JPH1054310A - Intake control device for internal combustion engine - Google Patents

Intake control device for internal combustion engine

Info

Publication number
JPH1054310A
JPH1054310A JP8214853A JP21485396A JPH1054310A JP H1054310 A JPH1054310 A JP H1054310A JP 8214853 A JP8214853 A JP 8214853A JP 21485396 A JP21485396 A JP 21485396A JP H1054310 A JPH1054310 A JP H1054310A
Authority
JP
Japan
Prior art keywords
fuel
amount
mixture
air
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.)
Granted
Application number
JP8214853A
Other languages
Japanese (ja)
Other versions
JP3509404B2 (en
Inventor
Nobutaka Takahashi
伸孝 高橋
Keisuke Suzuki
敬介 鈴木
Takeaki Obata
武昭 小幡
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.)
Nissan Motor Co Ltd
Original Assignee
Nissan Motor Co 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 Nissan Motor Co Ltd filed Critical Nissan Motor Co Ltd
Priority to JP21485396A priority Critical patent/JP3509404B2/en
Priority to KR1019970036413A priority patent/KR100209176B1/en
Priority to US08/903,952 priority patent/US6012435A/en
Publication of JPH1054310A publication Critical patent/JPH1054310A/en
Application granted granted Critical
Publication of JP3509404B2 publication Critical patent/JP3509404B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • Y02T10/12—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

  • Exhaust Gas After Treatment (AREA)
  • Supplying Secondary Fuel Or The Like To Fuel, Air Or Fuel-Air Mixtures (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

PROBLEM TO BE SOLVED: To simultaneously attain processing of vaporized fuel and reducing of NOx in an internal combustion engine. SOLUTION: Combustion is judged for whether it is stratified mixture combustion or uniform mixture combustion (step 301), at stratified mixture combustion time, when a purge of vaporized fuel is judged necessary, a discharge amount of NOx is calculated (step 302 to 305). A required amount of HC as a reducing agent matched with the discharge amount of NOx is calculated (step 306), an actual required purge amount of vaporized fuel is determined (step 307), a purge control valve for controlling a vaporized fuel supply amount is controlled (step 308).

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、少なくとも所定の
運転条件で成層化した混合気を燃焼室内に形成して燃焼
を行うと共に、蒸発燃料を吸気系に供給して処理する装
置を備えた内燃機関において、蒸発燃料の供給によって
吸気を制御する技術に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion system provided with a device for performing combustion by forming a stratified air-fuel mixture in at least a predetermined operating condition in a combustion chamber and supplying evaporative fuel to an intake system for processing. The present invention relates to a technique for controlling intake air by supplying evaporated fuel in an engine.

【０００２】[0002]

【従来の技術】内燃機関において、所定の運転条件の領
域では、機関の燃焼室内の点火プラグ付近には可燃混合
気の混合気層を、それ以外の領域では空気層を形成する
成層化混合気を形成し、成層混合気による燃焼を行うよ
うにしたものが公知である。例えば、燃焼室内に直接燃
料を噴射する火花点火式機関として、特開平４−２４１
７５４号に示されるものがある。2. Description of the Related Art In an internal combustion engine, a stratified mixture which forms a combustible mixture in the vicinity of a spark plug in a combustion chamber of the engine in a region of a predetermined operating condition and an air layer in other regions. Is known, and combustion by a stratified mixture is performed. For example, as a spark ignition type engine that directly injects fuel into a combustion chamber, Japanese Patent Laid-Open No. 4-241 is disclosed.
No. 754.

【０００３】また、燃料タンク内などで蒸発した燃料が
大気中に拡散されないように、これを容器 (キャニス
タ) に収められた活性炭等の吸着剤に吸着させて保持
し、状況に応じこれを放出させて吸気に混合し、機関に
供給することにより、蒸発燃料を消費するシステムも公
知である。しかし、前記成層化混合気を生成する運転条
件が存在する内燃機関の場合は、このキャニスタに溜め
られ、吸気系に放出 (パージ) される蒸発燃料は、吸気
に混合させられるため、成層化混合気の空気層にも蒸発
燃料が混入することになる。この蒸発燃料が混入した空
気層の混合比は、通常可燃混合比を大きく上回ってリー
ンとなっているため、可燃混合気層で形成された燃焼火
炎は、この空気層に進行することなく消えることにな
り、空気層に含まれる蒸発燃料はそのまま燃焼室から排
出されることになる。Further, in order to prevent the fuel evaporated in the fuel tank or the like from being diffused into the atmosphere, the fuel is adsorbed on an adsorbent such as activated carbon contained in a container (canister), held and released according to the situation. There is also known a system that consumes evaporated fuel by mixing it with intake air and supplying it to an engine. However, in the case of an internal combustion engine having operating conditions for generating the stratified mixture, the evaporated fuel stored in the canister and discharged (purged) into the intake system is mixed with the intake air. Evaporated fuel is also mixed into the air layer of the air. Since the mixture ratio of the air layer in which the evaporated fuel is mixed is usually much higher than the combustible mixture ratio and lean, the combustion flame formed in the combustible mixture layer disappears without proceeding to this air layer. And the fuel vapor contained in the air layer is directly discharged from the combustion chamber.

【０００４】したがって、成層燃焼中にむやみにパージ
を行うと、排気中に不要なＨＣ成分を放出することとな
るため、排気浄化の観点から必ずしも望ましいこととは
いえない。このため、特開平５−２２３０１７号に示さ
れるものでは、成層燃焼を行うような低・中負荷領域に
おいては、蒸発燃料のパージを行わない構成を提案して
いる。Therefore, if the purging is performed during the stratified charge combustion, unnecessary HC components are released into the exhaust gas, which is not always desirable from the viewpoint of exhaust gas purification. For this reason, Japanese Patent Application Laid-Open No. H5-223017 proposes a configuration in which the fuel vapor is not purged in a low / medium load region where stratified combustion is performed.

【０００５】[0005]

【発明が解決しようとする課題】しかしながら、前記特
開平５−２２３０１７号に示されるような構成を採用し
た場合、低負荷の運転が継続して行われる状態では、蒸
発燃料は、パージされる機会がないまま、キャニスタに
蓄えられ続けることになる。つまり、キャニスタの容量
を超えても、蒸発燃料が供給され続けることになるた
め、できれば大きなキャニスタを設けるべきであるが、
重量やレイアウトの関係で問題となる。However, in the case where the configuration as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. Hei 5-223017 is employed, in the state where the low-load operation is continuously performed, the evaporated fuel has an opportunity to be purged. Without being stored in the canister. In other words, even if the capacity of the canister is exceeded, the supply of evaporated fuel will continue, so a large canister should be provided if possible.
This is a problem in terms of weight and layout.

【０００６】本発明は、このような従来の問題点に鑑み
なされたもので、蒸発燃料のパージを適正に行うことに
より、蒸発燃料の消費率を高められると共に、該蒸発燃
料をパージによって窒素酸化物 (ＮＯｘ) の浄化性能を
も向上できるようにした内燃機関の吸気制御装置を提供
することを目的とする。SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. By properly purging evaporated fuel, the consumption rate of the evaporated fuel can be increased, and the evaporated fuel can be purged by nitrogen oxidation. It is an object of the present invention to provide an intake control device for an internal combustion engine that can improve the purification performance of substances (NOx).

【０００７】[0007]

【課題を解決するための手段】このため、請求項１に係
る発明は、少なくとも所定の条件で、燃焼室内に混合気
層と空気層との成層化状態を形成して燃焼を行う成層混
合気燃焼を行う一方、燃料系からの蒸発燃料を所定の条
件で吸気系に供給するようにし、かつ、排気系に排気浄
化用の触媒を備えた内燃機関の吸気制御装置において、
前記成層混合気燃焼時に、燃焼室から排出される窒素酸
化物の排出量に応じた量の蒸発燃料を吸気系に供給し、
蒸発燃料の炭化水素成分を成層混合気の空気層に混入さ
せて未燃焼のまま排気系に排出させ、前記触媒にて窒素
酸化物の還元に供するようにしたことを特徴とする。For this reason, the invention according to claim 1 provides a stratified mixture in which a stratified state of an air-fuel mixture layer and an air layer is formed in a combustion chamber at least under predetermined conditions to perform combustion. On the other hand, in the intake control device of the internal combustion engine, while performing combustion, the fuel evaporated from the fuel system is supplied to the intake system under predetermined conditions, and the exhaust system is provided with a catalyst for purifying exhaust gas.
At the time of the stratified mixture combustion, supplying an amount of fuel vapor to the intake system in accordance with the amount of nitrogen oxides discharged from the combustion chamber,
A hydrocarbon component of the evaporated fuel is mixed into an air layer of a stratified mixture, discharged to an exhaust system without being burned, and used for reduction of nitrogen oxides by the catalyst.

【０００８】(作用・効果)成層混合気燃焼時には、燃焼
室内が混合気層と空気層とに成層化され、このとき蒸発
燃料を吸気系に供給すると、燃焼室内で蒸発燃料が混入
した空気層の混合比は、通常可燃混合比を大きく上回っ
てリーンとなっているため、可燃混合気層で形成された
燃焼火炎が空気層に進行することなく、空気層に含まれ
る蒸発燃料は未燃焼のまま燃焼室から排出されることに
なる。(Operation / Effect) During the stratified mixture combustion, the combustion chamber is stratified into an air-fuel mixture layer and an air layer. At this time, when the fuel vapor is supplied to the intake system, the air layer mixed with the fuel vapor within the combustion chamber is formed. The mixture ratio is usually much higher than the combustible mixture ratio and lean, so that the combustion flame formed in the combustible mixture layer does not advance to the air layer, and the evaporative fuel contained in the air layer is unburned. It will be discharged from the combustion chamber as it is.

【０００９】そして、上記のように未燃焼のまま排出さ
れた蒸発燃料中の炭化水素成分の少なくとも一部は、排
気浄化用の触媒において排気中の窒素酸化物を還元させ
つつ炭化水素自身は酸化されてＨ2 Ｏ，ＣＯ2 となって
浄化処理され、窒素酸化物は還元されて窒素分子となっ
て浄化処理されるように反応するので、窒素酸化物の排
出量に応じた量の蒸発燃料を供給することにより、該蒸
発燃料と窒素酸化物とを同時に効果的に処理することが
できる。[0009] At least a part of the hydrocarbon component in the evaporative fuel discharged unburned as described above is oxidized while reducing the nitrogen oxides in the exhaust gas by the exhaust purification catalyst. The nitrogen oxides are converted to H 2 O and CO 2 and purified, and the nitrogen oxides are reduced to nitrogen molecules and reacted so that the purification processing is performed. , The evaporated fuel and the nitrogen oxide can be simultaneously and effectively treated.

【００１０】また、請求項２に係る発明は、図１に示す
ように、燃焼室内に混合気層と空気層との成層化状態を
形成して燃焼を行う成層混合気燃焼と、燃焼室内に均質
な混合気を形成して燃焼を行う均質混合気燃焼と、を、
機関の運転条件に応じて切り換えて行う混合気形成切換
手段と、燃料供給系から蒸発した燃料を、機関の吸気系
に供給する蒸発燃料供給手段と、前記蒸発燃料の吸気系
への供給量を制御する蒸発燃料供給量制御手段と、燃焼
室から排出される窒素酸化物の量を算出する窒素酸化物
排出量算出手段と、前記窒素酸化物排出量算出手段によ
り算出された窒素酸化物排出量に対し、機関の排気系に
介装された排気浄化用の触媒で窒素酸化物の還元を行う
のに必要な炭化水素量を算出する還元剤要求量算出手段
と、成層混合気燃焼時に、前記還元剤要求量に応じた量
の蒸発燃料を吸気系に供給するように供給量を設定する
蒸発燃料供給量設定手段と、を含んで構成され、前記成
層混合気燃焼時に吸気系に供給された蒸発燃料の炭化水
素成分を成層混合気の空気層に混入させて未燃焼のまま
排気系に排出させ、窒素酸化物の還元に供するようにし
たことを特徴とする。The invention according to a second aspect of the present invention provides a stratified mixture combustion in which a stratified state of an air-fuel mixture layer and an air layer is formed in a combustion chamber to perform combustion, as shown in FIG. Homogeneous mixture combustion, which forms a homogeneous mixture and performs combustion,
An air-fuel mixture formation switching unit that performs switching in accordance with operating conditions of the engine, an evaporative fuel supply unit that supplies fuel evaporated from the fuel supply system to an intake system of the engine, and a supply amount of the evaporative fuel to the intake system. Controlling means for controlling the amount of supply of evaporated fuel, controlling means for calculating the amount of nitrogen oxides discharged from the combustion chamber, and controlling the amount of nitrogen oxides calculated by the means for calculating nitrogen oxide emissions On the other hand, a reducing agent required amount calculating means for calculating the amount of hydrocarbons required to reduce nitrogen oxides with an exhaust purification catalyst interposed in the exhaust system of the engine, and at the time of stratified mixture combustion, Evaporative fuel supply amount setting means for setting the supply amount so as to supply the evaporative fuel in an amount corresponding to the required amount of the reducing agent to the intake system, and the evaporative fuel is supplied to the intake system during the stratified mixture combustion. Stratified mixing of hydrocarbon components of evaporated fuel Is mixed into the air layer was drained to leave the exhaust system unburned, characterized in that as subjected to the reduction of nitrogen oxides.

【００１１】(作用・効果)窒素酸化物算出手段は、燃焼
室からの窒素酸化物の排出量を算出し、還元剤要求量算
出手段は、触媒において前記算出された排出量分の窒素
酸化物と酸化還元反応するのに必要な還元剤としての炭
化水素 (ＨＣ) の要求量を算出する。蒸発燃料供給量設
定手段は、この還元剤要求量に基づいて、成層混合気燃
焼時に窒素酸化物の還元剤となる蒸発燃料の供給量を設
定し、蒸発燃料供給量制御手段は、該設定された量の蒸
発燃料が吸気系に供給されるように、蒸発燃料供給量を
制御する。(Function / Effect) The nitrogen oxide calculating means calculates the amount of nitrogen oxide emission from the combustion chamber, and the reducing agent required amount calculating means calculates the amount of nitrogen oxide corresponding to the calculated emission amount in the catalyst. Calculate the required amount of hydrocarbon (HC) as a reducing agent required for the oxidation-reduction reaction. The evaporative fuel supply amount setting means sets the supply amount of the evaporative fuel which becomes the reducing agent of the nitrogen oxide during the stratified mixture combustion based on the required amount of the reducing agent, and the evaporative fuel supply amount control means sets the set amount of the evaporative fuel supply amount. The evaporative fuel supply amount is controlled so that an appropriate amount of evaporative fuel is supplied to the intake system.

【００１２】このように、窒素酸化物の排出量に応じた
量の蒸発燃料を供給することにより、該蒸発燃料と窒素
酸化物とを同時に効果的に処理することができる。ま
た、請求項３に係る発明は、前記窒素酸化物排出量算出
手段は、機関の運転状態、混合気の空燃比及び燃料噴射
時期に基づいて窒素酸化物の排出量を算出することを特
徴とする。As described above, by supplying the evaporated fuel in an amount corresponding to the emission amount of the nitrogen oxide, the evaporated fuel and the nitrogen oxide can be effectively and simultaneously treated. The invention according to claim 3 is characterized in that the nitrogen oxide emission calculating means calculates the nitrogen oxide emission based on the operating state of the engine, the air-fuel ratio of the air-fuel mixture, and the fuel injection timing. I do.

【００１３】(作用・効果)窒素酸化物の排出量を、機関
の回転速度や負荷といった運転状態と、燃焼室に供給さ
れる混合気の空燃比及び燃料噴射時期といった窒素酸化
物の生成に影響の大きい要素に基づいて高精度に推定し
て算出することができる。また、請求項４に係る発明
は、図１に一点鎖線で示すように、前記蒸発燃料供給手
段は、燃料系から蒸発した燃料を一時的に蓄積する蒸発
燃料蓄積部を備え、前記蒸発燃料蓄積部における蒸発燃
料の蓄積量を算出する蒸発燃料蓄積量算出手段を含んで
構成され、前記成層混合気燃焼時の蒸発燃料の供給は、
前記蒸発燃料の蓄積量が限界値付近となったときに、行
うようにしたことを特徴とする。(Function / Effect) The amount of emission of nitrogen oxides affects the operating conditions such as the engine speed and load and the generation of nitrogen oxides such as the air-fuel ratio and the fuel injection timing of the air-fuel mixture supplied to the combustion chamber. Can be estimated and calculated with high accuracy based on the element having a large value. According to a fourth aspect of the present invention, as shown by a dashed line in FIG. 1, the evaporative fuel supply means includes an evaporative fuel accumulator for temporarily accumulating fuel evaporated from a fuel system, The fuel cell system further includes an evaporative fuel accumulation amount calculating unit that calculates an evaporative fuel accumulation amount in the unit, and the supply of the evaporative fuel during the stratified mixture combustion is performed,
The method is performed when the accumulated amount of the fuel vapor is near the limit value.

【００１４】(作用・効果)このようにすることにより、
成層混合気燃焼において、敢えて蒸発燃料の吸気系への
パージを行う条件を限定している。つまり、蒸発燃料量
が蓄積可能な量の限界値に近づいた場合において、パー
ジを行うこととする。これには、以下の２つの目標・効
果がある。(Action / Effect) By doing so,
In stratified mixture combustion, the conditions for purging evaporated fuel to the intake system are limited. That is, purging is performed when the amount of fuel vapor approaches the limit value of the amount that can be accumulated. This has the following two goals and effects.

【００１５】(1) １つは、蒸発燃料蓄積部 (例えばキャ
ニスタの活性炭層) 内に蒸発燃料を蓄える余裕がある場
合は、必ずしも蒸発燃料の処理を必要としていないため
である。 (2）別の理由として、蒸発燃料量の制御は、実際にはパ
ージ用の空気と混合させたパージ混合気の量を制御して
なされるものであり、直接蒸発燃料量を制御するもので
はない。したがって、蒸発燃料蓄積部に蓄積されている
燃料量により、実際に吸気系に導入される蒸発燃料量
は、変化してしまう。その場合、蒸発燃料蓄積部に十分
に蒸発燃料が蓄積保持されている場合は、供給量制御部
材 (パージ制御弁等) の操作量に対する蒸発燃料の供給
量が比較的精度良く推定でき、蒸発燃料の吸気への混合
量の制御を比較的高精度に行えるためである。(1) One is that if there is room to store the evaporated fuel in the evaporated fuel storage section (for example, the activated carbon layer of the canister), it is not necessary to treat the evaporated fuel. (2) As another reason, the control of the amount of evaporated fuel is actually performed by controlling the amount of the purge air-fuel mixture mixed with the air for purging, and is not directly controlled by the amount of the evaporated fuel. Absent. Therefore, the amount of fuel vapor actually introduced into the intake system changes depending on the amount of fuel stored in the fuel vapor storage unit. In such a case, if the fuel vapor is sufficiently accumulated and held in the fuel vapor storage unit, the supply amount of the fuel vapor with respect to the operation amount of the supply amount control member (purge control valve, etc.) can be estimated relatively accurately, and the fuel vapor amount can be estimated relatively accurately. This is because the control of the amount of mixture into the intake air can be performed with relatively high accuracy.

【００１６】また、請求項５に係る発明は、前記成層混
合気燃焼時の蒸発燃料の供給は、前記窒素酸化物排出量
算出手段によって算出される窒素酸化物排出量が所定以
上のときに、行うようにしたことを特徴とする。 (作用・効果)請求項４に係る発明と同様に、成層混合気
燃焼時において、敢えて蒸発燃料の吸気系へのパージを
行う条件を限定している。つまり、窒素酸化物排出量算
出手段により得られた窒素酸化物の排出量が比較的多い
場合において、成層混合気燃焼時であってもパージを行
うこととする。これにより、既述したように、何らかの
要求によって窒素酸化物の排出量が多めになった場合で
も、触媒下流に排出される窒素酸化物の量を低減でき
る。According to a fifth aspect of the present invention, the supply of the evaporated fuel during the combustion of the stratified mixture is performed when the nitrogen oxide emission calculated by the nitrogen oxide emission calculation means is equal to or more than a predetermined value. It is characterized by performing. (Operation / Effect) As in the case of the invention according to the fourth aspect, the conditions for purging the fuel vapor to the intake system during the stratified mixture combustion are limited. In other words, when the nitrogen oxide emission amount obtained by the nitrogen oxide emission amount calculation means is relatively large, purging is performed even during stratified mixture combustion. As a result, as described above, even if the amount of nitrogen oxide emission is increased due to some request, the amount of nitrogen oxide exhausted downstream of the catalyst can be reduced.

【００１７】但し、通常機関においてはＥＧＲシステム
などにより、窒素酸化物の総排出量は、このような排出
量が増加するような場合も考慮して設計され、総量とし
て所望の量以下となるように設計されているため、かか
る操作は、必要性の高い効果というより、より環境保全
等に効果を持つ方の意味合いが大きい。また、請求項６
に係る発明は、前記成層混合気燃焼時の蒸発燃料の供給
は、燃焼安定度の悪化に起因して混合気の設定空燃比を
リッチ補正しているときに、行うようにしたことを特徴
とする。However, in an ordinary engine, the total amount of nitrogen oxides is designed by an EGR system or the like in consideration of such an increase in the amount of nitrogen oxides. Since such an operation is designed to be more effective, it is more meaningful to have an effect on environmental preservation and the like than an effect having a high necessity. Claim 6
The invention according to the invention is characterized in that the supply of the evaporated fuel during the stratified mixture combustion is performed when the set air-fuel ratio of the mixture is richly corrected due to the deterioration of the combustion stability. I do.

【００１８】(作用・効果)成層混合気燃焼時にあって、
燃焼安定度の悪化に起因して混合気の空燃比を設定値に
対してリッチ補正している場合、窒素酸化物の排出量
は、増加する傾向を持つ。つまり、前記請求項５に係る
発明の (作用・効果) で説明した状況に相当する。そこ
で、この際には、成層混合気燃焼時であっても、蒸発燃
料をパージさせれば、窒素酸化物と触媒で反応して処理
できると同時に触媒下流の窒素酸化物を低減することが
できる。(Operation / Effect) At the time of stratified mixture combustion,
When the air-fuel ratio of the air-fuel mixture is richly corrected with respect to the set value due to the deterioration of the combustion stability, the emission amount of nitrogen oxide tends to increase. In other words, this corresponds to the situation described in the (action / effect) of the invention according to claim 5. Therefore, in this case, even in the case of stratified mixture combustion, if the fuel vapor is purged, it is possible to react and process the nitrogen oxides with the catalyst and to reduce the nitrogen oxides downstream of the catalyst. .

【００１９】また、請求項７に係る発明は、図１に点線
で示すように、前記排気浄化用触媒の活性状態を判断す
る触媒活性状態判断手段を含んで構成され、前記成層混
合気燃焼時の蒸発燃料の供給は、窒素酸化物の還元が進
行するには触媒活性が十分でないと判断されたときは、
禁止するようにしたことを特徴とする。Further, the invention according to claim 7 includes, as indicated by a dotted line in FIG. 1, a catalyst activation state judging means for judging an activation state of the exhaust gas purifying catalyst. When it is determined that the catalytic activity is not enough for the reduction of nitrogen oxides to proceed,
The feature is that it is prohibited.

【００２０】(作用・効果)前記成層混合気燃焼時の蒸発
燃料パージによる効果は、全て触媒が正常に機能してい
ることが前提となる。したがって、触媒の活性状態を判
断して、炭化水素を供給したときに確実に窒素酸化物が
還元される必要条件として、触媒が十分活性化されたと
判断された場合のみ、蒸発燃料の供給を行うことによ
り、既述した各効果を確実に発揮することができる。(Operation and Effect) The effect of the fuel vapor purge during the combustion of the stratified mixture is based on the premise that the catalyst functions normally. Therefore, the activation state of the catalyst is determined, and the supply of the evaporated fuel is performed only when it is determined that the catalyst has been sufficiently activated as a necessary condition for reliably reducing the nitrogen oxides when the hydrocarbon is supplied. Thus, the effects described above can be reliably achieved.

【００２１】また、請求項８に係る発明は、前記蒸発燃
料供給量設定手段は、前記還元剤要求量算出手段により
算出された還元剤要求量に対して、蒸発燃料の供給量を
少なめとなるように設定することを特徴とする。 (作用・効果)還元剤要求量算出手段により算出された要
求量に対し、少なくとも少なめとなるように蒸発燃料を
吸気系に供給することにより、少なくとも窒素酸化物の
一部を還元できる効果を得られると共に、窒素酸化物の
排出量の推定に誤差が生じたとしても、炭化水素を過剰
に供給し、排出してしまうことを防止できる。Further, in the invention according to claim 8, the evaporative fuel supply amount setting means makes the supply amount of the evaporative fuel smaller than the required reducing agent amount calculated by the required reducing agent amount calculating means. It is characterized by setting as follows. (Operation / Effect) By supplying the fuel vapor to the intake system so as to be at least slightly smaller than the required amount calculated by the required amount of reducing agent, an effect capable of reducing at least a part of nitrogen oxides is obtained. In addition, even if an error occurs in the estimation of the emission amount of nitrogen oxides, it is possible to prevent excessive supply and emission of hydrocarbons.

【００２２】また、請求項９に係る発明は、前記蒸発燃
料供給量設定手段は、空燃比のリーン度合いの大きい成
層混合気燃焼時に、蒸発燃料中の炭化水素のうち、排気
中の酸素と反応せず、窒素酸化物と還元反応を行うもの
の割合に基づいて、蒸発燃料の供給量を設定することを
特徴とする。According to a ninth aspect of the present invention, the evaporative fuel supply amount setting means reacts with the oxygen in the exhaust gas out of the hydrocarbons in the evaporative fuel during the combustion of a stratified mixture having a large lean air-fuel ratio. Instead, the supply amount of the evaporated fuel is set based on the ratio of the one that performs the reduction reaction with the nitrogen oxide.

【００２３】(作用・効果)還元剤要求量算出手段は、空
燃比リーン度合いが大きい状態において触媒に供給され
た蒸発燃料中の炭化水素のうち、排気中の酸素と反応せ
ず、窒素酸化物を還元させる反応割合より算出すること
により、排出される窒素酸化物と反応するために必要な
適正な還元剤量を算出できる効果を持つ。(Operation / Effect) The required amount of the reducing agent is calculated by the means for calculating the required amount of the reducing agent which does not react with the oxygen in the exhaust gas out of the hydrocarbons in the fuel vapor supplied to the catalyst when the air-fuel ratio lean degree is large. Calculating from the reaction rate for reducing the amount of the reducing agent has the effect of calculating the appropriate amount of reducing agent required to react with the exhausted nitrogen oxides.

【００２４】また、請求項10に係る発明は、前記窒素酸
化物排出量算出手段は、機関の運転状態と、混合気の空
燃比とに基づいて窒素酸化物の基本排出量を求め、該基
本排出量を燃料噴射時期で補正して算出することを特徴
とする。 (作用・効果)窒素酸化物排出量の算出を、比較的簡単な
構成で、かつ、精度良く算出することができる。According to a tenth aspect of the present invention, the nitrogen oxide emission calculating means obtains a basic nitrogen oxide emission based on an operating state of the engine and an air-fuel ratio of the air-fuel mixture. It is characterized in that the emission amount is corrected and calculated based on the fuel injection timing. (Operation / Effect) The calculation of the amount of nitrogen oxide emission can be performed with a relatively simple configuration and with high accuracy.

【００２５】[0025]

【発明の実施の形態】以下に、本発明の実施形態を図に
基づいて説明する。図２は、一実施形態のシステム構成
を示す。図において、内燃機関１の吸気通路２には、吸
入空気流量Ｑを検出するエアフローメータ３が設けら
れ、また、該吸入空気流量Ｑを調整するスロットル弁
４、該スロットル弁４をバイパスする補助空気通路５、
該補助空気通路５を流れる補助空気流量を制御する補助
空気量制御弁６が設けられている。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a system configuration of an embodiment. In the drawing, an air flow meter 3 for detecting an intake air flow rate Q is provided in an intake passage 2 of an internal combustion engine 1, a throttle valve 4 for adjusting the intake air flow rate Q, and an auxiliary air bypassing the throttle valve 4. Passage 5,
An auxiliary air amount control valve 6 for controlling an auxiliary air flow rate flowing through the auxiliary air passage 5 is provided.

【００２６】また、機関１のシリンダ部には、燃焼室７
内に燃料を噴射する燃料噴射弁８、燃焼室７内で火花点
火を行う点火プラグ９が設けられる。さらに、機関１の
排気通路10には、排気中の酸素濃度等から混合気の空燃
比を検出する空燃比センサ11が設けられ、下流部分に
は、ＨＣ，ＣＯ，ＮＯｘ等の排気汚染物質を浄化するた
めの排気浄化用触媒 (三元触媒) 21が介装されている。The combustion chamber 7 is provided in the cylinder of the engine 1.
A fuel injection valve 8 for injecting fuel into the fuel cell and a spark plug 9 for performing spark ignition in the combustion chamber 7 are provided. Further, an exhaust passage 10 of the engine 1 is provided with an air-fuel ratio sensor 11 for detecting an air-fuel ratio of an air-fuel mixture based on an oxygen concentration or the like in exhaust gas. An exhaust pollutant such as HC, CO, and NOx is provided in a downstream portion. An exhaust purification catalyst (three-way catalyst) 21 for purification is interposed.

【００２７】この他、機関のクランク角位置や機関回転
速度Ｎｅを検出するためのクランク角センサ12、機関冷
却水温度を検出する図示しない水温センサ等が設けられ
る。また、燃料タンク13から蒸発した燃料を導く蒸発燃
料通路14、該蒸発燃料通路14を介して導かれた蒸発燃料
を一時吸着して蓄える蒸発燃料蓄積部としての活性炭層
15、該活性炭層15を内蔵したキャニスタ16、前記スロッ
トル弁４上流の吸気通路２から前記キャニスタ16内の活
性炭層15に蒸発燃料パージ用の空気を導くためのパージ
エア導入通路17、活性炭層15から放出された蒸発燃料を
前記スロットル弁４下流の吸気通路２に導くためのパー
ジ通路18、該パージ通路18の流路面積を制御して蒸発燃
料のパージ量を制御するパージ制御弁19が設けられ、こ
れらによって蒸発燃料処理系が構成されている。なお、
蒸発燃料通路14、キャニスタ16、パージエア導入通路1
7、パージ通路18は、蒸発燃料供給手段を構成し、パー
ジ制御弁19と後述するコントロールユニット20とは、蒸
発燃料供給量制御手段を構成する。In addition, a crank angle sensor 12 for detecting the crank angle position of the engine and the engine rotation speed Ne, a water temperature sensor (not shown) for detecting the temperature of the engine cooling water, and the like are provided. Further, an evaporative fuel passage 14 for guiding the fuel evaporated from the fuel tank 13, and an activated carbon layer as an evaporative fuel storage part for temporarily adsorbing and storing the evaporative fuel guided through the evaporative fuel passage 14.
15, a canister 16 containing the activated carbon layer 15, a purge air introduction passage 17 for guiding vaporized fuel purge air from the intake passage 2 upstream of the throttle valve 4 to the activated carbon layer 15 in the canister 16, A purge passage 18 for guiding the discharged fuel to the intake passage 2 downstream of the throttle valve 4 and a purge control valve 19 for controlling the flow area of the purge passage 18 to control the purge amount of the fuel vapor are provided. These constitute an evaporative fuel processing system. In addition,
Evaporative fuel passage 14, canister 16, purge air introduction passage 1
7. The purge passage 18 constitutes an evaporative fuel supply means, and the purge control valve 19 and a control unit 20 which will be described later constitute an evaporative fuel supply amount control means.

【００２８】前記機関運転状態を検出する各種センサ類
の信号は、コントロールユニット (ＥＣＵ) 20に入力さ
れ、該コントロールユニット20は、これらの信号に応じ
て、前記補助空気量制御弁６、燃料噴射弁８、点火プラ
グ９、パージ制御弁19等のアクチュエータ類に駆動信号
を出力して、機関の各種制御を行う。次に前記システム
の作用を説明する。Signals from various sensors for detecting the engine operating state are input to a control unit (ECU) 20. The control unit 20 responds to these signals to control the auxiliary air amount control valve 6, the fuel injection A drive signal is output to actuators such as the valve 8, the ignition plug 9, the purge control valve 19, and the like to perform various controls of the engine. Next, the operation of the system will be described.

【００２９】燃焼室７内における混合気の空燃比がリー
ンになるに従い、吸気のポンピングロスの低減などによ
り、一般に同一出力トルクを得るために必要な燃料が減
少し、したがって、燃費は改善される。ここで、ガソリ
ン等の燃料を吸気ポート内に噴射して燃焼室内に均一な
空燃比の混合気を形成し、火花点火するタイプの通常の
火花点火式機関においては、ガソリンの場合空燃比が25
辺りが安定的に燃焼を行える限界となっている。これに
対し、本実施形態のように、燃焼室７内に燃料を直接噴
射して点火プラグ９周りにのみ混合気を形成し、その他
の領域には空気を配するような成層混合気を形成して燃
焼を行えば、点火プラグ９周りでは燃焼可能な混合気が
存在しながら、実質的に燃焼室７内の平均空燃比として
は、更にリーンな状態を実現でき、更なる燃費の向上が
図れる。As the air-fuel ratio of the air-fuel mixture in the combustion chamber 7 becomes leaner, the amount of fuel generally required to obtain the same output torque is reduced due to a reduction in pumping loss of intake air and the like, and therefore fuel efficiency is improved. . Here, in a normal spark ignition type engine in which fuel such as gasoline is injected into the intake port to form a mixture having a uniform air-fuel ratio in the combustion chamber and spark is ignited, the air-fuel ratio of gasoline is 25.
Around is the limit where stable combustion is possible. On the other hand, as in the present embodiment, a fuel-air mixture is formed directly around the spark plug 9 by directly injecting fuel into the combustion chamber 7, and a stratified air-fuel mixture in which air is disposed in other regions is formed. When the combustion is performed, the air-fuel ratio in the combustion chamber 7 can be substantially leaner while the combustible air-fuel mixture exists around the ignition plug 9, thereby further improving the fuel efficiency. I can do it.

【００３０】また、成層混合気状態で機関の運転を行う
場合、最大限に吸気を増加させても燃料量は相対的に少
ないため、発生トルクは小さくなる。したがって、成層
混合気燃焼は、通常比較的小さい負荷状態において用い
られ、負荷が大きい場合は混合気を燃焼室７内全体に満
たした状態での均質混合気での運転を行うようにする。When the engine is operated in a stratified mixture state, the generated torque is small because the fuel amount is relatively small even if the intake air is increased to the maximum. Therefore, the stratified mixture combustion is usually used under a relatively small load state, and when the load is large, the operation is performed with a homogeneous mixture in a state where the mixture is completely filled in the combustion chamber 7.

【００３１】一方、蒸発燃料の多くは機関の運転停止後
に発生するが、通常走行中も発生し、燃料温度の上昇に
伴い発生量は増加する。これらの蒸発燃料は、多くのシ
ステムではキャニスタ内の活性炭に吸着され、所定の運
転条件において、パージ制御弁を開いて吸着した蒸発燃
料を放出し、吸気系内から燃焼室に導いて処理してい
る。On the other hand, most of the evaporated fuel is generated after the operation of the engine is stopped, but is also generated during normal running, and the generated amount increases as the fuel temperature increases. In many systems, these fuel vapors are adsorbed on activated carbon in a canister, and under predetermined operating conditions, a purge control valve is opened to release the adsorbed fuel vapor, and the fuel vapor is guided from an intake system to a combustion chamber for processing. I have.

【００３２】この際一般的に、空燃比制御や排気成分に
悪影響が出ないように、蒸発燃料の吸気系への導入量
は、吸気量や燃料噴射量に応じ比例的に制御する。但
し、前述したように成層混合気を形成した場合には、燃
焼に関与しない空気層に蒸発燃料が混入すると、未燃焼
のＨＣ成分として燃焼室から排出されることとなるの
で、通常は、該成層混合気の形成中は、蒸発燃料の放出
を行わないようにする。At this time, the amount of evaporative fuel introduced into the intake system is generally controlled in proportion to the amount of intake air and the amount of fuel injection so that the air-fuel ratio control and the exhaust components are not adversely affected. However, when a stratified air-fuel mixture is formed as described above, if evaporative fuel enters an air layer that does not participate in combustion, it will be discharged from the combustion chamber as unburned HC components. During the formation of the stratified mixture, the fuel vapor is not released.

【００３３】しかし、成層混合気を形成するような運転
条件で機関が運転され続けた場合、蒸発燃料の放出を行
う機会が無くなってしまうという問題がある。このよう
な、蒸発燃料を十分に処理できないという問題を、本発
明の実施形態では、以下のような制御を行うことにより
対処したものである。以下に、本実施形態の制御を、図
３以降に示したフローチャートに従って説明する。However, when the engine is continuously operated under such operating conditions as forming a stratified air-fuel mixture, there is a problem that there is no opportunity to discharge the fuel vapor. In the embodiment of the present invention, such a problem that the evaporated fuel cannot be sufficiently processed is addressed by performing the following control. Hereinafter, the control of this embodiment will be described with reference to the flowcharts shown in FIG.

【００３４】図３は、全体の制御の流れを示すフローチ
ャートである。ステップ301 では、機関の運転条件に応
じて、成層混合気を形成するか、均質混合気を形成する
かを判断する。この判断の詳細は、後述する。ステップ
302 では、ステップ301 での判断に基づき、均質混合気
を形成する場合はステップ303 へ進み、成層混合気を形
成する場合はステップ304 へ進む。FIG. 3 is a flowchart showing the overall control flow. In step 301, it is determined whether to form a stratified mixture or a homogeneous mixture according to the operating conditions of the engine. The details of this determination will be described later. Steps
At 302, based on the determination at step 301, the process proceeds to step 303 when a homogeneous mixture is formed, and proceeds to step 304 when a stratified mixture is formed.

【００３５】ステップ303 では、均質混合気燃焼の場合
の制御を行う。これは、現在一般的に行われている制御
であるので、説明を省略する。ステップ304 では、現在
の運転状況に応じて、蒸発燃料のパージを行うか否かを
判断を行い、パージが不要の場合は本ルーチンを終了す
る。パージが必要な場合は、ステップ305 へ進み、ま
ず、窒素酸化物 (以下ＮＯｘという) の排出量を算出す
る。このＮＯｘ排出量の算出の詳細は、後述する。At step 303, control is performed in the case of homogeneous mixture combustion. This is a control that is generally performed at present, and a description thereof will be omitted. In step 304, it is determined whether or not the fuel vapor is to be purged according to the current operating condition. If the purge is unnecessary, the routine ends. If purging is required, the process proceeds to step 305, where the amount of emission of nitrogen oxides (hereinafter referred to as NOx) is calculated. Details of the calculation of the NOx emission amount will be described later.

【００３６】ステップ306 では、前記生成されたＮＯｘ
を還元するのに要する還元剤の要求量を算出する。この
算出の詳細は、後述する。ステップ307 では、前記還元
剤要求量に対し、実際にパージする還元剤としての蒸発
燃料の要求量を算出する。ステップ308 では、前記蒸発
燃料要求量に基づいて、前記パージ制御弁19の開度を制
御する。In step 306, the generated NOx
The required amount of the reducing agent required to reduce is calculated. Details of this calculation will be described later. In step 307, the required amount of the evaporated fuel as the reducing agent to be actually purged is calculated with respect to the required reducing agent amount. In step 308, the opening degree of the purge control valve 19 is controlled based on the required amount of fuel vapor.

【００３７】図４は、前記図３のステップ301 における
混合気形成の判断の一方法を示すフローチャートであ
る。この図４に示す機能が、混合気形成方法切換手段を
構成する。ステップ401 では、機関回転速度Ｎｅを読み
取り、ステップ402 では、機関の負荷、例えば基本燃料
噴射量等を読み取る。FIG. 4 is a flow chart showing one method of determining the formation of an air-fuel mixture in step 301 of FIG. The function shown in FIG. 4 constitutes the air-fuel mixture forming method switching means. In step 401, the engine speed Ne is read, and in step 402, the load of the engine, for example, the basic fuel injection amount, is read.

【００３８】ステップ403 では、機関回転速度Ｎｅと機
関負荷とにより、予めこれらをパラメータとして設定さ
れた成層／均質混合気形成領域判定マップから、成層混
合気を形成すべき領域か、均質混合気を形成すべき領域
かを判断する。具体的には、中・低回転速度かつ中・低
負荷負荷領域において、成層混合気を形成すべき領域と
し、それ以外の領域を均質混合気を形成すべき領域と判
断する。In step 403, a region where a stratified mixture is to be formed or a homogeneous mixture is determined from a stratified / homogeneous mixture formation region determination map which is set in advance by using the engine speed Ne and the engine load as parameters. It is determined whether the area should be formed. Specifically, it is determined that a stratified mixture is to be formed in the medium / low rotation speed and middle / low load load region, and that the other regions are regions in which a homogeneous mixture is to be formed.

【００３９】図５は、前記図３のステップ304 における
蒸発燃料のパージを行う必要があるか否かを判断する一
方法を示すフローチャートである。ステップ601 では、
蒸発燃料のキャニスタ16への蓄積量つまり蒸発燃料量を
算出する。この蒸発燃料量算出ルーチンを、図８のフロ
ーチャートに従って説明する。FIG. 5 is a flowchart showing one method of determining whether or not it is necessary to purge the fuel vapor in step 304 of FIG. In step 601,
The amount of evaporated fuel accumulated in the canister 16, that is, the amount of evaporated fuel is calculated. This evaporative fuel amount calculation routine will be described with reference to the flowchart of FIG.

【００４０】ステップ110 では、内燃機関の始動後この
処理を実行するのが、最初の１回目であるか否かを判断
する。最初の１回目であるは判断された場合は、ステッ
プ120 へ進んで、初回の場合として蒸発燃料量の初期量
をＱｅｖａｐに設定する。(Ｑｅｖａｐ＝Ｑｅｖａｐ
ｉｎｔ) 。この初期値は、例えば、前回機関停止時の燃
料温度あるいはその推定値の関数として与える。推定方
法の１つとしては、機関停止時の機関冷却水温と、始動
からの機関運転継続時間とにより、そのそれぞれが大き
いほど、多くの蒸発燃料が発生する関係で、量を規定す
る方法などがある。In step 110, it is determined whether or not this processing is executed for the first time after the internal combustion engine is started. If it is determined that this is the first time, the process proceeds to step 120, and the initial amount of the evaporated fuel amount is set to Qevap as the first time. (Qevap = Qevap
int). The initial value is given, for example, as a function of the fuel temperature at the time of the previous engine stop or its estimated value. As one of the estimation methods, there is a method of defining the amount based on the relationship between the engine cooling water temperature when the engine is stopped and the engine operation continuation time from the start, the larger the amount of each of them, the more evaporated fuel is generated. is there.

【００４１】ステップ130 では蒸発燃料放出のためのパ
ージ制御弁が開いているか否かを判断し，閉じている場
合はΔＱｅｖａｐが増加するのものとして、ステップ14
0 ではその増加量ΔＱｅｖａｐ (正値) を推定する。こ
の推定手法としては例えば、燃料温度あるいはその推定
値の関数として与える。ステップ150 では、逆にパージ
した結果の減少量ΔＱｅｖａｐ (負値) を推定する。こ
の推定手法としては例えば、ΔＱｅｖａｐを制御弁開度
と吸気負圧の関数として与える。In step 130, it is determined whether or not the purge control valve for discharging the evaporated fuel is open. If the purge control valve is closed, it is determined that ΔQevap increases, and step 14 is performed.
At 0, the increase amount ΔQevap (positive value) is estimated. This estimation method is given as a function of the fuel temperature or its estimated value, for example. In step 150, the amount of decrease ΔQevap (negative value) resulting from purging is estimated. As this estimation method, for example, ΔQevap is given as a function of the control valve opening and the intake negative pressure.

【００４２】ステップ160 では、Ｑｅｖａｐに対し、変
化量ΔＱｅｖａｐを加え、蒸発燃料量推定量とする (Ｑ
ｅｖａｐ←Ｑｅｖａｐ＋ΔＱｅｖａｐ) 。以上により蒸
発燃料量Ｑｅｖａｐつまり、キャニスタ内の蓄積蒸発燃
料量が推定される。図５に戻って、ステップ602 では、
前記蓄積量が所定の限界値に達しているか否かを判断
し、限界であればステップ603 へ進み、余裕があればス
テップ604 へ進む。In step 160, the change amount ΔQevap is added to Qevap to obtain an estimated fuel vapor amount (Q
evap ← Qevap + ΔQevap). From the above, the evaporated fuel amount Qevap, that is, the accumulated evaporated fuel amount in the canister is estimated. Returning to FIG. 5, in step 602,
It is determined whether or not the accumulated amount has reached a predetermined limit value. If it is the limit, the process proceeds to step 603, and if there is room, the process proceeds to step 604.

【００４３】ステップ603 では、設定空燃比をリッチに
補正しているか否かを判断し、リッチ補正中であればス
テップ604 へ進み、そうでない場合はステップ606 へ進
む。例えば、通常の設定空燃比で運転中に機関の安定度
が減少したときに、安定度を確保するため設定空燃比を
リッチ補正することがある。このように、リッチ補正し
ている場合、ＮＯｘの排出量は、所望の値より多くなる
が、このＮＯｘの排出量の増量を、成層混合気燃焼時の
蒸発燃料供給で還元処理するようにすれば、蒸発燃料の
処理量を増大できると共にＮＯｘ排出量を低減でき、し
かも、蒸発燃料の供給により、その分リッチ補正する燃
料噴射量を減少できるため燃費向上ともなる。そこで、
このような場合は、キャニスタ16への蒸発燃料の蓄積量
に余裕があるときでもステップ604 以降へ進み、可能な
限り蒸発燃料のパージを実行する。また、設定空燃比の
リッチ補正がされていない場合は、ＮＯｘを還元するの
に必要な量以上に蒸発燃料が供給されて、ＨＣ排出量が
増加する可能性があるので、ステップ606 へ進んで蒸発
燃料のパージを禁止する。In step 603, it is determined whether or not the set air-fuel ratio is richly corrected. If rich correction is being performed, the process proceeds to step 604; otherwise, the process proceeds to step 606. For example, when the stability of the engine decreases during operation at the normal set air-fuel ratio, the set air-fuel ratio may be richly corrected to ensure the stability. As described above, when the rich correction is performed, the emission amount of NOx becomes larger than a desired value. However, the increase in the emission amount of NOx is reduced by supplying the evaporated fuel during the combustion of the stratified mixture. For example, the processing amount of the evaporated fuel can be increased, the NOx emission amount can be reduced, and the fuel injection amount to be rich-corrected can be reduced by the supply of the evaporated fuel, so that the fuel efficiency can be improved. Therefore,
In such a case, even when the amount of fuel vapor accumulated in the canister 16 has a margin, the process proceeds to step 604 and thereafter, and purging of the fuel vapor is performed as much as possible. If the rich correction of the set air-fuel ratio has not been performed, there is a possibility that the amount of evaporative fuel is supplied to an amount greater than that required for reducing NOx and the amount of HC emission may increase. Prohibit purge of fuel vapor.

【００４４】ステップ604 では、排気浄化触媒21の活性
度を判断する。これは、触媒温度や、始動後の経過時間
等から判断する。そして、十分な浄化性能を有する程度
に活性化されていると判断された場合は、ステップ605
へ進んで蒸発燃料のパージを実行し、活性化されていな
いと判断された場合は、ステップ606 へ進んで蒸発燃料
のパージを禁止する。なお、このステップ604 の機能
が、触媒活性状態判断手段を構成する。In step 604, the activity of the exhaust purification catalyst 21 is determined. This is determined from the catalyst temperature, the elapsed time after starting, and the like. Then, when it is determined that the activation is performed to the extent that sufficient purification performance is obtained, step 605 is performed.
Proceeding to, purging of the evaporated fuel is executed, and if it is determined that the fuel is not activated, the process proceeds to step 606, and the purging of the evaporated fuel is prohibited. Incidentally, the function of this step 604 constitutes the catalyst activation state judging means.

【００４５】図６は、図３のステップ305 におけるＮＯ
ｘ排出量の算出の一方法を、明らかにするための図であ
る。このステップ305 の機能が、ＮＯｘ排出量算出手段
を構成する。これは、所定の機関回転速度Ｎｅと負荷と
で定まる運転状態の空燃比とＮＯｘ排出量の関係を示す
特性図である。このような情報を、前記コントロールユ
ニット20 (のＲＯＭ) に格納しておくことにより、運転
条件と混合気の空燃比とからＮＯｘ排出量を算出する。
また、この特性は、成層混合気による燃焼の際のデータ
であり、均質混合気燃焼時のデータとは異なる。また、
成層混合気燃焼では、ＮＯｘ排出量の特性は燃料噴射時
期によっても変化するため、図７に示すように燃料噴射
時期に応じた補正係数を設定し、該補正係数を用いた補
正を行う。FIG. 6 is a flowchart showing the operation of step 305 in FIG.
It is a figure for clarifying one method of calculation of x discharge. The function of step 305 constitutes NOx emission amount calculating means. This is a characteristic diagram showing a relationship between an air-fuel ratio and an NOx emission amount in an operating state determined by a predetermined engine speed Ne and a load. By storing such information in (the ROM of) the control unit 20, the NOx emission amount is calculated from the operating conditions and the air-fuel ratio of the air-fuel mixture.
This characteristic is data at the time of combustion with a stratified mixture, and is different from data at the time of homogeneous mixture combustion. Also,
In the stratified mixture combustion, the characteristics of the NOx emission amount also change depending on the fuel injection timing. Therefore, as shown in FIG. 7, a correction coefficient corresponding to the fuel injection timing is set, and correction is performed using the correction coefficient.

【００４６】次に、前記図３のステップ306 において、
算出されたＮＯｘ排出量に基づいて還元剤の要求量を算
出する際の基本的な考え方を説明する。このステップ30
6 の機能が、還元剤要求量算出手段を構成する。通常の
ガソリン燃料を使用する場合、ガソリンは空気に対し質
量比で14.7分の１の場合に、理論空燃比燃焼となって、
ガソリン中に含まれる水素や炭素と、大気中の酸素の量
が釣り合う。また、大気中の酸素質量は、約25％を占め
ており、ガソリン１ｇに対する酸素量は、約3.7 ｇとな
る。Next, in step 306 of FIG.
The basic concept of calculating the required amount of the reducing agent based on the calculated NOx emission amount will be described. This step 30
The function of No. 6 constitutes a reducing agent required amount calculating means. When using normal gasoline fuel, gasoline becomes stoichiometric air-fuel ratio combustion when the mass ratio to air is 1 / 4.7,
The amount of hydrogen and carbon in gasoline balances the amount of oxygen in the atmosphere. The mass of oxygen in the atmosphere accounts for about 25%, and the amount of oxygen per gram of gasoline is about 3.7 g.

【００４７】このことから、前述のＮＯｘ排出量に基づ
いて、その窒素と結合している酸素量を算出し、この酸
素量と釣り合うガソリン質量を、還元剤であるガソリン
(蒸発燃料) の要求量として算出する。次に、図３のス
テップ307 での実際の蒸発燃料のパージ量の算出につい
て、説明する。このステップ307 の機能が、蒸発燃料供
給量設定手段を構成する。Based on the above, the amount of oxygen combined with the nitrogen is calculated based on the above-mentioned NOx emission amount, and the mass of gasoline balanced with this amount of oxygen is determined by the gasoline as a reducing agent.
(Evaporated fuel). Next, the calculation of the actual amount of fuel vapor purge at step 307 in FIG. 3 will be described. The function of step 307 constitutes the evaporated fuel supply amount setting means.

【００４８】この算出の基本的な考え方は、ステップ30
6 で算出された還元剤の要求量に対し、実際に供給され
る還元剤量を少なめになるように算出する。これによ
り、少なくともＮＯｘの一部を還元できる効果を得られ
ると共に、ＮＯｘの排出量の推定に誤差があった場合で
も、蒸発燃料のＨＣ成分の排出を確実に防止することが
可能となる。この方法としては、ステップ306 での還元
剤要求量に対し一律に１より小の補正係数を乗じる方法
が簡易的である。The basic idea of this calculation is as follows:
The amount of reducing agent actually supplied is calculated to be smaller than the required amount of reducing agent calculated in 6. As a result, the effect of reducing at least a part of NOx can be obtained, and even if there is an error in estimating the NOx emission amount, it is possible to reliably prevent the HC component of the evaporated fuel from being emitted. As this method, a simple method is to uniformly multiply the required amount of reducing agent in step 306 by a correction coefficient smaller than 1.

【００４９】また、パージにより吸気に混入した蒸発燃
料のうち、燃焼室内において成層混合気の可燃混合気部
分に混入したものは、燃えてしまうので、その燃焼分を
考慮して、敢えて減少補正しなくてもよいといった考え
方もある。これらの考え方をどの程度活かして実際の蒸
発燃料のパージ量を決定するかは、パージ流量制御の制
御精度をも考慮して、システム毎に決めるべきである。Further, of the evaporative fuel mixed into the intake air by the purge, the fuel mixed into the combustible mixture of the stratified mixture in the combustion chamber burns. There is also an idea that it is not necessary. The extent to which these ideas are utilized to determine the actual purge amount of the evaporated fuel should be determined for each system in consideration of the control accuracy of the purge flow rate control.

【００５０】次に、図３のステップ308 でのパージ制御
弁19の制御について概略説明すると、パージ制御弁19の
開度を、前記ステップ307 で算出された蒸発燃料のパー
ジ量と、吸気負圧等と、に基づいて算出する。詳細は省
略するが、例えば、同一のパージ量を得る場合、機関運
転状態 (回転速度や負荷等) に基づいて推定された吸気
負圧が大きいときは、小さいときより開度を小さく制御
する。Next, the control of the purge control valve 19 in step 308 of FIG. 3 will be briefly described. The opening degree of the purge control valve 19 is determined by the amount of evaporative fuel purge calculated in step 307 and the intake negative pressure. And so on. Although details are omitted, for example, when the same purge amount is obtained, the opening is controlled to be smaller when the intake negative pressure estimated based on the engine operation state (rotational speed, load, etc.) is larger than when the intake negative pressure is smaller.

【００５１】また、前記空燃比センサ11として、空燃比
をリニアに検出できる広域型のものを使用すれば、パー
ジ制御弁19の開度を小量ずつ増大していって、その結果
変化した空燃比を空燃比センサによって検出することに
より、実際の蒸発燃料のパージ量を推定して、フィード
バック制御するような構成としてもよく、制御精度が向
上する。なお、この方式では、前記ＮＯｘ排出量の推定
も、実際に検出された空燃比に基づいて高精度に行うこ
とも可能である。If a wide-area air-fuel ratio sensor capable of linearly detecting the air-fuel ratio is used as the air-fuel ratio sensor 11, the opening degree of the purge control valve 19 is increased little by little. By detecting the fuel ratio with the air-fuel ratio sensor, the actual purge amount of the evaporated fuel may be estimated and the feedback control may be performed, thereby improving the control accuracy. In this method, the estimation of the NOx emission amount can be performed with high accuracy based on the actually detected air-fuel ratio.

【００５２】また、排気浄化触媒20において、還元剤と
してのＨＣは、ＮＯｘとのみ選択的に反応するわけでは
なく、排気中の酸素とも反応する。したがって、ＮＯｘ
を還元するために触媒に供給すべき還元剤の量は、前記
還元剤の必要量に対し、このＮＯｘと反応する還元剤の
比率分を増量して算出する。具体的には、空燃比40程度
の排気中に多くの酸素が含まれる場合には、必要量に対
し数倍から十数倍程度の還元剤を供給する必要があるの
で、これに応じて蒸発燃料のパージ量を制御する。In the exhaust purification catalyst 20, HC as a reducing agent does not react selectively with NOx but also reacts with oxygen in exhaust gas. Therefore, NOx
The amount of the reducing agent to be supplied to the catalyst to reduce NO is calculated by increasing the required amount of the reducing agent by the ratio of the reducing agent that reacts with NOx. More specifically, if the exhaust gas with an air-fuel ratio of about 40 contains a large amount of oxygen, it is necessary to supply a reducing agent several to several tens times the required amount. Control the amount of fuel purge.

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

【図１】本発明の構成・機能を示すブロック図。FIG. 1 is a block diagram showing the configuration and functions of the present invention.

【図２】本発明の一実施形態のシステム構成図。FIG. 2 is a system configuration diagram according to an embodiment of the present invention.

【図３】同上実施形態に係る制御のメインルーチンを示
すフローチャート。FIG. 3 is a flowchart showing a main routine of control according to the embodiment.

【図４】同じく、混合気形成方法切換のルーチンを示す
フローチャート。FIG. 4 is a flowchart showing a routine for switching the air-fuel mixture formation method.

【図５】同じく蒸発燃料のパージの要否を判断するルー
チンを示すフローチャート。FIG. 5 is a flowchart showing a routine for determining whether or not purge of evaporated fuel is necessary.

【図６】同じくＮＯｘ排出量の算出の一方法を明らかに
するための図。FIG. 6 is a diagram for clarifying one method of calculating the NOx emission amount.

【図７】同じくＮＯｘ排出量の算出に用いられる燃料噴
射時期に応じた補正係数を設定するための図。FIG. 7 is a diagram for setting a correction coefficient corresponding to a fuel injection timing used for calculating a NOx emission amount.

【図８】同じく蒸発燃料のキャニスタへの蓄積量を推定
するルーチンを示すフローチャート。FIG. 8 is a flowchart showing a routine for estimating the amount of accumulated fuel in the canister.

【符号の説明】[Explanation of symbols]

１ 内燃機関 ２ 吸気通路 ７ 燃焼室 ８ 燃料噴射弁 10 排気通路 13 燃料タンク 14 蒸発燃料通路 15 活性炭層 16 キャニスタ 17 パージエア導入通路 18 パージ通路 19 パージ制御弁 20 コントロールユニット 21 排気浄化用触媒 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake passage 7 Combustion chamber 8 Fuel injection valve 10 Exhaust passage 13 Fuel tank 14 Evaporation fuel passage 15 Activated carbon layer 16 Canister 17 Purge air introduction passage 18 Purge passage 19 Purge control valve 20 Control unit 21 Exhaust purification catalyst

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｆ０２Ｄ 41/02 ３０１ Ｆ０２Ｄ 41/02 ３０１Ｆ ３０１Ｊ 41/04 ３３５ 41/04 ３３５Ｃ 43/00 ３０１ 43/00 ３０１Ｅ ３０１Ｔ ３０１Ｊ ──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. 6 Identification number Office reference number FI Technical display location F02D 41/02 301 F02D 41/02 301F 301J 41/04 335 41/04 335C 43/00 301 43 / 00 301E 301T 301J

Claims (10)

【特許請求の範囲】[Claims] 【請求項１】少なくとも所定の条件で、燃焼室内に混合
気層と空気層との成層化状態を形成して燃焼を行う成層
混合気燃焼を行う一方、燃料系からの蒸発燃料を所定の
条件で吸気系に供給するようにし、かつ、排気系に排気
浄化用の触媒を備えた内燃機関の吸気制御装置におい
て、 前記成層混合気燃焼時に、燃焼室から排出される窒素酸
化物の排出量に応じた量の蒸発燃料を吸気系に供給し、
蒸発燃料の炭化水素成分を成層混合気の空気層に混入さ
せて未燃焼のまま排気系に排出させ、前記触媒にて窒素
酸化物の還元に供するようにしたことを特徴とする内燃
機関の吸気制御装置。At least under a predetermined condition, stratified mixture combustion is performed in which a stratified state of an air-fuel mixture layer and an air layer is formed in a combustion chamber and combustion is performed. In the intake control apparatus for an internal combustion engine, which is provided with an exhaust gas purification catalyst in the exhaust system, the amount of nitrogen oxides discharged from the combustion chamber during the combustion of the stratified mixture is determined. Supply the appropriate amount of fuel vapor to the intake system,
A hydrocarbon component of the evaporated fuel is mixed into an air layer of a stratified mixture, discharged to an exhaust system without being burned, and used for reduction of nitrogen oxides by the catalyst. Control device. 【請求項２】燃焼室内に混合気層と空気層との成層化状
態を形成して燃焼を行う成層混合気燃焼と、燃焼室内に
均質な混合気を形成して燃焼を行う均質混合気燃焼と、
を、機関の運転条件に応じて切り換えて行う混合気形成
切換手段と、 燃料供給系から蒸発した燃料を、機関の吸気系に供給す
る蒸発燃料供給手段と、 前記蒸発燃料の吸気系への供給量を制御する蒸発燃料供
給量制御手段と、 燃焼室から排出される窒素酸化物の量を算出する窒素酸
化物排出量算出手段と、 前記窒素酸化物排出量算出手段により算出された窒素酸
化物排出量に対し、機関の排気系に介装された排気浄化
用の触媒で窒素酸化物の還元を行うのに必要な炭化水素
量を算出する還元剤要求量算出手段と、 成層混合気燃焼時に、前記還元剤要求量に応じた量の蒸
発燃料を吸気系に供給するように供給量を設定する蒸発
燃料供給量設定手段と、 を含んで構成され、 前記成層混合気燃焼時に吸気系に供給された蒸発燃料の
炭化水素成分を成層混合気の空気層に混入させて未燃焼
のまま排気系に排出させ、窒素酸化物の還元に供するよ
うにしたことを特徴とする内燃機関の吸気制御装置。2. A stratified mixture combustion in which a stratified state of an air-fuel layer and an air layer is formed in a combustion chamber to perform combustion, and a homogeneous mixture combustion in which a homogeneous mixture is formed in the combustion chamber to perform combustion. When,
And an air-fuel mixture switching unit that switches the mixture according to operating conditions of the engine, an evaporative fuel supply unit that supplies fuel evaporated from a fuel supply system to an intake system of the engine, and a supply of the evaporative fuel to an intake system. Evaporative fuel supply amount controlling means for controlling the amount; nitrogen oxide emission calculating means for calculating the amount of nitrogen oxide discharged from the combustion chamber; and nitrogen oxide calculated by the nitrogen oxide emission calculating means. A reducing agent required amount calculating means for calculating an amount of hydrocarbons necessary for reducing nitrogen oxides with an exhaust purification catalyst interposed in an exhaust system of the engine with respect to the emission amount; Evaporative fuel supply amount setting means for setting a supply amount so as to supply an amount of evaporative fuel corresponding to the required amount of the reducing agent to the intake system, and supplying the evaporative fuel to the intake system during the stratified mixture combustion. Hydrocarbon component of the evaporated fuel An intake control device for an internal combustion engine, wherein the intake control device is mixed with an air layer of a stratified mixture and discharged to an exhaust system without being burned, thereby reducing nitrogen oxides. 【請求項３】前記窒素酸化物排出量算出手段は、機関の
運転状態、混合気の空燃比及び燃料噴射時期に基づいて
窒素酸化物の排出量を算出することを特徴とする請求項
２に記載の内燃機関の吸気制御装置。3. The apparatus according to claim 2, wherein said nitrogen oxide emission calculating means calculates the nitrogen oxide emission based on an operating state of the engine, an air-fuel ratio of an air-fuel mixture, and a fuel injection timing. An intake control device for an internal combustion engine according to any one of the preceding claims. 【請求項４】前記蒸発燃料供給手段は、燃料系から蒸発
した燃料を一時的に蓄積する蒸発燃料蓄積部を備え、 前記蒸発燃料蓄積部における蒸発燃料の蓄積量を算出す
る蒸発燃料蓄積量算出手段を含んで構成され、 前記成層混合気燃焼時の蒸発燃料の供給は、前記蒸発燃
料の蓄積量が限界値付近となったときに、行うようにし
たことを特徴とする請求項２又は請求項３に記載の内燃
機関の吸気制御装置。4. An evaporative fuel supply means comprising: an evaporative fuel accumulator for temporarily accumulating fuel evaporated from a fuel system; and an evaporative fuel accumulator calculating means for calculating an amount of evaporative fuel accumulated in the evaporative fuel accumulator. And supplying the evaporated fuel during the combustion of the stratified mixture when the accumulated amount of the evaporated fuel is near a limit value. Item 4. An intake control device for an internal combustion engine according to item 3. 【請求項５】前記成層混合気燃焼時の蒸発燃料の供給
は、前記窒素酸化物排出量算出手段によって算出される
窒素酸化物排出量が所定以上のときに、行うようにした
ことを特徴とする請求項２〜請求項４のいずれか１つに
記載の内燃機関の吸気制御装置。5. The method according to claim 1, wherein the supply of the evaporated fuel during the combustion of the stratified mixture is performed when the nitrogen oxide emission calculated by the nitrogen oxide emission calculation means is equal to or greater than a predetermined value. An intake control device for an internal combustion engine according to any one of claims 2 to 4. 【請求項６】前記成層混合気燃焼時の蒸発燃料の供給
は、燃焼安定度の悪化に起因して混合気の設定空燃比を
リッチ補正しているときに、行うようにしたことを特徴
とする請求項２〜請求項５のいずれか１つに記載の内燃
機関の吸気制御装置。6. The fuel supply system according to claim 1, wherein the supply of the evaporated fuel during the combustion of the stratified mixture is performed when the set air-fuel ratio of the mixture is richly corrected due to the deterioration of the combustion stability. An intake control device for an internal combustion engine according to any one of claims 2 to 5. 【請求項７】前記排気浄化用触媒の活性状態を判断する
触媒活性状態判断手段を含んで構成され、 前記成層混合気燃焼時の蒸発燃料の供給は、窒素酸化物
の還元が進行するには触媒活性が十分でないと判断され
たときは、禁止するようにしたことを特徴とする請求項
２〜請求項６のいずれか１つに記載の内燃機関の吸気制
御装置。7. A system according to claim 1, further comprising a catalyst activation state determining means for determining an activation state of said exhaust gas purifying catalyst, wherein the supply of the evaporated fuel during the combustion of the stratified mixture is such that the reduction of nitrogen oxides proceeds. The intake control device for an internal combustion engine according to any one of claims 2 to 6, wherein when it is determined that the catalyst activity is not sufficient, the control is prohibited. 【請求項８】前記蒸発燃料供給量設定手段は、前記還元
剤要求量算出手段により算出された還元剤要求量に対し
て、蒸発燃料の供給量を少なめとなるように設定するこ
とを特徴とする請求項１〜請求項７のいずれか１つに記
載の内燃機関の吸気制御装置。8. The fuel vapor supply amount setting means sets the amount of evaporative fuel to be smaller than the required amount of reducing agent calculated by the required amount of reducing agent calculating means. The intake control device for an internal combustion engine according to any one of claims 1 to 7. 【請求項９】前記蒸発燃料供給量設定手段は、空燃比の
リーン度合いの大きい成層混合気燃焼時に、蒸発燃料中
の炭化水素のうち、排気中の酸素と反応せず、窒素酸化
物と還元反応を行うものの割合に基づいて、蒸発燃料の
供給量を設定することを特徴とする請求項１〜請求項８
のいずれか１つに記載の内燃機関の吸気制御装置。9. The fuel vapor supply amount setting means does not react with the oxygen in the exhaust gas of the hydrocarbons in the vaporized fuel during the combustion of a stratified mixture with a large lean air-fuel ratio, and reduces the nitrogen oxides and the nitrogen oxides. 9. The supply amount of the evaporated fuel is set based on the ratio of the one that performs the reaction.
An intake control device for an internal combustion engine according to any one of the above. 【請求項10】前記窒素酸化物排出量算出手段は、機関の
運転状態と、混合気の空燃比とに基づいて窒素酸化物の
基本排出量を求め、該基本排出量を燃料噴射時期で補正
して算出することを特徴とする請求項２〜請求項９のい
ずれか１つに記載の内燃機関の吸気制御装置。10. The nitrogen oxide emission amount calculating means obtains a basic emission amount of nitrogen oxides based on an operating state of an engine and an air-fuel ratio of an air-fuel mixture, and corrects the basic emission amount with a fuel injection timing. The intake control device for an internal combustion engine according to any one of claims 2 to 9, wherein the calculation is performed by the following.
JP21485396A 1996-07-31 1996-08-14 Intake control device for internal combustion engine Expired - Lifetime JP3509404B2 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP21485396A JP3509404B2 (en) 1996-08-14 1996-08-14 Intake control device for internal combustion engine
KR1019970036413A KR100209176B1 (en) 1996-07-31 1997-07-31 Engine combustion controller
US08/903,952 US6012435A (en) 1996-07-31 1997-07-31 Engine combustion controller

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP21485396A JP3509404B2 (en) 1996-08-14 1996-08-14 Intake control device for internal combustion engine

Publications (2)

Publication Number Publication Date
JPH1054310A true JPH1054310A (en) 1998-02-24
JP3509404B2 JP3509404B2 (en) 2004-03-22

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0889221A3 (en) * 1997-07-04 2000-06-28 Nissan Motor Company, Limited Control system for internal combustion engine
EP1074706A2 (en) * 1999-08-02 2001-02-07 Ford Global Technologies, Inc. Temperature control method for a direct injection engine
EP1087118A2 (en) * 1999-08-02 2001-03-28 Ford Global Technologies, Inc. Heat generation method in an emission control device
EP1074726A3 (en) * 1999-08-02 2005-04-06 Ford Global Technologies, Inc. Engine control with a fuel vapour purge system
EP1074728A3 (en) * 1999-08-02 2005-05-25 Ford Global Technologies, Inc. Direct injection engine control with a fuel vapor purge system

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0889221A3 (en) * 1997-07-04 2000-06-28 Nissan Motor Company, Limited Control system for internal combustion engine
EP1074706A2 (en) * 1999-08-02 2001-02-07 Ford Global Technologies, Inc. Temperature control method for a direct injection engine
EP1087118A2 (en) * 1999-08-02 2001-03-28 Ford Global Technologies, Inc. Heat generation method in an emission control device
EP1087118A3 (en) * 1999-08-02 2001-05-02 Ford Global Technologies, Inc. Heat generation method in an emission control device
EP1074706A3 (en) * 1999-08-02 2002-06-19 Ford Global Technologies, Inc. Temperature control method for a direct injection engine
EP1074726A3 (en) * 1999-08-02 2005-04-06 Ford Global Technologies, Inc. Engine control with a fuel vapour purge system
EP1074728A3 (en) * 1999-08-02 2005-05-25 Ford Global Technologies, Inc. Direct injection engine control with a fuel vapor purge system

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