CN107917005B - Method and control device for regulating the oxygen filling of a three-way catalytic converter - Google Patents

Method and control device for regulating the oxygen filling of a three-way catalytic converter Download PDF

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CN107917005B
CN107917005B CN201710934463.9A CN201710934463A CN107917005B CN 107917005 B CN107917005 B CN 107917005B CN 201710934463 A CN201710934463 A CN 201710934463A CN 107917005 B CN107917005 B CN 107917005B
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way catalyst
oxygen
jump
exhaust gas
sensor
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CN107917005A (en
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M.法伊
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Robert Bosch GmbH
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Robert Bosch GmbH
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F01N11/007—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/101—Three-way catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N9/00—Electrical control of 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
    • 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
    • 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
    • F02D41/14—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
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
    • F01N2560/025—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting O2, e.g. lambda sensors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
    • F01N2900/1624—Catalyst oxygen storage capacity
    • 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
    • F02D2041/1433—Introducing closed-loop corrections characterised by the control or regulation method using a model or simulation of the system
    • 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

Abstract

The invention relates to a method for regulating the oxygen charge of a three-way catalyst in an exhaust gas channel of an internal combustion engine, wherein the oxygen content of the exhaust gas upstream of the three-way catalyst is determined using a first skip lambda sensor, wherein tolerance effects and aging effects, which lead to a deviation of the actual sensor characteristic from a reference sensor characteristic, are taken into account and corrected, wherein the oxygen charge of the three-way catalyst is modeled. And also to a control device for carrying out said method. According to the invention, the oxygen intake into the three-way catalytic converter and/or the oxygen exhaust from the three-way catalytic converter is determined from the corrected output signal of the first jump lambda sensor, and the oxygen filling of the three-way catalytic converter is modeled. By modeling the filling of the three-way catalyst, its filling level can be set such that it can also be operated in its optimum conversion capacity range during the dynamically occurring lean or rich phase due to its oxygen storage capacity.

Description

Method and control device for regulating the oxygen charge of a three-way catalyst
Technical Field
The invention relates to a method for regulating the oxygen charge of a three-way catalyst in an exhaust gas channel of an internal combustion engine, which channel guides the exhaust gas, wherein the oxygen content of the exhaust gas upstream of the three-way catalyst is determined using a first skip Lambda (Lambda) sensor, wherein tolerance effects and aging effects, which lead to a deviation of the actual sensor characteristic curve from a reference sensor characteristic curve, are taken into account and corrected, and wherein the oxygen charge of the three-way catalyst is modeled.
Background
The invention further relates to a control device for regulating the oxygen filling of a three-way catalyst in an exhaust gas channel of an internal combustion engine, which channel guides the exhaust gas, wherein a first jump-lambda sensor is provided for determining the oxygen content of the exhaust gas upstream of the three-way catalyst, wherein a voltage offset in the output signal of the first jump-lambda sensor is identified and corrected, wherein an offset of a point of the sensor characteristic curve at lambda =1 and a temperature-induced offset are corrected, wherein a lateral sensitivity (Querempfindlichkeit) of the first jump-lambda sensor with respect to the exhaust gas constituents is taken into account, and wherein a model for modeling the oxygen filling of the three-way catalyst is provided in the control device.
In the event of incomplete combustion of the air-fuel mixture in the internal combustion engine, nitrogen (N) is excluded2) Carbon dioxide (CO)2) And water (H)2O), a large amount of combustion products, among which Hydrocarbons (HC), carbon monoxide (CO), and Nitrogen Oxides (NO), are dischargedX) Are legally restricted. According to the state of the art, exhaust gas limits for motor vehicles can be met using only catalytic exhaust gas aftertreatment. By using a three-way catalyst in an exhaust passage of an internal combustion engine, the proposed harmful components can be converted into nitrogen, carbon dioxide, and water.
For three-way catalysts, for HC, CO and NOXThe simultaneously high conversion is achieved only in a narrow lambda range (so-called catalyst window) around the stoichiometric operating point (lambda = 1). Only here is there a balance between the oxygen requirement for oxidation of HC and CO and the presence of NOXThe balance between oxygen supplies generated by the reduction. In order to operate the catalyst in the catalyst window, a lambda controller is typically used in current engine control systems, which lambda controller is based on the signals of the lambda sensors before and after the three-way catalyst. In order to regulate the lambda value upstream of the catalyst, the oxygen content of the exhaust gas upstream of the catalyst is measured using the lambda sensor. Based on this measurement, the regulator corrects the fuel quantity from the pre-controller. For more precise control, the exhaust gas after the catalytic converter is additionally analyzed using a further lambda sensor. This signal is used for a pilot control which is superimposed on the lambda control upstream of the catalytic converter. Typically, a jump-lambda sensor is used as lambda sensor after the catalystThe sensor, the jump- λ sensor, has a very steep characteristic curve at λ =1, and, therefore, is able to display λ =1 very accurately.
Current regulation designs have disadvantages: they can detect the exit of the catalyst window later by means of the signal of the jump lambda sensor downstream of the catalyst. An alternative to the regulation of the three-way catalyst based on the signal of the lambda sensor after the catalyst is to regulate the oxygen filling level of the catalyst. In the catalysts currently used, the cerium oxide (Ceroxid) is located on a porous support material of the catalyst, which can be present in different oxidation stages, depending on the oxygen occlusion (sauerstofvorkommen). Oxidation of the oxygen storage material occurs during lean operation of the engine, and this is again reduced during rich operation. In this way, the oxygen excess or oxygen deficiency in the exhaust gas mixture can be completely or partially compensated depending on the oxygen storage capacity and the current oxygen charge of the catalyst, which leads to a significantly improved conversion performance of the catalyst with regard to non-stoichiometric exhaust gas compositions. Thus, the adjustment of the oxygen filling of the three-way catalyst leads to an increased cleaning performance.
Since the oxygen-filling or oxygen-filling level of the three-way catalyst cannot be measured, these quantities are modeled. For the modeling of the filling level, a measurement of the exhaust gas λ upstream of the catalyst in a wide range around λ =1 is necessary. Therefore, broadband sensors are usually used in front of the catalytic converter.
DE102013017260B3 discloses a method for operating a drive (1) having an internal combustion engine and a catalytic converter (3) for cleaning the exhaust gases of the internal combustion engine, wherein a first lambda sensor (5) is arranged upstream of the catalytic converter (3) and a second lambda sensor (6) is arranged downstream of the catalytic converter (3), which first lambda sensor provides a first lambda signal and which second lambda sensor provides a second lambda signal, and wherein a lambda-induced regulation is performed by means of the first lambda signal and a lambda-trim regulation (lambdatrimminregenging) is performed by means of the second lambda signal, which lambda trim regulation is superimposed on the lambda-induced regulation. In this case, a regulator (7) and an observer (8) who models the catalyst (3) are used for the lambda fine-tuning control, wherein a setpoint value and a model error obtained by means of the observer (8) are supplied as input variables to the regulator (7), and a control variable obtained by means of the regulator (7) is supplied as input variables to the observer (8). The invention further relates to a drive device (1).
Document DE102006061684a1 discloses a method for adjusting the oxygen filling level of an exhaust gas cleaning device of an internal combustion engine, wherein the exhaust gas composition is measured in the exhaust gas flow direction before the exhaust gas cleaning device by means of a first exhaust gas probe and after the exhaust gas cleaning device by means of a second exhaust gas probe, wherein the oxygen intake (Sauerstoff-Eintrag) into the exhaust gas cleaning device is determined and added or integrated to the oxygen quantity, and wherein the exhaust gas composition before the exhaust gas cleaning device is modulated between predetermined limit values (moduleren). According to the invention, the exhaust gas composition upstream of the exhaust gas cleaning device (16) is modulated in such a way that the lean control of the exhaust gas composition is ended when the oxygen quantity reaches a predetermined upper limit value and the rich control is ended when the oxygen quantity reaches a predetermined lower limit value.
Document DE010339063Al describes a method for mixture control in an internal combustion engine using a catalytic converter, which is arranged in an exhaust gas system of the internal combustion engine and has an oxygen storage capacity, and an oxygen sensor arranged downstream of the catalytic converter, wherein a model of the oxygen storage capacity is provided, which calculates a value of an oxygen charge of the catalytic converter as a function of an input lambda value and a catalytic converter parameter value. Is provided with: depending on the oxygen charge and the calculated value of the rich or lean cut (Fett-oder Magerdurchbruch) at the catalytic converter, which is detected by means of the oxygen sensor, a mixture change is initiated. In DE010339063Al, the modeling of the oxygen filling level of the catalyst is provided without using the corrected output signal of the jump lambda sensor in front of the catalyst.
Document DE102014211941Al describes a method for evaluating a lambda signal (lam _ 2) which is provided by a lambda sensor (18) using a characteristic curve in the form of a jump, said lambda sensor being arranged downstream of a catalytic converter (14) which is arranged in an exhaust gas duct (12) of an internal combustion engine (10). According to the invention, the lambda signal (lam _ 2) is differentiated, the absolute value of the differentiated signal (36) is formed, a quantity signal (40) of the differentiated signal (36) is integrated over a period of time, the integration result (44) is compared with an integration threshold value (I _ SW), and when the threshold value is exceeded, the fuel fraction of an air-fuel mixture is increased, and the air-fuel mixture is supplied to the internal combustion engine (10). In document E102014211941a1, a jump sensor is arranged behind the catalyst, the signal of which is evaluated in an improved manner.
DE102012211687Al discloses a method for detecting a voltage offset, which is a voltage offset at least in the range of a voltage λ characteristic curve of a jump λ sensor arranged in an exhaust gas duct of an internal combustion engine relative to a reference voltage λ characteristic curve of the jump λ sensor, wherein the jump λ sensor is a component for setting a control path for an air/fuel mixture supplied to the internal combustion engine, wherein a deviation of the voltage λ characteristic curve from the reference voltage λ characteristic curve with λ =1 is corrected, wherein starting from a value pair to be detected on the reference voltage λ characteristic curve with λ to be detected and voltage to be detected, a change in the composition of the air/fuel mixture supplied to the internal combustion engine is carried out toward λ =1, and the actual value of λ is inferred from the change in the composition of the air/fuel mixture up to λ = 1. According to the invention, it is provided that the delay time of the control path is determined in a first method step, that a change of the composition of the air/fuel mixture is carried out up to λ =1 in a second method step starting from the value pair to be detected, that the change of the composition is corrected using the delay time of the control path, that the actual λ value of the value pair is determined from the corrected change of the composition of the air/fuel mixture, and that the voltage offset of the voltage λ characteristic curve is detected from a deviation of the actual λ value from the value to be detected.
Document DE102014210442a1 describes a method for correcting a voltage λ characteristic curve (36) of a jump λ sensor (15, 18) arranged in an exhaust channel (17) of an internal combustion engine by adaptation when deviating from a reference voltage λ characteristic curve (35). According to the invention, the adaptation is carried out when the internal combustion engine is not running, wherein a temperature-dependent nominal value of the jump-lambda sensor (15, 18) is checked while delivering heating power.
The object of the present invention is to provide a method which makes use of the output signal of a cost-effective jump lambda sensor upstream of a three-way catalytic converter to achieve a model-based regulation of the oxygen filling level of the three-way catalytic converter.
Furthermore, it is an object of the invention to provide a control device which is suitable for carrying out the method.
Disclosure of Invention
The object of the invention, which relates to the method, is achieved by determining the oxygen intake into the three-way catalytic converter and/or the oxygen exhaust from the three-way catalytic converter from the corrected output signal of the first jump lambda sensor and by modeling the oxygen filling of the three-way catalytic converter from the determined oxygen intake and/or oxygen exhaust. A correction of the output signal of the first jump-lambda sensor with respect to tolerance effects and aging effects, which lead to a shift of the actual sensor characteristic curve from the reference sensor characteristic curve of the non-aged jump-lambda sensor having a jump-lambda characteristic curve according to the data sheet, indicates a clear relationship between the sensor signal and the lambda value of the exhaust gas in a wide lambda range. Thus, a cost-effective jump lambda sensor can be used to balance the oxygen intake into the three-way catalyst and the oxygen output from the three-way catalyst, and the oxygen filling or the oxygen filling level in the three-way catalyst can be modeled from these values. In particular, it is not necessary to take into account the output signal of a jump lambda sensor arranged after the three-way catalyst, which can only show a reaction if a lean or rich cut occurs and the conversion capacity of the three-way catalyst has been greatly reduced. The correction of the tolerance and aging effects is carried out according to known methods, either individually or in combination, in the following steps:
-adapting a constant offset of the sensor characteristic curve
-compensating for the offset of the λ =1 point of the sensor characteristic curve
-compensating for temperature-induced shifts in the sensor characteristic curve
Taking into account the current exhaust gas composition and the lateral sensitivity of the exhaust gas sensor with respect to different exhaust gas components.
A suitable correction of the sensor characteristic curve can be carried out in the following manner: in order to correct for tolerance effects and aging effects, a voltage offset in the output signal of the first jump- λ sensor is identified and corrected, an offset of the λ =1 point of the sensor characteristic curve and a temperature-induced offset are corrected, and the lateral sensitivity of the first jump- λ sensor with respect to the exhaust gas components is taken into account.
A preferred scheme of the method is that: the oxygen filling of the three-way catalyst is regulated in such a way that a filling window that can be specified is avoided. The filling window is selected such that, with regard to the supply of rich or lean exhaust gas during dynamic changes in the operating conditions of the internal combustion engine, a buffer is present due to the oxygen storage capacity of the three-way catalytic converter, which buffer is able to absorb oxygen in lean conditions on the one hand and to release oxygen in rich exhaust gas on the other hand, so that the exhaust gas cleaning in the three-way catalytic converter takes place at λ = 1. With the current oxygen filling level of the three-way catalyst known from the model, the exhaust gas composition can be adjusted early so that there is always enough buffer available.
In one embodiment of the method, provision is made for: the three-way catalyst is divided into two or more regions for which the oxygen filling is modeled separately. Thereby, the filling and emptying processes can be modeled with greater accuracy. Advantageously, the filling level of a single zone is standardized to the current oxygen storage capacity of the respective zone. The fill level of the individual regions (after weighting, if necessary) is converted to an average fill level. With weighting, it can be taken into account that the fill level in a small range at the outlet of the three-way catalyst is decisive for the instantaneous exhaust gas composition after the three-way catalyst. For the development of the filling level in this smaller range at the outlet of the catalyst, the filling level in the preceding volume and the development of the filling level are of decisive significance. This average filling level is set to a setpoint value which minimizes the possibility of a disconnection (durchbreak) after lean and after rich, and this leads to a minimum emission.
In another embodiment of the method, provision is made for: the catalyst model of the three-way catalyst is calibrated by means of the output signal of a second jump-lambda sensor, which is arranged downstream of the three-way catalyst. The second jump-lambda sensor indicates when the three-way catalyst is completely filled with oxygen or completely emptied. This is utilized in order to bring the modeled oxygen filling level into agreement with the actual oxygen filling level according to the lean phase or the rich phase, and in order to adapt the catalyst model if necessary.
The object of the invention is achieved by a control device in the following manner: in the control device, a balancing of the oxygen intake into the three-way catalytic converter and/or of the oxygen exhaust from the three-way catalytic converter is set from the corrected output signal of the first jump lambda sensor, and a determination of the oxygen charge of the three-way catalytic converter is set therefrom.
Drawings
In the following, the invention is explained in more detail by means of embodiments shown in the drawings. The figures show:
fig. 1 shows a schematic illustration of a technical environment in which the method can be used;
fig. 2 is a schematic illustration of the regulation according to the invention.
Detailed Description
Fig. 1 schematically shows a technical environment in which the method according to the invention can be applied. The combustion air supplied by the air supply device 11 is obtained by an internal combustion engine 10, which is embodied as a spark-ignited gasoline engine. The air mass of the combustion air can be determined by means of an air mass meter 12 in the air supply device 11. The delivered air mass is used to determine the fuel quantity to be metered in terms of a lambda value that can be controlled in advance. Furthermore, exhaust gas parameters (in particular the exhaust gas mass flow and the exhaust gas mass derived therefrom) are determined by means of the air mass. The exhaust gases of the internal combustion engine 10 are conducted away through an exhaust gas channel 15, in which a three-way catalyst 16 is arranged. Furthermore, in the exhaust gas duct 15, a first jump lambda sensor 14 upstream of the three-way catalyst 16 and a second jump lambda sensor 17 downstream of the three-way catalyst 16 are arranged, the signals of which are supplied to the control device 20. In addition, the signal of the air mass meter 12 is sent to the control device 20. On the basis of the air mass thus obtained and the signals of the jump lambda sensors 14, 17, a fuel mass is determined in the control device 20, said fuel mass being supplied to the internal combustion engine 10 by means of the fuel metering device 13. For this purpose, the control device 20 comprises a pilot control and a regulating device for regulating the composition of the air-fuel mixture on the basis of the signals of the jump lambda sensors 14, 17.
Fig. 2 shows a schematic view of the regulation according to the invention. The reference numerals already used in fig. 1 are denoted by the same numerals in fig. 2. The internal combustion engine 10 is connected to a three-way catalyst 16 through an exhaust passage 15 and thereafter to the outside. Between the internal combustion engine 10, a first jump- λ sensor 14 is arranged in an exhaust passage 15. After the three-way catalyst 16, a second jump-lambda sensor 17 is arranged in the exhaust gas channel 15. The control of the internal combustion engine 10 is integrated in the control device 20. In the known lambda control, a constant offset of the output signal of the first jump lambda sensor 14 with respect to the sensor characteristic curve in the signal preparation 29 is corrected in the control device 20. In addition, the offset of the point λ =1 of the sensor characteristic curve and the offset caused by temperature are compensated. Finally, the current exhaust gas composition and the lateral sensitivity of the exhaust gas sensor with respect to different exhaust gas components are taken into account. The signal corrected in this way is supplied to a lambda controller 24, which controls the composition of the air-fuel mixture supplied to the internal combustion engine 10. In the pilot controller 21, the output signal of the second jump lambda sensor 17 is evaluated in order to correct the lambda controller 24 in such a way that, on average, a desired lambda value of lambda =1 is maintained.
A fill level regulator 30 according to the invention within the control device 20 regulates the oxygen fill level of the three-way catalytic converter 16. For this purpose, the output signal of the signal preparation 29 is supplied to the discharge model 27 in a differential stage after correction with the signal of the pilot regulator 21. In the emission model 27, the corrected sensor signal is converted into a lambda value or one or more quantities derived therefrom. In this case, the lambda value is advantageously converted into the concentration of one or more exhaust gas components. For example, the λ value can be converted into a value for the concentration of oxygen and carbon monoxide before the three-way catalyst 16. The output value of the emission model 27 or the directly corrected lambda value is supplied to the catalyst model 25. In the catalyst model 25, the filling level of the three-way catalyst 16 is modeled. In particular, the balance of oxygen-introduction and oxygen-discharge amounts is set in order to model the oxygen-filling level. Advantageously, the reaction kinetics of the exhaust gas components calculated by the emission model are taken into account in the modeling. Furthermore, it is advantageous to divide the three-way catalyst 16 into a plurality of regions in which the fill levels are modeled separately. Thus, the filling and emptying processes can be depicted more realistically. For the regulation of the catalyst filling level, it is advantageous to standardize the filling level of the individual zones. The filling level of each region (after weighting, if necessary) is converted to the average filling level of the three-way catalyst 16. With weighting, it can be taken into account that the fill level in a relatively small range at the outlet of the three-way catalyst 16 is decisive for the instantaneous exhaust gas composition downstream of the three-way catalyst 16. The development of the filling level in this small range is influenced by the catalyst volume which it was previously present and by the development of said catalyst volume. The average filling level of the three-way catalyst 16 is set by the filling level regulator 30 to a setpoint value such that the possibility of disconnection after lean and after rich is minimized at the outlet of the three-way catalyst 16. Thereby, the emissions of the internal combustion engine 10 are minimized, which emissions reach the environment.
If necessary, the catalyst model 25 can be calibrated by means of the output signal of the second jump- λ sensor 17 by means of a calibrator 26, the second jump- λ sensor 17 being arranged downstream of the three-way catalyst 16. The output signal of the second jump-lambda sensor 17 indicates when the three-way catalyst 16 is completely filled with oxygen or completely emptied of oxygen. This can be applied in order to align the modeled and actual oxygen-filling levels after the lean or rich phase and to adapt the catalyst model 25 as needed. Thereby, the reliability of the catalyst model 25 can be improved.
The fill level of the three-way catalytic converter 16 is transmitted by the catalytic converter model 25 to the fill level controller 22, which adapts the setpoint value for the lambda controller 24 via the summing stage 23 together with the output signal of the pilot regulator 21.

Claims (4)

1. Method for regulating the oxygen charge of a three-way catalyst (16) in an exhaust gas channel (15) of an internal combustion engine (10) conducting the exhaust gas, wherein the oxygen content of the exhaust gas upstream of the three-way catalyst (16) is determined using a first jump-lambda sensor (14), wherein tolerance effects and aging effects, which lead to a deviation of the actual sensor characteristic curve from a reference sensor characteristic curve, are taken into account and corrected, and wherein the oxygen charge of the three-way catalyst (16) is modeled, characterized in that the oxygen charge into the three-way catalyst (16) and/or the oxygen discharge from the three-way catalyst (16) are determined from the corrected output signal of the first jump-lambda sensor (14), and from which the oxygen charge of the three-way catalyst (16) is modeled, the oxygen charge of the three-way catalyst (16) being adjusted in such a way that a predefined charge window is avoided,
wherein a catalyst model (25) of the three-way catalyst (16) is calibrated by means of an output signal of a second jump-lambda sensor (17) which is arranged downstream of the three-way catalyst (16),
wherein the output signal of the second jump-lambda sensor arranged after the three-way catalyst does not have to be taken into account, said output signal being able to show a reaction only when a lean-cut or a rich-cut occurs and the conversion capacity of the three-way catalyst has been greatly reduced.
2. Method according to claim 1, characterized in that for correcting tolerance effects and aging effects, a voltage offset in the output signal of the first jump- λ sensor (14) is identified and corrected, an offset of the point of the sensor characteristic curve at λ =1 and a temperature-induced offset are corrected, and the lateral sensitivity of the first jump- λ sensor (14) with respect to exhaust gas constituents is taken into account.
3. Method according to claim 1, characterized in that the three-way catalyst (16) is divided into two or more regions for which the oxygen filling is modeled separately.
4. Control device (20) for regulating the oxygen charge of a three-way catalyst (16) in an exhaust gas channel (15) of an internal combustion engine (10) conducting the exhaust gas, wherein a first jump lambda sensor (14) is provided for determining the oxygen content of the exhaust gas upstream of the three-way catalyst (16), wherein tolerance effects and aging effects are taken into account and corrected, which lead to a deviation of the actual sensor characteristic curve from a reference sensor characteristic curve, and wherein a model for modeling the oxygen charge of the three-way catalyst (16) is provided in the control device, characterized in that in the control device a balance of the oxygen intake into the three-way catalyst (16) and/or the oxygen output from the three-way catalyst (16) is set from the first jump lambda sensor (14) Is set in the corrected output signal and from which the determination of the oxygen charge of the three-way catalyst (16) is set,
wherein a catalyst model (25) of the three-way catalyst (16) is calibrated by means of an output signal of a second jump-lambda sensor (17) which is arranged downstream of the three-way catalyst (16),
wherein the output signal of the second jump-lambda sensor arranged after the three-way catalyst does not have to be taken into account, said output signal being able to show a reaction only when a lean-cut or a rich-cut occurs and the conversion capacity of the three-way catalyst has been greatly reduced.
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