WO2013114814A1 - Dispositif de purification de gaz d'échappement pour moteur à combustion interne - Google Patents

Dispositif de purification de gaz d'échappement pour moteur à combustion interne Download PDF

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WO2013114814A1
WO2013114814A1 PCT/JP2013/000284 JP2013000284W WO2013114814A1 WO 2013114814 A1 WO2013114814 A1 WO 2013114814A1 JP 2013000284 W JP2013000284 W JP 2013000284W WO 2013114814 A1 WO2013114814 A1 WO 2013114814A1
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exhaust gas
sensor
constant current
catalyst
rich
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PCT/JP2013/000284
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English (en)
Japanese (ja)
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真浩 横井
幹泰 松岡
真吾 中田
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株式会社デンソー
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Priority to DE112013000824.6T priority Critical patent/DE112013000824T5/de
Priority to US14/376,179 priority patent/US20140373512A1/en
Publication of WO2013114814A1 publication Critical patent/WO2013114814A1/fr

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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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/4065—Circuit arrangements specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/30—Controlling by gas-analysis apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9431—Processes characterised by a specific device
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9459—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts
    • B01D53/9477—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on separate bricks, e.g. 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
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • 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
    • 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
    • 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
    • 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
    • F01N3/24—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 constructional aspects of converting 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
    • F02D41/021—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
    • 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
    • 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
    • F02D41/1473—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
    • F02D41/1476—Biasing of the sensor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
    • G01N27/409—Oxygen concentration cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9413—Processes characterised by a specific catalyst
    • B01D53/9422—Processes characterised by a specific catalyst for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • 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
    • 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
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842—Nitrogen oxides
    • 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
    • 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
    • F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
    • F02D41/0275—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a NOx trap or adsorbent
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the present disclosure relates to an exhaust gas purifying apparatus for an internal combustion engine including a catalyst for purifying exhaust gas of an internal combustion engine and an exhaust gas sensor installed downstream or in the middle of the catalyst.
  • an exhaust gas purification catalyst for example, a three-way catalyst or NO x storage reduction type
  • an exhaust gas sensor air-fuel ratio sensor or oxygen sensor
  • Patent Document 2 Japanese Patent Publication No. 8-20414
  • a gas sensor such as an oxygen sensor
  • this auxiliary electrochemical cell is connected to one of the gas sensors.
  • a sensor element is configured by laminating a diaphragm layer, a reference electrode electron conduction layer, a solid electrolyte layer, and a measurement electrode electron conduction layer.
  • oxygen ions are moved from the measurement electrode side to the reference electrode side by the current supplied from the DC power source, so that the oxygen partial pressure on the measurement electrode side is reduced to the oxygen in the exhaust gas (detected gas).
  • an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio is detected by lowering the partial pressure (see the column (A) in FIG. 11).
  • Japanese Patent No. 3997599 Japanese Patent Publication No. 8-20414 JP, 56-89051 A The air-fuel ratio of the exhaust gas flowing into the catalyst changes depending on the operating state of the internal combustion engine, and the air-fuel ratio of the exhaust gas downstream of the catalyst and in the catalyst also changes accordingly.
  • the exhaust gas purification system of Patent Document 1 does not have a function of changing the output characteristics of the exhaust gas sensor, the exhaust gas purification system is affected by a delay in sensor output change with respect to changes in the air-fuel ratio downstream of the catalyst or in the catalyst.
  • the catalyst may not be used effectively, and exhaust emissions cannot be effectively reduced.
  • Patent Document 2 a technique for changing the output characteristics of a gas sensor is disclosed.
  • an auxiliary electrochemical cell needs to be incorporated in the gas sensor, a general technique that does not include an auxiliary electrochemical cell is provided. Therefore, it is necessary to change the sensor structure greatly with respect to a new gas sensor, and it is necessary to change the design of the gas sensor for practical use. As a result, the manufacturing cost of the gas sensor increases.
  • the output E of the oxygen sensor can be expressed by the following basic equation (Nernst equation).
  • E (R * T) / (4 * F) * ln (P1 / P2)
  • R is a gas constant
  • T is an absolute temperature
  • F is a Faraday constant
  • P1 is an oxygen partial pressure on the atmosphere side (reference electrode side)
  • P2 is an oxygen partial pressure on the exhaust side (measurement electrode side).
  • the oxygen sensor of Patent Document 3 is configured so that the reference electrode side is not exposed to the atmosphere and oxygen is supplied from the measurement electrode side to the reference electrode side.
  • the oxygen concentration on the reference electrode side may not be kept constant.
  • the oxygen concentration on the measurement electrode side is significantly reduced.
  • the oxygen concentration on the measurement electrode side is significantly reduced.
  • the output on the rich side of the oxygen sensor becomes unstable, and the detection accuracy of the oxygen sensor may be reduced.
  • the oxygen sensor of Patent Document 3 can shift the output characteristic line of the oxygen sensor to the lean side by flowing current so as to supply oxygen from the measurement electrode side to the reference electrode side.
  • the oxygen sensor output characteristic line can hardly be shifted to the rich side because oxygen is hardly supplied from the reference electrode side to the measurement electrode side. [See column (C) in FIG. 11].
  • the present disclosure aims to solve the above problems.
  • a catalyst for purifying exhaust gas of an internal combustion engine and a solid electrolyte body provided between a pair of sensor electrodes are provided on the downstream side of the catalyst or on the catalyst.
  • An exhaust gas purification apparatus for an internal combustion engine comprising: an exhaust gas sensor for detecting a concentration of a predetermined component in the exhaust gas by a sensor element in which one of the pair of sensor electrodes is exposed to the atmosphere.
  • Constant current supply unit that changes the output characteristics of the exhaust gas sensor by passing a constant current between the electrodes, and the direction of the constant current that flows between the sensor electrodes according to the change request to change the output characteristics of the exhaust gas sensor or the operating state of the internal combustion engine And a current control unit that controls the constant current supply unit so that a constant current flows in the determined direction.
  • the output characteristics of the exhaust gas sensor can be changed by flowing a constant current between the sensor electrodes by the constant current supply unit.
  • the output characteristics of the exhaust gas sensor can be changed without causing a significant design change or cost increase of the exhaust gas sensor.
  • the direction of the constant current flowing between the sensor electrodes is determined according to a change request for changing the output characteristics of the exhaust gas sensor or the operating state of the internal combustion engine, and the constant current supply unit is controlled so that the constant current flows in the determined direction.
  • the constant current supply unit is controlled so that the constant current flows in the determined direction.
  • the oxygen concentration on the atmosphere side sensor electrode side is always controlled regardless of the oxygen concentration on the other sensor electrode (exhaust side sensor electrode) side. Even if an exhaust gas sensor is installed on the downstream side of the catalyst, that is, when the oxygen concentration of the exhaust gas detected by the exhaust gas sensor may be significantly reduced, the output of the exhaust gas sensor can be maintained. The output variation can be reduced and the output can be stabilized.
  • the output characteristic line of the exhaust gas sensor can be shifted to the lean side, and the exhaust gas is discharged from the atmosphere side sensor electrode side.
  • the output characteristic line of the exhaust gas sensor can be shifted to the rich side, and the output characteristic line of the exhaust gas sensor can be shifted to either the lean side or the rich side.
  • the present invention is applied to a system equipped with a NO x storage reduction catalyst that reduces and purifies NO x stored in the catalyst when released. In this way, exhaust emission can be reduced by effectively utilizing the NO x storage reduction catalyst.
  • the exhaust gas sensor during the lean combustion control for controlling the air-fuel ratio of a mixture supplied to the internal combustion engine to a lean
  • the rich component of the exhaust gas sensor is controlled during the rich combustion control in which the constant current supply unit is controlled so that the constant current flows in a direction to increase the detection response to the lean component, and the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is controlled to be rich. It is preferable to control the constant current supply unit so that the constant current flows in a direction to improve the detection response to the.
  • the air-fuel ratio of the exhaust gas flowing into the NO X storage reduction catalyst becomes lean, and NO X (lean component) in the exhaust gas is stored in the NO X storage reduction catalyst.
  • NO X storage amount of X storage reduction catalyst increases, so NO X in the exhaust gas is discharged to the downstream side of the NO X storage reduction catalyst through the the NO X storage reduction catalyst.
  • NO X occluding air-fuel ratio of the exhaust gas flowing into the catalytic reduction catalyst becomes rich, NO X HC and CO (rich components of storage reduction catalyst NO X which is stored in the in the exhaust gas ) by it is released is reduced and purified, the NO X storage reduction type when the NO X storage amount of the catalyst is reduced, the NO X storage reduction catalyst HC and CO in the exhaust gas passes through the the NO X storage reduction catalyst It is discharged to the downstream side.
  • CO in the exhaust gas may be applied to a system with a three-way catalyst for purifying NO X.
  • the exhaust emission can be reduced by effectively utilizing the three-way catalyst.
  • FIG. 1 is a diagram illustrating a schematic configuration of an engine control system according to a first embodiment of the present disclosure.
  • FIG. 2 is a cross-sectional view showing a cross-sectional configuration of the sensor element.
  • FIG. 3 is an electromotive force characteristic diagram showing the relationship between the air-fuel ratio (excess air ratio ⁇ ) of exhaust gas and the electromotive force of the sensor element.
  • FIG. 4A is a schematic diagram showing the state of gas components around the sensor element.
  • FIG. 4B is a schematic diagram showing the state of gas components around the sensor element.
  • FIG. 5 is a time chart for explaining the behavior of the sensor output.
  • FIG. 1 is a diagram illustrating a schematic configuration of an engine control system according to a first embodiment of the present disclosure.
  • FIG. 2 is a cross-sectional view showing a cross-sectional configuration of the sensor element.
  • FIG. 3 is an electromotive force characteristic diagram showing the relationship between the air-fuel ratio (excess air ratio ⁇ ) of exhaust gas
  • FIG. 6A is a schematic diagram showing the state of gas components around the sensor element.
  • FIG. 6B is a schematic diagram showing the state of gas components around the sensor element.
  • FIG. 7 is an output characteristic diagram of the oxygen sensor when the lean response / rich response is enhanced.
  • FIG. 8 is a time chart for explaining an execution example of catalyst utilization control.
  • FIG. 9 is a flowchart showing the flow of processing of the catalyst utilization control routine.
  • FIG. 10 is a diagram for explaining the effect of the first embodiment.
  • FIG. 11 is a diagram for explaining the prior art.
  • FIG. 12 is a diagram illustrating a schematic configuration of an engine control system according to the second embodiment.
  • FIG. 13 is a flowchart showing the flow of processing of the sensor responsiveness control routine.
  • Example 1 of the present disclosure will be described with reference to FIGS.
  • the intake pipe 12 of the engine 11 is provided with a throttle valve 13 whose opening is adjusted by a motor or the like, and a throttle opening sensor 14 for detecting the opening (throttle position) of the throttle valve 13.
  • a fuel injection valve 15 that performs in-cylinder injection or intake port injection is attached to each cylinder of the engine 11, and a spark plug 16 is attached to each cylinder of the cylinder head of the engine 11. The air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 16.
  • the exhaust pipe 17 of the engine 11 is provided with a three-way catalyst 18 for purifying CO, HC, NO x and the like in the exhaust gas, and the NO x storage reduction catalyst 19 is provided downstream of the three-way catalyst 18. Is provided.
  • exhaust gas sensors 20 and 21 for detecting the air-fuel ratio or rich / lean of the exhaust gas are installed on the upstream side and the downstream side of the three-way catalyst 18, respectively.
  • an air-fuel ratio sensor linear A / F sensor
  • An oxygen sensor O 2 sensor whose output voltage is inverted depending on whether it is lean or not is used.
  • an oxygen sensor 28 (O 2 sensor) whose output voltage is inverted depending on whether the air-fuel ratio of the exhaust gas is rich or lean with respect to the stoichiometric air-fuel ratio is installed as an exhaust gas sensor on the downstream side of the NO x storage reduction catalyst 19. Has been.
  • this system includes a crank angle sensor 22 that outputs a pulse signal every time a crankshaft (not shown) of the engine 11 rotates by a predetermined crank angle, an air amount sensor 23 that detects an intake air amount of the engine 11, Various sensors such as a cooling water temperature sensor 24 for detecting the cooling water temperature of the engine 11 are provided. Based on the output signal of the crank angle sensor 22, the crank angle and the engine speed are detected.
  • the outputs of these various sensors are input to an electronic control unit (hereinafter referred to as “ECU”) 25.
  • the ECU 25 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount and the ignition timing are determined according to the engine operating state.
  • the throttle opening (intake air amount) and the like are controlled.
  • the oxygen sensor 28 includes a sensor element 31 having a cup-shaped structure.
  • the sensor element 31 is configured so that the entire element is accommodated in a housing or an element cover (not shown). Arranged in the tube 17.
  • the solid electrolyte layer 32 (solid electrolyte body) is formed in a cup shape in cross section, an exhaust side electrode layer 33 is provided on the outer surface, and an air side electrode layer 34 is provided on the inner surface. It has been.
  • the solid electrolyte layer 32 is made of an oxygen ion conductive oxide that is formed by dissolving CaO, MgO, Y 2 O 3 , Yb 2 O 3 or the like as a stabilizer in ZrO 2 , HfO 2 , ThO 2 , Bi 2 O 3 or the like. Consists of union.
  • Each of the electrode layers 33 and 34 is made of a noble metal having high catalytic activity such as platinum, and the surface thereof is subjected to porous chemical plating or the like.
  • Electrode layers 33 and 34 form a pair of counter electrodes (sensor electrodes).
  • An internal space surrounded by the solid electrolyte layer 32 is an atmospheric chamber 35, and a heater 36 is accommodated in the atmospheric chamber 35.
  • the heater 36 has a heat generation capacity sufficient to activate the sensor element 31, and the entire sensor element 31 is heated by the heat generation energy.
  • the activation temperature of the oxygen sensor 28 is about 350 to 400 ° C., for example.
  • the atmosphere chamber 35 is maintained at a predetermined oxygen concentration by introducing the atmosphere, and the atmosphere-side electrode layer 34 is exposed to the atmosphere in the atmosphere chamber 35.
  • the outside of the solid electrolyte layer 32 (electrode layer 33 side) is an exhaust atmosphere
  • the inside of the solid electrolyte layer 32 (electrode layer 34 side) is an air atmosphere.
  • An electromotive force is generated between the electrode layers 33 and 34 in accordance with the difference in partial pressure. That is, the sensor element 31 generates different electromotive force depending on whether the air-fuel ratio is rich or lean.
  • the oxygen sensor 28 outputs an electromotive force signal corresponding to the oxygen concentration (that is, the air-fuel ratio) of the exhaust gas.
  • the exhaust-side electrode layer 33 of the sensor element 31 is grounded, and the microcomputer 26 is connected to the atmosphere-side electrode layer 34.
  • a sensor detection signal corresponding to the electromotive force is output to the microcomputer 26.
  • the microcomputer 26 is provided in the ECU 25, for example, and calculates the air-fuel ratio based on the sensor detection signal.
  • the microcomputer 26 may calculate the engine rotation speed and the intake air amount based on the detection results of the various sensors described above.
  • the actual air-fuel ratio of the exhaust gas changes sequentially, and may change repeatedly, for example, between rich and lean.
  • the detection response of the oxygen sensor 28 is low, there is a concern that the engine performance may be affected. For example, when the engine 11 is operating at a high load, the amount of NO x in the exhaust gas increases more than intended.
  • the detection response of the oxygen sensor 28 when the actual air-fuel ratio changes between rich and lean will be described.
  • the actual air-fuel ratio the actual air-fuel ratio downstream of the NO x storage reduction catalyst 19
  • the component composition of the exhaust gas changes.
  • the change in the output of the oxygen sensor 28 relative to the air-fuel ratio after the change is delayed. Specifically, at the time of the change from rich to lean, as shown in FIG.
  • the output change of the oxygen sensor 28 will be described with reference to the time chart of FIG.
  • the sensor output (the output of the oxygen sensor 28) changes between the rich gas detection value (0.9 V) and the lean gas detection value (0 V) according to the change in the actual air-fuel ratio. Change.
  • the sensor output changes with a delay with respect to the change in the actual air-fuel ratio.
  • the sensor output changes with a delay of TD1 with respect to the change of the actual air-fuel ratio when changing from rich to lean, and the sensor output is delayed with respect to the change of the actual air-fuel ratio when changing from lean to rich. It has come to change.
  • a constant current circuit 27 as a constant current supply unit is connected to the atmosphere side electrode layer 34, and the constant current Ics is supplied from the constant current circuit 27 to the microcomputer 26.
  • the microcomputer 26 sets the direction and amount of the constant current Ics flowing between the pair of sensor electrodes, and controls the constant current circuit 27 so that the set constant current Ics flows.
  • the constant current circuit 27 supplies the constant current Ics to the atmosphere-side electrode layer 34 in either the forward or reverse direction, and the constant current amount can be variably adjusted. That is, the microcomputer 26 variably controls the constant current Ics by PWM control. In this case, in the constant current circuit 27, the constant current Ics is adjusted according to the duty signal output from the microcomputer 26, and the constant current Ics adjusted in the amount of current is provided between the sensor electrodes (the exhaust side electrode layer 33 and the atmosphere side). Between the electrode layers 34).
  • the constant current Ics that flows in the direction of the exhaust side electrode layer 33 ⁇ the atmosphere side electrode layer 34 is a negative constant current ( ⁇ Ics), and the constant current that flows in the direction of the atmosphere side electrode layer 34 ⁇ the direction of the exhaust side electrode layer 33.
  • Ics is a positive constant current (+ Ics).
  • a constant current Ics positive constant current Ics
  • the reduction reaction is promoted with respect to the lean component (NO x ) existing (residual) around the exhaust side electrode layer 33, and accordingly, the lean component is reduced. It can be removed quickly.
  • the rich component (HC) easily reacts in the exhaust-side electrode layer 33, and as a result, the responsiveness of the rich output of the oxygen sensor 28 is improved.
  • FIG. 7 is a diagram showing output characteristics (electromotive force characteristics) of the oxygen sensor 28 when increasing the detection responsiveness (lean sensitivity) at the time of lean change and when increasing the detection responsiveness (rich sensitivity) at the time of rich change. is there.
  • the negative constant current Ics is set so that oxygen is supplied from the atmosphere-side electrode layer 34 to the exhaust-side electrode layer 33 through the solid electrolyte layer 32 as described above.
  • the output characteristic line shifts to the rich side (more specifically, shifts to the rich side and to the electromotive force decreasing side), as indicated by the one-dot chain line (a) in FIG.
  • the sensor output becomes a lean output even if the actual air-fuel ratio is in a rich region near the stoichiometric air-fuel ratio. This means that the detection response (lean sensitivity) at the time of a lean change is enhanced as the output characteristic of the oxygen sensor 28.
  • the detection responsiveness (rich sensitivity) at the time of rich change is enhanced, a positive constant current is supplied so that oxygen is supplied from the exhaust-side electrode layer 33 to the atmosphere-side electrode layer 34 through the solid electrolyte layer 32 as described above.
  • the output characteristic line shifts to the lean side (more specifically, shifts to the lean side and to the electromotive force increasing side), as shown by a one-dot chain line (b) in FIG. .
  • the sensor output becomes a rich output. This means that the detection response at the time of rich change (rich sensitivity) is enhanced as the output characteristic of the oxygen sensor 28.
  • the ECU 25 (or the microcomputer 26) executes a catalyst utilization control routine of FIG. 9 to be described later, so that between the sensor electrodes (exhaust side electrode layer 33 and atmosphere side electrode) according to the operating state of the engine 11.
  • the direction of the constant current Ics flowing between the layer 34 and the constant current circuit 27 is controlled so that the constant current Ics flows in the determined direction. Accordingly, even after changing the state of the exhaust gas downstream of the NO X storage reduction state of the exhaust gas flowing into the catalyst 19 changes the NO X storage reduction catalyst 19 by the operating state of the engine 11, accordingly Thus, the output response of the oxygen sensor 28 can be changed to improve the detection response.
  • NO x lean component
  • the lean combustion control NO x (lean component) is discharged downstream of the NO x storage reduction catalyst 28 at time t1 when the output of the oxygen sensor 28 becomes a predetermined lean determination threshold value (eg, 0.45 V) or less.
  • a predetermined rich determination threshold value for example, 0.45 V
  • HC and CO rich components
  • the constant current circuit 27 is controlled so that the constant current Ics flows in a direction in which the lean sensitivity of the oxygen sensor 28 is increased and the lean response (detection response to the lean component) is increased.
  • the constant current circuit 27 is controlled so that the constant current Ics (negative constant current Ics) flows in a direction in which oxygen is supplied from the atmosphere-side electrode layer 34 to the exhaust-side electrode layer 33.
  • the constant current circuit 27 is controlled so that the constant current Ics flows in a direction in which the rich sensitivity of the oxygen sensor 28 is increased to increase the rich response (detection response to the rich component).
  • the constant current circuit 27 is controlled so that the constant current Ics (positive constant current Ics) flows in the direction in which oxygen is supplied from the exhaust side electrode layer 33 to the atmosphere side electrode layer 34.
  • the air-fuel ratio of the exhaust gas flowing into the NO X storage reduction catalyst 19 becomes lean, and NO X (lean component) in the exhaust gas is stored in the NO X storage reduction catalyst 19.
  • NO X storage amount of the NO X occluding and reducing catalyst 19 is increased, so that NO X in the exhaust gas is discharged to the downstream side of the NO X occluding and reducing catalyst 19 through the the NO X storage reduction catalyst 19 become. Therefore, if the lean response of the oxygen sensor 28 (detection response to the lean component) is increased during the lean combustion control, the NO X storage amount of the NO X storage reduction catalyst 19 increases during the lean combustion control.
  • the state can be detected early by the oxygen sensor 28.
  • the lean combustion control can be stopped at an early stage when NO X is exhausted downstream of the NO X storage reduction catalyst 19 after the start of the lean combustion control. compared to a system that does not have a function of changing the (see a broken line in FIG. 8), it is possible to reduce the emissions of nO X.
  • NO X air-fuel ratio of the exhaust gas flowing into the occlusion-reduction catalyst 19 becomes rich, Ya the NO X storage reduction type HC of the NO X which the catalyst 19 has been occluded in the exhaust gas Although it is reduced and purified by CO (rich component) and released, when the NO X storage amount of the NO X storage reduction catalyst 19 decreases, HC and CO in the exhaust gas pass through the NO X storage reduction catalyst 19.
  • the NO x storage reduction catalyst 19 is discharged downstream.
  • the NO X storage amount of the NO X storage reduction catalyst 19 during the rich combustion control is getting low
  • the state can be detected early by the oxygen sensor 28.
  • the rich combustion control can be stopped at an early stage when HC and CO are discharged downstream of the NO x storage reduction catalyst 19 after the rich combustion control is started.
  • the amount of HC and CO emissions can be reduced.
  • the catalyst utilization control routine shown in FIG. 9 is repeatedly executed at a predetermined period during the power-on period of the ECU 25, and serves as a current control unit.
  • step 101 it is determined whether a lean operation execution condition is satisfied.
  • the lean operation execution condition is, for example, that all the following conditions (1) to (3) are satisfied.
  • the cooling water temperature of the engine 11 is equal to or higher than a predetermined temperature
  • the NO X storage reduction catalyst 19 is in an active state (for example, the estimated temperature or detected temperature of the catalyst 19 is equal to or higher than the active temperature, or the elapsed time after engine start is equal to or longer than a predetermined time).
  • the routine proceeds to step 103, and during the lean combustion control, the constant current circuit 27 is controlled so that the constant current Ics flows in the direction of increasing the lean responsiveness of the oxygen sensor 28. That is, the constant current circuit 27 is controlled so that the constant current Ics (negative constant current Ics) flows in a direction in which oxygen is supplied from the atmosphere-side electrode layer 34 to the exhaust-side electrode layer 33. Thereby, the lean responsiveness of the oxygen sensor 28 is enhanced.
  • step 104 it is determined whether or not the output of the oxygen sensor 28 is equal to or lower than the lean determination threshold (for example, 0.45V), and it is determined that the output of the oxygen sensor 28 is higher than the lean determination threshold. Therefore, the process returns to step 102, and the lean combustion control is continued and the control for increasing the lean responsiveness of the oxygen sensor 28 is continued (steps 102 and 103).
  • the lean determination threshold for example 0.45V
  • the routine proceeds to step 106, and during the rich combustion control, the constant current circuit 27 is controlled so that the constant current Ics flows in the direction of increasing the rich response of the oxygen sensor 28. That is, the constant current circuit 27 is controlled so that the constant current Ics (positive constant current Ics) flows in the direction in which oxygen is supplied from the exhaust side electrode layer 33 to the atmosphere side electrode layer 34. Thereby, the rich responsiveness of the oxygen sensor 28 is improved.
  • step 107 when it is determined that the output of the oxygen sensor 28 is lower than the rich determination threshold depending on whether the output of the oxygen sensor 28 is equal to or higher than the rich determination threshold (eg, 0.45V).
  • the rich combustion control is continued, and the control for increasing the rich response of the oxygen sensor 28 is continued (steps 105, 106).
  • step 107 when it is determined in step 107 that the output of the oxygen sensor 28 is greater than or equal to the rich determination threshold value, it is determined that HC and CO (rich components) have started to be discharged downstream of the NO x storage reduction catalyst 19. Then, the process proceeds to step 108 and the rich combustion control is stopped.
  • the oxygen sensor 28 in the system in which the oxygen sensor 28 is installed on the downstream side of the NO x storage reduction catalyst 19, a constant current is caused to flow between the sensor electrodes by the constant current circuit 27 provided outside the oxygen sensor 28.
  • the output characteristics of the oxygen sensor 28 can be changed to improve lean responsiveness and rich responsiveness.
  • the output characteristics of the oxygen sensor 28 can be changed without causing a significant design change or cost increase.
  • the constant current circuit 27 is controlled so that the constant current Ics flows in the direction of increasing the lean responsiveness of the oxygen sensor 28, so that the downstream side of the NO X storage reduction catalyst 19 is provided.
  • the NO x lean component
  • the constant current circuit 27 is controlled so that the constant current Ics flows in a direction in which the rich response of the oxygen sensor 28 is increased, so that the downstream side of the NO X storage reduction catalyst 19 is controlled.
  • the output E of the oxygen sensor 28 can be expressed by the following basic equation (Nernst equation).
  • E (R * T) / (4 * F) * ln (P1 / P2)
  • R is a gas constant
  • T is an absolute temperature
  • F is a Faraday constant
  • P1 is an oxygen partial pressure on the atmosphere side electrode layer 34 side
  • P2 is an oxygen partial pressure on the exhaust side electrode layer 33 side.
  • the oxygen concentration on the atmosphere side electrode layer 34 side is stabilized to stabilize the oxygen partial pressure P1 on the atmosphere side electrode layer 34 side. Is important.
  • the oxygen sensor 28 of the first embodiment has the atmosphere side electrode layer 34 exposed to the atmosphere, so that the oxygen side is not affected by the oxygen concentration on the exhaust side electrode layer 33 side.
  • the oxygen concentration on the electrode layer 34 side can always be kept constant (equivalent to the atmosphere), and even when the oxygen sensor 28 is installed on the downstream side of the catalyst 19, that is, the oxygen concentration of the exhaust gas detected by the oxygen sensor 28 is remarkably high. Even in the case of a decrease, the output of the oxygen sensor 28 can be stabilized.
  • the output characteristic line of the oxygen sensor 28 can be shifted to the lean side, and the atmosphere side electrode layer
  • the output characteristic line of the oxygen sensor 28 can be shifted to the rich side, and the output characteristic line of the oxygen sensor 28 is set to the lean side.
  • a configuration was installed oxygen sensor 28 on the downstream side of the NO X occluding and reducing catalyst 19, the position in of the NO X occluding and reducing catalyst 19 (for example, the catalyst 19 inlet and outlet A configuration may be adopted in which the oxygen sensor 28 is installed at an intermediate position.
  • Example 2 of the present disclosure will be described with reference to FIGS. 12 and 13. However, description of substantially the same parts as those in the first embodiment will be omitted or simplified, and different parts from the first embodiment will be mainly described.
  • a three-way catalyst 37 for purifying CO, HC, NO x and the like in the exhaust gas is also provided on the downstream side of the three-way catalyst 18.
  • an exhaust gas sensor 20 air-fuel ratio sensor or oxygen sensor
  • the three-way catalyst 37 is provided with an oxygen sensor 28 whose output voltage is inverted depending on whether the air-fuel ratio of the exhaust gas is rich or lean with respect to the stoichiometric air-fuel ratio.
  • the ECU 25 (or the microcomputer 26) executes a sensor response control routine of FIG.
  • the sensor responsiveness control routine shown in FIG. 13 is repeatedly executed at a predetermined cycle during the power-on period of the ECU 25.
  • this routine in steps 201 to 203, it is determined whether or not there is a change request for changing the detection responsiveness of the oxygen sensor 28.
  • steps 204 to 207 constant current control is performed based on the change request determination result. Thus, the detection responsiveness of the oxygen sensor 28 is changed.
  • step 201 it is determined whether or not the engine 11 is in a cold state at the time of starting, for example, depending on whether or not one of the following conditions (1) to (3) is satisfied.
  • the cooling water temperature of the engine 11 is not more than a predetermined temperature (2)
  • the oil temperature (lubricating oil temperature) of the engine 11 is below a predetermined temperature (3)
  • the fuel temperature in the fuel path is equal to or lower than a predetermined temperature. If it is determined in step 201 that the engine 11 is in a cold state, a change request for increasing rich responsiveness (detection responsiveness during rich change). It is determined that there is. In this case, the process proceeds to step 204, and the supply of the constant current Ics is controlled based on the change request for increasing the rich responsiveness. Specifically, “positive constant current Ics” is set as the constant current of the constant current circuit 27.
  • the microcomputer 26 controls the constant current circuit 27, and the constant current Ics (positive constant current Ics) flows in the direction in which oxygen is supplied from the exhaust side electrode layer 33 to the atmosphere side electrode layer 34. Thereby, when the engine 11 is in a cold state, the rich responsiveness of the oxygen sensor 28 is enhanced.
  • the constant current amount is preferably a predetermined value.
  • step 201 when it is determined in step 201 that the engine 11 is not in the cold state, the process proceeds to step 202 to determine whether or not the engine 11 is in the high load operation state, for example, the following (4) Judgment is made based on whether or not one of the conditions (6) to (6) is satisfied.
  • step 202 when it is determined that the engine 11 is in a high load operation state, a change request for increasing lean responsiveness (detection responsiveness when lean changes). It is determined that there is. In this case, the process proceeds to step 205, and the supply of the constant current Ics is controlled based on the change request for improving the lean responsiveness. Specifically, “negative constant current Ics” is set as the constant current of the constant current circuit 27.
  • the microcomputer 26 controls the constant current circuit 27, and the constant current Ics (negative constant current Ics) flows in the direction in which oxygen is supplied from the atmosphere side electrode layer 34 to the exhaust side electrode layer 33. Thereby, when the engine 11 is in a high load operation state, the lean responsiveness of the oxygen sensor 28 is enhanced.
  • the constant current amount is preferably a predetermined value.
  • the high-load operation period includes a transient time when the engine load changes to an increasing side and a high-load steady time when the load is high due to the load increase.
  • both the transient response and the high load steady state can improve the lean response, but in order to increase the detection response, the response level required as the detection response is required for the transient and high load steady state. It is better to make them different.
  • the response level at the time of transition is set to be higher than the response level at the time of steady high load. That is, when it is determined that the engine 11 is in a high load operation state, it is further determined whether the engine 11 is in a transient state or a high load steady state. It is determined that there is a change request to make the response level relatively small (less than in the high load steady state) while increasing the lean response and determining that it is a transient time. Correspondingly, it is determined that there is a change request to increase the lean responsiveness and relatively increase the responsiveness level (increase the transient level) while determining that the load is steady at high load. It corresponds to that. Then, the supply of the constant current Ics is controlled based on the change request in each of the transition time and the high load steady time.
  • step 202 determines whether or not rich injection control for neutralization is being performed.
  • rich injection control when the engine 11 returns from the fuel cut, based on the detection result of the oxygen sensor 28, the air-fuel ratio is adjusted so as to eliminate the excessive oxygen state (extremely lean atmosphere) of the two catalysts 18, 37. This is air-fuel ratio control that is temporarily enriched.
  • the atmosphere of both the catalysts 18 and 37 is neutralized by the enrichment of the fuel injection amount (the state is maintained near the theoretical air-fuel ratio).
  • the rich injection control is terminated.
  • this rich injection control when this rich injection control is performed, the detection responsiveness at the time of rich change is lowered.
  • step 203 If it is determined in this step 203 that the rich injection control is being performed, it is determined that there is a change request for reducing the rich responsiveness (detection responsiveness at the time of rich change). In this case, the process proceeds to step 206, and the supply of the constant current Ics is controlled based on the change request for reducing the rich responsiveness.
  • “negative constant current Ics” is set as the constant current of the constant current circuit 27.
  • the microcomputer 26 controls the constant current circuit 27, and the constant current Ics (negative constant current Ics) flows in the direction in which oxygen is supplied from the atmosphere side electrode layer 34 to the exhaust side electrode layer 33. Thereby, the rich responsiveness is lowered when the rich injection control is performed.
  • the constant current amount is preferably a predetermined value.
  • step 201 and 204 the processing to increase the rich response of the oxygen sensor 28 when the engine 11 is cold (steps 201 and 204), and the lean response of the oxygen sensor 28 when the engine 11 is in a high load operation state.
  • the process of increasing the responsiveness (steps 202 and 205) and the process of reducing the rich responsiveness of the oxygen sensor 28 when the rich injection control is being performed (steps 203 and 206) are all performed. Instead, any one or two may be implemented.
  • the three-way catalyst 18 in the system in which the oxygen sensor 28 is installed on the downstream side of the three-way catalyst 18, it is determined whether there is a change request for changing the detection responsiveness of the oxygen sensor 28, and the change request is determined. Since the constant current control is performed based on the result and the detection responsiveness of the oxygen sensor 28 is changed, the three-way catalyst 18 can be effectively used to reduce the exhaust emission.
  • the oxygen sensor 28 is installed on the downstream side of the three-way catalyst 18.
  • the oxygen sensor 28 is provided at a position in the three-way catalyst 18 (for example, an intermediate position between the inlet and the outlet of the catalyst 18).
  • An installed configuration may be used.
  • the constant current circuit 27 is connected to the atmosphere-side electrode layer 34 of the oxygen sensor 28 (sensor element 31).
  • the present invention is not limited to this.
  • the oxygen sensor 28 The constant current circuit 27 may be connected to the exhaust side electrode layer 33 of the sensor element 31), or the constant current circuit 27 may be connected to both the exhaust side electrode layer 33 and the atmosphere side electrode layer 34. .
  • the present disclosure is applied to a system using the oxygen sensor 28 having the sensor element 31 having a cup-type structure.
  • the present disclosure is not limited thereto.
  • the present disclosure may be applied to a system using an oxygen sensor having the above.
  • the present invention is not limited to an oxygen sensor.
  • an oxygen sensor such as an air-fuel ratio sensor that outputs a linear air-fuel ratio signal corresponding to an air-fuel ratio, an HC sensor that detects HC concentration, or an NO X sensor that detects NO X concentration.
  • the present disclosure may be applied to this gas sensor.

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Abstract

Dans un système dans lequel un capteur d'oxygène (28) est installé en aval d'un catalyseur de réduction de stockage de NOx (19), la caractéristique de sortie du capteur d'oxygène (28) peut être changée par le passage d'un courant constant entre les électrodes de capteur au moyen d'un circuit de courant constant prévu sur l'extérieur du capteur d'oxygène (28). En outre, au cours d'une commande de combustion de mélange pauvre pour le moteur (11), la détection de la réponse du capteur d'oxygène (28) par rapport à la composante de mélange pauvre est augmentée; ainsi, quand NOx (le composant pauvre) est déchargé en aval du catalyseur (19) il peut être détecté rapidement par le capteur d'oxygène (28). Parallèlement, au cours d'une commande de combustion de mélange riche, la détection de la réponse du capteur d'oxygène (28) par rapport à la composante de mélange riche en est augmentée; ainsi, quand HC et CO (les composants riche) sont déchargés en aval du catalyseur (19), ceux-ci peuvent être détectés rapidement par le capteur d'oxygène (28).
PCT/JP2013/000284 2012-02-03 2013-01-22 Dispositif de purification de gaz d'échappement pour moteur à combustion interne WO2013114814A1 (fr)

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WO2015019583A1 (fr) * 2013-08-09 2015-02-12 株式会社デンソー Dispositif de commande de capteur de gaz
JP2015034804A (ja) * 2013-08-09 2015-02-19 株式会社デンソー ガスセンサ制御装置、及びガスセンサ制御方法

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JP5904173B2 (ja) 2013-08-09 2016-04-13 株式会社デンソー ガスセンサ制御装置
JP5904171B2 (ja) 2013-08-09 2016-04-13 株式会社デンソー ガスセンサ制御装置
JP6237057B2 (ja) * 2013-09-27 2017-11-29 株式会社デンソー ガスセンサ制御装置
JP6398866B2 (ja) * 2015-05-19 2018-10-03 株式会社デンソー 酸素センサの制御方法
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