US20070294998A1 - Control Method and Control Device for Exhaust Gas Control Apparatus - Google Patents

Control Method and Control Device for Exhaust Gas Control Apparatus Download PDF

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Publication number
US20070294998A1
US20070294998A1 US11/630,323 US63032305A US2007294998A1 US 20070294998 A1 US20070294998 A1 US 20070294998A1 US 63032305 A US63032305 A US 63032305A US 2007294998 A1 US2007294998 A1 US 2007294998A1
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catalyst
exhaust gas
temperature
ability
nox storage
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Kohei Yoshida
Kotaro Hayashi
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Toyota Motor Corp
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Toyota Motor Corp
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Assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA reassignment TOYOTA JIDOSHA KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HAYASHI, KOTARO, YOSHIDA, KOHEI
Publication of US20070294998A1 publication Critical patent/US20070294998A1/en
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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
    • F02D41/029—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 particulate filter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9413—Processes characterised by a specific catalyst
    • B01D53/9422—Processes characterised by a specific catalyst for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/96—Regeneration, reactivation or recycling of reactants
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0821—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with particulate filters
    • 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
    • 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
    • F01N3/0885—Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/10—Noble metals or compounds thereof
    • B01D2255/102—Platinum group metals
    • B01D2255/1025—Rhodium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/91—NOx-storage component incorporated in the catalyst
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/14—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories in relation to the exhaust system
    • F02M26/15—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories in relation to the exhaust system in relation to engine exhaust purifying apparatus
    • 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 invention relates to a control method and control device for an exhaust gas control apparatus including a catalyst that contains rhodium (Rh), and a particulate filter.
  • an exhaust gas control apparatus for a compression ignition internal combustion engine (i.e., diesel engine)
  • an exhaust gas control apparatus which is formed by integrally or separately arranging a catalyst that contains rhodium (Rh) and a particulate filter for trapping particulate matter (hereinafter, referred to as “PM”) in an exhaust system.
  • Rh rhodium
  • PM particulate filter for trapping particulate matter
  • the invention is made in light of the above-mentioned circumstances. It is therefore an object of the invention to provide a control method and control device which can appropriately recover a decreased reducing ability of a catalyst in an exhaust gas control apparatus for an internal combustion engine, the exhaust gas control apparatus being formed by integrally or separately arranging the catalyst that contains rhodium (Rh) and a particulate filter in an exhaust system of the internal combustion engine.
  • the exhaust gas control apparatus being formed by integrally or separately arranging the catalyst that contains rhodium (Rh) and a particulate filter in an exhaust system of the internal combustion engine.
  • a control method for an exhaust gas control apparatus formed by integrally or separately arranging a catalyst that contains rhodium (Rh) and a particulate filter in an exhaust system of an internal combustion engine, characterized in that the catalyst is placed in a reduction atmosphere in a course of decreasing a catalyst temperature after a PM trapping ability forcible recovery process for the particulate filter is completed.
  • the temperature of the particulate filter is increased by forcibly increasing the temperature of exhaust gas and/or forcibly increasing the amount of reaction heat in the catalyst.
  • the so-called PM trapping ability forcible recovery process is performed so as to oxidize and remove the PM trapped in the particulate filter.
  • the catalyst When the PM trapping ability forcible recovery process is performed, the catalyst is exposed to a high-temperature and lean atmosphere together with the particulate filter. Accordingly, rhodium (Rh) moves to the inside of a catalyst carrier. If rhodium (Rh) moves to the inside of the catalyst carrier, the reducing ability of the catalyst is decreased.
  • the catalyst is placed in the reduction atmosphere in a period, in which the temperature of the catalyst has been sufficiently decreased and re-heating of the catalyst need not be performed, in the course of decreasing the catalyst temperature after the PM trapping ability forcible recovery process is completed.
  • the decreased the reducing ability of the catalyst can be recovered by using heat obtained during the PM trapping ability forcible recovery process.
  • an extra temperature increasing process for recovering the decreased reducing ability of the catalyst need not be performed, and a decrease in the fuel efficiency is suppressed.
  • the decreased reducing ability of the catalyst is appropriately recovered, when the catalyst is exposed to the reduction atmosphere at a high temperature of approximately 400° C. or higher. Accordingly, the catalyst may be placed in the reduction atmosphere in a period, in which the catalyst temperature is approximately 400° C. or higher, in the course of decreasing the catalyst temperature after the PM trapping ability forcible recovery process is completed. In this case, an amount of reducing agent required to generate the reduction atmosphere can be minimized.
  • a NOx storage reduction catalyst may be used as the catalyst that contains rhodium (Rh). Since the NOx storage ability of the NOx storage reduction catalyst is limited, the NOx storage ability needs to be recovered when required, in the exhaust gas control apparatus including the NOx storage reduction catalyst.
  • rich-spike control As a method for recovering the NOx storage ability of the NOx storage reduction catalyst, so-called rich-spike control is effective.
  • an air-fuel ratio of the exhaust gas flowing into the catalyst is made rich by supplying a reducing agent into the exhaust gas flowing upstream of the catalyst.
  • the rich-spike control may be performed after the PM trapping ability forcible recovery process for the particulate filter is completed.
  • the rich-spike control is performed when the NOx reducing ability of the catalyst has been decreased, although the NOx stored in the NOx storage reduction catalyst is released, the released NOx cannot be reduced sufficiently. Accordingly, the NOx may be released into the air without being reduced. In addition, with an increase in the amount of NOx that has not been reduced, the amount of reducing agent that has not reacted with NOx may increase.
  • the catalyst is exposed to the high-temperature and rich atmosphere. Accordingly, the decreased NOx reducing ability of the catalyst may be recovered.
  • the air-fuel ratio of the exhaust gas is made rich intermittently, and the length of each period in which the air-fuel ratio of the exhaust gas is rich is relatively short. It is therefore difficult to sufficiently recover the decreased the NOx reducing ability of the catalyst.
  • the conventional type of rich-spike control is performed without the characteristics of rhodium (Rh) taken into consideration. Accordingly, the catalyst is not always placed in the rich atmosphere when the temperature of the catalyst in an appropriate temperature range.
  • the rich-spike control may be prohibited after the PM trapping ability forcible recovery process is completed, whereby the catalyst is placed in the reduction atmosphere.
  • an air-fuel ratio of the exhaust gas is made higher than that when the rich atmosphere is generated by the rich-spike control for the following reason.
  • Examples of a method for placing the catalyst in the reduction atmosphere include a method in which a small amount of reducing agent is supplied to the exhaust gas at intervals shorter than those in the rich-spike control, and a method in which an air-fuel ratio in the internal combustion engine is made low.
  • a process for recovering the NOx storage reduction catalyst from sulfur poisoning (hereinafter, referred to as a “sulfur poisoning recovery process for the NOx storage reduction catalyst”) may be performed subsequent to the PM trapping ability forcible recovery process.
  • the control according to the invention is different from the sulfur poisoning recovery process in the following point.
  • the catalyst is placed in the reduction atmosphere without forcibly increasing the temperature of the catalyst and without forcibly maintaining the temperature of the catalyst.
  • the catalyst is placed in the reduction atmosphere while the temperature of the catalyst is forcibly increased and maintained.
  • the catalyst is exposed to the high-temperature and rich atmosphere. Therefore the decreased NOx reducing ability of the catalyst can be recovered.
  • the control according to the invention is prohibited.
  • the control according to the invention is performed. In this case, the catalyst is prevented from unnecessarily being placed in the reduction atmosphere, and therefore the fuel efficiency is prevented from being decreased.
  • a control device for an exhaust gas control apparatus including a particulate filter provided in an exhaust system of an internal combustion engine, and a catalyst that is provided integrally with or separately from the particulate filter in the exhaust system and that contains rhodium, the control device being characterized by including recovery means for increasing a temperature of the particulate filter and a temperature of the catalyst, thereby forcibly recovering a PM trapping ability of the particulate filter; and NOx reducing ability recovery means for placing the catalyst in a reduction atmosphere in a course of decreasing the temperature of the catalyst after the PM trapping ability of the particulate filter is forcibly recovered.
  • “storage” used herein means retention of a substance (solid, liquid, gas molecules) in the form of at least one of adsorption, adhesion, absorption, trapping, occlusion, and others.
  • FIG. 1 is a view schematically showing a structure of an internal combustion engine to which the invention is applied;
  • FIG. 2 is a graph showing a temperature at which a NOx reducing ability of a NOx storage reduction catalyst is activated
  • FIG. 4 is a graph showing a concrete method for performing an exhaust gas enriching process.
  • An internal combustion engine 1 shown in FIG. 1 is a compression ignition internal combustion engine (i.e., diesel engine).
  • the internal combustion engine 1 is provided with an intake passage 2 and an exhaust passage 3 .
  • An intake throttle valve 4 is provided in the intake passage 2 .
  • a particulate filter 5 is provided in the exhaust passage 3 .
  • the particulate filter 5 supports a NOx storage reduction catalyst that contains rhodium (Rh).
  • a reducing agent supply valve 6 which injects fuel from the internal combustion engine 1 as a reducing agent, is provided in the exhaust passage 3 at a position upstream of the particulate filter 5 .
  • An exhaust gas temperature sensor 7 is provided in the exhaust passage 3 at a position downstream of the particulate filter 5 .
  • An EGR passage 8 permits communication between the intake passage 2 and the exhaust passage 3 .
  • An EGR valve 9 is provided in the EGR passage 8 .
  • Each of the intake throttle valve 4 , the reducing agent supply valve 6 , the exhaust gas temperature sensor 7 , and the EGR valve 9 is electrically connected to an ECU 10 .
  • the ECU 10 performs known controls such as fuel injection control and EGR control based on operation states of the exhaust gas temperature sensor 7 and the internal combustion engine 1 .
  • the ECU 10 also performs catalyst's NOx reducing ability recovery control that is a main feature of the invention. Hereafter, the catalyst's NOx reducing ability recovery control will be described in detail.
  • the ECU 10 Since the PM trapping ability of the particulate filter 5 is limited, the ECU 10 performs the PM trapping ability forcible recovery process before the limit of the PM trapping ability is reached. In the PM trapping ability forcible recovery process, the ECU 10 increases the temperature of the exhaust gas and/or increases the amount of reaction heat in the NOx storage reduction catalyst by performing post-injection and/or supplying fuel from the reducing agent supply valve 6 into the exhaust gas, thereby forcibly increasing the temperature of the particulate filter 5 .
  • the NOx storage reduction catalyst supported by the particulate filter 5 is also exposed to the high-temperature and rich atmosphere.
  • rhodium (Rh) contained in the NOx storage reduction catalyst moves to the inside of the catalyst carrier.
  • the NOx reducing ability of the NOx storage reduction catalyst especially, a hydrocarbon (HC) oxidizing ability
  • the NOx reducing ability of the NOx storage reduction catalyst is decreased. Namely, if the HC oxidizing ability of the NOx storage reduction catalyst is decreased, when the NOx storage ability of the NOx storage reduction catalyst is recovered, that is, when the rich spike control, in which fuel (hydrocarbon (HC)) is intermittently supplied from the reducing agent supply valve 6 into the exhaust gas, is performed, it becomes difficult for the hydrocarbon (HC) to transform into a reaction activated substance in the NOx storage reduction catalyst. Accordingly, the NOx released from the NOx storage reduction catalyst may be released into the air without being reduced, and the hydrocarbon supplied to the NOx storage reduction catalyst may be released into the air without reacting with NOx.
  • HC hydrocarbon
  • FIG. 2 is a graph showing the temperature at which the NOx reducing ability of the NOx storage reduction catalyst is activated.
  • the NOx reducing ability of the NOx storage reduction catalyst is activated at a temperature of approximately 300° C.
  • the NOx reducing ability of the NOx storage reduction catalyst is not activated until the temperature increases to be approximately 350° C. or higher.
  • the temperature of the exhaust gas released from the compression ignition internal combustion engine is approximately 300° C. at times other than a period in which the internal combustion engine is operated at high load. As described above, an increase in the temperature, at which the NOx reducing ability is activated, increases a possibility that the amounts of NOx and HC released into the air increase when the rich-spike control is performed.
  • Rhodium (Rh) which has moved to the inside of the catalyst carrier, outcrops to the surface of the catalyst carrier, when the catalyst is exposed to the reduction atmosphere at a high temperature of 400° C. or higher. Therefore, if the exhaust gas flowing in the NOx storage reduction catalyst is made rich after the temperature of the NOx storage reduction catalyst is increased to be 400° C. or higher, the decreased HC oxidizing ability can be recovered.
  • Examples of an effective method for increasing the temperature of the NOx storage reduction catalyst to be 400° C. or higher, that is, a temperature in a high temperature range include a method in which the temperature of the exhaust gas is increased by performing post injection and a method in which the amount of reaction heat in the NOx storage reduction catalyst is increased by supplying fuel into the exhaust gas.
  • a problem common to these methods that is, a decrease in the fuel efficiency.
  • the particulate filter 5 is placed in the reduction atmosphere (rich atmosphere) in the period in which the temperature of the NOx storage reduction catalyst is 400° C. or higher, in the course of decreasing the temperature of the catalyst after the PM trapping ability forcible recovery process is completed.
  • FIG. 3 is a flowchart showing the routine of the catalyst's NOx reducing ability recovery control.
  • the catalyst's NOx reducing ability recovery control routine is stored in ROM of the ECU 10 in advance.
  • the catalyst's NOx reducing ability recovery control routine is an interrupt routine that is performed by the ECU 10 when the PM trapping ability forcible recovery process is completed.
  • the ECU 10 initially determines in step S 101 whether a PM trapping ability forcible recovery completion flag shows “1”.
  • the PM trapping ability forcible recovery completion flag is stored in RAM or the like in advance. When the PM trapping ability forcible recovery process is completed, “1” is stored. When the catalyst's NOx reducing ability recovery control is completed, “0” is stored.
  • step S 101 When it is determined in step S 101 that the PM trapping ability forcible recovery completion flag shows “0”, the ECU 10 ends the routine. On the other hand, when it is determined in step S 101 that the PM trapping ability forcible recovery completion flag shows “1”, the ECU 10 then performs step S 102 .
  • step S 102 the ECU 10 receives a signal Tout which indicates a temperature of the exhaust gas released from the particulate filter 5 (hereinafter, referred to as “an outflow exhaust gas temperature Tout”), and which is output from the exhaust gas temperature sensor 7 .
  • a signal Tout which indicates a temperature of the exhaust gas released from the particulate filter 5 (hereinafter, referred to as “an outflow exhaust gas temperature Tout”), and which is output from the exhaust gas temperature sensor 7 .
  • step S 103 the ECU 10 determines whether the outflow exhaust gas temperature Tout received in step S 102 is equal to or higher than a predetermined temperature Ts (e.g., 400° C.).
  • a predetermined temperature Ts e.g. 400° C.
  • step S 103 When it is determined in step S 103 that the outflow exhaust gas temperature Tout is equal to nor higher than the predetermined temperature (Tout ⁇ Ts), the ECU estimates that a bed temperature of the NOx storage reduction catalyst is lower than the predetermined temperature Ts, and then performs step S 110 .
  • step S 110 the ECU 10 changes the value of the PM trapping ability forcible recovery completion flag to “0”, and then ends the routine.
  • step S 103 when it is determined in step S 103 that the outflow exhaust gas temperature Tout is equal to or higher than the predetermined temperature Ts (Tout ⁇ Ts), the ECU 10 estimates that the bed temperature of the NOx storage reduction catalyst is equal to or higher than the predetermined temperature T s , and then performs step S 104 .
  • step S 104 the ECU 10 prohibits the rich-spike control.
  • step S 105 the ECU 10 performs an exhaust gas enriching process for making the exhaust gas flowing into the particulate filter 5 rich.
  • the ECU 10 controls the reducing agent supply valve 6 such that fuel is intermittently supplied into the exhaust gas.
  • the ECU 10 controls the reducing agent supply valve 6 such that the amount of fuel supplied from the reducing agent supply valve 6 during each supply become smaller than that in the rich-spike control, and the interval between the fuel supplies become shorter than that in the rich-spike control, as shown in FIG. 4 .
  • the amount of fuel supplied from the reducing agent supply valve 6 during each supply is made smaller than that in the rich-spike control for the following reason. If the same amount of hydrocarbon (HC) as that in the rich-spike control is supplied to the NOx storage reduction catalyst when the HC oxidizing ability of the NOx storage reduction catalyst has been decreased, the amount of NOx released from the NOx storage reduction catalyst increases, and the amount of NOx released into the air without being reduced also increases.
  • HC hydrocarbon
  • the amount of fuel supplied from the reducing agent supply valve 6 during each supply is made smaller than that in the rich-spike control also for the following reason. If the same amount of hydrocarbon (HC) as that in the rich-spike control is supplied to the NOx storage reduction catalyst when the HC oxidizing ability of the NOx storage reduction catalyst has been decreased, the amount of hydrocarbon (HC) that is released into the air without reacting with NOx may increase.
  • the interval between the fuel supplies is made shorter than that in the rich-spike control for the following reason.
  • the temperatures of the particulate filter 5 and the NOx storage reduction catalyst rapidly decrease after the PM trapping ability forcible recovery process is completed. Accordingly, if the fuel is supplied with the same intervals as those in the rich-spike control, the temperature of the NOx storage reduction catalyst may decrease to be the predetermined temperature Ts or lower, before the HC oxidizing ability is recovered.
  • step S 106 the ECU 10 receives the signal (i.e., outflow exhaust gas temperature) Tout output from the exhaust gas temperature sensor 7 again.
  • step S 107 the ECU 10 determines whether the outflow exhaust gas temperature Tout received in step S 106 has decreased to be lower than the predetermined temperature Ts.
  • step S 107 When it is determined in step S 107 that the outflow exhaust gas temperature Tout has not decreased to be lower than the predetermined temperature Ts (Tout ⁇ Ts), the ECU 10 determines that the bed temperature of the NOx storage reduction catalyst is still equal to or higher than the predetermined temperature Ts, and then performs step S 105 and the following steps again.
  • step S 107 when it is determined in step S 107 that the outflow exhaust gas temperature Tout has decreased to be lower than the predetermined temperature Ts (Tout ⁇ Ts), the ECU 10 determines that the bed temperature of the NOx storage reduction catalyst has decreased to be lower than the predetermined temperature Ts, and then performs step S 108 .
  • step S 108 the ECU 10 ends the exhaust gas enriching process.
  • step S 109 the ECU 10 removes prohibition of the rich-spike control.
  • step S 110 the ECU 10 changes the value of the PM trapping ability forcible recovery process completion flag to “0”.
  • the ECU 10 When the ECU 10 performs the catalyst's NOx reducing ability recovery control routine in the above-mentioned manner, the HC oxidizing ability of the NOx storage reduction catalyst can be recovered by using the heat obtained during the PM trapping ability forcible recovery process. As a result, a decrease in the fuel efficiency due to an increase in the temperature of the NOx storage reduction catalyst can be suppressed.
  • the amount of fuel supplied into the exhaust gas during each supply is made smaller than that in the rich-spike control. Also, in the embodiment, the interval between the fuel supplies is made shorter than that in the rich-spike control. Accordingly, the HC oxidizing ability of the NOx storage reduction catalyst can be recovered in the period in which the bed temperature of the NOx storage reduction catalyst is equal to or higher than the predetermined temperature Ts. In addition, the amount of NOx released into the air without being reduced and the amount of hydrocarbon (HC) that are released into the air without reacting with NOx can be decreased.
  • the bed temperature of the NOx storage reduction catalyst may be maintained at a temperature equal to or higher than the predetermined temperature Ts for a long time due to the heat generated by reaction of rhodium (Rh) and hydrocarbon (HC).
  • any one of the following methods may be employed; (1) the exhaust gas enriching process is completed when the performance time of the exhaust gas enriching process becomes equal to or longer than a predetermined time, (2) the temperature of the NOx storage reduction catalyst is gradually decreased by decreasing the fuel supply amount with an increase in the number of times of fuel supply, and (3) an interval is provided every time fuel supply has been performed a predetermined number of times such that the temperature of the NOx storage reduction catalyst is decreased in a stepwise manner.
  • supplying fuel into the exhaust gas from the reducing agent supply valve 6 is employed as a concrete method for performing the exhaust gas enriching process.
  • the air-fuel ratio of the exhaust gas released from the internal combustion engine 1 may be decreased by increasing the amount of the EGR gas.
  • the particulate filter 5 and the NOx storage reduction catalyst are integrally provided in the exhaust passage 3 .
  • the particulate filter 5 and the NOx storage reduction catalyst may be separately provided in the exhaust passage 3 .
  • the particulate filter 5 and the NOx storage reduction catalyst may be provided in the exhaust passage 3 in series (preferably, the NOx storage reduction catalyst is provided upstream of the particulate filter 5 ).
  • the reducing agent supply valve 6 needs to be provided upstream of the NOx storage reduction catalyst.
  • sulfur poisoning i.e., S poisoning
  • the sulfur poisoning recovery process may be performed subsequent to the PM trapping ability forcible recovery process.
  • the catalyst In the sulfur poisoning recovery process, the catalyst is placed in the rich atmosphere while the temperature of the NOx storage reduction catalyst is maintained at a high temperature. Accordingly, the decreased HC oxidizing ability of the NOx storage reduction catalyst can be recovered.
  • the ECU 10 prohibits the catalyst's NOx reducing ability recovery control.
  • the ECU 10 performs the catalyst's NOx reducing ability recovery control.
  • the catalyst's NOx reducing ability recovery control is prevented from being unnecessarily performed. Accordingly, fuel consumption due to the catalyst's NOx reducing ability recovery control can be suppressed.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • General Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biomedical Technology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Processes For Solid Components From Exhaust (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)
  • Filtering Of Dispersed Particles In Gases (AREA)
US11/630,323 2004-07-05 2005-06-30 Control Method and Control Device for Exhaust Gas Control Apparatus Abandoned US20070294998A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2004-198310 2004-07-05
JP2004198310A JP4265497B2 (ja) 2004-07-05 2004-07-05 排気浄化装置の制御方法
PCT/IB2005/001861 WO2006006031A1 (fr) 2004-07-05 2005-06-30 Procede et dispositif de regulation pour un appareil de regulation du gaz d'echappement

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US (1) US20070294998A1 (fr)
EP (1) EP1781909A1 (fr)
JP (1) JP4265497B2 (fr)
KR (1) KR100828986B1 (fr)
CN (1) CN100445524C (fr)
WO (1) WO2006006031A1 (fr)

Cited By (1)

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US9440194B2 (en) 2012-06-19 2016-09-13 Toyota Jidosha Kabushiki Kaisha Exhaust gas purification apparatus for an internal combustion engine

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US7788910B2 (en) * 2007-05-09 2010-09-07 Ford Global Technologies, Llc Particulate filter regeneration and NOx catalyst re-activation
JP4502038B2 (ja) * 2008-04-14 2010-07-14 トヨタ自動車株式会社 内燃機関の制御システム
JP2015048767A (ja) * 2013-08-30 2015-03-16 本田技研工業株式会社 内燃機関の制御装置
US10690079B2 (en) * 2017-12-12 2020-06-23 GM Global Technology Operations LLC Method for diagnosing and controlling ammonia oxidation in selective catalytic reduction devices
JP2019157667A (ja) * 2018-03-08 2019-09-19 いすゞ自動車株式会社 排気浄化装置、車両および排気浄化制御装置

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US20010052232A1 (en) * 2000-05-12 2001-12-20 Michael Hoffmann Method for removing nitrogen oxides and particulates from the lean exhaust gas of an internal combustion engine and exhaust and exhaust gas emission system
US20030113249A1 (en) * 2001-12-18 2003-06-19 Hepburn Jeffrey Scott System and method for removing SOx and particulate matter from an emission control device
US20030121249A1 (en) * 2001-11-30 2003-07-03 Foster Michael Ralph Engine cylinder deactivation to improve the performance of exhaust emission control systems
US20040067176A1 (en) * 2002-03-28 2004-04-08 Marcus Pfeifer Particle filter having a catalytically active coating to accelerate burning off accumulated soot particles during a regeneration phase
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US20010052232A1 (en) * 2000-05-12 2001-12-20 Michael Hoffmann Method for removing nitrogen oxides and particulates from the lean exhaust gas of an internal combustion engine and exhaust and exhaust gas emission system
US20030121249A1 (en) * 2001-11-30 2003-07-03 Foster Michael Ralph Engine cylinder deactivation to improve the performance of exhaust emission control systems
US20030113249A1 (en) * 2001-12-18 2003-06-19 Hepburn Jeffrey Scott System and method for removing SOx and particulate matter from an emission control device
US20040067176A1 (en) * 2002-03-28 2004-04-08 Marcus Pfeifer Particle filter having a catalytically active coating to accelerate burning off accumulated soot particles during a regeneration phase
US20040216451A1 (en) * 2002-11-21 2004-11-04 Labarge William J. Exhaust system and method of thermal management

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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CN100445524C (zh) 2008-12-24
KR100828986B1 (ko) 2008-05-14
JP2006017083A (ja) 2006-01-19
JP4265497B2 (ja) 2009-05-20
CN1981117A (zh) 2007-06-13
WO2006006031A1 (fr) 2006-01-19
EP1781909A1 (fr) 2007-05-09
KR20070039918A (ko) 2007-04-13

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