WO2014122728A1 - 内燃機関の排気浄化装置 - Google Patents
内燃機関の排気浄化装置 Download PDFInfo
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- WO2014122728A1 WO2014122728A1 PCT/JP2013/052608 JP2013052608W WO2014122728A1 WO 2014122728 A1 WO2014122728 A1 WO 2014122728A1 JP 2013052608 W JP2013052608 W JP 2013052608W WO 2014122728 A1 WO2014122728 A1 WO 2014122728A1
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- exhaust
- exhaust gas
- purification catalyst
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- catalyst
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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
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
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- 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
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- 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
- B01D53/9495—Controlling the catalytic process
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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
- F01N3/0807—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
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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
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0871—Regulation of absorbents or adsorbents, e.g. purging
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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
- F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
- F01N3/2033—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating using a fuel burner or introducing fuel into exhaust duct
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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
- 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
- F02D41/1446—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 exhaust temperatures
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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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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2251/00—Reactants
- B01D2251/20—Reductants
- B01D2251/208—Hydrocarbons
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/40—Nitrogen compounds
- B01D2257/404—Nitrogen oxides other than dinitrogen oxide
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/01—Engine exhaust gases
- B01D2258/012—Diesel engines and lean burn gasoline engines
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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
- F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
- F01N2900/1602—Temperature of exhaust gas 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
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
- F01N2900/1614—NOx amount trapped in catalyst
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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
Definitions
- the present invention relates to an exhaust purification device for an internal combustion engine.
- An exhaust purification catalyst is disposed in the engine exhaust passage and a hydrocarbon supply valve is disposed in the engine exhaust passage upstream of the exhaust purification catalyst.
- the exhaust purification catalyst has a predetermined concentration of hydrocarbons flowing into the exhaust purification catalyst. When it is vibrated with an amplitude within a range and a period within a predetermined range, it has the property of reducing NO x contained in the exhaust gas, and when the vibration period of the hydrocarbon concentration is made longer than a predetermined range It has the property that the amount of occluded NO x contained in the exhaust gas increases, and NO x contained in the exhaust gas is reduced by injecting hydrocarbons with a predetermined injection cycle from the hydrocarbon supply valve.
- the second NO x purification method is selectively used, and the cycle in which the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst is made rich in the second NO x purification method is the above-described predetermined injection cycle Longer internal combustion engines are known (see, for example, Patent Document 1).
- An object of the present invention than when the NO x purification action by the first NO x purification method is being carried out, a high NO x than when the NO x purification action by the second NO x purification method is being carried out An object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that can obtain a purification rate.
- the exhaust purification catalyst is disposed in the engine exhaust passage
- the hydrocarbon supply valve is disposed in the engine exhaust passage upstream of the exhaust purification catalyst
- the noble metal catalyst is disposed on the exhaust gas flow surface of the exhaust purification catalyst.
- a basic exhaust gas flow surface portion is formed around the noble metal catalyst that is supported, and the exhaust purification catalyst has an amplitude within a predetermined range and a predetermined concentration of hydrocarbons flowing into the exhaust purification catalyst. When it is vibrated with a period within a predetermined range, it has the property of reducing NO x contained in the exhaust gas, and when the vibration period of the hydrocarbon concentration is longer than a predetermined range, it is contained in the exhaust gas.
- the second NO x purification method for releasing the stored NO x is selectively used, and the period during which the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst is made rich in the second NO x purification method is the above-mentioned beforehand.
- the temperature range that the exhaust purification catalyst can take during engine operation is divided into three regions, a low temperature region, a medium temperature region, and a high temperature region. is performed the NO x purification action by the NO x purification method, in a low temperature region is carried out the NO x purification action by the second NO x purification method, at moderate temperatures region, with at a predetermined injection period from the hydrocarbon feed valve The hydrocarbons are injected and the exhaust Internal combustion to NO x occluded in the catalyst air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst when exceeding the second tolerance value set in advance of a value smaller than the first allowable value is made rich An exhaust emission control device for an engine is provided.
- FIG. 1 is an overall view of a compression ignition type internal combustion engine.
- FIG. 2 is a view schematically showing the surface portion of the catalyst carrier.
- FIG. 3 is a view for explaining an oxidation reaction in the exhaust purification catalyst.
- FIG. 4 is a diagram showing changes in the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst.
- FIG. 5 is a diagram showing the NO x purification rate R1.
- 6A and 6B are diagrams for explaining the oxidation-reduction reaction in the exhaust purification catalyst.
- 7A and 7B are diagrams for explaining the oxidation-reduction reaction in the exhaust purification catalyst.
- FIG. 8 is a diagram showing a change in the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst.
- FIG. 9 is a diagram showing the NO x purification rate R2.
- FIG. 10 is a graph showing the relationship between the hydrocarbon injection cycle ⁇ T and the NO x purification rate R1.
- 11A and 11B are maps showing the injection amount of hydrocarbons and the like.
- 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 shows the fuel injection timing.
- FIG. 15 is a diagram showing a map of the additional fuel amount WR.
- FIG. 16 is a diagram showing the NO x purification rates R1 and R2.
- FIGS. 17A and 17B are views for explaining the storage amount of NO x in the exhaust purification catalyst.
- FIG. 18 is a diagram showing allowable values MAX and SX.
- FIG. 19 is a diagram showing a time chart of the NO x purification control in the intermediate temperature region.
- 20A and 20B are diagrams showing a map of the reduction rate RR of NO x and the like.
- FIG. 21 is a flowchart for performing NO x purification control.
- FIG. 22 is a flowchart for performing NO x purification control.
- FIG. 23 is a view for explaining the temperature distribution in the exhaust purification catalyst.
- FIG. 1 shows an overall view of a compression ignition type internal combustion engine.
- 1 is an engine body
- 2 is a combustion chamber of each cylinder
- 3 is an electronically controlled fuel injection valve for injecting fuel into each combustion chamber
- 4 is an intake manifold
- 5 is an exhaust manifold.
- the intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 via the intake duct 6, and the inlet of the compressor 7 a is connected to the air cleaner 9 via the intake air amount detector 8.
- a throttle valve 10 driven by an actuator is disposed in the intake duct 6, and a cooling device 11 for cooling intake air flowing through the intake duct 6 is disposed around the intake duct 6.
- the engine cooling water is guided into the cooling device 11, and the intake air is cooled by the engine cooling water.
- the exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7, and the outlet of the exhaust turbine 7 b is connected to the inlet of the exhaust purification catalyst 13 via the exhaust pipe 12.
- the exhaust purification catalyst 13 is composed of a NOx storage catalyst.
- the outlet of the exhaust purification catalyst 13 is connected to a particulate filter 14, and the exhaust pipe 12 upstream of the exhaust purification catalyst 13 is used to supply hydrocarbons consisting of light oil and other fuels used as fuel for a compression ignition internal combustion engine.
- a hydrocarbon feed valve 15 is arranged. In the embodiment shown in FIG. 1, light oil is used as the hydrocarbon supplied from the hydrocarbon supply valve 15.
- the present invention can also be applied to a spark ignition type internal combustion engine in which combustion is performed under a lean air-fuel ratio.
- hydrocarbons made of gasoline or other fuel used as fuel for the spark ignition type internal combustion engine are supplied from the hydrocarbon supply valve 15.
- the exhaust manifold 5 and the intake manifold 4 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 16, and an electronically controlled EGR control valve 17 is disposed in the EGR passage 16.
- EGR exhaust gas recirculation
- a cooling device 18 for cooling the EGR gas flowing in the EGR passage 16 is disposed.
- the engine cooling water is guided into the cooling device 18, and the EGR gas is cooled by the engine cooling water.
- Each fuel injection valve 3 is connected to a common rail 20 through a fuel supply pipe 19, and this common rail 20 is connected to a fuel tank 22 through an electronically controlled fuel pump 21 having a variable discharge amount.
- the fuel stored in the fuel tank 22 is supplied into the common rail 20 by the fuel pump 21, and the fuel supplied into the common rail 20 is supplied to the fuel injection valve 3 through each fuel supply pipe 19.
- the electronic control unit 30 comprises a digital computer and is connected to each other by a bidirectional bus 31.
- ROM read only memory
- RAM random access memory
- CPU microprocessor
- input port 35 and output port 36 It comprises.
- a temperature sensor 23 for detecting the temperature of the exhaust gas flowing out from the exhaust purification catalyst 13 is disposed downstream of the exhaust purification catalyst 13, and the output signals of the temperature sensor 23 and the intake air amount detector 8 correspond respectively. Is input to the input port 35 via the AD converter 37.
- a load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40. The output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37.
- crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 15 ° is connected to the input port 35.
- the output port 36 is connected to the fuel injection valve 3, the actuator for driving the throttle valve 10, the hydrocarbon supply valve 15, the EGR control valve 17, and the fuel pump 21 through corresponding drive circuits 38.
- FIG. 2 schematically shows a surface portion of the catalyst carrier carried on the substrate of the exhaust purification catalyst 13 shown in FIG.
- a noble metal catalyst 51 made of platinum Pt is supported on a catalyst support 50 made of alumina, and further, potassium K, sodium Na, Alkali metals such as cesium Cs, alkaline earth metals such as barium Ba and calcium Ca, rare earths such as lanthanides and metals that can donate electrons to NO x such as silver Ag, copper Cu, iron Fe, iridium Ir
- a basic layer 53 containing at least one selected from the above is formed.
- rhodium Rh or palladium Pd can be supported on the catalyst carrier 50 of the exhaust purification catalyst 13. Since the exhaust gas flows along the catalyst carrier 50, it can be said that the noble metal catalyst 51 is supported on the exhaust gas flow surface of the exhaust purification catalyst 13. Further, since the surface of the basic layer 53 is basic, the surface of the basic layer 53 is referred to as a basic exhaust gas flow surface portion 54.
- FIG. 3 schematically shows the reforming action performed in the exhaust purification catalyst 13 at this time.
- the hydrocarbon HC injected from the hydrocarbon feed valve 15 is converted into a radical hydrocarbon HC having a small number of carbons by the noble metal catalyst 51.
- FIG. 4 shows the supply timing of hydrocarbons from the hydrocarbon supply valve 15 and changes in the air-fuel ratio (A / F) in of the exhaust gas flowing into the exhaust purification catalyst 13. Since the change in the air-fuel ratio (A / F) in depends on the change in the concentration of hydrocarbons in the exhaust gas flowing into the exhaust purification catalyst 13, the air-fuel ratio (A / F) in shown in FIG. It can be said that the change represents a change in hydrocarbon concentration. However, since the air-fuel ratio (A / F) in decreases as the hydrocarbon concentration increases, the hydrocarbon concentration increases as the air-fuel ratio (A / F) in becomes richer in FIG.
- FIG. 5 shows the cycle of the air-fuel ratio (A / F) in of the exhaust gas flowing into the exhaust purification catalyst 13 as shown in FIG. 4 by periodically changing the concentration of hydrocarbons flowing into the exhaust purification catalyst 13.
- the NO x purification rate R1 by the exhaust purification catalyst 13 when the exhaust purification catalyst 13 is made rich is shown for each catalyst temperature TC of the exhaust purification catalyst 13.
- FIGS. 6A and 6B schematically show the surface portion of the catalyst carrier 50 of the exhaust purification catalyst 13, and in these FIGS. 6A and 6B, the concentration of hydrocarbons flowing into the exhaust purification catalyst 13 is predetermined. The reaction is shown to be presumed to occur when oscillated with an amplitude within a range and a period within a predetermined range.
- FIG. 6A shows a case where the concentration of hydrocarbons flowing into the exhaust purification catalyst 13 is low
- FIG. 6B shows the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 13 when hydrocarbons are supplied from the hydrocarbon supply valve 15.
- a / F When the in is made rich, that is, when the concentration of hydrocarbons flowing into the exhaust purification catalyst 13 is high.
- the oxygen concentration is high in the active NO x * around continues a predetermined time or more active NO x * is oxidized, nitrate ions NO 3 - in the basic layer 53 in the form of Absorbed.
- radical hydrocarbons HC activity NO x * is as hydrocarbon concentration is shown to be high in FIG. 6B on the platinum 51 around before the lapse of this period of time, whereby A reducing intermediate is produced. This reducing intermediate is attached or adsorbed on the surface of the basic layer 53.
- the first produced reducing intermediate this time is considered to be a nitro compound R-NO 2.
- this nitro compound R-NO 2 becomes a nitrile compound R-CN, but since this nitrile compound R-CN can only survive for a moment in that state, it immediately becomes an isocyanate compound R-NCO.
- This isocyanate compound R-NCO becomes an amine compound R-NH 2 when hydrolyzed.
- a reducing intermediate is generated by increasing the concentration of hydrocarbons flowing into the exhaust purification catalyst 13, and after reducing the concentration of hydrocarbons flowing into the exhaust purification catalyst 13,
- the reducing intermediate reacts with NO x , active NO x * and oxygen in the exhaust gas, or self-decomposes, thereby purifying NO x . That is, in order to purify NO x by the exhaust purification catalyst 13, it is necessary to periodically change the concentration of hydrocarbons flowing into the exhaust purification catalyst 13.
- the reducing intermediates R-NCO and R-NH 2 are used until they react with NO x , active NO x * and oxygen in the exhaust gas, or until they self-decompose. It must be retained on the basic layer 53, i.e. on the basic exhaust gas flow surface portion 54, for which a basic exhaust gas flow surface portion 54 is provided.
- the hydrocarbon supply cycle is lengthened, the period during which the oxygen concentration becomes high after the hydrocarbon is supplied and until the next hydrocarbon is supplied becomes longer, so that the active NO x * is reduced to the reducing intermediate. Without being generated in the basic layer 53 in the form of nitrate. In order to avoid this, it is necessary to vibrate the concentration of hydrocarbons flowing into the exhaust purification catalyst 13 with a period within a predetermined range.
- NO x contained in the exhaust gas is reacted with the reformed hydrocarbon to generate reducing intermediates R-NCO and R-NH 2 containing nitrogen and hydrocarbons.
- a noble metal catalyst 51 is supported on the exhaust gas flow surface of the exhaust purification catalyst 13, and the generated reducing intermediates R-NCO and R-NH 2 are held in the exhaust purification catalyst 13.
- a basic exhaust gas flow surface portion 54 is formed around the noble metal catalyst 51, and the reducing intermediates R-NCO and R-NH 2 held on the basic exhaust gas flow surface portion 54 are N 2.
- CO 2 , and H 2 O, and the vibration period of the hydrocarbon concentration is the vibration period necessary to continue to produce the reducing intermediates R-NCO and R-NH 2 .
- the injection interval is 3 seconds.
- FIG. 7B shows a case where the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 13 is made the stoichiometric air-fuel ratio or rich when NO x is absorbed in the basic layer 53 in the form of nitrate. Is shown.
- the reaction proceeds in the reverse direction (NO 3 ⁇ ⁇ NO 2 ), and thus the nitrates absorbed in the basic layer 53 are successively converted into nitrate ions NO 3.
- ⁇ And released from the basic layer 53 in the form of NO 2 as shown in FIG. 7B. The released NO 2 is then reduced by the hydrocarbons HC and CO contained in the exhaust gas.
- FIG. 8 shows a case where the air-fuel ratio (A / F) in of the exhaust gas flowing into the exhaust purification catalyst 13 is temporarily made rich slightly before the NO x absorption capacity of the basic layer 53 is saturated. Yes.
- the time interval of this rich control is 1 minute or more.
- the air-fuel ratio (A / F) in of the exhaust gas is lean
- the NO x absorbed in the basic layer 53 temporarily makes the air-fuel ratio (A / F) in of the exhaust gas rich.
- the basic layer 53 serves as an absorbent for temporarily absorbing NO x .
- the basic layer 53 temporarily adsorbs NO x, thus using term of storage as a term including both absorption and adsorption
- the basic layer 53 temporarily the NO x It plays the role of NO x storage agent for storage. That is, in this case, the ratio of air and fuel (hydrocarbon) supplied into the exhaust passage upstream of the engine intake passage, the combustion chamber 2 and the exhaust purification catalyst 13 is referred to as the exhaust gas air-fuel ratio. 13, the air-fuel ratio of the exhaust gas is acting as the NO x storage catalyst during the lean occludes NO x, the oxygen concentration in the exhaust gas to release NO x occluding the drops.
- FIG. 9 shows the NO x purification rate R2 when the exhaust purification catalyst 13 is made to function as a NO x storage catalyst in this way.
- the horizontal axis in FIG. 9 indicates the catalyst temperature TC of the exhaust purification catalyst 13.
- the exhaust purification catalyst 13 is made to function as a NO x storage catalyst in this way, an extremely high NO x purification rate can be obtained when the catalyst temperature TC is 250 ° C. to 300 ° C. as shown by the solid line in FIG.
- the temperature TC reaches a high temperature of 350 ° C. or higher, the NO x purification rate R2 decreases.
- the NO x purification rate R2 decreases because when the catalyst temperature TC exceeds 350 ° C., NO x is difficult to be occluded and the nitrate is thermally decomposed and NO 2 This is because it is discharged from the exhaust purification catalyst 13 in the form of. That is, as long as NO x is occluded in the form of nitrate, it is difficult to obtain a high NO x purification rate R2 when the catalyst temperature TC is high.
- the new NO x purification method shown in FIGS. 4 to 6B as can be seen from FIGS. 6A and 6B, nitrate is not generated or is very small even if it is generated, and as shown in FIG. Even when the catalyst temperature TC is high, a high NO x purification rate R1 can be obtained.
- a hydrocarbon supply valve 15 for supplying hydrocarbons is arranged in the engine exhaust passage so that NO x can be purified using this new NO x purification method, and hydrocarbon supply
- An exhaust purification catalyst 13 is arranged in the engine exhaust passage downstream of the valve 15, and a noble metal catalyst 51 is supported on the exhaust gas circulation surface of the exhaust purification catalyst 13 and a basic exhaust gas circulation around the noble metal catalyst 51 A surface portion 54 is formed, and the exhaust purification catalyst 13 causes the exhaust gas when the hydrocarbon concentration flowing into the exhaust purification catalyst 13 is vibrated with an amplitude within a predetermined range and a period within the predetermined range.
- NO x purification method when an exhaust purification catalyst that supports a noble metal catalyst and forms a basic layer capable of absorbing NO x is used, almost no nitrate is formed. NO x can be said to the a new the NO x purification method to be purified. In fact, when this new NO x purification method is used, the amount of nitrate detected from the basic layer 53 is very small compared to when the exhaust purification catalyst 13 functions as a NO x storage catalyst.
- This new NO x purification method is hereinafter referred to as a first NO x purification method.
- the hydrocarbon injection period ⁇ T from the hydrocarbon supply valve 15 becomes longer, after the hydrocarbon is injected, the oxygen concentration around the active NO x * is between the next injection of the hydrocarbon. The period during which becomes higher.
- the hydrocarbon injection period ⁇ T is longer than about 5 seconds, the active NO x * begins to be absorbed in the basic layer 53 in the form of nitrate, and therefore shown in FIG.
- the vibration period ⁇ T of the hydrocarbon concentration is longer than about 5 seconds, the NO x purification rate R1 decreases. Therefore, in the embodiment shown in FIG. 1, the hydrocarbon injection period ⁇ T needs to be 5 seconds or less.
- the injected hydrocarbon starts to accumulate on the exhaust gas flow surface of the exhaust purification catalyst 13 when the hydrocarbon injection period ⁇ T becomes approximately 0.3 seconds or less, and as shown in FIG.
- the hydrocarbon injection period ⁇ T becomes approximately 0.3 seconds or less, the NO x purification rate R1 decreases. Therefore, in the embodiment according to the present invention, the hydrocarbon injection period is set between 0.3 seconds and 5 seconds.
- the hydrocarbon injection amount and the injection timing from the hydrocarbon supply valve 15 are changed to the exhaust purification catalyst 13. Is controlled so that the air-fuel ratio (A / F) in and the injection cycle ⁇ T of the inflowing exhaust gas become optimum values according to the engine operating state.
- the optimum hydrocarbon injection amount WT when the NOx purification action by the first NOx purification method is performed is the injection amount Q from the fuel injection valve 3 and the engine speed N.
- 11A is stored in advance in the ROM 32 in the form of a map as shown in FIG. 11A, and the optimum hydrocarbon injection period ⁇ T at this time is also the injection amount Q from the fuel injection valve 3 and the engine speed N. Is previously stored in the ROM 32 in the form of a map as shown in FIG. 11B.
- the NO x purification method when the exhaust purification catalyst 13 is made to function as a NO x storage catalyst will be specifically described with reference to FIGS.
- the NO x purification method when the exhaust purification catalyst 13 functions as the NO x storage catalyst will be referred to as a second NO x purification method.
- the second NO x purification method as shown in FIG. 12, when the stored NO x amount ⁇ NOX stored in the basic layer 53 exceeds a predetermined first allowable amount MAX, The air-fuel ratio (A / F) in of the inflowing exhaust gas is temporarily made rich.
- Occluded amount of NO x ⁇ NOX is calculated from the amount of NO x exhausted from the engine, for example. Advance in the ROM32 in the form of a map as shown in FIG. 13 as a function of the injection quantity Q and engine speed N from the discharge amount of NO x NOXA the fuel injection valve 3 in the embodiment according to the present invention, which is discharged from the engine per unit time The stored NO x amount ⁇ NOX is calculated from this exhausted NO x amount NOXA. In this case, as described above, the period during which the air-fuel ratio (A / F) in of the exhaust gas is made rich is usually 1 minute or more.
- the air / fuel ratio (A / F) in of the gas is made rich.
- the horizontal axis in FIG. 14 indicates the crank angle.
- This additional fuel WR is injected when it burns but does not appear as engine output, that is, slightly before ATDC 90 ° after compression top dead center.
- This fuel amount WR is stored in advance in the ROM 32 in the form of a map as shown in FIG. 15 as a function of the injection amount Q from the fuel injection valve 3 and the engine speed N.
- Figure 16 is, the NO x purification rate when the NOx purification action is performed with the NO x purification rate R1 by the second NOx purification method when NOx purification action by the first NOx purification method has been done R2 And are shown together.
- NO x purification rate R1 when NOx purification action is being performed by the first NOx purification method the catalyst temperature TC becomes very high when the above 350 ° C.
- the catalyst temperature TC is At 350 ° C. or lower
- the catalyst temperature TC decreases as the temperature decreases.
- the NO x purification rate R2 when NOx purification action by the second NOx purification method is being carried out the catalyst temperature TC becomes very high when the 300 ° C.
- the catalyst temperature TC is 300 ° C. or higher Then, the catalyst temperature TC begins to decrease gradually as the catalyst temperature TC increases, and when the catalyst temperature TC reaches 350 ° C. or higher, it rapidly decreases as the catalyst temperature TC increases.
- T1 indicates the temperature of the catalyst when the the NO x purification rate R2 starts to decrease when the catalyst temperature TC rises when NOx purification action by the second NOx purification method is being carried out
- T2 indicates the catalyst temperature at which the NO x purification rate R2 becomes zero when the catalyst temperature TC rises further when the NOx purification action by the second NOx purification method has been done.
- a temperature region where the catalyst temperature TC is equal to or lower than the temperature T1 is referred to as a low temperature region
- a temperature region where the catalyst temperature TC is between the temperature T1 and the temperature T2 is referred to as a medium temperature region.
- a temperature region where TC is equal to or higher than temperature T2 is referred to as a high temperature region.
- the intermediate temperature region when the NO x purification action by the second NO x purification method is being carried out, is the NO x purification rate R2 when the temperature TC of the exhaust purification catalyst 13 rises decreases It shows the temperature range that keeps on.
- the NOx purification action by the first NOx purification method is performed at this time, that is, in the high temperature region.
- the NOx purification rate R2 becomes high. Therefore, in the embodiment according to the present invention, the NOx purification action by the second NOx purification method is performed at this time, that is, in the low temperature region.
- the NO x purification rate R1 decreases in a part of the temperature range, and the NO x purification rate R2 is a fairly wide temperature range. Decreases. Therefore, in this case, also by using the first and second one of the NOx purification method, NO x purification rate at somewhere in the temperature region is lowered.
- FIGS. 17A and 17B indicates when NO x is occluded in the exhaust purification catalyst 13, and hatching in FIGS. 17A and 17B indicates the total NO x amount that the exhaust purification catalyst 13 can occlude.
- the ratio of the NO x amount actually occluded, that is, the NO x occlusion ratio is shown.
- FIG. 17A shows the time when the NOx purification action by the second NOx purification method is being performed.
- the state indicated by X and the state indicated by Y are repeated. That is, at this time, as shown by Y in FIG. 17A, when the stored NO x amount in the exhaust purification catalyst 13 becomes close to saturation, that is, when it exceeds the first allowable value MAX shown in FIG.
- the air-fuel ratio of the inflowing exhaust gas is made rich, whereby the NO x storage ratio in the exhaust purification catalyst 13 is made zero, as indicated by X in FIG. 17A.
- the amount of NO x stored in the exhaust purification catalyst 13 increases.
- FIG. 17B shows a case where the first NOx purification method and the second NOx purification method are used in combination in the intermediate temperature range.
- the state indicated by X and the state indicated by Y are repeated. That is, at this time, as indicated by Y in FIG. 17B, the stored NO x amount in the exhaust purification catalyst 13 becomes the second allowable value SX smaller than the first allowable value MAX, that is, in the example shown in FIG. 17B. air-fuel ratio of the exhaust gas the NO x storage rate flows and the exhaust purification catalyst 13 becomes 50% is made rich, whereby as shown by X in FIG. 17B, and the NO x storage rate is zero at the exhaust purification catalyst 13 Is done.
- the second allowable value SX is the stored NO x amount when the NO x storage ratio is 50%.
- occluded amount of NO x in the exhaust purification catalyst 13 is first The air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 13 when the second allowable value SX is smaller than the allowable value MAX is made rich. That is, in the intermediate temperature region, performs a NOx purification action by the first NOx purification method, the exhaust gas flowing into the exhaust purification catalyst 13 when the occluded amount of NO x to the exhaust purification catalyst 13 reaches the second allowable value SX The air-fuel ratio is made rich.
- the exhaust purification catalyst 13 is disposed in the engine exhaust passage and the hydrocarbon supply valve 15 is disposed in the engine exhaust passage upstream of the exhaust purification catalyst 13, and the exhaust purification catalyst 13 has an exhaust gas flow surface on the surface thereof.
- a noble metal catalyst 51 is supported and a basic exhaust gas flow surface portion 54 is formed around the noble metal catalyst 51.
- the exhaust purification catalyst 13 predetermines the concentration of hydrocarbons flowing into the exhaust purification catalyst 13. When it is vibrated with an amplitude within a predetermined range and a period within a predetermined range, it has the property of reducing NO x contained in the exhaust gas, and the vibration period of the hydrocarbon concentration is more than the predetermined range.
- a second NO x purification method that releases the stored NO x from the exhaust purification catalyst 13 with a rich fuel ratio is selectively used, and the exhaust gas flowing into the exhaust purification catalyst 13 in the second NO x purification method is emptied.
- the period during which the fuel ratio is made rich is longer than the predetermined injection period described above.
- the temperature ranges that the exhaust purification catalyst 13 can take during engine operation are the low temperature range, the medium temperature range, and the high temperature range.
- the NO x purification action by the first NO x purification method is performed in a high temperature region, in a low temperature region is carried out the NO x purification action by the second NO x purification method, in intermediate temperature range, the carbonized Charcoal with a predetermined injection cycle from the hydrogen supply valve 15 Together with hydrogen is injected, it flows into the exhaust purification catalyst 13 when the occluded NO x in the exhaust purification catalyst 13 exceeds the second allowable value SX predetermined smaller value than the first allowable value MAX
- the air-fuel ratio of the exhaust gas to be made is made rich.
- FIG. 18 shows an embodiment in which the second allowable value SX is changed in accordance with the temperature TC of the exhaust purification catalyst 13.
- FIG. 18 also shows changes in the NO x purification rates R1, R2, and R.
- the catalyst temperature TC increases in the intermediate temperature range, the amount of NO x that can be stored in the exhaust purification catalyst 13 decreases.
- NO x cannot be stored unless NO x is released from the exhaust purification catalyst 13 while the amount of NO x stored in the exhaust purification catalyst 13 is small.
- the second allowable value SX is made smaller as the temperature TC of the exhaust purification catalyst 13 becomes higher.
- FIG. 19 shows a time chart of the NO x purification control in the intermediate temperature region.
- the hydrocarbon supply signal from the hydrocarbon supply valve 15, the supply signal of the additional fuel WR from the fuel injection valve 3, the change in the stored NO x amount ⁇ NOX in the exhaust purification catalyst 13, the exhaust The change of the air-fuel ratio (A / F) in of the exhaust gas flowing into the purification catalyst 13 is shown.
- FIG. 18 also shows the first allowable value MAX and the second allowable value SX. From FIG. 18, it can be seen that the second tolerance value SX is considerably smaller than the first tolerance value MAX.
- NOX (NOXA-RR) ⁇ KR
- NOXA shows the discharge amount of NO x per unit time from the engine shown in FIG. 13
- RR is shows a NOx reduction amount per unit by hydrocarbons which are injected from the hydrocarbon feed valve 15 time
- KR represents the storage rate of NO x in the exhaust purification catalyst 13.
- the injection amount WT and the injection cycle ⁇ T of hydrocarbons from the hydrocarbon supply valve 15 are determined in advance according to the operating state of the engine, and are therefore injected from the hydrocarbon supply valve 15.
- the reduction amount RR of NO x that is reduced per unit time of injection by the hydrocarbon is also determined in advance according to the operating state of the engine. Therefore, in the embodiment according to the present invention, this NO x reduction amount RR per unit time is previously stored in the ROM 32 in the form of a map as shown in FIG. 20A as a function of the injection amount Q from the fuel injection valve 3 and the engine speed N. Is stored within.
- storage modulus KR of the NO x is the hydrocarbon feed valve 15 the amount of NO x which could not have been reduced by hydrocarbon injection from the amount of NO x occluded in the exhaust purification catalyst 13 within the (NOXA-RR) indicates the percentage adsorption rate KP of the NO x, as shown in FIG. 20B, decreases as the temperature TC of the exhaust purification catalyst 13 becomes higher.
- Amount of NO x ⁇ NOX occluded in the exhaust purification catalyst 13 is calculated by the amount of NO x NOX is occluded in the exhaust purification catalyst 13 per unit time is calculated integrating the amount of NO x NOX.
- the NO x purification action by the first NO x purification method is performed in the middle temperature range, the NO x amount NOXA exhausted from the engine and the operating state of the engine and reducing the amount RR of the NO x determined, the calculated amount of NO x ⁇ NOX occluded in the exhaust purification catalyst 13 from absorbing rate KP of the NO x determined from the temperature TC of the exhaust purification catalyst 13, the amount of NO x ⁇ NOX calculated
- the second allowable value SX is exceeded, the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 13 is made rich.
- FIGS. 21 and 22 show a NO x purification control routine for executing the NO x purification method shown in FIG. 19, and this routine is executed by interruption every predetermined time.
- the temperature TC of the exhaust purification catalyst 13 is calculated based on the detected value of the temperature sensor 23.
- the routine proceeds to step 62, where the second NO x purification method is performed. the NO x purification action by is performed.
- the discharge amount of NO x NOXA per unit time is calculated from the map shown in FIG. 13, step 62.
- occluded amount of NO x ⁇ NOX is calculated by adding the discharge amount of NO x NOXA to ⁇ NOX step 63.
- occluded amount of NO x ⁇ NOX step 64 whether exceeds the first tolerance value MAX is determined.
- the routine proceeds to step 65, where an additional fuel amount WR is calculated from the map shown in FIG. 15, and then at step 66, an additional fuel injection action is performed.
- the air-fuel ratio (A / F) in of the exhaust gas flowing into the exhaust purification catalyst 13 is made rich.
- step 67 it is judged if regeneration of the exhaust purification catalyst 13 has been completed. If it is judged that regeneration of the exhaust purification catalyst 13 has been completed, the routine proceeds to step 68 where ⁇ NOX is cleared.
- step 61 when it is determined at step 61 that the exhaust gas temperature TC is higher than the temperature T1, the routine proceeds to step 69 where it is determined whether or not the catalyst temperature TC is higher than the temperature T2.
- the catalyst temperature T is higher than the medium temperature T2, that is, when the temperature is in the high temperature range, it is determined that the NOx purification action by the first NOx purification method should be performed, and the routine proceeds to step 70 and the NOx purification by the first NOx purification method The action is performed. That is, in step 70, the hydrocarbon injection period ⁇ T is read from FIG. 11B.
- step 71 it is determined whether or not the injection timing has come. When the injection time has come, the routine proceeds to step 72 where the hydrocarbon injection amount WT is calculated from FIG. 11A.
- step 73 hydrocarbons are injected from the hydrocarbon supply valve 15 with the injection amount WT calculated at step 72.
- step 78 the second allowable value SX shown in FIG. 18 is calculated.
- step 79 it is judged if the occluded NO x amount ⁇ NOX has exceeded a second allowable value SX.
- NOx purification action by the first NOx purification method proceeds to step 80 is performed when the storage amount of NO x ⁇ NOX does not exceed the second tolerance value SX. That is, in step 80, the hydrocarbon injection period ⁇ T is read from FIG. 11B.
- step 81 it is determined whether or not the injection timing has come. When the injection time has come, the routine proceeds to step 82 where the hydrocarbon injection amount WT is calculated from FIG. 11A.
- step 83 hydrocarbons are injected from the hydrocarbon supply valve 15 with the injection amount WT calculated at step 82.
- step 84 the NO x amount CNO released from the exhaust purification catalyst 13 at the time of hydrocarbon injection from the hydrocarbon supply valve 15 is subtracted from the stored NO x amount ⁇ NOX.
- step 85 storage amount of NO x ⁇ NOX is injection prohibition flag is set the routine proceeds to step 85 when it is determined to exceed the second permissible value SX in step 79, then the routine proceeds to step 86.
- the routine jumps from step 74 to step 86 in the next processing cycle.
- step 86 the additional fuel amount WRL required to release the stored NO x is calculated, and then in step 87, the additional fuel is injected into the combustion chamber 2.
- the air-fuel ratio (A / F) in of the exhaust gas flowing into the exhaust purification catalyst 13 is made rich.
- step 88 it is judged if regeneration of the exhaust purification catalyst 13 has been completed. If it is judged that regeneration of the exhaust purification catalyst 13 has been completed, the routine proceeds to step 89, where the injection inhibition flag is reset.
- ⁇ NOX is cleared.
- the catalyst temperature TC when the catalyst temperature TC is maintained in the middle temperature range, there is no large temperature difference between the upstream side and the downstream side of the exhaust purification catalyst 13.
- the temperature TC of the exhaust purification catalyst 13 increases, and the catalyst temperature TC changes from the middle temperature range to the high temperature range. Become.
- the catalyst temperature TC is lowered, and the catalyst temperature TC again becomes an intermediate temperature region.
- the exhaust purification catalyst 13 is cooled from the upstream side. Therefore, at this time, as shown in FIG.
- the downstream side is higher than the upstream side. That is, when the regeneration of the particulate filter is completed, a large temperature difference occurs between the upstream side and the downstream side of the exhaust purification catalyst 13.
- the catalyst temperature TC calculated from the detected value of the temperature sensor 23 is an average temperature as indicated by Tm in FIG.
- the NO x amount NOX stored per unit time is calculated based on the following equation.
- NOX (NOXA-RR) ⁇ KR
- the reduction amount RR of NO x in this case is an amount at an average temperature in the intermediate temperature range.
- the reduction amount RR of NO x increases as the catalyst temperature TC increases. Therefore, as shown in FIG. 23, the reduction amount RR of NO x increases when a portion having a high temperature TC exists in the exhaust purification catalyst 13. It will be.
- the NO x amount NOX stored per unit time is calculated based on the following equation, and an operating state in which a portion having a high temperature TC exists in the exhaust purification catalyst 13 as shown in FIG.
- NOX (NOXA-RR ⁇ ZK) ⁇ KR
- an oxidation catalyst for reforming hydrocarbons can be disposed in the engine exhaust passage upstream of the exhaust purification catalyst 13.
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Abstract
Description
本発明の目的は、第1のNOx浄化方法によるNOx浄化作用が行われているときよりも、第2のNOx浄化方法によるNOx浄化作用が行われているときよりも高いNOx浄化率が得られるようにした内燃機関の排気浄化装置を提供することにある。
図1を参照すると、1は機関本体、2は各気筒の燃焼室、3は各燃焼室2内に夫々燃料を噴射するための電子制御式燃料噴射弁、4は吸気マニホルド、5は排気マニホルドを夫々示す。吸気マニホルド4は吸気ダクト6を介して排気ターボチャージャ7のコンプレッサ7aの出口に連結され、コンプレッサ7aの入口は吸入空気量検出器8を介してエアクリーナ9に連結される。吸気ダクト6内にはアクチュエータにより駆動されるスロットル弁10が配置され、吸気ダクト6周りには吸気ダクト6内を流れる吸入空気を冷却するための冷却装置11が配置される。図1に示される実施例では機関冷却水が冷却装置11内に導かれ、機関冷却水によって吸入空気が冷却される。
この第2のNOx浄化方法では図12に示されるように塩基性層53に吸蔵された吸蔵NOx量ΣNOXが予め定められた第1の許容量MAXを越えたときに排気浄化触媒13に流入する排気ガスの空燃比(A/F)inが一時的にリッチにされる。排気ガスの空燃比(A/F)inがリッチにされると、排気ガスの空燃比(A/F)inがリーンのときに塩基性層53内に吸蔵されたNOxが塩基性層53から一気に放出されて還元される。それによってNOxが浄化される。
図16に示されるように、第1のNOx浄化方法によるNOx浄化作用が行われているときのNOx浄化率R1は、触媒温度TCが350℃以上のときに極めて高くなり、触媒温度TCが350℃以下になると触媒温度TCが低くなるにつれて低下する。一方、第2のNOx浄化方法によるNOx浄化作用が行われているときのNOx浄化率R2は、触媒温度TCが250℃から300℃のときに極めて高くなり、触媒温度TCが300℃以上になると触媒温度TCが高くなるにつれて少しずつ低下し始めると共に触媒温度TCが350℃以上になると触媒温度TCの上昇に伴い急激に低下する。
1の許容値MAXに比べてかなり小さいことがわかる。
NOX=(NOXA-RR)・KR
ここで、NOXAは図13に示される機関からの単位時間当たりの排出NOx量を示しており、RRは炭化水素供給弁15から噴射された炭化水素による単位時間当たりのNOx還元量を示しており、KRは排気浄化触媒13 へのNOxの吸蔵率を示している。図11Aおよび11Bに示されるように、炭化水素供給弁15からの炭化水素の噴射量WTおよび噴射周期ΔTは機関の運転状態に応じて予め定まっており、従って炭化水素供給弁15から噴射された炭化水素によって噴射単位時間当たりに還元されるNOxの還元量RRも機関の運転状態に応じて予め定まることになる。従って、本発明による実施例では、この単位時間当たりのNOx還元量RRは、燃料噴射弁3からの噴射量Qおよび機関回転数Nの関数として図20Aに示すようなマップの形で予めROM32内に記憶されている。一方、NOxの吸蔵率KRは、炭化水素供給弁15から噴射された炭化水素によって還元し得なかったNOx量(NOXA-RR)のうちで排気浄化触媒13に吸蔵されるNOx量の割合を示しており、このNOxの吸蔵率KPは図20Bに示されるように、排気浄化触媒13の温度TCが高くなると低下する。
図21を参照するとまず初めにステップ60において、温度センサ23の検出値に基づいて
排気浄化触媒13の温度TCが算出される。次いで、ステップ61では、触媒温度TCが温度T1よりも低いか否かが判別される。触媒温度TCが温度T1よりも低いとき、即ち低温領域であるときには第2のNOx浄化方法によるNOx浄化作用を行うべきであると判別され、ステップ62に進んで第2のNOx浄化方法によるNOx浄化作用が行われる。
NOX=(NOXA-RR)・KR
次いでステップ77では排気浄化触媒13に吸蔵されているNOx量ΣNOXが次式に基づいて算出される。
ΣNOX=ΣNOX+NOX
NOX=(NOXA-RR)・KR
この場合のNOxの還元量RRは中温領域における平均的な温度における量とされている。ところがこのNOxの還元量RRは触媒温度TCが高くなると増大し、従って図23に示されるように排気浄化触媒13内において温度TCが高い部分が存在するときにはNOxの還元量RRが増大することになる。そこでこの実施例では、単位時間当たり吸蔵されるNOx量NOXを次式に基づいて算出し、図23に示されるように排気浄化触媒13内において温度TCが高い部分が存在するような運転状態のときには、通常は1.0とされている増量係数ZKの値を大きくするようにしている。
NOX=(NOXA-RR・ZK)・KR
このようにこの実施例では、排気浄化触媒13において温度差が生じており、検出された排気浄化触媒13の温度TCよりも高い温度領域が排気浄化触媒13内に存在する場合には、NOxの還元量RRが増大される。
5 排気マニホルド
7 排気ターボチャージャ
12 排気管
13 排気浄化触媒
14 パティキュレートフィルタ
15 炭化水素供給弁
Claims (7)
- 機関排気通路内に排気浄化触媒を配置すると共に排気浄化触媒上流の機関排気通路内に炭化水素供給弁を配置し、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炭化水素の濃度を予め定められた範囲内の振幅および予め定められた範囲内の周期でもって振動させ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、該炭化水素濃度の振動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の吸蔵量が増大する性質を有しており、炭化水素供給弁から予め定められた噴射周期でもって炭化水素を噴射することにより排気ガス中に含まれるNOxを浄化する第1のNOx浄化方法と、排気浄化触媒に吸蔵されたNOxが予め定められた第1の許容値を超えたときに排気浄化触媒に流入する排気ガスの空燃比をリッチにして排気浄化触媒から吸蔵NOxを放出させる第2のNOx浄化方法とが選択的に用いられ、該第2のNOx浄化方法において排気浄化触媒に流入する排気ガスの空燃比がリッチにされる周期は該予め定められた噴射周期よりも長い内燃機関の排気浄化装置において、機関運転時に該排気浄化触媒がとり得る温度領域を低温領域と中温領域と高温領域との三つの領域に分別し、該高温領域では該第1のNOx浄化方法によるNOx浄化作用が行われ、該低温領域では該第2のNOx浄化方法によるNOx浄化作用が行われ、該中温領域では、炭化水素供給弁から該予め定められた噴射周期でもって炭化水素が噴射されると共に、排気浄化触媒に吸蔵されたNOxが該第1の許容値よりも小さな値の予め定められた第2の許容値を超えたときに排気浄化触媒に流入する排気ガスの空燃比がリッチにされる内燃機関の排気浄化装置。
- 該第2のNOx浄化方法が行われている場合において、排気浄化触媒に流入する排気ガスの空燃比をリッチにすべきときには、燃焼室内に追加の燃料を供給することによって燃焼室から排出される排気ガスの空燃比がリッチにされる請求項1に記載の内燃機関の排気浄化装置。
- 該中温領域は、該第2のNOx浄化方法によるNOx浄化作用が行われている場合において、該排気浄化触媒の温度が上昇したときにNOx浄化率が低下し続ける温度範囲である請求項1に記載の内燃機関の排気浄化装置。
- 上記第2の許容値は、排気浄化触媒の温度が高くなるにつれて小さくされる請求項1に記載の内燃機関の排気浄化装置。
- 該中温領域において、排気浄化触媒に流入する排気ガスの空燃比がリッチにされている間は、炭化水素供給弁からの炭化水素の噴射が中断される請求項1に記載の内燃機関の排気浄化装置。
- 上記中温領域において、該第1のNOx浄化方法によるNOx浄化作用が行われているときに、機関から排出されるNOx量と、機関の運転状態から定まるNOxの還元量と、排気浄化触媒の温度から定まるNOxの吸蔵率から排気浄化触媒に吸蔵されるNOx量が算出され、算出された該NOx量が上記第2の許容値を超えたときに排気浄化触媒に流入する排気ガスの空燃比がリッチにされる請求項1に記載の内燃機関の排気浄化装置。
- 排気浄化触媒内において温度差が生じており、検出された排気浄化触媒の温度よりも高い温度領域が排気浄化触媒内に存在する場合には、上記NOxの還元量が増大される請求項6に記載の内燃機関の排気浄化装置。
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EP13780046.2A EP2955348B1 (en) | 2013-02-05 | 2013-02-05 | Exhaust purification system of internal combustion engine |
JP2013552028A JP5673861B2 (ja) | 2013-02-05 | 2013-02-05 | 内燃機関の排気浄化装置 |
US14/114,587 US9441515B2 (en) | 2013-02-05 | 2013-02-05 | Exhaust purification system of internal combustion engine |
CN201380001503.4A CN104105852B (zh) | 2013-02-05 | 2013-02-05 | 内燃机的排气净化装置 |
PCT/JP2013/052608 WO2014122728A1 (ja) | 2013-02-05 | 2013-02-05 | 内燃機関の排気浄化装置 |
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EP (1) | EP2955348B1 (ja) |
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EP3273023A4 (en) * | 2015-03-18 | 2018-10-10 | Isuzu Motors, Ltd. | Exhaust purification system |
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JP5672328B2 (ja) * | 2013-03-22 | 2015-02-18 | トヨタ自動車株式会社 | 内燃機関の排気浄化装置 |
JP6477088B2 (ja) * | 2015-03-20 | 2019-03-06 | いすゞ自動車株式会社 | NOx吸蔵量推定装置 |
KR102371252B1 (ko) * | 2017-10-25 | 2022-03-04 | 현대자동차 주식회사 | 냉시동 시 차량 제어 시스템 및 방법 |
CN113803136B (zh) * | 2020-06-12 | 2023-02-03 | 丰田自动车株式会社 | 内燃机的排气净化装置及催化剂 |
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CN104105852A (zh) | 2014-10-15 |
JPWO2014122728A1 (ja) | 2017-01-26 |
US20150322834A1 (en) | 2015-11-12 |
EP2955348A4 (en) | 2016-01-20 |
US9441515B2 (en) | 2016-09-13 |
EP2955348B1 (en) | 2017-07-05 |
EP2955348A1 (en) | 2015-12-16 |
JP5673861B2 (ja) | 2015-02-18 |
CN104105852B (zh) | 2016-03-09 |
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