CN102939442A - 废气净化系统 - Google Patents

废气净化系统 Download PDF

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CN102939442A
CN102939442A CN2011800288278A CN201180028827A CN102939442A CN 102939442 A CN102939442 A CN 102939442A CN 2011800288278 A CN2011800288278 A CN 2011800288278A CN 201180028827 A CN201180028827 A CN 201180028827A CN 102939442 A CN102939442 A CN 102939442A
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automatic regeneration
regeneration
exhaust gas
outlet pipe
waste gas
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CN102939442B (zh
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池田卓史
浅见彻也
佐藤等
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Isuzu Motors Ltd
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D46/00Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/66Regeneration of the filtering material or filter elements inside the filter
    • B01D46/80Chemical processes for the removal of the retained particles, e.g. by burning
    • B01D46/84Chemical processes for the removal of the retained particles, e.g. by burning by heating only
    • 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
    • F01N13/00Exhaust 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
    • F01N13/009Exhaust 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
    • F01N13/0097Exhaust 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
    • 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
    • F01N3/02Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021Exhaust 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
    • F01N3/023Exhaust 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
    • F01N3/0235Exhaust 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 exhaust gas throttling means
    • 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
    • F01N3/02Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021Exhaust 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
    • F01N3/023Exhaust 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
    • F01N3/025Exhaust 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
    • F01N3/0253Exhaust 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
    • 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
    • F01N3/02Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021Exhaust 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
    • F01N3/033Exhaust 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 in combination with other devices
    • F01N3/035Exhaust 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 in combination with other devices with catalytic reactors, e.g. catalysed diesel 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
    • F01N3/10Exhaust 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
    • F01N3/105General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/106Auxiliary oxidation catalysts
    • 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
    • F01N9/00Electrical control of exhaust gas treating apparatus
    • F01N9/002Electrical control of exhaust gas treating apparatus of filter regeneration, e.g. detection of clogging
    • 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
    • F02D41/04Introducing corrections for particular operating conditions
    • F02D41/08Introducing corrections for particular operating conditions for idling
    • 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
    • F01N2240/00Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/36Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being an exhaust flap
    • 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
    • F01N2610/14Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1453Sprayers or atomisers; Arrangement thereof in the exhaust apparatus
    • F01N2610/146Control thereof, e.g. control of injectors or injection valves
    • 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
    • F01N2900/00Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06Parameters used for exhaust control or diagnosing
    • F01N2900/10Parameters used for exhaust control or diagnosing said parameters being related to the vehicle or its components
    • 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
    • F01N2900/00Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06Parameters used for exhaust control or diagnosing
    • F01N2900/14Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
    • F01N2900/1404Exhaust gas temperature
    • 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
    • F01N2900/00Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06Parameters used for exhaust control or diagnosing
    • F01N2900/16Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
    • F01N2900/1602Temperature of exhaust gas apparatus
    • 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
    • F02D41/14Introducing closed-loop corrections
    • F02D41/1401Introducing closed-loop corrections characterised by the control or regulation method
    • F02D2041/1409Introducing closed-loop corrections characterised by the control or regulation method using at least a proportional, integral or derivative controller
    • 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
    • F02D41/024Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus
    • F02D41/025Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus by changing the composition of the exhaust gas, e.g. for exothermic reaction on exhaust gas treating apparatus
    • 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
    • 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
    • F02D41/14Introducing closed-loop corrections
    • F02D41/1438Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1446Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being exhaust temperatures
    • 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
    • F02D41/14Introducing closed-loop corrections
    • F02D41/1438Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1477Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation circuit or part of it,(e.g. comparator, PI regulator, output)
    • F02D41/1482Integrator, i.e. variable slope
    • 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
    • Y02T10/40Engine management systems

Abstract

提供一种废气净化系统,能够正确地进行从行驶自动再生到停止时的自动怠速再生的控制,并且,即使从自动怠速再生转移到行驶自动再生,废气温度也不会产生过冲。柴油发动机(10)的排气管(20)与捕集废气中的PM的DPD(25)连接,在所述DPD(25)的PM量成为一定量以上时,进行排气管喷射而使柴油发动机(10)的废气温度上升,从而将DPD自动再生,其中,在检测自动再生时的DPD再生的废气温度,求出所检测到的废气温度与再生目标温度的偏差,并基于该偏差对排气管喷射量进行PID控制时,在从行驶自动再生转移到停车的怠速自动再生时,将PID控制中的积分控制项复位为零,来控制排气管喷射量。

Description

废气净化系统
技术领域
本发明涉及捕集柴油发动机的废气中的PM(Particulate Matter:微粒物质)并将NOx净化而排气的废气净化系统,特别涉及在将DPD自动再生时暂时停车而进行怠速自动再生时的废气净化系统。
背景技术
作为将柴油发动机的废气净化并排气的废气净化系统,开发了在排气管中连接有DPD(Diesel Particulate Defuser:柴油机微粒消除器)及SCR(Selective Catalytic Reductio:选择性催化还原)装置的废气净化系统。
在该废气净化系统中,利用DPD来捕集废气中的PM。此外,在废气净化系统中,通过具备SCR装置的SCR系统,将贮存在尿素箱中的尿素水向SCR的废气上游供给,利用废气的热生成氨气,通过该氨气,在SCR催化剂上将NOx还原而净化(例如参照专利文献1、2)。
由DPD捕集到的PM成为过滤器堵塞的原因,所以需要将捕集堆积的PM适当地氧化而除去,从而进行再生。
排气压传感器检测DPD前后的差压,在该差压达到上限值时,ECU(EngineControl Unit:发动机控制单元)自动进行该堵塞的检测,或者在手动进行的情况下,使设置在车舱内的DPD警告灯点灯,通过由驾驶员按下再生执行开关,开始DPD再生。
DPD包括:由将未燃烧燃料氧化的活性催化剂构成的DOC(DieselOxidation Catalyst:氧化催化剂);和捕集废气中的PM的CSF(CatalyzedSoot Filter:催化烟尘过滤器)。
在DPD再生时,在进行燃料的多级喷射(引燃喷射、预喷射、主喷射、延迟喷射)而使排气温度上升到了DOC的催化剂活性温度以上,追加后(post)喷射,使排气温度上升至500℃、600℃左右,利用该高温的废气使CSF所捕集到的PM燃烧而将其除去,从而进行再生。但是,进行后喷射时,在气筒的润滑油中混入燃料油,产生润滑油的稀释(dilution),因此,通过在DPD上游侧的排气管内喷射燃料(HC)、即所谓的排气管喷射来进行DPD再生。
在该排气管喷射中,也与后喷射同样,DPD再生分为在行驶中进行自动再生的情况和将车停止而以怠速旋转进行手动再生的情况。通常在行驶中进行自动再生,但是在为了进行行驶中的再生而使车反复进行加减速等时,废气温度不稳定,容易在DPD内产生PM的燃烧残留。因此,在再生间隔较短地反复进行DPD自动再生的情况下,警告驾驶员进行手动再生,在将车停止的状态下,按下手动再生执行开关,由此通过手动再生将DPD的PM除去。
此外,在行驶中的自动再生中,为了在车停止时在怠速旋转下也能够进行再生,将排气制动阀关闭来防止排气温度的降低,继续进行再生。
在该自动再生中,由设置在DOC的下游侧的排气温度传感器检测向CSF流入的废气温度,求出该废气温度与再生目标温度(作为一个例子为500℃、600℃)的偏差,基于该偏差对排气管喷射量进行PID控制,以成为再生目标温度。
在先技术文献
专利文献
专利文献1:日本特开2000-303826号公报
专利文献2:日本特许第4175281号公报
发明的概要
发明要解决的课题
然而,停车时的怠速自动再生通过降速至再生怠速转速并关闭排气制动阀,即使在转速较低且废气量较少的怠速下,也能够在实现DPD内的废气的保温的同时进行排气管喷射而自动再生。
然而,即使如上述那样关闭排气制动阀并进行排气管喷射,由于在DOC中流动的废气量较少,所以多数情况下再生温度达不到再生目标温度,并且排气管喷射的未燃燃料不断积存在DOC中。
一般而言,PID控制是将比例控制项(P项)、积分控制项(I项)、微分控制项(D项)组合而收敛为设定值的控制,并以如下方式进行控制:在比例控制项中,与偏差成正比地使操作量改变,在积分控制项中将偏差相加,并与该偏差值成正比地改变操作量,由此消除比例控制中的残存偏差(额定偏差),进而在微分控制项中将偏差的变化率变换为速度,并输出与其成正比的操作量,由此,加快响应速度而尽快收敛为设定值。
在此,在怠速自动再生时,如上述那样,再生温度达不到目标温度,因此若通过PID控制来控制排气管喷射,则在比例控制项中,基于该偏差输出恒定的操作量,并且在微分控制项中也没有偏差,因而输出恒定的操作量,在偏差不变化的状态下,在控制时也不会在怠速控制时出现障碍。但是,在积分控制项中,按照规定的积分时间将偏差相加,因此,若怠速控制变长,则积分控制项的操作量增大,上升至上限值。此外,行驶中和怠速时相比废气量较大地不同,因此需要各自采用最佳的积分控制项。
这样,在积分控制项上升至上限值而从怠速自动再生变为行驶自动再生的情况下,若将排气制动阀打开,则大量的废气从发动机流向废气管,并且,若同时以由到此为止的PID控制决定的操作量来进行排气管喷射,则大量的未燃燃料和废气流向DPD,而且积存于DOC的未燃燃料也燃烧,存在产生再生温度相对于目标温度过大的过冲(overshoot)的问题。此时,产生过大的过冲是怠速自动再生时间较长的情况,此外,在怠速停止时间较短的情况下,可以认为积分控制项的影响很小。
发明内容
因此,本发明的目的在于,解决上述课题,提供一种废气净化系统,能够正确地进行从行驶自动再生到停止时的自动怠速再生的控制,并且,即使从自动怠速再生转移到行驶自动再生,废气温度也不会产生过冲。
解决课题所采用的技术手段
为了实现上述目的,技术方案1的发明涉及废气净化系统,在柴油发动机的排气管中连接有捕集废气中的PM的DPD,在所述DPD的PM量成为一定量以上时,进行排气管喷射而使柴油发动机的废气温度上升,从而将DPD自动再生,该废气净化系统的特征在于,在检测自动再生时的DPD再生的废气温度,求出检测的废气温度与再生目标温度的偏差,并基于该偏差对排气管喷射量进行PID控制时,在从行驶自动再生转移到停车时的怠速自动再生时,将PID控制中的积分控制项复位为零,来控制排气管喷射量。
技术方案2的发明如技术方案1所述的废气净化系统,在从所述停车后的怠速自动再生开始起,在规定时间以内转移到行驶自动再生时,继续通过在所述怠速自动再生中将积分控制项复位为零后的PID控制,来控制排气管喷射量。
技术方案3的发明如技术方案1所述的废气净化系统,在从所述停车后的怠速自动再生开始起,超过规定时间后转移到行驶自动再生时,再次将PID控制的积分控制项复位为零。
技术方案4的发明如技术方案1所述的废气净化系统,在从行驶自动再生开始将车减速而停车时,在减速时继续通过PID控制进行排气管喷射,在停车后将PID控制的积分控制项复位为零。
技术方案5的发明如权利能要求1~3中任一项所述的废气净化系统,在开始怠速自动再生时,将排气制动阀关闭,在转移到行驶自动再生时,将排气制动阀打开。
发明的效果:
根据本发明,能够消除由怠速自动再生时的PID控制引起的弊端,发挥能够防止DPD内的废气过冲的良好效果。
附图说明
图1是表示本发明的一实施方式的整体结构图。
图2是表示本发明的自动再生时的控制图的图。
具体实施方式
以下,基于附图详细描述本发明优选的一实施方式。
在图1中,柴油发动机10的吸气岐管11和排气岐管12分别与增压机13的压缩机14和涡轮15连结,来自上游侧吸气管16a的空气被压缩机14升压,经过下游侧吸气管16b的中冷器17而被冷却后,经由吸气节流阀18从吸气岐管11被供给至柴油发动机10,来自柴油发动机10的废气对涡轮15进行驱动后,排气至排气管20。
上游侧吸气管16a中设有用于测定吸气量的空气流量传感器(MAF)19,通过该空气流量传感器(MAF),控制吸气节流阀18的开度,从而调整吸气量。此外,排气岐管12和吸气岐管11与EGR(Exhaust Gas Recirculation:排气再循环)管21连接,该EGR管21用于使废气的一部分返回至发动机10的吸气系统而减少NOx,该EGR管21与EGR冷却器22和EGR阀23连接。
排气管20与排气制动阀24、DPD25、排气节流阀26和消声器27连接。DPD25包括由将未燃烧燃料氧化的活性催化剂构成的DOC28、和捕集废气中的PM的CSF29。
在排气制动阀24的上游侧,为了在DPD再生时使废气温度升温,设有向排气管20喷射燃料(进行排气管喷射)的排气管喷射器39。向该排气管喷射器39供给来自未图示的燃料箱的燃料的燃料供给管路40,与用于将燃料中混入或产生的异物或水分除去的燃料过滤器41连接,在其下游侧设置有用于测定排气管喷射器39的燃料压力的燃料压力传感器42。
此外,虽未进行图示,但是在排气节流阀26和消声器27之间连接有用氨气将NOx脱硝的SCR装置。
在DOC28的前后设有废气温度传感器30a、30b,设有用于检测CSF29的PM堆积量的差压传感器31,这些传感器的检测值被输入至ECU(发动机控制单元)32。
ECU32被输入用于检测发动机的转速的旋转传感器33的检测值、车速传感器34的检测值。
ECU32在行驶中,根据加速器开度控制燃料喷射器38的燃料喷射量,并且适当地控制吸气节流阀18、排气制动阀24、排气节流阀26。
在该废气处理系统中,在ECU32通过用于检测CSF29的前后的差压的差压传感器31的检测值而判断为在DPD25中堆积了一定量PM时,或者在从上次的再生后起的行驶距离达到规定值时,使废气温度最终升温至600℃左右而使PM燃烧,进行再生。
该再生通过燃料喷射器38进行多级喷射(引燃喷射、预喷射、主喷射、延迟喷射),以成为DOC28的催化剂活性温度以上,然后由排气管喷射器39向排气管20内对燃料进行排气管喷射,使废气温度作为一例升温至500℃、600℃,从而使PM燃烧,通常在行驶中进行自动再生,在该期间,ECU32使自动再生灯36b进行再生中点灯。在自动再生中,若在行驶中反复进行加减速,则废气温度不稳定,DPD25中会产生PM的燃烧残留,在再生间隔变短时,将手动再生灯36a点灯而警告驾驶员进行手动再生,驾驶员在将车停止的状态下,按下手动再生执行开关37,由此能够通过手动再生来将DPD25再生。
另外,利用图2说明自动再生时的ECU32的控制图。
在自动再生时,ECU32将吸气节流阀18收束,进行多级喷射而使废气温度升温至催化剂活性温度以上,接着在多级喷射中加上由排气管喷射器39进行的排气管喷射,将废气温度作为一例升温至500℃、600℃而使PM燃烧,将DPD25再生。此外,由于再生是排气管喷射,因此EGR阀23维持通常控制。在再生结束后,使吸气节流阀18返回至通常控制。
在该自动再生中,在车辆由于等待信号等而处于停车时,使发动机旋转从通常怠速旋转开始,在变速器的齿轮为空挡时使再生怠速转速上升,在齿轮挂挡时,为了防止从停止开始行驶时的急起步而将再生怠速转速设定得低于齿轮为空挡时的再生怠速转速。此外,自动再生中,ECU32使自动再生警告灯36b点灯。
在多级喷射中加上排气管喷射而将DPD再生时,为了防止使废气温度升温至600℃时所堆积的PM一下子燃烧的情况,例如将初期的再生目标温度作为一例设为500℃,如果使DPD内的PM进行了一定程度的燃烧,则控制排气管喷射量,以变更目标温度,将最终再生目标温度作为一例设为600℃。
接下来,说明排气管喷射量的PID控制。
首先,在自动再生中,由图1所说明的废气温度传感器30b检测废气温度,ECU32求出再生目标温度与废气温度的偏差e,基于该偏差,通过PID控制,决定由排气管喷射器39进行排气管喷射的操作量M。
该操作量M由下面的式子表示。
M=Kp·e+Ki·(1/Ti)·∫edt+Kd·Td(de/dt)
在上式中,Kp为比例控制的比例常数,Ki为积分控制的比例常数,Kd为微分控制的比例常数,Ti为积分时间,Td为微分时间,t为时间。
在此,操作量M是由比例控制项、积分控制项、微分控制项的总和来决定的。实际的排气管喷射量是在该操作量M中加上基础项的操作量,并由燃料压力传感器42的燃料压力和排气管喷射器39的开阀时间来决定。
在该PID控制下,在行驶自动再生中,发动机转速也很高,所以能够与排气管喷射量相应地提高废气温度,所以能够对再生目标温度正确地进行控制。
但是,由于等待信号或交通状况,在车辆停车之前,发动机转速降低,废气量也变少,偏差e变大,在该状态下,将车停止并将排气制动阀24和排气节流阀26关闭来增加排气管喷射量,由此控制为DPD25内的废气温度不会降低,发动机旋转从通常的怠速旋转提高至再生怠速转速,从齿轮空挡变为齿轮挂挡,但是该再生怠速转速比行驶时的发动机转速低,因此向发动机的吸气量及废气量也减少,所以很难维持或提高再生目标温度。结果,偏差e变得更大。
在此,在偏差e恒定的情况下,比例控制项和微分控制项是恒定的,但是,积分控制项对该该增大的偏差e进行积分,因此在怠速再生中排气管喷射量会上升至上限值。在该控制状态下,从停止开始行驶并转移到行驶自动再生时,伴随着发动机转速的上升,吸气量也会增大,废气温度急剧地上升,有可能将DPD25熔损。
因此,在本发明中,在车停止而开始怠速自动再生时,与排气制动阀24的关闭动作相应地,将PID控制的控制式中的积分控制项复位为零。通过这样将积分控制项复位为零,不再存在由刚要停车时的车的行驶状态引起的偏差e的积分,基于停车时的偏差e,通过PID控制来决定排气管喷射量而进行怠速自动再生,由此能够进行稳定的怠速自动再生。
此外,在该零复位后进行怠速自动再生的期间,在车从停车起行驶了规定时间以内(例如3分钟以内)的情况下,通过该零复位后的基于PID控制的排气管喷射量的控制来进行行驶自动再生,由此能够无障碍地进行行驶自动再生。此外,在停车时间超过规定时间(例如3分钟)的情况下,基于积分控制项的操作量增大,因此,再次将该积分控制项复位为零而进行行驶自动再生,由此,能够防止废气温度产生过冲。
如上所述,本发明在怠速自动再生时,在通过PID控制来控制排气管喷射量时,通过将PID控制的积分控制项复位为零,能够进行稳定的怠速自动再生,并且,在该怠速自动再生后,根据车的停止时间,判断是再次将积分控制项复位为零,还是不进行复位而继续维持控制,由此,即使从怠速自动再生转移到行驶自动再生,也能够无障碍地进行该切换。
附图标记说明
10 柴油发动机
20 排气管
25 DPD
32 ECU
33 旋转传感器
39 排气管喷射器

Claims (5)

1.一种废气净化系统,在柴油发动机的排气管中连接有捕集废气中的微粒物质的柴油机微粒消除器,在所述柴油机微粒消除器的微粒物质量成为一定量以上时,进行排气管喷射而使柴油发动机的废气温度上升,从而将柴油机微粒消除器自动再生,该废气净化系统的特征在于,
在检测自动再生时的柴油机微粒消除器再生的废气温度,求出检测的废气温度与再生目标温度的偏差,并基于该偏差对排气管喷射量进行PID控制时,在从行驶自动再生转移到停车时的怠速自动再生时,将PID控制中的积分控制项复位为零,来控制排气管喷射量。
2.如权利要求1所述的废气净化系统,其特征在于,
在从所述停车后的怠速自动再生开始起,在规定时间以内转移到行驶自动再生时,继续通过在所述怠速自动再生中将积分控制项复位为零后的PID控制,来控制排气管喷射量。
3.如权利要求1所述的废气净化系统,其特征在于,
在从所述停车后的怠速自动再生开始起,超过规定时间后转移到行驶自动再生时,再次将PID控制的积分控制项复位为零。
4.如权利要求1所述的废气净化系统,其特征在于,
在从行驶自动再生开始将车减速而停车时,在减速时继续通过PID控制进行排气管喷射,在停车后将PID控制的积分控制项复位为零。
5.如权利能要求1~3中任一项所述的废气净化系统,其特征在于,
在开始怠速自动再生时,将排气制动阀关闭,在转移到行驶自动再生时,将排气制动阀打开。
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