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
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
• • 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
  • F02D41/021—Introducing corrections for particular conditions exterior to the engine
  • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
  • F02D41/0295—Control according to the amount of oxygen that is stored on the exhaust gas treating apparatus
• • 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
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
  • F02D41/1439—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the position of the sensor
  • F02D41/1441—Plural sensors
• • 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
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
  • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
  • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
• • 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
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
  • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
  • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
  • F02D41/1456—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio with sensor output signal being linear or quasi-linear with the concentration of oxygen
• • 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
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
  • F02D41/1473—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation method
  • F02D41/1475—Regulating the air fuel ratio at a value other than stoichiometry
• • 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
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
  • F02D41/1493—Details
• • 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
  • F02D41/182—Circuit arrangements for generating control signals by measuring intake air flow for the control of a fuel injection device
• • 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
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
  • F02D2041/1413—Controller structures or design
  • F02D2041/1418—Several control loops, either as alternatives or simultaneous
  • F02D2041/1419—Several control loops, either as alternatives or simultaneous the control loops being cascaded, i.e. being placed in series or nested
• • 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
  • F02D2200/06—Fuel or fuel supply system parameters
  • F02D2200/0614—Actual fuel mass or fuel injection amount
• • 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
  • F02D2200/08—Exhaust gas treatment apparatus parameters
  • F02D2200/0802—Temperature of the exhaust gas treatment apparatus
• • 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
  • F02D2200/08—Exhaust gas treatment apparatus parameters
  • F02D2200/0814—Oxygen storage amount
• • 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
  • F02D2200/08—Exhaust gas treatment apparatus parameters
  • F02D2200/0816—Oxygen storage capacity

Definitions

• TITLE PROCESS FOR ADJUSTING THE RICHNESS OF AN INTERNAL COMBUSTION ENGINE WITH CONTROL IGNITION
• the present invention relates to a method for adjusting the richness of an internal combustion engine. It relates more precisely to a method for adjusting the richness of the air-fuel mixture in an engine of the spark-ignition type, in which the quantity of oxygen stored in a three-way catalyst is adjusted in a closed loop, to a set value. of the motor.
• the adjustment of the richness that is to say the adjustment of the ratio between the quantity of fuel injected and the quantity of air admitted into the engine, reduced to stoichiometric proportions, is intended to control the richness of the mixture to a setpoint richness which can be variable according to the operating conditions of the engine, in particular the speed and the load.
• the ignition and the fuel injection are often controlled electronically by an engine computer in order to operate conventionally at richness 1 on most vehicles.
• operating points that is to say in stoichiometric proportions, according to which the quantity of oxygen contained in the air-fuel mixture is exactly equal to the quantity theoretically necessary for the fuel to be completely burnt.
• a three-way catalyst is generally fitted to the engine exhaust to ensure the treatment of the engine combustion gases before they are evacuated into the outside atmosphere.
• Such a catalyst makes it possible to oxidize at least part of the unburnt hydrocarbons (HC) and carbon monoxide (CO), and to reduce at least part of the nitrogen oxides (NOx) which are emitted in the gases of engine combustion.
• the efficiency of the catalyst can be defined as the efficiency of the reaction for treating pollutants in gases (HC, CO, NOx).
• a well-known example of a richness adjustment method consists in providing a control loop comprising an oxygen sensor mounted upstream of the catalyst (in the direction of gas flow).
• An output signal from the sensor generally a voltage, which is representative of the richness, is subtracted from a setpoint value, which corresponds to a richness value equal to 1.
• the error signal equal to the difference between the setpoint voltage and the measured voltage, is then compared in a binary comparator.
• the air-fuel mixture is enriched using a regulator, generally of the proportional-integral (PI) type, which receives the error signal as input and which delivers at the output, a fuel injection duration correction to be added to a base injection duration, to determine the fuel injection duration to be applied in order to obtain the richness of the mixture to be introduced into the engine, taking into account the amount of air.
• PI proportional-integral
• the basic injection duration is increased by a proportional term and an integral term.
• publication FR-A1 -3033364 discloses a method for adjusting the richness of the air-fuel mixture in an internal combustion engine, with ignition and fuel injection controlled by a computer, and associated with an exhaust catalyst. , the method comprising:
• step of regulating the quantity of oxygen stored according to the oxygen stock setpoint which delivers, as a function of the difference between the quantity of oxygen stored and the oxygen stock setpoint, a correction value richness setpoint to be added to a stoichiometric base richness setpoint to determine a richness setpoint value, and,
• a richness regulation step determined from the probe, according to the richness setpoint value, which delivers, according to the difference between the richness determined from the probe and the richness setpoint value, a fuel injection duration correction to be added to a base injection duration, to determine the fuel injection duration to be applied in order to obtain the richness of the mixture to be introduced into the engine.
• the oxygen stock setpoint is equal to a percentage of the oxygen storage capacity, for example 70%.
• FR-A1 -3033364 it is planned to determine the oxygen storage capacity of the engine (or OSC, from the acronym for: Oxygen Storage Capacity) after each engine start, causing a transition from a lean operating mode with zero richness corresponding to an injection cut-off which saturates the catalyst with oxygen, to an operating mode with a richness strictly greater than 1 which makes it possible to empty the catalyst of its oxygen.
• OSC oxygen Storage Capacity
• the OSC oxygen storage capacity is calculated as a time integral of the product of the exhaust gas flow rate; the level of oxygen in the air; and, by a factor which is equal to 1 minus the value of the richness measured by the upstream probe.
• the integral calculation begins when the signal from an oxygen sensor downstream of the catalyst switches to a low value, indicating the start of saturation of the catalyst with oxygen, and ends when the signal from the oxygen sensor downstream to a high value, indicating the approach of the catalyst oxygen drain.
• This calculation of the oxygen storage capacity makes it possible to update the OSC value taking into account the aging of the catalyst and any failures, but it is not updated between two engine starts, and therefore does not take into account.
• the oxygen stock setpoint which is equal to 70% of this predetermined OSC value during the previous start of the engine, therefore remains fixed between two starts and does not allow optimal treatment of the pollutants when the operating point of the engine evolves during a journey of the vehicle.
• the adjustment method according to this publication also has another precision defect, more precisely adjustment drift, linked to the determination and to the reinitialization of the OS.
• the current value of the quantity of oxygen stored in the OS catalyst is calculated as the sum of an initial value and a time integral of the flow rate of the exhaust gases, of the rate of oxygen in the air , and a factor which is equal to 1 minus the value of the richness measured by the upstream probe.
• the initial value is for example equal to the value of the OSC calculated after starting the engine as indicated above, or the previous value of OSC which was determined.
• the calculation integral of each current value of the OS then begins at this initialization moment and ends at each current instant.
• the integral calculus is performed iteratively by time step.
• a value which is equal to the product of the exhaust gas flow rate at the previous instant, of the mass rate of oxygen in the air by a factor which is equal to 1 minus the richness value measured by the upstream probe at the previous instant , and the time step.
• the calculation thus carried out presents a risk of deviating more or less rapidly from the real value of the quantity of oxygen stored: in fact, on the one hand, the calculation errors and rounding accumulate, and on the other hand, the upstream oxygen sensor can give slightly erroneous measurements (measurement of a richness too rich or too poor compared to reality).
• the richness adjustment being made on the basis of an error signal equal to the difference between the oxygen stock setpoint and the calculated value of the quantity of oxygen stored, an incorrect calculation of this quantity has the effect of to distort the richness adjustment.
• the oxygen storage capacity OSC is considered to be constant, and it is also indicated that the calculation of the storage capacity OSC oxygen can advantageously be continuously updated by an adaptation method, which preferably takes place using a downstream oxygen sensor which indicates that the catalyst is full or empty of oxygen. It will be understood that this is a method very similar to that which is disclosed in the publication FR-A1 -3033364. There are also no plans to update continuously updates the OSC value based on current engine operating conditions.
• the present invention aims to remedy these shortcomings of the known methods of adjusting the richness of the air-fuel mixture in spark-ignition engines, in which the quantity of oxygen stored is regulated around an oxygen stock setpoint.
• a device for adjusting the richness of the air-fuel mixture in an internal combustion engine, with ignition and injection controlled by a computer comprising a first servo loop comprising:
• a first richness regulator calculated from said upstream sensor according to a richness setpoint, which delivers a correction to be added to a basic fuel injection duration to obtain the fuel injection duration to be applied in order to obtain the richness of the mixture to be introduced into the engine;
• the device further comprising a second servo loop which slaves the richness setpoint of the first servo loop to the regulation of the quantity of oxygen stored in the catalyst, said second loop comprising:
• a second regulator for regulating said quantity of oxygen stored according to an oxygen stock setpoint, which delivers a richness setpoint correction to be added to a stoichiometric base richness setpoint to obtain said richness setpoint.
• the main characteristic of the device according to the invention is that it further comprises: means for determining the flow rate of the exhaust gases passing through the catalyst;
• the invention also proposes a method for adjusting the richness of the air-fuel mixture in an internal combustion engine, with ignition and injection controlled by a computer, and associated with an exhaust catalyst, comprising:
• a step of regulating said quantity of oxygen stored according to said oxygen stock setpoint which delivers a richness setpoint correction to be added to a stoichiometric base richness setpoint to obtain said richness setpoint.
• the main characteristic of the method according to the invention is that it further comprises: a step during which the flow rate of the exhaust gases passing through the catalyst is determined;
• a minimum threshold for the quantity of oxygen and a maximum threshold for the quantity of oxygen is determined as a function of said flow rate and of said temperature, corresponding respectively to the start of carbon monoxide leaks and to a start nitrogen oxides leaks downstream of the catalyst;
• FIG. 1 is a schematic view of a motorization device suitable for implementing the method according to the invention.
• FIG. 2 is a schematic view of the three-way catalyst of FIG. 1 associated with upstream and downstream oxygen sensors.
• FIG. 3 is a view which schematically shows a richness adjustment device according to the invention.
• FIG. 4 is a flowchart of the steps of an embodiment of the method according to the invention.
• a motorization device 1 suitable for implementing the method according to the invention.
• the device comprises an internal combustion engine 2 of the type with controlled ignition (operating in particular on gasoline), for example with direct injection, by means of fuel injectors (not shown) capable of injecting the fuel into the various cylinders of the engine. .
• the engine can be a naturally aspirated or supercharged engine. It may also have other features that are not shown, such as being associated with at least one circuit for partial recirculation of the exhaust gases at the intake, without harming the generality of the invention.
• the engine is in the form of a four-cylinder in-line engine.
• the engine draws air from the outside atmosphere, which enters an air intake circuit of the engine in the direction of arrow A.
• the quantity (mass flow) of air Qair entering the engine is metered by means of a valve 4, or throttle body 4, of the engine.
• the air intake circuit comprises means 5 for determining the quantity of air admitted into the engine, which are here in the form of a flowmeter 5.
• filling efficiency is understood in a known manner the ratio of the quantity of air which actually enters the cylinders of the engine, divided by the quantity of air which can theoretically enter them.
• the combustion gases of the engine are evacuated into the external atmosphere via an exhaust circuit 7 of the engine, in the direction of arrow G.
• the exhaust circuit comprises a three-way catalyst (or TWC for : Three Way Catalyst) which is able to treat a certain proportion of the polluting molecules of carbon monoxide (CO), unburned hydrocarbons (HC) and nitrogen oxides (NOx) contained in the combustion gases of the engine, before they are released into the outside atmosphere.
• the exhaust circuit may include additional pollution control devices not shown, for example a particulate filter, which do not come within the scope of the invention.
• the catalyst 8 is associated, for adjusting the richness of the air-fuel mixture admitted into the engine according to the invention, with an upstream oxygen sensor 9, that is to say an oxygen sensor mounted at the inlet. of the catalyst, in the direction of flow of the combustion gases, and to a downstream oxygen sensor 10, that is to say to an oxygen sensor mounted at the outlet of the catalyst, in the direction of flow of the combustion gases .
• the upstream oxygen probe 9 is of the proportional type and the downstream oxygen probe 10 is of the binary type (without however excluding the possibility of a proportional probe, such a probe not nevertheless being essential for the implementation of the invention).
• the motorization device comprises means for determining a value of the temperature Tcat of the catalyst, and means for determining a value of the temperature T'A of the downstream oxygen sensor 10.
• the means for determining the temperature of the catalyst Tcat can be in a simplified mode in the form of an upstream temperature sensor 11 of the catalyst, or of a downstream temperature sensor 12 of the catalyst, or of both.
• An electronic engine control system 13, or computer 13 makes it possible to determine a quantity (flow) of fuel Qcarb to be injected into the engine so that the richness of the mixture is closest to a given richness setpoint value. It is also possible for the computer 13 to determine an injection time T, of the fuel which corresponds to the quantity Qcarb to be injected.
• the computer 13 is connected, in the example of FIG. 1, at least to the flowmeter 5 and to the upstream oxygen sensor 9.
• the flowmeter indicates the quantity of fuel and the upstream oxygen sensor 9, which is a sensor. of proportional type, provides a measure of the richness RA upstream of the catalyst via an output signal which is generally a voltage value UA.
• the computer is also connected to the downstream oxygen probe 10, which may be in the form of a binary probe (without excluding the possibility of a probe proportional), to the means for determining the temperature of the catalyst Tcat (ie for example to the upstream 11 and / or downstream 12 temperature sensor in the example of the figure), and to the means for determining the temperature of the oxygen sensor downstream T'A (ie to the downstream temperature sensor 12 in the example of the figure).
• the downstream oxygen probe 10 may be in the form of a binary probe (without excluding the possibility of a probe proportional)
• the means for determining the temperature of the catalyst Tcat ie for example to the upstream 11 and / or downstream 12 temperature sensor in the example of the figure
• T'A ie to the downstream temperature sensor 12 in the example of the figure
• FIG. 2 represents in an enlarged manner the catalyst 8 of FIG. 1 associated with the upstream oxygen sensor 9 and the downstream oxygen sensor 10, on which the oxygen storage capacity, or OSC, has been shown schematically.
• OSC oxygen storage capacity
• the oxygen storage capacity OSC can be advantageously determined and updated regularly after each start of the engine 2, on a point of flow rate of the exhaust gases Qech and of catalyst temperature Tcat corresponding to a particular operating cycle of the engine carried out. after starting the engine, which is described below, in order to determine an aging factor V or degradation of the catalyst.
• the term aging factor is understood here to mean the residual percentage of the oxygen storage capacity of the catalyst in new condition and in perfect condition OSCnew, which the catalyst retains at a given time, for the same gas flow point of Qech exhaust and Tcat catalyst temperature. According to a simplified calculation, the following formula can be applied:
• a very worn catalyst such as a catalyst which is used to characterize the on-board diagnostic thresholds called OBD diagnostic (from the acronym for: On Board Diagnostic) has a capacity non-zero residual oxygen storage OSCobd, for example of the order of a tenth of the value of a new catalyst under the same conditions.
• OBD diagnostic from the acronym for: On Board Diagnostic
• OSCobd capacity non-zero residual oxygen storage
• OSC - OSCobd V x (OSCnew - OSCobd)
• the engine control unit can in particular take advantage of the first occurrence of a long enough lift of the foot from the accelerator pedal by the driver, after starting the engine, to cause an operating cycle.
• forced operation of the engine consisting in causing a transition from an operating mode with zero richness to an operating mode with strictly higher richness than IPIus precisely, initially, the operation of the engine with zero richness, corresponding to a cut in fuel injection, saturates the catalyst 8 with oxygen, as long as the foot lift is sufficiently long.
• the computer applies a richness level strictly greater than 1 when restarting after injection cut-off; for example, a richness equal to 1.05, so as to let the catalyst 8 gradually empty of its oxygen, until the downstream binary probe 10 switches above a precalibrated voltage threshold U’A.
• OSC JAt Qech x (1 -RA) x T02 x dt
• RA denotes the richness upstream of the catalyst, corresponding to the measurement of the voltage LIA of the upstream probe
• T02 denotes the level of oxygen in the air, for example 21%.
• the current value of the amount of oxygen present in the catalyst can be calculated by a similar formula:
• OS OSinit + JAt Qech x (1 -RA) x T02 x dt
• OSinit designates a known initial value of the quantity of oxygen
• At designates the time interval separating the instant of initialization from the current instant.
• initial value it may be, for example according to the state of the art, either the OSC calculated as indicated above after lifting the foot long enough to saturate the catalyst with oxygen, or a zero value after adjusting the engine to a rich mixture long enough to empty the catalyst of its oxygen. This latter scenario may arise in particular under conditions of full engine load, for which it is known practice to limit the temperature at the exhaust by adjusting the richness in open loop to a richness setpoint strictly greater than 1.
• L ' The invention provides additional advantageous reset modes, which will be explained below.
• FIG. 3 schematically shows a richness adjustment device according to the invention, suitable for implementing the method according to the invention in accordance with FIG. 4.
• the invention is based on the observation that, when a catalyst is characterized with a binary probe downstream of said catalyst, the maximum efficiency of said catalyst is retained as long as a richness of the exhaust gases is strictly equal to 1 to downstream of the R'A catalyst is respected. When this condition is not met, the efficiency drops until it reaches zero. The engine should therefore be operated in such a way as to remain outside these so-called “leak” operating zones.
• the aim of the invention is to ensure that the richness of the engine is adjusted such that the OS of the catalyst remains within the range between the lower OSmin and upper OSmax thresholds for the amount of oxygen.
• OSc OSmin + K x (OSmax - Osmin)
• K is a coefficient strictly between 0 and 1 and preferably between 0.25 and 0.75.
• K 0.5 can be taken, which corresponds to an identical risk-taking with regard to CO or NOx leaks.
• a value K will be taken substantially equal to 0.3. Regulating the richness of the engine will then tend to slightly favor the adjustment of the engine in rich mixture and to reduce the quantities of oxygen stored OS, which corresponds to a risk of NOx leaks less than the risk of CO leaks.
• a first map is established, the inputs of which are the flow rate of the gases Qech and the temperature of the catalyst Tcat and the output of which is the minimum threshold of quantity of oxygen of a new catalyst OSmin, new, and a second map is established, the inputs of which are identical and the output of which is the maximum threshold OSmax, nine of the quantity of oxygen of a new catalyst.
• These maps are established on the basis of a new catalyst in perfect condition, whose oxygen storage capacity OSCnew is known. The two maps are stored in a computer memory.
• each value of said minimum threshold OSmin, nine (Qech, Tcat) is associated with a table of maximum voltage threshold values U'max depending on the temperature of the probe T'A and on the flow rate Qech.
• each value deduces threshold maximum OSmax, nine (Qech, Tcat) is associated with a table of minimum voltage threshold values U'max depending on the temperature of the T'A probe and the flow rate Qech.
• the adjustment device comprises a simple servo loop, comprising the upstream oxygen sensor 9 of the proportional type, intended for measuring the oxygen concentration of the exhaust gases from the upstream engine. catalyst 8.
• This upstream probe 9 delivers a voltage signal LIA corresponding to a richness value RA.
• This richness RA is compared with a richness setpoint CA in a comparator 14 which delivers the difference e1 between the richness RA estimated from the measured voltage LIA and the richness setpoint CA to follow.
• This simple loop also includes a richness regulator 15, for example of the proportional-integral (“PI”) type which receives as input the value of the difference e1 and which provides at output the correction Te to be added to a duration of.
• PI proportional-integral
• each quantity of fuel is determined from an air quantity value Qair, for example measured by the flowmeter 5.
• the device comprises a second servo loop comprising: the upstream oxygen sensor 9; means 17 for calculating the quantity of oxygen OS stored in the catalyst 8; comparison means 18 between said quantity of stored oxygen OS and an OSc oxygen stock setpoint; a second regulator 19, which is a regulator of the amount of oxygen stored; a second adder 20.
• the richness setpoint CA of the single loop is delivered by the second adder 20.
• the latter adds a basic richness setpoint, equal to 1, to a correction of the richness setpoint cA which is delivered by the second regulator 19 from the difference e2 between, on the one hand, the value of the quantity of oxygen stored OS in the catalyst, delivered by the calculation means 17, and on the other hand, the oxygen stock set point OSc, which is delivered by means specific to the invention which are detailed below.
• Said setpoint OSc is subtracted from said quantity stored OS in comparator 18 which delivers said difference z2 to the second regulator 19
• the second adder 20 supplies the richness setpoint value CA of the single loop as output.
• the second regulator 19 is for example of the proportional-integral type. As a variant, it may have a transfer function such as that which is described in publication FR-A1 -3033364. More precisely, outside a range of deviation e2 comprising the value 0, the richness setpoint correction cA is saturated at a constant negative value below the deviation range and at a constant positive value above the range of deviation; within the range of deviation, the setpoint correction cA is a continuous function, increasing and refining by parts of the deviation e2.
• the device comprises means 21 for determining the flow rate Qech of the exhaust gases, for example means which calculate the exhaust flow rate Qech as the sum of the intake air flow rate Qair and the fuel flow rate Qcarb ; means 11, 12 for determining the temperature of the catalyst Tcat; means 22 for determining a minimum threshold of quantity of oxygen OSmin and a maximum threshold of quantity of oxygen OSmax from said flow rate Qech and from said temperature Tact, and means 23 for calculating the quantity setpoint of oxygen OSc from said minimum and maximum thresholds OSmin, OSmax.
• the exhaust gas flow rate is obtained as the sum of the air flow Qair measured by the air flow meter 5 and the fuel flow corresponding to the fuel injection time Ti.
• the minimum and maximum threshold values OSmin, OSmax are deduced, for a flow rate Qech and a temperature Tcat given, from the minimum and maximum threshold values for the quantity of oxygen of the new catalyst OSmin, new, OSmax, new stored respectively in the first and in the second maps, by respectively multiplying said values by the aging factor V determined after starting the vehicle (or during the previous journey if we have not yet recalculated and updated the value of l 'OSC).
• OSc OSmin + K x (OSmax - OSmin)
• the coefficient K is strictly between 0 and 1, preferably between 0.25 and 0.75, for example substantially equal to 0.3.
• the adjustment device further comprises means for resetting the value of the quantity of stored oxygen OS calculated by the calculation means 17. It comprises the downstream oxygen sensor 10, which delivers a signal of voltage U'A, the means 12 for determining the temperature of the probe T'A and the means for determining the flow rate Qech of the exhaust gases 21. It comprises means for comparing the voltage signal U'A with the threshold minimum voltage U'min and with the maximum voltage threshold U'max, which depend on the exhaust flow rate and the temperature of the T'A probe.
• the calculation of the OS continues by the classical integral calculation method which was discussed above. However, if the voltage reaches the minimum voltage threshold U’min, the OS calculation is immediately reset to a value equal to the maximum oxygen quantity threshold OSmax, regardless of the result of the integral calculation. Likewise, if the voltage reaches the maximum voltage threshold U’max, the OS calculation is immediately reset to a value equal to the minimum oxygen quantity threshold OSmin, regardless of the result of the integral calculation.
• the OS equals the oxygen storage capacity OSC.
• the closed-loop richness control is immediately put into operation on the setpoint coming from the setpoint calculation means 23, and the OS decreases without falling below the minimum oxygen quantity threshold OSmin, nor then rising above the maximum oxygen quantity threshold OSmax, if the regulation works with normal speed.
• this reset does not exclude the possibility of also resetting the calculation of the OS to the value of the oxygen storage capacity OSC after a fairly long lifting of the foot, or to the zero value after a sufficiently deep foot. long. It should also be noted that, in the event that the minimum threshold OSmin or the maximum threshold OSmax is reached periodically after each reset of the calculation, even though the motor is operating at a stabilized operating point and the setpoint of oxygen stock OSc is constant, a bias could be added or subtracted systematically to the richness signal RA from the upstream probe.
• FIG. 4 illustrates the steps of the method according to the invention.
• the method comprises an initialization step 100, in which the engine is started, the relative data with the new catalyst being stored in the computer: oxygen storage capacity of the new OSCnew catalyst; first and second maps of minimum and maximum oxygen quantity thresholds of the new catalyst OSmin, new, OSmax, new; tables of associated maximum and minimum voltage U'max, U'min thresholds.
• the method itself continues with a step 200 for determining the current value of the oxygen storage capacity OSC, which occurs as soon as possible after starting the engine, during the first lifting of the foot by the driver of the vehicle, then by a step of calculating the aging factor V. It then continues with a step of updating the first and second mapping, in which the aging factor V is applied. At this step, the OSc oxygen stock setpoint.
• the method then comprises a series of iterative steps 400 to 1500.
• step 400 the voltage LIA delivered by the upstream probe 9 is measured and a value for the upstream richness RA is deduced.
• step 500 the voltage U'A delivered by the downstream probe 10 is measured.
• step 600 the value of the exhaust flow rate Qech, of the temperature of the downstream probe T'A and of the catalyst temperature Tcat.
• step 700 the respective values of the minimum voltage threshold U’min and the maximum voltage threshold U’max corresponding to the flow rate Qech and temperature values of the downstream probe T’A are deduced.
• the method continues with a first test step 800 in which said voltage U'A is compared with the maximum voltage threshold U'max. As long as said voltage is strictly below said threshold, the method directs towards a second test step 900. Otherwise, that is to say as soon as said voltage becomes greater than or equal to said threshold, the calculated value of the OS is reinitialized. to the minimum threshold value of oxygen quantity OSmin (step 1000).
• said voltage I l is compared with the minimum voltage threshold U'min.
• the method directs towards a step of integral calculation 1100 of the quantity of oxygen stored as explained above. Otherwise, that is to say as soon as said voltage becomes less than or equal to said threshold, the calculated value of the OS is reset to the maximum threshold value of the quantity of oxygen OSmax (step 1200).
• the method continues with a step of determining 1300 the OSc oxygen stock setpoint corresponding to the value of the exhaust gas flow rate Qech and the temperature of the catalyst Tcat.
• step 1400 the value of the error e2 is calculated between the calculated value of the OS resulting from the integral calculation step 1100, or where appropriate from one of the reset steps 1000, 1200, and the OSc setpoint.
• step 1500 the value of the richness set point correction cA to be added to the stoichiometric value is determined to obtain the richness set point value CA to be adjusted in a closed loop.
• step 1600 the fuel injection time correction value Te to be added to a basic fuel injection time ti (which corresponds to the stoichiometric richness) is determined in order to obtain a total injection time of Ti fuel in the engine.
• the method ends (step 1700) when the engine is stopped.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Exhaust Gas After Treatment (AREA)
• Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

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• 2019
  • 2019-09-19 FR FR1910314A patent/FR3101110B1/fr active Active
• 2020
  • 2020-09-08 WO PCT/EP2020/075016 patent/WO2021052808A1/fr unknown
  • 2020-09-08 EP EP20765302.3A patent/EP4031759A1/de active Pending

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