JP5655349B2 - Exhaust gas purification control system for internal combustion engine - Google Patents

Exhaust gas purification control system for internal combustion engine Download PDF

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JP5655349B2
JP5655349B2 JP2010083042A JP2010083042A JP5655349B2 JP 5655349 B2 JP5655349 B2 JP 5655349B2 JP 2010083042 A JP2010083042 A JP 2010083042A JP 2010083042 A JP2010083042 A JP 2010083042A JP 5655349 B2 JP5655349 B2 JP 5655349B2
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catalyst
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internal combustion
combustion engine
exhaust gas
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JP2011214495A (en
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朝幸 伊藤
朝幸 伊藤
達夫 益子
達夫 益子
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Isuzu Motors Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—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
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • 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

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Description

本発明は、内燃機関の排気浄化制御システムに関するものである。   The present invention relates to an exhaust gas purification control system for an internal combustion engine.

車両に搭載される内燃機関、例えばディーゼルエンジンの排気ガス中のＮＯｘを浄化する排気浄化制御システムの一つとして、例えばＳＣＲ（選択式触媒還元）システムが開発されている。このＳＣＲシステムは、液体還元剤（反応剤）である例えば尿素水をＳＣＲ触媒の上流に噴射して供給し、排気ガスの熱で尿素を加水分解してアンモニアを生成し、このアンモニアによってＳＣＲ触媒上でＮＯｘを還元して浄化するものである。   For example, an SCR (Selective Catalytic Reduction) system has been developed as one of exhaust purification control systems for purifying NOx in an exhaust gas of an internal combustion engine mounted on a vehicle, for example, a diesel engine. In this SCR system, for example, urea water, which is a liquid reducing agent (reactant), is injected and supplied upstream of the SCR catalyst, and urea is hydrolyzed by the heat of exhaust gas to generate ammonia. In the above, NOx is reduced and purified.

その浄化の際に、ＳＣＲ触媒には一部のアンモニアが吸着し、この吸着したアンモニアがＳＣＲ触媒上でＮＯｘを高反応に還元することができる。そこで、浄化率を向上させるために、アンモニアの吸着量を制御するようにした排気浄化制御システム（触媒の作動方法およびその方法を実施する装置）が提案されている（例えば、特許文献１参照）。   During the purification, a part of ammonia is adsorbed on the SCR catalyst, and this adsorbed ammonia can reduce NOx to a high reaction on the SCR catalyst. In order to improve the purification rate, an exhaust gas purification control system (catalyst operation method and apparatus for carrying out the method) that controls the adsorption amount of ammonia has been proposed (see, for example, Patent Document 1). .

前記排気浄化制御システムは、ＮＯｘ浄化率からアンモニアの消費量を求め、アンモニアの供給量から前記消費量を差し引いた値を吸着量として算出し、この吸着量が目標吸着量になるように供給量を制御するものである（このように積算値による目標吸着量制御を積算値制御ともいう）。前記目標吸着量は、例えば温度の関数である飽和吸着量曲線から決定される。   The exhaust purification control system obtains the amount of ammonia consumed from the NOx purification rate, calculates a value obtained by subtracting the amount of consumption from the amount of ammonia supplied as an adsorption amount, and supplies the amount so that this amount of adsorption becomes the target adsorption amount. (The target adsorption amount control based on the integrated value is also referred to as integrated value control in this way). The target adsorption amount is determined from, for example, a saturated adsorption amount curve that is a function of temperature.

特開２００６−１７１１５号公報JP 2006-17115 A

しかしながら、前記排気浄化制御システムにおいては、各パラメータを積算した値で制御しているため、誤差も積算され、真値とのずれが拡大しやすい。このような現象は、例えば上り坂走行時等の過渡的運転状況において発生しやすい。このため、アンモニアの供給不足（不足配量）による浄化率の低下やアンモニアの供給過多（過剰配量）によるアンモニアスリップが起きやすく、浄化率が大幅に悪化するという問題がある。このような問題を解消するには、尿素水の無噴射状態を一定時間設定するなどしてリセットを行う必要があり、手間がかかると共に、頻繁にリセットは行えないため、真値とのずれをなくすことは困難である。   However, in the exhaust purification control system, since the control is performed using the values obtained by integrating the parameters, the errors are also integrated and the deviation from the true value is likely to increase. Such a phenomenon is likely to occur in a transitional driving situation such as when traveling uphill. For this reason, there is a problem that the purification rate decreases due to insufficient supply of ammonia (insufficient metering) and ammonia slip due to excessive supply of ammonia (excess metering) tends to occur, and the purification rate significantly deteriorates. In order to solve such problems, it is necessary to reset the non-injection state of urea water for a certain period of time, etc., which is time consuming and cannot be reset frequently. It is difficult to lose.

本発明は、前記事情を考慮してなされたものであり、積算値制御の問題点である真値とのずれに起因する浄化率の悪化をなくすことができると共に、リセットを行う手間を省くことができる内燃機関の排気浄化制御システムを提供することを目的とする。   The present invention has been made in view of the above circumstances, and can eliminate the deterioration of the purification rate due to the deviation from the true value, which is a problem of the integrated value control, and can save the trouble of resetting. An object is to provide an exhaust gas purification control system for an internal combustion engine.

前記目的を達成するために、本発明は、内燃機関の排気通路に設けられ排気ガスを浄化する触媒と、該触媒よりも上流側に前記触媒の反応に必要な反応剤を供給する反応剤供給手段と、該反応剤供給手段による反応剤の供給量を制御する制御装置とを備えた内燃機関の排気浄化制御システムにおいて、前記制御装置が、内燃機関の運転状況から基本反応剤供給量を算出する工程と、過渡時の前記触媒の温度変化率から前記基本反応剤供給量に対する補正量を算出すると共に、前記温度変化率が大きいほど前記補正量が小さくなるように前記補正量を算出する工程と、前記基本反応剤供給量および前記補正量から目標反応剤供給量を算出する工程とを実行するように構成されていることを特徴とする。 In order to achieve the above object, the present invention provides a catalyst for purifying exhaust gas provided in an exhaust passage of an internal combustion engine, and a reactant supply for supplying a reactant necessary for the reaction of the catalyst upstream of the catalyst. And an exhaust gas purification control system for an internal combustion engine comprising a control device for controlling the supply amount of the reactant by the reactant supply means, wherein the control device calculates a basic reactant supply amount from an operating state of the internal combustion engine Calculating a correction amount for the basic reactant supply amount from a temperature change rate of the catalyst at the time of transition, and calculating the correction amount so that the correction amount decreases as the temperature change rate increases. And a step of calculating a target reactant supply amount from the basic reactant supply amount and the correction amount.

前記補正量を算出するとき、前記触媒の温度が高いほど補正量が小さくなるように算出することが好ましい。 When calculating the correction amount, it is preferable to calculate so that the correction amount decreases as the temperature of the catalyst increases .

前記触媒が排気ガス中のＮＯｘを浄化するＳＣＲ触媒であり、前記反応剤が尿素水であり、前記内燃機関の運転状況が、エンジン回転数およびアクセル開度から求められることが好ましい。 It is preferable that the catalyst is an SCR catalyst that purifies NOx in exhaust gas, the reactant is urea water, and the operating state of the internal combustion engine is obtained from the engine speed and the accelerator opening.

本発明によれば、積算値による目標吸着量制御ではなく、過渡時の触媒温度変化率による吸着量および脱離量のみに応じた反応剤噴射量の補正を行うため、積算値制御の問題点である真値とのずれに起因する浄化率の悪化をなくすことができると共に、リセットを行う手間を省くことができる。   According to the present invention, since the target injection amount control based on the integrated value is not corrected, the reactant injection amount is corrected only in accordance with the adsorption amount and the desorption amount based on the catalyst temperature change rate at the time of transient. In addition, it is possible to eliminate the deterioration of the purification rate due to the deviation from the true value, and it is possible to save the trouble of resetting.

本発明の実施形態に係る内燃機関の排気浄化制御システムの一例を概略的に示す図である。1 is a diagram schematically showing an example of an exhaust gas purification control system for an internal combustion engine according to an embodiment of the present invention. FIG. 触媒温度とアンモニアの吸着量との関係を示すグラフである。It is a graph which shows the relationship between catalyst temperature and the adsorption amount of ammonia. 制御装置により行われる制御の工程を示すフローチャートである。It is a flowchart which shows the process of the control performed by a control apparatus.

以下に、本発明を実施するための形態を添付図面に基いて詳述する。   EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is explained in full detail based on an accompanying drawing.

本実施形態に係る内燃機関の排気浄化制御システムの一例を示す図１において、１は自動車用の内燃機関例えばディーゼルエンジンであり、２５はこのエンジン１の排気浄化制御システムである。このエンジン１は、複数のシリンダ、ピストン、シリンダブロックおよびクランクシャフト等を含むエンジン本体２を有し、このエンジン本体２には吸気マニホールド３および排気マニホールド４が設けられている。吸気マニホールド３は、吸気が流れる吸気通路（吸気管）５の下流端部を形成している。同様に排気マニホールド４は、排気ガスが流れる排気通路（排気管）６の上流端部を形成している。   In FIG. 1 showing an example of an exhaust gas purification control system for an internal combustion engine according to this embodiment, reference numeral 1 denotes an internal combustion engine for automobiles, for example, a diesel engine, and reference numeral 25 denotes an exhaust gas purification control system for the engine 1. The engine 1 has an engine body 2 including a plurality of cylinders, pistons, cylinder blocks, a crankshaft, and the like. The engine body 2 is provided with an intake manifold 3 and an exhaust manifold 4. The intake manifold 3 forms a downstream end portion of an intake passage (intake pipe) 5 through which intake air flows. Similarly, the exhaust manifold 4 forms an upstream end portion of an exhaust passage (exhaust pipe) 6 through which exhaust gas flows.

エンジン本体２には、排気ガスの一部すなわちＥＧＲガスを吸気側に還流するためのＥＧＲ装置７が設けられている。このＥＧＲ装置７は、排気通路６内（特に排気マニホールド４内）の排気ガスの一部を吸気通路５内（特に吸気マニホールド３内）に還流させるためのＥＧＲ通路８と、このＥＧＲ通路８を流れるＥＧＲガスを冷却するＥＧＲクーラ９と、ＥＧＲ通路８の下流側に設けられ、ＥＧＲガスの流量を調節するＥＧＲ弁１０とを備えている。   The engine body 2 is provided with an EGR device 7 for returning a part of the exhaust gas, that is, EGR gas to the intake side. The EGR device 7 includes an EGR passage 8 for returning a part of exhaust gas in the exhaust passage 6 (particularly in the exhaust manifold 4) to the intake passage 5 (particularly in the intake manifold 3), and the EGR passage 8 An EGR cooler 9 that cools the flowing EGR gas, and an EGR valve 10 that is provided on the downstream side of the EGR passage 8 and adjusts the flow rate of the EGR gas are provided.

前記排気通路６の途中には排気ガス浄化装置の一つであるＮＯｘ還元用のＳＣＲ装置（ＳＣＲユニットともいう。）１１が接続されていると共に、このＳＣＲ装置１１の上流（排気ガス上流）には液体還元剤（反応剤）である尿素水１２をＳＣＲ装置１１のＳＣＲ触媒１３に供給する液体還元剤供給手段（反応剤供給手段）３０を構成する噴射ノズル１４が設けられている。   An NOx reduction SCR device (also referred to as an SCR unit) 11, which is one of exhaust gas purification devices, is connected in the middle of the exhaust passage 6, and upstream (exhaust gas upstream) of the SCR device 11. Is provided with an injection nozzle 14 constituting a liquid reducing agent supply means (reactant supply means) 30 for supplying urea water 12 as a liquid reducing agent (reactant) to the SCR catalyst 13 of the SCR device 11.

前記反応剤供給手段３０は、尿素水を貯蔵した尿素水貯蔵タンク１６と、この尿素水貯蔵タンク１６から尿素水供給パイプ１５を介して供給される尿素水１２を排気通路６内に噴射する噴射ノズル１４とから主に構成されている。尿素水貯蔵タンク１６は、尿素水１２を尿素水供給パイプ１５を介して噴射ノズル１４に圧送するように構成されている。   The reactant supply means 30 is a jet for injecting urea water 12 stored in the urea water through the urea water storage tank 16 through the urea water supply pipe 15 into the exhaust passage 6. The nozzle 14 is mainly composed. The urea water storage tank 16 is configured to pump the urea water 12 to the injection nozzle 14 via the urea water supply pipe 15.

前記ＳＣＲ装置１１は、ＳＣＲ触媒１３と、このＳＣＲ触媒１３を収容した円筒状の容器１７と、この容器１７の前端部と後端部に接続された漏斗状の排気ガス入口部材１７ａおよび排気ガス出口部材１７ｂとから主に構成されている。   The SCR device 11 includes an SCR catalyst 13, a cylindrical container 17 containing the SCR catalyst 13, a funnel-shaped exhaust gas inlet member 17a connected to the front end and the rear end of the container 17, and an exhaust gas. It is mainly composed of the outlet member 17b.

エンジン本体２にはエンジン回転数を検出するエンジン回転数センサ１８が設けられ、エンジン回転数を制御するアクセルにはアクセル開度を検出するアクセル開度センサ１９が設けられている。吸気通路５には吸気流量を検出する流量センサ２０が設けられている。排気通路６にはＳＣＲ装置１１の上流側と下流側にＮＯｘセンサ２１，２２が設けられていると共に、ＳＣＲ装置１１の下流側に排気温度を検出する排気温度センサ２３が設けられている。このＳＣＲ装置１１の下流側の排気温度からＳＣＲ触媒の温度を推定することができる。   The engine body 2 is provided with an engine speed sensor 18 for detecting the engine speed, and the accelerator for controlling the engine speed is provided with an accelerator position sensor 19 for detecting the accelerator position. The intake passage 5 is provided with a flow rate sensor 20 for detecting the intake flow rate. In the exhaust passage 6, NOx sensors 21 and 22 are provided on the upstream side and the downstream side of the SCR device 11, and an exhaust temperature sensor 23 for detecting the exhaust temperature is provided on the downstream side of the SCR device 11. The temperature of the SCR catalyst can be estimated from the exhaust gas temperature downstream of the SCR device 11.

前記排気浄化制御システム２５は、エンジン１の運転状況に基いて尿素水１２の供給料を制御する、例えば前記噴射ノズル１４からの尿素水１２の噴射量を制御する制御装置２４を備えている。本実施形態のエンジン１の運転状況は、例えばエンジン回転数およびアクセル開度から求めることができる。制御装置２４は、図３に示すように、運転状況を検出するために例えばアクセル開度センサ１９を介してアクセル開度を、エンジン回転数センサ１８を介してエンジン回転数を読み込む工程（第１ステップ）Ｓ１と、これらアクセル開度およびエンジン回転数から基本反応剤供給量である基本尿素水噴射量Ｕｂを算出する工程（第２ステップ）Ｓ２と、排気温度センサ２３により過渡時の触媒の温度変化率（変化量）ΔＴを読み込む工程（第３ステップ）Ｓ３と、その触媒温度変化率ΔＴから前記基本尿素水噴射量Ｕｂに対するアンモニアの吸着量ないし脱離量である補正量Ｎｃを算出する工程（第４ステップ）Ｓ４と、前記基本尿素水噴射量Ｕｂおよび前記補正量Ｎｃから目標尿素水噴射量を算出する工程（第５ステップ）Ｓ５とを実行するように構成されている。これにより、目標尿素水噴射量の尿素水が前記噴射ノズル１４から噴射供給される（第６ステップＳ６）。   The exhaust purification control system 25 includes a control device 24 that controls the supply amount of the urea water 12 based on the operating state of the engine 1, for example, controls the injection amount of the urea water 12 from the injection nozzle 14. The operating status of the engine 1 of the present embodiment can be obtained from, for example, the engine speed and the accelerator opening. As shown in FIG. 3, the control device 24 reads the accelerator opening through the accelerator opening sensor 19 and the engine rotation speed through the engine rotation sensor 18 in order to detect the driving situation (first operation) (first step). Step) S1, a step of calculating a basic urea water injection amount Ub, which is a basic reactant supply amount, from the accelerator opening and the engine speed (second step) S2, and the temperature of the catalyst during the transition by the exhaust temperature sensor 23 A step of reading the rate of change (amount of change) ΔT (third step) S3 and a step of calculating a correction amount Nc that is an adsorption amount or desorption amount of ammonia with respect to the basic urea water injection amount Ub from the catalyst temperature change rate ΔT. (Fourth Step) S4 and a step (fifth step) S5 of calculating a target urea water injection amount from the basic urea water injection amount Ub and the correction amount Nc are executed. It is configured as follows. Thereby, the urea water of the target urea water injection amount is injected and supplied from the injection nozzle 14 (sixth step S6).

基本尿素水噴射量Ｕｂ（ｍｇ）は、制御装置２４がアクセル開度とエンジン回転数からＮＯｘ排出量を算出し、必要尿素水噴射量を求めて決定する。この基本尿素水噴射量Ｕｂは、アクセル開度およびエンジン回転数の単位時間当たりの変化量（変化率）に応じて触媒へのアンモニア吸着・脱離量を推定して補正する。   The basic urea water injection amount Ub (mg) is determined by the control device 24 calculating the NOx emission amount from the accelerator opening and the engine speed and obtaining the required urea water injection amount. This basic urea water injection amount Ub is corrected by estimating the amount of ammonia adsorbed / desorbed from the catalyst according to the amount of change (change rate) per unit time of the accelerator opening and the engine speed.

前記第３ステップＳ３および第４ステップＳ４においては、触媒温度変化率ΔＴすなわち単位時間（ｔ[ｍｓ]後）当たりの排気温度変化率（変化量）ΔＴに基いてアンモニアの吸着・脱離量を推定して補正する。   In the third step S3 and the fourth step S4, the adsorption / desorption amount of ammonia is determined based on the catalyst temperature change rate ΔT, that is, the exhaust temperature change rate (change amount) ΔT per unit time (after t [ms]). Estimate and correct.

単純に比例として考えて、Ｎｃ＝Ｃ０＋Ｃ１×ΔＴとし、この演算式から基本尿素水噴射量Ｕｂに対して増量もしくは減量する補正量Ｎｃを算出する。ここで、Ｃ０は初期値、Ｃ１は負（Ｃ１＜０）の補正係数である。触媒に吸着されるアンモニアの初期値Ｃ０は、初期は、製造時の吸着量が０であると考えて最初に尿素水を噴射する際の目標吸着量を決定し、走行距離の増加に伴い例えばマイナスに増加させ、Ｃ０＝０ｍｇにする。触媒温度変化率(変化量) ΔＴとアンモニアの吸着量（補正量）Ｎｃとの関係は、図２に示す通りであり、触媒温度の上昇に伴ってアンモニアの吸着量（補正量）Ｎｃが低下する。前記演算式を用いることにより、容易に補正量Ｎｃを算出することができる。   Simply considering it as proportional, Nc = C0 + C1 × ΔT, and a correction amount Nc that is increased or decreased with respect to the basic urea water injection amount Ub is calculated from this arithmetic expression. Here, C0 is an initial value, and C1 is a negative (C1 <0) correction coefficient. The initial value C0 of ammonia adsorbed on the catalyst is initially determined to be a target adsorption amount when first injecting urea water on the assumption that the adsorption amount at the time of manufacture is 0. Increase to minus, C0 = 0 mg. The relationship between the catalyst temperature change rate (change amount) ΔT and the ammonia adsorption amount (correction amount) Nc is as shown in FIG. 2. As the catalyst temperature rises, the ammonia adsorption amount (correction amount) Nc decreases. To do. By using the arithmetic expression, the correction amount Nc can be easily calculated.

図２では、同じΔＴにおいても触媒温度が低い場合と高い場合とでは、補正量が異なるグラフになっているが、これは前記演算式におけるＣ１の係数が異なることにより補正量Ｎｃが異なることを表している。補正量Ｎｃの決定には、触媒温度の変化率（変化量）ΔＴだけでなく、触媒温度自体も必要である。図２における触媒温度と補正量の関係を表す反比例曲線上のある触媒温度での傾きに対応してＣ１が決定され、触媒温度の変化によりＣ１は反比例曲線の傾きに対応して変化する。   In FIG. 2, even when the catalyst temperature is low and high even at the same ΔT, the correction amount is different in the graph. This is because the correction amount Nc is different due to the difference in the coefficient of C1 in the arithmetic expression. Represents. In order to determine the correction amount Nc, not only the change rate (change amount) ΔT of the catalyst temperature but also the catalyst temperature itself is necessary. C1 is determined corresponding to the slope at a certain catalyst temperature on the inversely proportional curve representing the relationship between the catalyst temperature and the correction amount in FIG. 2, and C1 changes corresponding to the slope of the inversely proportional curve as the catalyst temperature changes.

本実施形態の排気浄化制御システム２５によれば、制御装置２４が、エンジン１の運転状態例えばアクセル開度およびエンジン回転数をアクセル開度センサ１９とエンジン回転数センサ１８により読み込む工程Ｓ１と、これらアクセル開度およびエンジン回転数から基本反応剤供給量例えば基本尿素水噴射量Ｕｂを算出する工程（第２ステップ）Ｓ２と、過渡時のＳＣＲ触媒１３の温度変化率（変化量）である排気温度の変化率（変化量）ΔＴを読み込む工程（第３ステップ）Ｓ３と、その触媒の温度変化率ΔＴから前記基本尿素水噴射量Ｕｂに対するアンモニアの吸着量ないし脱離量である補正量Ｎｃを算出する工程（第４ステップ）Ｓ４と、前記基本尿素水噴射量Ｕｂおよび前記補正量Ｎｃから目標尿素水噴射量を算出する工程（第５ステップ）Ｓ５とを実行するように構成されているため、正確な目標尿素水噴射量の尿素水をＳＣＲ触媒１３に供給することができ、過渡時（坂道走行などの過渡的運転状況）でも浄化率の向上が図れ、従来の積算値制御の問題点である真値とのずれによる浄化率の悪化をなくすことができると共に、リセットを行う手間を省くことができる。   According to the exhaust gas purification control system 25 of the present embodiment, the control device 24 reads the operating state of the engine 1 such as the accelerator opening degree and the engine speed by the accelerator opening degree sensor 19 and the engine speed sensor 18, and these steps S1. A step (second step) S2 of calculating a basic reactant supply amount, for example, a basic urea water injection amount Ub, from the accelerator opening and the engine speed, and an exhaust temperature which is a temperature change rate (change amount) of the SCR catalyst 13 at the time of transition. A correction amount Nc, which is an adsorption amount or desorption amount of ammonia with respect to the basic urea water injection amount Ub, is calculated from the step (third step) S3 of reading the change rate (change amount) ΔT of the catalyst and the temperature change rate ΔT of the catalyst. Step (fourth step) S4 and a step (fifth step) of calculating the target urea water injection amount from the basic urea water injection amount Ub and the correction amount Nc. ) Since it is configured to execute S5, it is possible to supply an accurate target urea water injection amount of urea water to the SCR catalyst 13, and even in a transient state (transient operating conditions such as running on a slope). The purification rate can be improved, the deterioration of the purification rate due to the deviation from the true value, which is a problem of the conventional integrated value control, can be eliminated, and the trouble of resetting can be saved.

以上、本発明の実施の形態を図面により詳述してきたが、本発明は前記実施の形態に限定されるものではなく、本発明の要旨を逸脱しない範囲での種々の設計変更が可能である。例えば、前記補正量は、前記演算式の代わりに、実験から三次元マップを作成して算出する方法であってもよい。排気通路にはＳＣＲ触媒以外の他の排ガス浄化装置例えばＤＯＣ（ディーゼル用酸化触媒）等も設けられていてもよい。   The embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the gist of the present invention. . For example, the correction amount may be calculated by creating a three-dimensional map from an experiment instead of the arithmetic expression. An exhaust gas purification device other than the SCR catalyst, for example, DOC (diesel oxidation catalyst) or the like may be provided in the exhaust passage.

１ エンジン（内燃機関）
６ 排気通路
１２ 尿素水（反応剤）
１３ ＳＣＲ触媒（触媒）
２４ 制御装置
２５ 排気浄化制御システム
３０ 反応剤供給手段 1 engine (internal combustion engine)
6 Exhaust passage 12 Urea water (reactant)
13 SCR catalyst (catalyst)
24 control device 25 exhaust purification control system 30 reactant supply means

Claims (3)

内燃機関の排気通路に設けられ排気ガスを浄化する触媒と、該触媒よりも上流側に前記触媒の反応に必要な反応剤を供給する反応剤供給手段と、該反応剤供給手段による反応剤の供給量を制御する制御装置とを備えた内燃機関の排気浄化制御システムにおいて、前記制御装置が、内燃機関の運転状況から基本反応剤供給量を算出する工程と、過渡時の前記触媒の温度変化率から前記基本反応剤供給量に対する補正量を算出すると共に、前記温度変化率が大きいほど前記補正量が小さくなるように前記補正量を算出する工程と、前記基本反応剤供給量および前記補正量から目標反応剤供給量を算出する工程とを実行するように構成されていることを特徴とする内燃機関の排気浄化制御システム。 A catalyst for purifying exhaust gas provided in an exhaust passage of the internal combustion engine; a reactant supply means for supplying a reactant necessary for the reaction of the catalyst upstream of the catalyst; and a reactant supplied by the reactant supply means. An exhaust gas purification control system for an internal combustion engine comprising a control device for controlling a supply amount, wherein the control device calculates a basic reactant supply amount from an operating state of the internal combustion engine, and a temperature change of the catalyst during a transition Calculating a correction amount for the basic reactant supply amount from a rate, and calculating the correction amount so that the correction amount decreases as the temperature change rate increases, and the basic reactant supply amount and the correction amount An exhaust purification control system for an internal combustion engine, characterized in that the step of calculating a target reactant supply amount from the engine is executed. 前記補正量を算出するとき、前記触媒の温度が高いほど補正量が小さくなるように算出することを特徴とする請求項１記載の内燃機関の排気浄化制御システム。 2. The exhaust gas purification control system for an internal combustion engine according to claim 1, wherein the correction amount is calculated such that the correction amount decreases as the temperature of the catalyst increases . 前記触媒が排気ガス中のＮＯｘを浄化するＳＣＲ触媒であり、前記反応剤が尿素水であり、前記内燃機関の運転状況が、エンジン回転数およびアクセル開度から求められることを特徴とする請求項１又は２記載の内燃機関の排気浄化制御システム。 The catalyst is an SCR catalyst that purifies NOx in exhaust gas, the reactant is urea water, and an operating state of the internal combustion engine is obtained from an engine speed and an accelerator opening. 3. An exhaust gas purification control system for an internal combustion engine according to 1 or 2.
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