JP2001050033A - Exhaust emission control system - Google Patents

Exhaust emission control system

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Publication number
JP2001050033A
JP2001050033A JP11224911A JP22491199A JP2001050033A JP 2001050033 A JP2001050033 A JP 2001050033A JP 11224911 A JP11224911 A JP 11224911A JP 22491199 A JP22491199 A JP 22491199A JP 2001050033 A JP2001050033 A JP 2001050033A
Authority
JP
Japan
Prior art keywords
nox
exhaust gas
air
fuel ratio
adsorption catalyst
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.)
Pending
Application number
JP11224911A
Other languages
Japanese (ja)
Inventor
Toshio Manaka
敏雄 間中
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Ltd
Original Assignee
Hitachi Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Hitachi Ltd filed Critical Hitachi Ltd
Priority to JP11224911A priority Critical patent/JP2001050033A/en
Publication of JP2001050033A publication Critical patent/JP2001050033A/en
Pending legal-status Critical Current

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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

Abstract

PROBLEM TO BE SOLVED: To reduce NOx emission to zero as much as possible, which is generated abruptly during a transient period when an internal combustion engine is operated with a stoichiometric air-fuel ratio. SOLUTION: A NOx adsorption catalyst is disposed in an exhaust gas passage. When an engine is operated with a stoichiometric air-fuel ratio, a ratio is set by control to be slightly richer than the stoichiometric air-fuel ratio (an excess air ratio λ ranging from 0.97 to 1). Accordingly, since NOx generated abruptly during a transient period, when the engine is operated with the stoichiometric air-fuel ratio, is adsorbed and reduced by the NOx adsorption catalyst efficiently, an amount of NOx emission is reduced significantly.

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】本発明は自動車等の内燃機関
から排出される排気ガスを浄化する装置に係わり、特に
理論空燃比と希薄空燃比（リーンバーン）で運転可能な
内燃機関を搭載した自動車から排出される排ガスの浄化
装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for purifying exhaust gas discharged from an internal combustion engine of an automobile or the like, and more particularly to an automobile equipped with an internal combustion engine operable at a stoichiometric air-fuel ratio and a lean air-fuel ratio (lean burn). The present invention relates to a device for purifying exhaust gas discharged from a plant.

【０００２】[0002]

【従来の技術】自動車等の内燃機関から排出される排ガ
スに含まれる、一酸化炭素（ＣＯ），炭化水素(ＨＣ：H
ydrocarbon），窒素酸化物（ＮＯｘ）等は大気汚染物質
として種々の問題を生起する。そこで、従来より、これ
らの排出量低減には多大の努力が払われ、内燃機関の燃
焼方法の改善による発生量の低減に加え、排出された排
ガスを触媒等を利用して浄化する方法の開発が進めら
れ、着実な成果を挙げてきた。ガソリンエンジン車に関
しては、三元触媒なるＰｔ，Ｒｈを活性の主成分とし、
ＨＣ及びＣＯの酸化とＮＯｘの還元を同時に行って無害
化する触媒を用いる方法が主流となっている。2. Description of the Related Art Carbon monoxide (CO) and hydrocarbons (HC: H) contained in exhaust gas discharged from an internal combustion engine of an automobile or the like are used.
Hydrocarbons, nitrogen oxides (NOx), etc., cause various problems as air pollutants. So far, great efforts have been made to reduce these emissions, and in addition to reducing the amount generated by improving the combustion method of the internal combustion engine, a method of purifying the exhaust gas using a catalyst or the like has been developed. Has been promoted and has achieved steady results. For gasoline engine vehicles, the three-way catalysts Pt and Rh are the main components of the activity,
A method of using a catalyst for simultaneously oxidizing HC and CO and reducing NOx to make them harmless has become mainstream.

【０００３】ところで、三元触媒はその特性から、ウィ
ンドウと称される理論空気燃料比近傍で燃焼させて生成
した排ガスにしか効果的に作用しない。そこで従来は、
空燃比は自動車の運転状況に応じて変動するものの変動
範囲は原則として理論空燃料（ガソリンの場合Ａ（空気
の重量）／Ｆ(燃料の重量）＝約１４.７；以下本明細書
では理論空撚比をＡ／Ｆ＝１４.７ で代表させるが燃料
種によりこの数値は変る。）近傍に調節されてきた。し
かし、理論空燃比より希薄（リーン）な空燃比でエンジ
ンを運転できると燃費を向上させることができることか
ら、リーンバーン燃焼技術の開発が進められ、最近では
空燃比１８以上のリーン域で内燃機関を燃焼させる自動
車が珍しくない。しかし前述の様に現用三元触媒でリー
ンバーン排気の浄化を行わせるとＨＣ，ＣＯの酸化浄化
は行えるもののＮＯｘを効果的に還元浄化することはで
きない。したがって、リーンバーン方式の大型車への適
用、リーンバーン燃焼時間の拡大（リーンバーン方式の
適用運転域の拡大）を進めるには、リーンバーン対応排
ガス浄化技術が必要となる。そこでリーンバーン対応排
気浄化技術、すなわち酸素（Ｏ2 ）が多量に含まれる排
ガス中のＨＣ，ＮＯ，ＮＯｘを浄化する技術の開発、特
にＮＯｘを浄化する技術の開発が精力的に進められてい
る。[0003] By the way, due to its characteristics, the three-way catalyst effectively acts only on exhaust gas generated by burning near the theoretical air-fuel ratio called a window. So conventionally,
Although the air-fuel ratio fluctuates according to the driving conditions of the vehicle, the fluctuation range is, in principle, theoretical air fuel (A (weight of air) / F (weight of fuel) = about 14.7 for gasoline; The air / twist ratio is represented by A / F = 14.7, but this value varies depending on the fuel type.) However, if the engine can be operated at an air-fuel ratio leaner than the stoichiometric air-fuel ratio, the fuel efficiency can be improved. Therefore, the development of lean burn combustion technology has been promoted. It is not unusual for cars to burn gas. However, as described above, when purifying lean burn exhaust gas with the current three-way catalyst, HC and CO can be oxidized and purified, but NOx cannot be effectively reduced and purified. Therefore, in order to apply the lean burn method to a large-sized vehicle and to extend the burn time of the lean burn method (expansion of the operating range to which the lean burn method is applied), lean burn compatible exhaust gas purification technology is required. Therefore, development of lean burn compatible exhaust gas purification technology, that is, technology for purifying HC, NO, and NOx in exhaust gas containing a large amount of oxygen (O 2 ), particularly technology for purifying NOx, has been vigorously pursued. .

【０００４】特開昭63−61708 号では、リーンバーン排
ガスの上流にＨＣを供給し、排ガス中のＯ2 濃度を触媒
が有効に機能する濃度域まで低め触媒の能力を引き出す
方法が提案されている。Japanese Patent Application Laid-Open No. 63-61708 proposes a method in which HC is supplied to the upstream of lean burn exhaust gas to lower the O 2 concentration in the exhaust gas to a concentration range in which the catalyst can function effectively, thereby extracting the ability of the catalyst. I have.

【０００５】特開昭62−97630号，特開昭62−106826
号，特開昭62−117620 号では排ガス中のＮＯｘを（Ｎ
Ｏは酸化して吸収され易いＮＯ2 に変換した後）ＮＯｘ
吸収能を有する触媒と接触させて吸収除去し、吸収効率
が低下した時点で排ガスの通過を止めてＨ2 ，メタン・
ガソリン等のＨＣ、等の還元剤を用いて蓄積されたＮＯ
ｘを還元除去し、触媒のＮＯｘ吸収能を再生する方法が
示されている。JP-A-62-97630 and JP-A-62-106826
In Japanese Patent Application Laid-Open No. 62-117620, NOx in exhaust gas is
O After converted into liable NO 2 is absorbed by oxidizing) NOx
Absorption is removed by contacting with a catalyst having an absorption capacity, and when the absorption efficiency decreases, the passage of exhaust gas is stopped and H 2 , methane
NO accumulated using a reducing agent such as HC such as gasoline
A method is shown in which x is reduced and removed to regenerate the NOx absorption capacity of the catalyst.

【０００６】また、ＰＣＴ／ＪＰ９２／０１２７９及び
ＰＣＴ／ＪＰ９２／０１３３０には、排ガスがリーンの
時にＮＯｘを吸収し排ガス中の酸素濃度を低下させると
吸収したＮＯｘを放出するＮＯｘ吸収剤を排気通路に設
置し、排気ガスがリーンのときにＮＯｘを吸収させ、吸
収させたＮＯｘをＮＯｘ吸収剤に流入する排ガス中のＯ
2 濃度を低下せしめて放出させる、排気浄化装置が提案
されている。In PCT / JP92 / 01279 and PCT / JP92 / 01330, a NOx absorbent that absorbs NOx when the exhaust gas is lean and releases the absorbed NOx when the oxygen concentration in the exhaust gas is reduced is provided in the exhaust passage. NOx is absorbed when the exhaust gas is lean, and the absorbed NOx is absorbed by the exhaust gas flowing into the NOx absorbent.
2. Exhaust gas purifying devices have been proposed in which the concentration is reduced and released.

【０００７】[0007]

【発明が解決しようとする課題】特開昭63−61708 号に
おいて触媒が機能する空燃比である(Ａ／Ｆ）１４.７程
度に相当する排ガスの組成（Ｏ2濃度約０.５％程度）を
達成するには多量のＨＣが必要となる。同発明のブロー
バイガスの利用は有効であるものの、内燃機関運転中の
排ガスを処理するに十分な量ではない。燃料を投入する
ことも技術的には不可能ではないが、リーンバーン方式
で節減した燃費を低下させる結果となる。また、特開昭
62−97630号，特開昭62−106826号，特開昭62−117620
号では、ＮＯｘ吸収剤の再生にあたり排ガスの流通を停
止してＨＣ等の還元剤をＮＯｘ吸収剤に接触させるた
め、還元剤の排ガス中のＯ2 による燃焼消費が大幅に抑
制されて還元剤の使用量が激減する。しかし、ＮＯｘ吸
収剤を２つ設け、且つ、排ガスをこれらに交互に流通さ
せるための排気切り替え機構が必要で、排気処理装置の
構造が複雑になることは否定できない。THE INVENTION Problems to be Solved is a air-fuel ratio of the catalyst to function in JP 63-61708 (A / F) composition of the exhaust gas corresponding to about 14.7 (O 2 concentration of about 0.5% To achieve ()), a large amount of HC is required. Although the use of the blow-by gas of the present invention is effective, it is not sufficient to treat the exhaust gas during operation of the internal combustion engine. Injecting fuel is not technically impossible, but will result in a reduction in fuel economy, which has been saved by the lean burn method. In addition,
62-97630, JP-A-62-106826, JP-A-62-117620
The issue, for Upon regeneration of the NOx absorbent by stopping the flow of the exhaust gas a reducing agent such as HC is brought into contact with the NOx absorbent, reductant fuel consumption by O 2 in the exhaust gas is greatly suppressed reducing agent The amount of use is drastically reduced. However, an exhaust switching mechanism for providing two NOx absorbents and alternately allowing exhaust gas to flow through them is necessary, and it cannot be denied that the structure of the exhaust treatment device becomes complicated.

【０００８】さらに、ＰＣＴ／ＪＰ９２／０１２７９及
びＰＣＴ／ＪＰ９２／０１３３０では、排ガスを常時Ｎ
Ｏｘ吸収剤に流通させておき、排ガスがリーンの時にＮ
Ｏｘを吸収させ、排ガス中のＯ2 濃度を低下させて吸収
したＮＯｘを放出させて吸収剤を再生するため、排ガス
流の切り替えは不要で、上記方式の問題点は解消する。
しかし、排ガスがリーンのときにＮＯｘを吸収し排ガス
中のＯ2 濃度が低下せしめられたときにＮＯｘを放出で
きる材料の適用が前提となる。この材料の場合、ＮＯｘ
の吸収と放出を行うことは必然的に吸収剤の結晶構造の
周期的な変化を繰り返すこととなり、耐久性に対する慎
重な配慮が必要となる。また、放出NOxの処理が必要で
あり大量に放出される場合には三元触媒による後処理も
考慮する必要が生じる。Further, in PCT / JP92 / 01279 and PCT / JP92 / 01330, the exhaust gas is always N
Circulated through the Ox absorbent, and when the exhaust gas is lean,
To absorb ox, for regeneration of the absorbent by releasing the NOx absorbed by lowering the O 2 concentration in the exhaust gas, the switching of the exhaust gas flow is not required, the problems of the method will be eliminated.
However, it is premised that a material capable of absorbing NOx when the exhaust gas is lean and releasing NOx when the O 2 concentration in the exhaust gas is reduced is used. In the case of this material, NOx
Inevitably, the absorption and release of the carboxylic acid repeats a periodic change in the crystal structure of the absorbent, which requires careful attention to durability. In addition, when the released NOx needs to be treated and is released in a large amount, it is necessary to consider a post-treatment using a three-way catalyst.

【０００９】以上の従来技術ではＮＯｘ触媒の特性を活
かした理論空燃比モード運転時の空燃比制御について考
慮されていないために、理論空燃比モード運転時のＮＯ
ｘ浄化が不十分だった。In the above prior art, no consideration is given to the air-fuel ratio control in the stoichiometric air-fuel ratio mode operation utilizing the characteristics of the NOx catalyst.
x Purification was insufficient.

【００１０】本発明は、上記従来技術の問題点に鑑み、
理論空燃比モード運転時でもＮＯｘ触媒の特性を活かし
た空燃比に制御する排気浄化制御装置を提供することに
ある。The present invention has been made in view of the above-mentioned problems of the prior art,
An object of the present invention is to provide an exhaust gas purification control device that controls the air-fuel ratio by utilizing the characteristics of the NOx catalyst even during the stoichiometric air-fuel ratio mode operation.

【００１１】[0011]

【課題を解決するための手段】本発明では、理論空燃比
モード運転時の排ガス濃度を、吸着されたＮＯｘを還元
できる理論空燃比より若干濃く(空気過剰率λ０.９７か
ら１の範囲）する。これにより理論空燃比モード運転時
のＮＯｘ浄化率を著しく高めることができる。本発明に
使用されるＮＯｘ吸着触媒では、排ガス中の各成分間の
酸化還元化学量論関係において還元剤に対して酸化剤が
多い状態でＮＯｘを化学吸着し、酸化剤に対し還元剤が
同量以上の状態で吸着したＮＯｘを接触還元するＮＯｘ
吸着触媒を排ガス流路に配置し、排ガス中の各成分間の
酸化還元化学量論関係において還元剤に対して酸化剤が
多い状態をつくって吸着触媒上にＮＯｘを化学吸着さ
せ、次に酸化剤に対し還元剤が同量以上の状態をつく
り、吸着触媒上に吸着したNOxを還元剤と接触反応させ
てＮ2 に還元して無害化する。According to the present invention, the exhaust gas concentration during operation in the stoichiometric air-fuel ratio mode is made slightly higher than the stoichiometric air-fuel ratio capable of reducing adsorbed NOx (range from excess air ratio λ 0.97 to 1). . Thus, the NOx purification rate during the stoichiometric air-fuel ratio mode operation can be significantly increased. In the NOx adsorption catalyst used in the present invention, NOx is chemically adsorbed in a state where the oxidizing agent is large relative to the reducing agent in the oxidation-reduction stoichiometry relationship between the components in the exhaust gas, and the reducing agent is the same as the oxidizing agent. NOx that catalytically reduces NOx adsorbed in excess of the amount
An adsorption catalyst is placed in the exhaust gas channel, and in the redox stoichiometry relationship between the components in the exhaust gas, a state in which the oxidizing agent is large relative to the reducing agent is made to chemically adsorb NOx on the adsorption catalyst, and then oxidize. The reducing agent makes a state in which the amount of the reducing agent is equal to or more than that of the agent, and NOx adsorbed on the adsorption catalyst is brought into contact with the reducing agent to be reduced to N 2 and made harmless.

【００１２】ここで吸着触媒は、ＮＯｘ等の物質を吸着
する能力を持ち同時に触媒機能を持つ材料を指す。本発
明では、ＮＯｘを吸着して捕捉する能力とＮＯｘを接触
的に還元する能力及びＨＣ，ＣＯ等を接触的に酸化する
能力を持つ材料を指す。Here, the adsorption catalyst refers to a material that has the ability to adsorb substances such as NOx and also has a catalytic function. In the present invention, it refers to a material having an ability to adsorb and capture NOx, an ability to catalytically reduce NOx, and an ability to catalytically oxidize HC, CO, and the like.

【００１３】また、酸化剤はＯ2 ，ＮＯ，ＮＯ2 等で主
として酸素である。還元剤は、内燃機関に供されたＨ
Ｃ，燃焼過程で生成するその派生物としてＨＣ（含む含
酸素炭化水素），ＣＯ，Ｈ2 等、さらには、後述の還元
成分として排ガス中に添加されるＨＣ等の還元性物質で
ある。The oxidizing agent is O 2 , NO, NO 2 and the like, and is mainly oxygen. The reducing agent was H supplied to the internal combustion engine.
C is a reducing substance such as HC (containing oxygen-containing hydrocarbon), CO, H 2 or the like as a derivative thereof generated in the combustion process, and HC added to exhaust gas as a reducing component described later.

【００１４】前述のように、リーン排ガスとＮＯｘを窒
素にまで還元するための還元剤としてのＨＣ，ＣＯ，Ｈ
2等とを接触させるとこれらは排ガス中の酸化剤として
のＯ2と燃焼反応を起こす。ＮＯｘ（ＮＯ及びＮＯ2 ）
もこれらと反応して窒素に還元される。通常は両反応が
平行して進行するため酸素の共存下では還元剤の利用率
が低い。特に反応温度が（触媒材料にも依るが）５００
℃以上の高温では後者の割合がかなり大きくなる。そこ
で、ＮＯｘを吸着触媒で排ガスから分離し（少なくとも
排ガス中のＯ2 から分離し）しかる後に還元剤と接触反
応させることによりＮＯｘのＮ2 への還元を効果的に行
うことが可能となる。本発明では、ＮＯｘ吸着触媒によ
りリーン排ガス中のＮＯｘを吸着除去することにより排
ガス中のＮＯｘをＯ2 から分離する。As described above, HC, CO, and H as reducing agents for reducing lean exhaust gas and NOx to nitrogen.
When they come into contact with 2 etc., they cause a combustion reaction with O 2 as an oxidizing agent in the exhaust gas. NOx (NO and NO 2 )
Also reacts with these to be reduced to nitrogen. Usually, the utilization of the reducing agent is low in the presence of oxygen because both reactions proceed in parallel. Especially when the reaction temperature is 500 (depending on the catalyst material)
At a high temperature of ℃ or more, the ratio of the latter becomes considerably large. Therefore, NOx is separated from the exhaust gas in the adsorber (separated from O 2 at least in the exhaust gas) it is possible to perform reduction to N 2 in the NOx effectively by catalytic reaction with a reducing agent thereafter. In the present invention, NOx in lean exhaust gas is adsorbed and removed by the NOx adsorption catalyst to separate NOx in exhaust gas from O 2 .

【００１５】本発明に用いられるＮＯｘ吸着触媒におい
ては、次に、排ガス中の酸化剤(Ｏ2，ＮＯｘ等）と還元
剤（ＨＣ，ＣＯ，Ｈ2 等）で構成される酸化還元系にお
いて還元剤が同量かもしくは卓越する状態をつくり、吸
着触媒上に吸着したＮＯｘをＨＣ等の還元剤と接触反応
させてＮ2 に還元する。Next, in the NOx adsorption catalyst used in the present invention, reduction is performed in an oxidation-reduction system composed of an oxidizing agent (O 2 , NOx, etc.) and a reducing agent (HC, CO, H 2, etc.) in the exhaust gas. When the amount of the agent is equal or excellent, NOx adsorbed on the adsorption catalyst is brought into contact with a reducing agent such as HC to reduce it to N 2 .

【００１６】ところで排ガス中のＮＯｘはほぼＮＯとＮ
Ｏ2 からなる。ＮＯ2 はＮＯに比べて反応性に富む。し
たがってＮＯ2 の吸着除去と還元はＮＯよりも容易であ
る。したがってＮＯをＮＯ2 に酸化すれば排ガス中のＮ
Ｏｘの吸着除去と還元が容易となる。本発明はリーン排
ガス中のＮＯｘを共存するＯ2 によりＮＯ2 に酸化し除
去する方法、そのための酸化手段例えば吸着触媒にＮＯ
酸化機能を持たせることをも包含するものである。By the way, NOx in exhaust gas is almost NO and N
Consists of O 2 . NO 2 is more reactive than NO. Therefore, adsorption removal and reduction of NO 2 are easier than NO. Therefore, if NO is oxidized to NO 2 , N
Adsorption removal and reduction of Ox are facilitated. The present invention is a method of removing oxidized to NO 2 by O 2 coexist NOx in lean exhaust gas, NO oxidation means such as adsorption catalyst therefor
It also includes having an oxidizing function.

【００１７】本発明のＮＯｘ吸着触媒における、化学吸
着したＮＯｘの還元反応はおおよそ以下の反応式で記述
できる。The reduction reaction of chemically adsorbed NOx in the NOx adsorbing catalyst of the present invention can be approximately described by the following reaction formula.

【００１８】Ｍ−ＮＯ3＋ＨＣ→ＭＯ＋Ｎ2 ＋ＣＯ2 ＋
Ｈ2Ｏ→ＭＣＯ3 ＋Ｎ2 ＋Ｈ2Ｏ ここに、Ｍは金属元素 （還元生成物にＭＣＯ3 を採用した理由は後述する） 上記の反応は発熱反応である。金属Ｍとしてアルカリ金
属とアルカリ土類金属を取り上げ、それぞれＮａ及びＢ
ａを代表させて反応熱を評価すると標準状態（１気圧，
２５℃）では以下となる。M-NO 3 + HC → MO + N 2 + CO 2 +
H 2 O → MCO 3 + N 2 + H 2 O Here, M is a metal element (the reason why MCO 3 is used as a reduction product will be described later). The above reaction is an exothermic reaction. Alkali metals and alkaline earth metals are taken as metals M, Na and B respectively.
When the reaction heat is evaluated as a representative, the standard state (1 atm,
(25 ° C.) is as follows.

【００１９】 ２ＮａＮＯ3(ｓ)＋５／９Ｃ3Ｈ6→Ｎａ2ＣＯ3(ｓ)＋Ｎ2 ＋２／３ＣＯ2 ＋５／３Ｈ2Ｏ ［−ΔＨ＝８７３kjule／mole］ Ｂａ(ＮＯ3)2＋５／９Ｃ3Ｈ6→ＢａＣＯ3(ｓ)＋Ｎ2 ＋２／３ＣＯ2 ＋５／３Ｈ2Ｏ ［−ΔＨ＝７５１kjule／mole］ ここに、ｓ：固体 ｇ：気体 吸着種の熱力学量には相当する固体の値を用いた。2NaNO 3 (s) + 5 / 9C 3 H 6 → Na 2 CO 3 (s) + N 2 + 2 / 3CO 2 + 5 / 3H 2 O [−ΔH = 873 kjule / mole] Ba (NO 3 ) 2 + 5 / 9C 3 H 6 → BaCO 3 (s) + N 2 + 2 / 3CO 2 + 5 / 3H 2 O [−ΔH = 751 kjule / mole] Here, s: solid g: gas The thermodynamic quantity of the adsorbed species used was the value of the corresponding solid.

【００２０】ちなみにＣ3Ｈ6５／９moleの燃焼熱は１０
７０kjule であり、上記各反応はＨＣの燃焼熱に匹敵す
る発熱量である。当然のことながらこの発熱は接触する
排ガスに伝えられ吸着触媒表面の局部的な温度上昇は抑
制される。The heat of combustion of C 3 H 6 5/9 mole is 10
Each reaction has a calorific value comparable to the heat of combustion of HC. Naturally, this heat generation is transmitted to the contacting exhaust gas, and a local temperature rise on the surface of the adsorption catalyst is suppressed.

【００２１】ＮＯｘの捕捉剤がＮＯｘ吸収剤の場合、吸
収剤のバルク内に捕捉されたＮＯｘも還元されるため発
熱量は大きくなり、排ガスへの伝達には限度があるため
吸収剤の温度上昇をもたらす。この発熱は下式に示す吸
収反応の平衡を放出側にずらす（左側が放出、右側が吸
収）。When the NOx trapping agent is a NOx absorbent, the calorific value increases because NOx trapped in the bulk of the absorbent is also reduced, and the temperature of the absorbent rises because transmission to exhaust gas is limited. Bring. This exotherm shifts the equilibrium of the absorption reaction shown below to the emission side (emission on the left and absorption on the right).

【００２２】ＭＣＯ3(ｓ)＋２ＮＯ2 ＋１／２Ｏ2 ←→
Ｍ(ＮＯ3)2＋ＣＯ2 放出したＮＯｘを速やかに還元して装置外へ排出される
排ガス中のＮＯｘ濃度を低減すべく還元剤の濃度を高め
ても、気相においてはＮＯ2 とＨＣの反応はあまり進ま
ない。したがって、還元剤の増量でＮＯｘ放出量を十分
に減ずることができない可能性がある。また、ＮＯｘ吸
収量が少ない段階で還元反応による操作を行うことも考
えられるが、ＮＯｘ吸収剤の再生頻度が増し、燃費向上
効果を抑制することになる。MCO 3 (s) + 2NO 2 + ／ O 2 ← →
M (NO 3 ) 2 + CO 2 Even if the concentration of the reducing agent is increased in order to reduce the NOx released from the apparatus quickly to reduce the NOx released, the NO 2 and HC in the gas phase are reduced. The reaction does not progress very much. Therefore, there is a possibility that the NOx emission amount cannot be sufficiently reduced by increasing the amount of the reducing agent. It is also conceivable to perform the operation by the reduction reaction at the stage where the NOx absorption amount is small, but the frequency of regeneration of the NOx absorbent increases, and the effect of improving the fuel efficiency is suppressed.

【００２３】本発明に用いられる吸着触媒は、その表面
近傍でのみＮＯｘを捕捉するため発熱の絶対量としては
少なく、且つ速やかに排ガスに伝達されるため吸着触媒
の温度上昇は少ない。したがって一旦捕捉したＮＯｘの
放出を防止することができる。The adsorption catalyst used in the present invention captures NOx only in the vicinity of its surface, so that the absolute amount of heat generation is small, and the temperature of the adsorption catalyst is small because it is quickly transmitted to exhaust gas. Therefore, release of the trapped NOx can be prevented.

【００２４】本発明に用いられるＮＯｘ吸着触媒は、Ｎ
Ｏｘをその表面で化学吸着により捕捉しＮＯｘの還元に
際しての発熱反応でＮＯｘの放出を生起しない材料とし
て特徴付けられる。また、本発明に用いられるＮＯｘ吸
着触媒は、ＮＯｘをその表面で化学吸着によりもしくは
表面近傍で化学結合により捕捉し、ＮＯｘの還元に際し
ての発熱反応でＮＯｘの放出を生起しない材料として特
徴付けられる。The NOx adsorption catalyst used in the present invention is N
It is characterized as a material that captures Ox on its surface by chemisorption and does not release NOx by an exothermic reaction upon reduction of NOx. Further, the NOx adsorption catalyst used in the present invention is characterized as a material that captures NOx by chemical adsorption on its surface or by chemical bonding near the surface, and does not cause release of NOx due to an exothermic reaction upon reduction of NOx.

【００２５】本出願人は、少なくともカリウム（Ｋ），
ナトリウム（Ｎａ），マグネシウム（Ｍｇ），ストロン
チウム（Ｓｒ）及びカルシウム（Ｃａ）から選ばれる一
種以上の元素を成分の一部として含むＮＯｘ吸着触媒で
上記特徴を実現し得ることを見出している。The applicant has at least potassium (K),
It has been found that the above characteristics can be realized by a NOx adsorption catalyst containing at least one element selected from sodium (Na), magnesium (Mg), strontium (Sr) and calcium (Ca) as a part of the components.

【００２６】本発明が適用される内燃機関の排ガス浄化
装置は、少なくともカリウム(Ｋ),ナトリウム（Ｎ
ａ），マグネシウム（Ｍｇ），ストロンチウム（Ｓｒ）
及びカルシウム（Ｃａ）から選ばれる一種以上の元素を
成分の一部として含むＮＯｘ吸着触媒を排ガス流路に配
置し、排ガス中の各成分間の酸化還元化学量論関係にお
いて還元剤に対して酸化剤が多い状態をつくって吸着触
媒上にＮＯｘを化学吸着させ、次に酸化剤に対し還元剤
が同量以上の状態をつくり、吸着触媒上に吸着したＮＯ
ｘを還元剤と接触反応させてＮ2 に還元して無害化す
る。The exhaust gas purifying apparatus for an internal combustion engine to which the present invention is applied includes at least potassium (K), sodium (N
a), magnesium (Mg), strontium (Sr)
A NOx adsorption catalyst containing at least one element selected from calcium and calcium (Ca) as a part of a component is disposed in an exhaust gas channel, and oxidizes a reducing agent in a redox stoichiometric relationship between components in the exhaust gas. NOx is chemisorbed on the adsorption catalyst by creating a state in which the amount of the agent is large, and then the state in which the amount of the reducing agent is equal to or more than that of the oxidizing agent is created, and the NO adsorbed on the adsorption catalyst is formed.
x is contacted with a reducing agent to reduce it to N 2 and render it harmless.

【００２７】また、本発明が適用される内燃機関の排ガ
ス浄化装置は、少なくともカリウム（Ｋ），ナトリウム
（Ｎａ），マグネシウム（Ｍｇ），ストロンチウム（Ｓ
ｒ）及びカルシウム（Ｃａ）から選ばれる一種以上の元
素を成分の一部として含むＮＯｘ吸着触媒を排ガス流路
に配置し、酸化還元化学量論関係においてＨＣ等の還元
剤に対してＯ2 等の酸化剤が多い状態をつくって吸着触
媒表面及び表面近傍にＮＯｘを化学結合により捕捉し、
次に酸化剤に対し還元剤が同量かもしくは多い状態をつ
くり、吸着触媒に捕捉されたＮＯｘを還元剤と接触反応
させてＮ2 に還元して無害化する。The exhaust gas purifying apparatus for an internal combustion engine to which the present invention is applied includes at least potassium (K), sodium (Na), magnesium (Mg), strontium (S
The NOx adsorbing catalyst disposed in the exhaust gas line comprising one or more elements selected from r) and calcium (Ca) as part of component, O 2 or the like to a reducing agent such as HC in a redox stoichiometry NOx is trapped on the surface of the adsorption catalyst and near the surface by chemical bonding,
Next, a state in which the amount of the reducing agent is equal to or larger than that of the oxidizing agent is created, and the NOx trapped by the adsorption catalyst is caused to contact with the reducing agent to be reduced to N 2 to be harmless.

【００２８】本発明に用いられるＮＯｘ吸着触媒として
は特に以下が好適に適用できる。As the NOx adsorption catalyst used in the present invention, the following can be particularly preferably applied.

【００２９】カリウム（Ｋ），ナトリウム（Ｎａ），マ
グネシウム（Ｍｇ），ストロンチウム（Ｓｒ）及びカル
シウム（Ｃａ）から選ばれる少なくとも一種と、セリウ
ム等からなる希土類から選ばれる少なくとも一種と、白
金，ロジウム，パラジウム等からなる貴金属から選ばれ
る少なくとも一種の元素を含む、金属および金属酸化物
（もしくは複合酸化物）からなる組成物、該組成物を多
孔質耐熱性金属酸化物に担持してなる組成物。本組成物
は、優れたＮＯｘ吸着能に加え優れた耐ＳＯｘ性を有す
る。At least one selected from potassium (K), sodium (Na), magnesium (Mg), strontium (Sr) and calcium (Ca), and at least one selected from rare earths such as cerium, platinum, rhodium, A composition comprising a metal and a metal oxide (or composite oxide) containing at least one element selected from precious metals such as palladium, and a composition comprising the composition supported on a porous heat-resistant metal oxide. The composition has excellent SOx resistance in addition to excellent NOx adsorption ability.

【００３０】本発明における、酸化剤に対し還元剤が同
量かもしくは多い状態は以下の方法で作ることができ
る。In the present invention, the state in which the amount of the reducing agent is equal to or larger than that of the oxidizing agent can be produced by the following method.

【００３１】内燃機関における燃焼条件を理論空燃比も
しくは燃料過剰（リッチ）とする。また、リーンバーン
排ガスに還元剤を添加する。The combustion conditions in the internal combustion engine are set to the stoichiometric air-fuel ratio or excess fuel (rich). Further, a reducing agent is added to the lean burn exhaust gas.

【００３２】前者は以下の方法で達成することができ
る。The former can be achieved by the following method.

【００３３】排気ダクトに設けられた酸素濃度センサー
出力及び吸気流量センサー出力等に応じて燃料噴射量を
制御する方法。本法では、複数の気筒の一部を燃料過剰
とし残部を燃料不足とし、全気筒からの混合排ガス中の
成分が酸化還元化学量論関係において酸化剤に対して還
元剤が同量かもしくは多い状態をつくる方法をも含む。A method of controlling the fuel injection amount according to the output of an oxygen concentration sensor and the output of an intake flow sensor provided in an exhaust duct. In this method, a part of the plurality of cylinders is made excessive and the remaining fuel is made insufficient, and the components in the mixed exhaust gas from all the cylinders have the same amount or larger amount of the reducing agent than the oxidizing agent in the oxidation-reduction stoichiometry relationship. Includes methods for creating states.

【００３４】後者は以下の各方法で達成することができ
る。The latter can be achieved by the following methods.

【００３５】排ガス流の吸着触媒上流に還元剤を投入す
る方法。還元剤には内燃機関の燃料としてのガソリン，
軽油，灯油，天然ガス、これらの改質物，水素，アルコ
ール類，アンモニア等が適用できる。A method of introducing a reducing agent upstream of the adsorption catalyst in the exhaust gas stream. Gasoline as fuel for internal combustion engine
Light oil, kerosene, natural gas, their reformed products, hydrogen, alcohols, ammonia and the like can be applied.

【００３６】ブローバイガス及びキャニスターパージガ
スを吸着触媒上流に導きこれらに含まれる炭化水素等の
還元剤を投入することも有効である。燃料直噴式内燃機
関においては、排気行程で燃料を噴射し還元剤としての
燃料を投入することが有効である。It is also effective to introduce the blow-by gas and the canister purge gas upstream of the adsorption catalyst and to introduce a reducing agent such as a hydrocarbon contained therein. In a fuel direct injection type internal combustion engine, it is effective to inject fuel during an exhaust stroke and to input fuel as a reducing agent.

【００３７】本発明に用いられる吸着触媒は、各種の形
状で適用することができる。コージェライト，ステンレ
ス等の金属材料からなるハニカム状構造体に吸着触媒成
分をコーティングして得られるハニカム形状を始めと
し、ペレット状，板状，粒状，粉末として適用できる。The adsorption catalyst used in the present invention can be applied in various shapes. The present invention can be applied as a pellet, plate, granule, or powder, including a honeycomb shape obtained by coating a honeycomb-like structure made of a metal material such as cordierite or stainless steel with an adsorption catalyst component.

【００３８】本発明における、酸化剤に対し還元剤が同
量かもしくは多い状態を作るタイミングは以下の各方法
によることができる。In the present invention, the timing for forming the state in which the amount of the reducing agent is equal to or larger than that of the oxidizing agent can be determined by the following methods.

【００３９】（１）ＥＣＵ(Engine Control Unit）で決
定される空燃比設定信号，エンジン回転数信号，吸入空
気量信号，吸気管圧力信号，速度信号，スロットル開
度，排ガス温度等からリーン運転時におけるＮＯｘ排出
量を推定し、その積算値が所定の設定値を超えたとき。(1) During lean operation, an air-fuel ratio setting signal, an engine speed signal, an intake air amount signal, an intake pipe pressure signal, a speed signal, a throttle opening, an exhaust gas temperature, etc., determined by an ECU (Engine Control Unit). Is estimated when the integrated value exceeds a predetermined set value.

【００４０】（２）排気流路の吸着触媒上流または後流
に置かれた酸素センサー（もしくはＡ／Ｆセンサー）の
信号により累積酸素量を検出し累積酸素量が所定の量を
超えたとき。その変形態様として、リーン運転時の累積
酸素量が所定の量を超えたとき。(2) When the accumulated oxygen amount is detected by a signal from an oxygen sensor (or A / F sensor) placed upstream or downstream of the adsorption catalyst in the exhaust passage, and the accumulated oxygen amount exceeds a predetermined amount. As a variation thereof, when the accumulated oxygen amount during the lean operation exceeds a predetermined amount.

【００４１】（３）排気流路の吸着触媒上流に置かれた
ＮＯｘセンサー信号により累積ＮＯｘ量を算出し、リー
ン運転時における累積ＮＯｘ量が所定の量を超えたと
き。(3) When the accumulated NOx amount is calculated from the NOx sensor signal placed upstream of the adsorption catalyst in the exhaust passage, and the accumulated NOx amount during the lean operation exceeds a predetermined amount.

【００４２】（４）排気流路の吸着触媒後流に置かれた
ＮＯｘセンサーの信号によりリーン運転時におけるＮＯ
ｘ濃度を検出し、ＮＯｘ濃度が所定濃度を超えたとき。
または吸着触媒の上流，下流の両方に置かれたＮＯｘセ
ンサの信号により、ＮＯｘ浄化率を求め、そのＮＯｘ浄
化率が所定値以下になったとき。(4) NO during lean operation is determined by a signal from a NOx sensor placed downstream of the adsorption catalyst in the exhaust passage.
When the x concentration is detected and the NOx concentration exceeds a predetermined concentration.
Alternatively, the NOx purification rate is obtained from the signals of NOx sensors placed both upstream and downstream of the adsorption catalyst, and when the NOx purification rate falls below a predetermined value.

【００４３】（５）ＮＯｘ吸着触媒に吸着されたＮＯｘ
吸着量，排気温度，該吸着触媒の温度，硫黄被毒量，車
の走行距離，触媒の劣化度，空燃比，未燃炭化水素の濃
度，触媒前のＮＯｘ濃度，ストイキ（理論空燃比）また
はリッチ運転からリーン運転に変化した時からのリーン
運転経過時間，内燃機関の回転数，該機関の負荷，吸入
空気量，排ガス量のいずれかひとつ以上の状態量からＮ
Ｏｘ吸着触媒のＮＯｘ浄化率を推定し、その推定された
ＮＯｘ浄化率が所定値以下になったとき。(5) NOx adsorbed on the NOx adsorption catalyst
Adsorption amount, exhaust temperature, temperature of the adsorption catalyst, sulfur poisoning amount, travel distance of the vehicle, degree of catalyst deterioration, air-fuel ratio, unburned hydrocarbon concentration, NOx concentration before the catalyst, stoichiometric (stoichiometric air-fuel ratio) or From the state quantity of any one or more of the lean operation elapsed time from the time of the change from the rich operation to the lean operation, the number of revolutions of the internal combustion engine, the load of the engine, the intake air amount, and the exhaust gas amount, N
When the NOx purification rate of the Ox adsorption catalyst is estimated, and when the estimated NOx purification rate falls below a predetermined value.

【００４４】本発明における、酸化剤に対し還元剤が同
量かもしくは多い状態を維持する時間もしくは維持すべ
く投入する還元剤量は、前述のごとく、予め吸着触媒の
特性，内燃機関の諸元と特性等を考慮して決めることが
できるが、これらは、燃料噴射弁からシリンダに供給す
る噴射量を増加したり、内燃機関の膨張行程中に筒内噴
射したり、排気管内に燃料を供給することで実現でき
る。また、理論空燃比モード運転しか行わない場合でも
理論空燃比より若干濃い値(空気過剰率λ０.９７から１
の範囲）に制御することにより、過渡運転時のスパイク
状に発生したNOxがＮＯｘ触媒により効率よく吸着，還
元されるため、ＮＯｘ排出量が著しく低減される。In the present invention, as described above, the time for maintaining the state in which the amount of the reducing agent is equal to or larger than the amount of the oxidizing agent or the amount of the reducing agent to be charged is, as described above, the characteristics of the adsorption catalyst and the specifications of the internal combustion engine. These characteristics can be determined in consideration of the characteristics of the fuel injection valve, such as increasing the injection amount supplied from the fuel injection valve to the cylinder, injecting fuel into the cylinder during the expansion stroke of the internal combustion engine, or supplying fuel into the exhaust pipe. It can be realized by doing. Even when only the stoichiometric air-fuel ratio mode operation is performed, a value slightly higher than the stoichiometric air-fuel ratio (excess air ratio λ 0.97 to 1
, The NOx generated in a spike during the transient operation is efficiently adsorbed and reduced by the NOx catalyst, so that the NOx emission amount is significantly reduced.

【００４５】[0045]

【発明の実施の形態】本発明の具体的実施態様を挙げて
本発明を詳細に説明する。なお、本発明は以下の実施態
様及び実施例に限定されるものでなく、その思想範囲内
において各種の実施態様があることは言うまでもない。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to specific embodiments of the present invention. The present invention is not limited to the following embodiments and examples, and it goes without saying that there are various embodiments within the scope of the idea.

【００４６】［吸着触媒］本発明の方法による吸着触媒
の特性について説明する。アルカリ金属としてＮａを含
むＮ−Ｎ９とＫを含むＮ−Ｋ９の特性は次の様である。[Adsorption Catalyst] The characteristics of the adsorption catalyst according to the method of the present invention will be described. The characteristics of N-N9 containing Na as an alkali metal and NK9 containing K are as follows.

【００４７】《吸着触媒調製法》吸着触媒Ｎ−Ｎ９を以
下の方法で得た。<< Preparation method of adsorption catalyst >> An adsorption catalyst N-N9 was obtained by the following method.

【００４８】アルミナ粉末とベーマイトを硝酸邂逅して
得たバインダーとしてのアルミナゾルを混合し硝酸酸性
アルミナスラリーを得た。該コーティング液にハニカム
を浸漬した後速やかに引き上げ、セル内に閉塞した液を
エアーブローして除去した後、乾燥、続いて４５０℃で
焼成した。この操作を繰り返しハニカムの見掛け容積１
Ｌあたり１５０ｇのアルミナをコーティングした。該ア
ルミナコートハニカムに触媒活性成分担持しハニカム状
吸着触媒を得た。例えば、硝酸セリウム（硝酸Ｃｅ）溶
液を含浸し乾燥後６００℃で１時間焼成した。続いて硝
酸ナトリウム（硝酸Ｎａ）溶液とチタニアゾル溶液と硝
酸マグネシウム（硝酸Ｍｇ）溶液の混合溶液を含浸し、
同様に乾燥，焼成した。さらにジニトジアンミンＰｔ硝
酸溶液と硝酸ロジウム（硝酸Ｒｈ）溶液の混合溶液に含
浸し、乾燥後４５０℃で１時間焼成した。最後に硝酸Ｍ
ｇ溶液を含浸し４５０℃で１時間焼成した。以上により
アルミナ（Ａｌ2Ｏ3）にＣｅ，Ｍｇ，Ｎａ，Ｔｉ，Ｒ
ｈ，Ｐｔを担持したハニカム状吸着触媒，２Ｍｇ−(０.
２Ｒｈ，２.７Ｐｔ)−(１８Ｎａ，４Ｔｉ，２Ｍｇ)−２
７Ｃｅ／Ａｌ2Ｏ3を得た。ここで、／Ａｌ2Ｏ3は活性成
分がＡｌ2Ｏ3上に担持されたことを示し、元素記号前の
数値はハニカム見掛け容積１Ｌ当たりに担持した表示金
属成分の重量（ｇ）である。表記順序は担持順序を示し
ており、Ａｌ2Ｏ3に近く表記される成分から離れる成分
の順で担持し、（ ）で括られた成分は同時に担持し
た。ちなみに各活性成分の担持量は含浸溶液中の活性成
分濃度を変化させることにより変えることができる。An alumina sol as a binder obtained by mixing alumina powder and boehmite with nitric acid was mixed to obtain a nitric acid acidic alumina slurry. After dipping the honeycomb in the coating liquid, the honeycomb was immediately pulled up, the liquid blocked in the cell was removed by air blow, dried, and subsequently fired at 450 ° C. By repeating this operation, the apparent volume of the honeycomb 1
150 g of alumina were coated per liter. A catalytically active component was carried on the alumina-coated honeycomb to obtain a honeycomb-shaped adsorption catalyst. For example, it was impregnated with a cerium nitrate (Ce nitrate) solution, dried, and fired at 600 ° C. for 1 hour. Subsequently, a mixed solution of a sodium nitrate (Na nitrate) solution, a titania sol solution, and a magnesium nitrate (Mg nitrate) solution is impregnated,
It was dried and fired similarly. Furthermore, the mixture was impregnated with a mixed solution of a dinitodiamine Pt nitric acid solution and a rhodium nitrate (Rh nitrate) solution, dried, and baked at 450 ° C. for 1 hour. Finally, nitric acid M
g solution and impregnated at 450 ° C. for 1 hour. Thus, Ce, Mg, Na, Ti, R are added to alumina (Al 2 O 3 ).
h, Pt-supported honeycomb-shaped adsorption catalyst, 2Mg- (0.
2Rh, 2.7Pt)-(18Na, 4Ti, 2Mg) -2
7 Ce / Al 2 O 3 was obtained. Here, / Al 2 O 3 indicates that the active component was supported on Al 2 O 3 , and the numerical value before the element symbol is the weight (g) of the indicated metal component supported per 1 L of apparent honeycomb volume. The notation order indicates the order in which the components are carried, and the components separated from the components near Al 2 O 3 are carried in order, and the components enclosed in parentheses are carried simultaneously. Incidentally, the loading amount of each active ingredient can be changed by changing the active ingredient concentration in the impregnating solution.

【００４９】吸着触媒Ｎ−Ｋ９を以下の方法で調製し
た。The adsorption catalyst NK9 was prepared by the following method.

【００５０】吸着触媒Ｎ−Ｎ９調製における硝酸Ｎａ溶
液に代わり硝酸カリウム（硝酸Ｋ）溶液を用い、その他
は吸着触媒Ｎ−Ｎ９同様の方法でＮ−Ｋ９ ２Ｍｇ−
（０.２Ｒｈ，２.７Ｐｔ）−（１８Ｋ，４Ｔｉ，２Ｍ
ｇ）−２７Ｃｅ／Ａｌ2Ｏ3を得た。また同様の方法で比
較触媒Ｎ−Ｒ２ ２Ｍｇ−(０.２Ｒｈ，２.７Ｐｔ)−２
７Ｃｅ／Ａｌ2Ｏ3を得た。A potassium nitrate (K nitrate) solution was used in place of the sodium nitrate solution in the preparation of the adsorption catalyst N-N9, and the other steps were the same as those for the adsorption catalyst N-N9.
(0.2Rh, 2.7Pt)-(18K, 4Ti, 2M
It was obtained g) -27Ce / Al 2 O 3 . In the same manner, the comparative catalyst NR2 2Mg- (0.2Rh, 2.7Pt) -2 was used.
7 Ce / Al 2 O 3 was obtained.

【００５１】《性能評価法》上記方法で得た吸着触媒を
７００℃で５時間酸化雰囲気で熱処理した後、以下の方
法で特性を評価した。<< Performance Evaluation Method >> The adsorption catalyst obtained by the above method was heat-treated at 700 ° C. for 5 hours in an oxidizing atmosphere, and then its characteristics were evaluated by the following methods.

【００５２】排気量１.８Ｌ のリーンバーン仕様ガソリ
ンエンジンを搭載した乗用車に本発明の方法により調製
した容積１.７Ｌ のハニカム状吸着触媒を搭載しＮＯｘ
浄化特性を評価した。A 1.7-liter honeycomb-shaped adsorption catalyst prepared by the method of the present invention was mounted on a passenger car equipped with a 1.8-liter lean burn gasoline engine, and NOx
The purification properties were evaluated.

【００５３】《吸着触媒の特性》吸着触媒Ｎ−Ｎ９を搭
載し、Ａ／Ｆ＝１３.３ のリッチ運転３０秒間とＡ／Ｆ
＝２２のリーン運転約２０分間（ＮＯｘ浄化率が約４０
％まで低下するまでの時間）を交互に繰り返し図２のＮ
Ｏｘ浄化率経時特性を得た。同図から本吸着触媒により
リーン運転期間中のＮＯｘが浄化されることが伺える。
リーン運転中NOx浄化率は徐々に低下し初期に１００％
あった浄化率は経過時間とともに約４０％となる。しか
しこの低下した浄化率は３０秒間のリッチ運転や機関の
膨張行程または排気行程中のシリンダ内燃料噴射で１０
０％にまで回復する。再びリーン運転を行うとＮＯｘ浄
化能は回復して前述のＮＯｘ浄化率の低下を繰り返す。
リーン運転とリッチ運転を複数回繰り返した場合、リー
ン運転中のＮＯｘ浄化率の低下の速度は触媒温度，硫黄
被毒量，車の走行距離，触媒入口のＮＯｘ濃度，排ガス
量により変化する。したがって、それらの運転状態に応
じてＮＯｘ浄化率を精度よく推定することが重要であ
る。<< Characteristics of Adsorption Catalyst >> The adsorbent catalyst N-N9 is mounted, and the A / F = 13.3 rich operation for 30 seconds and the A / F
= 22 lean operation for about 20 minutes (NOx purification rate is about 40
%) Is alternately repeated.
Ox purification rate aging characteristics were obtained. From the figure, it can be seen that the present adsorption catalyst purifies NOx during the lean operation period.
NOx purification rate gradually decreases during lean operation to 100% in the initial stage
The resulting purification rate becomes approximately 40% over time. However, this reduced purification rate is 10 times during the rich operation for 30 seconds or the fuel injection in the cylinder during the expansion stroke or the exhaust stroke of the engine.
Recovers to 0%. When the lean operation is performed again, the NOx purification ability is restored, and the above-described decrease in the NOx purification rate is repeated.
When the lean operation and the rich operation are repeated a plurality of times, the rate of decrease in the NOx purification rate during the lean operation varies depending on the catalyst temperature, sulfur poisoning amount, vehicle travel distance, NOx concentration at the catalyst inlet, and exhaust gas amount. Therefore, it is important to accurately estimate the NOx purification rate in accordance with these operating conditions.

【００５４】車速を約４０ｋｍ／ｈ一定（排ガスの空間
速度(ＳＶ)約２０,０００／ｈ一定)とし点火時期を変化
させて排ガス中のＮＯｘ濃度を変え、ＮＯｘ濃度とリー
ン排ガス中のＮＯｘ浄化率の関係を求めて図３を得た。
ＮＯｘ浄化率は経時的に低下するがＮＯｘ濃度が低いほ
ど低下速度は小さい。また、吸着量が飽和したと考えら
れる経過時間後もＮＯｘ浄化率は２２〜２５％に維持さ
れており、ＮＯｘがある程度直接Ｎ2 に還元されている
ことがわかる。ＮＯｘ浄化率５０％及び３０％に至るま
でに捕捉されたＮＯｘ量を同図から求めると表１とな
る。The vehicle speed is kept constant at about 40 km / h (the exhaust gas space velocity (SV) is kept constant at about 20,000 / h), and the ignition timing is changed to change the NOx concentration in the exhaust gas, thereby purifying the NOx concentration and the NOx purification in the lean exhaust gas. Figure 3 was obtained by determining the relationship between the rates.
The NOx purification rate decreases with time, but the lower the NOx concentration, the lower the rate of decrease. Also, the NOx purification rate after the elapsed time is considered to adsorption is saturated is maintained at 22 to 25%, it can be seen that NOx is reduced to some extent directly N 2. Table 1 shows the amounts of NOx trapped up to the NOx purification rates of 50% and 30% from the figure.

【００５５】[0055]

【表１】 [Table 1]

【００５６】ＮＯｘ捕捉量はＮＯｘ濃度に依らずほぼ一
定である。吸着量が吸着質の濃度（圧力）に寄らないの
は化学吸着の特徴である。The amount of trapped NOx is substantially constant regardless of the NOx concentration. The fact that the amount of adsorption does not depend on the concentration (pressure) of the adsorbate is a characteristic of chemisorption.

【００５７】供試吸着触媒中でＮＯｘ吸着楳としてとし
て先ず考えられるのはＰｔ粒子である。露出Ｐｔ量を評
価する手段として多用されるＣＯ吸着量評価を行ったと
ころＣＯ吸着量（at １００℃）は４.５×１０-4molで
あった。この値は上記ＮＯｘ吸着量の約１／１００であ
りＰｔがＮＯｘ吸着楳の主役でないことは明らかであ
る。Pt particles are firstly considered as NOx adsorbents in the test adsorption catalyst. When the amount of CO adsorbed, which is frequently used as a means for evaluating the amount of exposed Pt, was evaluated, the amount of adsorbed CO (at 100 ° C.) was 4.5 × 10 −4 mol. This value is about 1/100 of the NOx adsorption amount, and it is clear that Pt is not the main player of NOx adsorption.

【００５８】一方、本吸着触媒のコーディェライトごと
測定したＢＥＴ比表面積（窒素吸着で測定）は約２５ｍ
2／ｇでハニカム１.７Ｌ当たり２８,０５０ｍ2であっ
た。また、本発明の吸着触媒のＮａの化学構造について
検討したところ、鉱酸にＣＯ2ガスを発生して溶解する
こと及び鉱酸による中和滴定曲線における変曲点の値か
ら判断して主にＮａ2ＣＯ3として存在すると判断でき
た。仮に全ての表面がＮａ2ＣＯ3で占められているとす
ると表面には０.２７５molのＮａ2ＣＯ3が露出している
ことになる（Ｎａ2ＣＯ3の比重が２.５３３ｇ／ｍｌで
あることから Ｎａ2ＣＯ3１分子の体積が求まる（Ｎａ
2ＣＯ3を立方体と仮定してその１面の面積を求めこれを
表面Ｎａ2ＣＯ3の占有面積とした）。前出の反応式に従
えば０.２７５molのＮａ2ＣＯ3は０.５５molのＮＯ2 を
吸着する能力がある。しかし、実際に本発明の吸着触媒
が除去したＮＯｘ量はその１／１０以下の０.０４molの
オーダーである。この相違はＢＥＴ法が物理表面積を評
価するものでＡｌ2Ｏ3等のＮａ2ＣＯ3以外の表面積も評
価していることによる。以上の評価は、吸着ＮＯｘ量は
Ｎａ2ＣＯ3バルクのＮＯｘ捕捉能よりはるかに少なく、
少なくともＮＯｘがＮａ2ＣＯ3表面か表面近傍の限られ
た領域で捕捉されていることを示している。On the other hand, the BET specific surface area (measured by nitrogen adsorption) of the present adsorption catalyst measured for each cordierite is about 25 m
It was 28,050 m 2 per 1.7 L of honeycomb at 2 / g. Further, when the chemical structure of Na of the adsorption catalyst of the present invention was examined, it was mainly determined from the fact that CO 2 gas was generated and dissolved in the mineral acid and the value of the inflection point in the neutralization titration curve with the mineral acid was used. It was determined that it was present as Na 2 CO 3 . Assuming that the entire surface is occupied by Na 2 CO 3 , 0.275 mol of Na 2 CO 3 is exposed on the surface (the specific gravity of Na 2 CO 3 is 2.533 g / ml). From this, the volume of one molecule of Na 2 CO 3 is determined (Na
Assuming that 2 CO 3 is a cube, the area of one surface was determined and this was defined as the area occupied by the surface Na 2 CO 3 ). According to the above reaction formula, 0.275 mol of Na 2 CO 3 is capable of adsorbing 0.55 mol of NO 2 . However, the amount of NOx actually removed by the adsorption catalyst of the present invention is on the order of 0.04 mol, which is 1/10 or less. This difference is due to the fact that the BET method evaluates the physical surface area and also evaluates the surface area other than Na 2 CO 3 such as Al 2 O 3 . The above evaluation shows that the amount of adsorbed NOx is much smaller than the NOx trapping ability of Na 2 CO 3 bulk,
This indicates that at least NOx is trapped in the Na 2 CO 3 surface or a limited area near the surface.

【００５９】図４は、リーン運転からストイキ運転に切
替えた直後のＮＯｘ浄化率を示す。本吸着触媒では、ス
トイキ運転への切替え直後から９０％以上のＮＯｘ浄化
率が得られることが分かる。FIG. 4 shows the NOx purification rate immediately after switching from the lean operation to the stoichiometric operation. It can be seen that with the present adsorption catalyst, a NOx purification rate of 90% or more can be obtained immediately after switching to the stoichiometric operation.

【００６０】図５，図６に、リーンからストイキあるい
はリッチへの切替え前後におけるＮＯｘ浄化特性を示し
た。図５は吸着触媒Ｎ−Ｎ９の入口と出口のＮＯｘ濃度
を示したもので、図（ａ）はＡ／Ｆ＝２２のリーンから
Ａ／Ｆ＝１４.２ のリッチへ空燃比を切替えた場合であ
る。リッチ切替え直後の再生の開始時点においてはＡ／
Ｆ＝１４.２ の排ガスＮＯｘ濃度が高いためリッチ運転
の入口ＮＯｘ濃度が大きく増加し、これに伴い過渡的に
出口ＮＯｘ濃度は増加するが、常時出口NOx濃度は入口
ＮＯｘ濃度を大きく下回る。再生は速やかに進み短時間
で出口ＮＯｘ濃度は０近傍に到達する。図(ｂ）はＡ／
Ｆ＝２２のリーンからＡ／Ｆ＝１４.２のリッチへ空燃
比を切替えた場合であるが、図（ａ）と同様に、常時出
口ＮＯｘ濃度は入口ＮＯｘ濃度を大きく下回り、且つ、
より短時間で出口ＮＯｘ濃度は０近傍に到達する。FIGS. 5 and 6 show NOx purification characteristics before and after switching from lean to stoichiometric or rich. FIG. 5 shows the NOx concentration at the inlet and outlet of the adsorption catalyst N-N9. FIG. 5A shows the case where the air-fuel ratio is switched from lean at A / F = 22 to rich at A / F = 14.2. It is. At the start of playback immediately after rich switching, A /
Since the exhaust gas NOx concentration at F = 14.2 is high, the inlet NOx concentration in the rich operation greatly increases, and the outlet NOx concentration transiently increases with this. However, the outlet NOx concentration is always significantly lower than the inlet NOx concentration. The regeneration proceeds promptly, and the outlet NOx concentration reaches near zero in a short time. Figure (b) shows A /
This is a case where the air-fuel ratio is switched from lean at F = 22 to rich at A / F = 14.2, but the outlet NOx concentration is always much lower than the inlet NOx concentration, as in FIG.
The outlet NOx concentration reaches near zero in a shorter time.

【００６１】以上から明らかであるが、再生条件として
のＡ／Ｆ値は再生に要する時間に影響する。再生に適し
たＡ／Ｆ値，時間、さらには還元剤量は、吸着触媒の組
成，形状，温度，ＳＶ値，還元剤の種類，排気流路の形
状や長さの影響を受ける。従って、再生条件はこれらを
考慮して総合的に決められるものである。As is clear from the above, the A / F value as a reproduction condition affects the time required for reproduction. The A / F value, time, and amount of reducing agent suitable for regeneration are affected by the composition, shape, temperature, SV value, type of reducing agent, and shape and length of the exhaust passage of the adsorption catalyst. Therefore, reproduction conditions are comprehensively determined in consideration of these.

【００６２】図６は吸着触媒Ｎ−Ｋ９の入口と出口のＮ
Ｏｘ濃度を示したもので、図（ａ）はＡ／Ｆ＝２２のリ
ーンからＡ／Ｆ＝１４.２ のリッチへ空燃比を切替えた
場合、図（ｂ）はＡ／Ｆ＝２２のリーンからＡ／Ｆ＝１
４.２ のリッチへ空燃比を切替えた場合であるが、上述
の吸着触媒Ｎ−Ｎ９の場合と同様に常時出口ＮＯｘ濃度
は入口ＮＯｘ濃度を大きく下回り、且つ、短時間で吸着
触媒の再生が進んでいる。FIG. 6 shows N and N at the inlet and outlet of the adsorption catalyst NK9.
FIG. 4A shows the Ox concentration. FIG. 4A shows the case where the air-fuel ratio is switched from A / F = 22 lean to A / F = 14.2 rich, and FIG. 4B shows A / F = 22 lean. A / F = 1
In the case where the air-fuel ratio is switched to 4.2 rich, the NOx concentration at the outlet is always much lower than the NOx concentration at the inlet and the regeneration of the adsorbent catalyst is performed in a short time as in the case of the adsorption catalyst N-N9. I'm advancing.

【００６３】［排気浄化制御装置］図１は本発明のＮＯ
ｘ吸着触媒の理論空燃比モード運転時の空燃比制御機能
を有する排気浄化装置の一例である。排気温度，該吸着
触媒の温度，車速，内燃機関の回転数、該機関の負荷，
吸入空気量のいずれかひとつ以上の状態量が理論空燃比
／リーンモード判定手段に入力される。理論空燃比モー
ド運転時の場合はＮＯｘ吸着触媒の上流か下流に設けら
れた酸素センサまたは空燃比センサ信号による目標空気
過剰率λ＝０.９８ になるようなフィードバック制御が
行われる。理論空燃比より若干濃い値(空気過剰率λ０.
９７から１の範囲）に制御することにより、過渡運転時
のスパイク状に発生したＮＯｘがＮＯｘ触媒により効率
よく吸着，還元されるため、ＮＯｘ排出量が著しく低減
される。このフィードバック制御に関して以下の制御技
術を採用することにより、さらにＮＯｘ浄化率を高める
ことができる。[Exhaust gas purification control device] FIG.
1 is an example of an exhaust gas purification device having an air-fuel ratio control function when a x-adsorption catalyst is operated in a stoichiometric air-fuel ratio mode. Exhaust temperature, temperature of the adsorption catalyst, vehicle speed, rotation speed of the internal combustion engine, load of the engine,
One or more state quantities of the intake air amount are input to the stoichiometric air-fuel ratio / lean mode determination means. In the case of the stoichiometric air-fuel ratio mode operation, feedback control is performed so that the target excess air ratio λ = 0.98 based on an oxygen sensor or an air-fuel ratio sensor signal provided upstream or downstream of the NOx adsorption catalyst. A value slightly higher than the stoichiometric air-fuel ratio (excess air ratio λ0.
By controlling the NOx in the range of 97 to 1), NOx generated in a spike during transient operation is efficiently adsorbed and reduced by the NOx catalyst, so that the NOx emission is significantly reduced. By employing the following control technique for this feedback control, the NOx purification rate can be further increased.

【００６４】（ａ）フィードバックの空燃比目標値を所
定の変動幅，所定の周波数でλ＝０．９８を中心にして
故意に変動させる。(A) The air-fuel ratio target value of the feedback is intentionally fluctuated around λ = 0.98 with a predetermined fluctuation width and a predetermined frequency.

【００６５】（ｂ）ＮＯｘ吸着触媒の上流と下流の両方
に空燃比を検出する排気センサを設置し、下流の排気セ
ンサ信号に応じて平均空燃比が目標空燃比（空気過剰率
λ＝０．９８)になるように上流の排気センサによるフ
ィードバック制御の目標値を変化させる。(B) An exhaust sensor for detecting the air-fuel ratio is installed both upstream and downstream of the NOx adsorption catalyst, and the average air-fuel ratio is adjusted to the target air-fuel ratio (excess air ratio λ = 0. 98), the target value of the feedback control by the upstream exhaust sensor is changed.

【００６６】リーンモード運転時はＮＯｘ吸着触媒の上
流か下流に設けられた酸素センサまたは空燃比センサ信
号による目標空気過剰率λ＝２.７ になるようなフィー
ドバック制御が行われる。しかし、ＮＯｘ吸着量が所定
値以上になったらＮＯｘの還元処理を実施する。ＮＯｘ
吸着触媒に吸着されたＮＯｘの還元処理は該触媒に流入
する排ガス中の未燃炭化水素濃度を増加させることで行
い、具体的には空燃比を理論空燃比より濃くしたり（燃
料噴射量を増加する）、筒内噴射の場合は機関の膨張行
程や排気行程中に追加噴射することにより、未燃炭化水
素濃度を増加させる。この増加により、ＮＯｘ吸着触媒
に吸着されたＮＯｘは未燃炭化水素で還元され、無害化
される。未燃炭化水素濃度を増加させた時にエンジンの
出力トルクまた車の駆動輪の最終駆動トルクに変動が生
じないように点火時期，吸入空気量，排ガスの一部を内
燃機関の吸気に混ぜる量（ＥＧＲ率），燃料噴射量，燃
料噴射タイミング，内燃機関の出力をアシストする電動
モータ、該機関に設けられた発電機の負荷、該機関出力
側のブレーキングのいずれか１つ以上の手段で調整す
る。During the lean mode operation, feedback control is performed so that the target excess air ratio λ = 2.7 based on the signal of the oxygen sensor or the air-fuel ratio sensor provided upstream or downstream of the NOx adsorption catalyst. However, when the NOx adsorption amount becomes equal to or more than the predetermined value, the NOx reduction process is performed. NOx
The reduction treatment of the NOx adsorbed on the adsorption catalyst is performed by increasing the concentration of unburned hydrocarbons in the exhaust gas flowing into the catalyst. Specifically, the air-fuel ratio is made higher than the stoichiometric air-fuel ratio or the fuel injection amount is reduced. In the case of in-cylinder injection, the unburned hydrocarbon concentration is increased by performing additional injection during the expansion stroke and the exhaust stroke of the engine. Due to this increase, the NOx adsorbed on the NOx adsorption catalyst is reduced by the unburned hydrocarbons and is rendered harmless. The ignition timing, the amount of intake air, and the amount of part of exhaust gas mixed with the intake air of the internal combustion engine so that the output torque of the engine and the final drive torque of the drive wheels of the vehicle do not change when the concentration of unburned hydrocarbons is increased ( EGR rate), fuel injection amount, fuel injection timing, electric motor for assisting the output of the internal combustion engine, load of the generator provided in the engine, braking by any one or more of the means on the engine output side I do.

【００６７】図７はこれを実現するための内燃機関のエ
ンジン制御システム図である。FIG. 7 is an engine control system diagram of an internal combustion engine for realizing this.

【００６８】本発明の装置は、リーンバーン可能なエン
ジン９９，エアフローセンサー２，電子制御スロットル
バルブ３等を擁する吸気系，酸素濃度センサー(or Ａ／
Ｆセンサー）１９，排気温度センサー１７，ＮＯｘ吸着
触媒１８等を擁する排気系及び制御ユニット（ＥＣＵ）
等から構成される。ＥＣＵは入出力インターフェイスと
してのＩ／Ｏ ＬＳＩ，演算処理装置ＭＰＵ，多数の制
御プログラムを記憶させた記憶装置ＲＡＭおよびＲＯ
Ｍ，タイマーカウンター等より構成される。このＥＣＵ
には本発明である以下の処理をする制御プログラムが格
納されており、各種のセンサー信号に基づいて、理論空
燃比／リーンモード運転判定部，理論空燃比フィードバ
ック制御部，リーン空燃比フィードバック制御部，ＮＯ
ｘ還元処理を実施する。ＮＯｘ吸着触媒の温度，車の走
行距離，空燃比，ストイキ（理論空燃比）またはリッチ
運転からリーン運転に変化した時からのリーン運転経過
時間，内燃機関の回転数、該機関の負荷，吸入空気量の
いずれかひとつ以上の状態量が理論空燃比／リーンモー
ド運転判定部に入力される。この判定結果に応じて理論
空燃比／リーンモードの空燃比フィードバック制御を排
気センサ１９に基づいて行う。ＮＯｘ吸着触媒に吸着さ
れたＮＯｘの還元処理は該触媒に流入する排ガス中の未
燃炭化水素濃度を増加させることで行い、具体的には空
燃比を理論空燃比より濃くしたり（燃料噴射量を増加す
る）、筒内噴射の場合は機関の膨張行程や排気行程中に
追加噴射することにより、未燃炭化水素濃度を増加させ
る。この増加により、ＮＯｘ吸着触媒に吸着されたＮＯ
ｘは未燃炭化水素で還元され、無害化される。未燃炭化
水素濃度を増加させた時にエンジンの出力トルクまた車
の駆動輪の最終駆動トルクに変動が生じないように点火
時期，吸入空気量，排ガスの一部を内燃機関の吸気に混
ぜる量（ＥＧＲ率，ＥＧＲバルブ３１），燃料噴射量イ
ンジェクター５），燃料噴射タイミング，内燃機関の出
力をアシストする電動モータ、該機関に設けられた発電
機の負荷、該機関出力側のブレーキングのいずれか１つ
以上の手段で調整する。The apparatus of the present invention comprises an intake system having an engine 99 capable of lean burn, an air flow sensor 2, an electronically controlled throttle valve 3, etc., an oxygen concentration sensor (or A /
F sensor) 19, exhaust temperature sensor 17, exhaust system and control unit (ECU) having NOx adsorption catalyst 18, etc.
And so on. The ECU includes an I / O LSI as an input / output interface, an arithmetic processing unit MPU, a storage device RAM storing a large number of control programs, and an RO.
M, a timer counter and the like. This ECU
Stores a control program for performing the following processing according to the present invention, based on various sensor signals, based on a stoichiometric air / fuel ratio / lean mode operation determination unit, a stoichiometric air / fuel ratio feedback control unit, and a lean air / fuel ratio feedback control unit. , NO
Perform x reduction processing. NOx adsorption catalyst temperature, vehicle travel distance, air-fuel ratio, stoichiometric (stoichiometric air-fuel ratio) or lean operation elapsed time from the time of change from rich operation to lean operation, internal combustion engine speed, load of the engine, intake air Any one or more of the quantities is input to the stoichiometric air-fuel ratio / lean mode operation determination unit. The air-fuel ratio feedback control in the stoichiometric air-fuel ratio / lean mode is performed based on the exhaust sensor 19 according to the determination result. The reduction treatment of the NOx adsorbed on the NOx adsorption catalyst is performed by increasing the concentration of unburned hydrocarbons in the exhaust gas flowing into the catalyst. Specifically, the air-fuel ratio is made higher than the stoichiometric air-fuel ratio (fuel injection amount). In the case of in-cylinder injection, the unburned hydrocarbon concentration is increased by performing additional injection during the expansion stroke and the exhaust stroke of the engine. Due to this increase, the NO adsorbed by the NOx adsorption catalyst
x is reduced with unburned hydrocarbons and rendered harmless. The ignition timing, the amount of intake air, and the amount of part of exhaust gas mixed with the intake air of the internal combustion engine so that the output torque of the engine and the final drive torque of the drive wheels of the vehicle do not change when the concentration of unburned hydrocarbons is increased ( EGR rate, EGR valve 31), fuel injection amount injector 5), fuel injection timing, electric motor for assisting output of internal combustion engine, load of generator provided in the engine, braking on engine output side Adjust by one or more means.

【００６９】以上の排気浄化制御装置は、以下のように
機能する。エンジンへの吸入空気はエアクリーナー１に
より濾過された後エアフローセンサー２により計量さ
れ、電子制御スロットルバルブ３を経て、さらにインジ
ェクター５から燃料噴射を受け、混合気としてエンジン
９９に供給される。エアフローセンサー信号その他のセ
ンサー信号はＥＣＵ(Engine Control Unit）へ入力され
る。The above exhaust gas purification control device functions as follows. The intake air to the engine is filtered by an air cleaner 1 and then measured by an air flow sensor 2, passes through an electronic control throttle valve 3, receives a fuel injection from an injector 5, and is supplied to the engine 99 as an air-fuel mixture. The airflow sensor signal and other sensor signals are input to an ECU (Engine Control Unit).

【００７０】ＥＣＵでは後述の方法によって内燃機関の
運転状態及びＮＯｘ吸着触媒の状態を評価して運転空燃
比を決定し、インジェクター５の噴射時間等を制御して
混合気の燃料濃度を所定値に設定する。インジェクター
５は図７のエンジンの吸気ポート位置の代わりにディー
ゼルのようにシリンダ内噴射ができるように取付けても
よい。また、噴射燃料一定で電子制御スロットルバルブ
３の開度調整（スロットルアクチュエータ３１）で吸入
空気量を減らして混合気の燃料濃度を所定値に設定して
もよい。シリンダーに吸入された混合気はＥＣＵ２５か
らの信号で制御される点火プラグ６により着火され燃焼
する。燃焼排ガスは排気浄化系に導かれる。排気浄化系
にはＮＯｘ吸着触媒が設けられ、ストイキ運転時にはそ
の三元触媒機能により排ガス中のＮＯｘ，ＨＣ，ＣＯを
浄化し、また、リーン運転時にはＮＯｘ吸着能によりＮ
Ｏｘを浄化すると同時に併せ持つ燃焼機能により、Ｈ
Ｃ，ＣＯを浄化する。さらに、ＥＣＵの判定及び制御信
号により、リーン運転時にはＮＯｘ吸着触媒のＮＯｘ吸
着量により、空燃比をリッチ側にシフトしたり、膨張行
程や排気行程にシリンダ内噴射して、吸着触媒のＮＯｘ
吸着能を回復させる。以上の操作により、本装置では、
リーン運転，ストイキ（含むリッチ）運転の全てのエン
ジン燃焼条件下における排ガスを効果的に浄化する。The ECU evaluates the operating state of the internal combustion engine and the state of the NOx adsorbing catalyst to determine the operating air-fuel ratio by the method described later, and controls the injection time of the injector 5 to adjust the fuel concentration of the air-fuel mixture to a predetermined value. Set. The injector 5 may be mounted so as to be able to perform in-cylinder injection like diesel instead of the intake port position of the engine in FIG. Alternatively, the fuel concentration of the air-fuel mixture may be set to a predetermined value by reducing the intake air amount by adjusting the opening degree of the electronic control throttle valve 3 (throttle actuator 31) while the injected fuel is constant. The air-fuel mixture sucked into the cylinder is ignited by the ignition plug 6 controlled by a signal from the ECU 25 and burns. The combustion exhaust gas is led to an exhaust purification system. The exhaust gas purification system is provided with a NOx adsorption catalyst, which purifies NOx, HC, and CO in exhaust gas by a three-way catalytic function during stoichiometric operation, and a NOx adsorbent by lean NOx adsorption capability during lean operation.
The combustion function that purifies Ox and combines it with H
Purifies C and CO. Further, according to the determination and control signal of the ECU, during lean operation, the air-fuel ratio is shifted to the rich side or injected into the cylinder during the expansion stroke or the exhaust stroke depending on the amount of NOx adsorbed by the NOx adsorbing catalyst.
Restore adsorption capacity. With the above operation, this device
Effectively purifies exhaust gas under all engine combustion conditions of lean operation and stoichiometric (including rich) operation.

【００７１】[0071]

【発明の効果】本発明によれば、理論空燃比モード運転
時、理論空燃比より若干濃い値（空気過剰率λ０.９７
から１の範囲）に制御することにより、過渡運転時のス
パイク状に発生したＮＯｘがＮＯｘ触媒により効率よく
吸着，還元されるため、ＮＯｘ排出量が著しく低減され
る。According to the present invention, during operation in the stoichiometric air-fuel ratio mode, a value slightly higher than the stoichiometric air-fuel ratio (excess air ratio λ 0.97)
(In the range from 1 to 1), NOx generated in a spike during transient operation is efficiently adsorbed and reduced by the NOx catalyst, so that the NOx emission amount is significantly reduced.

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

【図１】本発明の代表的な実施態様を示す本発明の方法
による排ガス浄化装置の構成図。FIG. 1 is a configuration diagram of an exhaust gas purifying apparatus according to a method of the present invention, showing a typical embodiment of the present invention.

【図２】本発明の方法によりリッチ運転とリーン運転を
交互に繰り返したときのＮＯｘ浄化率の経時特性を示す
図。FIG. 2 is a graph showing a time characteristic of a NOx purification rate when a rich operation and a lean operation are alternately repeated by the method of the present invention.

【図３】排気中のＮＯｘ濃度とＮＯｘ浄化率の関係を示
す図。FIG. 3 is a diagram showing a relationship between NOx concentration in exhaust gas and NOx purification rate.

【図４】ストイキ排ガス中のＮＯｘ浄化率を示す図。FIG. 4 is a view showing a NOx purification rate in stoichiometric exhaust gas.

【図５】リッチ（ストイキ）運転からリーン運転に切替
えたときの吸着触媒入口ＮＯｘ濃度と出口ＮＯｘ濃度の
関係を示す図。FIG. 5 is a diagram showing the relationship between the NOx concentration at the inlet of the adsorption catalyst and the NOx concentration at the outlet when switching from rich (stoichiometric) operation to lean operation.

【図６】リッチ（ストイキ）運転からリーン運転に切替
えたときの吸着触媒入口ＮＯｘ濃度と出口ＮＯｘ濃度の
関係を示す図。FIG. 6 is a diagram showing the relationship between the NOx concentration at the inlet and the NOx concentration at the outlet when switching from rich (stoichiometric) operation to lean operation.

【図７】エンジン制御システムを示す図。FIG. 7 is a diagram showing an engine control system.

【符号の説明】[Explanation of symbols]

１…エアクリーナ、２…エアフローセンサー、３…スロ
ットルバルブ、５…インジェクタ、６…点火プラグ、７
…アクセルペダル、８…負荷センサー、９…吸気温度セ
ンサー、１２…燃料ポンプ、１３…燃料タンク、１７…
マニホールド触媒、１８…吸着触媒、１９…排気センサ
ー、２０…吸着触媒温度センサー、２５…ＥＣＵ、２７
…ＥＧＲバルブ、２８…水温センサー、２９…クランク
角センサー、３１…スロットルアクチュエーター、９９
…エンジン。DESCRIPTION OF SYMBOLS 1 ... Air cleaner, 2 ... Air flow sensor, 3 ... Throttle valve, 5 ... Injector, 6 ... Spark plug, 7
... Accelerator pedal, 8 ... Load sensor, 9 ... Intake air temperature sensor, 12 ... Fuel pump, 13 ... Fuel tank, 17 ...
Manifold catalyst, 18: Adsorption catalyst, 19: Exhaust sensor, 20: Adsorption catalyst temperature sensor, 25: ECU, 27
... EGR valve, 28 ... Water temperature sensor, 29 ... Crank angle sensor, 31 ... Throttle actuator, 99
…engine.

フロントページの続き Ｆターム(参考） 3G091 AA02 AA11 AA12 AA13 AA14 AA17 AA18 AA23 AA24 AB06 AB09 BA01 BA11 BA14 BA15 BA19 BA33 BA39 CA13 CA17 CA18 CA19 CB02 CB03 CB05 CB06 CB07 CB08 DA01 DA02 DA03 DA05 DB06 DB10 DB13 DC01 EA01 EA03 EA04 EA05 EA06 EA07 EA16 EA17 EA18 EA30 EA31 EA33 EA34 EA39 FA17 FA18 FA19 FB10 FB11 FB12 FC02 FC04 GA01 GA03 GA06 GB01W GB01X GB02W GB03W GB04W GB05W GB06W GB07W GB10W GB10X GB16X GB17X HA08 HA18 HA36 HA37 HA39 HB03 HB05 HB08 HB09 3G301 HA01 HA02 HA04 HA06 HA07 HA13 HA14 HA15 HA18 JA15 JA25 JA26 JA33 JB09 KA11 KA12 KA16 LA03 LB02 LB04 MA01 MA11 MA18 MA26 NA06 NA07 NA08 NA09 ND01 NE01 NE06 NE11 NE12 NE13 NE14 NE15 PA01A PA01B PA07A PA07B PD02A PD02B PD11A PD11B PD12A PD12B PE01A PE01B PE03A PE03B PE08A PE08B PF01A PF01B PF03A PF03B PF12A PF12B Continued on the front page F term (reference) 3G091 AA02 AA11 AA12 AA13 AA14 AA17 AA18 AA23 AA24 AB06 AB09 BA01 BA11 BA14 BA15 BA19 BA33 BA39 CA13 CA17 CA18 CA19 CB02 CB03 CB05 CB06 CB07 CB08 DA01 DA02 DA03 DB05 DB06 EA EA06 EA07 EA16 EA17 EA18 EA30 EA31 EA33 EA34 EA39 FA17 FA18 FA19 FB10 FB11 FB12 FC02 FC04 GA01 GA03 GA06 GB01W GB01X GB02W GB03W GB04W GB05W GB06W GB07W GB10W GB10X GB16X GB17H03 HA03 HA08 HA03 HA08 HA03 HA08 HA03 HA08 HA03 HA08 HA03 HA08 HA03 HA08 HA03 HA08 HA03 HA15 HA18 JA15 JA25 JA26 JA33 JB09 KA11 KA12 KA16 LA03 LB02 LB04 MA01 MA11 MA18 MA26 NA06 NA07 NA08 NA09 ND01 NE01 NE06 NE11 NE12 NE13 NE14 NE15 PA01A PA01B PA07A PA07B PD02A PD02B PD11A PD11B0312 PDA PE01B03A01 PF12B

Claims (8)

【特許請求の範囲】[Claims] 【請求項１】排ガス中の各成分間の酸化還元化学量論関
係において還元剤に対して酸化剤が多い状態でＮＯｘを
化学吸着し、酸化剤に対し還元剤が同量以上の状態で吸
着したＮＯｘを接触還元するＮＯｘ吸着触媒を排ガス流
路に配置し、排ガス中の各成分間の酸化還元化学量論関
係において還元剤に対して酸化剤が多い状態をつくって
吸着触媒上にＮＯｘを化学吸着させ、次に酸化剤に対し
還元剤が同量以上の状態をつくり、吸着触媒上に吸着し
たＮＯｘを還元剤と接触反応させてＮ2 に還元して無害
化する内燃機関の排ガス浄化装置において、 理論空燃比運転モード時は内燃機関から排出される排ガ
スの空気過剰率λが１以下（理論空燃比を含む濃い混合
気）になるように機関の燃料供給量と空気供給量を制御
することを特徴とする排気浄化制御装置。1. In the oxidation-reduction stoichiometry relationship between components in exhaust gas, NOx is chemisorbed in a state where the oxidizing agent is large relative to the reducing agent, and is adsorbed in a state where the reducing agent is equal to or more than the oxidizing agent A NOx adsorption catalyst for catalytically reducing NOx is placed in the exhaust gas flow path, and in a redox stoichiometric relationship between the components in the exhaust gas, a state in which the amount of the oxidant is large relative to the reducing agent is formed, and NOx is reduced on the adsorption catalyst. is chemically adsorbed, then the reducing agent to the oxidizing agent is made the same amount or more conditions, the exhaust gas purification of an internal combustion engine to harmless by reduction by catalytic reaction with a reducing agent to N 2 adsorbed NOx on adsorption catalyst In the device, in the stoichiometric air-fuel ratio operation mode, the fuel supply amount and the air supply amount of the engine are controlled such that the excess air ratio λ of the exhaust gas discharged from the internal combustion engine becomes 1 or less (a rich mixture including the stoichiometric air-fuel ratio). Exhaust gas purification characterized by The control device. 【請求項２】少なくともカリウム（Ｋ），ナトリウム
（Ｎａ），マグネシウム（Ｍｇ），ストロンチウム（Ｓ
ｒ）及びカルシウム（Ｃａ）から選ばれる一種以上の元
素を成分の一部として含むＮＯｘ吸着触媒を排ガス流路
に配置し、排ガス中の各成分間の酸化還元化学量論関係
において還元剤に対して酸化剤が多い状態をつくって吸
着触媒上にＮＯｘを化学吸着させ、次に酸化剤に対し還
元剤が同量以上の状態をつくり、吸着触媒上に吸着した
ＮＯｘを還元剤と接触反応させてＮ2 に還元して無害化
する内燃機関の排ガス浄化装置において、 理論空燃比運転モード時は内燃機関から排出される排ガ
スの空気過剰率λが１以下（理論空燃比を含む濃い混合
気）になるように機関の燃料供給量と空気供給量を制御
することを特徴とする排気浄化制御装置。2. At least potassium (K), sodium (Na), magnesium (Mg), strontium (S)
r) and a NOx adsorption catalyst containing at least one element selected from the group consisting of calcium (Ca) as a part of the components is disposed in the exhaust gas flow path. To create a state with a large amount of oxidant to chemically adsorb NOx on the adsorption catalyst, and then create a state in which the amount of the reducing agent is equal to or more than that of the oxidizing agent, and contact the NOx adsorbed on the adsorption catalyst with the reducing agent to react. Exhaust gas purifying apparatus for an internal combustion engine, which reduces the amount of exhaust gas to N 2 and renders it harmless, the excess air ratio λ of exhaust gas discharged from the internal combustion engine is 1 or less (a rich air-fuel mixture including the stoichiometric air-fuel ratio) in the stoichiometric air-fuel ratio operation mode An exhaust gas purification control device characterized by controlling a fuel supply amount and an air supply amount of an engine such that 【請求項３】少なくともカリウム（Ｋ），ナトリウム
（Ｎａ），マグネシウム（Ｍｇ），ストロンチウム（Ｓ
ｒ）及びカルシウム（Ｃａ）から選ばれる一種以上の元
素を成分の一部として含むＮＯｘ吸着触媒を排ガス流路
に配置し、酸化還元化学量論関係においてＨＣ等の還元
剤に対してＯ2 等の酸化剤が多い状態をつくって吸着触
媒表面及び表面近傍にＮＯｘを化学結合により捕捉し、
次に酸化剤に対し還元剤が同量かもしくは多い状態をつ
くり、吸着触媒に捕捉されたＮＯｘを還元剤と接触反応
させてＮ2 に還元して無害化する内燃機関の排ガス浄化
装置において、 理論空燃比運転モード時は内燃機関から排出される排ガ
スの空気過剰率λが１以下（理論空燃比を含む濃い混合
気）になるように機関の燃料供給量と空気供給量を制御
することを特徴とする排気浄化制御装置。3. At least potassium (K), sodium (Na), magnesium (Mg), strontium (S
The NOx adsorbing catalyst disposed in the exhaust gas line comprising one or more elements selected from r) and calcium (Ca) as part of component, O 2 or the like to a reducing agent such as HC in a redox stoichiometry NOx is trapped on the surface of the adsorption catalyst and near the surface by chemical bonding,
Then create a state reducing agent is the same amount whether or greater relative to the oxidant, the exhaust gas purifying apparatus of an internal combustion engine to harmless by reducing NOx trapped in the adsorbent catalyst by catalytic reaction with a reducing agent to N 2, In the stoichiometric air-fuel ratio operation mode, the fuel supply amount and the air supply amount of the engine are controlled so that the excess air ratio λ of the exhaust gas discharged from the internal combustion engine becomes 1 or less (a rich mixture including the stoichiometric air-fuel ratio). Exhaust gas purification control device. 【請求項４】請求項１又は２において、カリウム
（Ｋ），ナトリウム（Ｎａ），マグネシウム（Ｍｇ），
ストロンチウム（Ｓｒ）及びカルシウム（Ｃａ）から選
ばれる少なくとも一種とセリウム等からなる希土類から
選ばれる少なくとも一種と、白金，ロジウム，パラジウ
ム等からなる貴金属から選ばれる少なくとも一種の元素
を含む、金属および金属酸化物（もしくは複合酸化物）
からなる組成物もしくは該組成物を多孔質耐熱性金属酸
化物に担持してなる組成物を吸着触媒として用いた排気
浄化制御装置。4. The method according to claim 1, wherein potassium (K), sodium (Na), magnesium (Mg),
Metals and metal oxides containing at least one element selected from strontium (Sr) and calcium (Ca) and at least one element selected from rare earths such as cerium and at least one element selected from noble metals such as platinum, rhodium and palladium Object (or composite oxide)
An exhaust gas purification control device using, as an adsorption catalyst, a composition comprising: or a composition obtained by supporting the composition on a porous heat-resistant metal oxide. 【請求項５】請求項１又は２において、カリウム
（Ｋ），ナトリウム（Ｎａ），マグネシウム（Ｍｇ），
ストロンチウム（Ｓｒ）及びカルシウム（Ｃａ）から選
ばれる少なくとも一種と、セリウム等からなる希土類か
ら選ばれる少なくとも一種と、白金，ロジウム，パラジ
ウム等からなる貴金属から選ばれる少なくとも一種と、
チタン及びシリコンから選ばれる少なくとも一種の元素
を含む、金属および金属酸化物（もしくは複合酸化物）
からなる組成物、該組成物を多孔質耐熱性金属酸化物に
担持してなる組成物を吸着触媒として用いた排気浄化制
御装置。5. The method according to claim 1, wherein potassium (K), sodium (Na), magnesium (Mg),
At least one selected from strontium (Sr) and calcium (Ca), at least one selected from rare earths such as cerium, and at least one selected from precious metals such as platinum, rhodium, and palladium;
Metals and metal oxides (or composite oxides) containing at least one element selected from titanium and silicon
An exhaust gas purification control device comprising, as an adsorption catalyst, a composition comprising: and a composition comprising the composition supported on a porous heat-resistant metal oxide. 【請求項６】請求項１から５の何れかにおいて、ＮＯｘ
吸着触媒の上流または下流に設けた排気センサ信号に基
づいて、内燃機関から排出される排ガスの空気過剰率λ
が１以下（理論空燃比を含む濃い混合気）になるように
機関の燃料供給量と空気供給量を制御することを特徴と
する排気浄化制御装置。6. The method according to claim 1, wherein the NOx
An excess air ratio λ of exhaust gas discharged from the internal combustion engine based on an exhaust sensor signal provided upstream or downstream of the adsorption catalyst.
An exhaust gas purification control device for controlling the amount of fuel supplied to the engine and the amount of air supplied to the engine such that the value is 1 or less (a rich mixture including the stoichiometric air-fuel ratio). 【請求項７】請求項１から６の何れかにおいて、理論空
燃比運転モード時の内燃機関から排出される排ガスの空
気過剰率λの平均的な値が０.９７ から１の間であるこ
とを特徴とする排気浄化制御装置。7. An average value of an excess air ratio λ of exhaust gas discharged from an internal combustion engine in a stoichiometric air-fuel ratio operation mode is in a range of 0.97 to 1. An exhaust gas purification control device characterized by the above-mentioned. 【請求項８】請求項１から６の何れかにおいて、理論空
燃比運転モード時の内燃機関から排出される排ガスの空
気過剰率λが０.９７ から１の値を中心にして所定の変
動幅，所定の周波数で変動するように制御することを特
徴とする排気浄化制御装置。8. The method according to claim 1, wherein the excess air ratio λ of the exhaust gas discharged from the internal combustion engine in the stoichiometric air-fuel ratio operation mode is a predetermined fluctuation range centered on a value from 0.97 to 1. An exhaust gas purification control device, which controls to fluctuate at a predetermined frequency.
JP11224911A 1999-08-09 1999-08-09 Exhaust emission control system Pending JP2001050033A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP11224911A JP2001050033A (en) 1999-08-09 1999-08-09 Exhaust emission control system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP11224911A JP2001050033A (en) 1999-08-09 1999-08-09 Exhaust emission control system

Publications (1)

Publication Number Publication Date
JP2001050033A true JP2001050033A (en) 2001-02-23

Family

ID=16821100

Family Applications (1)

Application Number Title Priority Date Filing Date
JP11224911A Pending JP2001050033A (en) 1999-08-09 1999-08-09 Exhaust emission control system

Country Status (1)

Country Link
JP (1) JP2001050033A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004018850A1 (en) * 2002-08-26 2004-03-04 Hitachi, Ltd. Apparatus and method for clarifying exhaust gas of diesel engine

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004018850A1 (en) * 2002-08-26 2004-03-04 Hitachi, Ltd. Apparatus and method for clarifying exhaust gas of diesel engine

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