WO2014024311A1 - Dispositif de purification de gaz d'échappement pour moteur à combustion interne et à allumage par étincelle - Google Patents

Dispositif de purification de gaz d'échappement pour moteur à combustion interne et à allumage par étincelle Download PDF

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Publication number
WO2014024311A1
WO2014024311A1 PCT/JP2012/070522 JP2012070522W WO2014024311A1 WO 2014024311 A1 WO2014024311 A1 WO 2014024311A1 JP 2012070522 W JP2012070522 W JP 2012070522W WO 2014024311 A1 WO2014024311 A1 WO 2014024311A1
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Prior art keywords
engine
fuel ratio
air
catalyst
exhaust gas
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PCT/JP2012/070522
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English (en)
Japanese (ja)
Inventor
悠樹 美才治
吉田　耕平
櫻井　健治
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トヨタ自動車株式会社
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Priority to PCT/JP2012/070522 priority Critical patent/WO2014024311A1/fr
Publication of WO2014024311A1 publication Critical patent/WO2014024311A1/fr

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • 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
    • F01N3/0864—Oxygen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/0295—Control according to the amount of oxygen that is stored on the exhaust gas treating apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0814—Oxygen storage amount
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0816—Oxygen storage capacity
    • 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
    • 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 emission control device for a spark ignition type internal combustion engine.
  • An exhaust purification catalyst is arranged in the engine exhaust passage and a hydrocarbon supply valve is arranged in the engine exhaust passage upstream of the exhaust purification catalyst.
  • a noble metal catalyst is supported on the exhaust gas flow surface of the exhaust purification catalyst and noble metal
  • a basic exhaust gas flow surface portion is formed around the catalyst, and when hydrocarbons are injected from the hydrocarbon supply valve at a predetermined cycle during engine operation, nitrogen compounds and hydrocarbons are formed on the exhaust purification catalyst.
  • a compression ignition type internal combustion engine in which an intermediate body which is a combined body is generated and NO x contained in exhaust gas is purified using this intermediate body is known (see, for example, Patent Document 1). In this internal combustion engine, a high NO x purification rate can be obtained even when the temperature of the exhaust purification catalyst becomes high.
  • the monoxide generated in the combustion chamber when switching to rich is made.
  • the carbon CO generates an intermediate that is a combined body of nitrogen and carbon monoxide CO on the exhaust purification catalyst, and NO x contained in the exhaust gas is purified using this intermediate.
  • the intermediate is a conjugate of nitrogen monoxide carbide CO is easily oxidized, so that these intermediates can not be sufficiently used for the purification of NO x, to purify enough NO x There is a problem that you can not.
  • An object of the present invention is to provide an exhaust emission control device for a spark ignition internal combustion engine that makes it possible to sufficiently use the produced intermediate for NO x purification, thereby obtaining a high NO x purification rate. There is.
  • the exhaust purification catalyst is disposed in the engine exhaust passage, the catalyst having an oxygen storage function is disposed in the engine exhaust passage upstream of the exhaust purification catalyst, and the noble metal is disposed on the exhaust gas distribution surface of the exhaust purification catalyst.
  • the catalyst is supported and a basic exhaust gas flow surface portion is formed around the noble metal catalyst.
  • the exhaust purification catalyst has an air-fuel ratio of exhaust gas flowing into the exhaust purification catalyst within a predetermined range.
  • a high NO x purification rate can be secured even in a spark ignition type internal combustion engine.
  • 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 and 4B are views for explaining an adsorption reaction and the like in the exhaust purification catalyst.
  • FIG. 5 is a view showing another embodiment of the exhaust purification catalyst.
  • 6A and 6B are diagrams for explaining the oxidation-reduction reaction in the exhaust purification catalyst.
  • FIG. 7 is a diagram showing NO x release control.
  • FIG. 8 is a diagram showing a map of the exhausted NO x amount NOXA.
  • FIG. 9 is a diagram showing the NO x purification rate.
  • 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
  • FIG. 10 is a diagram showing changes in the air-fuel ratio of the exhaust gas flowing into the three-way catalyst and the exhaust purification catalyst.
  • FIG. 11 is a graph showing the relationship between the lean-to-rich switching period ⁇ T of the air-fuel ratio and the NO x purification rate.
  • FIG. 12 is a diagram showing the NO x purification rate.
  • FIG. 13 is a diagram showing a map of the fuel injection amount.
  • FIG. 14 is a diagram showing a map of the switching cycle ⁇ T from the lean to rich air-fuel ratio.
  • 15A and 15B are diagrams for explaining the NO x absorption ability and NO adsorption ability.
  • 16A and 16B are diagrams for explaining the NO x absorption ability and NO adsorption ability.
  • FIG. 17A, 17B and 17C are time charts showing changes in the air-fuel ratio of the exhaust gas discharged from the engine.
  • FIG. 18 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. 19 is a diagram showing an operation region of the engine.
  • FIG. 20 is a time chart showing changes in the fuel injection amount during engine operation.
  • FIG. 21 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 the combustion chamber 2 and an electronically controlled fuel injection valve 11 for injecting fuel, i.e., gasoline, into the intake port 8.
  • 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 catalyst 20 having an oxygen storage function through an exhaust manifold 19, and an outlet of the catalyst 20 is connected to an inlet of an exhaust purification catalyst 22 through an exhaust pipe 21.
  • the catalyst 20 having the oxygen storage function is a three-way catalyst.
  • 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.
  • EGR exhaust gas recirculation
  • 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.
  • the three-way catalyst 20 is contained 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 a function of simultaneously reducing harmful components HC, CO and NO x contained therein. 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. 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 present inventors have repeatedly studied the NO x purification action when combustion is performed under a lean air-fuel ratio in a spark ignition internal combustion engine, and as a result, the NO x purification action in the spark ignition internal combustion engine. With regard to the above, it has been found that the NO adsorption action on the exhaust purification catalyst 13 has a great influence.
  • 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, this NO x purification method using adsorbed NO will be described with reference to FIGS. 4A and 4B.
  • FIG. 4A and 4B show an enlarged view of FIG. 3B, that is, a surface portion of the catalyst carrier 60 of the exhaust purification catalyst 22.
  • FIG. 4A shows the time when combustion is performed under a lean air-fuel ratio
  • FIG. 4B shows the time when the air-fuel ratio in the combustion chamber 5 is made rich.
  • NO contained in the exhaust gas is purified by exhaust gas.
  • NO x contained in the exhaust gas is adsorbed by the catalyst 22 and reacted with the reducing intermediate NCO held or adsorbed on the surface of the basic layer 63 to be purified.
  • NO x adsorbed on the exhaust purification catalyst 22 is released from the exhaust purification catalyst 22 and reduced. Therefore, NO x contained in the exhaust gas can be purified by periodically enriching the air-fuel ratio in the combustion chamber 5 when combustion is performed under a lean air-fuel ratio.
  • a catalyst 20 having an oxygen storage function is disposed upstream of the exhaust purification catalyst 22 in order to prevent a large amount of oxygen from being sent to the exhaust purification catalyst 22 when combustion with a lean air-fuel ratio is started.
  • the catalyst 20 having an oxygen storage function is arranged upstream of the exhaust purification catalyst 22, a large amount of oxygen is stored in the catalyst 20 when combustion by the lean air-fuel ratio is started, and as a result, exhaust purification.
  • the amount of oxygen flowing into the catalyst 22 decreases. Therefore, most of the generated reducing intermediate NCO continues to be held or adsorbed on the surface of the basic layer 63, and as a result, the NO x contained in the exhaust gas is well purified.
  • the catalyst 20 having an oxygen storage function is composed of a three-way catalyst disposed upstream of the exhaust purification catalyst 22.
  • the upstream side portion 22a of the exhaust purification catalyst 22 can have an oxygen storage function. That is, a catalyst having an oxygen storage function can be integrally formed on the upstream side of the exhaust purification catalyst 22.
  • the downstream portion 22b of the NO x storage catalyst 22 may have a weaker oxygen storage function than the upstream portion 22a.
  • NO contained in the exhaust gas is platinum Pt as shown in FIG. 4A. Dissociates and adsorbs on the surface of 61. However, after a while from the start of the lean air-fuel ratio combustion, the NO x contained in the exhaust gas is absorbed by the exhaust purification catalyst 22.
  • the absorption and release action of the NO x in the exhaust purification catalyst 22, enlarged in Figure 3B This will be described with reference to FIGS. 6A and 6B.
  • the air-fuel ratio in the combustion chamber 5 is made rich, the oxygen concentration in the exhaust gas flowing into the exhaust purification catalyst 22 decreases, so that the reaction proceeds in the reverse direction (NO 3 ⁇ ⁇ NO 2 ).
  • the nitrate absorbed in the basic layer 63 is successively released as nitrate ions NO 3 ⁇ from the basic layer 63 in the form of NO 2 as shown in FIG. 6B.
  • 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.
  • FIG. 7 shows the NO x release control when NO x is absorbed by 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. 8 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 9 shows the NO x purification rate when so as to purify NO x by absorbing and releasing action of the NO x in such an exhaust purification catalyst 22 as shown in FIG.
  • the horizontal axis in FIG. 9 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.
  • FIG. 10 shows the change in the air-fuel ratio (A / F) of the exhaust gas flowing into the exhaust purification catalyst 22 when the NO x purification action is performed by this NO x purification method using adsorbed NO.
  • (A / F) b indicates the base air-fuel ratio in the engine combustion chamber 5.
  • FIG. 12 shows the NO x purification rate when NO x is purified by the NO x purification method using adsorption NO. As shown in FIG. 12, 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 richness of the air-fuel ratio in the combustion chamber 5 and the lean-to-rich switching cycle ⁇ T are changed by changing the fuel injection amount and the injection timing from the fuel injection valves 11 and 12. It is controlled so as to have an optimum value according to the operating state.
  • the fuel injection amount WT capable of obtaining this optimum rich air-fuel ratio is previously stored in the ROM 32 in the form of a map as shown in FIG. 13 as a function of the required load L and the engine speed N. It is remembered. Further, the optimum lean-to-rich switching period ⁇ T is also stored in advance in the ROM 32 as a function of the required load L and the engine speed N in the form of a map as shown in FIG.
  • the exhaust purification catalyst 22 is disposed in the engine exhaust passage, and the catalyst 20 having an oxygen storage function is disposed in the engine exhaust passage upstream of the exhaust purification catalyst 22.
  • Precious metal catalysts 61 and 62 are supported on the exhaust gas flow surface, and a basic exhaust gas flow surface portion is formed around the noble metal catalysts 61 and 62.
  • the exhaust purification catalyst 22 is an exhaust purification catalyst 22.
  • the air-fuel ratio of the exhaust gas flowing into the exhaust gas is temporarily switched from lean to rich with a period within a predetermined range, it has the property of reducing NO x contained in the exhaust gas and switching from lean to rich cycle has the property of absorption is increased in the predetermined NO contained in the exhaust gas to be longer than the range x, this air-fuel ratio in the combustion chamber 5 at the time of engine operation Rich temporarily switched from lean with a cycle of the predetermined range, thereby so as to purify the NO x contained in the exhaust gas.
  • FIG. 15A 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. 15A 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, the NO adsorption capacity of the exhaust purification catalyst 22 decreases as the oxygen concentration in the exhaust gas increases, as shown in FIG. 16A.
  • the higher the oxygen concentration in the exhaust gas the more NO oxidation in the exhaust gas is promoted and the NO x absorption into the exhaust purification catalyst 22 is promoted. Therefore, as shown in FIG. 16B, the NO x absorption capacity in the exhaust purification catalyst 22 increases as the oxygen concentration in the exhaust gas increases.
  • the region X is obtained under the lean air-fuel ratio when NO x is purified by using the NO x storage / release action to the 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. 15A 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. 15B 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. 16A and 16B.
  • FIG. 17A shows the air-fuel ratio (A / F) in the combustion chamber 5 when NO x is purified 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. 17B shows the change in the air-fuel ratio (A / F) in the combustion chamber 5 when NO x is purified using 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. 17C 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. 18 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. 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.
  • shaft L of FIG. 19 has shown the required load
  • the horizontal axis N has shown the engine speed.
  • the NO x purification action that purifies NO x by using the NO x storage and release action to the exhaust purification catalyst 22 is performed.
  • 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. 20 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 represents the first allowable NO x storage amount
  • MAX II represents the second allowable NO x storage amount.
  • the second allowable NO x storage amount MAXII is set to a smaller value than the first allowable NO x storage amount MAXI.
  • the first allowable NO x storage amount MAXI is the same as the allowable NO x storage amount MAXI in FIG.
  • the air-fuel ratio in the combustion chamber 5 is temporarily made rich.
  • the exhaust purification catalyst 22 is high, NO x is hardly absorbed into the exhaust purification catalyst 22, the majority of the NO x consists of adsorbing NO. Therefore, in other words, the NO adsorption amount adsorbed by the exhaust purification catalyst 22 is calculated, and when the engine is operating in the engine middle load operation region II, the NO adsorption amount ⁇ NOX is preliminarily determined.
  • the determined allowable NO adsorption amount MAXII is exceeded, the air-fuel ratio (A / F) in the combustion chamber 5 is made rich.
  • the engine low load operating region I which is occluded in the exhaust purifying catalyst 22, NO x
  • the occlusion amount ⁇ NOX exceeds a predetermined first allowable NO x occlusion amount MAXI
  • the air-fuel ratio (A / F) in the combustion chamber 5 is made rich, and the engine is operated in the engine middle load operation region II.
  • the air-fuel ratio (a / F) is made rich in the combustion chamber 5 when exceeding the second tolerance the NO x storage amount MAXII that the NO x storage amount ⁇ NOX is predetermined, the second The allowable NO x occlusion amount MAXII is smaller than the first allowable NO x occlusion amount MAXI.
  • the injection amounts from the fuel injection valves 11 and 12 are feedback-controlled based on the output signal of the air-fuel ratio sensor 27 so that the air-fuel ratio in the combustion chamber 5 becomes the stoichiometric air-fuel ratio. .
  • 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. 21 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 the 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. 8 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 operating state of the engine is an engine low load operating region I shown in FIG. When the engine operating state is in the engine low load operation region I shown in FIG.
  • step 84 the NO x storage amount ⁇ NOX is discriminated whether or not more than the first allowable the NO x storage amount MAXI is, when the NO x storage amount ⁇ NOX has not exceeded the first tolerance the NO x storage amount MAXI, the step Proceeding to 85, the air-fuel ratio in the combustion 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 the routine proceeds to step 86, where the air-fuel ratio in the combustion chamber 5 becomes temporarily rich. ⁇ 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. 19, 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 it is determined whether or not the NO x storage amount ⁇ NOX exceeds the second allowable NO x storage amount MAXII.
  • the routine proceeds to step 90, where the air-fuel ratio in the combustion chamber 5 is set to a lean air space that is predetermined according to the operating state of the engine. The fuel ratio is set. At this time, combustion is performed with the base air-fuel ratio lean. Note that the base air-fuel ratio at this time is smaller than the base air-fuel ratio in the engine low load operation region I.
  • step 89 when it is determined at step 89 that the NO x storage amount ⁇ NOX exceeds the second allowable NO x storage amount MAXII, the routine proceeds to step 91 where the air-fuel ratio in the combustion chamber 5 becomes temporarily rich. ⁇ NOX is cleared. At this time, NO x stored in the exhaust purification catalyst 22 is released from the exhaust purification catalyst 22.
  • 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. 19, the routine proceeds to step 92, 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 93 where the air-fuel ratio in the combustion chamber 5 is temporarily made rich. In contrast, 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 94. In step 94, the air-fuel ratio in the combustion chamber 5 is feedback-controlled to the stoichiometric air-fuel ratio.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Emergency Medicine (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

Un convertisseur catalytique à trois voies (20) possédant des capacités de stockage d'oxygène, et un convertisseur catalytique de purification de gaz d'échappement (22) sont disposés à l'intérieur d'un trajet de gaz d'échappement de moteur. Des convertisseurs catalytiques de métal noble (61, 62) sont supportés sur une surface d'écoulement de gaz d'échappement du convertisseur catalytique de purification de gaz d'échappement (22), une portion surface d'écoulement de gaz d'échappement basique est formée tout autour de ces convertisseurs catalytiques de métal noble (61, 62). Par commutation temporaire de pauvre à riche selon un cycle dans une plage de rapport air/carburant prédéterminé à l'intérieur d'une chambre de combustion (5) lors du fonctionnement du moteur, un NOx contenu dans un gaz d'échappement est purifié.
PCT/JP2012/070522 2012-08-10 2012-08-10 Dispositif de purification de gaz d'échappement pour moteur à combustion interne et à allumage par étincelle WO2014024311A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9845756B2 (en) 2012-07-27 2017-12-19 Toyota Jidosha Kabushiki Kaisha Exhaust gas control apparatus for internal combustion engine
CN110529274A (zh) * 2018-05-25 2019-12-03 丰田自动车株式会社 内燃机

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011118044A1 (fr) * 2010-03-23 2011-09-29 トヨタ自動車株式会社 Dispositif d'épuration de gaz d'échappement pour un moteur à combustion interne
WO2012014330A1 (fr) * 2010-07-28 2012-02-02 トヨタ自動車株式会社 Appareil d'épuration de gaz d'échappement pour moteur à combustion interne
WO2012111171A1 (fr) * 2011-02-18 2012-08-23 トヨタ自動車株式会社 Dispositif de purification de gaz d'échappement pour moteur à combustion interne

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011118044A1 (fr) * 2010-03-23 2011-09-29 トヨタ自動車株式会社 Dispositif d'épuration de gaz d'échappement pour un moteur à combustion interne
WO2012014330A1 (fr) * 2010-07-28 2012-02-02 トヨタ自動車株式会社 Appareil d'épuration de gaz d'échappement pour moteur à combustion interne
WO2012111171A1 (fr) * 2011-02-18 2012-08-23 トヨタ自動車株式会社 Dispositif de purification de gaz d'échappement pour moteur à combustion interne

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9845756B2 (en) 2012-07-27 2017-12-19 Toyota Jidosha Kabushiki Kaisha Exhaust gas control apparatus for internal combustion engine
CN110529274A (zh) * 2018-05-25 2019-12-03 丰田自动车株式会社 内燃机

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