JP3509482B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Exhaust gas purification device for internal combustion engine

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Publication number
JP3509482B2
JP3509482B2 JP20640997A JP20640997A JP3509482B2 JP 3509482 B2 JP3509482 B2 JP 3509482B2 JP 20640997 A JP20640997 A JP 20640997A JP 20640997 A JP20640997 A JP 20640997A JP 3509482 B2 JP3509482 B2 JP 3509482B2
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JP
Japan
Prior art keywords
fuel
amount
nox
air
fuel ratio
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
JP20640997A
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Japanese (ja)
Other versions
JPH1150894A (en
Inventor
太郎 横井
康二 石原
隆之 戸城
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Nissan Motor Co Ltd
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Nissan Motor Co Ltd
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Priority to JP20640997A priority Critical patent/JP3509482B2/en
Publication of JPH1150894A publication Critical patent/JPH1150894A/en
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Classifications

    • 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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  • Exhaust Gas After Treatment (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【発明の属する技術分野】本発明は、内燃機関の排気浄
化装置に関し、詳しくは、燃焼室内に直接燃料を噴射す
る燃料噴射弁を備えた筒内噴射型の内燃機関において、
ＮＯｘ吸収触媒に吸収されたＮＯｘを還元処理するため
の技術に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to a cylinder injection type internal combustion engine provided with a fuel injection valve for directly injecting fuel into a combustion chamber,
The present invention relates to a technique for reducing NOx absorbed by a NOx absorption catalyst.

【０００２】[0002]

【従来の技術】従来から、排気空燃比がリーンであると
きに排気中のＮＯｘを吸収し、排気空燃比が理論空燃比
（ストイキ）又はリッチであるときに前記吸収したＮＯ
ｘを放出して還元処理するＮＯｘ吸収触媒（ＮＯｘ吸収
型三元触媒）を備えた筒内噴射型の内燃機関が知られて
いる（特開平９−３２６１９号公報参照）。2. Description of the Related Art Conventionally, when the exhaust air-fuel ratio is lean, it absorbs NOx in the exhaust gas, and when the exhaust air-fuel ratio is stoichiometric or rich, the absorbed NOx is absorbed.
A cylinder injection type internal combustion engine equipped with a NOx absorption catalyst (NOx absorption type three-way catalyst) that releases x and performs reduction processing is known (see Japanese Patent Laid-Open No. 9-32619).

【０００３】前記特開平９−３２６１９号公報に開示さ
れるものでは、硫黄が前記ＮＯｘ吸収触媒に付着すると
浄化能力が低下することから、前記硫黄の付着量が所定
量に達したときに、通常の燃料噴射を行いつつ、排気行
程において燃料噴射を行わせ、この排気行程で噴射され
た燃料が排気通路内及びＮＯｘ吸収触媒内で燃焼するこ
とで、前記硫黄が除去されるようにしている。In the method disclosed in Japanese Patent Laid-Open No. 9-32619, when sulfur adheres to the NOx absorption catalyst, the purifying performance decreases, so that when the adhered amount of sulfur reaches a predetermined amount, While the fuel injection is being performed, the fuel is injected in the exhaust stroke, and the fuel injected in the exhaust stroke is burned in the exhaust passage and the NOx absorption catalyst to remove the sulfur.

【０００４】[0004]

【発明が解決しようとする課題】ところで、前記排気行
程噴射では、ＮＯｘ吸収触媒に付着した硫黄の除去が行
えるとしても、ＮＯｘの還元処理は行えないという問題
があった。即ち、前記排気行程での燃料噴射は、リーン
燃焼中に行われ、酸素過剰状態で燃料（ＨＣ）がＮＯｘ
吸収触媒内に流入することになるので、ＮＯｘが脱離さ
れないことになる。また、ＮＯｘ吸収触媒に酸化作用が
あったとしても、触媒の前部で燃料が燃焼して触媒後部
のみが還元雰囲気になるので、上流側に吸収されていた
ＮＯｘは未浄化のまま放置されることになってしまう。In the exhaust stroke injection, however, there is a problem that even if the sulfur adhering to the NOx absorption catalyst can be removed, the NOx reduction process cannot be performed. That is, the fuel injection in the exhaust stroke is performed during lean combustion, and the fuel (HC) is NOx in the excess oxygen state.
Since it will flow into the absorption catalyst, NOx will not be desorbed. Even if the NOx absorption catalyst has an oxidizing effect, the fuel burns in the front part of the catalyst and only the rear part of the catalyst becomes a reducing atmosphere, so the NOx absorbed upstream is left unpurified. I will end up.

【０００５】更に、ＮＯｘ吸収触媒は通常の三元触媒よ
りも耐熱性が低いので、排気行程で噴射した燃料のＮＯ
ｘ吸収触媒内での燃焼によって触媒内の雰囲気を還元雰
囲気にしようとすると、触媒の温度上昇を招いて触媒劣
化が進んでしまうという問題もあった。本発明は上記問
題点に鑑みなされたものであり、燃焼空燃比を変化させ
ることのない膨張〜排気行程での燃料噴射により、ＮＯ
ｘ吸収触媒に吸収されたＮＯｘの浄化を図れ、然も、Ｎ
Ｏｘ吸収触媒の熱劣化を回避できる排気浄化装置を提供
することを目的とする。Furthermore, since the NOx absorption catalyst has lower heat resistance than the ordinary three-way catalyst, NO of the fuel injected in the exhaust stroke is
If the atmosphere in the catalyst is made to be a reducing atmosphere by combustion in the x absorption catalyst, there is a problem that the temperature of the catalyst rises and the catalyst deteriorates. The present invention has been made in view of the above problems, and NO is obtained by fuel injection in the expansion to exhaust stroke without changing the combustion air-fuel ratio.
The NOx absorbed by the x absorption catalyst can be purified, and N
An object of the present invention is to provide an exhaust gas purification device that can avoid thermal deterioration of an Ox absorption catalyst.

【０００６】[0006]

【課題を解決するための手段】そのため請求項１記載の
発明は、内燃機関の燃焼室内に直接燃料を噴射する燃料
噴射弁を備え、理論空燃比よりもリーン空燃比での燃焼
運転を行いうる内燃機関の排気浄化装置であって、排気
空燃比が理論空燃比よりもリーンであるときに排気中の
ＮＯｘを吸収し、排気空燃比が理論空燃比又は理論空燃
比よりもリッチであるときに前記吸収したＮＯｘを放出
して還元処理するＮＯｘ吸収触媒と、該ＮＯｘ吸収触媒
よりも上流側の排気通路に介装される酸化触媒とを備
え、リーン燃焼中に前記燃料噴射弁により膨張〜排気行
程で燃料を噴射させることにより、前記ＮＯｘ吸収触媒
の入口での排気空燃比をリッチにして、前記ＮＯｘ吸収
触媒に吸収されたＮＯｘの還元処理を行うと共に、前記
膨張〜排気行程で噴射される燃料量を、吸入空気量，燃
焼空燃比，ＮＯｘ吸収触媒におけるＮＯｘ吸収量に応じ
て設定する構成とした。Therefore, the invention according to claim 1 is provided with a fuel injection valve for directly injecting fuel into a combustion chamber of an internal combustion engine, and can perform a combustion operation at a lean air-fuel ratio rather than a stoichiometric air-fuel ratio. An exhaust purification device for an internal combustion engine, which absorbs NOx in the exhaust when the exhaust air-fuel ratio is leaner than the theoretical air-fuel ratio, and when the exhaust air-fuel ratio is richer than the theoretical air-fuel ratio or the theoretical air-fuel ratio. An NOx absorption catalyst that releases the absorbed NOx and performs a reduction process, and an oxidation catalyst that is interposed in an exhaust passage on the upstream side of the NOx absorption catalyst, are expanded by the fuel injection valve during lean combustion to exhaust gas. By injecting fuel in the stroke, the exhaust air-fuel ratio at the inlet of the NOx absorption catalyst is made rich, and the NOx absorbed by the NOx absorption catalyst is reduced , and
The amount of fuel injected during the expansion-exhaust stroke is calculated as
Depending on the burnt air-fuel ratio and the NOx absorption amount in the NOx absorption catalyst
The configuration is set as follows.

【０００７】かかる構成によると、膨張〜排気行程で噴
射された燃料は、排気通路にリーン燃焼排気と共に排出
され、まず、酸化触媒に流入する。そして、酸化触媒の
酸化作用によって前記燃料が燃焼することで酸素が消費
され、酸化触媒出口では、排気空燃比がリッチになり、
かかるリッチ空燃比の排気がＮＯｘ吸収触媒に流入し
て、ＮＯｘ吸収触媒におけるＮＯｘの脱離，還元処理が
行われる。また、吸入空気量，燃焼空燃比，ＮＯｘ吸収
量によって、ＮＯｘ吸収触媒内がＮＯｘ還元処理に最適
な雰囲気となるように、膨張〜排気行程での燃料噴射に
おける噴射量が設定される。 According to this structure, the fuel injected during the expansion-exhaust stroke is discharged into the exhaust passage together with the lean combustion exhaust, and first flows into the oxidation catalyst. Then, oxygen is consumed by the combustion of the fuel by the oxidizing action of the oxidation catalyst, the exhaust air-fuel ratio becomes rich at the oxidation catalyst outlet,
Exhaust gas having such a rich air-fuel ratio flows into the NOx absorption catalyst, and NOx desorption and reduction processing in the NOx absorption catalyst is performed. Also, intake air amount, combustion air-fuel ratio, NOx absorption
Depending on the amount, the inside of the NOx absorption catalyst is optimal for NOx reduction processing
For fuel injection during expansion to exhaust stroke to create a perfect atmosphere
Injection amount is set.

【０００８】尚、一般的に酸化触媒（三元触媒でも可）
の耐熱性は、ＮＯｘ吸収触媒よりも高く、膨張〜排気行
程で噴射された燃料の燃焼による酸化触媒の劣化は充分
に小さい。 Generally, an oxidation catalyst (a three-way catalyst is also possible)
Has a higher heat resistance than the NOx absorption catalyst, and deterioration of the oxidation catalyst due to combustion of the fuel injected in the expansion to exhaust stroke is sufficiently small.

【０００９】請求項２記載の発明では、前記吸入空気量
と燃焼空燃比とに基づいて前記酸化触媒における酸化反
応で排気中の酸素を消費する分の燃料量を演算する一
方、前記ＮＯｘ吸収触媒におけるＮＯｘ吸収量に基づい
てＮＯｘを還元処理する分の燃料量を演算し、これらの
合計を膨張〜排気行程で噴射する燃料量とする構成とし
た。According to the second aspect of the present invention, the fuel amount for consuming oxygen in the exhaust gas by the oxidation reaction in the oxidation catalyst is calculated based on the intake air amount and the combustion air-fuel ratio, while the NOx absorption catalyst is calculated. The amount of fuel for reducing NOx is calculated on the basis of the amount of NOx absorbed in the above, and the sum of these is set as the amount of fuel to be injected in the expansion-exhaust stroke.

【００１０】かかる構成によると、吸入空気量と燃焼空
燃比とから排気中の過剰酸素を酸化触媒での燃焼で消費
するための燃料量を判定でき、また、ＮＯｘの還元処理
には、同時に酸化されるＨＣの存在が不可欠であるか
ら、ＮＯｘ吸収量からＮＯｘ還元処理時に必要となる燃
料量を判定でき、前記過剰酸素を消費するための燃料量
と還元処理時に必要となる燃料量との合計を、膨張〜排
気行程において噴射させる。According to this structure, the amount of fuel for consuming excess oxygen in the exhaust gas by combustion in the oxidation catalyst can be determined from the amount of intake air and the combustion air-fuel ratio, and the NOx reduction process is performed simultaneously with oxidation. Since the presence of HC is indispensable, the amount of fuel required for the NOx reduction process can be determined from the NOx absorption amount, and the sum of the amount of fuel for consuming the excess oxygen and the amount of fuel required for the reduction process can be determined. Are injected in the expansion-exhaust stroke.

【００１１】請求項３記載の発明は、内燃機関の燃焼室
内に直接燃料を噴射する燃料噴射弁を備え、理論空燃比
よりもリーン空燃比での燃焼運転を行いうる内燃機関の
排気浄化装置であって、図１に示すように構成される。
図１において、ＮＯｘ吸収触媒は、排気空燃比が理論空
燃比よりもリーンであるときに排気中のＮＯｘを吸収
し、排気空燃比が理論空燃比又は理論空燃比よりもリッ
チであるときに前記吸収したＮＯｘを放出して還元処理
する触媒であり、酸化触媒は、前記ＮＯｘ吸収触媒より
も上流側の排気通路に介装される。According to a third aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, comprising a fuel injection valve for directly injecting fuel into a combustion chamber of the internal combustion engine, and capable of performing a combustion operation at a lean air-fuel ratio rather than a stoichiometric air-fuel ratio. Therefore, the configuration is as shown in FIG.
In FIG. 1, the NOx absorption catalyst absorbs NOx in the exhaust when the exhaust air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and when the exhaust air-fuel ratio is the stoichiometric air-fuel ratio or is richer than the stoichiometric air-fuel ratio, The oxidation catalyst is a catalyst that releases the absorbed NOx and performs a reduction process, and the oxidation catalyst is provided in the exhaust passage on the upstream side of the NOx absorption catalyst.

【００１２】一方、ＮＯｘ吸収量予測手段は、前記ＮＯ
ｘ吸収触媒におけるＮＯｘの吸収量を予測する。そし
て、排気行程噴射制御手段は、リーン燃焼運転中に前記
ＮＯｘ吸収量予測手段で予測されるＮＯｘ吸収量が所定
値以上になったときに、前記燃料噴射弁により膨張〜排
気行程中に燃料噴射を所定期間だけ行わせる。On the other hand, the NOx absorption amount predicting means is the NOx
Predict the amount of NOx absorbed by the x absorption catalyst. Then, the exhaust stroke injection control means causes the fuel injection valve to perform fuel injection during expansion to the exhaust stroke when the NOx absorption amount predicted by the NOx absorption amount prediction means during the lean combustion operation becomes a predetermined value or more. Is performed for a predetermined period.

【００１３】ここで、排気行程噴射量演算手段は、前記
排気行程噴射制御手段による燃料噴射量を、機関の吸入
空気量，燃焼空燃比及び前記ＮＯｘ吸収量予測手段で予
測されたＮＯｘ吸収量に基づいて演算する。かかる構成
によると、リーン燃焼中に、ＮＯｘ吸収触媒に吸収され
たＮＯｘ量が所定値以上になると、リーン燃焼混合気形
成のための通常の燃料噴射（吸気行程噴射又は圧縮行程
噴射）の他、膨張〜排気行程でも燃料噴射を行わせる。Here, the exhaust stroke injection quantity computing means sets the fuel injection quantity by the exhaust stroke injection control means to the intake air quantity of the engine, the combustion air-fuel ratio, and the NOx absorption quantity predicted by the NOx absorption quantity prediction means. Calculate based on According to this configuration, when the NOx amount absorbed by the NOx absorption catalyst becomes equal to or larger than the predetermined value during lean combustion, in addition to the normal fuel injection (intake stroke injection or compression stroke injection) for forming the lean combustion mixture, Fuel is injected even during the expansion-exhaust stroke.

【００１４】膨張行程又は排気行程で燃焼室内に噴射さ
れた燃料は、燃焼排気と共に燃焼室から排出されて酸化
触媒に流入し、ここでの酸化触媒作用によって燃焼して
リーン燃焼による過剰酸素を消費する。酸化触媒で燃焼
せずに残った燃料（ＨＣ）は、リーン排気と共にＮＯｘ
吸収触媒に流入し、ＮＯｘ吸収触媒に吸収されていたＮ
Ｏｘは、リーン排気の下で脱離し、燃料（ＨＣ）の酸化
と同時に還元処理される。The fuel injected into the combustion chamber in the expansion stroke or exhaust stroke is discharged from the combustion chamber together with the combustion exhaust gas and flows into the oxidation catalyst, where it is burned by the oxidation catalyst action and consumes excess oxygen due to lean combustion. To do. The fuel (HC) remaining without being burned by the oxidation catalyst is NOx along with lean exhaust.
N that had flowed into the absorption catalyst and was absorbed by the NOx absorption catalyst
Ox is desorbed under lean exhaust gas and is reduced at the same time as the fuel (HC) is oxidized.

【００１５】前記膨張〜排気行程での燃料噴射量は、過
剰酸素量を示す機関の吸入空気量及び燃焼空燃比と、還
元処理するＮＯｘ吸収量とに基づいて演算される。請求
項４記載の発明では、前記排気行程噴射量演算手段が、
前記吸入空気量と燃焼空燃比とに基づいて前記酸化触媒
における酸化反応で排気中の酸素を消費する分の燃料量
を演算する一方、前記ＮＯｘ吸収触媒におけるＮＯｘ吸
収量に基づいてＮＯｘを還元処理する分の燃料量を演算
し、これらの合計を膨張〜排気行程で噴射する燃料量と
して演算する構成とした。The fuel injection amount in the expansion-exhaust stroke is calculated on the basis of the intake air amount and combustion air-fuel ratio of the engine, which indicates the excess oxygen amount, and the NOx absorption amount to be reduced. In the invention according to claim 4 , the exhaust stroke injection amount calculation means is
Based on the intake air amount and the combustion air-fuel ratio, the fuel amount for consuming oxygen in the exhaust gas by the oxidation reaction in the oxidation catalyst is calculated, while the NOx reduction process is performed based on the NOx absorption amount in the NOx absorption catalyst. The fuel amount is calculated and the sum of these is calculated as the fuel amount injected during the expansion-exhaust stroke.

【００１６】かかる構成によると、吸入空気量と燃焼空
燃比とから過剰酸素を酸化触媒での燃焼で消費するため
の燃料量を演算し、また、ＮＯｘの還元処理には、同時
に酸化されるＨＣが必要であるから、ＮＯｘ吸収量から
ＮＯｘ還元処理時に必要となる燃料量（酸化処理される
燃料量）を演算し、これらの合計を膨張〜排気行程にお
いて噴射させる燃料量とする。According to such a configuration, the amount of fuel for consuming excess oxygen by combustion in the oxidation catalyst is calculated from the amount of intake air and the combustion air-fuel ratio, and the HC which is simultaneously oxidized in the NOx reduction process is calculated. Therefore, the fuel amount required for the NOx reduction process (fuel amount to be oxidized) is calculated from the NOx absorption amount, and the sum of these is set as the fuel amount to be injected in the expansion-exhaust stroke.

【００１７】請求項５記載の発明では、前記排気行程噴
射量演算手段が、機関の吸入空気量と燃焼空燃比とに基
づいて、理論空燃比燃焼時相当の燃料噴射量とそのとき
の燃焼空燃比での燃料噴射量との差分を演算し、この差
分を前記酸化触媒における酸化反応で排気中の酸素を消
費する分の燃料量とする構成とした。かかる構成による
と、理論空燃比燃焼を行わせるときの燃料噴射量から、
そのときのリーン燃焼での燃料噴射量との差分が、過剰
酸素を生じさせる燃料の不足分となるから、前記差分を
膨張〜排気行程で噴射させて、一旦過剰酸素として排気
通路に排出された酸素を、膨張〜排気行程噴射で噴射さ
れた燃料の酸化触媒での燃焼で消費させる。According to the fifth aspect of the invention, the exhaust stroke injection amount calculation means is based on the intake air amount of the engine and the combustion air-fuel ratio, and the fuel injection amount corresponding to the stoichiometric air-fuel ratio combustion and the combustion air at that time. A difference from the fuel injection amount at the fuel ratio is calculated, and this difference is set as a fuel amount for consuming oxygen in the exhaust gas by the oxidation reaction in the oxidation catalyst. According to such a configuration, from the fuel injection amount when performing stoichiometric air-fuel ratio combustion,
Since the difference from the fuel injection amount in lean combustion at that time is the shortage of the fuel that causes excess oxygen, the difference is injected in the expansion-exhaust stroke and once discharged as excess oxygen to the exhaust passage. Oxygen is consumed by combustion of the fuel injected in the expansion to exhaust stroke injection in the oxidation catalyst.

【００１８】請求項６記載の発明では、前記酸化触媒の
下流側でかつ前記ＮＯｘ吸収触媒の上流側の排気通路に
おいて排気空燃比を検出する排気空燃比検出手段と、該
排気空燃比検出手段で検出される排気空燃比に基づいて
前記排気行程噴射制御手段による膨張〜排気行程での燃
料噴射量をフィードバック補正する噴射量フィードバッ
ク手段と、を設ける構成とした。According to a sixth aspect of the present invention, there is provided an exhaust air-fuel ratio detecting means for detecting an exhaust air-fuel ratio in an exhaust passage downstream of the oxidation catalyst and upstream of the NOx absorption catalyst, and the exhaust air-fuel ratio detecting means. And an injection quantity feedback means for feedback-correcting the fuel injection quantity from expansion to exhaust stroke by the exhaust stroke injection control means based on the detected exhaust air-fuel ratio.

【００１９】かかる構成によると、膨張〜排気行程で燃
料噴射を行わせてリーン燃焼による過剰酸素の消費を図
るときに、酸化触媒の下流側で排気空燃比を検出して、
過剰酸素が実際に消費されているか否かを確認して、膨
張〜排気行程での噴射における燃料量をフィードバック
補正する。According to this structure, when fuel injection is performed in the expansion to exhaust stroke to consume excess oxygen by lean combustion, the exhaust air-fuel ratio is detected on the downstream side of the oxidation catalyst,
It is confirmed whether or not the excess oxygen is actually consumed, and the fuel amount in the injection from the expansion to the exhaust stroke is feedback-corrected.

【００２０】[0020]

【発明の効果】請求項１記載の発明によると、リーン燃
焼中の膨張〜排気行程での噴射により、ＮＯｘ吸収触媒
内を還元雰囲気としてＮＯｘを脱離・還元処理でき、ま
た、膨張〜排気行程での噴射による燃料は酸化触媒で燃
焼するのでＮＯｘ吸収触媒の熱劣化を回避できると共
に、ＮＯｘ吸収触媒内を還元雰囲気とするための膨張〜
排気行程での噴射量を適切に設定でき、ＮＯｘが不完全
に浄化されたり、排気，燃費が悪化することを防止でき
るという効果がある。 According to the invention described in claim 1, NOx can be desorbed and reduced by using the NOx absorption catalyst as a reducing atmosphere by injection in the expansion-exhaust stroke during lean combustion, and the expansion-exhaust stroke. co the fuel by injection in can avoid thermal degradation of the NOx absorbent catalyst so that combustion in the oxidation catalyst
To expand the NOx absorption catalyst to a reducing atmosphere ~
The injection amount in the exhaust stroke can be set appropriately and NOx is incomplete.
Can prevent the exhaust gas and fuel consumption from deteriorating.
Has the effect of

【００２１】請求項２記載の発明によると、過剰酸素の
消費に必要な燃料量と、還元処理に必要とされる燃料量
とをそれぞれに求めて、これらの合計を膨張〜排気行程
において噴射させることで、過剰酸素状態を確実に解消
し、かつ、脱離されたＮＯｘの還元処理を確実に行わせ
ることができるという効果がある。 According to the second aspect of the present invention, the amount of fuel required for consumption of excess oxygen and the amount of fuel required for reduction treatment are respectively obtained, and the sum of these is injected in the expansion-exhaust stroke. As a result, there is an effect that the excess oxygen state can be reliably eliminated, and the deoxidized NOx can be reduced.

【００２２】請求項３記載の発明によると、ＮＯｘ吸収
触媒に吸収されたＮＯｘが所定値以上になったときに、
リーン燃焼運転のまま、膨張〜排気行程での燃料噴射に
よってＮＯｘ吸収触媒内を還元雰囲気にしてＮＯｘを浄
化でき、かつ、リーン燃焼による酸素過剰状態を、上流
側の酸化触媒での燃焼によって解消するので、ＮＯｘ吸
収触媒の熱劣化を回避できるという効果がある。According to the third aspect of the invention, when the NOx absorbed by the NOx absorption catalyst exceeds a predetermined value,
With the lean combustion operation as it is, NOx can be purified by forming a reducing atmosphere in the NOx absorption catalyst by fuel injection in the expansion to exhaust stroke, and the excess oxygen state due to lean combustion is eliminated by combustion in the upstream oxidation catalyst. Therefore, there is an effect that thermal deterioration of the NOx absorption catalyst can be avoided.

【００２３】請求項４記載の発明によると、酸化触媒で
の燃焼による過剰酸素の消費に必要な燃料量と、ＮＯｘ
吸収触媒における還元処理に必要とされる燃料量とを膨
張〜排気行程において噴射させることで、過剰酸素状態
を確実に解消してＮＯｘを脱離させ、かつ、脱離された
ＮＯｘの還元処理を確実に行わせることができるという
効果がある。According to the invention described in claim 4 , the amount of fuel required for consumption of excess oxygen by combustion in the oxidation catalyst and NOx
By injecting the amount of fuel required for the reduction process in the absorption catalyst in the expansion-exhaust stroke, the excess oxygen state is reliably eliminated to desorb NOx, and the deoxidized NOx is reduced. The effect is that it can be performed reliably.

【００２４】請求項５記載の発明によると、リーン燃焼
状態における酸素過剰状態を、酸化触媒における燃料の
燃焼によって解消するための燃料量を、簡便かつ確実に
求めることができるという効果がある。請求項６記載の
発明によると、酸化触媒における燃料の燃焼によって過
剰酸素状態を解消し得る燃料量を、過不足なく膨張〜排
気行程において噴射させることができるという効果があ
る。According to the fifth aspect of the present invention, there is an effect that the amount of fuel for eliminating the oxygen excess state in the lean combustion state by the combustion of the fuel in the oxidation catalyst can be simply and surely obtained. According to the invention described in claim 6, there is an effect that the fuel amount capable of eliminating the excess oxygen state by the combustion of the fuel in the oxidation catalyst can be injected in the expansion-exhaust stroke without excess or deficiency.

【００２５】[0025]

【発明の実施の形態】以下に本発明の実施の形態を説明
する。図２は、実施の形態における内燃機関のシステム
構成を示す図であり、内燃機関１には、エアクリーナ２
を通過した空気がスロットル弁３で調量されて吸引され
る。機関１の各気筒には、燃焼室内に直接燃料を噴射す
る燃料噴射弁４がそれぞれ設けられており、該燃料噴射
弁４による燃料噴射によって燃焼室内に混合気が形成さ
れる。BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 2 is a diagram showing a system configuration of an internal combustion engine according to the embodiment. The internal combustion engine 1 includes an air cleaner 2
The air that has passed through is throttled by the throttle valve 3 and sucked. Each cylinder of the engine 1 is provided with a fuel injection valve 4 that directly injects fuel into the combustion chamber, and the fuel injection by the fuel injection valve 4 forms a mixture in the combustion chamber.

【００２６】ここで、吸気行程での燃料噴射による均質
リーン燃焼運転及び／又は圧縮行程での燃料噴射による
成層リーン燃焼運転が行われるようになっており、マイ
クロコンピュータを内蔵したコントロールユニット５は
目標空燃比の混合気を形成させるべく燃料噴射弁４の燃
料噴射量及び噴射タイミングを制御する。前記燃料噴射
弁４からの燃料噴射で形成された混合気は、点火プラグ
６による火花点火によって着火燃焼し、燃焼排気は、上
流側から順に酸化触媒７，ＮＯｘ吸収触媒８が介装され
た排気通路９を介して大気中に排出される。Here, a homogeneous lean combustion operation by fuel injection in the intake stroke and / or a stratified lean combustion operation by fuel injection in the compression stroke are performed, and the control unit 5 incorporating a microcomputer is the target. The fuel injection amount and injection timing of the fuel injection valve 4 are controlled to form an air-fuel mixture. The air-fuel mixture formed by the fuel injection from the fuel injection valve 4 is ignited and combusted by spark ignition by the spark plug 6, and the combustion exhaust gas is an exhaust gas in which an oxidation catalyst 7 and a NOx absorption catalyst 8 are interposed in order from the upstream side. It is discharged into the atmosphere via the passage 9.

【００２７】前記酸化触媒７は、酸化作用のある触媒で
あり、三元触媒であっても良い。また、前記ＮＯｘ吸収
触媒８は、排気空燃比が理論空燃比よりもリーンである
ときに排気中のＮＯｘを吸収し、排気空燃比が理論空燃
比又は理論空燃比よりもリッチであるときに前記吸収し
たＮＯｘを放出して還元処理するＮＯｘ吸収型三元触媒
である。The oxidation catalyst 7 is a catalyst having an oxidizing action, and may be a three-way catalyst. Further, the NOx absorption catalyst 8 absorbs NOx in the exhaust when the exhaust air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and when the exhaust air-fuel ratio is the stoichiometric air-fuel ratio or is richer than the stoichiometric air-fuel ratio, It is a NOx absorption type three-way catalyst that releases absorbed NOx and performs reduction processing.

【００２８】前記ＮＯｘ吸収触媒８におけるＮＯｘの吸
放出作用を、担体上に白金Ｐｔ及びバリウムＢａを担持
させた場合を例として説明する。尚、他の貴金属，アル
カリ金属，アルカリ土類，希土類を用いる構成の場合も
同様である。排気空燃比がリーンであるときには、図３
（Ａ）に示すように、排気中の酸素Ｏ2 が、Ｏ2-形で白
金Ｐｔの表面に付着する。一方、排気中のＮＯは、白金
Ｐｔの表面上でＯ2-と反応し、ＮＯ2 となる（２ＮＯ＋
Ｏ2 →２ＮＯ2 ）。次いで、生成されたＮＯ2 の一部は
白金Ｐｔ上で更に酸化されつつ、硝酸イオンＮＯ3-の形
で吸収物質（バリウム) 内に吸収される。The action of absorbing and releasing NOx in the NOx absorption catalyst 8 will be described by taking as an example the case where platinum Pt and barium Ba are carried on a carrier. The same applies to the case of using other noble metals, alkali metals, alkaline earths, and rare earths. When the exhaust air-fuel ratio is lean, FIG.
As shown in (A), oxygen O 2 in the exhaust gas adheres to the surface of platinum Pt in the O 2− form. On the other hand, NO in the exhaust gas reacts with O 2− on the surface of platinum Pt to become NO 2 (2NO +
O 2 → 2NO 2 ). Then, a part of the generated NO 2 is further oxidized on the platinum Pt and is absorbed in the absorbing substance (barium) in the form of nitrate ion NO 3 − .

【００２９】一方、ストイキ燃焼又はリッチ燃焼への切
り換えによって排気中の酸素濃度が低下してＮＯ2 の生
成量が低下すると、反応が逆方向（ＮＯ3-→ＮＯ2 ）に
進み、吸収物質内の硝酸イオンＮＯ3-がＮＯ2 の形で吸
収物質から放出される。放出されたＮＯ2 は、ＣＯ又は
ＨＣと反応してＮ2 に還元処理される。前記コントロー
ルユニット５には、燃料噴射制御のために各種センサか
らの検出信号が入力される。On the other hand, when the oxygen concentration in the exhaust gas is reduced by the switching to stoichiometric combustion or rich combustion to reduce the amount of NO 2 produced, the reaction proceeds in the reverse direction (NO 3 → NO 2 ) and Nitrate ion NO 3-of is released from the absorbent in the form of NO 2 . The released NO 2 reacts with CO or HC and is reduced to N 2 . Detection signals from various sensors are input to the control unit 5 for fuel injection control.

【００３０】前記各種センサとしては、機関１の吸入空
気流量Ｑａを検出するエアフローメータ10，スロットル
弁３の開度ＴＶＯを検出するスロットルセンサ11，機関
１の冷却水温度ＴＷを検出する水温センサ12，クランク
角を検出するクランク角センサ13，前記酸化触媒７の上
流側の排気通路９に介装されて排気中の酸素濃度を検出
する酸素センサ14などが設けられている。尚、前記クラ
ンク角センサ13からの検出信号に基づいて機関回転数Ｎ
ｅ（rpm)が算出される。As the various sensors, an air flow meter 10 for detecting the intake air flow rate Qa of the engine 1, a throttle sensor 11 for detecting the opening TVO of the throttle valve 3, and a water temperature sensor 12 for detecting the cooling water temperature TW of the engine 1. A crank angle sensor 13 that detects a crank angle, an oxygen sensor 14 that is installed in the exhaust passage 9 on the upstream side of the oxidation catalyst 7 and that detects the oxygen concentration in the exhaust gas, and the like are provided. Based on the detection signal from the crank angle sensor 13, the engine speed N
e (rpm) is calculated.

【００３１】そして、コントロールユニット５は、図４
の制御ブロック図に示すようにして、燃料噴射弁４によ
る燃料噴射を制御する。リーン・ストイキ切り替え手段
Ａは、燃焼空燃比を、リーンとストイキ（理論空燃比）
とに切り替え、該切り替えに応じてストイキ空燃比制御
手段Ｂ又はリーン空燃比制御手段Ｃが、前記燃料噴射弁
４による燃料噴射量を制御して燃焼混合気を形成する。The control unit 5 is shown in FIG.
The fuel injection by the fuel injection valve 4 is controlled as shown in the control block diagram of FIG. The lean / stoichi switching means A sets the combustion air-fuel ratio to lean and stoichiometric (theoretical air-fuel ratio).
And the stoichiometric air-fuel ratio control means B or the lean air-fuel ratio control means C controls the fuel injection amount by the fuel injection valve 4 in accordance with the switching to form a combustion mixture.

【００３２】一方、リーン空燃比制御手段Ｃにより燃料
噴射が制御されるリーン燃焼運転時には、ＮＯｘ吸収量
予測手段Ｄが前記ＮＯｘ吸収触媒８に対するＮＯｘの吸
収量を予測し、該予測結果に基づいて２次噴射許可手段
Ｅが、２次噴射（膨張〜排気行程噴射）の許可判断を下
し、噴射量算出手段Ｆ（排気行程噴射制御手段，排気行
程噴射量演算手段）は、前記２次噴射（膨張〜排気行程
噴射）における噴射量を算出して、通常の燃料噴射とは
別に、膨張〜排気行程において燃料噴射弁４による燃料
噴射を行わせる。On the other hand, during lean combustion operation in which fuel injection is controlled by the lean air-fuel ratio control means C, the NOx absorption amount prediction means D predicts the amount of NOx absorbed by the NOx absorption catalyst 8, and based on the prediction result. The secondary injection permission means E makes a determination of permission of secondary injection (expansion to exhaust stroke injection), and the injection amount calculation means F (exhaust stroke injection control means, exhaust stroke injection amount calculation means) uses the secondary injection. The injection amount in (expansion-exhaust stroke injection) is calculated, and fuel injection is performed by the fuel injection valve 4 in the expansion-exhaust stroke in addition to normal fuel injection.

【００３３】次に図５〜図10のフローチャートに従って
図４に示される各手段を詳細に説明する。図５のフロー
チャートは、リーン燃焼の許可判断を行うルーチン（リ
ーン・ストイキ切り替え手段Ａ）を示し、まず、ステッ
プ１（図中にはＳ１と記してある。以下同様）では、機
関回転数ＮｅがスライスレベルＳＬＮＥ未満であるか否
かを判別し、スライスレベルＳＬＮＥ未満であるときに
はステップ２へ進む。Next, each means shown in FIG. 4 will be described in detail with reference to the flowcharts of FIGS. The flowchart in FIG. 5 shows a routine (lean / stoichiometric switching means A) for making a lean burn permission determination. First, in step 1 (denoted as S1 in the figure, the same applies hereinafter), the engine speed Ne is It is determined whether the slice level is lower than SLNE. If the slice level is lower than SLNE, the process proceeds to step 2.

【００３４】ステップ２では、機関負荷がスライスレベ
ルＳＬＴＰ未満であるか否かを判別する。ここで、機関
負荷は、吸入空気流量Ｑａと機関回転数Ｎｅとに基づい
て演算される理論空燃比相当の基本噴射量Ｔｐ（シリン
ダ吸入空気量）で代表させることができる。ステップ２
で、機関負荷がスライスレベルＳＬＴＰ未満であると判
別されたときには、更に、ステップ３へ進み、スロット
ル開度変化率ΔＴＶＯがスライスレベルＳＬＴＶＯ未満
であるか否かを判別することで、スロットル弁３の開度
が安定している定常状態であるか否かを判別する。In step 2, it is judged whether the engine load is less than the slice level SLTP. Here, the engine load can be represented by a basic injection amount Tp (cylinder intake air amount) corresponding to the theoretical air-fuel ratio calculated based on the intake air flow rate Qa and the engine speed Ne. Step two
When it is determined that the engine load is less than the slice level SLTP, the process further proceeds to step 3, and it is determined whether the throttle opening change rate ΔTVO is less than the slice level SLTVO. It is determined whether or not the opening is stable and in a steady state.

【００３５】スロットル開度変化率ΔＴＶＯがスライス
レベルＳＬＴＶＯ未満であるときには、ステップ４へ進
み、水温ＴＷがスライスレベルＳＬＴＷを越えているか
否かを判別する。そして、水温ＴＷがスライスレベルＳ
ＬＴＷを越えているとき、即ち、低負荷低回転領域の定
常かつ完暖状態であるときには、ステップ５へ進んで、
リーン燃焼の許可を判定し、フラグＦＬＧＬＥＮに１を
セットする。When the throttle opening change rate ΔTVO is less than the slice level SLTVO, the routine proceeds to step 4, where it is judged if the water temperature TW exceeds the slice level SLTW. And the water temperature TW is the slice level S
When it exceeds LTW, that is, when it is in the steady and completely warm state of the low load and low rotation region, the routine proceeds to step 5,
The permission of lean combustion is determined, and the flag FLGLEN is set to 1.

【００３６】一方、ステップ１〜４のリーン許可条件の
うちのいずれか１つでも成立していないときには、ステ
ップ６へ進み、リーン燃焼の不許可を判定して前記フラ
グＦＬＧＬＥＮに０をセットする。ステップ７では、前
記ＮＯｘ吸収触媒８におけるＮＯｘ吸収量の予測値であ
るＳＩＧＮＯに０をセットする。リーン燃焼運転でな
く、理論空燃比（又はリッチ）燃焼運転を行わせるとき
には、前記ＮＯｘ吸収触媒８においてＮＯｘが逐次還元
処理され、ＮＯｘが吸収されることがないので、前述の
ように、吸収量ＳＩＧＮＯに０をセットする。On the other hand, when any one of the lean permission conditions of steps 1 to 4 is not satisfied, the routine proceeds to step 6, where it is judged that lean combustion is not permitted and 0 is set to the flag FLGLEN. In step 7, SIGNO, which is a predicted value of the NOx absorption amount in the NOx absorption catalyst 8, is set to 0. When the theoretical air-fuel ratio (or rich) combustion operation is performed instead of the lean combustion operation, NOx is successively reduced in the NOx absorption catalyst 8 and NOx is not absorbed. Set SIGNO to 0.

【００３７】図６のフローチャートは、理論空燃比燃焼
時における噴射量Ｔｉ制御の様子（ストイキ空燃比制御
手段Ｂ）を示すものであり、ステップ11では、吸入空気
流量Ｑａ及び機関回転数Ｎｅの検出値を読み込む。ステ
ップ12では、基本噴射量Ｔｐを、 Ｔｐ＝ｋ×Ｑａ／Ｎｅ （ｋは定数） として演算する。The flow chart of FIG. 6 shows the state of the injection amount Ti control at stoichiometric air-fuel ratio combustion (Stoichiometric air-fuel ratio control means B). In step 11, the intake air flow rate Qa and the engine speed Ne are detected. Read the value. In step 12, the basic injection amount Tp is calculated as Tp = k × Qa / Ne (k is a constant).

【００３８】ステップ13では、酸素センサ14の信号に基
づいて実際の空燃比の理論空燃比に対するリッチ・リー
ンを判定し、該リッチ・リーンの判定結果に基づいて、
空燃比フィードバック補正係数αを例えば比例・積分制
御する。ステップ14では、前記基本噴射量Ｔｐを、前記
空燃比フィードバック補正係数α等によって補正して最
終的な燃料噴射量Ｔｉを演算する。In step 13, the rich lean of the actual air-fuel ratio with respect to the theoretical air-fuel ratio is judged based on the signal of the oxygen sensor 14, and based on the rich lean judgment result,
The air-fuel ratio feedback correction coefficient α is, for example, proportionally / integrally controlled. In step 14, the basic injection amount Tp is corrected by the air-fuel ratio feedback correction coefficient α or the like to calculate the final fuel injection amount Ti.

【００３９】Ｔｉ＝Ｔｐ×α コントロールユニット５は、各気筒の吸気行程に合わせ
た噴射タイミングにおいて、前記燃料噴射量Ｔｉに相当
するパルス幅の噴射パルス信号を燃料噴射弁４に出力し
て、燃料噴射弁４による燃料噴射を制御し、理論空燃比
（ストイキ）燃焼運転を行わせる。Ti = Tp × α The control unit 5 outputs an injection pulse signal having a pulse width corresponding to the fuel injection amount Ti to the fuel injection valve 4 at the injection timing adjusted to the intake stroke of each cylinder, and the fuel is injected. The fuel injection by the injection valve 4 is controlled to perform stoichiometric air-fuel ratio (stoichiometric) combustion operation.

【００４０】一方、図７のフローチャートは、リーン燃
焼時における噴射量Ｔｉ制御の様子（リーン空燃比制御
手段Ｃ）を示すものであり、ステップ21では、吸入空気
流量Ｑａ及び機関回転数Ｎｅの検出値を読み込み、ステ
ップ22では、理論空燃比相当の基本噴射量Ｔｐを演算す
る。そして、ステップ23では、そのときの目標空燃比
と、前記理論空燃比相当の基本噴射量Ｔｐとに基づい
て、リーン燃焼時の燃料噴射量Ｔｉを演算する。On the other hand, the flowchart of FIG. 7 shows the state of the injection amount Ti control (lean air-fuel ratio control means C) at the time of lean combustion. In step 21, the intake air flow rate Qa and the engine speed Ne are detected. The value is read, and in step 22, the basic injection amount Tp equivalent to the theoretical air-fuel ratio is calculated. Then, in step 23, the fuel injection amount Ti during lean combustion is calculated based on the target air-fuel ratio at that time and the basic injection amount Tp corresponding to the theoretical air-fuel ratio.

【００４１】Ｔｉ＝Ｔｐ×14.7／目標空燃比 コントロールユニット５は、成層リーン燃焼を行わせる
場合には各気筒の圧縮行程において、また、均質リーン
燃焼を行わせる場合には各気筒の吸気行程において、前
記燃料噴射量Ｔｉに相当するパルス幅の噴射パルス信号
を燃料噴射弁４に出力して、リーン燃焼運転を行わせ
る。Ti = Tp × 14.7 / target air-fuel ratio control unit 5 controls the compression stroke of each cylinder when stratified lean combustion is performed, and the intake stroke of each cylinder when homogeneous lean combustion is performed. , An injection pulse signal having a pulse width corresponding to the fuel injection amount Ti is output to the fuel injection valve 4 to perform lean combustion operation.

【００４２】ここで、リーン燃焼運転中には、前述のよ
うにＮＯｘがＮＯｘ吸収触媒８に吸収されることにな
り、このＮＯｘ吸収触媒８に対するＮＯｘ吸収量が、図
８のフローチャートに示すようにして推定される（ＮＯ
ｘ吸収量予測手段Ｄ）。図８のフローチャートは、１se
c 毎に実行されるようになっており、ステップ31では、
前記フラグＦＬＧＬＥＮの判別によってリーン燃焼状態
であるか否かを判別する。Here, during lean combustion operation, NOx is absorbed by the NOx absorption catalyst 8 as described above, and the NOx absorption amount for this NOx absorption catalyst 8 is as shown in the flow chart of FIG. Estimated (NO
x absorption amount predicting means D). The flow chart of FIG. 8 is 1se
It is executed every c, and in step 31,
Whether the lean combustion state is set or not is determined by the determination of the flag FLGLEN.

【００４３】前記フラグＦＬＧＬＥＮに１がセットされ
ていてリーン燃焼が許可される条件であるときには、ス
テップ32へ進み、前記ＮＯｘ吸収触媒８に吸収されたＮ
Ｏｘを還元処理するための膨張〜排気行程噴射の許可状
態であるか否かを、フラグＦＬＧＲＳに基づいて判別す
る。尚、上記膨張〜排気行程噴射及びフラグＦＬＧＲＳ
については、後に詳細に説明する。When the flag FLGLEN is set to 1 and the condition is that lean combustion is permitted, the routine proceeds to step 32, where N absorbed by the NOx absorbing catalyst 8 is admitted.
Whether or not the expansion-exhaust stroke injection for Ox reduction processing is permitted is determined based on the flag FLGRS. The expansion-exhaust stroke injection and the flag FLGRS
Will be described in detail later.

【００４４】前記フラグＦＬＧＲＳに０がセットされて
いて、ＮＯｘ還元処理のための膨張〜排気行程噴射が行
われない状態であるとき、換言すれば、ＮＯｘ吸収触媒
８にＮＯｘが吸収されるリーン燃焼運転時であるときに
は、ステップ33へ進む。ステップ33では、機関回転数Ｎ
ｅ及び機関負荷を代表する基本噴射量Ｔｐを読み込む。When the flag FLGRS is set to 0 and the expansion-exhaust stroke injection for the NOx reduction process is not performed, in other words, the lean combustion in which NOx is absorbed by the NOx absorption catalyst 8 is performed. If it is during operation, go to step 33. In step 33, the engine speed N
e and the basic injection amount Tp representing the engine load are read.

【００４５】ステップ34では、予め機関回転数Ｎｅ及び
機関負荷をパラメータとして１秒当たりのＮＯｘ排出量
ＮＯＧを記憶したマップを参照し、現在の機関回転数Ｎ
ｅ及び機関負荷に対応する排出量ＮＯＧを読み出す。ス
テップ35では、前記ステップ34で読み出した排出量ＮＯ
Ｇをそれまでの吸収量ＳＩＧＮＯに加算して、該加算結
果を新たな吸収量ＳＩＧＮＯとする。即ち、リーン燃焼
運転中には、機関回転数Ｎｅ及び機関負荷から推定され
る機関１からのＮＯｘ排出量を逐次積算して、ＮＯｘ吸
収触媒８に対するＮＯｘの吸収量を予測する。In step 34, the map in which the NOx emission amount NOG per second is stored in advance with the engine speed Ne and the engine load as parameters is referred to, and the current engine speed N
The emission amount NOG corresponding to e and the engine load is read. In step 35, the emission amount NO read in step 34
G is added to the absorption amount SIGNO until then, and the addition result is set as a new absorption amount SIGNO. That is, during the lean combustion operation, the NOx emission amount estimated from the engine speed Ne and the engine load is sequentially integrated to predict the NOx absorption amount for the NOx absorption catalyst 8.

【００４６】尚、ＮＯｘ吸収量の予測方法を上記に限定
するものではなく、機関回転数及び機関負荷以外の条件
で燃焼空燃比が変化する場合には、燃焼空燃比をパラメ
ータに含めてＮＯｘ吸収量を予測させれば良い。図９の
フローチャートは、前記吸収量ＳＩＧＮＯに基づいてリ
ーン燃焼運転中にＮＯｘを脱離・還元処理するための制
御（２次噴射許可手段Ｅ）を示すものである。The method of predicting the NOx absorption amount is not limited to the above, and when the combustion air-fuel ratio changes under conditions other than engine speed and engine load, the combustion air-fuel ratio is included in the parameters to absorb NOx. Just predict the quantity. The flowchart of FIG. 9 shows the control (secondary injection permission means E) for performing desorption / reduction processing of NOx during lean combustion operation based on the absorption amount SIGNO.

【００４７】ステップ41では、前記推定された吸収量Ｓ
ＩＧＮＯがスライスレベルＳＬＳＮＯを越えているか否
かを判別する。そして、ＮＯｘ吸収触媒８におけるＮＯ
ｘ吸収量ＳＩＧＮＯがスライスレベルＳＬＳＮＯを越え
ているときには、ステップ42へ進み、ＮＯｘ処理時間Ｎ
ＯＴＩＭＥ（ＮＯｘ浄化のための膨張〜排気行程噴射の
継続時間）がスライスレベルＳＬＮＯＴＭ未満であるか
否かを判別する。In step 41, the estimated absorption amount S
It is determined whether the IGNO exceeds the slice level SLSNO. Then, the NO in the NOx absorption catalyst 8
When the x absorption amount SIGNO exceeds the slice level SLSNO, the routine proceeds to step 42, where the NOx processing time N
It is determined whether or not OTIME (expansion for NOx purification-duration of exhaust stroke injection) is less than the slice level SLNOTM.

【００４８】ＮＯｘ処理時間ＮＯＴＩＭＥがスライスレ
ベルＳＬＮＯＴＭ未満であるときには、ＮＯｘ吸収触媒
８に吸収されたＮＯｘの脱離・還元を行うための処理を
行わせるべく、ステップ43へ進んで、フラグＦＬＧＲＳ
に１をセットする。一方、ＮＯｘ処理時間ＮＯＴＩＭＥ
がスライスレベルＳＬＮＯＴＭ以上になったときには、
スライスレベルＳＬＳＮＯを越えるまでに増大したＮＯ
ｘ吸収量ＳＩＧＮＯの脱離・還元処理が終了したものと
見做し、ステップ44で前記ＮＯｘ吸収量ＳＩＧＮＯをゼ
ロリセットした後、ステップ45へ進んで、前記フラグＦ
ＬＧＲＳに０をセットする。When the NOx processing time NOTTIME is less than the slice level SLNOTM, the routine proceeds to step 43, in order to execute the processing for desorbing / reducing the NOx absorbed by the NOx absorption catalyst 8, the flag FLGRS.
Set 1 to. On the other hand, NOx processing time NOTIME
Is above the slice level SLNOTM,
NO increased to exceed the slice level SLSNO
It is considered that the desorption / reduction processing of the x absorption amount SIGNO has been completed, and the NOx absorption amount SIGNO is reset to zero in step 44, and then the routine proceeds to step 45, where the flag F
Set 0 to LGRS.

【００４９】ステップ41でＮＯｘ吸収量ＳＩＧＮＯがス
ライスレベルＳＬＳＮＯ以下であると判別されたときに
も、吸収されたＮＯｘの脱離・還元処理は必要ないもの
と判断して、ステップ45へ進む。前記ＮＯｘ吸収触媒８
においてはリーン燃焼運転中にＮＯｘを吸収し、運転が
理論空燃比燃焼又はリッチ燃焼に切り換われば、それま
でに吸収したＮＯｘが脱離・還元処理されることになる
が、リーン燃焼運転が継続されてＮＯｘを脱離・還元処
理する機会がないと、ＮＯｘ吸収量が最大吸収量を越え
るようになってしまい、機関１から排出されるＮＯｘが
そのまま大気中に排出されることになってしまう。Even when it is determined in step 41 that the NOx absorption amount SIGNO is less than or equal to the slice level SLSNO, it is judged that the desorption / reduction processing of the absorbed NOx is not necessary, and the routine proceeds to step 45. The NOx absorption catalyst 8
In this case, if NOx is absorbed during lean combustion operation and the operation switches to stoichiometric air-fuel ratio combustion or rich combustion, the NOx absorbed up to that point will be desorbed / reduced, but lean combustion operation If there is no opportunity to continue desorption / reduction of NOx, the NOx absorption amount will exceed the maximum absorption amount, and NOx discharged from the engine 1 will be directly discharged to the atmosphere. I will end up.

【００５０】そこで、リーン燃焼中にＮＯｘ吸収量ＳＩ
ＧＮＯが許容量ＳＬＳＮＯを越えたときには、ＮＯｘ吸
収触媒８の雰囲気を強制的に還元雰囲気として吸収され
たＮＯｘの脱離・還元を行わせる必要があり、本願発明
では、ＮＯｘ吸収触媒８の上流側に介装した酸化触媒７
と膨張〜排気行程での燃料噴射との組み合わせによっ
て、リーン燃焼運転を行わせたまま前記還元雰囲気を作
り出せるようにしている。Therefore, the NOx absorption amount SI during lean combustion
When the GNO exceeds the allowable amount SLSNO, it is necessary to forcibly desorb and reduce the absorbed NOx as the reducing atmosphere in the atmosphere of the NOx absorption catalyst 8. In the present invention, the upstream side of the NOx absorption catalyst 8 Oxidation catalyst 7
The expansion and the fuel injection in the exhaust stroke are combined to create the reducing atmosphere while the lean combustion operation is performed.

【００５１】図10のフローチャートは、前記膨張〜排気
行程噴射の制御の様子（噴射量算出手段Ｆ：排気行程噴
射制御手段，排気行程噴射量演算手段）を示すものであ
り、ステップ51では、前記フラグＦＬＧＲＳに１がセッ
トされているか否かを判別する。前記フラグＦＬＧＲＳ
に１がセットされている場合には、ステップ52へ進み、
過剰酸素を消費させるために各気筒の膨張〜排気行程で
噴射させる燃料噴射量ＴＩＯ２を、 ＴＩＯ２＝Ｔｐ×（１−14.7／目標空燃比） として演算する。The flow chart of FIG. 10 shows the state of control of the expansion-exhaust stroke injection (injection amount calculation means F: exhaust stroke injection control means, exhaust stroke injection amount calculation means). It is determined whether 1 is set in the flag FLGRS. The flag FLGRS
If 1 is set to, go to step 52,
The fuel injection amount TIO2 to be injected from the expansion to the exhaust stroke of each cylinder in order to consume excess oxygen is calculated as TIO2 = Tp × (1-14.7 / target air-fuel ratio).

【００５２】前記基本噴射量Ｔｐは、理論空燃比相当の
基本噴射量であり、シリンダ吸入空気量を示すことにな
り、目標空燃比はそのときの燃焼空燃比である。上記燃
料噴射量ＴＩＯ２は、理論空燃比相当の基本噴射量Ｔｐ
からリーン燃焼相当の基本噴射量Ｔｐ’を減算した値と
なり、このＴＩＯ２分だけ燃焼に供する燃料量が少ない
ために過剰酸素の排気が排出されることになる。前記燃
料噴射弁４は燃焼室内に直接燃料を噴射するから、膨張
〜排気行程で燃料を噴射させると、排気と共に燃料がそ
のまま排気系に流れ出すことになり、この燃焼室から排
出された燃料は、酸化触媒７の酸化作用で燃焼し、酸素
を消費することになる。従って、前記燃料量ＴＩＯ２だ
け膨張〜排気行程で燃料を噴射させれば、酸化触媒７に
おいて燃料が燃焼することで、過剰酸素が消費される。The basic injection amount Tp is a basic injection amount corresponding to the theoretical air-fuel ratio and represents the cylinder intake air amount, and the target air-fuel ratio is the combustion air-fuel ratio at that time. The fuel injection amount TIO2 is the basic injection amount Tp corresponding to the theoretical air-fuel ratio.
It becomes a value obtained by subtracting the basic injection amount Tp ′ corresponding to lean combustion from this, and since the amount of fuel used for combustion is small by this TIO2, exhaust of excess oxygen is exhausted. Since the fuel injection valve 4 injects fuel directly into the combustion chamber, if fuel is injected in the expansion-exhaust stroke, the fuel will flow out to the exhaust system together with the exhaust gas, and the fuel discharged from this combustion chamber will be Oxidation of the oxidation catalyst 7 burns and consumes oxygen. Therefore, if the fuel is injected by the fuel amount TIO2 during the expansion to the exhaust stroke, the fuel is burned in the oxidation catalyst 7, and excess oxygen is consumed.

【００５３】ステップ53では、予めＮＯｘ吸収量ＳＩＧ
ＮＯに応じてＮＯｘ還元のための燃料量ＴＩＮＯを記憶
したテーブルを参照し、そのときの吸収量ＳＩＧＮＯに
対応する燃料量ＴＩＮＯを読み出す。そして、ステップ
54では、前記ＴＩＯ２とＴＩＮＯとの合計を、最終的な
膨張〜排気行程における燃料噴射量ＴＩＲＳにセットす
る。コントロールユニット５は、吸気行程又は圧縮行程
での燃焼に供される燃料噴射の他に、各気筒の膨張〜排
気行程において前記燃料噴射量ＴＩＲＳに相当するパル
ス幅の噴射パルス信号を各燃料噴射弁４に出力する。In step 53, the NOx absorption amount SIG is previously set.
A table that stores the fuel amount TINO for NOx reduction according to NO is referred to, and the fuel amount TINO corresponding to the absorption amount SIGNO at that time is read. And step
At 54, the sum of TIO2 and TINO is set to the fuel injection amount TIRS in the final expansion-exhaust stroke. In addition to the fuel injection used for combustion in the intake stroke or the compression stroke, the control unit 5 outputs an injection pulse signal having a pulse width corresponding to the fuel injection amount TIRS in each cylinder from the expansion stroke to the exhaust stroke of each cylinder. Output to 4.

【００５４】ここで、前記燃料噴射量ＴＩＲＳによる排
気行程噴射の開始から前記図９のフローチャートのステ
ップ２で判別される一定時間ＳＬＮＯＴＭが経過する
と、ＮＯｘ吸収量ＳＩＧＮＯがゼロリセットされると共
に、フラグＦＬＧＲＳに１がセットされることで、ステ
ップ51からステップ55に進むようになる。そして、ステ
ップ55で前記燃料噴射量ＴＩＲＳに０がセットされるよ
うになることで、膨張〜排気行程での燃料噴射が停止さ
れ、通常のリーン燃焼のための吸気或いは圧縮行程での
噴射のみが行われるようになる。Here, when the predetermined time SLNOTM determined in step 2 of the flow chart of FIG. 9 has elapsed from the start of the exhaust stroke injection by the fuel injection amount TIRS, the NOx absorption amount SIGNO is reset to zero and the flag FLGRS. By setting 1 to, the process proceeds from step 51 to step 55. Then, in step 55, the fuel injection amount TIRS is set to 0, so that the fuel injection in the expansion-exhaust stroke is stopped and only the injection in the intake or compression stroke for normal lean combustion is performed. Will be done.

【００５５】前記燃料量ＴＩＯ２だけ膨張〜排気行程で
燃料を噴射させることで、過剰酸素状態を解消して、Ｎ
Ｏｘ吸収触媒８に流入する排気の空燃比をリッチにでき
るものの、ＮＯｘの還元処理には、同時にＨＣの酸化処
理が行われる必要がある。そのため、酸化触媒７で燃焼
せずにＮＯｘ吸収触媒８に到達して、ＮＯｘ還元処理と
同時に酸化処理されるＨＣを確保すべく、ＮＯｘ吸収量
に応じた燃料量ＴＩＮＯを前記燃料量ＴＩＯ２に加えて
噴射させるものである。By injecting fuel in the expansion-exhaust stroke by the fuel amount TIO2, the excess oxygen state is eliminated, and N
Although it is possible to make the air-fuel ratio of the exhaust gas flowing into the Ox absorption catalyst 8 rich, it is necessary to simultaneously perform the oxidation process of HC for the reduction process of NOx. Therefore, in order to secure the HC that reaches the NOx absorption catalyst 8 without being burned by the oxidation catalyst 7 and is oxidized at the same time as the NOx reduction process, the fuel amount TINO corresponding to the NOx absorption amount is added to the fuel amount TIO2. It is what makes it jet.

【００５６】上記のように燃料噴射量ＴＩＲＳだけ膨張
〜排気行程噴射を行わせれば、酸化触媒７における燃焼
によって過剰酸素状態が解消されて排気空燃比がリッチ
となり、下流側のＮＯｘ吸収触媒８においてＮＯｘの脱
離が行われるようになり、更に、酸化触媒７で燃焼せず
にＮＯｘ吸収触媒８に流れ込む燃料（ＨＣ）の酸化反応
に伴ってＮＯｘの還元処理が行われることになる。If the expansion-exhaust stroke injection is performed by the fuel injection amount TIRS as described above, the excess oxygen state is eliminated by the combustion in the oxidation catalyst 7 and the exhaust air-fuel ratio becomes rich, and in the NOx absorption catalyst 8 on the downstream side. The NOx is desorbed, and further, the NOx reduction process is performed along with the oxidation reaction of the fuel (HC) flowing into the NOx absorption catalyst 8 without being burned by the oxidation catalyst 7.

【００５７】上記のように、膨張〜排気行程での噴射
（２次噴射）により供給された燃料は酸化触媒７で燃焼
することになるが、一般に、ＮＯｘ吸収触媒８に比して
酸化触媒（三元触媒）７の耐熱性が高いために触媒劣化
の原因となることがない。また、上記のように、過剰酸
素状態を解消するのに要する燃料量と、脱離されたＮＯ
ｘを還元処理するのに要する燃料（ＨＣ）量とに基づい
て、膨張〜排気行程で噴射させる燃料量を決定する構成
であれば、確実にＮＯｘの脱離，還元処理を行え、然
も、燃費性能の悪化を回避できる。As described above, the fuel supplied by the injection (secondary injection) from the expansion to the exhaust stroke is burned by the oxidation catalyst 7, but generally the oxidation catalyst (compared to the NOx absorption catalyst 8 ( Since the three-way catalyst 7 has high heat resistance, it does not cause catalyst deterioration. Further, as described above, the amount of fuel required to eliminate the excess oxygen state and the desorbed NO
If the configuration is such that the amount of fuel to be injected in the expansion-exhaust stroke is determined based on the amount of fuel (HC) required to reduce x, the desorption and reduction processes of NOx can be performed with certainty. It is possible to avoid deterioration of fuel efficiency.

【００５８】ところで、膨張〜排気行程での燃料噴射に
よって、ＮＯｘ吸収触媒８に流れ込む排気の空燃比を確
実にリッチにするために、図11に示すように、酸化触媒
７の下流側でＮＯｘ吸収触媒８上流側の排気通路９に、
排気中の酸素濃度に基づいて排気空燃比を広域に検出で
きる空燃比センサ15（排気空燃比検出手段）を設け、前
記燃料噴射量ＴＩＲＳを前記空燃比センサ15による検出
結果に基づいてフィードバック制御するようにしても良
い（噴射量フィードバック手段）。By the way, in order to surely make the air-fuel ratio of the exhaust gas flowing into the NOx absorption catalyst 8 rich by the fuel injection from the expansion to the exhaust stroke, as shown in FIG. 11, the NOx absorption is performed on the downstream side of the oxidation catalyst 7. In the exhaust passage 9 on the upstream side of the catalyst 8,
An air-fuel ratio sensor 15 (exhaust air-fuel ratio detecting means) that can detect the exhaust air-fuel ratio in a wide range based on the oxygen concentration in the exhaust is provided, and the fuel injection amount TIRS is feedback-controlled based on the detection result by the air-fuel ratio sensor 15. Alternatively, the injection amount feedback means may be used.

【００５９】具体的には、前記空燃比センサ15で検出さ
れる排気空燃比と、ＮＯｘ吸収触媒８に流入させる排気
の目標空燃比とを比較し、目標よりも実際の空燃比がリ
ーンであるときには噴射量を増量修正し、逆に、リッチ
であるときには噴射量を減量修正するようにする。かか
る構成とすれば、各種のばらつき要因があっても、ＮＯ
ｘ吸収触媒８入口における排気空燃比をリッチ状態とし
て、ＮＯｘ吸収触媒８に吸収されたＮＯｘの脱離・還元
を確実に行わせることができる。Specifically, the exhaust air-fuel ratio detected by the air-fuel ratio sensor 15 is compared with the target air-fuel ratio of the exhaust gas flowing into the NOx absorption catalyst 8, and the actual air-fuel ratio is leaner than the target. Sometimes, the injection amount is corrected to increase, and conversely, when it is rich, the injection amount is corrected to decrease. With such a configuration, even if there are various variation factors, NO
By making the exhaust air-fuel ratio at the inlet of the x absorption catalyst 8 rich, it is possible to reliably desorb and reduce the NOx absorbed by the NOx absorption catalyst 8.

【図面の簡単な説明】[Brief description of drawings]

【図１】請求項３記載の発明に係る排気浄化装置の基本
構成を示すブロック図。FIG. 1 is a block diagram showing a basic configuration of an exhaust emission control device according to a third aspect of the invention.

【図２】実施の形態における内燃機関のシステム構成
図。FIG. 2 is a system configuration diagram of an internal combustion engine in the embodiment.

【図３】ＮＯｘ吸収触媒のＮＯｘの吸放出作用を説明す
るための図。FIG. 3 is a diagram for explaining a NOx absorption / release action of a NOx absorption catalyst.

【図４】上記実施の形態における基本的な燃料制御ブロ
ック図。FIG. 4 is a basic fuel control block diagram in the above embodiment.

【図５】リーン・ストイキの切り替え制御を示すフロー
チャート。FIG. 5 is a flowchart showing lean / stoichi switching control.

【図６】ストイキ燃焼時の燃料噴射制御を示すフローチ
ャート。FIG. 6 is a flowchart showing fuel injection control during stoichiometric combustion.

【図７】リーン燃焼時の燃料噴射制御を示すフローチャ
ート。FIG. 7 is a flowchart showing fuel injection control during lean combustion.

【図８】ＮＯｘ吸収量の予測制御を示すフローチャー
ト。FIG. 8 is a flowchart showing a predictive control of the NOx absorption amount.

【図９】膨張〜排気行程噴射の許可制御を示すフローチ
ャート。FIG. 9 is a flowchart showing expansion-exhaust stroke injection permission control.

【図10】膨張〜排気行程噴射の噴射量演算を示すフロー
チャート。FIG. 10 is a flowchart showing an injection amount calculation of expansion-exhaust stroke injection.

【図11】第２の実施の形態における内燃機関のシステム
構成図。FIG. 11 is a system configuration diagram of an internal combustion engine according to the second embodiment.

【符号の説明】[Explanation of symbols]

１ 内燃機関 ２ エアクリーナ ３ スロットル弁 ４ 燃料噴射弁 ５ コントロールユニット ６ 点火プラグ ７ 酸化触媒 ８ ＮＯｘ吸収触媒 ９ 排気通路 10 エアフローメータ 11 スロットルセンサ 12 水温センサ 13 クランク角センサ 14 酸素センサ 15 空燃比センサ 1 Internal combustion engine 2 air cleaner 3 Throttle valve 4 Fuel injection valve 5 control unit 6 spark plugs 7 Oxidation catalyst 8 NOx absorption catalyst 9 exhaust passage 10 Air flow meter 11 Throttle sensor 12 Water temperature sensor 13 Crank angle sensor 14 Oxygen sensor 15 Air-fuel ratio sensor

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ Ｆ０１Ｎ 3/24 Ｆ０１Ｎ 3/24 Ｒ Ｆ０２Ｄ 41/02 ３２５ Ｆ０２Ｄ 41/02 ３２５Ａ 41/04 ３０５ 41/04 ３０５Ｚ 41/14 ３１０ 41/14 ３１０Ａ (56)参考文献 特開 平８−200045（ＪＰ，Ａ) 特開 平９−32619（ＪＰ，Ａ) 特開 平８−312408（ＪＰ，Ａ) 国際公開96／22457（ＷＯ，Ａ１) (58)調査した分野(Int.Cl.7，ＤＢ名) F02D 41/34 F01N 3/08 F01N 3/24 F02D 41/02 325 F02D 41/04 305 F02D 41/14 310 ─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. 7 Identification code FI F01N 3/24 F01N 3/24 R F02D 41/02 325 F02D 41/02 325A 41/04 305 41/04 305Z 41/14 310 41 / 14 310A (56) Reference JP-A-8-200045 (JP, A) JP-A-9-32619 (JP, A) JP-A-8-312408 (JP, A) International Publication 96/22457 (WO, A1) ) (58) Fields surveyed (Int.Cl. 7 , DB name) F02D 41/34 F01N 3/08 F01N 3/24 F02D 41/02 325 F02D 41/04 305 F02D 41/14 310

Claims (6)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】内燃機関の燃焼室内に直接燃料を噴射する
燃料噴射弁を備え、理論空燃比よりもリーン空燃比での
燃焼運転を行いうる内燃機関の排気浄化装置であって、 排気空燃比が理論空燃比よりもリーンであるときに排気
中のＮＯｘを吸収し、排気空燃比が理論空燃比又は理論
空燃比よりもリッチであるときに前記吸収したＮＯｘを
放出して還元処理するＮＯｘ吸収触媒と、該ＮＯｘ吸収
触媒よりも上流側の排気通路に介装される酸化触媒とを
備え、リーン燃焼中に前記燃料噴射弁により膨張〜排気
行程で燃料を噴射させることにより、前記ＮＯｘ吸収触
媒の入口での排気空燃比をリッチにして、前記ＮＯｘ吸
収触媒に吸収されたＮＯｘの還元処理を行うと共に、前
記膨張〜排気行程で噴射される燃料量を、吸入空気量，
燃焼空燃比，ＮＯｘ吸収触媒におけるＮＯｘ吸収量に応
じて設定することを特徴とする内燃機関の排気浄化装
置。1. An exhaust gas purification apparatus for an internal combustion engine, comprising: a fuel injection valve for directly injecting fuel into a combustion chamber of the internal combustion engine; and capable of performing a combustion operation at a lean air-fuel ratio rather than a stoichiometric air-fuel ratio. Is leaner than the stoichiometric air-fuel ratio, NOx in the exhaust gas is absorbed, and when the exhaust air-fuel ratio is the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio, the absorbed NOx is released to perform reduction processing. The NOx absorption catalyst is provided with a catalyst and an oxidation catalyst that is interposed in the exhaust passage on the upstream side of the NOx absorption catalyst, and injects fuel during the expansion-exhaust stroke by the fuel injection valve during lean combustion. of the exhaust air-fuel ratio at the inlet to the rich, performs reduction processing of the NOx absorbed in the NOx absorbent catalyst, before
The amount of fuel injected during the expansion-exhaust stroke is defined as the intake air amount,
Depending on the combustion air-fuel ratio and the NOx absorption amount in the NOx absorption catalyst,
An exhaust gas purification device for an internal combustion engine, which is characterized in that it is set in advance. 【請求項２】前記吸入空気量と燃焼空燃比とに基づいて
前記酸化触媒における酸化反応で排気中の酸素を消費す
る分の燃料量を演算する一方、前記ＮＯｘ吸収触媒にお
けるＮＯｘ吸収量に基づいてＮＯｘを還元処理する分の
燃料量を演算し、これらの合計を膨張〜排気行程で噴射
する燃料量とすることを特徴とする請求項１記載の内燃
機関の排気浄化装置。2. A fuel amount for consuming oxygen in exhaust gas by an oxidation reaction in the oxidation catalyst is calculated on the basis of the intake air amount and a combustion air-fuel ratio, and based on a NOx absorption amount in the NOx absorption catalyst. the NOx calculates the amount of fuel quantity reduction treatment Te, exhaust purification system of an internal combustion engine according to claim 1, characterized in that the amount of fuel injected these total expansion-exhaust stroke. 【請求項３】内燃機関の燃焼室内に直接燃料を噴射する
燃料噴射弁を備え、理論空燃比よりもリーン空燃比での
燃焼運転を行いうる内燃機関の排気浄化装置であって、 排気空燃比が理論空燃比よりもリーンであるときに排気
中のＮＯｘを吸収し、排気空燃比が理論空燃比又は理論
空燃比よりもリッチであるときに前記吸収したＮＯｘを
放出して還元処理するＮＯｘ吸収触媒と、 該ＮＯｘ吸収触媒よりも上流側の排気通路に介装される
酸化触媒と、 前記ＮＯｘ吸収触媒におけるＮＯｘの吸収量を予測する
ＮＯｘ吸収量予測手段と、 リーン燃焼運転中に前記ＮＯｘ吸収量予測手段で予測さ
れるＮＯｘ吸収量が所定値以上になったときに、前記燃
料噴射弁により膨張〜排気行程中に燃料噴射を所定期間
だけ行わせる排気行程噴射制御手段と、 前記排気行程噴射制御手段による燃料噴射量を、機関の
吸入空気量，燃焼空燃比及び前記ＮＯｘ吸収量予測手段
で予測されたＮＯｘ吸収量に基づいて演算する排気行程
噴射量演算手段と、 を含んで構成されたことを特徴とする内燃機関の排気浄
化装置。3. An exhaust gas purifying apparatus for an internal combustion engine, comprising: a fuel injection valve for directly injecting fuel into a combustion chamber of the internal combustion engine and capable of performing a combustion operation at a lean air-fuel ratio rather than a stoichiometric air-fuel ratio. Is leaner than the stoichiometric air-fuel ratio, NOx in the exhaust gas is absorbed, and when the exhaust air-fuel ratio is the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio, the absorbed NOx is released to perform reduction processing. A catalyst, an oxidation catalyst installed in an exhaust passage upstream of the NOx absorption catalyst, a NOx absorption amount prediction means for predicting the amount of NOx absorbed in the NOx absorption catalyst, and the NOx absorption during lean combustion operation. Exhaust stroke injection control means for causing the fuel injection valve to perform fuel injection only during a predetermined period during the expansion-exhaust stroke when the NOx absorption amount predicted by the amount predicting means exceeds a predetermined value; An exhaust stroke injection quantity computing means for computing the fuel injection quantity by the exhaust stroke injection control means based on the intake air quantity of the engine, the combustion air-fuel ratio, and the NOx absorption quantity predicted by the NOx absorption quantity prediction means. An exhaust gas purification device for an internal combustion engine, which is configured. 【請求項４】前記排気行程噴射量演算手段が、前記吸入
空気量と燃焼空燃比とに基づいて前記酸化触媒における
酸化反応で排気中の酸素を消費する分の燃料量を演算す
る一方、前記ＮＯｘ吸収触媒におけるＮＯｘ吸収量に基
づいてＮＯｘを還元処理する分の燃料量を演算し、これ
らの合計を膨張〜排気行程で噴射する燃料量として演算
することを特徴とする請求項３記載の内燃機関の排気浄
化装置。4. The exhaust stroke injection amount calculation means calculates a fuel amount for consuming oxygen in exhaust gas by an oxidation reaction in the oxidation catalyst on the basis of the intake air amount and a combustion air-fuel ratio, while 4. The internal combustion engine according to claim 3 , wherein the amount of fuel for reducing NOx is calculated based on the amount of NOx absorbed in the NOx absorption catalyst, and the sum of these is calculated as the amount of fuel injected during the expansion-exhaust stroke. Exhaust gas purification device for engines. 【請求項５】前記排気行程噴射量演算手段が、機関の吸
入空気量と燃焼空燃比とに基づいて、理論空燃比燃焼時
相当の燃料噴射量とそのときの燃焼空燃比での燃料噴射
量との差分を演算し、この差分を前記酸化触媒における
酸化反応で排気中の酸素を消費する分の燃料量とするこ
とを特徴とする請求項４記載の内燃機関の排気浄化装
置。5. The exhaust stroke injection amount calculation means, based on the intake air amount of the engine and the combustion air-fuel ratio, the fuel injection amount corresponding to the stoichiometric air-fuel ratio combustion and the fuel injection amount at the combustion air-fuel ratio at that time. 5. The exhaust gas purification apparatus for an internal combustion engine according to claim 4 , wherein a difference between the exhaust gas and the exhaust gas is calculated, and the difference is used as a fuel amount for consuming oxygen in the exhaust gas by the oxidation reaction in the oxidation catalyst. 【請求項６】前記酸化触媒の下流側でかつ前記ＮＯｘ吸
収触媒の上流側の排気通路において排気空燃比を検出す
る排気空燃比検出手段と、 該排気空燃比検出手段で検出される排気空燃比に基づい
て前記排気行程噴射制御手段による膨張〜排気行程での
燃料噴射量をフィードバック補正する噴射量フィードバ
ック手段と、 を設けたことを特徴とする請求項３〜５のいずれか１つ
に記載の内燃機関の排気浄化装置。6. Exhaust air-fuel ratio detection means for detecting an exhaust air-fuel ratio in an exhaust passage downstream of the oxidation catalyst and upstream of the NOx absorption catalyst, and exhaust air-fuel ratio detected by the exhaust air-fuel ratio detection means. according to any one of claims 3-5, characterized in that a, the injection quantity feedback unit for feedback correction of the fuel injection quantity in the expansion-exhaust stroke by the exhaust stroke injection control means based on Exhaust gas purification device for internal combustion engine.
JP20640997A 1997-07-31 1997-07-31 Exhaust gas purification device for internal combustion engine Expired - Lifetime JP3509482B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
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Application Number Priority Date Filing Date Title
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JPH1150894A JPH1150894A (en) 1999-02-23
JP3509482B2 true JP3509482B2 (en) 2004-03-22

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* Cited by examiner, † Cited by third party
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ES2299887T3 (en) 2003-12-01 2008-06-01 Toyota Jidosha Kabushiki Kaisha PURIFICATION DEVICE FOR EXHAUST GASES OF AN INTERNAL COMBUSTION MOTOR FOR COMPRESSION.
SE0401217D0 (en) 2004-05-11 2004-05-11 Hoeganaes Ab Electrical machine and method for producing an electrical machine
JP2007255310A (en) * 2006-03-23 2007-10-04 Mitsubishi Fuso Truck & Bus Corp Exhaust emission control device
JP4665830B2 (en) * 2006-05-24 2011-04-06 トヨタ自動車株式会社 Exhaust gas purification system for internal combustion engine
JP4816599B2 (en) * 2007-09-04 2011-11-16 トヨタ自動車株式会社 Exhaust gas purification system for internal combustion engine

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