CN1981117A - 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
CN1981117A
CN1981117A CNA2005800224726A CN200580022472A CN1981117A CN 1981117 A CN1981117 A CN 1981117A CN A2005800224726 A CNA2005800224726 A CN A2005800224726A CN 200580022472 A CN200580022472 A CN 200580022472A CN 1981117 A CN1981117 A CN 1981117A
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catalyzer
temperature
particulate filter
exhaust
nox
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CN100445524C (en
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吉田耕平
林孝太郎
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Toyota Motor Corp
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Toyota Motor Corp
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/021Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/027Introducing 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
    • F02D41/029Introducing 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
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation 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
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/92Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation 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
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/92Chemical or biological purification of waste gases of engine exhaust gases
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation 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
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/92Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404Removing only nitrogen compounds
    • B01D53/9409Nitrogen oxides
    • B01D53/9413Processes characterised by a specific catalyst
    • B01D53/9422Processes 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)
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation 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
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/96Regeneration, reactivation or recycling of reactants
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0821Exhaust 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
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0871Regulation of absorbents or adsorbents, e.g. purging
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0871Regulation of absorbents or adsorbents, e.g. purging
    • F01N3/0885Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10Exhaust 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
    • F01N3/18Exhaust 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
    • F01N3/20Exhaust 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
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/021Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/027Introducing 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
    • F02D41/0275Introducing 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
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2255/00Catalysts
    • B01D2255/10Noble metals or compounds thereof
    • B01D2255/102Platinum group metals
    • B01D2255/1025Rhodium
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2255/00Catalysts
    • B01D2255/90Physical characteristics of catalysts
    • B01D2255/91NOx-storage component incorporated in the catalyst
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00Adding substances to exhaust gases
    • F01N2610/03Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/14Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories in relation to the exhaust system
    • F02M26/15Arrangement 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
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00Road transport of goods or passengers
    • Y02T10/10Internal combustion engine [ICE] based vehicles
    • Y02T10/12Improving ICE efficiencies

Abstract

It is an object of the invention to provide a technology for appropriately recovering a decreased HC oxidizing ability of rhodium (Rh), in an exhaust gas control apparatus including a catalyst that contains rhodium (Rh) and a particulate filter (5). In this exhaust gas control apparatus, rich-spike control is prohibited and a NOx storage reduction catalyst is placed in a reduction atmosphere during a period in which a temperature of the NOx storage reduction catalyst is equal to or higher than a predetermined temperature, in a course of decreasing the temperature of the NOx storage reduction catalyst after a PM trapping ability forcible recovery process of the particulate filter (5) is completed. Thus, the decreased HC oxidizing ability of rhodium (Rh) is recovered.

Description

The controlling method and the control gear that are used for exhaust control device
Technical field
The present invention relates to a kind of controlling method and control gear that is used for exhaust control device, described exhaust control device comprises catalyzer and particle (particulate, particulate) filter that contains rhodium (Rh).
Background technique
In being used for being installed in the exhaust control device of the internal-combustion engine of vehicle for example, the catalyzer that contains platinum (Pt) is deterioration along with use.In order to address this problem, known a kind of method wherein when catalyst degradation, places dense atmosphere scheduled time slot with catalyzer, and the catalyst regeneration of deterioration (is restored, recover).For example be disclosed among the Japanese utility model application gazette No.63-128221 about the technology of this method.
As the exhaust control device of compression ignition internal combustion engine (being diesel engine), known a kind of by will containing rhodium (Rh) catalyzer and the particulate filter that is used for trap particulate matter (hereinafter being called " PM ") be arranged on the exhaust control device that vent systems forms integratedly or discretely.
In this exhaust control device, when the PM of particulate filter trapping ability was regenerated, catalyst exposure was in high temperature and rare atmosphere.If the catalyst exposure that contains rhodium (Rh) is in high temperature and rare atmosphere, then rhodium (Rh) moves to the inside of catalyst carrier, causes the NOx reducing capacity of catalyzer to descend.
When catalyzer is exposed in the dense atmosphere under 400 ℃ or higher high temperature, the NOx reducing capacity regeneration of this decline of catalyzer.Yet, there is such problem, promptly the temperature owing to the exhaust that discharges from compression ignition internal combustion engine is very low, so the temperature of catalyzer is elevated to 400 ℃ or higher meeting reduction fuel efficiency.
Summary of the invention
In view of the foregoing make the present invention.Therefore, the controlling method and the control gear that the purpose of this invention is to provide a kind of reducing capacity regeneration of the decline that can suitably make catalyzer at the exhaust control device that is used for internal-combustion engine, described exhaust control device by will containing rhodium (Rh) catalyzer and a particulate filter be arranged on described internal-combustion engine integratedly or discretely vent systems in form.
According to an aspect of the present invention, a kind of controlling method that is used for exhaust control device is provided, described exhaust control device by will containing rhodium (Rh) catalyzer and a particulate filter be arranged on internal-combustion engine integratedly or discretely vent systems in form, described controlling method is characterised in that: after the PM of described particulate filter trapping ability forcible recovery process is finished, in the process that reduces catalyst temperature described catalyzer is placed reducing atmosphere.
In order to make the PM trapping ability regeneration of particulate filter, the raise temperature of particulate filter of the amount that the temperature by forcing the rising exhaust and/or force increases reaction heat in the catalyzer.Like this, carry out so-called PM trapping ability forcible recovery process, so that oxidation and remove the PM that is captured in the particulate filter.
When carrying out PM trapping ability forcible recovery process, catalyzer and particulate filter are exposed in high temperature and the rare atmosphere together.Therefore, rhodium (Rh) moves to the inside of catalyst carrier.If rhodium (Rh) moves to the inside of catalyst carrier, then the reducing capacity of catalyzer descends.
When catalyzer at high temperature was exposed in the reducing atmosphere, the rhodium (Rh) that moves to catalyst carrier inside was exposed to the surface of catalyst carrier.
Should be pointed out that if the temperature of forcing the rising catalyzer for the reducing capacity regeneration of the decline that makes catalyzer just, then fuel efficiency can significantly reduce.
In order to solve such problem, after finishing, PM trapping ability forcible recovery process reduces in the process of catalyst temperature, and fully descending and need not to carry out in period of heating again of catalyzer in the temperature of catalyzer places reducing atmosphere with catalyzer.Like this, the reducing capacity of the decline of catalyzer can be regenerated by use the heat that obtains during PM trapping ability forcible recovery process.As a result, need not to carry out the extra hyperthermic treatment of the reducing capacity regeneration of the decline that is used to make catalyzer, suppressed the reduction of fuel efficiency.
When catalyzer was exposed in the reducing atmosphere under about 400 ℃ or higher high temperature, the reducing capacity of the decline of catalyzer was suitably regenerated.Therefore, after PM trapping ability forcible recovery process is finished, reduce in the process of catalyst temperature, in catalyst temperature is approximately 400 ℃ or higher period, catalyzer can be placed reducing atmosphere.In this case, the amount that produces the required reducing agent of reducing atmosphere can reduce to minimum.
In the present invention, can use NOx storage type reducing catalyst as the catalyzer that contains rhodium (Rh).Because the NOx storage capacity of NOx storage type reducing catalyst is restricted, so in the exhaust control device that comprises NOx storage type reducing catalyst, need to make the regeneration of NOx storage capacity where necessary.
As the method for the NOx storage capacity regeneration that is used to make NOx storage type reducing catalyst, so-called dense peak control (rich-spike control) is effective.In the control of dense peak, by supplying the air-fuel ratio that reducing agent makes the exhaust of inflow catalyst to exhaust in the catalyzer upstream flow.
In the exhaust control device that comprises particulate filter and NOx storage type reducing catalyst, can after finishing, the PM of particulate filter trapping ability forcible recovery process carry out the control of dense peak.
If carry out the control of dense peak when the NOx of catalyzer reducing capacity has descended, although the NOx that then is stored in the NOx storage type reducing catalyst is released, the NOx that discharges can not fully be reduced.Therefore, NOx is not discharged in the air with can being reduced.In addition, along with the increase of the amount of the NOx that is not reduced, the amount with the reducing agent of NOx reaction can not increase.
Simultaneously, if carry out the control of dense peak after PM trapping ability forcible recovery process is finished, then catalyst exposure is in high temperature and dense atmosphere.Therefore, can make the NOx reducing capacity regeneration of the decline of catalyzer.Yet in the control of dense peak, the air fuel ratio of exhaust thickens intermittently, and the length of the dense day part of the air fuel ratio of exhaust is shorter.Therefore, the very difficult NOx reducing capacity regeneration that fully makes the decline of catalyzer.Do not consider the characteristic of rhodium (Rh) when controlling in addition, at the dense peak of carrying out traditional type.Therefore, catalyzer does not always place dense atmosphere when the temperature of catalyzer is in suitable temperature range.
According to the present invention, be NOx storage type reducing catalyst if contain the catalyzer of rhodium (Rh), then the control of dense peak can be under an embargo after PM trapping ability forcible recovery process is finished, and catalyzer is placed in the reducing atmosphere thus.
When catalyzer places reducing atmosphere,, preferably make the air fuel ratio of exhaust be higher than air fuel ratio when dense atmosphere is produced by the control of dense peak owing to following reason.
If form when the NOx of catalyzer reducing capacity descends and the similar dense atmosphere of dense atmosphere that is produced by the control of dense peak, then the NOx of more amount is released from NOx storage type reducing catalyst, and the amount that therefore is not discharged into airborne NOx can increase with being reduced.
Be used for placing the example of the method for reducing atmosphere to comprise catalyzer a spot of reducing agent is supplied to the method for exhaust to control the short-and-medium time lag than dense peak, and the method that makes the air fuel ratio step-down in the internal-combustion engine.
In the exhaust control device that comprises NOx storage type reducing catalyst and particulate filter, after PM trapping ability forcible recovery process, can carry out and be used to make of the processing (hereinafter be called " the sulfur poisoning Regeneration Treatment of NOx storage type reducing catalyst ") of NOx storage type reducing catalyst from sulfur poisoning regeneration.
Be different from the sulfur poisoning Regeneration Treatment according to of the present invention being controlled on following this aspect.In control according to the present invention, catalyzer placed reducing atmosphere and the temperature of catalyzer and do not force to keep the temperature of catalyzer of not forcing to raise.In contrast, in the sulfur poisoning Regeneration Treatment, place reducing atmosphere to force simultaneously to raise catalyzer and keep the temperature of catalyzer.
If carry out the sulfur poisoning Regeneration Treatment, then catalyst exposure is in high temperature and dense atmosphere.Therefore can make the NOx reducing capacity regeneration of the decline of catalyzer.
Therefore, when after PM trapping ability forcible recovery process, carrying out the sulfur poisoning Regeneration Treatment, forbid according to control of the present invention.On the other hand, when after PM trapping ability forcible recovery process, not carrying out the sulfur poisoning Regeneration Treatment, carry out according to control of the present invention.In this case, prevented that catalyzer from unnecessarily being placed reducing atmosphere, therefore prevented the reduction of fuel efficiency.
According to a further aspect in the invention, a kind of control gear that is used for exhaust control device is provided, described exhaust control device comprises the particulate filter in the vent systems that is located at internal-combustion engine, and be arranged in the described vent systems integratedly or discretely with described particulate filter and contain the catalyzer of rhodium, described control gear is characterised in that and comprises: thus the temperature of the temperature of the described particulate filter that is used to raise and described catalyzer makes the reclaimer of the PM trapping ability forced regeneration of described particulate filter; And the process that is used for the temperature of the described catalyzer of reduction after the PM of described particulate filter trapping ability is forced to regenerate places described catalyzer the NOx reducing capacity reclaimer of reducing atmosphere.
Should be appreciated that " storage " used herein is meant with at least a form maintenance material (solid, liquid, gas molecule) in absorption, adhesion, absorption, capture, occlusion (occlusion) and other form.
Description of drawings
The detailed description of below reading in conjunction with the drawings exemplary embodiment of the present invention being carried out can be understood the above embodiment of the present invention and other embodiment, purpose, feature, advantage, technology and industrial significance better, in the accompanying drawings:
Fig. 1 is the schematically illustrated view of having used the structure of internal-combustion engine of the present invention;
Fig. 2 is the figure that the temperature of the NOx reducing capacity that activates NOx storage type reducing catalyst is shown;
Fig. 3 is the flow chart of program that the NOx reducing capacity regeneration control of catalyzer is shown;
Fig. 4 illustrates the figure that is used to carry out a kind of concrete grammar that the exhaust enriching handles.
Embodiment
In the following description, will the present invention will be described in more detail in conjunction with exemplary embodiment.
Internal-combustion engine 1 shown in Figure 1 is compression ignition internal combustion engine (being diesel engine).This internal-combustion engine 1 is provided with inlet air pathway 2 and exhaust passageway 3.In inlet air pathway 2, be provided with air inlet shutter 4.In exhaust passageway 3, be provided with particulate filter 5.This particulate filter was held the NOx storage type reducing catalyst that contains rhodium (Rh) in 5 years.
In exhaust passageway 3, be provided with from the reducing agent supply valve 6 of internal-combustion engine 1 burner oil in a certain position of particulate filter 5 upstreams as reducing agent.A certain position in particulate filter 5 downstreams is provided with exhaust gas temperature sensor 7 in exhaust passageway 3.
EGR path 8 allows to be communicated with between inlet air pathway 2 and exhaust passageway 3.In EGR path 8, be provided with EGR valve 9.
In air inlet shutter 4, reducing agent supply valve 6, exhaust gas temperature sensor 7 and the EGR valve 9 each all is electrically connected to ECU 10.
ECU 10 carries out known control based on the working state of exhaust gas temperature sensor 7 and internal-combustion engine 1, for example fuel injection control and EGR control.ECU 10 also carries out the NOx reducing capacity regeneration control as the catalyzer of major character of the present invention.To the NOx reducing capacity regeneration control of catalyzer be elaborated hereinafter.
Because the PM trapping ability of particulate filter 5 is restricted, so ECU 10 carried out PM trapping ability forcible recovery process before the limit that reaches the PM trapping ability.In PM trapping ability forcible recovery process, ECU 10 is by carrying out the back and spray and/or from the temperature of reducing agent supply valve 6 fuel supplying and rising exhaust to exhaust and/or increase the amount of the reaction heat in the NOx storage type reducing catalyst, the temperature of forcing rising particulate filter 5 thus.
When carrying out the PM trapping ability forcible recovery process of particulate filter 5, the NOx storage type reducing catalyst of being held in 5 years by particulate filter also is exposed in high temperature and the dense atmosphere.At this moment, be included in the inside that rhodium (Rh) in the NOx storage type reducing catalyst moves to catalyst carrier.As a result, the NOx reducing capacity of NOx storage type reducing catalyst (especially hydrocarbon (HC) oxidability) descends.
If the HC oxidability of NOx storage type reducing catalyst descends, then the NOx reducing capacity of NOx storage type reducing catalyst descends.That is to say, if the HC oxidability of NOx storage type reducing catalyst descends, then when the NOx storage capacity of NOx storage type reducing catalyst is regenerated, promptly when carrying out fuel (hydrocarbon (HC)) intermittently from the control of reducing agent supply valve 6 is supplied dense peak to exhaust, hydrocarbon (HC) converts the reaction activating substance to and becomes very difficult in NOx storage type reducing catalyst.Therefore, the NOx that discharges from NOx storage type reducing catalyst is not discharged into the air with will being reduced, and is supplied to the hydrocarbon of NOx storage type reducing catalyst not to be discharged in the air with NOx with reacting.
Fig. 2 is the figure that the temperature of the NOx reducing capacity that activates NOx storage type reducing catalyst is shown.Before the PM trapping ability forcible recovery process of carrying out particulate filter 5, the NOx reducing capacity of NOx storage type reducing catalyst is activated under about 300 ℃ temperature.In contrast, after carrying out the PM trapping ability forcible recovery process of particulate filter 5, the NOx reducing capacity of NOx storage type reducing catalyst is not activated always and is elevated to about 350 ℃ or higher up to temperature.
The temperature of the exhaust that discharges from compression ignition internal combustion engine is about 300 ℃ constantly removing internal-combustion engine other the period of working under the high load.As mentioned above, the rising of the temperature that is activated of NOx reducing capacity has increased the possibility that the amount that is discharged into airborne NOx and HC when carrying out the control of dense peak increases.
Therefore, when carrying out PM trapping ability forcible recovery process, need make the HC oxidability regeneration of the decline of NOx storage type reducing catalyst.In order to make the HC oxidability regeneration of decline, the rhodium (Rh) that has been moved to catalyst carrier inside need be exposed to the surface of catalyst carrier once more.
When catalyzer was exposed in the reducing atmosphere under 400 ℃ or higher high temperature, the rhodium (Rh) that has been moved to catalyst carrier inside was exposed to the surface of catalyst carrier.Therefore, if the temperature of NOx storage type reducing catalyst be elevated to 400 ℃ or higher after the exhaust that flows into NOx storage type reducing catalyst is thickened, then the HC oxidability of Xia Jianging is renewable.
Be used for the temperature of NOx storage type reducing catalyst is elevated to 400 ℃ or higher, promptly the example of the effective ways of the temperature in the high-temperature scope comprises the method for elevated exhaust temperature by carrying out the back injection, and the method that increases the amount of the reaction heat in the NOx storage type reducing catalyst by fuel supplying in exhaust.Yet these methods exist a common problem, the i.e. reduction of fuel efficiency.
Therefore, in NOx reducing capacity regeneration control according to the catalyzer of present embodiment, after PM trapping ability forcible recovery process is finished, reduce in the process of temperature of NOx storage type reducing catalyst, in catalyst temperature is 400 ℃ or higher period, particulate filter 5 is placed reducing atmosphere (dense atmosphere).
Below with reference to Fig. 3 explanation is carried out in the NOx reducing capacity regeneration control of catalyzer.Fig. 3 is the flow chart of program that the NOx reducing capacity regeneration control of catalyzer is shown.The NOx reducing capacity regeneration control program of catalyzer is stored among the ROM of ECU 10 in advance.The NOx reducing capacity regeneration control program of catalyzer is the interrupt routine of being carried out by ECU 10 after PM trapping ability forcible recovery process is finished.
In the NOx of catalyzer reducing capacity regeneration control program, ECU 10 determines in step S101 at first that PM trapping ability forced regeneration is finished and marks whether to be shown as " 1 ".PM trapping ability forced regeneration is finished mark and is stored in advance among RAM etc.When PM trapping ability forcible recovery process is finished, storage " 1 ".When the NOx of catalyzer reducing capacity regeneration control is finished, storage " 0 ".
When determining that in step S101 PM trapping ability forced regeneration is finished mark and is shown as " 0 ", ECU 10 termination routines.On the other hand, when determining that in step S101 PM trapping ability forced regeneration is finished mark and is shown as " 1 ", ECU 10 is execution in step S102 subsequently.
In step S102, ECU 10 receives the signal Tout (hereinafter be called " go out flow delivery temperature Tout ") of indication from the temperature of the exhaust of particulate filter 5 releases, and this signal Tout is from exhaust gas temperature sensor 7 outputs.
In step S103, ECU 10 determines to receive in step S102 goes out to flow delivery temperature Tout and whether is equal to or higher than predetermined temperature Ts (for example 400 ℃).
Be not higher than predetermined temperature (during Tout<Ts), the bed temperature that ECU infers NOx storage type reducing catalyst is lower than predetermined temperature Ts, then execution in step S110 when in step S103, determining stream delivery temperature Tout.In step S110, the value that ECU 10 finishes mark with PM trapping ability forced regeneration changes to " 0 ", termination routine then.
On the other hand, be equal to or higher than predetermined temperature (during Tout 〉=Ts), the bed temperature that ECU 10 infers NOx storage type reducing catalyst is equal to or higher than predetermined temperature Ts, then execution in step S104 when in step S103, determining stream delivery temperature Tout.
In step S104, ECU 10 forbids the control of dense peak.
In step S105, ECU 10 carries out the exhaust enriching that is used to make the exhaust that flows into particulate filter 5 to thicken and handles.In the exhaust enriching was handled, ECU 10 control reducing agent supply valves 6 made fuel be fed in the exhaust intermittently.
At this moment, ECU 10 controls reducing agent supply valves 6, make that the quantitative change from reducing agent supply valve 6 supplied fuel must be littler than the amount the control of dense peak during each supply, and the interval between the supply of fuel becomes than the interval weak point in the control of dense peak, as shown in Figure 4.
Making from the amount of reducing agent supply valve 6 supplied fuel during each supply is owing to following reason than the amount the control of dense peak for a short time.If when the HC oxidability of NOx storage type reducing catalyst has descended, be supplied to NOx storage type reducing catalyst with the hydrocarbon (HC) of same amount in the control of dense peak, then the amount of the NOx that discharges from NOx storage type reducing catalyst increases, and the amount that is not discharged into airborne NOx also increases with being reduced.
During each supply, make from the amount of reducing agent supply valve 6 supplied fuel littler also owing to following reason than the amount the control of dense peak.If when the HC oxidability of NOx storage type reducing catalyst has descended, be supplied to NOx storage type reducing catalyst with the hydrocarbon (HC) of same amount in the control of dense peak, then the amount that is not discharged into airborne hydrocarbon (HC) with NOx can increase with reacting.
Making the interval between the supply of fuel is owing to following reason than the interval weak point in the control of dense peak.After PM trapping ability forcible recovery process was finished, the temperature of particulate filter 5 and NOx storage type reducing catalyst reduced rapidly.Therefore, if with identical distance fuel supplying in controlling with dense peak, then the temperature of NOx storage type reducing catalyst can be reduced to predetermined temperature Ts or lower temperature before the regeneration of HC oxidability.
In step S106, ECU 10 receives once more from signal (promptly going out the to flow delivery temperature) Tout of exhaust gas temperature sensor 7 outputs.
In step S107, whether ECU 10 determines to receive in step S106 goes out to flow delivery temperature Tout and has been reduced to and is lower than predetermined temperature Ts.
Also be not reduced to and be lower than predetermined temperature Ts (during Tout 〉=Ts) when in step S107, determining stream delivery temperature Tout, ECU 10 determines that the bed temperature of NOx storage type reducing catalyst still is equal to or higher than predetermined temperature Ts, and then execution in step S105 and step subsequently.
On the other hand, be reduced to and be lower than predetermined temperature Ts (during Tout<Ts), ECU 10 determines that the bed temperature of NOx storage type reducing catalysts has been reduced to and be lower than predetermined temperature Ts, then execution in step S108 when in step S107, determining stream delivery temperature Tout.
In step S108, ECU 10 finishes the exhaust enriching to be handled.
In step S109, ECU 10 eliminates forbidding dense peak control.
In step S110, the value that ECU 10 finishes mark with PM trapping ability forced regeneration changes to " 0 ".
When ECU 10 carries out the NOx reducing capacity regeneration control program of catalyzer in the above described manner, can make the HC oxidability regeneration of NOx storage type reducing catalyst by using the heat that during PM trapping ability forcible recovery process, obtains.As a result, can suppress owing to the raise reduction of the fuel efficiency that causes of the temperature of NOx storage type reducing catalyst.
In the present embodiment, make the amount that during each supply, is fed to the fuel in the exhaust littler than the amount in the control of dense peak.And, in the present embodiment, make the interval between the supply of fuel shorter than the interval in the control of dense peak.Therefore, in being equal to or higher than period of predetermined temperature Ts, the bed temperature of NOx storage type reducing catalyst can make the HC oxidability regeneration of NOx storage type reducing catalyst.In addition, can reduce amount that is not discharged into airborne NOx and the amount that is not discharged into airborne hydrocarbon (HC) with NOx with being reduced with reacting.
If carrying out the exhaust enriching after PM trapping ability forcible recovery process is finished handles, then owing to the heat that reaction produced by rhodium (Rh) and hydrocarbon (HC), the bed temperature of NOx storage type reducing catalyst can maintain the temperature that is equal to or higher than predetermined temperature Ts for a long time.In this case, can adopt in the following method any one: (1) became and equals or when being longer than the scheduled time, the exhaust enriching is finished dealing with when the time of implementation that the exhaust enriching is handled; (2) by when increasing the supply of fuel number of times, reducing fuel duty the temperature of NOx storage type reducing catalyst is reduced gradually; And (3) in each supply of fuel executed be provided with one behind the pre-determined number at interval, make the temperature of NOx storage type reducing catalyst reduce in stepped mode.
In the present embodiment, adopt a kind of concrete grammar that is used to carry out the processing of exhaust enriching from reducing agent supply valve 6 fuel supplying conduct to exhaust.Yet, can reduce from the air fuel ratio of the exhaust of internal-combustion engine 1 release by the amount that increases EGR gas.
In the present embodiment, particulate filter 5 and NOx storage type reducing catalyst are arranged in the exhaust passageway 3 integratedly.Yet particulate filter 5 and NOx storage type reducing catalyst also are arranged in the exhaust passageway 3 separably.
For example, particulate filter 5 and NOx storage type reducing catalyst can in series be arranged on (preferably, NOx storage type reducing catalyst is arranged on the upstream of particulate filter 5) in the exhaust passageway 3.Should be noted that in this case reducing agent supply valve 6 need be arranged on the upstream of NOx storage type reducing catalyst.
Below other embodiment is described.
When the amount of the sulphur in being included in internal-combustion engine 1 employed fuel was very high, sulfur poisoning (being that S poisons) took place in NOx storage type reducing catalyst.Therefore, after PM trapping ability forcible recovery process, can carry out the sulfur poisoning Regeneration Treatment.
In the sulfur poisoning Regeneration Treatment, catalyzer is placed in the dense atmosphere, and the temperature maintenance of NOx storage type reducing catalyst is at high temperature simultaneously.Therefore, can make the HC oxidability regeneration of the decline of NOx storage type reducing catalyst.
Therefore, when carrying out the sulfur poisoning Regeneration Treatment after PM trapping ability forcible recovery process, ECU 10 forbids the NOx reducing capacity regeneration control of catalyzer.On the other hand, when not carrying out the sulfur poisoning Regeneration Treatment after PM trapping ability forcible recovery process, ECU 10 carries out the NOx reducing capacity regeneration control of catalyzer.
In this case, the NOx reducing capacity regeneration control that has prevented catalyzer is unnecessarily carried out.Therefore, can suppress owing to the fuel consumption that causes is controlled in the NOx reducing capacity regeneration of catalyzer.

Claims (6)

1. controlling method that is used for exhaust control device, described exhaust control device forms by catalyzer that will contain rhodium and the vent systems that the particulate filter (5) that is used for trap particulate matter is arranged on internal-combustion engine integratedly or discretely, and described controlling method is characterised in that:
The temperature by the described particulate filter (5) that raises and the temperature of described catalyzer are carried out the particulate matter trapping ability forcible recovery process of the particulate matter trapping ability forced regeneration that is used to make described particulate filter (5); And
After finishing, described particulate matter trapping ability forcible recovery process in the process of the temperature that reduces described catalyzer, described catalyzer is placed reducing atmosphere.
2. the controlling method that is used for exhaust control device according to claim 1, wherein:
In the temperature of described catalyzer is equal to or higher than period of predetermined temperature, described catalyzer is placed reducing atmosphere.
3. the controlling method that is used for exhaust control device according to claim 2, wherein:
Described predetermined temperature is approximately 400 ℃.
4. according to each described controlling method that is used for exhaust control device in the claim 1 to 3, wherein:
Described catalyzer is a NOx storage type reducing catalyst; And
When described catalyzer is placed in the described reducing atmosphere, forbid being used to making the execution of processing of the NOx storage and reduction ability regeneration of described catalyzer.
5. the controlling method that is used for exhaust control device according to claim 4, wherein:
Make the air fuel ratio of exhaust when described catalyzer is placed in the described reducing atmosphere be higher than the air fuel ratio of exhaust during the processing of the described NOx storage and reduction ability regeneration that is used to make described catalyzer.
6. control gear that is used for exhaust control device, described exhaust control device comprises the particulate filter (5) in the vent systems that is located at internal-combustion engine, and be arranged in the described vent systems integratedly or discretely with described particulate filter (5) and contain the catalyzer of rhodium, described control gear is characterised in that and comprises:
The temperature that is used for temperature by the described particulate filter (5) that raises and described catalyzer makes the reclaimer (10) of the particulate matter trapping ability forced regeneration of described particulate filter (5); And
Be used for after the particulate matter trapping ability of described particulate filter (5) is forced to regenerate, described catalyzer being placed the NOx reducing capacity reclaimer (10) of reducing atmosphere in the process of the temperature that reduces described catalyzer.
CNB2005800224726A 2004-07-05 2005-06-30 Control method and control device for exhaust gas control apparatus Expired - Fee Related CN100445524C (en)

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