Control method and system for a supercharged spark ignition internal combustion engine configured to purge a charge air cooler
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- HORSE POWERTRAIN SOLUTIONS S L U
- Filing Date
- 2024-08-22
- Publication Date
- 2026-07-01
AI Technical Summary
The use of low-pressure exhaust gas recirculation systems in internal combustion engines leads to water condensation in the charge air cooler, causing premature wear, corrosion, and potential engine damage due to the formation of droplets, ice, and sudden water release during engine operation.
A control method and system that estimates the mass of liquid water in the charge air cooler and activates a purge by oscillating the intake air volumetric flow rate between nominal and increased values, using the variable valve timing system to desorb water without disrupting engine torque.
Effectively manages the storage and desorption of liquid water in the charge air cooler, preventing condensation-related issues such as premature wear, corrosion, and engine damage, while maintaining stable engine performance.
Smart Images
Figure EP2024073533_27022025_PF_FP_ABST
Abstract
Description
[0001] DESCRIPTION
[0002] Control method and system for a supercharged spark ignition internal combustion engine configured to purge a charge air cooler
[0003] The present invention relates to the field of spark-ignition internal combustion engines, in particular for motor vehicles, and more particularly to supercharged internal combustion engines, in particular petrol or alcohol or LPG, comprising a partial exhaust gas recirculation system at the intake of the engine.
[0004] More particularly, the invention relates to the reduction of condensation, or even purging, in a charge air cooler.
[0005] As the pollutant emission standards of internal combustion engines such as spark-ignition engines are increasingly stringent, these engines are generally designed with Exhaust Gas Recirculation (EGR) systems. Such EGR systems generally comprise a recirculation circuit for the high- pressure duct sampling the exhaust gases upstream of the turbine of the turbocharger, a recirculation circuit for the low-pressure duct sampling the exhaust gases downstream of a depollution device of the exhaust line, and a heat exchanger in order to cool the gases present in the low-pressure recirculation circuit and to reintroduce them at the inlet of the engine. The low- pressure EGR circuit allows burnt gases from combustion to be sucked back into the intake and reintroduced upstream of the supercharger.
[0006] These inert gases make it possible in particular to increase the total mass of gas admitted into the combustion chamber in a petrol engine, which reduces the need to lower the pressure of the intake manifold to manage the air load. This limits pumping losses and improves combustion. This results in a decrease in fuel consumption.
[0007] More particularly, the present invention relates to gas recirculation systems comprising a cold water charge air cooler (W-CAC) located downstream of the turbocharger system compressor and upstream of the intake manifold and a variable valve timing (VVT) distribution system.
[0008] In order to meet the emission standards, internal combustion engines may be forced to use the cold low-pressure gas recirculation circuit. However, the low-pressure gas recirculation circuit contains water-laden burnt gases. Thus, when the engine is cold, there is a risk of condensation of the water present in the gas recirculation system at the charge air cooler.
[0009] The use of a low-pressure EGR circuit therefore leads to problems of water condensation in the engine intake circuit. This water generally comes from the moisture of the fresh air arriving from the fresh air inlet and / or from the water vapour contained in the exhaust gases recirculated by the low-pressure EGR circuit.
[0010] This condensed water can then lead to:
[0011] - the projection of droplets of liquid water upstream of the compressor, resulting in premature wear of the wheel of said compressor;
[0012] - the storage of water in low points of the intake circuit resulting in corrosion issues, for example of the charge air cooler or the EGR cooler.
[0013] - the formation of ice in the intake circuit under extreme ambient conditions, either during the driving phase or during the cooling of the engine at a standstill. Slow progressive storage concomitant with freezing can then lead to ice storage. When the ambient temperature rises above 0°C, this ice turns into liquid, which in turn can cause corrosion or premature wear of the compressor wheel. This water can also be sucked by the engine, especially during the starting phase of the engine, and damage it.
[0014] In addition, during operating phases promoting the condensation of water, for example because of environmental conditions, such as high ambient humidity and / or low ambient temperature, or because of the operation of the engine, the water vapour contained in the mixture of fresh air and EGR gas is likely to condense in the intake circuit and in particular on the surface of the charge air cooler.
[0015] This water is stored in the cooler and can be desorbed, which can disrupt the combustion of the engine or even extinguish it. Indeed, the storage of water in the charge air cooler can be followed by a sudden release phenomenon, especially during a sharp increase in the flow rate of the EGR air and gas mixture sucked by the engine, for example, following a request for a full load when the driver presses the accelerator pedal. This sudden release of liquid water into the combustion chamber can lead to combustion quenching, i.e. the absence of torque generation or misfiring, known as a "misfire", which can, in the long run, damage the engine or some of its associated components as an mission catalyst.
[0016] In order to avoid such a phenomenon of condensation, the engine operates with the high-pressure exhaust gas recirculation circuit while waiting for the temperature of the intake line to reach a threshold value to avoid condensation in the charge air cooler.
[0017] Document FR 3 064 678 - B1 is known, which proposes a solution for estimating the risk of condensation in the charge air cooler in order to control the exhaust gas recirculation system. Thus, in case of water accumulation in the charge air cooler, the EGR valve is closed in order to wait for favourable conditions to evacuate the condensed water. However, such a solution is not satisfactory because it requires the EGR valve to be closed for a long time, which leads to a deterioration in fuel consumption. Furthermore, such a solution does not eliminate the condensed water already present in the charge air cooler.
[0018] There is a need to improve the management of the storage and desorption of liquid water in the intake circuit, and more particularly in the charge air cooler of a supercharged spark ignition internal combustion engine.
[0019] It is therefore an object of the present invention to provide an engine control method and system configured to manage the storage and desorption of liquid water in the charge air cooler.
[0020] The object of the present invention is a method for controlling a spark-ignition internal combustion engine comprising at least one cylinder, a fresh air intake manifold supplied with fresh air via a duct, a compressor of a turbocharger and a heat exchanger downstream of said compressor and upstream of the intake manifold, the engine further comprising an exhaust circuit comprising, from upstream to downstream in the direction of flow of the burnt gases, an exhaust manifold, a turbine of the turbocharger and, for example, a system for emitting the combustion gases of the engine.
[0021] The engine further comprises a partial intake exhaust gas recirculation circuit originating at a point in the exhaust circuit, downstream of said turbine, and opening into the fresh air supply duct, upstream of the turbocharger compressor.
[0022] Said partial recirculation circuit comprising a low pressure control valve V EGR LP mounted upstream of the duct.
[0023] The engine further comprising a variable valve timing system (VVT) configured to control the lift of the valves between a bottom dead centre (BDC) at the exhaust, a top dead centre (TDC) and a bottom dead centre at the intake (BDC).
[0024] According to the method:
[0025] - the mass of liquid water stored in real time on the internal walls of the exchanger is estimated;
[0026] - the said estimated mass is compared with a threshold value; and
[0027] - the cooler purge is activated when the estimate of the mass of water is greater than the threshold value, by generating oscillations in the volumetric flow rate of intake air entering the exchanger between a nominal volumetric flow rate value and an increased volumetric flow rate value.
[0028] These variations in intake air volumetric flow rate make it possible to force the water accumulated on the walls of the cooler to stall, while maintaining a stable engine torque around the torque setpoint.
[0029] The heat exchanger can be a cold water charge air cooler (W-CAC) or a charge air cooler (CAC).
[0030] Thus, VVT valve lift setpoints are made, and therefore the crossing value to generate jumps in volumetric flow rate at the intake.
[0031] This makes it possible to very significantly increase the volumetric flow rate with respect to the reference setting of the engine in order to desorb the water by the effect of tearing off the liquid film formed on the walls of the exchanger.
[0032] Such a solution is more effective than those using mass flow variation.
[0033] It is therefore the velocity of the gases within the exchanger that will vary greatly and not the density of the gases.
[0034] Advantageously, the step of activating the purge comprises a step of determining the operating point of the engine (speed / load) between a supercharged operating mode and an atmospheric operating mode, i.e. not supercharged.
[0035] For example, the oscillations of the intake air volumetric flow rate are achieved by controlling the variable valve timing distribution system by performing oscillations of the valve crossing areas corresponding to the angular duration during which the intake and exhaust valves are simultaneously open around the top dead centre between a nominal crossing value and a higher crossing value, for example between 30°Vil and 60°Vil, preferably equal to 60°Vil, when the engine is operating in supercharged operating mode and between a nominal crossing value and a decreased crossing value, for example equal to 0°Vil when the engine is operating in atmospheric mode, i.e. not supercharged.
[0036] The generation of the oscillations of the intake air flow entering the exchanger and the generation of the oscillations of the crossing areas of the valves are preferably carried out simultaneously.
[0037] For example, the intake air volumetric flow oscillations form oscillating slots between the nominal volumetric flow value and the increased volume flow value and the generation of the oscillations of the valve crossing areas forms oscillating slots between a nominal crossing value and a higher crossing value, for example between 30°Vil and 60°Vil, preferably equal to 60°Vil, when the engine is operating in supercharged mode and between a nominal crossing value and a decreased crossing value, for example equal to 0°Vil when the engine is operating in atmospheric mode, i.e. not supercharged.
[0038] For example, the slots have an identical time period between the rising and falling phases, for example between 1 s and 2s, for example equal to 1 .5s.
[0039] For example, the purge step has a duration necessary to evacuate the water from the re-cooler of between 8s and 12s, preferably equal to 10s.
[0040] According to a second aspect, the invention relates to an electronic control unit for a spark-ignition internal combustion engine comprising at least one cylinder, a fresh air intake manifold supplied with fresh air via a duct, a compressor of a turbocharger and a heat exchanger downstream of said compressor and upstream of the intake manifold, the engine further comprising an exhaust circuit comprising, from upstream to downstream in the direction of flow of the burnt gases, an exhaust manifold, a turbine of the turbocharger and, for example, a system for emitting the combustion gases of the engine. The engine further comprises a partial intake exhaust gas recirculation circuit originating at a point in the exhaust circuit, downstream of said turbine, and opening into the fresh air supply duct, upstream of the turbocharger compressor, the said intake circuit comprising an adjustment valve or throttle box mounted between the compressor and the heat exchanger.
[0041] Said partial recirculation circuit comprising a low pressure control valve V EGR LP mounted upstream of the duct.
[0042] The engine further comprising a variable valve timing system, VVT, configured to control the lift of the valves between a bottom dead centre at the exhaust, a top dead centre and a bottom dead centre at the intake.
[0043] The electronic control unit comprises an engine control system comprising:
[0044] - a module for estimating the mass of liquid water stored in real time on the internal walls of the exchanger;
[0045] - a module for comparing the estimate of the mass of water with a threshold value; and
[0046] - a module for activating the cooler purge when the estimate of the mass of water is greater than the threshold value configured to generate oscillations in the volumetric flow rate of intake air entering the exchanger between a nominal volumetric flow rate value and an increased volumetric flow rate value.
[0047] Advantageously, the cooler purge activation module comprises a module for determining an operating point of the engine between a supercharged operating mode and a non-supercharged operating mode.
[0048] For example, the cooler purge activation module comprises a control module of the variable valve lift timing distribution system by making slots of the valve crossing zones corresponding to the angular duration during which the intake and exhaust valves are simultaneously open around top dead centre between a nominal crossing value and a higher crossing value, for example between 30°Vil and 60 °Vil, preferably equal to 60°Vil, when the engine is operating in supercharged mode and between a nominal crossing value and a decreased crossing value, for example equal to 0°Vil when the engine is operating in atmospheric mode, i.e. not supercharged.
[0049] According to another aspect, the invention relates to a motor vehicle comprising an electronic control unit as described above.
[0050] Other aims, characteristics and advantages of the invention will become apparent on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings wherein:
[0051] [Fig.1 ] shows, very schematically, an exemplary structure of an internal combustion engine of a motor vehicle comprising a control unit comprising a control system according to the invention;
[0052] [Fig.2a], [Fig.2b] illustrate the lift of the valves, respectively without offset and with offset;
[0053] [Fig.3] shows the effect of the variable timing crossing on the volumetric filling efficiency as a function of the engine operating point;
[0054] [Fig.4a] illustrates slot curves of the control signals from the control system according to [Fig.1 ] in the case of an operating point of the supercharged engine;
[0055] [Fig.4b] illustrates slot curves of the control signals from the control system according to [Fig.1 ] in the case of an operating point of the non-supercharged engine;
[0056] [Fig.5] illustrates a curve of the charge air cooler purge activation principle as a function of time on the x-axis and the mass of water accumulated in the cooler on the y-axis; and [Fig.6] shows the block diagram of a method for controlling according to the invention implemented by the control unit of [Fig.1 ].
[0057] In [FIG. 1], the general structure of an internal combustion engine 10, of the spark-ignition type operating in particular on petrol, of a motor vehicle has been represented schematically. As a variant, it may be an engine running on alcohol or liquefied gas of the LPG type.
[0058] These architectures are given by way of example and do not limit the invention to the only configuration to which the control of the engine according to the invention can apply.
[0059] In the example illustrated, the internal combustion engine 10 comprises, in a non-limiting manner, three in-line cylinders 12, a fresh air intake manifold 14, an exhaust manifold 16 and a turbo charging system or turbocharger 18.
[0060] The cylinders 12 are supplied with air via the intake manifold 14, or intake distributor, itself supplied with air via a duct 20 provided with an air filter 22 and the compressor 18b of the turbocharger 18 of the engine 10.
[0061] Each cylinder 12 is supplied with fuel, for example of the petrol type.
[0062] In a known manner, 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, with the aim of increasing the quantity (mass flow rate) of air admitted to the cylinders 12 of the engine 10. The turbine 18a may be of the “variable geometry” type, i.e. the turbine impeller is equipped with variable inclination vanes in order to modulate the amount of energy taken from the exhaust gases, and thus the supercharging pressure.
[0063] A heat exchanger 26 is placed after the outlet of the compressor 18b equipping the duct 14a of the intake manifold 14 with fresh air.
[0064] The internal combustion engine 10 thus comprises an intake circuit Ca, an exhaust circuit Ce and a fuel injection circuit (not shown).
[0065] The intake circuit Ca comprises, from upstream to downstream in the direction of air circulation:
[0066] - air filter 22 or air box;
[0067] - the compressor 18b of the turbocharger 18 configured to compress the air sampled from the outside atmosphere and, if necessary, recycled exhaust gases at low pressure, such as will be described later;
[0068] - a throttle housing 24 or a gas intake valve in the engine;
[0069] - a heat exchanger 26 configured to cool the intake gases corresponding to a mixture of fresh air and recycled gases after they have been compressed in the compressor 18b; and
[0070] - intake manifold 14.
[0071] The heat exchanger 26 is a cooler of the so-called "supercharged" intake gases, corresponding, here, to an air-water exchanger, called "water charged air cooler" in English terms. The terms "heat exchanger 26" and "charge air cooler 26" hereinafter refer to the same element. Alternatively, it may be an air-to-air cooler.
[0072] The intake circuit Ca may also comprise a flow meter (not shown) arranged in the intake duct 20 downstream of the air filter 22; the flow meter being configured to measure the actual value of the air flow entering the engine 10. The flow meter only measures the flow of fresh air alone.
[0073] The exhaust circuit Ce comprises, from upstream to downstream in the direction of flow of the burnt gases:
[0074] - exhaust manifold 16;
[0075] - the turbine 18a of the turbocharger 18 configured to draw energy from the exhaust gases passing through it, said expansion energy being transmitted to the compressor 18b via the common shaft, for compression of the intake gases;
[0076] - an engine combustion gas de-pollution system 40.
[0077] With regard to the exhaust manifold 16, the latter recovers the exhaust gases from the combustion and discharges them to the outside, via a gas exhaust duct 28 leading to the turbine 18a of the turbocharger 18 and via an exhaust line 30 mounted downstream of said turbine 18a.
[0078] By way of a non-limiting example, the system 40 for emission control of the combustion gases of the engine comprises a first device 42 comprising a three-way catalyst.
[0079] The emission control system 40 further comprises a second device 55 which here is a fine particle filter, and an exhaust pipe 32 mounted at the outlet of the second emission control device 55 and opening outwards.
[0080] As illustrated, the engine 10 comprises a partial exhaust gas recirculation (EGR) circuit 50 at intake.
[0081] This circuit 50, here a low-pressure exhaust gas recirculation circuit, called "EGR BP", originates at a point in the exhaust line 30, here, in the exhaust pipe 32, downstream of said turbine 18a, and in particular, in the case of [Fig. 1], downstream of the gas emission control system 40 and returns the exhaust gases to a point of the fresh air supply duct 20, upstream of the compressor 18b of the turbocharger 18, in particular downstream of the air filter 22.
[0082] In a variant not shown, the low-pressure exhaust gas recirculation circuit could originate at the outlet of the turbine 18a, or else downstream of only part of the gas emission control system 40, for example between the first and the second emission control devices 42, 55.
[0083] As illustrated, this recirculation circuit 50 comprises, in the direction of flow of the recirculated gases, a “V EGR BP” regulator valve 52 configured to adjust the flow of exhaust gases at low pressure and an EGR gas cooler 54. The “V EGR LP” valve 52 is arranged upstream of the cooler 54 and the said cooler 54 is arranged upstream of the compressor 18b.
[0084] By way of a non-limiting example, the engine is associated with a fuel circuit comprising, for example, fuel injectors (not referenced) injecting petrol directly into each cylinder from a fuel tank (not shown).
[0085] The engine 10 also comprises a variable valve timing (VVT) system 27 configured to control the lift of the valves in the engine 10.
[0086] The valves are used to control the flow of intake and exhaust gases into and out of the combustion chamber. The timing, duration and lift of the valves have a significant impact on engine performance. Without variable valve timing, or variable valve lift, the valve timing is the same for all engine speeds.
[0087] Recent piston engines typically comprise valves driven by camshafts. The cams lift the valves for a certain period of time during each intake and exhaust cycle.
[0088] Figures 2a and 2b illustrate the lift of the valves between the bottom dead centre at the exhaust BDC, the top dead centre TDC and the bottom dead centre at the intake BDC, as a function of the crankshaft angle, respectively without VVT offset and with VVT offset.
[0089] [Fig.2b] illustrates the operating mode of the variable valve timing system 27. Said system 27 is configured to angularly offset the laws of camshafts at the intake and exhaust with an offset of 20° crankshaft at the intake and exhaust making it possible to obtain a crossing area of 40° crankshaft.
[0090] An important concept is this value of the valve crossing area, corresponding to the angular duration (crankshaft degree) during which the intake and exhaust valves are simultaneously open around the crossing top dead centre, which positions in the cycle the end of exhaust gas draining and the beginning of fresh gas intake.
[0091] For a given speed, the value of the crossing area will condition the volumetric filling efficiency of the engine to order 1 , that is to say the volumetric flow rate of the gases at the intake and therefore the speed of the gases at the intake.
[0092] The volumetric efficiency q_rdvl is calculated according to a filling concept according to the following equation:
[0093] With: n_rdvl, volumetric efficiency;
[0094] Qmot, the total flow actually entering, in kg / s;
[0095] Displacement, the displacement of the engine, in m3;
[0096] Pcoll, the pressure in the intake manifold, in Pascal;
[0097] Tcoll, the temperature in the intake manifold, in K; r, a mass constant of ideal gases for air equal to 287,058 J-kg1-K1; and
[0098] N, the speed, in rpm.
[0099] "Filling" means the mass of air actually sucked in with respect to the mass of air that could theoretically have been sucked in considering the total volume of the cylinders.
[0100] The value of the volumetric efficiency depends at least on the speed N and the pressure Pcoll in the intake manifold of the engine. Then, depending on the technical definition of the engine, the volumetric efficiency may also depend on the adjustment of other equipment, such as for example the adjustment of the position of one or more variable timing distribution systems for a given operating point, the adjustment of the position of a valve lift system, known as VVL, etc.
[0101] The valve opening law influences the permeability of the combustion chambers.
[0102] The direction of variation of the volumetric efficiency according to the crossing of the valves depends on the type of operating point, as shown in [Fig .3].
[0103] In the so-called "supercharged" operating mode, i.e. essentially at high or full load, the pressure Pcoll in the intake manifold 14 is higher than the atmospheric pressure and the pressure in the exhaust manifold 16.
[0104] The reference timing of variable timing valve systems is generally characterized by low levels of valve crossing to optimise engine emissions, such as particulate matter, carbon dioxide, CO or nitrogen oxides, NOx.
[0105] When the crossing of the valves is increased at this type of operating point, the volumetric filling efficiency is in turn increased because fresh air passes directly from the inlet to the exhaust to evacuate the burnt gases.
[0106] In the so-called "atmospheric" operating mode, i.e. essentially at low load or medium load for relatively low speed values, the pressure Pcoll in the intake manifold 14 is less than the atmospheric pressure and the pressure in the exhaust manifold 16.
[0107] The reference timing of variable timing valve systems is generally characterised by high levels of valve crossing to reduce valve pumping work and minimise fuel consumption.
[0108] When the crossing of the valves is reduced at this type of operating point, the volumetric filling efficiency is in turn increased because the rate of burnt gases recirculated to the inlet is reduced.
[0109] The engine includes an electronic control unit ECU 60 including a control system 70 configured to control the variable valve lift timing distribution system 27.
[0110] The control system 70 receives data collected by sensors at different locations in the engine or estimates.
[0111] The control system 70 could receive other data, such as temperatures at different locations in the engine, or other pressures.
[0112] The control system 70 comprises a module 71 for estimating the mass M water of liquid water stored in real time on the internal walls of the exchanger 26.
[0113] Indeed, the activation of the purge strategy is dependent on the accumulated water mass, as can be seen in [Fig.5].
[0114] The estimate of the mass M water of liquid water stored in real time on the internal walls of the exchanger 26 can be carried out for example as a function of the temperature of fresh air admitted, the air flow rate obtained by the flow meter, and an estimate of the ambient relative moisture, either through a moisture rate sensor arranged in the intake circuit Ca, for example in the flow meter, or outside the vehicle, or by a meteorological service especially if the vehicle is a so-called "connected" vehicle, or by the method described in patent FR 3 064 678-B1 .
[0115] The control system 70 comprises a module 72 for comparing the estimate of the mass of water M water with a threshold value S.
[0116] The threshold value S may correspond to a maximum mass of liquid water that can be stored in the exchanger 26.
[0117] In order to determine the threshold value S, the exchanger 26 can, for example, be weighed in the dry state, the volume usually traversed by the mixture of air and EGR gas is completely filled with water, said exchanger 26 is installed on a test bench and blown through with a constant air flow until the water contained therein is mechanically evacuated, without waiting for the water to evaporate. Next, the exchanger 26 is weighed to estimate the mass of water it has retained. This mass corresponds to the threshold value S of storable liquid water, for the constant air flow rate considered.
[0118] Alternatively, the threshold value S could correspond to a critical mass of water corresponding to the mass of water which runs the risk of quenching the combustion if a desorption phenomenon were to occur, for example in the event of a large increase in the air flow admitted by the engine, following an acceleration request, for example.
[0119] The critical mass of water can be estimated by tests, on a stationary engine bench, by injecting an increasing mass of liquid water at the intake of the cylinders and by measuring the internal combustion pressure which makes it possible to estimate the indicated torque produced. Then, we deduce the maximum permissible mass of liquid water per combustion cycle and per cylinder, corresponding to a combustion defect. The critical water mass for the engine can then be deduced by knowing the engine dynamics, i.e. the duration, and therefore the number of combustion cycles that are required to reach a critical stage for the engine.
[0120] The control system 70 comprises a module 74 for activating the purge of the cooler 26 when the estimate of the mass of water M water is greater than the threshold value S.
[0121] The purge activation module 74 comprises a module 75 for determining the operating point of the engine between a supercharged operating mode and a non-supercharged operating mode.
[0122] The purge activation module 74 further comprises a control module 76 of the variable valve lift timing distribution system 27 VVT to generate oscillations of the valve crossing areas and thus to generate variations of the intake air volumetric flow rate between a nominal flow rate value Qvol_name and an increased flow rate value Qvol_+ when the engine is operating in supercharged mode and in atmospheric mode.
[0123] In one embodiment, said increased volumetric flow rate value may be equal to the maximum volumetric flow rate value of the engine corresponding to the fully open position of the throttle box 24. More generally, this is a flow rate value that is greater than the nominal flow rate value.
[0124] These variations in intake air volumetric flow rate make it possible to force the water accumulated on the walls of the coolers 26 to stall.
[0125] These intake air flow rate variations are obtained by performing slots on valve crossing areas between a nominal crossing value CVVT name and a higher crossing value CVVT_+, for example between 30°Vil and 60 °Vil, for example equal to 60°Vil, when the engine is operating in supercharged mode and between a nominal crossing value CVVT name and a decreased crossing value CVVT -, for example equal to 0°Vil when the engine is operating in atmospheric mode, i.e. not supercharged.
[0126] The values of the air flow Qvol and the CWT crossing areas come from an engine computer (not shown) integrated into the ECU comprising pairs of air flow / CVVT crossing areas for an engine speed / load operating point.
[0127] [Fig.4a] shows slot curves respectively of the volumetric air flow rate Qvol passing through the cooler 26, of the crossing areas of the CWT valves and of the engine torque C, as a function of time in seconds.
[0128] As can be seen in [Fig.4a], the intake air volumetric flow rate variations form oscillating slots between the nominal flow rate value Qvol_name and the increased volumetric flow rate value Qvol_+ and the valve crossoving areas modulation forms oscillating slots between a nominal crossing value CVVT name and a higher crossing value CVVT_+, for example between 30°Vil and 60°Vil, for example equal to 60°Vil.
[0129] The slots preferably have an identical time period T between the rising and falling phases, for example between 1 s and 2s, for example equal to 1 .5s.
[0130] For example, the duration of the purge phase St required to evacuate the water from the cooler 26 is between 8s and 12s, for example equal to 10s.
[0131] To the extent that variations in valve opening impact the intake air mass and engine efficiency, the boost pressure and ignition advance are preferably adjusted so that the engine delivers a constant effective torque so that the duct is not disturbed. This is known to those skilled in the art and is calculated automatically by the electronic control unit 70 of the engine.
[0132] [Fig.4b] shows slot curves respectively of the volumetric air flow rate Qvol passing through the cooler 26, of the crossing areas of the CWT valves and of the engine torque C, as a function of time in seconds. As can be seen in [Fig.4b], the intake air volumetric flow rate variations form oscillating slots between the nominal flow rate value Qvol_name and the increased volume flow rate value Qvol_+ and the modulation of the valve crossing areas forms oscillating slots between a nominal crossing value CVVT name and a decreased crossing value CVVT -, for example equal to 0°Vil.
[0133] The slots preferably have an identical time period T between the rising and falling phases, for example between 1 s and 2s, for example equal to 1 .5s.
[0134] For example, the duration of the purge phase St required to evacuate the water from the cooler 26 is between 8s and 12s, for example equal to 10s.
[0135] To the extent that variations in valve opening impact the intake air mass and engine efficiency, the opening of the throttle box and the ignition advance are preferably adjusted so that the engine delivers a constant effective torque so that the duct is not disrupted. This is known to those skilled in the art and is calculated automatically by the electronic control unit of the engine.
[0136] As illustrated in detail in [Fig.6], the engine control method 100 includes a step 102 of estimating the mass M water of liquid water stored in real time on the internal walls of the exchanger 26.
[0137] The method 100 for controlling the engine further comprises a step 104 of comparing the estimate of the mass of water M water with a threshold value S.
[0138] The method 100 for controlling the engine further comprises a step 1 10 of activating the purge of the cooler 26 when the estimate of the mass of water M water is greater than the threshold value S.
[0139] The step 110 of activating the purge of the cooler 26 comprises a step 11 1 of determining the operating point of the engine between a supercharged operating mode and a non-supercharged operating mode.
[0140] The step 1 10 of activating the purge of the cooler 26 further comprises a step 112 of controlling the variable valve lift timing distribution system 27 VVT to generate oscillations of the crossing areas of the valves and thus to generate variations of the intake air volumetric flow rate between a nominal flow rate value Qvol_name and an increased flow rate value Qvol_+ when the engine is operating in supercharged mode and in atmospheric mode.
[0141] The variable valve timing distribution system 27 of the VVT valves is controlled in step 1 12 to perform oscillations of the crossing areas of the CWT valves corresponding to the angular duration during which the intake and exhaust valves are simultaneously open around the top dead centre TDC between a nominal crossing value CVVT name and a higher crossing value CVVT_+, for example between 30°Vil and 60°Vil, preferably equal to 60°Vil, when the engine is operating in supercharged mode and between a nominal crossing value CVVT name and a decreased crossing value CVVT -, for example equal to 0°Vil when the engine is operating in atmospheric mode, i.e. not supercharged.
[0142] The generation of the oscillations of the intake air flow Qvol entering the exchanger 26 and the generation of the oscillations of the crossing areas of the CWT valves are carried out simultaneously.
[0143] Thanks to the invention, it is possible to purge the air cooler in order to avoid any risk of rapid desorption and quenching of the combustion of the engine, while keeping a torque generated by the engine constant around a target value.
[0144] The advantage of the proposed solution is to be able to vary the volumetric flow rate at the intake very significantly at iso-rpm and iso-load (torque) of the engine, therefore without disturbing the operating mode of the vehicle.
Claims
CLAIMS1. Method (100) for controlling a spark-ignition internal combustion engine (10) comprising at least one cylinder (12), a fresh air intake manifold (14) supplied with fresh air through a duct (20), a compressor (18b) of a turbocharger (18) and a heat exchanger (26) downstream of said compressor (18b) and upstream of the intake manifold (14), the engine further comprising an exhaust circuit (Ce) comprising, from upstream to downstream in the direction of flow of the burnt gases, an exhaust manifold (16), a turbine (18a) of the turbocharger (18) and a partial recirculation circuit (50) of the exhaust gases at the intake starting at a point of the exhaust circuit (Ce), downstream of said turbine (18a), and opening outwards into the fresh air supply duct (20), upstream of the compressor (18b) of the turbocharger (18), said partial recirculation circuit (50) comprising a low pressure adjustment valve (V EGR BP 52) mounted upstream of the duct (20), the engine further comprising a variable timing variable valve timing system (27) configured to control valve lift (VVT) between an exhaust bottom dead centre (exhaust BDC), a top dead centre (TDC) and an intake bottom dead centre (intake BDC), wherein:- the mass (M water) of liquid water stored in real time on the internal walls of the exchanger (26) is estimated;- the said estimated mass (M water) is compared with a threshold value (S); and- the cooler purge (26) is activated when the water mass estimate (M water) is greater than the threshold value (S), by generating oscillations of the intake air volumetric flow rate (Qvol) entering the exchanger (26) between a nominal volumetric flow rate value (Qvol_name) and an increased flow rate value (Qvol_+).
2. The method according to claim 1 , wherein the step of activating the purge comprises a step of determining the engine operating point between a supercharged operating mode and a non-supercharged operating mode.
3. The method according to claim 2, wherein the oscillations of the intake air volumetric flow rate (Qvol) are performed by controlling the variable valve timing distribution system (VVT) by performing oscillations of the valve crossing areas (CWT) corresponding to the angular time during which the intake and exhaust valves are simultaneously opened around the top dead centre (TDC) between a nominal crossing value (CVVT name) and a higher crossing value (CVVT_+), for example between 30°Vil and 60 °Vil, preferably equal to 60°Vil, when the engine is operating in supercharged mode and between a nominal crossing value (CVVT name) and a decreased crossing value (CVVT -), for example equal to 0°Vil when the engine is operating in non-supercharged mode.
4. The method according to claim 3, wherein the generation of the oscillations of the intake air flow (Qvol) entering the exchanger (26) and the generation of the oscillations of the crossing areas of the (CWT) valves are carried out simultaneously.
5. The method according to claim 3 or 4, wherein the intake air volumetric flow rate oscillations form oscillating slots between the nominal volumetric flow value (Qvol_nom) and the increased volume flow value (Qvol_+) and the generation of the oscillations of the valve crossing areas (CWT) forms oscillating slots between a nominal crossing value (CVVT name) and a higher crossing value (CWT +), for example between 30°Vil and 60°Vil, preferably equal to 60°Vil, when the engine is operating in supercharged mode and between a nominal crossing value (CVVT name) and a decreased crossing value (CVVT -), for example equal to 0°Vil when the engine is operating in non-supercharged mode.
6. The method according to claim 5, wherein the slots have an identical time period (T) between the rising and falling phases, for example between 1 s and 2s, for example equal to 1 .5s.
7. The method according to claim 5 or 6, wherein the purge step has a duration (St)necessary to evacuate the water from the cooler (26) between 8s and 12s, preferably equal to 10s.
8. Electronic control unit ECU of a spark-ignition internal combustion engine (10) comprising at least one cylinder (12), a fresh air intake manifold (14) supplied with fresh air through a duct (20), a compressor (18b) of a turbocharger (18) and a heat exchanger (26) downstream of said compressor (18b) and upstream of the intake manifold (14), the engine further comprising an exhaust circuit (Ce) comprising, from upstream to downstream in the direction of flow of the burnt gases, an exhaust manifold (16), a turbine (18a) of the turbocharger (18) and a partial recirculation circuit (50) of the exhaust gases at the intake starting at a point of the exhaust circuit (Ce), downstream of said turbine (18a), and opening outwards into the fresh air supply duct (20), upstream of the compressor (18b) of the turbocharger (18), said partial recirculation circuit (50) comprising a low pressure adjustment valve (V EGR BP 52) mounted upstream of the duct (20), the engine further comprising a variable timing variable valve timing system (27) configured to control valve lift (VVT) between an exhaust bottom dead centre (exhaust BDC), a top dead centre (TDC) and an intake bottom dead centre (intake BDC), the electronic control unit ECU comprising an engine control system (70) comprising:- a module (71 ) for estimating the mass (M water) of liquid water stored in real time on the internal walls of the exchanger (26);- a module (72) for comparing the estimate of the mass of water (M water) with a threshold value (S); and- a module (74) for activating the purge of the cooler (26) when the estimate of the mass of water (M water) is greater than the threshold value (S) configured to generate oscillations of the intake air volume flow rate (Qvolf) entering the exchanger (26) between a nominal volumetric flow rate value (Qvol_name).
9. The electronic control unit ECU according to claim 8, wherein the module (74) for activating the purge of the cooler (26) comprises a module (75) for determining an operating point of the engine between a supercharged operating mode and a non-supercharged operating mode.
10. The electronic control unit ECU according to claim 9, wherein the module (74) for activating the purge of the cooler (26) comprises a module (76) for controlling the system (27) for distributing the variable valve lift timing by performing slots of the valve crossing areas (CWT) corresponding to the angular time during which the intake and exhaust valves are simultaneously opened around the top dead centre (TDC) between a nominal crossing value (CWT name) and a higher crossing value (CWT_+), for example between 30°Vil and 60 °Vil, preferably equal to 60°Vil, when the engine is operating in supercharged mode and between a nominal crossing value (CWT name) and a decreased crossing value (CWT -), for example equal to 0°Vil when the engine is operating in non-supercharged mode.
11. Motor vehicle comprising an electronic control unit according to any one of claims 8