WO2014033836A1 - 火花点火式内燃機関の排気浄化装置 - Google Patents
火花点火式内燃機関の排気浄化装置 Download PDFInfo
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- WO2014033836A1 WO2014033836A1 PCT/JP2012/071693 JP2012071693W WO2014033836A1 WO 2014033836 A1 WO2014033836 A1 WO 2014033836A1 JP 2012071693 W JP2012071693 W JP 2012071693W WO 2014033836 A1 WO2014033836 A1 WO 2014033836A1
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- 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
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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
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
- F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
- F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
- F01N3/025—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust
- F01N3/0253—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust adding fuel to exhaust gases
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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
- 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
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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
- 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
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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
- F01N9/00—Electrical control of exhaust gas treating apparatus
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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
- F01N9/00—Electrical control of exhaust gas treating apparatus
- F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration, e.g. detection of clogging
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- 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
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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
- F01N2430/00—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics
- F01N2430/06—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by varying fuel-air ratio, e.g. by enriching fuel-air mixture
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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
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
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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
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/10—Adding substances to exhaust gases the substance being heated, e.g. by heating tank or supply line of the added substance
- F01N2610/105—Control thereof
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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
- 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
- F01N2900/18—Parameters used for exhaust control or diagnosing said parameters being related to the system for adding a substance into the exhaust
- F01N2900/1806—Properties of reducing agent or dosing system
- F01N2900/1811—Temperature
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- 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
- F02D2200/0806—NOx storage amount, i.e. amount of NOx stored on NOx trap
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- 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
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- 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
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- 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
Definitions
- the present invention relates to an exhaust emission control device for a spark ignition type internal combustion engine.
- the three-way catalyst downstream of the engine exhaust passage with placing a three-way catalyst in the engine exhaust passage, when the air-fuel ratio of the inflowing exhaust gas lean occludes NO x in the exhaust gas, sky of the exhaust gas flowing ratio is arranged the NO x storage catalyst releases the NO x occluding
- a lean air-fuel ratio operation of burning fuel under a lean air-fuel ratio is performed
- an internal combustion engine that is switched to one of a mode and a theoretical air-fuel ratio operation mode in which combustion is performed under a theoretical air-fuel ratio (see, for example, Patent Document 1).
- the fuel consumption is lower when combustion is performed under a lean air-fuel ratio than when combustion is performed under a stoichiometric air-fuel ratio. Therefore, in such an internal combustion engine, Normally, combustion is performed under a lean air-fuel ratio in the widest possible operating range. However, when burning fuel under a lean air-fuel ratio when the engine load is increased is carried out, the higher the temperature of the NO x storage catalyst, for the result the NO x storage catalytic NO x storage ability is decreased NO x The purification rate will decrease. Therefore, in such an internal combustion engine, when the engine load increases, the operation mode is switched from the lean air-fuel ratio operation mode to the stoichiometric air-fuel ratio operation mode so that the NO x purification rate does not decrease.
- a three-way catalyst having an oxygen storage function is disposed in the engine exhaust passage, and the oxygen storage amount of the three-way catalyst is a value between zero and the maximum oxygen storage amount.
- Exhaust gas purification device for a spark ignition type internal combustion engine in which the air-fuel ratio in the combustion chamber is feedback controlled to the stoichiometric air-fuel ratio so that HC, CO and NO x contained in the exhaust gas are simultaneously purified in a three-way catalyst
- the air-fuel ratio in the combustion chamber is feedback-controlled to the stoichiometric air-fuel ratio, the amount of poisoning of the noble metal catalyst supported on the three-way catalyst is gradually increased, or the amount of noble metal catalyst covered is reduced.
- the lean ratio of the air-fuel ratio in the combustion chamber is set so that the oxygen storage amount of the three-way catalyst increases to the maximum oxygen storage amount.
- Theoretical air / fuel ratio The air-fuel ratio in the combustion chamber is kept lean even after the oxygen storage amount of the three-way catalyst reaches the maximum oxygen storage amount, and then returned to rich after the oxygen storage amount of the three-way catalyst reaches the maximum oxygen storage amount.
- FIG. 1 is an overall view of an internal combustion engine.
- FIG. 2 is a diagram schematically showing a surface portion of a three-way catalyst substrate.
- 3A and 3B are diagrams schematically showing a surface portion of the catalyst carrier of the exhaust purification catalyst.
- 4A, 4B and 4C are diagrams for explaining the purification action in the three-way catalyst.
- 5A, 5B and 5C are diagrams for explaining the poisoning action of the three-way catalyst.
- 6A, 6B, 6C, and 6D are diagrams showing the amount of poisoning in the three-way catalyst and the time during which the air-fuel ratio in the combustion chamber is maintained lean.
- 7A, 7B, 7C, and 7D are diagrams showing the poisoning amount in the three-way catalyst and the time during which the air-fuel ratio in the combustion chamber is rich.
- 8A, 8B and 8C are diagrams showing the fuel injection time and the like.
- 9A and 9B are flowcharts for controlling the operation of the engine.
- 10A and 10B are views for explaining an adsorption reaction and the like in the exhaust purification catalyst.
- 11A and 11B are diagrams for explaining the oxidation-reduction reaction in the exhaust purification catalyst.
- FIG. 12 is a diagram showing NO x release control.
- FIG. 13 is a diagram showing a map of the exhausted NO x amount NOXA.
- FIG. 14 is a diagram showing the NO x purification rate.
- FIG. 15 is a graph showing the relationship between the lean-to-rich air-fuel ratio switching period ⁇ TL and the NO x purification rate.
- FIG. 16 is a diagram showing the NO x purification rate.
- 17A and 17B are diagrams for explaining the NO x absorption ability and NO adsorption ability.
- 18A and 18B are diagrams for explaining the NO x absorption ability and NO adsorption ability.
- 19A, 19B and 19C are time charts showing changes in the air-fuel ratio of the exhaust gas discharged from the engine.
- FIG. 20 is a time chart showing changes in the air-fuel ratio of the exhaust gas flowing into the three-way catalyst and the exhaust purification catalyst.
- FIG. 21 is a diagram showing an operation region of the engine.
- FIG. 22 is a time chart showing changes in the fuel injection amount and the like during engine operation.
- FIG. 23 is a flowchart for performing engine operation control.
- FIG. 1 shows an overall view of a spark ignition internal combustion engine using gasoline as fuel.
- 1 is an engine body
- 2 is a cylinder block
- 3 is a cylinder head
- 4 is a piston
- 5 is a combustion chamber
- 6 is a spark plug
- 7 is an intake valve
- 8 is an intake port
- 9 is an exhaust valve
- Reference numeral 10 denotes an exhaust port.
- each cylinder injects fuel, i.e. gasoline, into an intake port 8 and an electronically controlled fuel injection valve 11 for injecting fuel, i.e. gasoline, into the combustion chamber 2.
- a pair of fuel injection valves consisting of an electronically controlled fuel injection valve 12 for this purpose.
- the intake port 8 of each cylinder is connected to a surge tank 14 via an intake branch pipe 13, and the surge tank 14 is connected to an air cleaner 16 via an intake duct 15.
- an intake air amount detector 17 and a throttle valve 18 driven by an actuator 18a are arranged.
- the exhaust port 10 of each cylinder is connected to an inlet of a three-way catalyst 20 having an oxygen storage function through an exhaust manifold 19, and an outlet of the three-way catalyst 20 is connected to an inlet of an exhaust purification catalyst 22 through an exhaust pipe 21. Connected. The outlet of the exhaust purification catalyst 22 is connected to the NO x selective reduction catalyst 23.
- the exhaust pipe 21 and the surge tank 14 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 24.
- An electronically controlled EGR control valve 25 is disposed in the EGR passage 24, and a cooling device 26 for cooling the exhaust gas flowing in the EGR passage 24 is disposed around the EGR passage 24.
- the engine cooling water is guided into the cooling device 26, and the exhaust gas is cooled by the engine cooling water.
- the electronic control unit 30 is composed of a digital computer and includes a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35 and an output port 36 connected to each other by a bidirectional bus 31. It comprises.
- An air-fuel ratio sensor 27 for detecting the air-fuel ratio of the exhaust gas discharged from the engine is attached upstream of the three-way catalyst 20, and the oxygen concentration in the exhaust gas is detected downstream of the three-way catalyst 20.
- an oxygen concentration sensor 28 is attached.
- Output signals of the air-fuel ratio sensor 27, the oxygen concentration sensor 28, and the intake air amount detector 17 are input to the input port 35 via corresponding AD converters 37, respectively.
- a load sensor 41 that generates an output voltage proportional to the depression amount L of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. Is done. Further, a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 30 ° is connected to the input port 35. On the other hand, the output port 36 is connected to the spark plug 6, the fuel injection valves 11 and 12, the throttle valve driving actuator 18 a and the EGR control valve 25 via the corresponding drive circuit 38.
- FIG. 2 schematically shows the surface portion of the base 50 of the three-way catalyst 20.
- an upper coat layer 51 and a lower coat layer 52 are formed on the catalyst carrier 50 in a laminated form.
- the upper coat layer 51 is made of rhodium Rh and cerium Ce
- the lower coat layer 52 is made of platinum Pt and cerium Ce.
- the amount of cerium Ce contained in the upper coat layer 51 is smaller than the amount of cerium Ce contained in the lower coat layer 52.
- the upper coat layer 51 can contain zirconia Zr soot
- the lower coat layer 52 can contain palladium Pd soot.
- FIG. 3A schematically shows the surface portion of the base 55 of the exhaust purification catalyst 22.
- a coat layer 56 is formed on the base 55 also in the exhaust purification catalyst 22.
- the coat layer 56 is made of, for example, an aggregate of powder
- FIG. 3B shows an enlarged view of the powder.
- noble metal catalysts 61 and 62 are supported on a catalyst carrier 60 made of alumina, for example, of this powder, and further, such as potassium K, sodium Na, and cesium Cs are supported on the catalyst carrier 60.
- a basic layer 63 including one is formed. Since the exhaust gas flows along the catalyst carrier 60, it can be said that the noble metal catalysts 61 and 62 are supported on the exhaust gas flow surface of the exhaust purification catalyst 22. Further, since the surface of the basic layer 63 is basic, the surface of the basic layer 63 is referred to as a basic exhaust gas flow surface portion.
- the noble metal catalyst 61 is made of platinum Pt and the noble metal catalyst 62 is made of rhodium Rh.
- any of the noble metal catalysts 61 and 62 can be made of platinum Pt.
- palladium Pd can be supported on the catalyst carrier 60, or palladium Pd can be supported instead of rhodium Rh. That is, the noble metal catalysts 61 and 62 supported on the catalyst carrier 60 are composed of at least one of platinum Pt, rhodium Rh and palladium Pd.
- the three-way catalyst 20 is in the exhaust gas when combustion is performed in the combustion chamber 5 under the stoichiometric air-fuel ratio, that is, when the air-fuel ratio of the exhaust gas discharged from the engine is the stoichiometric air-fuel ratio. It has simultaneously a function of reducing the harmful components HC, CO and NO x contained in the. Therefore, when combustion is performed in the combustion chamber 5 under the stoichiometric air-fuel ratio, harmful components HC, CO and NO x contained in the exhaust gas are purified by the three-way catalyst 20.
- the air-fuel ratio of the exhaust gas discharged from the combustion chamber 5 becomes almost the stoichiometric air-fuel ratio.
- the injection amount from the fuel injection valves 11 and 12 is feedback controlled based on the detection signal of the air-fuel ratio sensor 27 so that the air-fuel ratio of the exhaust gas discharged from the combustion chamber 5 fluctuates around the stoichiometric air-fuel ratio. Is done.
- FIG. 4A shows the time when the air-fuel ratio of the exhaust gas is slightly richer than the stoichiometric air-fuel ratio.
- oxygen O 2 held in the form of ceria by cerium Ce is released from the ceria, so that the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio on the surface of the platinum Pt.
- FIG. 4A shows the time when the air-fuel ratio of the exhaust gas is slightly richer than the stoichiometric air-fuel ratio.
- oxygen O 2 held in the form of ceria by cerium Ce is released from the ceria, so that the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio on the surface of the platinum Pt.
- FIG. 4A shows harmful components HC, CO and NO x contained in the exhaust gas are simultaneously purified in the three-way catalyst 20.
- FIG. 4B shows a case where the air-fuel ratio of the exhaust gas is slightly lean with respect to the stoichiometric air-fuel ratio. At this time, surplus oxygen O 2 with respect to the stoichiometric air-fuel ratio is taken into cerium Ce, so that the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio on the surface of platinum Pt.
- harmful components HC, CO and NO x contained in the exhaust gas are simultaneously purified in the three-way catalyst 20.
- the air-fuel ratio of the exhaust gas is changed so that the action of releasing oxygen O 2 from ceria and the action of taking in excess oxygen O 2 by cerium Ce can always occur, harmful components HC contained in the exhaust gas, CO and NO x are well purified in the three-way catalyst 20.
- the excess uptake action of oxygen O 2 in due to the release action and cerium Ce oxygen O 2 from ceria is so may occur normally, the oxygen storage amount in the three-way catalyst 20 as shown in FIG. 4C
- the air-fuel ratio in the combustion chamber 5 may be controlled so that the oxygen storage amount in the three-way catalyst 20 is preferably approximately half of the maximum oxygen storage amount so as to be a value between zero and the maximum oxygen storage amount. It will be.
- the amount of oxygen O 2 released from ceria and the amount of excess oxygen O 2 taken in by cerium Ce can be calculated from the difference between the actual air-fuel ratio and the stoichiometric air-fuel ratio of the exhaust gas and the intake air amount. Therefore, the oxygen storage amount of the three-way catalyst 20 can be calculated.
- the air-fuel ratio (A / F) in the combustion chamber 5 is theoretically increased.
- the air-fuel ratio (A / F) in the combustion chamber 5 is slightly less than the stoichiometric air-fuel ratio. Just lean. In this way, the oxygen storage amount in the three-way catalyst 20 is maintained at about half of the maximum oxygen storage amount, and therefore the harmful components HC, CO and NO x contained in the exhaust gas are well purified in the three-way catalyst 20.
- the air-fuel ratio in the combustion chamber 5 actually fluctuates around the theoretical air-fuel ratio. That is, in the embodiment according to the present invention, the air-fuel ratio in the combustion chamber 5 is feedback-controlled to the stoichiometric air-fuel ratio so that the oxygen storage amount in the three-way catalyst 20 becomes a value between zero and the maximum oxygen storage amount. As a result, HC, CO and NO x contained in the exhaust gas are simultaneously purified in the three-way catalyst 20.
- FIGS. 5A and 5B schematically show the poisoning action on the noble metal catalyst Pt as an example.
- the air-fuel ratio of the exhaust gas becomes rich, as shown in FIG. 5A, hydrocarbon HC and carbon C adhere to the surface of the noble metal catalyst Pt.
- the surface of the noble metal catalyst Pt 1 It will be poisoned by carbon C.
- the NO x purification rate decreases.
- the air-fuel ratio (A / F) in the combustion chamber 5 that is, the base air-fuel ratio (A / F) b is the theoretical sky. It is considerably lean with respect to the fuel ratio. That is, the lean degree of the air-fuel ratio in the combustion chamber 5 is made larger than when the air-fuel ratio is feedback controlled to the stoichiometric air-fuel ratio.
- the oxygen storage amount in the three-way catalyst 20 reaches the maximum oxygen storage amount, and the air-fuel ratio in the combustion chamber 5 is maintained lean even after the oxygen storage amount reaches the maximum oxygen storage amount.
- the air-fuel ratio (A / F) in the combustion chamber 5 is made rich. As described above, when the air-fuel ratio in the combustion chamber 5 is maintained lean even after the oxygen storage amount in the three-way catalyst 20 reaches the maximum oxygen storage amount, the poisoning of the noble metal catalyst Pt is recovered.
- the amount of hydrocarbons HC and carbon C adhering to the surface of the noble metal catalyst Pt during the period when the air-fuel ratio (A / F) in the combustion chamber 5 is rich is reduced.
- the number increases, it is necessary to increase the time ⁇ TL during which the air-fuel ratio (A / F) in the combustion chamber 5 is maintained lean. Therefore, in the present invention, when recovering the poisoning of the noble metal catalyst Pt, the lean degree of the air-fuel ratio (A / F) in the combustion chamber 5 is compared with that when the air-fuel ratio is feedback controlled to the stoichiometric air-fuel ratio.
- the air-fuel ratio (A / F) in the combustion chamber 5 is maintained lean even after the oxygen storage amount of the three-way catalyst 20 reaches the maximum oxygen storage amount and then returned to rich.
- the time ⁇ TL during which the air-fuel ratio (A / F) in the combustion chamber 5 is kept lean is made longer as the poisoning amount of the noble metal catalyst when the air-fuel ratio (A / F) in the combustion chamber 5 is richer is larger. ing.
- FIG. 6A shows the poisoning amount of the noble metal catalyst by the hydrocarbon HC and carbon C and the fuel injection amount Q when the air-fuel ratio (A / F) in the combustion chamber 5 is kept constant at a constant rich air-fuel ratio.
- FIG. 6B shows the amount of poisoning of the noble metal catalyst by hydrocarbons HC and carbon C when the air-fuel ratio (A / F) in the combustion chamber 5 is kept at a constant rich air-fuel ratio for a fixed period.
- the relationship with the temperature TC of the three-way catalyst 20 is shown.
- FIG. 6C shows the relationship between the air-fuel ratio lean time ⁇ TL required for recovery of poisoning of the noble metal catalyst and the fuel injection amount Q
- FIG. 6D shows the air-fuel ratio required for recovery of poisoning of the noble metal catalyst.
- the relationship between the lean time ⁇ TL and the temperature TC of the three-way catalyst 20 is shown.
- the amount of hydrocarbon HC in the exhaust gas when the air-fuel ratio (A / F) in the combustion chamber 5 is a constant rich air-fuel ratio for a certain period is the fuel injection quantity Q.
- the amount of hydrocarbons HC and carbon C adhering to the surface of the noble metal catalyst Pt during the rich period increases as the fuel injection amount Q increases, that is, the engine load increases. It increases. Therefore, as described above, as shown in FIG. 6C, when the poisoning of the noble metal catalyst is recovered, the lean time ⁇ TL of the air-fuel ratio is lengthened as the fuel injection amount Q increases, that is, as the engine load increases.
- the amount of hydrocarbon HC in the exhaust gas when the air-fuel ratio (A / F) in the combustion chamber 5 is kept at a constant rich air-fuel ratio for a fixed period is the three-way catalyst. Accordingly, the amount of hydrocarbons HC and carbon C adhering to the surface of the noble metal catalyst Pt during the rich period decreases as the temperature TC of the three-way catalyst 20 increases. Therefore, as shown in FIG. 6D, when recovering the poisoning of the noble metal catalyst, the higher the temperature TC of the three-way catalyst 20, the shorter the lean time ⁇ TL of the air-fuel ratio.
- the surface of the noble metal catalyst Pt 2 is not only poisoned by hydrocarbons HC and carbon C but also poisoned by sulfur S and phosphorus P as shown in FIG. 5B. In this case as well, the NO x purification rate decreases.
- these sulfur S and phosphorus P are reduced and released by HC and CO contained in the exhaust gas as shown in FIG. 5B. Poisoning by phosphorus P is recovered.
- the air-fuel ratio in the combustion chamber 5 is feedback-controlled to the stoichiometric air-fuel ratio, the air-fuel ratio of the exhaust gas is made rich in a short cycle.
- the air-fuel ratio (A / F) in the combustion chamber 5 is made rich relative to the stoichiometric air-fuel ratio as shown in FIG. 5C.
- the rich degree ⁇ (A / F) r of the air-fuel ratio in the combustion chamber 5 at this time is made larger than when the air-fuel ratio is feedback controlled to the stoichiometric air-fuel ratio.
- the oxygen storage amount in the three-way catalyst 20 decreases to zero, and the air-fuel ratio in the combustion chamber 5 is maintained rich even after the oxygen storage amount becomes zero.
- the air-fuel ratio (A / F) in the combustion chamber 5 is made lean.
- the rich degree ⁇ (A / F) r when the air-fuel ratio in the combustion chamber 5 is kept lean to be returned to rich to recover poisoning by sulfur S or phosphorus P is: After the air-fuel ratio is increased so that the oxygen storage amount of the three-way catalyst 20 is reduced to zero, compared to when the stoichiometric air-fuel ratio is feedback-controlled, and after the oxygen storage amount of the three-way catalyst 20 reaches zero However, after the air-fuel ratio in the combustion chamber 5 is maintained rich, it is returned to lean. Note that the amount of poisoning due to sulfur S or phosphorus P increases as the time ⁇ TL for maintaining the air-fuel ratio (A / F) in the combustion chamber 5 lean is increased.
- the time ⁇ TR for making A / F) rich is lengthened.
- FIG. 7A shows the relationship between the amount of poisoning caused by sulfur S and phosphorus P and the time ⁇ TL during which the air-fuel ratio in the combustion chamber 5 is kept lean
- FIG. 7B shows the amount of poisoning caused by sulfur S and phosphorus P.
- the relationship with the temperature TC of the three-way catalyst 20 is shown
- FIG. 7C shows the relationship between the rich time ⁇ TR of the air-fuel ratio necessary for recovery of poisoning by sulfur S and phosphorus P and the time ⁇ TL during which the air-fuel ratio in the combustion chamber 5 is kept lean. Shows the relationship between the rich time ⁇ TR of the air-fuel ratio necessary for recovery of poisoning by sulfur S and phosphorus P and the temperature TC of the three-way catalyst 20.
- the poisoning amount due to sulfur S and phosphorus P increases as the time ⁇ TL for maintaining the air-fuel ratio in the combustion chamber 5 lean is increased. Therefore, as described above, as shown in FIG. 7C, when the poisoning due to sulfur S or phosphorus P is recovered, the air-fuel ratio rich time ⁇ TR increases as the air-fuel ratio lean time ⁇ TL in the combustion chamber 5 increases. Is lengthened.
- the poisoning amount due to sulfur S and phosphorus P slightly decreases as the temperature TC of the three-way catalyst 20 increases. Therefore, as shown in FIG. 7D, when recovering the poisoning by sulfur S or phosphorus P, the air-fuel rich time ⁇ TR is slightly shortened as the temperature TC of the three-way catalyst 20 increases.
- the fuel injection amount WT from the fuel injection valves 11 and 12 for obtaining the rich degree ⁇ (A / F) r required at the time of recovery from poisoning is the required load L and the engine speed N.
- the function is stored in advance in the ROM 32 in the form of a map as shown in FIG. 8A.
- the optimal lean time ⁇ TL at the time of recovery from poisoning is stored in advance in the ROM 32 as a function of the fuel injection amount Q and the temperature TC of the three-way catalyst 20 in the form of a map as shown in FIG.
- the optimal rich time ⁇ TR at the time of recovery is stored in advance in the ROM 32 in the form of a map as shown in FIG. 8C as a function of the lean time ⁇ TL and the temperature TC of the three-way catalyst 20.
- the poisoning amount of the noble metal catalyst by hydrocarbon HC or carbon C increases as the fuel injection amount Q increases, that is, as the engine load increases.
- the poisoning amount of the noble metal catalyst by hydrocarbon HC or carbon C decreases as the temperature TC of the three-way catalyst 20 increases, that is, as the engine load increases. That is, during engine high load operation, the fuel injection amount Q increases and the poisoning amount increases, but the three-way catalyst 20 becomes a state where the temperature TC becomes high and the poisoning amount decreases. Sometimes the amount of poisoning does not increase that much.
- the three-way catalyst 20 is in a state where the temperature TC becomes high and the poisoning amount increases, but at this time because the fuel injection amount Q is small and the poisoning amount decreases. However, the amount of poisoning does not increase that much.
- the poisoning amount of the noble metal catalyst by hydrocarbon HC and carbon C is the highest during the medium load operation when the fuel injection amount Q is relatively large and the temperature TC of the three-way catalyst 20 is difficult to be relatively high. is there. Therefore, in the embodiment shown in FIG.
- the engine operating state is such that the poisoning amount of the noble metal catalyst supported on the three-way catalyst gradually increases. In other words, at the time of engine load operation, the engine operation capable of recovering poisoning of the three-way catalyst 20 is performed.
- step 70 it is judged if the engine is in a medium load operation or not.
- the routine proceeds to step 71 where the air-fuel ratio in the combustion chamber 5 is fed back to the stoichiometric air-fuel ratio so that the oxygen storage amount of the three-way catalyst 20 becomes a value between zero and the maximum oxygen storage amount. Be controlled.
- step 72 the fuel injection amount WT, the lean time ⁇ TL and the rich time ⁇ TR are calculated from FIGS. 8A, 8B and 8C, respectively. Based on the fuel injection amount WT, the lean time ⁇ TL, and the rich time ⁇ TR, the lean / rich control capable of recovery from poisoning shown in FIG. 5C is performed.
- FIG. 9B shows an embodiment in which the engine operation is performed in which the poisoning recovery of the three-way catalyst 20 can be performed when the poisoning amount of the noble metal catalyst exceeds the allowable amount during the medium load operation. That is, referring to FIG. 9B, first, at step 75, it is judged if the engine medium load operation is being performed. When it is not during engine load operation, the routine proceeds to step 76, where the air-fuel ratio in the combustion chamber 5 is fed back to the stoichiometric air-fuel ratio so that the oxygen storage amount of the three-way catalyst 20 becomes a value between zero and the maximum oxygen storage amount. Be controlled. On the other hand, when it is determined at step 75 that the engine is in a medium load operation, the routine proceeds to step 77 where the poisoning amount of the noble metal catalyst by hydrocarbon HC or carbon C is integrated.
- step 78 whether the integrated value PX of poisoning amount of the noble metal catalyst by the hydrocarbon HC and carbon C has exceeded the allowable amount PX O is determined. Proceed to step 76 when the integrated value PX of poisoning amount of the noble metal catalyst does not exceed the allowable amount PX O, so that the oxygen storage amount of the three-way catalyst 20 becomes a value between zero and the maximum oxygen storage amount
- the air fuel ratio in the combustion chamber 5 is feedback controlled to the stoichiometric air fuel ratio. In contrast, each of FIGS.
- step 79 when the integrated value PX of poisoning amount of the noble metal catalyst is determined to have exceeded the allowable amount PX O at step 78, the fuel injection amount WT, lean time ⁇ TL and rich time ⁇ TR are calculated, and based on these fuel injection amount WT, lean time ⁇ TL, and rich time ⁇ TR, lean / rich control capable of recovery from poisoning shown in FIG. 5C is performed.
- the three-way catalyst 20 having an oxygen storage function is arranged in the engine exhaust passage so that the oxygen storage amount of the three-way catalyst 20 is a value between zero and the maximum oxygen storage amount.
- an exhaust emission control device for a spark ignition type internal combustion engine in which the air-fuel ratio in the combustion chamber 5 is feedback-controlled to the stoichiometric air-fuel ratio so that HC, CO and NO x contained in the exhaust gas are simultaneously purified in the three-way catalyst 20
- the air-fuel ratio in the combustion chamber 5 is feedback-controlled to the stoichiometric air-fuel ratio
- the poisoning amount of the noble metal catalyst supported on the three-way catalyst 20 gradually increases, or the noble metal catalyst
- the degree of leanness of the air-fuel ratio in the combustion chamber 5 so that the oxygen storage amount of the three-way catalyst 20 increases to the maximum oxygen storage amount when the poisoning amount of the gas exceeds a predetermined allowable amount
- the air-fuel ratio The air-fuel ratio is increased as compared to when the air-fuel ratio is feedback
- the new the NO x purification method the use of the adsorption of NO, following this new the NO x purification method, referred to as the NO x purification method of adsorbing NO use. Therefore, first, the the NO x purification process of the adsorption NO utilized will be described with reference to FIGS. 10A and 10B.
- FIG. 10A and 10B show an enlarged view of FIG. 3B, that is, a surface portion of the catalyst carrier 60 of the exhaust purification catalyst 22.
- FIG. FIG. 10A shows when the air-fuel ratio of the exhaust gas is lean
- FIG. 10B shows when the air-fuel ratio of the exhaust gas is made rich.
- NO contained in the exhaust gas is dissociated and adsorbed on the surface of the platinum Pt 61 as shown in FIG. 10A.
- the adsorption amount of NO on the surface of the platinum Pt 61 increases with the passage of time. Therefore, the adsorption amount of NO on the exhaust purification catalyst 22 increases with the passage of time.
- the exhaust gas flowing into the exhaust purification catalyst 22 contains a large amount of carbon monoxide CO.
- carbon monoxide CO As carbon monoxide CO is shown in FIG. 10B, it reacts with NO that dissociative adsorption onto the surface of the platinum Pt 61, the NO is a reducing intermediate NCO in N 2, and the other is on the one hand .
- the reducing intermediate NCO continues to be held or adsorbed on the surface of the basic layer 63 for a while after the generation. Therefore, the amount of the reducing intermediate NCO retained or adsorbed on the surface of the basic layer 63 gradually increases with time.
- the reducing intermediate NCO reacts with NO x contained in the exhaust gas, whereby NO x contained in the exhaust gas is purified.
- NO contained in the exhaust gas at this time is NO in FIG. 11A.
- NO 2 on the platinum Pt 61 is absorbed into the basic layer 63 and diffused into the basic layer 63 in the form of nitrate ions NO 3 ⁇ , It becomes nitrate.
- NO x in the exhaust gas is absorbed in the basic layer 63 in the form of nitrate.
- the air-fuel ratio in the combustion chamber 5 is made rich, that is, when the air-fuel ratio of the exhaust gas is made rich, the oxygen concentration in the exhaust gas flowing into the exhaust purification catalyst 22 decreases.
- the reaction proceeds in the reverse direction (NO 3 ⁇ ⁇ NO 2 ), and thus the nitrate absorbed in the basic layer 63 is successively converted to nitrate ions NO 3 ⁇ and forms NO 2 as shown in FIG. 11B. Is released from the basic layer 63.
- the released NO 2 is then reduced by the hydrocarbons HC and CO contained in the exhaust gas.
- the exhaust purification catalyst 22 When the air-fuel ratio of the exhaust gas flowing into the catalyst 22 is lean, NO x is stored, and when the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 22 becomes rich, the stored NO x is released.
- NO x in the exhaust gas begins to be absorbed by the exhaust purification catalyst 22.
- the NO x storage capability of the exhaust purification catalyst 22 is saturated during that time, and as a result, the exhaust purification catalyst 22 cannot store NO x. End up. Therefore, NO x storage capacity of the exhaust purification catalyst 22 is temporarily made rich the air-fuel ratio in the combustion chamber 5 prior to saturated, NO x is made to release from the exhaust purification catalyst 22 by it.
- Figure 12 shows the NO x releasing control in a case which is adapted to absorb the NO x in the exhaust purification catalyst.
- the air-fuel ratio (A / F) in the combustion chamber 5 is temporarily increased. To be rich.
- the air-fuel ratio (A / F) in the combustion chamber 5 is made rich, that is, when the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 22 is made rich, combustion is performed under the lean air-fuel ratio.
- NO x stored in the exhaust purification catalyst 22 is released from the exhaust purification catalyst 22 at once and reduced. As a result, NO x is purified.
- Occluded amount of NO x ⁇ NOX is calculated from the amount of NO x exhausted from the engine, for example. Is stored in advance in the ROM32 in the form of a map as shown in FIG. 13 as a function of the discharge amount of NO x NOXA is required load L and engine speed N which is discharged from the engine per unit time in this embodiment of the present invention, The occluded NO x amount ⁇ NOX is calculated from this exhausted NO x amount NOXA. In this case, the period during which the air-fuel ratio in the combustion chamber 5 is made rich is usually 1 minute or more.
- Figure 14 shows the NO x purification rate when so as to purify NO x by absorbing and releasing action of Figure 12 as shown, NO x of the exhaust purification catalyst 22.
- the horizontal axis in FIG. 14 indicates the catalyst temperature TC of the exhaust purification catalyst 22.
- reduced catalyst temperature TC When it extremely high NO x purification rate is obtained catalyst temperature TC becomes a high temperature of at least 400 ° C. when the 300 ° C. of 400 ° C. the NO x purification rate To do. As described above, the NO x purification rate decreases when the catalyst temperature TC exceeds 400 ° C.
- the NO x is not easily absorbed when the catalyst temperature TC exceeds 400 ° C., and the nitrate is thermally decomposed to form NO 2 . This is because it is discharged from the exhaust purification catalyst 22. That is, as long as NO x is absorbed in the form of nitrate, it is difficult to obtain a high NO x purification rate when the catalyst temperature TC is high.
- the amount of NO adsorbed on the surface of platinum Pt 61 is hardly affected by the temperature TC of the exhaust purification catalyst 22. Therefore, if NO x contained in the exhaust gas is adsorbed on the surface of platinum Pt 61 without being absorbed in the form of nitrate in the exhaust purification catalyst 22, the stored amount of NO x is the exhaust purification catalyst 22. It is hardly affected by the temperature TC. By the way, as described above, after a while from the start of the lean air-fuel ratio combustion, the NO x absorption action to the exhaust purification catalyst 22 is started.
- the purification process of the NO x which is adapted to purify NO x is a the NO x purification method of adsorbing NO use explained with reference to FIGS. 10A and 10B.
- the period ⁇ TL FIGS. 10A and 10B.
- FIG. 16 shows the NO x purification rate when NO x is purified by the NO x purification method using adsorption NO. As shown in FIG. 16, in this case, it is understood that the NO x purification rate does not decrease even when the temperature TC of the exhaust purification catalyst 22 is increased to a high temperature of 400 ° C. or higher.
- the fuel injection valves 11 and 12 follow the fuel injection amount WT calculated from the map shown in FIG. 8A and the lean time ⁇ TL and rich time ⁇ TR calculated from the maps shown in FIGS. 8B and 8C, respectively.
- the NO x purification action is performed by the NO x purification method using adsorbed NO.
- the temperature TC of the exhaust purification catalyst 22 becomes high, a high NO x purification rate is obtained and the ternary is achieved.
- the poisoning of the catalyst 20 can be recovered.
- the exhaust purification catalyst 22 is disposed in the engine exhaust passage downstream of the three-way catalyst 20, and the noble metal catalysts 61 and 62 are supported on the exhaust gas flow surface of the exhaust purification catalyst 22.
- a basic exhaust gas flow surface portion is formed around the noble metal catalysts 61 and 62, and the exhaust purification catalyst 22 has a period within a predetermined range of the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 22.
- FIG. 17A shows the NO x absorption ability and the NO adsorption ability when NO x is purified using the NO x storage / release action to the exhaust purification catalyst 22, as shown in FIG.
- the vertical axis in FIG. 17A shows the storage capacity of the NO x which is the sum of the absorption capacity and NO adsorption capacity NO x
- the horizontal axis shows the temperature TC of the exhaust purification catalyst 22.
- the amount of NO quantity of NO contained in the exhaust gas is adsorbed on the surface of The more the more the platinum Pt 61 as compared to the amount of O 2 becomes more than the amount of O 2, on the contrary As the amount of O 2 contained in the exhaust gas increases as compared with the amount of NO, the amount of NO adsorbed on the surface of platinum Pt 61 decreases as compared with the amount of O 2 . Therefore, as shown in FIG. 18A, the NO adsorption capacity of the exhaust purification catalyst 22 decreases as the oxygen concentration in the exhaust gas increases.
- FIG. 18B shows the NO x absorption capacity of the exhaust purification catalyst 22 increases as the oxygen concentration in the exhaust gas increases.
- region X is obtained under the lean air-fuel ratio when NO x is purified by using the NO x storage / release action to exhaust purification catalyst 22, as shown in FIG. It shows when combustion is taking place. At this time, it can be seen that the NO adsorption capacity is low and the NO x absorption capacity is high.
- FIG. 17A described above shows the NO adsorption capacity and the NO x absorption capacity at this time.
- the oxygen concentration in the exhaust gas may be decreased.
- the NO x absorption capacity decreases.
- FIG. 17B shows the NO x absorption ability and NO adsorption ability when the oxygen concentration in the exhaust gas is lowered to the region Y in FIGS. 18A and 18B.
- FIG. 19A shows the air-fuel ratio (A / F) in the combustion chamber 5 when NO x is purified by using the NO x storage / release action to the exhaust purification catalyst 22, as in the case shown in FIG. Shows changes.
- (A / F) b represents the base air-fuel ratio
- ⁇ (A / F) r represents the richness of the air-fuel ratio
- ⁇ T represents the switching of the air-fuel ratio from lean to rich.
- FIG. 19B shows the change in the air-fuel ratio (A / F) in the combustion chamber 5 when NO x is purified by utilizing the NO adsorption action.
- (A / F) b indicates the base air-fuel ratio
- ⁇ (A / F) r indicates the richness of the air-fuel ratio
- ⁇ T indicates the rich period of the air-fuel ratio.
- FIG. 19C shows a change in the air-fuel ratio in the combustion chamber 5 when the air-fuel ratio in the combustion chamber 5 is feedback-controlled to the stoichiometric air-fuel ratio.
- FIG. 20 shows the change in the air-fuel ratio (A / F) in the combustion chamber 5 when the NO x is purified by utilizing the NO adsorption action and the exhaust purification catalyst 22 as shown in FIG. 19B. It shows the change in the air-fuel ratio (A / F) in of the inflowing exhaust gas.
- the air-fuel ratio (A / F) in the combustion chamber 5 is made rich, the oxygen stored in the three-way catalyst 20 is released and maintained at the stoichiometric air-fuel ratio for a time t1, Thereby, HC, CO and NO x are simultaneously reduced. During this time, as shown in FIG.
- the air-fuel ratio (A / F) in of the exhaust gas flowing into the exhaust purification catalyst 22 is maintained at the stoichiometric air-fuel ratio.
- the air-fuel ratio (A / F) in of the exhaust gas flowing into the exhaust purification catalyst 22 becomes rich during the time t2.
- NO dissociated and adsorbed on the surface of platinum Pt 61 becomes N 2 on the one hand and a reducing intermediate NCO on the other hand.
- the reducing intermediate NCO continues to be held or adsorbed on the surface of the basic layer 63 for a while after the generation.
- An engine medium load operation region II located between the load operation regions III is set in advance.
- the vertical axis L in FIG. 21 indicates the required load
- the horizontal axis N indicates the engine speed.
- the engine low load operating region I as shown in FIG. 19A, purification action of the NO x row which is adapted by using the storage and release action of the NO x purifying NO x in the exhaust gas purifying catalyst 22
- the middle-medium-load operation region II as shown in FIG.
- the NO x purification action is performed in which NO x is purified using the NO adsorption action.
- the air-fuel ratio in the combustion chamber 5 is feedback-controlled to the stoichiometric air-fuel ratio.
- combustion should be performed in the combustion chamber 5 with the base air-fuel ratio lean, and NO x should be released from the exhaust purification catalyst 22.
- the air-fuel ratio in the combustion chamber 5 is made rich, and in the predetermined engine high load operation region III, the air-fuel ratio in the combustion chamber 5 is feedback-controlled to the stoichiometric air-fuel ratio, so that the predetermined engine load operation region II is determined.
- combustion in the combustion chamber 5 is performed under a base air-fuel ratio smaller than the base air-fuel ratio in the engine low-load operation region I, and the air-fuel ratio rich for NO x release in the engine low-load operation region I
- the air-fuel ratio in the combustion chamber 5 is made rich with a cycle shorter than the cycle.
- the base air-fuel ratio in the engine medium load operation region II is an intermediate value between the base air fuel ratio and the stoichiometric air fuel ratio in the engine low load operation region I.
- the richness of the air-fuel ratio when the air-fuel ratio in the combustion chamber 5 is made rich is the richness of the air-fuel ratio in the engine low load operation region I when the air-fuel ratio in the combustion chamber 5 is made rich. Smaller than the degree.
- FIG. 22 shows changes in the fuel injection amount into the combustion chamber 5, changes in the air-fuel ratio (A / F) in the combustion chamber 5, and changes in the stored NO x amount ⁇ NOX.
- MAXI indicates the allowable NO x storage amount.
- the air-fuel ratio in the combustion chamber 5 is temporarily made rich every time the lean time ⁇ TL elapses. At this time, NO x purification action using adsorbed NO is performed, and poisoning of the three-way catalyst 20 is recovered.
- NO x is occluded in the exhaust purification catalyst 22 and switched to the NO x purification method by feedback control to the stoichiometric air-fuel ratio shown in FIG. 19C, NO by feedback control to the stoichiometric air-fuel ratio is switched.
- part of the NO x stored in the exhaust purification catalyst 22 is released without being reduced. Therefore, in the embodiment according to the present invention, as shown in FIG. 22, when the engine operating state shifts from the engine middle load operation region II to the engine high load operation region III, the air-fuel ratio (A / F) is temporarily made rich.
- the fuel injection valves 11 and 12 are controlled based on the output signal of the air-fuel ratio sensor 27 so that the oxygen storage amount of the three-way catalyst 20 becomes an intermediate value between zero and the maximum oxygen storage amount.
- the injection amount is feedback-controlled.
- the air-fuel ratio in the combustion chamber 5 is controlled to the stoichiometric air-fuel ratio, so that harmful components HC, CO and NO x contained in the exhaust gas are simultaneously purified in the three-way catalyst 20.
- ammonia may be generated at this time.
- this ammonia is adsorbed by the NO x selective reduction catalyst 23.
- the ammonia adsorbed on the NO x selective reduction catalyst 23 reacts with NO x contained in the exhaust gas and is used to reduce NO x .
- FIG. 23 shows an operation control routine. This routine is executed by interruption every predetermined time.
- step 80 it is judged if the operating state of the engine is an engine high load operating region III shown in FIG.
- the process proceeds to step 81, the discharge amount of NO x NOXA per unit time from the map shown in FIG. 13 is calculated.
- occluded amount of NO x ⁇ NOX is calculated by adding the discharge amount of NO x NOXA to ⁇ NOX step 82.
- step 83 it is judged if the engine operating state is an engine low load operating region I shown in FIG. When the engine operating state is the engine low load operation region I shown in FIG.
- step 84 whether the NO x storage amount ⁇ NOX has exceeded the allowable the NO x storage amount MAXI is determined, when the NO x storage amount ⁇ NOX does not exceed the allowable the NO x storage amount MAXI, the routine proceeds to step 85, the combustion The air-fuel ratio in the chamber 5 is set to a lean air-fuel ratio that is predetermined according to the operating state of the engine. At this time, combustion is performed with the base air-fuel ratio lean.
- step 86 when it is determined in step 84 that the NO x storage amount ⁇ NOX exceeds the allowable NO x storage amount MAXI, the routine proceeds to step 86, where the air-fuel ratio in the combustion chamber 5 is temporarily made rich, and ⁇ NOX. Is cleared. At this time, NO x stored in the exhaust purification catalyst 22 is released from the exhaust purification catalyst 22.
- step 83 when it is determined in step 83 that the engine operating state is not the engine low load operating region I shown in FIG. 21, that is, the engine operating state is the engine medium load operating region II shown in FIG.
- the routine proceeds to step 87, where it is determined whether or not the engine operating state has shifted from the engine low load operation region I to the engine middle load operation region II.
- step 88 the routine proceeds to step 88 where the air-fuel ratio in the combustion chamber 5 is temporarily made rich.
- the routine proceeds to step 89.
- step 89 the fuel injection amount WT, the lean time ⁇ TL, and the rich time ⁇ TR are calculated from FIGS. 8A, 8B, and 8C, respectively. Based on the fuel injection amount WT, the lean time ⁇ TL, and the rich time ⁇ TR, the values shown in FIG. Lean / rich control that can recover poisoning is performed. At this time, NO x purification action utilizing adsorption of NO takes place.
- step 80 when it is determined in step 80 that the engine operating state is the engine high load operating region III shown in FIG. 21, the routine proceeds to step 90, where the engine operating state is now changed from the engine medium load operating region II. It is determined whether or not the engine has shifted to the high engine load operation region III. Now, when the engine operating state shifts from the engine middle load operation region II to the engine high load operation region III, the routine proceeds to step 91 where the air-fuel ratio in the combustion chamber 5 is temporarily made rich. On the other hand, when the engine operating state has already shifted from the engine middle load operation region II to the engine high load operation region III, the routine proceeds to step 92. In step 92, the air-fuel ratio in the combustion chamber 5 is feedback-controlled to the stoichiometric air-fuel ratio.
Abstract
Description
図1を参照すると、1は機関本体、2はシリンダブロック、3はシリンダヘッド、4はピストン、5は燃焼室、6は点火栓、7は吸気弁、8は吸気ポート、9は排気弁、10は排気ポートを夫々示す。図1に示されるように、各気筒は燃焼室2内に向けて燃料、即ちガソリンを噴射するための電子制御式燃料噴射弁11と、吸気ポート8内に向けて燃料、即ちガソリンを噴射するための電子制御式燃料噴射弁12からなる一対の燃料噴射弁を具備する。各気筒の吸気ポート8は吸気枝管13を介してサージタンク14に連結され、サージタンク14は吸気ダクト15を介してエアクリーナ16に連結される。吸気ダクト15内には吸入空気量検出器17と、アクチュエータ18aより駆動されるスロットル弁18とが配置される。
図23を参照すると、まず初めにステップ80において、機関の運転状態が図21に示される機関高負荷運転領域IIIであるか否かが判別される。機関の運転状態が機関高負荷運転領域IIIでないときにはステップ81に進み、図13に示すマップから単位時間当りの排出NOx量NOXAが算出される。次いでステップ82ではΣNOXに排出NOx量NOXAを加算することによって吸蔵NOx量ΣNOXが算出される。次いで、ステップ83では、機関の運転状態が図21に示される機関低負荷運転領域Iであるか否かが判別される。機関の運転状態が図21に示される機関低負荷運転領域Iであるときにはステップ84に進む。
ステップ89に進む。ステップ89では、図8A,8Bおよび8Cから夫々、燃料噴射量WT、リーン時間ΔTLおよびリッチ時間ΔTRが算出され、これら燃料噴射量WT、リーン時間ΔTLおよびリッチ時間ΔTRに基づいて、図5Cに示される被毒回復が可能なリーン・リッチ制御が行われる。このとき、NOの吸着を利用したNOx浄化作用が行われる。
6 点火栓
11,12 燃料噴射弁
14 サージタンク
19 排気マニホルド
20 三元触媒
22 排気浄化触媒
Claims (8)
- 機関排気通路内に酸素貯蔵機能を有する三元触媒を配置し、該三元触媒の酸素貯蔵量が零と最大酸素貯蔵量との間の値となるように燃焼室内における空燃比を理論空燃比にフィードバック制御して排気ガス中に含まれるHC,COおよびNOxを該三元触媒において同時に浄化するようにした火花点火式内燃機関の排気浄化装置において、燃焼室内における空燃比が理論空燃比にフィードバック制御されると三元触媒に担持されている貴金属触媒の被毒量が次第に増大していく機関運転状態になったとき、又は該貴金属触媒の被毒量が増大して予め定められた許容量を超えたときに、三元触媒の酸素貯蔵量が最大酸素貯蔵量まで増大するように、燃焼室内における空燃比のリーンの度合いを、該空燃比が理論空燃比にフィードバック制御されているときに比べて大きくすると共に三元触媒の酸素貯蔵量が最大酸素貯蔵量に達した後も燃焼室内における空燃比をリーンに維持してその後にリッチに戻し、このとき燃焼室内における空燃比がリーンに維持される時間を、燃焼室内における空燃比がリッチのときの上記貴金属触媒の被毒量が大きいほど長くするようにした火花点火式内燃機関の排気浄化装置。
- 上記燃焼室内における空燃比がリーンに維持される時間は、機関負荷が高くなるほど長くされる請求項1に記載の火花点火式内燃機関の排気浄化装置。
- 上記燃焼室内における空燃比がリーンに維持される時間は、三元触媒の温度が高いほど短くされる請求項2に記載の火花点火式内燃機関の排気浄化装置。
- 燃焼室内における空燃比がリーンに維持された後にリッチに戻されたときのリッチ度合いは、三元触媒の酸素貯蔵量が零まで低下するように、該空燃比が理論空燃比にフィードバック制御されているときに比べて大きくすると共に三元触媒の酸素貯蔵量が零に達した後も燃焼室内における空燃比をリッチに維持した後にリーンに戻すようにした請求項1に記載の火花点火式内燃機関の排気浄化装置。
- 貴金属触媒の被毒量が次第に増大していく機関運転状態は、機関中負荷運転状態である請求項1に記載の火花点火式内燃機関の排気浄化装置。
- 上記三元触媒下流の機関排気通路内に排気浄化触媒を配置されており、該排気浄化触媒の排気ガス流通表面上には貴金属触媒が担持されていると共に該貴金属触媒周りには塩基性の排気ガス流通表面部分が形成されており、該排気浄化触媒は、排気浄化触媒に流入する排気ガスの空燃比を予め定められた範囲内の周期でもってリーンからリッチに一時的に切換えると排気ガス中に含まれるNOxを還元する性質を有すると共に、該リーンからリッチへの切換え周期を該予め定められた範囲よりも長くすると排気ガス中に含まれるNOxの吸収量が増大する性質を有しており、機関運転時において燃焼室内における空燃比が該予め定められた範囲内の周期でもってリーンからリッチに一時的に切換えられたときに該排気浄化触媒において排気ガス中に含まれるNOxが浄化される請求項1に記載の火花点火式内燃機関の排気浄化装置。
- 機関の運転領域が、機関低負荷運転側の予め定められた機関低負荷運転領域と、機関高負荷運転側の予め定められた機関高負荷運転領域と、該機関低負荷運転領域および該機関高負荷運転領域の間に位置する予め定められた機関中負荷運転領域からなり、該予め定められた機関低負荷運転領域では燃焼室内においてベース空燃比がリーンのもとで燃焼が行われると共に排気浄化触媒からNOxを放出すべきときには燃焼室内における空燃比がリッチとされ、該予め定められた機関高負荷運転領域では燃焼室内における空燃比が理論空燃比にフィードバック制御され、該予め定められた機関中負荷運転領域では、該機関低負荷運転領域におけるベース空燃比よりも小さいベース空燃比のもとで燃焼室内における燃焼が行われると共に、該機関低負荷運転領域におけるNOx放出のための空燃比のリッチ周期よりも短い周期でもって燃焼室内における空燃比がリッチとされる請求項6に記載の火花点火式内燃機関の排気浄化装置。
- 排気浄化触媒の触媒担体上には、貴金属触媒が担持されており、更にこの触媒担体上にはカリウムK、ナトリウムNa、セシウムCsのようなアルカリ金属、バリウムBa、カルシウムCaのようなアルカリ土類金属、ランタノイドのような希土類および銀Ag、銅Cu、鉄Fe、イリジウムIrのようなNOxに電子を供与しうる金属から選ばれた少なくとも一つを含む塩基性層が形成されている請求項6に記載の火花点火式内燃機関の排気浄化装置。
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EP12883497.5A EP2891777B1 (en) | 2012-08-28 | 2012-08-28 | Exhaust purification device for spark ignition internal combustion engine |
US14/423,713 US9534552B2 (en) | 2012-08-28 | 2012-08-28 | Exhaust purification system of spark ignition type internal combustion engine |
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JP2018204533A (ja) * | 2017-06-02 | 2018-12-27 | トヨタ自動車株式会社 | 内燃機関の排気浄化装置 |
JP2021102944A (ja) * | 2019-12-25 | 2021-07-15 | トヨタ自動車株式会社 | 触媒劣化検出装置 |
JP2022007483A (ja) * | 2020-06-26 | 2022-01-13 | トヨタ自動車株式会社 | 排気浄化触媒の劣化診断装置 |
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CN104204434B (zh) * | 2013-02-20 | 2016-12-07 | 丰田自动车株式会社 | 内燃机的排气净化装置 |
JP6946871B2 (ja) * | 2017-09-05 | 2021-10-13 | トヨタ自動車株式会社 | 内燃機関の制御システム |
IT201900003269A1 (it) * | 2019-03-06 | 2020-09-06 | Fpt Motorenforschung Ag | Metodo e gruppo per controllare l'alimentazione di combustibile per un motore a combustione interna ad accensione comandata, in particolare per un motore alimentato a gas naturale |
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CN104704214A (zh) | 2015-06-10 |
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