US20090229256A1 - Control unit for exhaust gas purifying apparatus - Google Patents

Control unit for exhaust gas purifying apparatus Download PDF

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Publication number
US20090229256A1
US20090229256A1 US12/089,848 US8984806A US2009229256A1 US 20090229256 A1 US20090229256 A1 US 20090229256A1 US 8984806 A US8984806 A US 8984806A US 2009229256 A1 US2009229256 A1 US 2009229256A1
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Prior art keywords
catalysts
control
catalyst
elimination
control unit
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Abandoned
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US12/089,848
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English (en)
Inventor
Hisanobu Suzuki
Kenji Kawai
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Toyota Industries Corp
Toyota Motor Corp
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Toyota Industries Corp
Toyota Motor Corp
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Assigned to KABUSHIKI KAISHA TOYOTA JIDOSHOKKI, TOYOTA JIDOSHA KABUSHIKI KAISHA reassignment KABUSHIKI KAISHA TOYOTA JIDOSHOKKI ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KAWAI, KENJI, SUZUKI, HISANOBU
Publication of US20090229256A1 publication Critical patent/US20090229256A1/en
Abandoned legal-status Critical Current

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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
    • F02D41/028—Desulfurisation of NOx traps or adsorbent
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • 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
    • F01N13/0097—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 the purifying devices are arranged in a single housing
    • 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
    • F01N13/011—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 purifying devices arranged in parallel
    • 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
    • F01N13/08—Other arrangements or adaptations of exhaust conduits
    • F01N13/10—Other arrangements or adaptations of exhaust conduits of exhaust manifolds
    • F01N13/107—More than one exhaust manifold or exhaust collector
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/025—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust
    • F01N3/0253—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust adding fuel to exhaust gases
    • 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
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842—Nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—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
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration, e.g. detection of clogging
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
    • F02B37/007—Engines characterised by provision of pumps driven at least for part of the time by exhaust with exhaust-driven pumps arranged in parallel, e.g. at least one pump supplying alternatively
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2430/00—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics
    • F01N2430/08—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by modifying ignition or injection timing
    • F01N2430/085—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by modifying ignition or injection timing at least a part of the injection taking place during expansion or exhaust stroke
    • 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
    • F02D2200/0802—Temperature of the exhaust gas treatment apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1439—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the position of the sensor
    • F02D41/1441—Plural sensors
    • F02D41/1443—Plural sensors with one sensor per cylinder or group of cylinders
    • 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
    • F02M26/02—EGR systems specially adapted for supercharged engines
    • F02M26/08—EGR systems specially adapted for supercharged engines for engines having two or more intake charge compressors or exhaust gas turbines, e.g. a turbocharger combined with an additional compressor
    • 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
    • F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/23—Layout, e.g. schematics
    • F02M26/24—Layout, e.g. schematics with two or more coolers
    • 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
    • F02M26/38—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with two or more EGR valves disposed in parallel
    • 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
    • F02M26/42—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories having two or more EGR passages; EGR systems specially adapted for engines having two or more cylinders
    • F02M26/44—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories having two or more EGR passages; EGR systems specially adapted for engines having two or more cylinders in which a main EGR passage is branched into multiple passages
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • the present invention relates to a control unit of an exhaust gas purifying apparatus that purifies exhaust gas generated by an engine using a catalyst.
  • An exhaust gas purifying apparatus that purifies exhaust gas caused by an internal combustion engine (hereinafter, referred to also as an engine) such as a diesel engine includes, for example, a NOx storage reduction catalyst and a particulate filter, which collects particulate matter (hereinafter, referred to as PM) from the exhaust gas.
  • an engine such as a diesel engine
  • PM particulate matter
  • the NOx storage reduction catalyst stores NOx if the content of oxygen in the exhaust gas is great and reduces NOx to NO 2 or NO and releases the substance if the content of oxygen in the exhaust gas is small and the amount of reducing agent (for example, unburned elements of fuel (HC)) is great.
  • a particulate filter hereinafter, referred to as the filter
  • a DPF diesel particulate filter
  • DPNR diesel particulate-NOx reduction system
  • the exhaust gas purifying apparatus which includes the NOx storage reduction catalyst and the filter arranged in an exhaust passage, involves various types of control (hereinafter, referred to generally as catalyst control) including NOx reduction control, sulfur release control, and PM elimination control.
  • catalyst control various types of control including NOx reduction control, sulfur release control, and PM elimination control.
  • NOx reduction control which is one type of the catalyst control
  • fuel is fed to the NOx storage reduction catalyst.
  • NOx stored in the catalyst is thus caused to react with the fuel elements (HC) and reduced through such reaction.
  • the NOx storage reduction catalyst is recovered from sulfur poisoning by desorbing SOx from the NOx storage reduction catalyst.
  • it is effective to expose the NOx storage reduction catalyst in the atmosphere in which the air-fuel ratio is slightly richer than the stoichiometric air-fuel ratio after the catalyst has been heated to a predetermined temperature (for example, 600 to 700° C.).
  • a predetermined temperature for example, 600 to 700° C.
  • fuel is supplied to the catalyst after the catalyst has been heated through, for example, switching of combustion states of the engine. In this manner, the fuel is exposed to the atmosphere of a rich air-fuel ratio, and the sulfur components are desorbed from the catalyst.
  • the sulfur release control may involve supply of fuel to the catalyst to increase the temperature of the catalyst.
  • the temperature of the catalyst (catalyst bed temperature) is raised by, for example, regulating the combustion state of the engine. This promotes oxidization (burning) of the PM deposited on the catalyst such as a DPNR catalyst.
  • a predetermined temperature which is, for example, approximately 600 to 700° C.
  • V type multicylinder engine As a type of diesel engine, there is a V type multicylinder engine that includes left and right banks each having a plurality of cylinders. The sets of the cylinders, each of which forms the corresponding one of the banks, are connected to exhaust passages of different systems.
  • the V type multicylinder engine includes an intake manifold, or a portion of an intake passage, which is provided commonly for the left and right banks to maintain the amounts of the intake air supplied to the banks at equal levels.
  • This type of engine also performs the PM elimination control, the sulfur release control, and the NOx reduction control, which have been described so far, in response to a request for the catalyst control.
  • Patent Document 1 which is listed below, describes a method as a technique related to the catalyst control of the V type multicylinder engine.
  • the technique of Patent Document 1 performs control in such a manner as to suppress variation of flow rates of exhaust gas between multiple cylinders. This prevents delay in recovery of exhaust gas purifying performance and wasteful consumption of energy.
  • the flow rates of the exhaust gas flowing to the catalysts of the systems of the left and right banks may vary between the systems due to a difference (which is, for example, varied sizes of fine pores defined in the catalysts, varied flow characteristics, and varied performances of turbochargers) between the systems.
  • a difference which is, for example, varied sizes of fine pores defined in the catalysts, varied flow characteristics, and varied performances of turbochargers
  • Such variation of the exhaust gas flow rates varies the speeds of deterioration of the catalysts depending on the deposit amount of PM and the degree of sulfur poisoning between the left and right systems.
  • recovery of the catalyst, or the catalyst control is requested at different timings between the left and right banks. In this case, if the catalyst control is requested only for one of the systems, it is impossible to switch the combustion state of the bank of the system requesting such control separately from the other system.
  • the intake manifold, which forms a portion of the intake passage, of the V type diesel engine is provided commonly for the banks in order to maintain the intake air amounts of the banks at equal levels. This makes it impossible to switch the combustion state of one of the banks independently from the other through air-fuel ratio control (rich control) performed by adjusting a throttle valve (an intake air throttle valve).
  • the PM elimination control and the sulfur release control each involve PM elimination combustion and sulfur release combustion. This increases the fuel consumption.
  • the PM elimination/sulfur release combustion is carried out to recover the catalyst of the system that requests the catalyst control every time such request is generated, the recovery is performed for repeated times and the fuel consumption is increased.
  • Patent Document 1 Japanese Laid-Open Patent Publication No. 2005-036663
  • the present invention provides a control unit of an exhaust gas purifying apparatus used in an internal combustion engine having a plurality of sets of cylinders. Different exhaust systems are each connected to one of the sets of the cylinders, and the exhaust gas purifying apparatus includes catalysts each provided in one of the exhaust systems to purify exhaust gas.
  • the control unit performs a PM elimination control or a sulfur release control on the catalysts using a common procedure.
  • the present invention also provides a method for controlling an exhaust gas purifying apparatus used in an internal combustion engine having a plurality of sets of cylinders. Different exhaust systems are each connected to one of the sets of the cylinders. The method includes: purifying exhaust gas by means of catalysts each provided in one of the exhaust systems; and performing a PM elimination control or a sulfur release control on the catalysts using a common procedure.
  • FIG. 1 is a schematic diagram showing one embodiment of the present invention
  • FIG. 2 is a flowchart representing the content of PM elimination/sulfur release control executed by an ECU
  • FIG. 3 is a flowchart representing the content of NOx reduction control performed by the ECU
  • FIG. 4 is a timing chart representing the energization duration, the requested number of multiple addition cycles, and the addition interval for addition of fuel;
  • FIG. 5 is a map representing a bed temperature correction coefficient
  • FIG. 6 is a schematic view showing an engine having four systems of exhaust passages.
  • FIG. 1 An example of an engine in which the present invention is employed will hereafter be explained with reference to FIG. 1 .
  • an engine 1 is a V type eight cylinders diesel engine having a left bank 2 L and a right bank 2 R, each of which is. configured by four cylinders 3 .
  • the banks 2 L, 2 R are arranged in a V shaped manner.
  • the engine 1 includes injectors 4 , each of which injects fuel directly into a combustion chamber of the corresponding one of the cylinders 3 (cylinders #1, #2, #3, #4, #5, #6, #7, #8).
  • Each injector 4 is an electromagnetic on-off valve that opens when energized (supplied with voltage). The timings at which the injectors 4 become open are regulated by an ECU (electronic control unit) 100 .
  • the engine 1 has an intake manifold commonly provided for the left and right banks 2 L, 2 R, and an exhaust manifold 11 L and an exhaust manifold 11 R, which are arranged for the left bank 2 L and the right bank 2 R, respectively.
  • the exhaust system of the left bank 2 L may be referred to as a first system and the exhaust system of the right bank 2 R may be referred to as a second system.
  • An intake passage 5 is connected to the engine 1 to introduce intake air to the cylinders 3 .
  • An air cleaner 50 is connected to the intake passage 5 .
  • the intake passage 5 is branched into a branch line 5 L and a branch line 5 R at a position downstream from the air cleaner 50 .
  • a compressor portion 7 a of a turbocharger 7 L and a compressor portion 7 a of a turbocharger 7 R are arranged in the branch line 5 L and the branch line 5 R, respectively.
  • An intercooler 6 is connected to the branch lines 5 L, 5 R at a position downstream from the compressor portions 7 a.
  • the intercooler 6 is connected to the intake manifold 10 through a common intake passage 5 C.
  • An electronically controlled throttle valve (an intake air throttle valve) 9 is provided in the common intake passage 5 C.
  • EGR lines 14 L, 14 R which will be explained later, are connected to the common intake passage 5 C at a position downstream from the throttle valve 9 .
  • An air flow meter 8 L is arranged in the branch line 5 L at a position upstream from the compressor portion 7 a of the turbocharger 7 L.
  • An air flow meter 8 R is arranged in the branch line 5 R at a position upstream from the compressor portion 7 a of the turbocharger 7 R.
  • a fuel adding valve 12 L is arranged in the exhaust manifold 11 L connected to the left bank 2 L.
  • a fuel adding valve 12 R is connected to the exhaust manifold 11 R connected to the right bank 2 R.
  • Each of the fuel adding valves 12 L, 12 R is an electromagnetic on-off valve that opens when energized (supplied with voltage) to add fuel to the exhaust system of the corresponding one of the left and right banks 2 L, 2 R.
  • the timings at which each fuel adding valve 12 L, 12 R becomes open are regulated by the ECU 100 .
  • An exhaust passage 13 L and an exhaust passage 13 R are connected to the exhaust manifold 11 L and the exhaust manifold 11 R, respectively.
  • a turbine portion 7 b of the turbocharger 7 L is provided in the exhaust passage 13 L.
  • a turbine portion 7 b of the turbocharger 7 R is provided in the exhaust passage 13 R.
  • Each of the turbochargers 7 L, 7 R is a variable nozzle type turbocharger and has a variable nozzle vane mechanism at the side corresponding to the corresponding one of the turbine portions 7 b. By adjusting the opening degree of the variable nozzle vane mechanism, charging pressure of the engine 1 is changed.
  • the ECU 100 regulates the opening degree of the variable nozzle vane mechanism.
  • An EGR line 14 L and an EGR line 14 R connect the exhaust manifold 11 L and the exhaust manifold 11 R, respectively, to the common intake passage 5 C.
  • the EGR line 14 L receives an EGR cooler 15 L cooling EGR gas and an EGR valve 16 L, which adjusts the flow rate of EGR.
  • the EGR line 14 R accommodates an EGR cooler 15 R cooling the EGR gas and an EGR valve 16 R adjusting the flow rate of EGR.
  • the opening degree of each of the EGR valves 16 L, 16 R is adjusted by the ECU 100 .
  • An NSR (NOx storage reduction) catalyst 17 L, a DPNR catalyst 18 L, and a sweeper 19 L are arranged in the exhaust passage 13 L at positions downstream from the turbocharger 7 L.
  • An NSR catalyst 17 R, a DPNR catalyst 18 R, and a sweeper 19 R are arranged in the exhaust passage 13 R at positions downstream from the turbocharger 7 R.
  • Each of the NSR catalysts 17 L, 17 R is a NOx storage reduction catalyst formed by, for example, alumina (Al 2 O 3 ) as a carrier supporting alkaline metal such as potassium (K), sodium (Na), lithium (Li), or cesium (Cs), alkaline earth such as barium (Ba) or calcium (Ca), rare earth such as lantern (La) and yttrium (Y), and precious metal such as platinum (Pt).
  • alkaline metal such as potassium (K), sodium (Na), lithium (Li), or cesium (Cs)
  • alkaline earth such as barium (Ba) or calcium (Ca)
  • rare earth such as lantern (La) and yttrium (Y)
  • precious metal such as platinum (Pt).
  • Each NSR catalyst 17 L, 17 R stores NOx if the content of oxygen in the exhaust gas is great and reduces NOx to NO 2 or NO, and releases the substance if the content of oxygen in the exhaust gas is small and the content of reducing agents (such as unburned components of fuel (HC)) is great.
  • the NOx released as No 2 or NO is further reduced to N 2 through rapid reaction with HC or CO contained in the exhaust gas.
  • HC and CO are oxidized to H 2 O or CO 2 .
  • Each of the DPNR catalysts 18 L, 18 R is formed by, for example, a porous ceramic structure supporting a NOx storage reduction catalyst and collects PM from the exhaust gas as PM passes through a porous wall. If the air-fuel ratio of the exhaust gas is lean, NOx contained in the exhaust gas is stored by the NOx storage reduction catalyst. If the air-fuel ratio is rich, the stored NOx is reduced and released.
  • Each DPNR catalyst 18 L, 18 R supports a catalyst (for example, an oxidation catalyst including precious metal such as platinum as a main component) that oxidizes and burns the collected PM.
  • Each of the sweeper 19 L, 19 R is an oxidation catalyst and oxidizes HC and CO to purify the exhaust gas.
  • a first exhaust gas temperature sensor 21 L is arranged between the NSR catalyst 17 L and the DPNR catalyst 18 L.
  • a first exhaust gas temperature sensor 21 R is provided between the NSR catalyst 17 R and the DPNR catalyst 18 R.
  • a second exhaust gas temperature sensor 22 L and an air-fuel ratio sensor 23 L are provided downstream from the DPNR catalyst 18 L.
  • a second exhaust gas temperature sensor 22 R and an air-fuel ratio sensor 23 R are provided downstream from the DPNR catalyst 18 R.
  • a pressure difference sensor 24 L detects the difference in pressure (upstream-downstream pressure difference) between the upstream side and the downstream side of the DPNR catalyst 18 L.
  • the ECU 100 includes a CPU, a ROM, a RAM, and a backup RAM.
  • the ROM stores various control programs and maps, with reference to which the control programs are executed.
  • the CPU performs calculation procedures in accordance with the control programs and the maps, which are stored in the ROM.
  • the RAM is a memory that temporarily stores results of calculations by the CPU and data provided by the sensors.
  • the backup memory is a non-volatile memory that stores data to be maintained after the engine 1 is stopped.
  • the air flow meters 8 L, BR, the first exhaust gas temperature sensors 21 L, 21 R, the second exhaust gas temperature sensors 22 L, 22 R, the air-fuel ratio sensors 23 L, 23 R, the pressure difference sensors 24 L, 24 R, a coolant temperature sensor that detects the temperature of coolant of the engine 1 , a crank position sensor that detects the speed of the engine 1 , and various other sensors including an accelerator pedal position sensor are connected to the ECU 100 .
  • the ECU 100 Based on the outputs provided by the above-listed sensors, the ECU 100 carries out various control procedures by controlling operations of the injectors 4 , the throttle valve 9 , the variable nozzle vane mechanisms of the turbochargers 7 L, 7 R, and the EGR valves 16 l, 16 R. Also, the ECU 100 performs the following catalyst control.
  • the ECU 100 performs PM elimination control, sulfur release control, and NOx reduction control. Specifically, in the PM elimination control, PM deposited on the DPNR catalysts 18 L, 18 R are oxidized. In the sulfur release control, the NOx storage reduction catalysts of the NSR catalysts 17 L, 17 R and the DPNR catalysts 18 L, 18 R are recovered from S poisoning. In the NOx reduction control, NOx stored in the NOx storage reduction catalysts of the NSR catalysts 17 L, 17 R and the DPNR catalysts 18 L, 18 R are reduced. In the following, the PM elimination control, the sulfur release control, and the NOx reduction control will be explained.
  • the ECU 100 estimates the deposit amount of PM deposited on the DPNR catalysts 18 L, 18 R.
  • a map is defined from PM discharge amounts of the engine corresponding to the engine speed and the fuel injection amount, which are determined in advance through tests or the like.
  • the PM deposit amount is estimated by integrating the PM discharge amounts of the engine, which is obtained with reference to the map.
  • the PM deposit amount is estimated based on an integrated value of the intake air amount.
  • the PM deposit amount is estimated using one of the DPNR catalyst 18 L, 18 R exhibiting the greater PM deposit amount as a reference. This provides an estimated PM deposit amount corresponding to a greatest possible value, in order to prevent incomplete burning of the PM deposited on the DPNR catalysts 18 L, 18 R.
  • the catalyst representing a smaller value of the intake air amount (the greater PM deposit amount), which is determined based on detection signals of the air flow meters 8 L, 8 R arranged in the branch lines 5 L, 5 R of the intake passage 5 , is used as the reference.
  • the PM deposit amount is estimated by integrating the intake air amounts of the reference catalyst.
  • the ECU 100 determines that the DPNR catalysts 18 L, 18 R needs to be immediately recovered if the estimated PM amount exceeds a predetermined reference value (a threshold deposit amount). At this stage, the ECU 100 performs the PM elimination control, which will be explained later.
  • a predetermined reference value a threshold deposit amount
  • the ECU 100 monitors signals output by the pressure difference sensors 24 L, 24 R arranged in the first and second systems.
  • the ECU 100 compares the upstream-downstream pressure differences of the DPNR catalysts 18 L, 18 R obtained from the output signals of the pressure difference sensors 24 L, 24 R with a predetermined threshold value. If the upstream-downstream pressure difference of either one of the DPNR catalysts 18 L, 18 R exceeds the threshold value before the estimated PM deposit amount reaches the reference value, the ECU 100 starts the PM elimination at this stage.
  • the ECU 100 estimates the S poisoning amounts of the NOx storage reduction catalysts of the NSR catalysts 17 L, 17 R and the DPNR catalysts 18 L, 18 R.
  • a map is defined from the S poisoning amounts corresponding to the engine speed and the fuel injection amount, which are determined in advance through tests or the like.
  • the S poisoning amounts are estimated by integrating the S poisoning amount, which is obtained with reference to the map.
  • the ECU 100 determines that recovery from S poisoning needs to be immediately performed if an estimated value of the S poisoning amount exceeds a predetermined value (a threshold estimation amount). The ECU 100 then carries out the sulfur release control, which will be described later.
  • the PM elimination/sulfur release control which is carried out by the ECU 100 , will now be explained with reference to the flowchart of FIG. 2 .
  • the PM elimination/sulfur release control routine is performed repeatedly at predetermined intervals.
  • step ST 1 it is determined whether the PM elimination or the sulfur release needs to be immediately carried out using the above-described determination method. If the determination is negative, the routine is suspended. If positive determination is made in step ST 1 , it is determined whether the control that has been determined to need to be carried out corresponds to the “PM elimination control” in step ST 2 . If it is determined that the “PM elimination control” needs to be immediately performed, step ST 3 is carried out. If the determination of step ST 2 is negative, it is determined that the “sulfur release control” needs to be immediately carried out and step ST 11 is performed.
  • step ST 3 the catalyst bed temperatures of the DPNR catalysts 18 L, 18 R are estimated using the output signals of the first exhaust gas temperature sensors 21 L, 21 R. It is then determined whether the lower value of these estimated catalyst bed temperatures corresponds to a temperature required for the PM elimination (which is, for example, approximately 350° C.). If the determination of step ST 3 is positive, it is determined that the PM elimination can be carried out smoothly. Step ST 5 is then performed.
  • step ST 3 If the determination of step ST 3 is negative, the combustion state of the engine 1 is switched (to a PM elimination combustion mode) in step ST 4 , in order to increase the catalyst bed temperatures.
  • Step ST 5 is then carried out.
  • the air-fuel ratio (A/F) may be decreased by reducing the intake air amount by means of the throttle valve 9 .
  • the EGR amount may be increased or the fuel injection timings may be retarded.
  • a PM elimination amount is calculated.
  • the PM elimination amount is obtained with reference to a map defined through tests and calculations using the catalyst bed temperatures and a PM oxidization speed as parameters.
  • the PM elimination amount is determined using the estimated catalyst bed temperature value of one of the catalysts exhibiting the lower catalyst bed temperature, the DPNR catalyst 18 L of the first system or the second DPNR catalyst 18 R of the second system.
  • a requested fuel addition amount is then obtained from the calculated PM elimination amount. Based on the requested fuel addition amount, energization durations (fuel adding durations) of the fuel adding valves 12 L, 12 R, a requested number of multiple addition cycles, and an addition interval (see FIG. 4 ) are determined (step ST 6 ).
  • step ST 7 based on the energization duration, the requested number of multiple addition cycles, and the addition interval, which have been obtained in step ST 6 , operation of the fuel adding valve 12 L of the first system and operation of the fuel adding valve 12 R of the second system are controlled in accordance with a common procedure to carry out the PM elimination.
  • the PM elimination control is carried out in the first and second systems in accordance with the common procedure.
  • step ST 8 it is determined whether a condition for ending the PM elimination control is satisfied in step ST 8 . Specifically, it is determined whether the amount of the fuel added since starting of the PM elimination control has reached the requested fuel addition amount. If the determination is positive, the fuel addition is ended and the routine is also suspended.
  • step ST 2 If the determination of step ST 2 is negative and it is determined that the “sulfur release control” needs to be immediately carried out, the catalyst bed temperatures of the NSR catalysts 17 L, 17 R and the DPNR catalysts 18 L, 18 R are estimated based on the output signals of the first exhaust gas temperature sensors 21 L, 21 R in step ST 11 . It is then determined whether the lowest value of the estimated bed temperature values reaches a temperature required for the sulfur release (which is, for example, approximately 350° C.). If such determination is positive, it is determined that the sulfur release should be carried out smoothly and step ST 13 is performed.
  • a temperature required for the sulfur release which is, for example, approximately 350° C.
  • step ST 11 If the determination of step ST 11 is negative, the combustion state of the engine 1 is switched (to a sulfur release combustion mode) in step ST 12 , so as to raise the catalyst bed temperatures. Step ST 13 is then carried out.
  • the air-fuel ratio (A/F) may be decreased by reducing the intake air amount by means of the throttle valve 9 .
  • the EGR amount may be increased or the fuel injection timings may be retarded.
  • step ST 13 it is determined whether the catalyst bed temperatures of the NSR catalysts 17 L, 17 R and the DPNR catalysts 18 L, 18 R, which are estimated based on the output signals of the first exhaust gas temperature sensors 21 L, 21 R, and the air-fuel ratio obtained from the output signals of the air-fuel ratio sensors 23 L, 23 R satisfy a rich spike condition (fuel addition condition), based on which the recovery from S poisoning is carried. out. If the determination of step ST 13 is positive, step ST 15 is performed. In step ST 13 , determination is performed using the lowest value of the estimated bed temperatures of the catalysts as the reference catalyst bed temperature. Further, the higher value of the air fuel-ratios of the first and second systems is employed as the air-fuel ratio in such determination.
  • step ST 13 If the determination of step ST 13 is negative, fuel addition (opening of the fuel adding valves 12 L, 12 R) is carried out in step ST 14 in order to adjust the catalyst bed temperatures. In this manner, the catalyst bed temperature is increased and the air-fuel ratio is enriched in such a manner as to satisfy the condition for carrying out the recovery from S poisoning. Step ST 15 is then performed.
  • the rich spike condition for permitting the recovery from S poisoning is, for example, that the catalyst bed temperature is 350° C. or greater and the air-fuel ratio has reached 22 .
  • a sulfur release amount is calculated.
  • the sulfur release amount is obtained with reference to a map defined in advance through tests and calculations using the catalyst bed temperatures and an S poisoning reduction speed as parameters.
  • the sulfur release amount is determined using an average value of the estimated catalyst bed temperature of the DPNR catalyst 18 L of the first system and the estimated catalyst bed temperature of the DPNR catalyst 18 R of the second system.
  • the requested fuel addition amount is determined based on the sulfur release amount obtained in step ST 15 . Based on the requested fuel addition amount, the energization duration (the fuel adding duration) of the fuel adding valves 12 L, 12 R, the requested number of multiple addition cycles, and the addition interval (see FIG. 4 ) are calculated.
  • step S 17 based on the energization duration, the requested number of multiple addition cycles, and the addition interval, which are calculated in step ST 16 , operation of the fuel adding valve 12 L of the first system and operation of the fuel adding valve 12 R of the second system are controlled in accordance with a common procedure. That is, the fuel is intermittently added to the exhaust gas by the fuel adding valves 12 L, 12 R at constant time intervals.
  • the sulfur release is executed by performing the rich spike, in which the exhaust gas in the vicinity of the NOx storage reduction catalysts is temporarily held in a state in which the oxygen content is small and the content of unburned fuel component is great.
  • the sulfur release control is performed in the first system and the second system in accordance with the common procedure.
  • step ST 18 It is then determined whether a condition for ending the sulfur release control is satisfied in step ST 18 . Specifically, it is determined whether the amount of the fuel added since starting of the sulfur release control has reached the requested fuel addition amount. If the determination is positive, the rich spike is ended and the routine is also suspended.
  • the PM elimination control for example, is performed by priority.
  • the PM elimination combustion or the sulfur release combustion is carried out for both of the first and second systems in accordance with the common procedure. This reduces the number of recovery cycles compared to a case in which the PM elimination/sulfur release control is performed each time the catalyst control is requested for the catalyst of the first system or the second system. The fuel consumption is thus prevented from increasing due to the PM elimination/sulfur release.
  • the PM elimination is performed using the catalyst exhibiting the lower catalyst bed temperature (the greater PM deposit amount) of the DPNR catalysts 18 L, 18 R of the systems as the reference.
  • the PM is thus completely burned on both DPNR catalysts 18 L, 18 R, preventing incomplete burning of PM.
  • the sulfur release is performed using the average value of the catalyst bed temperatures of the multiple catalysts (the NSR catalysts 17 L, 17 R and the DPNR catalysts 18 L, 18 R) of the first and second systems as the reference, to suppress thermal deterioration of the catalysts and ensure effective release of sulfur. This minimizes the thermal deterioration of each catalyst and allows sufficient release of sulfur.
  • the PM elimination is performed using the catalyst exhibiting the lowest catalyst bed temperature as the reference.
  • the sulfur release is carried out using the average of the catalyst bed temperatures of the catalysts. In this manner, the fuel addition for the PM elimination/sulfur release is carried out in both systems in accordance with the common procedure. This further suppresses increase of the fuel consumption caused by the PM elimination/sulfur release.
  • the air-fuel ratio of exhaust gas is lean in most of the operating ranges.
  • the content of oxygen is great in the atmosphere around the NSR catalysts 17 L, 17 R and the DPNR catalysts 18 L, 18 R.
  • This causes the NOx storage reduction catalysts of the NSR catalysts 17 L, 17 R and the DPNR catalysts 18 L, 18 R to store NOx of the exhaust gas.
  • the oxygen content in the atmosphere around the catalysts hardly becomes small, the stored NOx cannot be reduced easily.
  • the NOx storage reduction performance of each NOx storage reduction catalyst thus easily reaches a saturated level.
  • fuel is supplied to the NOx storage reduction catalysts, including those of the DPNR catalysts, to adjust the air-fuel ratio of the exhaust gas.
  • the temperature in the atmosphere around each catalyst is raised or such atmosphere is switched to a reductive atmosphere.
  • a specific example will hereafter be explained with reference to the flowchart of FIG. 3 .
  • the NOx reduction control of FIG. 3 is performed by the ECU 100 .
  • the NOx reduction routine is carried out repeatedly at certain time intervals.
  • step ST 21 it is determined whether NOx reduction needs to be immediately carried out for the first system or the second system. If the determination is negative, the routine is suspended. If the determination of step ST 21 is positive, step ST 22 is performed.
  • Such determination is carried out by, for example, estimating the NOx storage amounts of the NSR catalysts 17 L, 17 R and the DPNR catalysts 18 L, 18 R of both systems. Specifically, if an estimated NOx storage amount exceeds a predetermined reference value (a threshold estimated amount), it is determined that the NOx reduction needs to be immediately performed.
  • a predetermined reference value a threshold estimated amount
  • a map is defined from the NOx storage amounts corresponding to the engine speed and the fuel injection amount, which are determined in advance through tests or the like. The NOx storage amounts are then estimated by integrating the NOx storage amount, which is obtained with reference to the map.
  • step ST 22 it is determined whether the system for which the NOx reduction needs to be immediately performed corresponds to “the first system”. If the determination is positive, step ST 23 is performed. If the determination of step ST 22 is negative, it is determined that the NOx reduction needs to be immediately carried out in “the second system”. In this case, step ST 31 follows.
  • a NOx reduction basic fuel addition amount is calculated based on the difference between the actual fuel-air ratio, which is obtained using the detection signal of the air-fuel ratio sensor 23 L of the first system, and a target air-fuel ratio.
  • the NOx reduction basic fuel addition amount is then multiplied by a bed temperature correction coefficient to obtain a NOx reduction fuel addition amount, with which the NOx reduction control is performed.
  • the bed temperature correction coefficient is determined with reference to the bed temperature correction coefficient map shown in FIG. 5 , using the lower value of the catalyst bed temperatures of the NSR catalysts 17 L and the DPNR catalyst 18 L, which are estimated from the detection signal of the first exhaust gas temperature sensor 21 L of the first system.
  • the bed temperature correction coefficient is set to “zero”.
  • step ST 24 the energization duration (the fuel adding duration) of the fuel adding valve 12 L of the first system, the requested number of multiple addition cycles, and the addition interval (see FIG. 4 ) are calculated based on the NOx reduction fuel addition amount obtained in step ST 23 .
  • step ST 25 operation of the fuel adding valve 12 L of the first system is controlled in accordance with the energization duration, the requested number of the multiple addition cycles, and the addition interval, which have been determined in step ST 24 . In this manner, fuel is intermittently added to the exhaust gas by the fuel adding valve 12 L at certain time intervals.
  • the NOx reduction is thus performed by performing the rich spike, in which the atmosphere around each NOx storage reduction catalyst is temporarily held in a state in which the oxygen content is small and the content of unburned fuel component is great. Then, in step ST 26 , it is determined whether a condition for ending the NOx reduction control is satisfied. Specifically, it is determined whether the amount of the fuel added since starting of the NOx reduction control reaches the NOx reduction fuel addition amount. If the determination is positive, the rich spike is ended and the routine is suspended.
  • step ST 31 is performed. That is, the NOx reduction basic fuel addition amount is calculated using the difference between the actual air-fuel ratio, which is obtained from the detection signal of the air-fuel ratio sensor 23 R of the second system, and the target air-fuel ratio. The determined NOx reduction basic fuel addition amount is then multiplied by the bed temperature correction coefficient to obtain the NOx reduction fuel addition amount.
  • the bed temperature correction coefficient is determined with reference to the bed temperature correction coefficient map of FIG. 5 , as in the above-described case.
  • step ST 33 based on the energization duration, the requested number of multiple addition cycles, and the addition interval, which are determined in step ST 32 , operation of the fuel adding valve 12 R of the second system is controlled. In this manner, the fuel is intermittently added to the exhaust gas by the fuel adding valve 12 R at certain time intervals.
  • the NOx reduction is thus carried out by performing the rich spike, in which the atmosphere around each NOx storage reduction catalyst is temporarily held in a state in which the oxygen content is small and the content of the unburned fuel component is great. Then, in step ST 33 , it is determined whether a condition for ending the NOx reduction control is satisfied. Specifically, it is determined whether the amount of the fuel added since starting of the NOx reduction control reaches the NOx reduction fuel addition amount. If positive determination is made, the rich spike is ended and the routine is suspended.
  • the NOx reduction may be carried out for one of the first system or the second system by priority over the other or for both in parallel. Further, if the PM elimination or the sulfur release needs to be immediately performed at the same time as the NOx reduction control, the PM elimination control or the sulfur release control, for example, is carried out by priority.
  • the present invention is employed in the V type eight cylinders diesel engine having two exhaust systems.
  • the invention is not restricted to this use but may be employed in a diesel engine having any number of cylinders and three or more exhaust systems, such as a diesel engine having a total of four exhaust systems in which two exhaust passages 201 L, 202 L are provided in the left bank 2 L and two exhaust passages 201 R, 202 R are defined in the right bank 2 R as is illustrated in FIG. 6 .
  • the invention may be used in an engine other than the V type, for example, in a horizontal opposed type or a straight type.
  • the diesel engine in which the invention is used does not necessarily have to be an in-cylinder direct injection type but may be other types of diesel engines.
  • the NSR catalysts 17 L, 17 R and the DPNR catalysts 18 L, 18 R are arranged in the corresponding exhaust systems.
  • an exhaust gas purifying apparatus may be formed by providing an NSR catalyst or an oxidation catalyst and a DPF in each of the exhaust systems.

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EP1947306A1 (en) 2008-07-23
JP4657074B2 (ja) 2011-03-23
JP2007107415A (ja) 2007-04-26

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