Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/18—Circuit arrangements for generating control signals by measuring intake air flow
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2200/00—Input parameters for engine control
  • F02D2200/02—Input parameters for engine control the parameters being related to the engine
  • F02D2200/04—Engine intake system parameters
  • F02D2200/0402—Engine intake system parameters the parameter being determined by using a model of the engine intake or its components

Definitions

• the invention relates to an estimating method and an estimator of a mass Ma of fresh air admitted inside a combustion chamber of a cylinder of a motor during a motor cycle.
• the invention also relates to a method of estimating the total charge of fresh air supercharged from the combustion chamber and a vehicle equipped with the estimator.
• An engine cycle successively comprises the exhaust of the burnt gases from the combustion chamber, the admission of fresh air and fuel into the combustion chamber and the explosion of the mixture in this combustion chamber.
• an engine cycle is two round trips of piston in the cylinder between the two extreme positions of its stroke, that is to say the top dead center (TDC) and the point low death (PMB).
• the power delivered by an internal combustion engine is a function of the amount of air introduced into the combustion chamber of the engine. This quantity of air is itself proportional to the density of this air. Therefore, in case of high power demand, it is expected to increase the amount of air by means of compression of the air before it is admitted into the combustion chamber.
• This operation is more commonly known as supercharging and can be performed by a supercharging device such as a turbocharger or a driven compressor such as a screw compressor.
• this scanning is obtained by simultaneously opening the exhaust and intake valves of the same combustion chamber for a few degrees to a few tens of degrees of angle. rotation of the crankshaft. Typically, this occurs at the end of the flue gas exhaust and at the beginning of the intake of fresh air. Specifically, the fact that the air pressure at the open intake valve is higher than the pressure at the exhaust valve creates a flow of air that passes directly from the intake to the exhaust valve. exhaust resulting in passing part of the residual burnt gases present in the combustion chamber. This period during which the intake and exhaust valves are simultaneously open is called "valve crossing".
• valve crossover In the case of atmospheric engines, that is to say engines without supercharging, a valve crossover can also be provided. In this case, during the crossing of valves, flue gases are sucked into the combustion chamber. It is said that the flue gases are re-aspirated. This feature is known by the acronym IGR (Internal Gas Recirculation) or Internal Recirculation of Exhaust Gas.
• the invention aims to overcome this disadvantage by providing a more accurate method for estimating the amount of fresh air admitted into a combustion chamber.
• the estimates of the total mass Mtot and the mass Mb of burnt gases can be established precisely without measuring the pressure or the temperature inside the combustion chamber. Therefore, this method of estimating the mass Ma is more accurate.
• the embodiments of this method of estimating the mass Ma may comprise one or more of the characteristics corresponding to the variants described hereinafter.
• the estimate of the mass Mb of burnt gas comprises the estimation of a mass Mb_resi of residual burnt gas contained in the combustion chamber at the end of the exhaust of the burnt gases, and the estimating a mass Mb_reasp of burnt gases re-aspirated inside the combustion chamber during the crossing of valves.
• the estimation of the mass Mb_resi is obtained from a pressure P ECH of the burnt gases, an internal volume of the combustion chamber at the end of the exhaust of the burnt gases, d a temperature T ECH of the burnt gases and a correction coefficient A ECH of the pressure P ECH whose value is a function of an end-of-exhaust angle and the engine speed.
• This mode also makes it possible to obtain an accurate estimate of the mass of residual burnt gases in the combustion chamber at the end of the exhaust without it being necessary to measure the pressure or the temperature inside the combustion chamber. combustion.
• the estimation of the mass Mb_reasp is obtained using the following relation:
• r is a constant equal to the following ratio R / M where R is the universal constant of perfect gases and M is the molar mass in kg. mol "1 of flue gases,
• - Sbase is a corrective value depending on the engine speed and the difference between angles FE and OA, respectively, of exhaust closure and intake opening and,
• - Scor is a corrective value according to the difference between the angles FE and OA and the engine speed
• ⁇ is the ratio of the heat capacity at constant pressure of the flue gases to the heat capacity at constant volume of the flue gases, - ⁇ O (PADM / PECH) is defined by the following relation:
• the estimate of the total mass Mtot is obtained from an admission pressure P ADM of the air, a volume of the combustion chamber at the end of the admission, of a temperature T m ang ang du of the mixture of fresh air and flue gas contained in the combustion chamber at the end of the intake of fresh air, and a correction coefficient A ADM whose value is obtained from a prerecorded cartography according to an angle FA end of admission and the engine speed.
• the estimate of the mass Ma of fresh air is a solution of the system of equations. next :
• - AADM is a correction coefficient whose value depends on the engine speed and the end of intake angle
• Vcyl_FA is the geometric volume of the combustion chamber calculated at the end angle of admission
• Tmixture is the temperature of the mixture of fresh air and flue gases contained in the combustion chamber
• r is a constant equal to the ratio R / M where R is the universal constant of perfect gases and M is the molar mass in kg mol -1 of the mixed gases,
• cpa and cpb are the constant pressure mass heat capacities, respectively, of fresh air and flue gases
• Ta and Tb are the temperatures, respectively, of fresh air and flue gases.
• the invention also relates to a method of estimating the total filling fill_tot supercharged fresh air of a combustion chamber of a cylinder of a motor during a motor cycle, wherein this method comprises estimating a mass Ma of fresh air admitted into the combustion chamber using the above method, estimating a mass Mbal_tot of gas swept (air or flue gas) during the crossing of the valves, and estimating the total filling repl_tot fresh air supercharged from the fresh air mass Ma and the mass Mbal_tot estimated gas swept
• the estimate of the total filling is a solution of the following equation system:
• Mo is an air reference mass under normal conditions of temperature and pressure
• Mb is a mass of burnt gases contained in the combustion chamber at the end of the exhaust of the burned gases
• Mbal_tot is the total mass of swept gas (air or flue gas) during the valve crossing
• Mbal is the mass of gas swept (air) between the intake and the exhaust during the crossing of valves
• Max true and Min true are respectively the functions returning the maximum and the minimum.
• I is the absolute value.
• the invention also relates to an information recording medium comprising instructions for performing one of the above methods, when these instructions are executed by an electronic computer.
• the invention also relates to an estimator of a mass Ma of fresh air admitted inside a combustion chamber of a cylinder of a motor during an engine cycle, in which this estimator comprises a module for estimating a total mass Mtot of gas contained in the combustion chamber at the end of the admission of fresh air, a module for estimating a mass Mb of burnt gases contained in the chamber at the end of the flue gas exhaust, and a module for estimating the mass Ma of fresh air from the difference between the total mass Mtot and the estimated mass Mb of flue gases.
• the invention also relates to a vehicle comprising the estimator above.
• FIG. 1 is a schematic illustration of a vehicle in which the mass Ma and the total fillage fill_tot are estimated;
• FIG. 2 is a graph schematically illustrating movements of the exhaust and intake valves during an engine cycle
• FIG. 3 is a more detailed illustration of the architecture of an electronic calculator implementing an estimator of the mass Ma and of the total fill, fill_tot, and
• FIG. 1 schematically shows a vehicle 2 equipped with an internal combustion engine.
• the vehicle 2 is a motor vehicle such as a car.
• the engine of the vehicle 2 is equipped with several cylinders. However, to simplify the illustration, only a cylinder 6 of this combustion engine is shown in Figure 1. Inside the cylinder 6, a piston 8 is mounted movably in translation between a top dead center (TDC) and a bottom dead center (PMB). This piston 8 rotates a crank 10 of a crankshaft 12 via a connecting rod 14. The crankshaft 12 drives in rotation, through a mechanism (not shown), the driving wheels of the vehicle 2 such that the wheel 16.
• TDC top dead center
• PMB bottom dead center
• the cylinder 6 defines a combustion chamber 18 defined by the upper part of the piston 8 and a cylinder head not shown.
• a fresh air intake duct 20 opens into the chamber 18 through an inlet opening.
• An inlet valve 24 is movable between a closed position in which it closes the intake opening in a fresh airtight manner, and an open position in which fresh air can be admitted into the interior of the chamber. chamber 18 through the intake opening.
• the valve 24 is moved between its open position and its closed position by an actuator 26 of intake valves.
• a fuel injector 28 is provided in the conduit 20 to inject fuel into the fresh air admitted to the interior of the chamber 18.
• the fresh air / fuel mixture starts at occur inside the intake air duct.
• the conduit 20 is fluidly connected to a compressor 30 of a turbocharger 32 adapted to compress the fresh air admitted to the interior of the chamber 18.
• the fresh air thus compressed is called fresh air supercharged.
• a candle 34 clean to ignite the fresh air / fuel mixture opens into the chamber 18. This candle is controlled by an ignition device 36.
• An exhaust duct 40 also opens into the chamber 18 through an exhaust opening.
• This exhaust opening is closable by a valve 44 movable between a closed position, and an open position in which the burnt gases contained inside the chamber 18 can escape via the conduit 40.
• This valve 44 is moved between these open and closed positions by a valve actuator 46.
• the valve actuators 26 and 46 may be mechanical valve actuators.
• the end of the duct 40 opposite its opening which opens into the chamber 18 is fluidly connected to a turbine 48 of the turbocharger 32.
• This turbine 48 allows in particular to relax the exhaust before sending them in a line d exhaust 50.
• the various engine equipment that can be controlled such as the actuators, the ignition device or the fuel injector are connected to a motor control unit 60 also known by the acronym ECU (Engine Control Unit).
• ECU Engine Control Unit
• FIG. 1 the connections between this unit 60 and the various equipment items ordered have not been represented.
• the unit 60 is also connected to many sensors such as for example a sensor 62 of the position of the crankshaft 12 and a sensor 64 of the engine speed.
• the engine speed is defined here as being the number of revolutions per minute performed by the motor drive shaft.
• Figure 2 shows, in the form of a graph, the movements of the valves 24 and 44 relative to the movements of the piston 8 during a motor cycle.
• an axis 70 of the abscissa represents the displacement of the piston 8 between its top dead center and its bottom dead center, noted respectively, PMH and PMB on this graph.
• the y-axis represents the amplitude of the displacement of the intake and exhaust valves. This amplitude is zero when the intake valve or the exhaust valve is closed. It is maximum when these same valves are completely open.
• the displacement of the valve 44 is represented by a curve 72 and the displacement of the valve 24 is represented by a curve 74.
• the axis 70 is graduated in degrees of rotation angle of the crankshaft. The origin of this axis is confused with the top dead center of fresh air intake.
• the exhaust valve begins to open at an angle OE located substantially around the bottom dead center of relaxation and closes at an angle FE.
• the angle FE is located after the top dead center.
• the inlet valve begins to open at an angle OA and closes at an angle FA.
• this graph is represented in the particular case where a valve crossing exists. Indeed, the angle OA precedes the angle FE, which indicates that during a period of time of a few degrees, the intake and exhaust valves are simultaneously open.
• FIG. 3 represents in more detail a possible architecture for the unit 60 for estimating the mass Ma and the total filling rate_tot.
• the unit 60 implements an estimator 80 of a temperature T ECH of the burnt gases, an estimator 82 of a pressure P ECH of the gases, an estimator 84 of a temperature T ADM of the air charge admitted inside the chamber 18 via the conduit 20, and an estimator 86 of a pressure P ADM of the fresh air admitted inside the chamber 18.
• estimators 80, 82, 84 and 86 are connected to an estimator 88 of the mass Ma and the total fill fill_tot.
• This estimator 88 is also connected to a motor control block 90.
• This block 90 makes it possible in particular to control the various actuators, injectors and ignition devices of the engine according to the estimates of the mass Ma and the total fill fill_tot.
• the block 90 is able to adjust the quantity of fuel injected and to advance the ignition timing of the fresh air / fuel mixture injected into the chamber 18 or to adjust the opening of a butterfly valve to adjust the amount of fresh air admitted into the room 18.
• the estimator 88 comprises a module 92 for estimating a mass Mb of burnt gas contained in the chamber 18 at the end of the exhaust of the flue gases, an estimator 94 of a mass Mbal of gas swept from the admission to the exhaust at the crossing of valves, an estimator 96 of the temperature Tb of the flue gases, an estimator 98 of the mass Ma of fresh air admitted into the chamber 18, and an estimator 100 of the total filling repl_tot.
• the module 92 has a submodule 102 for estimating a mass Mb_resi of residual burnt gas contained in the chamber 18 at the end of the exhaust, and a submodule 104 for estimating a mass Mb_reasp of burnt gases sucked off at the crossing of the valves inside the chamber 18.
• modules 92 to 100 will be described in more detail with reference to FIG. 4.
• the unit 60 is typically made from a programmable computer capable of executing instructions stored in an information storage means.
• the unit 60 is connected to a memory 106 containing the various instructions and data necessary for the execution of the method of FIG. 4.
• the various maps used to implement the method of FIG. 4 are recorded in this memory 106. These maps are for example constructed experimentally so as to minimize errors between the estimated values and the real values.
• the general principle is based on a mass balance on an engine cycle of the gas entering and leaving the chamber 18. This mass balance is decomposed into several calculations that take place throughout the engine cycle.
• the mass Mb of flue gases in the chamber 18 is estimated.
• the total mass Mtot of gas contained inside the chamber 18 is estimated. From these two estimates, and because the total mass of gas is preserved on a motor cycle, the mass Ma of air contained inside the chamber 18 during a motor cycle can be obtained by subtraction of the mass Mb to the mass Mtot.
• the mass Ma is given by the following relation: where Mtot is the total mass of gas in chamber 18 at the end of admission, and Mb is the total mass of flue gases in chamber 18 at the end of the exhaust.
• the estimate of the mass Mb is decomposed into an estimate of the mass Mb_resi of residual burnt gases not removed via the leads 40 at the end of the exhaust and mass Mb_reasp of flue gas re-aspirated during the crossing of valves.
• Mb Mb_resi + Mb_reasp
• Mb_resi is the mass of residual burned gas that could not be evacuated during the exhaust.
• Mb_reasp is the mass of burned gas re-sucked at the crossing of valves.
• Total fill_tot is the total amount of fresh air admitted through the intake opening during an engine cycle.
• Mbal the exhaust
• Mbal is the mass of gases swept from the intake to the exhaust during the crossing of valves
• Mo is an air reference mass under normal conditions of temperature and pressure.
• Fresh air filling fill_cyl is defined by the following relationship:
• Mo where Ma is the air mass contained in chamber 18 at the end of admission, and Mo is the reference mass.
• the quantities fill_tot, fill_cyl and the ratio Mbal / Mo are dimensionless quantities.
• the Mbal mass exists only in the case of supercharged engines.
• the description of the process which follows is made in the most complete case, that is to say the case where the estimates of the Mb_reasp and Mbal masses are both carried out.
• the skilled person can easily simplify the process that follows to adapt it only to the case of atmospheric engines or only in the case of supercharged engines.
• the process starts with a step 120 of estimation of the mass Mb_resi of burnt gas contained in the chamber 18 at the end of the exhaust.
• the submodule 102 estimates the mass Mb_resi using the following relation: ⁇ / fU . * cyl FE ⁇ * cyl FE V ⁇ ECff * ⁇ ECH / X ⁇ cyl FE
• r is a constant equal to the following ratio R / M where R is the universal constant of perfect gases and M is the molar mass in kg. mol "1 of flue gases,
• Vcyi FE is the geometric volume of the chamber 18 at the end of the exhaust that is to say for the angle FE.
• V cy ⁇ _ FE The volume V cy ⁇ _ FE is given by the following relation:
• Vcyi FE (FE) - + - ⁇ [+ TO - COs (FE) - ⁇ A 2 Sm 2 (FE))
• the ratio ⁇ and the rate ⁇ are known characteristics of a motor. It is simply recalled here that the ratio ⁇ is the ratio between the length of the rod 14 divided by the half-length of the crank 18.
• the pressures P ECH and PADM and the temperatures TECH and T A DM are the pressures and temperatures estimated by the estimators 80, 82, 84 and 86 from physical magnitudes. measured in the engine.
• the sub-module 104 estimates the Mb_reasp mass of flue gases re-aspired during the crossing of valves.
• this estimate is given by the following relation: , "Mb reasp
• Mb_reasp is the flow rate of re-aspirated burned gases expressed in kg / h
• K is a coefficient making it possible to pass from the flow rate to an admitted mass per engine cycle in the chamber 18.
• N is the engine speed
• Cylinder_number is the engine cylinder number
• Nbre_revolutioncycle is the number of crankshaft revolution during a motor cycle
• 60 is used to convert the N engine speed given in a revolution per minute in number of revolutions per hour.
• Sbase is a predetermined map that gives a first corrective value as a function of the difference between the angles FE and OA and the engine speed
• Scor is a predetermined map which gives a second corrective value as a function of the difference between the angles FE and OA and the engine speed
• - POND is a predetermined mapping that gives a third corrective value depending on the position of the valve crossing and the engine speed.
• ⁇ is the ratio of the heat capacity at constant pressure of the flue gases to the heat capacity at constant volume of the flue gases. For example, this ratio is equal to 1, 4.
• the module 94 estimates the total mass Mbal_tot of gas swept between the intake and the exhaust during the crossing of valves.
• the mass Mbal_tot is obtained using the following relation:
• K is the same coefficient as previously defined for passing from the flow rate to an admitted mass per engine cycle in chamber 18.
• the flow Mbal _tot is estimated from the law of Barrier Saint Venant corrected in the following way to take into account crossover valves:
• S is a predetermined map making it possible to obtain a corrective value as a function of the difference between the angles FE and OA and of the engine speed, and
• - POND is a predetermined map to obtain a corrective value depending on the position of the valve crossing and the engine speed.
• the position of the crossing of valves is equal to the following value: (FE + OA) / 2.
• the module 96 estimates the temperature Tb of the flue gases.
• this temperature Tb is obtained by a calculation of enthalpy mixture between the residual gases and the re-aspirated flue gases.
• the temperature Tb is obtained from the following relation:
• Mb_resi is the mass of residual burned gas previously estimated
• - Mb_reasp is the mass of burned gases re-aspirated at the crossing of valves
• - cpb_reasp is the mass heat capacity at constant pressure of the re-aspirated flue gas
• Tb_reasp is the temperature of the flue gases that have been sucked off during the valve crossover
• Tb_resi is the residual flue gas temperature obtained from an adiabatic expansion calculation.
• the temperature Tb_reasp is taken equal to the temperature TECH.
• the temperature Tb_resi is calculated from the following relation:
• the module 98 estimates the mass Ma by solving the following system of equations:
• Vcyi FA is the geometric volume of the chamber 18 calculated at the angle FA
• a ADM is a correction coefficient
• r is a constant equal to the ratio R / M where R is the universal constant of perfect gases and M is the molar mass in kg. mol "1 of the mixed gases,
• Tmégege is the temperature of the mixture of fresh air and flue gases contained in chamber 18, and cpa and cpb are the constant pressure mass capacities, respectively, of fresh air and flue gases, and
• Ta and Tb are the temperatures, respectively, of fresh air and flue gases.
• the volume V cy ⁇ _ FA is calculated using the following relation:
• the correction coefficient A ADM is obtained using the following relation:
• AADM_ATMO is a corrective value obtained from a predetermined cartography as a function of the angle FA and the engine speed
• AADM_TURBO is a corrective value obtained from a predetermined cartography according to the angel FA and the engine speed
• the coefficient kATMO_TURBO is a corrective coefficient given by the following relation:
• PATMO is the atmospheric pressure
• Po is the reference pressure which is here equal to 1013 mbar
• fA (N, FA) is a corrective value obtained from a predetermined mapping as a function of the engine speed and the angle FA
• fB (N) is a corrective value obtained from a predetermined mapping according to the regime engine.
• the relationship defining the temperature T me iang ⁇ is obtained by a calculation of enthalpy mixture between the mass of burnt gas and the fresh air mass contained in the chamber 18.
• the estimate of the mass Ma is given by the following relation in the particular case where cpb and cpa are equal:
• the estimate of the mass Ma obtained after solving the system of equations is corrected according to the inverse of the temperature Ta of the fresh air.
• the mass Ma is corrected using the following relation:
• f (1 / Ta) is a correction coefficient whose value is obtained from a prerecorded cartography giving the value of this correction coefficient as a function of the inverse of the temperature Ta.
• the module 100 estimates the total filling repl_tot fresh air.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Combined Controls Of Internal Combustion Engines (AREA)

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• 2009
  • 2009-02-23 FR FR0951133A patent/FR2942503B1/fr active Active
• 2010
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