrical energy consumer capable of drawing torque from the engine, so that the system (60) for monitoring the status of the electrical energy consumers comprises a module (62) for comparing the mass of particles present in the particulate filter (44) with a first threshold value (S1); and - a system (68) for controlling the engine speed based on the detection of the failure of any electrical energy consumer by the monitoring system (60), so that the system (60) for monitoring the status of the electrical energy consumers comprises a module (66) for continuously comparing the load of the engine alternator with a second threshold value (S2), wherein when the alternator load is less than or equal to the second threshold value (S2), the system (68) for controlling the engine speed is configured to transmit a nominal idle speed command to the engine control unit, and wherein when the alternator load is greater than the second threshold value (S2), the system (68) for controlling the engine speed is configured to transmit an accelerated idle speed command to the engine control unit.

4. A control unit (50) according to claim 3, wherein the system (60) for monitoring the status of the electrical energy consumers comprises a module (64) for checking the status of the engine alternator.

5. A motor vehicle comprising an electronic control unit according to any of claims 3 to 4.