JP2007187146A - Controller for internal combustion engine - Google Patents

Controller for internal combustion engine Download PDF

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JP2007187146A
JP2007187146A JP2006209495A JP2006209495A JP2007187146A JP 2007187146 A JP2007187146 A JP 2007187146A JP 2006209495 A JP2006209495 A JP 2006209495A JP 2006209495 A JP2006209495 A JP 2006209495A JP 2007187146 A JP2007187146 A JP 2007187146A
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fuel ratio
value
air
internal combustion
combustion engine
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JP4646868B2 (en
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Hisao Haga
久夫 羽賀
Norio Suzuki
典男 鈴木
Katsuji Wada
勝治 和田
Nobuhiro Komatsu
伸裕 小松
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Honda Motor Co Ltd
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Honda Motor Co Ltd
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Priority to US11/882,255 priority patent/US8028518B2/en
Priority to EP07015037A priority patent/EP1887202B1/en
Priority to DE602007004039T priority patent/DE602007004039D1/en
Priority to DE602007001740T priority patent/DE602007001740D1/en
Priority to EP07015038A priority patent/EP1887203B1/en
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for an internal combustion engine capable of accurately carrying out sulfur purging of LNC without complication of structure or increase in manufacturing costs. <P>SOLUTION: In the controller for the internal combustion engine having a treating means for removing sulfur components adsorbed by the LNC provided in an exhaust passage, values of differences are integrated between a predetermined reference value and detected values of an upstream side air-fuel ratio detecting means for detecting a value corresponding to an air-fuel ratio in an upstream side of the LNC, and sulfur purging is ended when the integrated value reaches a predetermined value. Alternatively, values of differences between values corresponding to respective air-fuel ratios in an upstream side and a downstream side of the LNC are integrated, and sulfur purging is ended when the integrated value reaches a predetermined value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、内燃機関の制御装置に関し、特に、排出ガス中の窒素酸化物を浄化するための触媒装置から硫黄分を除去する処理を実行し得るように構成された内燃機関の制御装置に関するものである。   The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine configured to be able to execute a process of removing sulfur from a catalyst device for purifying nitrogen oxides in exhaust gas. It is.

ディーゼル内燃機関の排気通路には、排出ガス中の窒素酸化物（以下、ＮＯＸと略称する）を還元浄化するためのリーンＮＯＸ浄化触媒（以下、ＬＮＣと略称する）が設けられることがある。このＬＮＣにおいては、排出ガスの空燃比（以下、排気Ａ／Ｆと略称する）が所定値よりも高い（以下、リーンと呼称する）時、換言すると酸素濃度が高い時に取り込んだＮＯＸを、排気Ａ／Ｆが所定値よりも低い（以下、リッチと呼称する）時、換言すると酸素濃度が低下した時に放出し且つ還元して無害化する処理を行っている。またＬＮＣは、ＮＯＸ吸収量が増大するとその吸収性能が低下するので、適時、燃焼状態を変化させ、還元剤であるＣＯやＨＣ濃度を高めると共に酸素濃度を低下させ、それによってＬＮＣからのＮＯＸ放出を促進させ且つ十分に還元浄化させるようにしている。 The exhaust passage of a diesel internal combustion engine may be provided with a lean NO X purification catalyst (hereinafter abbreviated as LNC) for reducing and purifying nitrogen oxide (hereinafter abbreviated as NO X ) in exhaust gas. . In this LNC, when the air-fuel ratio of exhaust gas (hereinafter referred to as exhaust A / F) is higher than a predetermined value (hereinafter referred to as lean), in other words, NO X taken in when the oxygen concentration is high, When the exhaust A / F is lower than a predetermined value (hereinafter referred to as rich), in other words, when the oxygen concentration is reduced, the exhaust A / F is released and reduced to be harmless. Further, since the absorption performance of LNC decreases as the amount of NO X absorbed increases, the combustion state is changed in a timely manner, and the concentration of CO and HC as reducing agents is increased and the oxygen concentration is decreased. X release is promoted and reduced and purified sufficiently.

他方、燃料には硫黄分が含まれているため、硫黄酸化物（以下ＳＯＸと略称する）や硫化水素（以下Ｈ２Ｓと略称する）も排出される。これらの硫黄分がＬＮＣに吸収されると、ＬＮＣのＮＯＸ浄化性能が低下するので、ＬＮＣに吸収された硫黄分を適時放出する必要がある。このＬＮＣからの硫黄分の放出処理（以下、サルファパージと呼称する）として、吸入行程中に噴射される主燃料噴射に加えて、燃焼後補助燃料噴射（ 以下ポスト噴射と略称する）を行うことにより、ＬＮＣ温度を所定値以上に上昇させるのに必要な未燃燃料を排気通路に供給して排気Ａ／Ｆをリッチ化することにより、ＬＮＣの発熱を誘起していた（特許文献１を参照されたい）。 On the other hand, since the fuel contains sulfur, sulfur oxides (hereinafter abbreviated as SO X ) and hydrogen sulfide (hereinafter abbreviated as H 2 S) are also discharged. If these sulfur is absorbed in LNC, so NO X purification performance LNC is reduced, it is necessary to timely release a sulfur absorbed by the LNC. As a process of releasing sulfur from the LNC (hereinafter referred to as sulfur purge), in addition to the main fuel injection injected during the intake stroke, post-combustion auxiliary fuel injection (hereinafter abbreviated as post injection) is performed. As a result, unburned fuel necessary to raise the LNC temperature to a predetermined value or more is supplied to the exhaust passage to enrich the exhaust A / F, thereby inducing heat generation of the LNC (see Patent Document 1) I want to be)

このサルファパージは、燃料消費率の悪化やＬＮＣの熱劣化を招くので、過度に行うことは好ましいことではない。そこでサルファパージの終了時期を正確に判断できることが望まれている。このために、燃料消費量からＳＯＸの蓄積量を推定し、この推定蓄積量から逆算してサルファパージ中のＳＯＸ放出量を推定し、推定放出量が所定値に到達した時点でサルファパージを終了させる手法（特許文献２を参照されたい）や、ＬＮＣの前後にＳＯＸセンサを設置し、ＬＮＣから放出されるＳＯＸが所定量以下になった時点でサルファパージを終了させる手法（特許文献３を参照されたい）が知られている。
特開２００１−１７３４９８号公報 特開２０００−１１０５５２号公報 特開２００１−３７８２号公報 Since this sulfur purge causes deterioration of the fuel consumption rate and thermal deterioration of the LNC, it is not preferable to perform it excessively. Therefore, it is desired that the end time of sulfur purge can be accurately determined. For this purpose, the accumulated amount of SO X is estimated from the fuel consumption, and the SO X released amount during sulfur purge is estimated by calculating backward from this estimated accumulated amount, and when the estimated released amount reaches a predetermined value, the sulfur purge (See Patent Document 2), or a method of installing SO X sensors before and after the LNC and ending the sulfur purge when the SO X released from the LNC falls below a predetermined amount (patent Reference 3) is known.
JP 2001-173498 A JP 2000-110552 A JP 2001-3782 A

しかるに、文献２に記載の手法は、あくまでも推定値によるものなので、サルファパージが不十分であるのに終了してしまったり、サルファパージが既に終了しているのに必要以上に継続されたりすることがあり得た。   However, since the method described in Document 2 is based on an estimated value, it may end even if the sulfur purge is insufficient, or may continue more than necessary even if the sulfur purge has already ended. Could be.

また、文献３に記載の手法は、サルファパージの終了を正確に判断できる反面、複数のセンサを隣接させて設置しなければならないため、設置スペースの確保が問題となる上、製造コストを圧迫するといった問題がある。   In addition, while the method described in Document 3 can accurately determine the end of the sulfur purge, a plurality of sensors must be installed adjacent to each other, so that securing the installation space becomes a problem and the manufacturing cost is reduced. There is a problem.

本発明は、このような従来技術の不都合を解消すべく案出されたものであり、その主な目的は、構造の複雑化や製造コストの増大を招かずにＬＮＣのサルファパージを的確に実行することが可能な内燃機関の制御装置を提供することにある。   The present invention has been devised to eliminate such disadvantages of the prior art, and its main purpose is to accurately execute the LNC sulfur purge without complicating the structure and increasing the manufacturing cost. An object of the present invention is to provide a control device for an internal combustion engine that can be used.

このような目的を達成するために本発明は、排気通路に設けられたＬＮＣに吸着された硫黄分を除去するための処理手段を有する内燃機関の制御装置において、ＬＮＣの上流側の空燃比に対応する値を検出する上流側空燃比検出手段（Ｏ２センサ２７Ｕ）を有し、該上流側空燃比検出手段の検出値をサルファパージ終了時期の判断に含ませることを特徴とするものとした（請求項１）。特に、上流側空燃比検出手段の検出値と所定の基準値（理論空燃比）との差の値の積算値をサルファパージ終了時期の判断に含ませるようにする（請求項２）と良く、更に、ＬＮＣにおけるＣＯ消費率に対応する値を検出し、この検出値をサルファパージ終了時期の判断に含ませるようにする（請求項３）と良い。
また、ＬＮＣの上流側空燃比検出手段（Ｏ２センサ２７Ｕ）と下流側空燃比検出手段（Ｏ２センサ２７Ｌ）との検出値をサルファパージ終了時期の判断に含ませることを特徴とするものとした（請求項４）。この場合は特に、上流側空燃比検出手段の検出値と下流側空燃比検出手段の検出値との差の値の積算値をサルファパージ終了時期の判断に含ませると良い（請求項５）。
さらに、ＬＮＣに流入する排気の空間速度を検出し、この検出値をサルファパージ終了時期の判断に含ませるものとすると良い（請求項６）。 In order to achieve such an object, the present invention provides a control device for an internal combustion engine having a processing means for removing sulfur adsorbed by an LNC provided in an exhaust passage. An upstream air-fuel ratio detecting means (O 2 sensor 27U) for detecting a corresponding value is provided, and the detected value of the upstream air-fuel ratio detecting means is included in the determination of the sulfur purge end timing. (Claim 1). In particular, the integrated value of the difference between the detection value of the upstream air-fuel ratio detection means and the predetermined reference value (theoretical air-fuel ratio) may be included in the determination of the sulfur purge end time. Furthermore, a value corresponding to the CO consumption rate in the LNC is detected, and this detected value may be included in the determination of the sulfur purge end time.
The detection values of the upstream air-fuel ratio detection means (O 2 sensor 27U) and the downstream air-fuel ratio detection means (O 2 sensor 27L) of the LNC are included in the determination of the sulfur purge end timing. (Claim 4). In this case, in particular, the integrated value of the difference between the detection value of the upstream air-fuel ratio detection means and the detection value of the downstream air-fuel ratio detection means may be included in the determination of the sulfur purge end timing.
Further, it is preferable that the space velocity of the exhaust gas flowing into the LNC is detected, and this detected value is included in the determination of the sulfur purge end time.

このような本発明によれば、Ｓ被毒量を常時監視してその時のＳ被毒量に対応したサルファパージに必要な還元剤量を把握し、その値をサルファパージの終了判断基準値とすることができるので、Ｓ被毒量が変化した場合や、格別なサルファパージ制御を実行していないとき（自然パージ可能環境下など）であっても、サルファパージ実行期間の最適化を図ることができる。また、硫黄分を検出するためのセンサを設置する必要がないので、コスト増大や設置スペースの問題を生ずることもない。
特に、ＬＮＣにおけるＣＯ消費率やＬＮＣに流入する排気の空間速度の検出値でサルファパージ終了時期の判断基準値を補正するものとすれば、触媒との接触、反応確率変化の影響による還元剤消費量の変化度合いを考慮することができ、サルファパージの終了時期の判断をより一層的確に行うことができる。 According to the present invention, the sulfur poisoning amount is constantly monitored, the amount of reducing agent necessary for sulfur purge corresponding to the sulfur poisoning amount at that time is grasped, and this value is used as the reference value for determining the end of sulfur purge. Therefore, the sulfur purge execution period should be optimized even when the amount of sulfur poisoning changes or when special sulfur purge control is not being executed (such as in a naturally purgeable environment). Can do. Further, since there is no need to install a sensor for detecting the sulfur content, there is no problem of cost increase and installation space.
In particular, if the judgment reference value of the sulfur purge end timing is corrected by the detected value of the CO consumption rate in the LNC and the space velocity of the exhaust gas flowing into the LNC, the consumption of the reducing agent due to the contact with the catalyst and the influence of the reaction probability change The degree of change in the amount can be taken into consideration, and the end time of sulfur purge can be determined more accurately.

以下に添付の図面を参照して本発明について詳細に説明する。   Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

図１は、本発明が適用される内燃機関Ｅの基本的な構成図である。この内燃機関（ディーゼルエンジン）Ｅは、その機械的な構成自体は周知のものと何ら変わるところはなく、過給圧可変機構付きターボチャージャ１を備えるものであり、ターボチャージャ１のコンプレッサ側に吸気通路２が連結され、ターボチャージャ１のタービン側に排気通路３が連結されている。そして吸気通路２の上流端にエアクリーナ４が接続され、吸気通路２の適所に燃焼室に流入する新気の流量を調節するための吸気制御弁５と、低回転低負荷運転域で流路断面積を絞って吸気流速を高めるためのスワールコントロール弁６とが設けられている。また排気通路３の下流端には、酸化触媒（以下、ＤＯＣと略称する）７と、煤などの粒子状物質を除去するフィルタ（以下、DＰＦと略称する）８と、前記したＬＮＣ９とを、排気の流れに沿ってこの順に連設してなる排気浄化装置１０が接続されている。   FIG. 1 is a basic configuration diagram of an internal combustion engine E to which the present invention is applied. The internal combustion engine (diesel engine) E has a mechanical configuration that is not different from that of a known one, and includes a turbocharger 1 with a supercharging pressure variable mechanism. A passage 2 is connected, and an exhaust passage 3 is connected to the turbine side of the turbocharger 1. An air cleaner 4 is connected to the upstream end of the intake passage 2, and an intake control valve 5 for adjusting the flow rate of fresh air flowing into the combustion chamber at an appropriate position of the intake passage 2, and a flow passage disconnection in the low rotation and low load operation region. A swirl control valve 6 is provided for reducing the area and increasing the intake flow velocity. Further, at the downstream end of the exhaust passage 3, an oxidation catalyst (hereinafter abbreviated as DOC) 7, a filter (hereinafter abbreviated as DPF) 8 for removing particulate matter such as soot, and the LNC 9 described above, An exhaust gas purification device 10 connected in this order along the flow of exhaust gas is connected.

スワールコントロール弁６と排気通路３における燃焼室の直後との間は、排出ガス再循環（以下、ＥＧＲと略称す）通路１１を介して互いに連結されている。このＥＧＲ通路１１は、切換弁１２を介して分岐されたクーラー通路１１ａとバイパス通路１１ｂとからなり、その合流部に、燃焼室に流入するＥＧＲ量を調節するＥＧＲ制御弁１３が設けられている。   The swirl control valve 6 and the exhaust passage 3 immediately after the combustion chamber are connected to each other via an exhaust gas recirculation (hereinafter abbreviated as EGR) passage 11. The EGR passage 11 includes a cooler passage 11a and a bypass passage 11b branched via a switching valve 12, and an EGR control valve 13 for adjusting the amount of EGR flowing into the combustion chamber is provided at the junction. .

内燃機関Ｅのシリンダヘッドには、その先端を燃焼室に臨ませた燃料噴射弁１４が設けられている。この燃料噴射弁１４は、燃料を所定の高圧状態で蓄えるコモンレール１５に連結され、コモンレール１５には、クランク軸にて駆動されて燃料タンク１６から燃料を汲み上げる燃料ポンプ１７が接続されている。   The cylinder head of the internal combustion engine E is provided with a fuel injection valve 14 with its tip facing the combustion chamber. The fuel injection valve 14 is connected to a common rail 15 that stores fuel in a predetermined high pressure state, and a fuel pump 17 that is driven by a crankshaft and pumps fuel from the fuel tank 16 is connected to the common rail 15.

これらのターボチャージャ１の過給圧可変機構１９、吸気制御弁５、ＥＧＲ通路切換弁１２およびＥＧＲ制御弁１３、燃料噴射弁１４、燃料ポンプ１７・・・等は、電子制御装置（以下、ＥＣＵと略称する）１８からの制御信号によって作動するように構成されている（図２参照）。   These turbocharger 1 supercharging pressure variable mechanism 19, intake control valve 5, EGR passage switching valve 12 and EGR control valve 13, fuel injection valve 14, fuel pump 17... (Referred to as “abbreviated”) 18 (see FIG. 2).

一方、ＥＣＵ１８には、図２に示すように、内燃機関Ｅの所定箇所に配置された吸気弁開度センサ２０、クランク軸回転速度センサ２１、吸気流量センサ２２、過給圧センサ２３、ＥＧＲ弁開度センサ２４、コモンレール圧センサ２５、アクセルペダル操作量センサ２６、Ｏ２センサ２７Ｕ・２７Ｌ、ＮＯＸセンサ２８Ｕ・２８Ｌ、ＬＮＣ温度センサ２９・・・等からの出力信号が入力されている。 On the other hand, as shown in FIG. 2, the ECU 18 includes an intake valve opening sensor 20, a crankshaft rotation speed sensor 21, an intake flow rate sensor 22, a supercharging pressure sensor 23, and an EGR valve disposed at predetermined locations of the internal combustion engine E. Output signals from the opening sensor 24, the common rail pressure sensor 25, the accelerator pedal operation amount sensor 26, the O 2 sensors 27U and 27L, the NO X sensors 28U and 28L, the LNC temperature sensor 29, etc. are input.

ＥＣＵ１８のメモリには、クランク軸回転速度および要求トルク（アクセルペダル操作量）に応じて実験等によって予め求めた最適燃料噴射量をはじめとする各制御対象の制御目標値を設定したマップが格納されており、内燃機関Ｅの負荷状況に応じて最適な燃焼状態が得られるように、各部の制御が行われる。   The memory of the ECU 18 stores a map in which control target values for each control object including the optimum fuel injection amount obtained in advance by experiments or the like according to the crankshaft rotation speed and the required torque (accelerator pedal operation amount) are set. Therefore, each part is controlled so that an optimal combustion state is obtained according to the load state of the internal combustion engine E.

次に本発明によるサルファパージに係わる制御フローについて図３を参照して説明する。   Next, a control flow relating to sulfur purge according to the present invention will be described with reference to FIG.

先ず、ＬＮＣ９のＳ（硫黄分）被毒量を推定すると共に、サルファパージに必要な還元剤量を把握する（ステップ１）。   First, the S (sulfur content) poisoning amount of LNC 9 is estimated, and the amount of reducing agent necessary for sulfur purge is grasped (step 1).

Ｓ被毒量は、図４に示すように、ＮＯＸ浄化率と逆比例の関係にあり、ＮＯＸ浄化率が高いとＳ被毒量は小さく、Ｓ被毒が進行するとＮＯＸ浄化率は低下する。この関係より、ＮＯＸ浄化率の低下度合いからＳ被毒量を推定することができる。ここでＮＯＸ浄化率は、ＬＮＣ９の上流側（入口）と下流側（出口）とのそれぞれに設置した２つのＮＯＸセンサ２８Ｕ・２８Ｌの出力差の比率を求めることで算出できる。そしてサルファパージに必要な還元剤量は、Ｓ被毒量と正比例の関係にあるので（図５）、Ｓ被毒量が分かれば自ずと得られる。なお、ＬＮＣ９のＳ被毒量は、走行距離、運転時間、燃料消費量などからも推定することができる。 S poisoning amount, as shown in FIG. 4, NO have a relation of X purification rate and inversely, the NO X purification rate is higher S poisoning amount is small, S the poisoning progresses NO X purification rate descend. From this relationship, the degree of decrease of the NO X purification rate can be estimated S poisoning amount. Wherein NO X purification rate can be calculated by determining the ratio of the upstream side (inlet) and the downstream two of the NO X sensor 28U · output difference between 28L installed in each of the (exit) of the LNC 9. Since the amount of reducing agent necessary for sulfur purge is directly proportional to the S poisoning amount (FIG. 5), it is naturally obtained if the S poisoning amount is known. Note that the S poisoning amount of the LNC 9 can be estimated from a travel distance, an operation time, a fuel consumption amount, and the like.

次に、Ｓ被毒量推定値が予め設定した規定値を超えたか否かを判断する（ステップ２）。ここでＳ被毒量が規定値を超えていると判断された時は、サルファパージを実行するものとし、ＬＮＣ９の上流側に設置されたＬＮＣ温度センサ２９の出力値により、ＬＮＣ９がサルファパージ実行可能温度以上であるか否かを判断する（ステップ３）。ここでＬＮＣ温度センサ２９の出力値が所定値（例えば摂氏６５０度）に達していなければ、昇温制御を行う（ステップ４）。   Next, it is determined whether or not the estimated amount of S poisoning exceeds a preset specified value (step 2). When it is determined that the sulfur poisoning amount exceeds the specified value, sulfur purge is executed, and the LNC 9 executes sulfur purge according to the output value of the LNC temperature sensor 29 installed on the upstream side of the LNC 9. It is determined whether or not the temperature is higher than the possible temperature (step 3). If the output value of the LNC temperature sensor 29 does not reach a predetermined value (for example, 650 degrees Celsius), temperature increase control is performed (step 4).

昇温制御は、メイン噴射タイミングの遅角、ポスト噴射の増量、吸入空気量の減量などを適宜に併用することにより、サルファパージが可能なＬＮＣ温度を維持するようにフィードバック制御する。   In the temperature rise control, feedback control is performed so as to maintain the LNC temperature at which sulfur purge can be performed by appropriately using a delay of the main injection timing, an increase in the post injection, a decrease in the intake air amount, and the like.

ＬＮＣ９がサルファパージ可能な温度に達していたならば、サルファパージのための排気Ａ／Ｆリッチ化制御を実行する（ステップ５）。この排気Ａ／Ｆリッチ化制御は、基本的には昇温制御と同様であるが、昇温制御よりもポスト噴射量を更に増加させ、且つ吸入空気量を更に減量することにより行う。   If the temperature of the LNC 9 has reached the temperature at which sulfur purge is possible, exhaust A / F enrichment control for sulfur purge is executed (step 5). This exhaust A / F enrichment control is basically the same as the temperature rise control, but is performed by further increasing the post injection amount and further reducing the intake air amount than the temperature rise control.

このようなＬＮＣ９がサルファパージ可能なリッチ環境にある時に、ＬＮＣ９の上流側と下流側とのそれぞれに設置した２つのＯ２センサ２７Ｕ・２７Ｌの出力を監視し、上流側Ｏ２センサ２７Ｕの出力とある所定の基準値（例えば理論空燃比＝ストイキ）との差の積算値に基づいてＬＮＣ９への還元剤供給量を推定するか（ステップ６）、あるいは、上流側Ｏ２センサ２７Ｕと下流側Ｏ２センサ２７Ｌとの出力差の積算値に基づいてＬＮＣ９での還元剤消費量を推定する（ステップ７）。そしてこれらの積算値を監視してステップ１で求めた還元剤必要量と比較し（ステップ８、９）、積算値が還元剤必要量に達したことが判別されたならば、サルファパージ終了判定信号を出力する（ステップ１０）。 When the LNC 9 is in a rich environment capable of sulfur purge, the outputs of the two O 2 sensors 27U and 27L installed on the upstream side and the downstream side of the LNC 9 are monitored, and the outputs of the upstream O 2 sensor 27U are monitored. Whether the reducing agent supply amount to the LNC 9 is estimated based on the integrated value of the difference from a predetermined reference value (for example, stoichiometric air-fuel ratio = stoichiometric) (step 6), or the upstream O 2 sensor 27U and the downstream side Based on the integrated value of the output difference from the O 2 sensor 27L, the amount of reducing agent consumed in the LNC 9 is estimated (step 7). Then, these integrated values are monitored and compared with the reducing agent required amount obtained in step 1 (steps 8 and 9). If it is determined that the integrated value has reached the reducing agent required amount, the sulfur purge end determination is made. A signal is output (step 10).

具体的には、排気中の酸素濃度から排気Ａ／Ｆが分かり、上流側Ｏ２センサ２７Ｕから得られた排気Ａ／Ｆと理論空燃比（ストイキ）との差の積算値からＬＮＣ９への還元剤供給量が分かり、上流側Ｏ２センサ２７Ｕと下流側Ｏ２センサ２７Ｌとの出力差の積算値からＬＮＣ９での還元剤消費量が分かるので、サルファパージ処理中の２つのＯ２センサの出力を監視すれば、サルファパージ中に供給、または消費された還元剤量を推定することができる。つまり、あるＳ被毒量をサルファパージするのに必要な還元剤量を予め求めておけば、供給量あるいは消費量が必要量に到達した時点をもってサルファパージの終了時期を判断することができる。 Specifically, the exhaust A / F is known from the oxygen concentration in the exhaust, and the reduction value to the LNC 9 is calculated from the integrated value of the difference between the exhaust A / F obtained from the upstream O 2 sensor 27U and the stoichiometric air-fuel ratio (stoichiometric). Since the agent supply amount is known and the reducing agent consumption amount in the LNC 9 is known from the integrated value of the output difference between the upstream O 2 sensor 27U and the downstream O 2 sensor 27L, the outputs of the two O 2 sensors during the sulfur purge process Is monitored, the amount of reducing agent supplied or consumed during sulfur purge can be estimated. That is, if the amount of reducing agent necessary for sulfur purging a certain amount of sulfur is obtained in advance, the end time of sulfur purging can be determined at the time when the supply amount or consumption amount reaches the necessary amount.

なお、還元剤の供給量と消費量とのいずれか一方だけでもサルファパージの終了時期を判断できるが、両者を互いに比較することでより一層精度を高めることができる。   Note that the end time of sulfur purge can be determined by only one of the supply amount and consumption amount of the reducing agent, but the accuracy can be further improved by comparing the two with each other.

図６は、サルファパージ実行中のＬＮＣ９の上流側と下流側とのそれぞれに設置した２つのＯ２センサ２７Ｕ・２７Ｌの出力差とＳ濃度との推移を示したものである。サルファパージ初期は、２つのＯ２センサの出力差が大きく、ＳＯＸ濃度あるいはＨ２Ｓ濃度の低下、つまりサルファパージの進行と共に２つのＯ２センサの出力差が減少している。このことから、２つのＯ２センサの出力差からＳの放出量を推定することが可能なことが分かる。 FIG. 6 shows the transition of the output difference and the S concentration of the two O 2 sensors 27U and 27L installed on the upstream side and the downstream side of the LNC 9 during execution of sulfur purge. Sulfur purge initial, output difference between the two O 2 sensors is large, reduction of SO X concentration or the concentration of H 2 S, that is, the output difference between the two O 2 sensors with the progress of sulfur purge is reduced. From this, it can be seen that the amount of S released can be estimated from the output difference between the two O 2 sensors.

サルファパージは、図７に示すように、ＬＮＣ９の温度が高い方が、その処理に要する時間が減少する傾向にある。これはＬＮＣ９における還元剤としてのＣＯ消費率との相関があり、図８に示すように、ＬＮＣ温度が高いほどＣＯ消費率が高いことを表している。即ち、単に上流側Ｏ２センサ２７Ｕから得られた排気Ａ／Ｆと理論空燃比（ストイキ）との差の積算値から判断するのみならず、この積算値にＬＮＣ温度から求めたＣＯ消費率を乗ずることにより、還元剤消費量を正確に把握することができ、ＬＮＣのサルファパージ終了時期の判断精度をより一層高めることが可能となる。 As shown in FIG. 7, the sulfur purge tends to reduce the time required for the process when the temperature of the LNC 9 is higher. This has a correlation with the CO consumption rate as the reducing agent in LNC9, and as shown in FIG. 8, the higher the LNC temperature, the higher the CO consumption rate. That is, it is not only determined from the integrated value of the difference between the exhaust A / F obtained from the upstream O 2 sensor 27U and the stoichiometric air-fuel ratio (stoichiometric), but the CO consumption rate obtained from the LNC temperature is added to this integrated value. By multiplying, it is possible to accurately grasp the amount of reducing agent consumed, and it is possible to further increase the accuracy of determining the LNC sulfur purge end timing.

更に、空間速度ＳＶが高いほど還元剤の供給量が高まるので、空間速度ＳＶを考慮することにより、還元剤の供給量（消費量）を正確に把握することができ、ＬＮＣのサルファパージ終了時期の判断をより一層的確に行うことができる。ここで空間速度ＳＶとは、還元剤供給容積速度の反応器容積に対する割合であり、
（吸入空気量＋燃料供給量）／ＬＮＣ容積
で与えられる。なお、吸入空気量は吸気流量センサ２２の出力値であり、燃料供給量は、主にアクセルペダル操作量センサ２６の出力に対するＥＣＵ１８からの燃料噴射弁１３の制御量から求めた推定値であり、ＬＮＣ容積は、予め実測して求めた値である。 Furthermore, since the supply amount of the reducing agent increases as the space velocity SV increases, the supply amount (consumption amount) of the reducing agent can be accurately grasped by considering the space velocity SV. Can be determined more accurately. Here, the space velocity SV is a ratio of the reducing agent supply volume velocity to the reactor volume,
(Intake air amount + fuel supply amount) / LNC volume. The intake air amount is an output value of the intake flow rate sensor 22, and the fuel supply amount is an estimated value obtained mainly from the control amount of the fuel injection valve 13 from the ECU 18 with respect to the output of the accelerator pedal operation amount sensor 26. The LNC volume is a value obtained by actual measurement in advance.

図３におけるステップ６の処理において、上流側Ｏ２センサ２７Ｕの出力と理論空燃比との差の積算値に上述したＳＶ値およびＣＯ消費率を乗ずることにより、触媒との接触、反応確率変化の影響による還元剤消費量の変化度合いを考慮することができ、各運転状態に応じた還元剤の量をより一層正確に把握することができる。 In the process of step 6 in FIG. 3, by multiplying the integrated value of the difference between the output of the upstream O 2 sensor 27U and the theoretical air-fuel ratio by the SV value and the CO consumption rate, the contact with the catalyst and the reaction probability change are changed. The degree of change of the reducing agent consumption due to the influence can be taken into account, and the amount of reducing agent corresponding to each operating state can be grasped more accurately.

また図３におけるステップ７の処理においては、２つのＯ２センサ２７Ｕ・２７Ｌの出力差には既にＣＯ消費率の変化が含まれた値となるので、空間速度ＳＶのみを乗じれば良い。 In the process of step 7 in FIG. 3, since the output difference between the two O 2 sensors 27U and 27L already has a value including the change in the CO consumption rate, it is sufficient to multiply only the space velocity SV.

このように、ＣＯ消費率並びにＳＶ値を加味するものとすれば、上流側Ｏ２センサ２７Ｕの出力と理論空燃比との差の積算値だけでも充分に正確な還元剤の消費量を把握し得るので、Ｏ２センサを１本設ければ済むことになり、製造コスト並びに設置スペースの増大を回避する上に寄与することができる。 As described above, if the CO consumption rate and the SV value are taken into account, a sufficiently accurate reducing agent consumption can be grasped only by the integrated value of the difference between the output of the upstream O 2 sensor 27U and the theoretical air-fuel ratio. Therefore, only one O 2 sensor needs to be provided, which can contribute to avoiding an increase in manufacturing cost and installation space.

本発明が適用される内燃機関の全体構成図である。1 is an overall configuration diagram of an internal combustion engine to which the present invention is applied. 本発明が適用される制御装置のブロック図である。It is a block diagram of a control device to which the present invention is applied. 本発明による制御フロー図である。It is a control flow figure by this invention. Ｓ被毒量とＮＯＸ浄化率との関係を示す線図である。S is a graph showing the relationship between the poisoning amount and NO X purification rate. Ｓ被毒量とサルファパージに要する還元剤量との関係を示す線図である。It is a diagram which shows the relationship between S poison amount and the amount of reducing agents required for sulfur purge. ２つのＯ２センサの出力差とＳ濃度との推移を示す線図である。Is a diagram showing the transition between the two O 2 output difference and S concentration sensor. サルファパージ速度とＬＮＣ温度との関係を示す線図である。It is a diagram which shows the relationship between a sulfur purge speed | rate and LNC temperature. ＣＯ消費率とＬＮＣ温度との関係を示す線図である。It is a diagram which shows the relationship between CO consumption rate and LNC temperature.

符号の説明Explanation of symbols

３ 排気通路
９ ＬＮＣ
１８ ＥＣＵ
２７Ｕ・２７Ｌ Ｏ２センサ 3 Exhaust passage 9 LNC
18 ECU
27U / 27L O 2 sensor

Claims (6)

排気通路に設けられたＮＯＸ触媒に吸着された硫黄分を除去するための処理手段を有する内燃機関の制御装置であって、
前記ＮＯＸ触媒の上流側の空燃比に対応する値を検出する上流側空燃比検出手段を有し、
該上流側空燃比検出手段の検出値を硫黄分除去処理の終了時期の判断に含ませることを特徴とする内燃機関の制御装置。 A control apparatus for an internal combustion engine having a processing means for removing the sulfur adsorbed to the NO X catalyst provided in an exhaust passage,
Upstream air-fuel ratio detection means for detecting a value corresponding to the air-fuel ratio upstream of the NO X catalyst;
A control device for an internal combustion engine, characterized in that the detection value of the upstream air-fuel ratio detection means is included in the determination of the end time of the sulfur content removal process. 前記上流側空燃比検出手段の検出値と所定の基準値との差の値を積算する積算手段を有し、
該積算手段の積算値を硫黄分除去処理の終了時期の判断に含ませることを特徴とする請求項１に記載の内燃機関の制御装置。 Integrating means for integrating the difference value between the detection value of the upstream air-fuel ratio detection means and a predetermined reference value;
2. The control apparatus for an internal combustion engine according to claim 1, wherein the integrated value of the integrating means is included in the determination of the end time of the sulfur content removing process. 前記ＮＯＸ触媒におけるＣＯ消費率に対応する値を検出するＣＯ消費率検出手段を有し、該ＣＯ消費率検出手段の検出値を硫黄分除去処理の終了時期の判断に含ませることを特徴とする請求項１に記載の内燃機関の制御装置。 And characterized in that contained in the NO has a CO consumption rate detector for detecting a value corresponding to the CO consumption rate in the X catalyst, end timing of the judgment of the sulfur removal process the detection value of the CO consumption rate detector The control device for an internal combustion engine according to claim 1. 排気通路に設けられたＮＯＸ触媒に吸着された硫黄分を除去するための処理手段を有する内燃機関の制御装置であって、
前記ＮＯＸ触媒の上流側の空燃比に対応する値を検出する上流側空燃比検出手段と、
前記ＮＯＸ触媒の下流側の空燃比に対応する値を検出する下流側空燃比検出手段とを有し、
前記上流側空燃比検出手段と前記下流側空燃比検出手段との検出値を硫黄分除去処理の終了時期の判断に含ませることを特徴とする内燃機関の制御装置。 A control apparatus for an internal combustion engine having a processing means for removing the sulfur adsorbed to the NO X catalyst provided in an exhaust passage,
An upstream side air-fuel ratio detecting means for detecting a value corresponding to the air-fuel ratio of the upstream side of the NO X catalyst,
And a downstream air-fuel ratio detecting means for detecting a value corresponding to the air-fuel ratio on the downstream side of the NO X catalyst,
A control apparatus for an internal combustion engine, wherein detected values of the upstream air-fuel ratio detection means and the downstream air-fuel ratio detection means are included in the determination of the end time of the sulfur content removal process. 前記上流側空燃比検出手段の検出値と前記下流側空燃比検出手段の検出値との差の値を積算する積算手段を有し、
該積算手段の積算値を硫黄分除去処理の終了時期の判断に含ませることを特徴とする請求項４に記載の内燃機関の制御装置。 Integrating means for integrating the difference value between the detection value of the upstream air-fuel ratio detection means and the detection value of the downstream air-fuel ratio detection means;
5. The control apparatus for an internal combustion engine according to claim 4, wherein the integrated value of the integrating means is included in the determination of the end time of the sulfur content removal process. 前記ＮＯＸ触媒に流入する排気の空間速度を検出する空間速度検出手段を有し、該空間速度検出手段の検出値を硫黄分除去処理の終了時期の判断に含ませることを特徴とする請求項１乃至５のいずれか１つに記載の内燃機関の制御装置。 Claims, characterized in that said a space velocity detecting means for detecting a space velocity of the exhaust gas flowing to the NO X catalyst, to include detected values of the space velocity detecting means for determining ending timing of the sulfur removal process The control apparatus for an internal combustion engine according to any one of 1 to 5.
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