JP2001050042A - Exhaust gas emission control system - Google Patents

Exhaust gas emission control system

Info

Publication number
JP2001050042A
JP2001050042A JP11223418A JP22341899A JP2001050042A JP 2001050042 A JP2001050042 A JP 2001050042A JP 11223418 A JP11223418 A JP 11223418A JP 22341899 A JP22341899 A JP 22341899A JP 2001050042 A JP2001050042 A JP 2001050042A
Authority
JP
Japan
Prior art keywords
nox
exhaust gas
adsorption catalyst
amount
internal combustion
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
JP11223418A
Other languages
Japanese (ja)
Inventor
Toshio Manaka
敏雄 間中
Osamu Kuroda
黒田　　修
Kiyoshi Miura
清 三浦
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 JP11223418A priority Critical patent/JP2001050042A/en
Priority to DE10038227A priority patent/DE10038227A1/en
Publication of JP2001050042A publication Critical patent/JP2001050042A/en
Priority to US09/989,204 priority patent/US20020050135A1/en
Pending legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842—Nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
    • F02D41/0275—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a NOx trap or adsorbent
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/402—Multiple injections
    • F02D41/405—Multiple injections with post injections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0811—NOx storage efficiency
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Abstract

PROBLEM TO BE SOLVED: To reduce emission of hazardous exhaust gases while maintaining a NOx purification ratio in lean burn exhaust gas from an internal combustion engine constantly at or above a predetermined level. SOLUTION: Under control where a NOx adsorption catalyst is disposed in an exhaust gas passage, the NOx adsorption catalyst adsorbs NOx in an oxidization atmosphere of lean exhaust gas and regenerate the adsorption catalyst in a reduction atmosphere, an NOx purification ratio is estimated and NOx reduction process is performed according thereto. Accordingly, a NOx purification ratio can be estimated by a simple system configuration and NOx emission can be maintained constantly at a low level through reduction process based on the estimated ratio.

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
希薄空燃比（リーンバーン）で運転可能な内燃機関及び
該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 emitted from an internal combustion engine of an automobile or the like, and more particularly to an internal combustion engine operable at a lean air-fuel ratio (lean burn) and an automobile equipped with the internal combustion engine. 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
として人体に悪影響を及ぼす他、植物の生育を妨げる等
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), and the like adversely affect the human body as air pollutants and cause problems such as hindering plant growth. 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, Pt and Rh, which are three-way catalysts, are the main components of activity, and HC and CO
The mainstream is a method using a catalyst that renders harmless by simultaneously oxidizing NO and reducing NOx.

【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 extend the burn time of the lean burn method (expansion of the operating range in 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】特許番号2586739号では、内燃機関の排気
管に設置されたＮＯｘ吸収剤のＮＯxの吸収量を推定
し、その推定量があらかじめ定められた許容量を超えた
らＮＯｘ吸収剤に流入する排ガス中の酸素濃度を低下さ
せてＮＯｘ吸収剤からＮＯｘを放出させるＮＯｘ放出手
段を具備した排気浄化装置が提案されている。In Japanese Patent No. 2,867,739, the amount of NOx absorbed by a NOx absorbent installed in an exhaust pipe of an internal combustion engine is estimated, and when the estimated amount exceeds a predetermined allowable amount, exhaust gas flowing into the NOx absorbent is estimated. There has been proposed an exhaust gas purifying apparatus provided with NOx releasing means for releasing NOx from a NOx absorbent by lowering the concentration of oxygen therein.

【０００５】[0005]

【発明が解決しようとする課題】この方法ではＮＯｘ吸
収剤に吸着されたＮＯｘ吸収量に応じてＮＯｘ還元処理
（排ガス中の酸素濃度を低下させてＮＯｘ吸収剤からＮ
Ｏｘを放出させる処理）を繰り返すため、ＮＯｘ吸収剤
後のＮＯｘ排出量を排気規制値以下に維持する精度に限
度がある。In this method, the NOx reduction treatment (reducing the concentration of oxygen in the exhaust gas to reduce the NOx from the NOx absorbent in accordance with the amount of NOx absorbed by the NOx absorbent).
Since the process of releasing Ox is repeated, there is a limit to the accuracy with which the NOx emission amount after the NOx absorbent is maintained at or below the emission regulation value.

【０００６】本発明は、上記従来技術の問題点に鑑み、
ＮＯｘ吸着触媒に吸着されたＮＯｘの還元処理のタイミ
ングを精度よく実施でき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,
It is an object of the present invention to provide an exhaust gas purification control device capable of accurately executing the timing of a reduction process of NOx adsorbed on a NOx adsorption catalyst.

【０００７】[0007]

【課題を解決するための手段】上記課題は、内燃機関か
ら排出されるＮＯｘ排出量と機関の運転状態からNOx浄
化率を推定し、その推定されたＮＯｘ浄化率が所定値ま
で低下した時にＮＯｘ吸着触媒に吸着されたＮＯｘの還
元処理を行うことにより解決できる。排気を悪化させな
いタイミングでＮＯｘの還元処理を開始できるので排気
レベルも常に規制値以下に維持できる。The object of the present invention is to estimate a NOx purification rate from the amount of NOx exhausted from an internal combustion engine and the operating state of the engine. When the estimated NOx purification rate drops to a predetermined value, NOx is reduced. The problem can be solved by performing a reduction treatment of NOx adsorbed on the adsorption catalyst. Since the NOx reduction process can be started at a timing that does not deteriorate the exhaust gas, the exhaust gas level can always be maintained below the regulation value.

【０００８】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。[0008] In the NOx adsorption catalyst used in the present invention,
In the oxidation-reduction stoichiometry relationship between each component in the exhaust gas, NOx is chemisorbed in a state where the oxidizing agent is large relative to the reducing agent
NOx adsorbed with oxidizing agent in the same amount or more of reducing agent
A NOx adsorption catalyst for catalytic reduction of
In the oxidation-reduction stoichiometry relationship between each component in the exhaust gas, a state in which the oxidizing agent is large relative to the reducing agent is created, and NOx is chemisorbed on the adsorption catalyst. A state is created, and NOx adsorbed on the adsorption catalyst is brought into contact with a reducing agent to be reduced to N 2 and rendered harmless.

【０００９】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 term "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.

【００１０】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，燃焼仮定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 or the like, and is mainly oxygen. The reducing agent was H supplied to the internal combustion engine.
C, HC as derivatives thereof generated in the combustion assumption (oxygenated hydrocarbons including), CO, H 2, etc., and further, a reducing substance such as HC to be added to the exhaust gas as a reducing component described later.

【００１１】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。[0011] As described above, HC, CO, 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 .

【００１２】本発明の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（Ｈ
Ｃ，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 of the present invention, the oxidizing agent (O 2 , NOx, etc.) and the reducing agent (H
C, CO, H 2 etc.) in the oxidation-reduction system composed of the same amount or a predominant amount of the reducing agent, and the NOx adsorbed on the adsorption catalyst is contacted with the reducing agent such as HC to react with N 2 to form N 2 . To reduce.

【００１３】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
This includes providing an oxidizing function.

【００１４】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。[0014] The reduction reaction of chemisorbed NOx in the NOx adsorption catalyst of the present invention can be approximately described by the following reaction formula.

【００１５】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.

【００１６】 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.

【００１７】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.

【００１８】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。When the NOx trapping agent is a NOx absorbent, the NOx trapped in the bulk of the absorbent is also reduced, so that the calorific value increases, and the transmission to the exhaust gas is limited. Bring. This exotherm shifts the equilibrium of the absorption reaction shown below to the emission side.

【００１９】 [0019]

【００２０】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
はあまり進まないと考えられる。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と考
えられる。また、ＮＯｘ吸収量が少ない段階で還元反応
による操作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、燃費の向上効果が抑制される。Even if the concentration of the reducing agent is increased in order to reduce the released NOx quickly and reduce the NOx concentration in the exhaust gas discharged out of the apparatus, the reaction between NO 2 and HC does not proceed so much in the gas phase. it is conceivable that. Therefore, it is considered that the amount of NOx emission cannot be sufficiently reduced by increasing the amount of the reducing agent. It is also conceivable to perform an operation operation by a reduction reaction at a stage where the NOx absorption amount is small, but the regeneration frequency of the NOx absorbent increases, and the effect of improving fuel efficiency is suppressed.

【００２１】本発明の吸着触媒は、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 of the present invention traps 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.

【００２２】本発明のＮＯｘ吸着触媒は、ＮＯｘ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、本発明の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 of the present invention is characterized as a material that captures NOx on its surface by chemisorption and does not generate NOx by an exothermic reaction upon reduction of NOx. Further, the NOx adsorption catalyst of 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 generate NOx by an exothermic reaction upon reduction of NOx.

【００２３】本発明者等は、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た。The present inventors have determined that at least potassium (K), sodium (Na), magnesium (Mg),
It has been found that the above characteristics can be realized by a NOx adsorption catalyst containing at least one element selected from strontium (Sr) and calcium (Ca) as a part of components.

【００２４】本発明の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（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ＮＯｘを還元剤と
接触反応させてＮ2 に還元して無害化することを特徴と
する。The exhaust gas purifying apparatus for an internal combustion engine according to the present invention comprises at least one element selected from the group consisting of potassium (K), sodium (Na), magnesium (Mg), strontium (Sr) and calcium (Ca). The NOx adsorption catalyst, which is included as a part, is disposed in the exhaust gas flow path, and in the oxidation-reduction stoichiometric relationship between the components in the exhaust gas, a state in which the amount of the oxidizing agent is large relative to the reducing agent is formed, and the NOx adsorption catalyst is formed on the adsorption catalyst.
Was chemically adsorbed, then the reducing agent to the oxidizing agent is made the same amount or more states, and characterized in that the detoxification is reduced to N 2 by catalytic reaction with a reducing agent adsorbed NOx on adsorption catalyst I do.

【００２５】本発明の内燃機関の排ガス浄化装置は、ま
た、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ことを特徴とする。The exhaust gas purifying apparatus for an internal combustion engine according to the present invention further comprises at least potassium (K), sodium (Na),
A NOx adsorption catalyst containing at least one element selected from magnesium (Mg), strontium (Sr) and calcium (Ca) as a part of components is disposed in the exhaust gas flow path;
In the oxidation-reduction stoichiometry, a state in which the oxidizing agent such as O 2 is larger than the reducing agent such as HC is used to trap NOx by chemical bonding on the surface of the adsorption catalyst and in the vicinity of the surface. Make the same amount or more, and make NOx trapped by the adsorption catalyst react with the reducing agent to form N 2
To make it harmless.

【００２６】本発明における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 in the present invention, the following can be particularly preferably applied.

【００２７】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 and the like, 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. This composition has excellent SOx resistance in addition to excellent NOx adsorption ability.

【００２８】本発明の方法における、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 method of 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.

【００２９】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 the excess fuel (rich). Further, a reducing agent is added to the lean burn exhaust gas.

【００３０】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.

【００３１】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 air 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.

【００３２】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.

【００３３】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.

【００３４】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.

【００３５】本発明における、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。In the present invention, the adsorption catalyst can be applied in various shapes. Starting with the honeycomb shape obtained by coating the adsorption catalyst component on a honeycomb-like structure made of metal materials such as cordierite and stainless steel,
It can be applied as pellets, plates, granules, and powders.

【００３６】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、特に（４)，(５）が好ましい。In the present invention, the timing for forming a state in which the amount of the reducing agent is equal to or larger than the amount of the oxidizing agent can be determined by the following methods, and (4) and (5) are particularly preferable.

【００３７】（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) Lean operation based on an air-fuel ratio setting signal determined by an ECU (Engine Control Unit), 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. Is estimated when the integrated value exceeds a predetermined set value.

【００３８】（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.

【００３９】（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.

【００４０】（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.

【００４１】（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 Elapsed time of the lean operation from the time of the change from the rich operation to the lean operation, the number of rotations of the internal combustion engine, the load of the engine, the intake air amount, and the exhaust gas amount.
When the NOx purification rate of the Ox adsorption catalyst is estimated, and when the estimated NOx purification rate falls below a predetermined value.

【００４２】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。In the present invention, as described above, the time required to maintain the state in which the amount of the reducing agent is equal to or greater than the amount of the oxidizing agent or the amount of the reducing agent to be charged is determined in advance as described above. 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.

【００４３】[0043]

【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.

【００４４】［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.

【００４５】《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.

【００４６】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。この操作を繰返しハニカムの見掛け容積１Ｌ
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Ｍｇ
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，Ｒｈ，
Ｐｔを担持したハニカム状吸着触媒、２Ｍｇ−(０.２Ｒ
ｈ，２.７Ｐｔ)−(１８Ｎａ，４Ｔｉ，２Ｍｇ)−２７Ｃ
ｅ／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。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. This operation was repeated until the apparent volume of the honeycomb became 1 L.
Per gram of alumina was coated. 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 was impregnated, and 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, Mg nitrate
The solution was impregnated and calcined at 450 ° C. for 1 hour. Ce alumina (Al 2 O 3) by more than, Mg, Na, Ti, Rh ,
Honeycomb-shaped adsorption catalyst supporting Pt, 2Mg- (0.2R
h, 2.7Pt)-(18Na, 4Ti, 2Mg) -27C
e / 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.

【００４７】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.

【００４８】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 Na 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.

【００４９】《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 the characteristics were evaluated by the following methods.

【００５０】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.

【００５１】《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 adsorption 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 changes 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.

【００５２】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。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. The amount of NOx trapped up to the NOx purification rates of 50% and 30% is obtained from FIG.
Becomes

【００５３】[0053]

【表１】 [Table 1]

【００５４】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.

【００５５】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 first considered as NOx adsorbents in the test adsorption catalyst. When the amount of adsorbed CO, which is frequently used as a means for evaluating the amount of exposed Pt, was evaluated, the adsorbed amount of 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.

【００５６】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) measured for each cordierite of the present adsorption catalyst 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.

【００５７】図３において前記ＮＯｘ吸着能力は自動車
の走行距離の増加に伴い、低下し、ストイキ運転からリ
ーン運転に切り替えた後のＮＯｘ浄化率の減少速度が速
くなる。これは排ガス中に含まれる被毒物（ＳＯｘ等）
がＮＯｘ吸着物質と反応し、吸着能力を低下させるため
である。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。In FIG. 3, the NOx adsorbing ability decreases as the traveling distance of the vehicle increases, and the rate of decrease of the NOx purification rate after switching from the stoichiometric operation to the lean operation increases. This is a poisonous substance (SOx etc.) contained in exhaust gas.
Is to react with the NOx adsorbing substance to lower the adsorbing ability. 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.

【００５８】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.

【００５９】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.

【００６０】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.

【００６１】［排気浄化制御装置］図１は本発明のＮＯ
ｘ浄化率推定によるＮＯｘ還元処理装置の一例である。[Exhaust gas purification control device] FIG.
It is an example of a NOx reduction processing device based on x purification rate estimation.

【００６２】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がＮＯｘ吸
着触媒のＮＯｘ浄化率推定部に入力される。この推定さ
れたＮＯｘ浄化率が所定値以下になったらＮＯｘの還元
処理を実施するものである。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），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。The amount of NOx adsorbed on the NOx adsorbing catalyst, the exhaust temperature, the temperature of the adsorbing catalyst, the amount of sulfur poisoning, the traveling distance of the vehicle, the degree of catalyst deterioration, the air-fuel ratio, the concentration of unburned hydrocarbons,
NOx concentration before the catalyst, stoichiometric (stoichiometric air-fuel ratio) or one of the following: the elapsed time of the lean operation from 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 The above state quantities are input to the NOx purification rate estimating unit of the NOx adsorption catalyst. When the estimated NOx purification rate becomes equal to or less than a predetermined value, a NOx reduction process is performed. 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), 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 means of the engine output side I do.

【００６３】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.

【００６４】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、ＮＯｘ
浄化率推定，推定値の比較部，ＮＯｘ還元処理を実施す
る。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Ｎ
Ｏｘ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がＮＯｘ吸着触媒のＮ
Ｏｘ浄化率推定部に入力される。この推定されたＮＯｘ
浄化率が所定値以下になったらＮＯｘの還元処理を実施
するものである。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（ＥＧ
Ｒ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 according to 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, and performs NOx based on various sensor signals.
The purification rate estimation, the comparison part of the estimated value, and the NOx reduction processing are performed. NOx adsorption amount adsorbed on the NOx adsorption catalyst, exhaust temperature, temperature of the adsorption catalyst, sulfur poisoning amount, car traveling distance, catalyst deterioration degree, air-fuel ratio, unburned hydrocarbon concentration, N in front of the catalyst
Ox concentration, stoichiometric (stoichiometric air-fuel ratio) or elapsed time of lean operation from the time of change from rich operation to lean operation,
The state quantity of any one or more of the number of revolutions of the internal combustion engine, the load of the engine, the intake air amount, and the exhaust gas amount is determined by the Nx of the NOx adsorption catalyst.
It is input to the Ox purification rate estimation unit. This estimated NOx
When the purification rate becomes equal to or less than a predetermined value, a NOx reduction process is performed. 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 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 ( EG
R rate, EGR valve 31), fuel injection amount (injector 5), fuel injection timing, electric motor for assisting the output of the internal combustion engine, load on the generator provided in the engine,
The adjustment is made by any one or more means of the braking on the engine output side.

【００６５】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 exhaust gas purification control device described above 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).

【００６６】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１０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
ＮＯｘ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浄
化能力をＮＯｘ浄化率推定により、常時判定して、ＮＯ
ｘ浄化能力が低下した場合燃焼の空燃比等をリッチ側に
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 by a method described later to determine the operating air-fuel ratio, 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 spark plug 10 controlled by a signal from the ECU 25 and burns. The combustion exhaust gas is led to an exhaust purification system. The exhaust purification system is provided with a NOx adsorbing catalyst, and during stoichiometric operation, the NOx, HC, CO
In addition, during the lean operation, NOx is purified by the NOx adsorbing ability, and at the same time, the combustion function is provided.
Purifies C and CO. Further, based on the determination and control signal of the ECU, during lean operation, the NOx purification capacity of the NOx adsorption catalyst is constantly determined by estimating the NOx purification rate.
If the x-purification capacity decreases, the air-fuel ratio of the combustion is shifted to the rich side, or the fuel is injected into the cylinder during the expansion stroke or the exhaust stroke to recover the NOx adsorption ability of the adsorption catalyst. Through the above operation, the present apparatus effectively purifies exhaust gas under all engine combustion conditions of lean operation and stoichiometric (including rich) operation.

【００６７】[0067]

【発明の効果】本発明によれば、ＮＯｘ吸着触媒のＮＯ
ｘ浄化率を推定し、その推定値が所定値以下になった時
にＮＯｘ吸着触媒に吸着されたＮＯｘの還元処理を実施
するので有害排ガスを増加させることなく、長い間、Ｎ
Ｏｘを高効率で浄化できる。According to the present invention, the NOx adsorbing catalyst
x purification rate is estimated, and when the estimated value becomes equal to or less than a predetermined value, the reduction treatment of NOx adsorbed by the NOx adsorption catalyst is performed.
Ox can be purified with high efficiency.

【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
交互に繰返したときのＮＯｘ浄化率の経時特性。FIG. 2 is a time characteristic of the NOx purification rate when a rich operation and a lean operation are alternately repeated by the method of the present invention.

【図３】自動車の走行距離とＮＯｘ浄化率の関係。FIG. 3 shows the relationship between the mileage of an automobile and the NOx purification rate.

【図４】ストイキ排ガス中のＮＯｘ浄の化率。FIG. 4 shows the conversion rate of NOx 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。FIG. 5 shows 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。FIG. 6 shows 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７】エンジン制御システム。FIG. 7 is 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 (72)発明者 三浦 清 茨城県ひたちなか市大字高場2520番地 自 動車機器技術研究組合内 Ｆターム(参考） 3G091 AA02 AA11 AA12 AA17 AA23 AA24 AA28 AB03 AB06 AB09 BA11 BA14 BA15 BA19 BA33 BA39 CA17 CA18 CA19 CA26 CB02 CB03 CB05 CB07 CB08 DB06 DB10 DB13 DC01 EA01 EA03 EA04 EA05 EA06 EA07 EA17 EA18 EA21 EA30 EA31 EA33 EA34 EA38 EA39 FA18 FB10 FB11 FB12 FC02 GA01 GA03 GA06 GB01W GB01X GB02W GB03W GB04W GB05W GB06W GB07W GB10W GB10X HA18 HA36 HA37 HA39 HB05 HB08 HB09 3G301 HA01 HA04 HA13 HA15 HA18 JA15 JA25 JA26 JA33 JB09 LA03 LB02 LB04 MA01 MA11 MA18 MA19 MA20 MA23 MA26 NA04 NA06 NA08 NE01 NE06 NE11 NE12 NE13 NE14 NE15 PA01A PA01B PA01Z PA07A PA07B PA07Z PA11A PA11B PA11Z PD01A PD01B PD01Z PD02A PD02B PD02Z PD11A PD11B PD11Z PD12A PD12B PD12Z PE01A PE01B PE01Z PE03A PE03B PE03Z PE04A PE04B PE04Z PF01A PF01B PF01Z PF03A PF03B PF03Z PF11A PF11B PF11Z  ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kiyoshi Miura 2520 Odaiba, Hitachinaka-shi, Ibaraki F-term in the Automotive Equipment Research Association (reference) 3G091 AA02 AA11 AA12 AA17 AA23 AA24 AA28 AB03 AB06 AB09 BA11 BA14 BA15 BA19 BA33 BA39 CA17 CA18 CA19 CA26 CB02 CB03 CB05 CB07 CB08 DB06 DB10 DB13 DC01 EA01 EA03 EA04 EA05 EA06 EA07 EA17 EA18 EA21 EA30 EA31 EA33 EA34 EA38 EA39 FA18 FB10 FB11 FB12 GB01 GB03 GB01 GA03 GB01 GB03 HA37 HA39 HB05 HB08 HB09 3G301 HA01 HA04 HA13 HA15 HA18 JA15 JA25 JA26 JA33 JB09 LA03 LB02 LB04 MA01 MA11 MA18 MA19 MA20 MA23 MA26 NA04 NA06 NA08 NE01 NE06 NE11 NE12 NE13 NE14 NE15 PA01A PA01B PA01Z PA07A11 PD02 PD07 PD02 PD07 PD02Z PD11A PD11B PD11Z PD12A PD12B PD12Z PE01A PE01B PE01Z PE03A PE03B PE03Z PE04A PE04B PE04Z PF01A PF01B PF01Z PF03A PF03B PF03Z PF11A PF11B PF11Z

Claims (9)

【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、 内燃機関から排出されるＮＯｘ排出量と機関の運転状態
からＮＯｘ浄化率を推定し、その推定されたＮＯｘ浄化
率が所定値まで低下した時にＮＯｘ吸着触媒に吸着され
たＮＯｘの還元処理を行う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 The apparatus estimates a NOx purification rate from an amount of NOx emitted from an internal combustion engine and an operation state of the engine, and reduces the NOx adsorbed on the NOx adsorption catalyst when the estimated NOx purification rate decreases to a predetermined value. Do this Exhaust gas purification controller according to claim. 【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、 内燃機関から排出されるＮＯｘ排出量と機関の運転状態
からＮＯｘ浄化率を推定し、その推定されたＮＯｘ浄化
率が所定値まで低下した時にＮＯｘ吸着触媒に吸着され
たＮＯｘの還元処理を行う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. Te in the exhaust gas purifying apparatus for an internal combustion engine to harmless by reducing the N 2, to estimate the NOx purification rate from the operation state of the NOx emissions and engine discharged from the internal combustion engine, the estimated NOx purification ratio predetermined value An exhaust gas purification control device that performs a reduction process of NOx adsorbed on a NOx adsorption catalyst when the exhaust gas purification level has dropped to a level lower than the maximum value. 【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、 内燃機関から排出されるＮＯｘ排出量と機関の運転状態
からＮＯｘ浄化率を推定し、その推定されたＮＯｘ浄化
率が所定値まで低下した時にＮＯｘ吸着触媒に吸着され
たＮＯｘの還元処理を行う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
r) and a NOx adsorption catalyst containing at least one element selected from calcium (Ca) as a part of the components is disposed in the exhaust gas flow path. Create a state with a large amount of oxidizing agent and trap NOx 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, Estimating the NOx purification rate from the amount of NOx exhausted from the internal combustion engine and the operating state of the engine, and performing a reduction process of the NOx adsorbed on the NOx adsorption catalyst when the estimated NOx purification rate decreases to a predetermined value. An exhaust gas purification control device characterized by the above-mentioned. 【請求項４】請求項１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ガス浄化装置。4. The method according to claim 1, wherein at least one selected from potassium (K), sodium (Na), magnesium (Mg), strontium (Sr) and calcium (Ca) and at least one selected from rare earths composed of cerium and the like. And a composition comprising a metal and a metal oxide (or composite oxide) containing at least one element selected from precious metals such as platinum, rhodium, palladium and the like, or the composition supported on a porous heat-resistant metal oxide An exhaust gas purifying apparatus using the composition obtained as an adsorption catalyst. 【請求項５】請求項１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ガス浄化装置。5. The method according to claim 1, wherein at least one selected from potassium (K), sodium (Na), magnesium (Mg), strontium (Sr), and calcium (Ca) and at least one selected from rare earths composed of cerium or the like. A composition comprising a metal and a metal oxide (or composite oxide) containing at least one selected from noble metals such as platinum, rhodium, palladium, and at least one element selected from titanium and silicon; An exhaust gas purifying apparatus using, as an adsorption catalyst, a composition obtained by supporting a substance 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
うことを特徴とする排ガス浄化制御装置。6. The method according to claim 1, wherein the NOx
An exhaust gas purification control device characterized in that the reduction treatment of NOx adsorbed on an adsorption catalyst is performed by increasing the concentration of unburned hydrocarbons in exhaust gas flowing into the catalyst. 【請求項７】請求項１から５の何れかにおいて、内燃機
関から排出されるＮＯｘ排出量と機関の運転状態からＮ
Ｏｘ浄化率を推定する方法として、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ＮＯｘ吸着触媒のＮＯｘ浄化率を推定する
排ガス浄化装置。7. The method according to claim 1, wherein the amount of NOx discharged from the internal combustion engine and the operating state of the engine are determined based on N
As a method of estimating the Ox purification rate, the amount of NOx adsorbed on the NOx adsorption catalyst, the exhaust temperature, the temperature of the adsorption catalyst,
Sulfur poisoning amount, car mileage, degree of catalyst deterioration, air-fuel ratio, unburned hydrocarbon concentration, NOx concentration before catalyst, stoichiometric (stoichiometric air-fuel ratio), or lean after changing from rich operation to lean operation An exhaust gas purifying device for estimating the NOx purification rate of a NOx adsorption catalyst from at least one of state quantities of an operation elapsed time, a rotation speed of an internal combustion engine, a load of the engine, an intake air amount, and an exhaust gas amount. 【請求項８】請求項１から７の何れかにおいて、ＮＯｘ
吸着触媒に吸着されたＮＯｘの還元処理の時に内燃機関
のトルク変動が生じる場合はそのトルク変動を抑制する
方向に内燃機関の出力トルクを調整する排気浄化装置。8. The method according to claim 1, wherein the NOx
An exhaust purification device that adjusts the output torque of an internal combustion engine in a direction to suppress the torque fluctuation when the torque fluctuation of the internal combustion engine occurs during the reduction process of NOx adsorbed on the adsorption catalyst. 【請求項９】請求項８において、出力トルクの調整を点
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つ以上の手段により実施する排気浄化制
御装置。9. An engine according to claim 8, wherein the output torque is adjusted by adjusting an ignition timing, an intake air amount, an amount of a part of exhaust gas mixed with intake air of the internal combustion engine (EGR rate), a fuel injection amount, a fuel injection timing, and an internal combustion engine. An exhaust gas purification control device implemented by at least one of an electric motor for assisting output, a load on a generator provided in the engine, and braking on an output side of the engine.
JP11223418A 1999-08-06 1999-08-06 Exhaust gas emission control system Pending JP2001050042A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP11223418A JP2001050042A (en) 1999-08-06 1999-08-06 Exhaust gas emission control system
DE10038227A DE10038227A1 (en) 1999-08-06 2000-08-04 Exhaust gas purification device comprises nitrogen oxides adsorption catalyst arranged in exhaust gas channel of engine and control unit
US09/989,204 US20020050135A1 (en) 1999-08-06 2001-11-21 Apparatus for purifying and controlling exhaust gases

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP11223418A JP2001050042A (en) 1999-08-06 1999-08-06 Exhaust gas emission control system

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JP (1) JP2001050042A (en)
DE (1) DE10038227A1 (en)

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JP2006214320A (en) * 2005-02-02 2006-08-17 Honda Motor Co Ltd Exhaust emission control device of internal combustion engine
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JP2011012687A (en) * 2010-10-21 2011-01-20 Denso Corp Engine torque control device

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EP1245817A3 (en) * 2001-03-30 2003-01-02 Mazda Motor Corporation Apparatus for and method of purifying exhaust gas and method of injecting fuel for diesel engine
JP3828425B2 (en) 2002-01-08 2006-10-04 三菱電機株式会社 Exhaust gas purification method for internal combustion engine
DE10216260B4 (en) * 2002-04-12 2005-04-21 Siemens Ag Method for operating an internal combustion engine
DE10216278B4 (en) * 2002-04-12 2005-05-04 Siemens Ag Method for determining a NOx concentration
ATE344382T1 (en) * 2003-02-05 2006-11-15 Volkswagen Ag METHOD FOR DESIGNING A CATALYST SYSTEM
US7155331B1 (en) 2003-12-15 2006-12-26 Donaldson Company, Inc. Method of prediction of NOx mass flow in exhaust
US8474243B2 (en) * 2006-12-22 2013-07-02 Cummins, Inc. System for controlling regeneration of an adsorber
DE102009058713A1 (en) * 2009-12-17 2011-06-22 Deutz Ag, 51149 Method for exhaust gas recirculation
US9708950B2 (en) * 2015-02-26 2017-07-18 Cummins Power Generation Ip, Inc. Genset engine using electrical sensing to control components for optimized performance
JP7444104B2 (en) * 2021-02-24 2024-03-06 トヨタ自動車株式会社 Internal combustion engine control device

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Publication number Priority date Publication date Assignee Title
JP2006214320A (en) * 2005-02-02 2006-08-17 Honda Motor Co Ltd Exhaust emission control device of internal combustion engine
JP4510654B2 (en) * 2005-02-02 2010-07-28 本田技研工業株式会社 Exhaust gas purification device for internal combustion engine
JP2008144689A (en) * 2006-12-12 2008-06-26 Denso Corp Engine torque control device and its adjusting method
JP4645585B2 (en) * 2006-12-12 2011-03-09 株式会社デンソー Engine torque control device
JP2011012687A (en) * 2010-10-21 2011-01-20 Denso Corp Engine torque control device

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