JP3596378B2 - Exhaust gas heating device for internal combustion engine - Google Patents

Exhaust gas heating device for internal combustion engine Download PDF

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Publication number
JP3596378B2
JP3596378B2 JP29216899A JP29216899A JP3596378B2 JP 3596378 B2 JP3596378 B2 JP 3596378B2 JP 29216899 A JP29216899 A JP 29216899A JP 29216899 A JP29216899 A JP 29216899A JP 3596378 B2 JP3596378 B2 JP 3596378B2
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Prior art keywords
exhaust
internal combustion
combustion engine
exhaust gas
fuel
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JP29216899A
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Japanese (ja)
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JP2001115883A (en
Inventor
伸基 大橋
信也 広田
孝充 浅沼
俊祐 利岡
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Toyota Motor Corp
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Toyota Motor Corp
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Priority to JP29216899A priority Critical patent/JP3596378B2/en
Priority to DE10045548A priority patent/DE10045548B4/en
Priority to FR0013020A priority patent/FR2799794B1/en
Publication of JP2001115883A publication Critical patent/JP2001115883A/en
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    • 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
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
    • 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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
    • F01N3/0222—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
    • 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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • 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
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • 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
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2825—Ceramics
    • F01N3/2828—Ceramic multi-channel monoliths, e.g. honeycombs
    • 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
    • F02D41/024—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus
    • F02D41/0245—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus by increasing temperature of the exhaust gas leaving the engine
    • 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
    • F02D41/029—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 particulate filter
    • 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
    • F02D41/401—Controlling injection timing
    • 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
    • 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
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/06—Ceramic, e.g. monoliths
    • 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)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Toxicology (AREA)
  • Health & Medical Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Control Of Throttle Valves Provided In The Intake System Or In The Exhaust System (AREA)
  • Processes For Solid Components From Exhaust (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、自動車等に搭載される内燃機関から排出される排気の温度を昇温させる技術に関し、特に排気のエミッションを悪化させることなく排気温度を昇温させる技術に関する。
【０００２】
【従来の技術】
自動車等に搭載される内燃機関では、該内燃機関から排出される排気に含まれる有害ガス成分を浄化した上で大気中に放出することが要求されている。このような要求に対し、従来では、内燃機関の排気通路に排気浄化触媒を配置し、排気中に含まれる有害ガス成分を排気浄化触媒にて浄化する技術が提案されている。
【０００３】
ところで、排気浄化触媒は、一般に所定温度以上のときに活性して排気中の有害ガス成分を浄化することが可能となるため、内燃機関が冷間始動されたときのように排気浄化触媒の温度が所定温度未満であるときは排気中の有害ガス成分を十分に浄化することが不可能となる。
【０００４】
このような問題点に対し、従来では、特開平１０−２１２９９５号公報に記載されたような排気昇温装置が提案されている。この公報に記載された排気昇温装置は、内燃機関が冷間始動後の暖機運転状態にある場合等に、内燃機関の燃焼に供される通常の燃料噴射（主燃料噴射）に加え、各気筒の膨張行程時に副次的な燃料噴射（副燃料噴射）を行うことにより、副噴射された燃料を燃焼させて、排気弁開弁時における筒内ガス温度、言い換えれば排気温度を高め、以て排気浄化触媒の早期活性化を図ろうとするものである。
【０００５】
【発明が解決しようとする課題】
ところで、内燃機関が冷間始動後の暖機運転状態にある場合等は、筒内の温度が低く主燃料が完全燃焼し難いため、既燃ガス中に比較的多量の未燃燃料成分が残存することになる。このように未燃燃料成分の残存量が多い状況下で副燃料噴射が実行されると、副燃料を着火源として未燃燃料成分が燃焼するが、筒内の雰囲気温度が低いために副燃料と未燃燃料成分とが完全に燃焼しきれず、煤や未燃燃料成分に代表される粒子状物質（ＰＭ：Ｐａｒｔｉｃｕｌａｔｅ Ｍａｔｔｅｒ）が多量に発生する場合がある。
【０００６】
本発明は、上記したような問題点に鑑みてなされたものであり、排気エミッションを悪化させることなく、排気の温度を効率的に上昇させる技術を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明は、上記課題を解決するために以下のような手段を採用した。すなわち、本発明に係る内燃機関の排気昇温装置は、内燃機関の排気通路に設けられて該排気通路を流れる排気の流量を調節する排気絞り弁と、前記内燃機関の気筒内に直接燃料を噴射する燃料噴射弁と、前記内燃機関から排出される未燃燃料成分を低減すべきときに前記排気絞り弁をほぼ全閉に制御する弁制御手段と、前記排気絞り弁がほぼ全閉に制御されたときに前記燃料噴射弁から噴射される主たる燃料量を増加させる主燃料噴射制御手段と、前記主燃料噴射制御手段による主燃料の噴射後に前記燃料噴射弁から副次的に燃料を噴射させる副燃料噴射制御手段と、前記排気通路に設けられて該排気通路を流れる排気に含まれる粒子状物質を除去するＰＭ除去手段と、を備え、前記副燃料噴射制御手段は、前記内燃機関から排出される未燃燃料成分の量が最も少なくなる時期に副燃料の噴射を実行するとともに、前記ＰＭ除去手段によって粒子状物質を除去することを特徴とする。
【０００８】
このように構成された排気昇温装置では、弁制御手段は、内燃機関から排出される未燃燃料成分量を低減すべき時期に、排気絞り弁の開度をほぼ全閉状態とする。これに応じて、主燃料噴射制御手段が主燃料の噴射量を増加させるべく燃料噴射弁を制御するとともに、副燃料噴射制御手段が主燃料の噴射後に副燃料を噴射させるべく燃料噴射弁を制御する。
【０００９】
この場合、ほぼ全閉状態となった排気絞り弁と主燃料の噴射量増加との相乗効果により、排気絞り弁上流の排気通路から内燃機関の気筒内にかけて排気の圧力及び温度が上昇するとともに排気の流速が低下するため、主燃料の燃え残りである未燃燃料成分と副燃料が高温下で長期にわたって燃焼し、未燃燃料成分の残存量が減少する。更に、排気中に含まれる煤などの粒子状物質は、排気通路に配置されたＰＭ除去手段によって排気中から除去され、大気中に放出されることがない。
【００１０】
ここで、内燃機関から排出される未燃燃料成分量を低減すべき時期としては、内燃機関が冷間始動後の暖機運転状態にあるとき、外気温度が低い状況下で内燃機関が低負荷運転状態にあるとき、等を例示することができる。
【００１１】
本発明に係る内燃機関の排気昇温装置では、副燃料噴射制御手段は、内燃機関から排出される未燃燃料成分の量が最も少なくなる時期に副燃料の噴射を実行するようにすることが好ましい。
【００１２】
本発明に係る内燃機関の排気昇温装置では、ＰＭ除去手段として、排気中に含まれる粒子状物質を物理的に吸着するＰＭトラップを例示することが出来る。
この場合、ＰＭトラップの吸着能力が飽和する前にＰＭトラップを再生する必要が生じるが、そのような場合は、弁制御手段が排気絞り弁をほぼ全閉に制御し、主燃料噴射制御手段が主燃料の噴射量を増加すべく燃料噴射弁を制御し、副燃料噴射制御手段が副燃料の噴射を実行すべく燃料噴射弁を制御することにより、ＰＭトラップを通過する排気の温度を高めるようにすればよい。
【００１３】
本発明に係る内燃機関の排気昇温装置では、ＰＭ除去手段は、排気絞り弁より上流の排気通路に配置されることが好ましい。
これは、排気絞り弁がほぼ全閉状態となったときに、排気絞り弁上流の排気通路では排気絞り弁下流の排気通路に比して排気の流速が低く、高温状態の排気が滞留するため、ＰＭ除去手段が高温の排気に長期間曝されて粒子状物質の再生効率が向上するからである。
【００１４】
【発明の実施の形態】
以下、本発明に係る内燃機関の排気昇温装置の具体的な実施態様について図面に基づいて説明する。
【００１５】
図１は、本発明に係る排気昇温装置を適用する内燃機関の概略構成を示す図である。図１に示す内燃機関１は、複数の気筒２１を備えるとともに、各気筒２１内に直接燃料を噴射する燃料噴射弁３２を具備した４サイクルの筒内噴射式内燃機関である。
【００１６】
前記内燃機関１は、複数の気筒２１及び冷却水路１ｃが形成されたシリンダブロック１ｂと、このシリンダブロック１ｂの上部に固定されたシリンダヘッド１ａとを備えている。
【００１７】
前記シリンダブロック１ｂには、機関出力軸であるクランクシャフト２３が回転自在に支持され、このクランクシャフト２３は、各気筒２１内に摺動自在に装填されたピストン２２と連結されている。
【００１８】
前記ピストン２２の上方には、ピストン２２の頂面とシリンダヘッド１ａの壁面とに囲まれた燃焼室２４が形成されている。前記シリンダヘッド１ａには、燃焼室２４に臨むよう点火栓２５が取り付けられ、この点火栓２５には、該点火栓２５に駆動電流を印加するためのイグナイタ２５ａが接続されている。
【００１９】
前記シリンダヘッド１ａには、２つの吸気ポート２６の開口端と２つの排気ポート２７の開口端とが燃焼室２４に臨むよう形成されるとともに、その噴孔が燃焼室２４に臨むよう燃料噴射弁３２が取り付けられている。
【００２０】
前記吸気ポート２６の各開口端は、シリンダヘッド１ａに進退自在に支持された吸気弁２８によって開閉されるようになっており、これら吸気弁２８は、シリンダヘッド１ａに回転自在に支持されたインテーク側カムシャフト３０によって進退駆動されるようになっている。
【００２１】
前記排気ポート２７の各開口端は、シリンダヘッド１ａに進退自在に支持された排気弁２９により開閉されるようになっており、これら排気弁２９は、シリンダヘッド１ａに回転自在に支持されたエキゾースト側カムシャフト３１により進退駆動されるようになっている。
【００２２】
前記インテーク側カムシャフト３０及び前記エキゾースト側カムシャフト３１は、図示しないタイミングベルトを介してクランクシャフト２３と連結され、クランクシャフト２３の回転トルクがタイミングベルトを介してインテーク側カムシャフト３０及びエキゾースト側カムシャフト３１へ伝達されるようになっている。
【００２３】
各気筒２１に連通する２つの吸気ポート２６のうちの一方の吸気ポート２６は、シリンダヘッド１ａ外壁に形成された開口端から燃焼室２４に臨む開口端へ向かって直線状に形成された流路を有するストレートポートで構成され、他方の吸気ポート２６は、シリンダヘッド１ａ外壁の開口端から燃焼室２４の開口端へ向かって、気筒２１の軸方向と垂直な面において旋回するよう形成された流路を有するヘリカルポートで構成されている。
【００２４】
前記各吸気ポート２６は、シリンダヘッド１ａに取り付けられた吸気枝管３３の各枝管と連通している。各気筒２１に対応した２つの吸気ポート２６のうちのストレートポートと連通する枝管には、その枝管内の流量を調節するスワールコントロールバルブ３７が設けられている。前記スワールコントロールバルブ３７には、ステッパモータ等からなり、印加電流の大きさに応じてスワールコントロールバルブ３７を開閉駆動するアクチュエータ３７ａと、スワールコントロールバルブ３７の開度に対応した電気信号を出力するＳＣＶポジションセンサ３７ｂとが取り付けられている。
【００２５】
前記吸気枝管３３は、サージタンク３４に接続され、このサージタンク３４は、吸気管３５を介してエアクリーナボックス３６と接続されている。前記吸気管３５には、該吸気管３５内を流れる新気の流量を調節するスロットル弁３９が設けられている。
【００２６】
前記スロットル弁３９には、ステッパモータ等からなり、印加電流の大きさに応じて該スロットル弁３９を開閉駆動するアクチュエータ４０と、該スロットル弁３９の開度に対応した電気信号を出力するスロットルポジションセンサ４１とが取り付けられている。
【００２７】
さらに、前記スロットル弁３９には、アクセルペダル４２に連動して回転するアクセルレバー（図示せず）が併設され、このアクセルレバーには、アクセルレバーの回転位置（アクセルペダル４２の踏み込み量）に対応した電気信号を出力するアクセルポジションセンサ４３が取り付けられている。
【００２８】
前記スロットル弁３９より上流の吸気管３５には、吸気管３５内を流れる新気の質量（吸入空気質量）に対応した電気信号を出力するエアフローメータ４４が取り付けられる。
【００２９】
一方、前記内燃機関１の各排気ポート２７は、前記シリンダヘッド１ａに取り付けられた排気枝管４５の各枝管と連通している。前記排気枝管４５は、排気浄化触媒４６を介して排気管４７に接続され、排気管４７は、下流にて図示しないマフラーと接続されている。
【００３０】
前記排気浄化触媒４６は、本発明に係るＰＭ除去手段を実現するものであり、例えば、図２、図３に示すように、上流側の端部が開放され且つ下流側の端部が閉塞された第１流路４６ａと上流側の端部が閉塞され且つ下流側の端部が開放された第２流路４６ｂとをハニカム状をなすよう配置してなる多孔質の担体と、前記担体の表面に形成された触媒層とからなるウォールスロー型の排気浄化触媒である。
【００３１】
前記した担体としては、多孔質のセラミックやゼオライト等を例示することができ、前記した触媒層としては、多孔質のアルミナ（Ａｌ２Ｏ３）の表面に白金−ロジウム（Ｐｔ−Ｒｈ）系あるいはパラジウム−ロジウム（Ｐｄ−Ｒｈ）系の貴金属触媒物質が担持されたもの、または、カリウム（Ｋ）、ナトリウム（Ｎａ）、リチウム（Ｌｉ）もしくはセシウム（Ｃｓ）等のアルカリ金属と、バリウム（Ｂａ）やカルシウム（Ｃａ）等のアルカリ土類と、ランタン（Ｌａ）やイットリウム（Ｙ）等の希土類とから選択された少なくとも１つと、白金（Ｐｔ）等の貴金属類とからなるもの等を例示することができる。
【００３２】
このように構成された排気浄化触媒４６では、該排気浄化触媒４６に流入した排気は、先ず第１流路４６ａに導かれ、次いで担体の壁面の細孔を通って第２流路４６ｂへ流れ、第２流路４６ｂから下流の排気管４７へ排出される。排気が担体の壁面を通過する際に、排気中に含まれる煤や未燃燃料成分などの粒子状物質が捕集されるとともに、排気中に含まれる有害ガス成分が触媒層にて浄化される。従って、排気浄化触媒４６は、排気中の粒子状物質を捕集するフィルタの機能と、排気中の有害ガス成分を浄化する触媒機能とを兼ね備えていることになる。
【００３３】
ここで図１に戻り、前記排気枝管４５には、該排気枝管４５内を流れる排気に含まれる酸素の濃度に対応した電気信号を出力する酸素センサ（Ｏ２センサ）４８が取り付けられている。
【００３４】
前記排気管４７の途中には、該排気管４７内を流れる排気の流量を調節する排気絞り弁４９が設けられている。前記排気絞り弁４９には、ステッパモータ等からなり、印加電流の大きさに応じて該排気絞り弁４９を開閉駆動するアクチュエータ５０が取り付けられている。
【００３５】
また、内燃機関１は、クランクシャフト２３の端部に取り付けられたタイミングロータ５１ａとタイミングロータ５１ａ近傍のシリンダブロック１ｂに取り付けられた電磁ピックアップ５１ｂとからなるクランクポジションセンサ５１と、内燃機関１の内部に形成された冷却水路１ｃを流れる冷却水の温度を検出すべくシリンダブロック１ｂに取り付けられた水温センサ５２とを備えている。
【００３６】
このように構成された内燃機関１には、該内燃機関１の運転状態を制御するための電子制御ユニット（Ｅｌｅｃｔｒｏｎｉｃ Ｃｏｎｔｒｏｌ Ｕｎｉｔ：ＥＣＵ、以下ＥＣＵと称する）２０が併設されている。
【００３７】
前記ＥＣＵ２０には、ＳＣＶポジションセンサ３７ｂ、スロットルポジションセンサ４１、アクセルポジションセンサ４３、エアフローメータ４４、酸素センサ４８、クランクポジションセンサ５１、及び水温センサ５２等の各種センサが電気配線を介して接続され、各センサの出力信号が前記ＥＣＵ２０に入力されるようになっている。
【００３８】
前記ＥＣＵ２０には、イグナイタ２５ａ、燃料噴射弁３２、アクチュエータ３７ａ、アクチュエータ４０、アクチュエータ５０等が電気配線を介して接続され、前記ＥＣＵ２０は、前記した各種センサの出力信号値をパラメータとして、イグナイタ２５ａ、燃料噴射弁３２、アクチュエータ３７ａ、アクチュエータ４０、アクチュエータ５０を制御することが可能になっている。
【００３９】
例えば、ＥＣＵ２０は、クランクポジションセンサ５１、アクセルポジションセンサ４３、あるいはエアフローメータ４４等の出力信号値をパラメータとして内燃機関１の運転状態を判別する。前記内燃機関１の運転状態が低負荷運転領域にあると判定された場合は、ＥＣＵ２０は、内燃機関１の成層燃焼を実現すべく、アクチュエータ３７ａへ制御信号を送信してスワールコントロールバルブ３７の開度を小さくし、アクチュエータ４０へ制御信号を送信してスロットル弁３９を実質的に全開状態とし、さらに各気筒２１の圧縮行程時に燃料噴射弁３２に駆動電流を印加して圧縮行程噴射を行う。
【００４０】
この場合、各気筒２１の燃焼室２４には、吸気行程時に主としてスワールポート７ｂからの新気が導入され、強い旋回流（スワール流）が発生する。続く圧縮行程では、燃料噴射弁３２から噴射された燃料がスワール流に従って燃焼室２４内を旋回し、所定の時期に点火栓２５近傍へ移動する。このとき、燃焼室２４内は、点火栓２５の近傍が可燃混合気層となり、且つその他の領域が空気層となる、いわゆる成層状態となる。そして、ＥＣＵ２０は、上記した所定の時期に、イグナイタ２５ａを駆動して点火栓２５を点火する。この結果、燃焼室２４内の混合気（可燃混合気層と空気層とを含む）は、点火栓２５近傍の可燃混合気層を着火源として燃焼する。
【００４１】
尚、成層燃焼運転時における燃料噴射量は、アクセル開度と機関回転数とをパラメータとして決定される。すなわち、ＥＣＵ２０は、アクセルポジションセンサ４３の出力信号値（アクセル開度）と機関回転数と燃料噴射量との関係を示す成層燃焼時燃料噴射制御マップを用いて燃料噴射量（燃料噴射時間）を決定する。
【００４２】
また、ＥＣＵ２０は、内燃機関１の運転状態が中負荷運転領域にあると判定した場合は、リーン混合気による均質リーン燃焼を実現すべく、アクチュエータ３７ａへ制御信号を送信してスワールコントロールバルブ３７の開度を小さくし、さらに各気筒２１の吸気行程時に燃料噴射弁３２に駆動電流を印加して吸気行程噴射を行う。この場合、各気筒２１の燃焼室２４内の略全域にわたって、新気と燃料とが均質に混じり合ったリーン混合気が形成され、均質リーン燃焼が実現される。
【００４３】
また、ＥＣＵ２０は、内燃機関１の運転状態が高負荷運転領域にあると判定した場合は、理論空燃比近傍の混合気による均質燃焼を実現すべく、アクチュエータ３７ａへ制御信号を送信してスワールコントロールバルブ３７を全開状態とし、スロットル弁３９がアクセルペダル４２の踏み込み量（アクセルポジションセンサ４３の出力信号値）に対応した開度となるようアクチュエータ４０へ制御信号を送信し、さらに各気筒２１の吸気行程時に燃料噴射弁３２に駆動電流を印加して吸気行程噴射を行う。この場合、各気筒２１の燃焼室２４内の略全域にわたって、新気と燃料とが均質に混じり合った理論空燃比の混合気が形成され、均質燃焼が実現される。
【００４４】
尚、ＥＣＵ２０は、成層燃焼制御から均質燃焼制御へ移行する際、あるいは均質燃焼制御から成層燃焼制御へ移行する際に、内燃機関１のトルク変動を防止すべく各気筒２１の圧縮行程時と吸気行程時との二回に分けて燃料噴射弁３２に駆動電流を印加する。この場合、各気筒２１の燃焼室２４内には、点火栓２５の近傍に可燃混合気層が形成されるとともに、その他の領域にリーン混合気層が形成され、いわゆる弱成層燃焼が実現される。
【００４５】
また、ＥＣＵ２０は、内燃機関１の運転状態がアイドル運転領域にあると判定した場合は、実際の機関回転数を目標アイドル回転数に収束させるために必要な吸入空気量を確保すべくスロットル弁３９の開度を制御する、いわゆるアイドルスピードコントロール（ＩＳＣ）のフィードバック制御を行う。
【００４６】
次に、ＥＣＵ２０は、未燃燃料成分（未燃ＨＣ）の大気中への排出量を低減すべきときに、排気昇温制御を実行する。
排気昇温制御では、ＥＣＵ２０は、図４に示すような排気昇温制御ルーチンを実行する。この排気昇温制御ルーチンは、ＥＣＵ２０に内蔵されたＲＯＭなどに予め記憶されているルーチンであり、所定時間毎（例えば、クランクポジションセンサ５１がパルス信号を出力する毎）に繰り返し実行されるルーチンである。
【００４７】
排気昇温制御ルーチンでは、ＥＣＵ２０は、先ず、Ｓ４０１において、内燃機関１から排出される未燃燃料成分（未燃ＨＣ）を低減すべき時期であるか否かを判別する。
【００４８】
内燃機関１から排出される未燃ＨＣを低減すべき時期としては、例えば、内燃機関１が冷間始動後の暖機運転状態にある場合や、内燃機関１が低負荷運転状態にある場合のように、内燃機関１の燃焼室２４の温度が低く、排気浄化触媒４６が未活性状態にある場合である。
【００４９】
これは、内燃機関１の燃焼室２４内の温度が低いときは、燃焼室２４内において混合気の燃焼状態が不安定となり易く混合気が完全燃焼し難いため、燃焼室２４から多量の未燃ＨＣが排出されることになり、その際に排気浄化触媒４６が未活性状態にあると排気中に含まれる未燃ＨＣが排気浄化触媒４６にて十分に浄化されずに大気中に放出されることになるからである。
【００５０】
前記Ｓ４０１において、内燃機関１から排出される未燃ＨＣを低減すべき時期ではないと判定した場合は、ＥＣＵ２０は、本ルーチンの実行を一旦終了する。
一方、前記Ｓ４０１において、内燃機関１から排出される未燃ＨＣを低減すべき時期であると判定した場合は、ＥＣＵ２０は、Ｓ４０２へ進み、排気昇温処理の実行を開始する。
【００５１】
排気昇温処理では、ＥＣＵ２０は、排気絞り弁４９をほぼ全閉状態とすべくアクチュエータ５０を制御する。この場合、排気ポート２７内、排気枝管４５内、及び排気絞り弁４９より上流の排気管４７内において、排気の圧力が高くなる。このように排気圧力が高くなると、燃焼室２４から排気ポート２７へ排出された排気の圧力が低下せず、それに応じて排気の温度低下が抑制されることになる。更に、排気絞り弁４９がほぼ全閉状態にされると、排気ポート２７から排気絞り弁４９に至る排気通路内における排気の流速が低下することになる。
【００５２】
この結果、燃焼室２４から排出された排気は、排気絞り弁４９より上流の排気通路内において高温の状態で長期間滞留することになり、その間に、排気中に残存していた未燃ＨＣが酸化されることになる。
【００５３】
ところで、排気絞り弁４９がほぼ全閉状態とされても、燃焼室２４から排気ポート２７へ排出された時点における排気の温度が過剰に低い場合や、燃焼室２４から排出される排気に含まれる未燃ＨＣ量が過剰に多い場合は、未燃ＨＣの酸化反応が十分に行われなくなる虞がある。
【００５４】
そこで、本実施の形態に係る排気昇温処理では、ＥＣＵ２０は、排気絞り弁４９をほぼ全閉状態に制御するとともに、機関出力に寄与する主たる燃料の噴射に加えて主燃料噴射後の所定の時期に副次的に燃料を噴射する副噴射を行うべく燃料噴射弁３２を制御するようにした。
【００５５】
この場合、燃焼室２４内では、主燃料の燃え残りである未燃ＨＣが副燃料を着火源として燃焼せしめられることになる。その際、副燃料の噴射は、主燃料が燃焼した直後の高温下で行われるため、副燃料がほぼ完全燃焼することとなり、副燃料の噴射に起因した未燃ＨＣの発生量は極わずかとなる。
【００５６】
更に、上記したように副燃料が燃焼室２４内で燃焼せしめられると、主燃料の燃焼熱に加えて、副燃料の燃焼熱と未燃ＨＣの燃焼熱とが発生することになり、燃焼室２４内の既燃ガスの温度が一層高くなる。
【００５７】
この結果、燃焼室２４から排気ポート２７へ排出される排気の温度が十分に高くなるとともに、排気中に残存する未燃ＨＣ量が低減されることになり、排気絞り弁４９より上流の排気通路において排気中に残存する未燃ＨＣのほぼすべてが酸化されるようになる。更に、本実施の形態では、排気浄化触媒４６が排気絞り弁４９より上流の排気通路に配置されるため、上記したように排気温度が高められると、排気浄化触媒４６が高温の排気に長期間曝され、排気浄化触媒４６の活性化が促進される。
【００５８】
尚、副燃料の噴射時期については、燃焼室２４から排気ポート２７へ排出された排気の温度が十分に高く、且つ排気中に残存する未燃ＨＣが最も少なくなる時期を予め実験的に求めておくことが好ましい。
【００５９】
例えば、本実施の形態で例示した内燃機関１が冷間始動後の暖機運転状態にある場合は、図５に示すように、クランクシャフト２３が各気筒２１の膨張行程における上死点後６０°近傍にあるときに副燃料の噴射が実行されると、燃焼室２４から排気ポート２７へ排出される未燃ＨＣ量が最も少なくなり、且つ、燃焼室２４から排気ポート２７へ排出される排気の温度が十分に高くなるため、ＥＣＵ２０は、クランクシャフト２３が各気筒２１の膨張行程における上死点後６０°付近で副燃料の噴射制御を実行すればよい。
【００６０】
また、排気絞り弁４９がほぼ全閉状態とされて排気圧力が上昇すると、その排気圧力が背圧として内燃機関１に作用するため、内燃機関１の出力が低下してしまう。これに対し、本実施の形態では、ＥＣＵ２０は、排気絞り弁４９をほぼ全閉状態に制御する際に、内燃機関１の出力を、排気絞り弁４９が全開状態にあるときの出力と一致させるべく主燃料噴射量を増量するようにした。
【００６１】
また、図５に示した例では、燃焼室２４から排出される未燃ＨＣ量が最も少なくなる時期に副燃料の噴射が実行されると、煤などの粒子状物質が多量に発生することになるが、本実施の形態に係る排気昇温装置では、内燃機関１の排気通路にウォールスルー型の排気浄化触媒４６が設けられているため、排気中に含まれる粒子状物質は、排気浄化触媒４６にて除去されることとなり、大気中に放出されることがない。
【００６２】
ここで、図４の排気昇温制御ルーチンに戻り、ＥＣＵ２０は、上記したようなＳ４０２の処理を実行した後、Ｓ４０３へ進み、排気浄化触媒４６が活性したか否かを判別する。
【００６３】
排気浄化触媒４６が活性したか否かを判別する方法としては、排気昇温処理の実行時間から推定するようにしてもよく、あるいは排気浄化触媒４６に温度センサを取り付け、その温度センサの出力信号値に基づいて判定するようにしてもよい。
【００６４】
前記Ｓ４０２において排気浄化触媒４６が未だ活性していないと判定した場合は、ＥＣＵ２０は、Ｓ４０２へ戻り、排気昇温処理の実行を継続する。一方、前記Ｓ４０２において排気浄化触媒４６が活性したと判定した場合は、ＥＣＵ２０は、Ｓ４０４へ進み、排気昇温処理の実行を終了して、本ルーチンの実行を一旦終了する。
【００６５】
このように、ＥＣＵ２０が排気昇温制御ルーチンを実行することにより、本発明に係る弁制御手段、主燃料噴射制御手段、副燃料噴射制御手段が実現される。従って、本実施の形態に係る内燃機関の排気昇温装置によれば、内燃機関１が冷間始動後の暖機運転状態にある場合や、内燃機関１が低負荷運転状態にある場合のように、内燃機関１から排出される未燃ＨＣ量を低減すべき必要があるときに、大気中に放出される未燃ＨＣ及び粒子状物質の量を低減することが可能になるとともに、排気浄化触媒４６の早期活性化を図ることが可能となる。
【００６６】
尚、本実施の形態では、排気昇温制御において比較的多量に発生する粒子状物質を排気浄化触媒４６によって除去しているため、排気浄化触媒４６の粒子状物質吸着能力が飽和する前に、排気浄化触媒４６を再生する必要がある。
【００６７】
そこで、本実施の形態では、ＥＣＵ２０は、図６に示すような排気浄化触媒再生制御ルーチンに従って排気浄化触媒４６の吸着能力を再生するようにした。排気浄化触媒再生制御ルーチンは、ＥＣＵ２０のＲＯＭに予め記憶されたルーチンであり、ＥＣＵ２０によって所定時間毎（例えば、クランクポジションセンサ５１がパルス信号を出力する毎）に繰り返し実行されるルーチンである。
【００６８】
排気浄化触媒再生制御ルーチンでは、ＥＣＵ２０は、先ずＳ６０１において、排気浄化触媒４６の吸着能力を再生すべき時期であるか否かを判定する。この判定方法としては、例えば、内燃機関１の運転履歴をパラメータとして排気浄化触媒４６に吸着された粒子状物質量を推定し、その推定値と排気浄化触媒４６が吸着可能な粒子状物質量の最大値（最大吸着量）とを比較して、推定値が最大吸着量以上であるときは排気浄化触媒４６の吸着能力を再生すべき時期であると判定する方法を例示することができる。
【００６９】
前記Ｓ６０１において排気浄化触媒４６の吸着能力を再生すべき時期ではないと判定した場合は、ＥＣＵ２０は、本ルーチンの実行を一旦終了する。一方、前記Ｓ６０１において排気浄化触媒４６の吸着能力を再生すべき時期であると判定した場合は、ＥＣＵ２０は、Ｓ６０２へ進み、排気浄化触媒再生処理を実行する。
【００７０】
ここで、排気浄化触媒４６に吸着された粒子状物質を除去するには、排気浄化触媒４６内の雰囲気温度をおよそ５００℃以上まで上昇させるとともに、酸素過剰雰囲気にすることにより、粒子状物質を酸化（燃焼）させればよい。
【００７１】
従って、ＥＣＵ２０は、排気浄化触媒再生処理において、前述した排気昇温制御における排気昇温処理と同様の処理を所定時間実行することにより、排気浄化触媒４６に流入する排気の温度を上昇させ、排気浄化触媒４６に吸着されている粒子状物質を酸化させる。
【００７２】
前記Ｓ６０２の処理を実行し終えると、ＥＣＵ２０は、本ルーチンの実行を一旦終了する。
このようにＥＣＵ２０が排気浄化触媒再生制御ルーチンを実行することにより、
内燃機関１から排出される排気の温度を高めることが可能となる。その際、排気浄化触媒４６が排気絞り弁４９より上流の排気通路に配置されているため、排気浄化触媒４６に吸着された粒子状物質は、排気絞り弁４９より上流の排気通路に滞留する高温の排気に長期間曝され、効率的に酸化されることになる。
【００７３】
尚、内燃機関１がディーゼルエンジンや希薄燃焼式内燃機関である場合のように、排気浄化触媒が主にリーン雰囲気下で使用される場合は、排気浄化触媒が酸素によって被毒されて活性能力が低下する傾向があるため、このような場合には、排気浄化触媒を再生する際に、排気浄化触媒を一旦理論空燃比もしくはリッチ雰囲気の排気に曝して酸素被毒を解消させた後に上記したような排気昇温処理を行うようにすることが好ましい。
【００７４】
【発明の効果】
本発明に係る内燃機関の排気昇温装置では、内燃機関から排出される未燃燃料成分を低減すべき時期に、排気絞り弁の開度がほぼ全閉状態にされるとともに、主燃料の噴射後に副燃料の噴射が行われるため、排気絞り弁上流の排気通路から内燃機関の気筒内にかけて排気の圧力及び温度が上昇するとともに排気の流速が低下する。この結果、主燃料の燃え残りである未燃燃料成分と副燃料とが高温下で長期にわたって燃焼し、排気中に残存する未燃燃料成分量が低減されることになる。その際、排気中に含まれる煤などの粒子状物質は、排気通路に設けられたＰＭ除去手段によって除去されるため、大気中に放出されることがない。
【００７５】
従って、本発明に係る内燃機関の排気昇温装置によれば、内燃機関から排出される未燃燃料成分を低減すべき時期に、未燃燃料成分を確実に低減させるとともに、粒子状物質の大気中への放出も防止することが可能となる。
【００７６】
また、本発明に係る内燃機関の排気昇温装置では、ＰＭ除去手段としてＰＭトラップを用いた場合は、ＰＭトラップの吸着能力を再生する際に、排気絞り弁の開度がほぼ全閉状態にされるとともに、主燃料の噴射後に副燃料の噴射が行われるため、ＰＭトラップに流入する排気の温度が高くなり、その結果、ＰＭトラップに吸着されている粒子状物質が燃焼及び除去される。
【００７７】
その際、ＰＭトラップを排気絞り弁より上流の排気通路に配置すれば、ＰＭトラップは、排気絞り弁より上流の排気通路に滞留する高温の排気に長期間曝されることになるため、ＰＭトラップの再生効率を向上させることが可能となる。
【図面の簡単な説明】
【図１】本発明に係る内燃機関の排気昇温装置を適用する内燃機関の概略構成を示す図
【図２】排気浄化触媒の内部構成を示す図（１）
【図３】排気浄化触媒の内部構成を示す図（２）
【図４】排気昇温制御ルーチンを示すフローチャート図
【図５】副燃料噴射の時期と粒子状物質及び未燃ＨＣの排出量との関係を示す図
【図６】排気浄化触媒再生制御ルーチンを示すフローチャート図
【符号の説明】
１・・・・内燃機関
２１・・・気筒
２４・・・燃焼室
２７・・・排気ポート
２９・・・排気弁
３２・・・燃料噴射弁
４５・・・排気枝管
４６・・・排気浄化触媒
４７・・・排気管
４９・・・排気絞り弁
５０・・・アクチュエータ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for increasing the temperature of exhaust gas discharged from an internal combustion engine mounted on an automobile or the like, and more particularly to a technique for increasing the temperature of exhaust gas without deteriorating exhaust emission.
[0002]
[Prior art]
2. Description of the Related Art In an internal combustion engine mounted on an automobile or the like, it is required that a harmful gas component contained in exhaust gas discharged from the internal combustion engine be purified and then released into the atmosphere. In response to such demands, there has been proposed a technique in which an exhaust purification catalyst is disposed in an exhaust passage of an internal combustion engine, and a harmful gas component contained in exhaust gas is purified by the exhaust purification catalyst.
[0003]
By the way, since the exhaust gas purifying catalyst is generally activated when the temperature is equal to or higher than a predetermined temperature and can purify harmful gas components in the exhaust gas, the temperature of the exhaust gas purifying catalyst is low as when the internal combustion engine is cold started. When the temperature is lower than the predetermined temperature, it becomes impossible to sufficiently purify the harmful gas components in the exhaust gas.
[0004]
In order to solve such a problem, an exhaust gas heating device as described in Japanese Patent Application Laid-Open No. H10-212995 has been proposed. When the internal combustion engine is in a warm-up operation state after a cold start, the exhaust gas temperature raising device described in this publication adds to the normal fuel injection (main fuel injection) used for combustion of the internal combustion engine, By performing secondary fuel injection (auxiliary fuel injection) during the expansion stroke of each cylinder, the sub-injected fuel is burned, and the in-cylinder gas temperature when the exhaust valve is opened, in other words, the exhaust temperature is increased. Thus, early activation of the exhaust purification catalyst is intended.
[0005]
[Problems to be solved by the invention]
By the way, when the internal combustion engine is in a warm-up operation state after a cold start, a relatively large amount of unburned fuel components remain in the burned gas because the temperature in the cylinder is low and the main fuel is difficult to completely burn. Will do. When the sub-fuel injection is performed in such a situation where the remaining amount of the unburned fuel component is large, the unburned fuel component burns using the sub-fuel as an ignition source, but the sub-fuel temperature is low due to the low ambient temperature in the cylinder. The fuel and the unburned fuel component may not completely burn, and a large amount of particulate matter (PM: Particulate Matter) typified by soot and unburned fuel component may be generated.
[0006]
The present invention has been made in view of the above problems, and has as its object to provide a technique for efficiently increasing the temperature of exhaust gas without deteriorating exhaust emission.
[0007]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems. That is, an exhaust gas heating device for an internal combustion engine according to the present invention includes an exhaust throttle valve provided in an exhaust passage of the internal combustion engine for adjusting a flow rate of exhaust gas flowing through the exhaust passage, and directing fuel directly into a cylinder of the internal combustion engine. A fuel injection valve for injecting, valve control means for controlling the exhaust throttle valve to be almost fully closed when an unburned fuel component discharged from the internal combustion engine is to be reduced, and controlling the exhaust throttle valve to be almost fully closed. Main fuel injection control means for increasing the amount of main fuel injected from the fuel injection valve when the fuel injection is performed, and secondary fuel injection from the fuel injection valve after main fuel injection by the main fuel injection control means Auxiliary fuel injection control means, and PM removal means provided in the exhaust passage and removing particulate matter contained in exhaust flowing through the exhaust passage, The auxiliary fuel injection control means executes the injection of the auxiliary fuel at a time when the amount of the unburned fuel component discharged from the internal combustion engine is minimized, and removes the particulate matter by the PM removal means. It is characterized by the following.
[0008]
In the exhaust gas temperature increasing device configured as described above, the valve control unit sets the opening of the exhaust throttle valve to a substantially fully closed state at a time when the amount of the unburned fuel component discharged from the internal combustion engine should be reduced. In response, the main fuel injection control means controls the fuel injection valve to increase the injection amount of the main fuel, and the sub fuel injection control means controls the fuel injection valve to inject the sub fuel after the main fuel is injected. I do.
[0009]
In this case, due to the synergistic effect of the exhaust throttle valve that is almost fully closed and the increase in the injection amount of the main fuel, the pressure and temperature of the exhaust rise from the exhaust passage upstream of the exhaust throttle valve into the cylinder of the internal combustion engine, and the exhaust gas increases. As a result, the unburned fuel component and the auxiliary fuel, which are unburned main fuel, burn over a long period of time at a high temperature, and the remaining amount of the unburned fuel component decreases. Further, particulate matter such as soot contained in the exhaust gas is removed from the exhaust gas by the PM removing means disposed in the exhaust passage, and is not released into the atmosphere.
[0010]
Here, when the amount of the unburned fuel component discharged from the internal combustion engine should be reduced, when the internal combustion engine is in a warm-up operation state after a cold start, the internal combustion engine has a low load when the outside air temperature is low. For example, when the vehicle is in the driving state.
[0011]
In the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, the auxiliary fuel injection control means may execute the injection of the auxiliary fuel at a time when the amount of the unburned fuel component discharged from the internal combustion engine is minimized. preferable.
[0012]
In the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, a PM trap which physically adsorbs particulate matter contained in exhaust gas can be exemplified as the PM removing means.
In this case, it is necessary to regenerate the PM trap before the adsorption capacity of the PM trap is saturated. In such a case, the valve control means controls the exhaust throttle valve to be almost fully closed, and the main fuel injection control means performs the operation. The fuel injection valve is controlled to increase the injection amount of the main fuel, and the auxiliary fuel injection control means controls the fuel injection valve to execute the injection of the auxiliary fuel, so that the temperature of the exhaust gas passing through the PM trap is increased. What should I do?
[0013]
In the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, it is preferable that the PM removing unit is disposed in the exhaust passage upstream of the exhaust throttle valve.
This is because when the exhaust throttle valve is almost fully closed, the exhaust flow velocity is lower in the exhaust passage upstream of the exhaust throttle valve than in the exhaust passage downstream of the exhaust throttle valve, and the high-temperature exhaust gas stays. This is because the PM removing means is exposed to high-temperature exhaust gas for a long period of time to improve the particulate matter regeneration efficiency.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a specific embodiment of an exhaust gas heating device for an internal combustion engine according to the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas heating device according to the present invention is applied. The internal combustion engine 1 shown in FIG. 1 is a four-cycle in-cylinder internal combustion engine having a plurality of cylinders 21 and a fuel injection valve 32 for directly injecting fuel into each cylinder 21.
[0016]
The internal combustion engine 1 includes a cylinder block 1b in which a plurality of cylinders 21 and a cooling water passage 1c are formed, and a cylinder head 1a fixed above the cylinder block 1b.
[0017]
A crankshaft 23, which is an engine output shaft, is rotatably supported by the cylinder block 1b. The crankshaft 23 is connected to a piston 22 slidably mounted in each cylinder 21.
[0018]
Above the piston 22, a combustion chamber 24 surrounded by the top surface of the piston 22 and the wall surface of the cylinder head 1a is formed. An ignition plug 25 is attached to the cylinder head 1a so as to face the combustion chamber 24. The ignition plug 25 is connected to an igniter 25a for applying a drive current to the ignition plug 25.
[0019]
In the cylinder head 1a, an open end of two intake ports 26 and an open end of two exhaust ports 27 are formed so as to face the combustion chamber 24, and the fuel injection valve is formed such that its injection hole faces the combustion chamber 24. 32 are attached.
[0020]
Each open end of the intake port 26 is opened and closed by an intake valve 28 supported on the cylinder head 1a so as to be movable forward and backward. The intake valve 28 is rotatably supported on the cylinder head 1a. It is configured to be driven forward and backward by the side camshaft 30.
[0021]
Each open end of the exhaust port 27 is opened and closed by an exhaust valve 29 supported on the cylinder head 1a so as to be able to advance and retreat, and these exhaust valves 29 are rotatably supported on the cylinder head 1a. It is configured to be driven forward and backward by the side camshaft 31.
[0022]
The intake camshaft 30 and the exhaust camshaft 31 are connected to the crankshaft 23 via a timing belt (not shown), and the rotational torque of the crankshaft 23 is applied to the intake camshaft 30 and the exhaust cam via the timing belt. The power is transmitted to the shaft 31.
[0023]
One of the two intake ports 26 communicating with each cylinder 21 has a flow path formed linearly from an open end formed on the outer wall of the cylinder head 1 a to an open end facing the combustion chamber 24. The other intake port 26 has a flow port formed to swirl in a plane perpendicular to the axial direction of the cylinder 21 from the open end of the outer wall of the cylinder head 1a to the open end of the combustion chamber 24. It consists of a helical port with a road.
[0024]
Each intake port 26 communicates with each branch pipe of the intake branch pipe 33 attached to the cylinder head 1a. A branch pipe communicating with a straight port of the two intake ports 26 corresponding to each cylinder 21 is provided with a swirl control valve 37 for adjusting a flow rate in the branch pipe. The swirl control valve 37 includes a stepper motor or the like, an actuator 37a for opening and closing the swirl control valve 37 in accordance with the magnitude of the applied current, and an SCV for outputting an electric signal corresponding to the opening of the swirl control valve 37. The position sensor 37b is attached.
[0025]
The intake branch pipe 33 is connected to a surge tank 34, and the surge tank 34 is connected to an air cleaner box 36 via an intake pipe 35. The intake pipe 35 is provided with a throttle valve 39 for adjusting the flow rate of fresh air flowing through the intake pipe 35.
[0026]
The throttle valve 39 includes a stepper motor or the like, and an actuator 40 that opens and closes the throttle valve 39 according to the magnitude of the applied current, and a throttle position that outputs an electric signal corresponding to the opening of the throttle valve 39. The sensor 41 is attached.
[0027]
Further, the throttle valve 39 is provided with an accelerator lever (not shown) which rotates in conjunction with an accelerator pedal 42. The accelerator lever corresponds to the rotational position of the accelerator lever (the amount of depression of the accelerator pedal 42). An accelerator position sensor 43 for outputting the generated electric signal is attached.
[0028]
An air flow meter 44 that outputs an electric signal corresponding to a mass of fresh air flowing through the intake pipe 35 (a mass of intake air) is attached to the intake pipe 35 upstream of the throttle valve 39.
[0029]
On the other hand, each exhaust port 27 of the internal combustion engine 1 communicates with each branch pipe of the exhaust branch pipe 45 attached to the cylinder head 1a. The exhaust branch pipe 45 is connected to an exhaust pipe 47 via an exhaust purification catalyst 46, and the exhaust pipe 47 is connected downstream to a muffler (not shown).
[0030]
The exhaust gas purifying catalyst 46 realizes the PM removing means according to the present invention. For example, as shown in FIGS. 2 and 3, the upstream end is opened and the downstream end is closed. A porous carrier in which the first flow path 46a and the second flow path 46b whose upstream end is closed and whose downstream end is open are formed in a honeycomb shape; This is a wall-throw type exhaust purification catalyst comprising a catalyst layer formed on the surface.
[0031]
Examples of the support include porous ceramics and zeolites, and examples of the catalyst layer include porous alumina (Al). 2 O 3 ) On which platinum-rhodium (Pt-Rh) -based or palladium-rhodium (Pd-Rh) -based noble metal catalyst material is supported, or potassium (K), sodium (Na), lithium (Li) or At least one selected from an alkali metal such as cesium (Cs), an alkaline earth such as barium (Ba) and calcium (Ca), and a rare earth such as lanthanum (La) and yttrium (Y); and platinum (Pt) ) Can be exemplified.
[0032]
In the exhaust gas purifying catalyst 46 configured as described above, the exhaust gas flowing into the exhaust gas purifying catalyst 46 is first guided to the first flow path 46a, and then flows to the second flow path 46b through the pores on the wall surface of the carrier. Are discharged from the second flow passage 46b to the exhaust pipe 47 downstream. When the exhaust gas passes through the wall surface of the carrier, particulate matter such as soot and unburned fuel components contained in the exhaust gas are collected, and the harmful gas components contained in the exhaust gas are purified by the catalyst layer. . Therefore, the exhaust gas purifying catalyst 46 has both a function of a filter for trapping particulate matter in the exhaust gas and a catalytic function of purifying a harmful gas component in the exhaust gas.
[0033]
Returning to FIG. 1, an oxygen sensor (O2 sensor) 48 for outputting an electric signal corresponding to the concentration of oxygen contained in exhaust gas flowing through the exhaust branch pipe 45 is attached to the exhaust branch pipe 45. .
[0034]
An exhaust throttle valve 49 for adjusting the flow rate of exhaust flowing through the exhaust pipe 47 is provided in the exhaust pipe 47. The exhaust throttle valve 49 is provided with an actuator 50 comprising a stepper motor or the like and driving the opening and closing of the exhaust throttle valve 49 according to the magnitude of the applied current.
[0035]
Further, the internal combustion engine 1 includes a crank position sensor 51 including a timing rotor 51a attached to an end of the crankshaft 23 and an electromagnetic pickup 51b attached to a cylinder block 1b near the timing rotor 51a. And a water temperature sensor 52 attached to the cylinder block 1b to detect the temperature of the cooling water flowing through the cooling water passage 1c formed in the cylinder block 1b.
[0036]
The thus configured internal combustion engine 1 is provided with an electronic control unit (Electronic Control Unit: ECU, hereinafter referred to as ECU) 20 for controlling the operating state of the internal combustion engine 1.
[0037]
Various sensors such as an SCV position sensor 37b, a throttle position sensor 41, an accelerator position sensor 43, an air flow meter 44, an oxygen sensor 48, a crank position sensor 51, and a water temperature sensor 52 are connected to the ECU 20 via electric wiring. The output signal of each sensor is input to the ECU 20.
[0038]
An igniter 25a, a fuel injection valve 32, an actuator 37a, an actuator 40, an actuator 50, and the like are connected to the ECU 20 via electrical wiring. The ECU 20 uses the igniter 25a, The fuel injection valve 32, the actuator 37a, the actuator 40, and the actuator 50 can be controlled.
[0039]
For example, the ECU 20 determines the operating state of the internal combustion engine 1 using output signal values of the crank position sensor 51, the accelerator position sensor 43, the air flow meter 44, and the like as parameters. When it is determined that the operation state of the internal combustion engine 1 is in the low load operation region, the ECU 20 transmits a control signal to the actuator 37a to open the swirl control valve 37 in order to realize the stratified combustion of the internal combustion engine 1. The throttle valve 39 is substantially fully opened by transmitting a control signal to the actuator 40 and the drive current is applied to the fuel injection valve 32 during the compression stroke of each cylinder 21 to perform the compression stroke injection.
[0040]
In this case, fresh air mainly from the swirl port 7b is introduced into the combustion chamber 24 of each cylinder 21 during the intake stroke, and a strong swirl flow (swirl flow) is generated. In the subsequent compression stroke, the fuel injected from the fuel injection valve 32 swirls in the combustion chamber 24 according to the swirl flow, and moves to the vicinity of the spark plug 25 at a predetermined timing. At this time, the combustion chamber 24 is in a so-called stratified state in which the vicinity of the ignition plug 25 is a combustible air-fuel mixture layer and the other areas are air layers. Then, the ECU 20 drives the igniter 25a to ignite the spark plug 25 at the above-mentioned predetermined time. As a result, the mixture in the combustion chamber 24 (including the combustible mixture layer and the air layer) burns using the combustible mixture layer near the ignition plug 25 as an ignition source.
[0041]
The fuel injection amount during the stratified charge combustion operation is determined using the accelerator opening and the engine speed as parameters. That is, the ECU 20 determines the fuel injection amount (fuel injection time) using a stratified combustion fuel injection control map indicating the relationship between the output signal value of the accelerator position sensor 43 (accelerator opening), the engine speed, and the fuel injection amount. decide.
[0042]
When the ECU 20 determines that the operation state of the internal combustion engine 1 is in the medium load operation range, the ECU 20 transmits a control signal to the actuator 37a to realize the homogeneous lean combustion by the lean air-fuel mixture. The opening is reduced, and a drive current is applied to the fuel injection valve 32 during the intake stroke of each cylinder 21 to perform the intake stroke injection. In this case, a lean mixture in which fresh air and fuel are homogeneously mixed is formed over substantially the entire region in the combustion chamber 24 of each cylinder 21, and homogeneous lean combustion is realized.
[0043]
When the ECU 20 determines that the operation state of the internal combustion engine 1 is in the high-load operation range, the ECU 20 transmits a control signal to the actuator 37a to realize the homogeneous combustion with the air-fuel mixture near the stoichiometric air-fuel ratio. The valve 37 is fully opened, a control signal is transmitted to the actuator 40 so that the throttle valve 39 has an opening degree corresponding to the depression amount of the accelerator pedal 42 (the output signal value of the accelerator position sensor 43), and further, the intake of each cylinder 21 is performed. During a stroke, a drive current is applied to the fuel injection valve 32 to perform an intake stroke injection. In this case, a mixture with a stoichiometric air-fuel ratio in which fresh air and fuel are homogeneously mixed is formed over substantially the entire region in the combustion chamber 24 of each cylinder 21, and homogeneous combustion is realized.
[0044]
Note that the ECU 20 performs the compression stroke and the intake stroke of each cylinder 21 in order to prevent the torque fluctuation of the internal combustion engine 1 when shifting from the stratified combustion control to the homogeneous combustion control or when shifting from the homogeneous combustion control to the stratified combustion control. A drive current is applied to the fuel injection valve 32 in two stages, that is, during the stroke. In this case, in the combustion chamber 24 of each cylinder 21, a combustible mixture layer is formed in the vicinity of the spark plug 25, and a lean mixture layer is formed in other regions, so-called weak stratified combustion is realized. .
[0045]
When the ECU 20 determines that the operation state of the internal combustion engine 1 is in the idling operation range, the ECU 20 controls the throttle valve 39 to secure an intake air amount necessary for converging the actual engine speed to the target idle speed. In this case, feedback control of so-called idle speed control (ISC) for controlling the opening of the motor is performed.
[0046]
Next, the ECU 20 executes the exhaust gas temperature raising control when the amount of discharge of the unburned fuel component (unburned HC) into the atmosphere should be reduced.
In the exhaust gas temperature raising control, the ECU 20 executes an exhaust gas temperature raising control routine as shown in FIG. This exhaust gas temperature raising control routine is a routine stored in advance in a ROM or the like built in the ECU 20, and is a routine that is repeatedly executed at predetermined time intervals (for example, every time the crank position sensor 51 outputs a pulse signal). is there.
[0047]
In the exhaust gas temperature raising control routine, the ECU 20 first determines in S401 whether it is time to reduce the unburned fuel component (unburned HC) discharged from the internal combustion engine 1 or not.
[0048]
The timing to reduce the unburned HC discharged from the internal combustion engine 1 is, for example, when the internal combustion engine 1 is in a warm-up operation state after a cold start or when the internal combustion engine 1 is in a low load operation state. Thus, the case where the temperature of the combustion chamber 24 of the internal combustion engine 1 is low and the exhaust purification catalyst 46 is in an inactive state.
[0049]
This is because when the temperature in the combustion chamber 24 of the internal combustion engine 1 is low, the combustion state of the air-fuel mixture tends to be unstable in the combustion chamber 24 and the air-fuel mixture is difficult to completely burn, so that a large amount of unburned HC is exhausted. At this time, if the exhaust purification catalyst 46 is in an inactive state, the unburned HC contained in the exhaust is released to the atmosphere without being sufficiently purified by the exhaust purification catalyst 46. Because it will be.
[0050]
If it is determined in S401 that it is not time to reduce the unburned HC discharged from the internal combustion engine 1, the ECU 20 once ends the execution of this routine.
On the other hand, if it is determined in S401 that it is time to reduce the unburned HC discharged from the internal combustion engine 1, the ECU 20 proceeds to S402 and starts execution of the exhaust gas temperature raising process.
[0051]
In the exhaust gas temperature raising process, the ECU 20 controls the actuator 50 so that the exhaust throttle valve 49 is almost fully closed. In this case, the exhaust pressure increases in the exhaust port 27, the exhaust branch pipe 45, and the exhaust pipe 47 upstream of the exhaust throttle valve 49. When the exhaust pressure increases in this manner, the pressure of the exhaust gas discharged from the combustion chamber 24 to the exhaust port 27 does not decrease, and accordingly, the temperature of the exhaust gas is suppressed from decreasing. Further, when the exhaust throttle valve 49 is almost fully closed, the flow velocity of exhaust gas in the exhaust passage from the exhaust port 27 to the exhaust throttle valve 49 decreases.
[0052]
As a result, the exhaust gas discharged from the combustion chamber 24 stays at a high temperature for a long time in the exhaust passage upstream of the exhaust throttle valve 49, during which time the unburned HC remaining in the exhaust gas is removed. It will be oxidized.
[0053]
By the way, even if the exhaust throttle valve 49 is almost fully closed, the temperature of the exhaust gas at the time when the exhaust gas is discharged from the combustion chamber 24 to the exhaust port 27 is excessively low or is included in the exhaust gas discharged from the combustion chamber 24. If the unburned HC amount is excessively large, there is a possibility that the oxidation reaction of the unburned HC may not be sufficiently performed.
[0054]
Therefore, in the exhaust gas temperature raising process according to the present embodiment, the ECU 20 controls the exhaust throttle valve 49 to a substantially fully closed state, and in addition to the injection of the main fuel contributing to the engine output, a predetermined amount after the main fuel injection. The fuel injection valve 32 is controlled so as to perform the sub-injection for injecting the fuel at the timing.
[0055]
In this case, in the combustion chamber 24, unburned HC, which is the unburned main fuel, is burned using the auxiliary fuel as an ignition source. At that time, since the injection of the auxiliary fuel is performed at a high temperature immediately after the main fuel is burned, the auxiliary fuel is almost completely burned, and the amount of unburned HC generated by the injection of the auxiliary fuel is extremely small. Become.
[0056]
Further, when the auxiliary fuel is burned in the combustion chamber 24 as described above, the combustion heat of the auxiliary fuel and the combustion heat of the unburned HC are generated in addition to the combustion heat of the main fuel, and the combustion chamber The temperature of the burned gas in 24 becomes higher.
[0057]
As a result, the temperature of the exhaust gas discharged from the combustion chamber 24 to the exhaust port 27 becomes sufficiently high, and the amount of unburned HC remaining in the exhaust gas is reduced. , Almost all of the unburned HC remaining in the exhaust gas is oxidized. Further, in this embodiment, since the exhaust purification catalyst 46 is disposed in the exhaust passage upstream of the exhaust throttle valve 49, when the exhaust temperature is increased as described above, the exhaust purification catalyst 46 is As a result, the activation of the exhaust purification catalyst 46 is promoted.
[0058]
As for the injection timing of the auxiliary fuel, the timing at which the temperature of the exhaust gas discharged from the combustion chamber 24 to the exhaust port 27 is sufficiently high and the amount of unburned HC remaining in the exhaust gas is minimized is experimentally obtained in advance. Preferably.
[0059]
For example, when the internal combustion engine 1 exemplified in the present embodiment is in a warm-up operation state after a cold start, as shown in FIG. °, when the injection of the auxiliary fuel is executed, the amount of unburned HC discharged from the combustion chamber 24 to the exhaust port 27 becomes the smallest and the exhaust gas discharged from the combustion chamber 24 to the exhaust port 27 Is sufficiently high, the ECU 20 may execute the auxiliary fuel injection control at around 60 ° after the top dead center of the crankshaft 23 in the expansion stroke of each cylinder 21.
[0060]
Further, when the exhaust throttle valve 49 is almost fully closed and the exhaust pressure rises, the exhaust pressure acts on the internal combustion engine 1 as a back pressure, so that the output of the internal combustion engine 1 decreases. On the other hand, in the present embodiment, when controlling the exhaust throttle valve 49 to be almost fully closed, the ECU 20 matches the output of the internal combustion engine 1 with the output when the exhaust throttle valve 49 is fully opened. The main fuel injection amount was increased as much as possible.
[0061]
Further, in the example shown in FIG. 5, if the injection of the auxiliary fuel is performed at a time when the amount of unburned HC discharged from the combustion chamber 24 is minimized, a large amount of particulate matter such as soot is generated. However, in the exhaust gas temperature raising apparatus according to the present embodiment, since the wall-through type exhaust gas purification catalyst 46 is provided in the exhaust passage of the internal combustion engine 1, the particulate matter contained in the exhaust gas is It will be removed at 46 and will not be released into the atmosphere.
[0062]
Here, returning to the exhaust gas temperature raising control routine of FIG. 4, the ECU 20 executes the above-described process of S402, and then proceeds to S403 to determine whether or not the exhaust purification catalyst 46 has been activated.
[0063]
As a method for determining whether or not the exhaust gas purification catalyst 46 has been activated, it may be estimated from the execution time of the exhaust gas temperature raising process, or a temperature sensor may be attached to the exhaust gas purification catalyst 46 and the output signal of the temperature sensor may be estimated. The determination may be made based on the value.
[0064]
If it is determined in S402 that the exhaust purification catalyst 46 has not been activated yet, the ECU 20 returns to S402 and continues the execution of the exhaust gas temperature raising process. On the other hand, if it is determined in S402 that the exhaust purification catalyst 46 has been activated, the ECU 20 proceeds to S404, ends the execution of the exhaust gas temperature raising process, and once ends the execution of this routine.
[0065]
As described above, the valve control unit, the main fuel injection control unit, and the auxiliary fuel injection control unit according to the present invention are realized by the ECU 20 executing the exhaust gas temperature increase control routine. Therefore, according to the exhaust gas temperature raising apparatus for an internal combustion engine according to the present embodiment, the internal combustion engine 1 is in a warm-up operation state after a cold start, or when the internal combustion engine 1 is in a low load operation state. In addition, when it is necessary to reduce the amount of unburned HC discharged from the internal combustion engine 1, it becomes possible to reduce the amount of unburned HC and particulate matter released into the atmosphere, and to purify exhaust gas. This enables early activation of the catalyst 46.
[0066]
In the present embodiment, since the particulate matter generated in a relatively large amount in the exhaust gas temperature rise control is removed by the exhaust purification catalyst 46, the particulate matter adsorption capacity of the exhaust purification catalyst 46 is not saturated before the exhaust purification catalyst 46 becomes saturated. It is necessary to regenerate the exhaust purification catalyst 46.
[0067]
Therefore, in the present embodiment, the ECU 20 regenerates the adsorption capacity of the exhaust purification catalyst 46 according to an exhaust purification catalyst regeneration control routine as shown in FIG. The exhaust purification catalyst regeneration control routine is a routine stored in the ROM of the ECU 20 in advance, and is a routine that is repeatedly executed by the ECU 20 at predetermined time intervals (for example, every time the crank position sensor 51 outputs a pulse signal).
[0068]
In the exhaust purification catalyst regeneration control routine, the ECU 20 first determines in S601 whether it is time to regenerate the adsorption capacity of the exhaust purification catalyst 46. As this determination method, for example, the amount of particulate matter adsorbed on the exhaust gas purification catalyst 46 is estimated using the operation history of the internal combustion engine 1 as a parameter, and the estimated value and the amount of particulate matter that the exhaust gas purification catalyst 46 can adsorb are used. A method of comparing with a maximum value (maximum adsorption amount) and judging that it is time to regenerate the adsorption capacity of the exhaust purification catalyst 46 when the estimated value is equal to or larger than the maximum adsorption amount can be exemplified.
[0069]
If it is determined in S601 that it is not time to regenerate the adsorption capacity of the exhaust purification catalyst 46, the ECU 20 once ends the execution of this routine. On the other hand, if it is determined in S601 that it is time to regenerate the adsorption capacity of the exhaust purification catalyst 46, the ECU 20 proceeds to S602 and executes an exhaust purification catalyst regeneration process.
[0070]
Here, in order to remove the particulate matter adsorbed on the exhaust purification catalyst 46, the temperature of the atmosphere in the exhaust purification catalyst 46 is raised to about 500 ° C. or more, and the particulate matter is reduced by making the atmosphere excessive in oxygen. It may be oxidized (burned).
[0071]
Therefore, in the exhaust purification catalyst regeneration process, the ECU 20 executes the same process as the exhaust gas temperature increase process in the exhaust gas temperature increase control described above for a predetermined time, thereby increasing the temperature of the exhaust gas flowing into the exhaust gas purification catalyst 46, and The particulate matter adsorbed on the purification catalyst 46 is oxidized.
[0072]
After the execution of the process of S602, the ECU 20 once ends the execution of this routine.
As described above, by the ECU 20 executing the exhaust gas purification catalyst regeneration control routine,
The temperature of the exhaust gas discharged from the internal combustion engine 1 can be increased. At that time, since the exhaust purification catalyst 46 is disposed in the exhaust passage upstream of the exhaust throttle valve 49, the particulate matter adsorbed by the exhaust purification catalyst 46 stays in the exhaust passage upstream of the exhaust throttle valve 49. For a long period of time, it is oxidized efficiently.
[0073]
When the exhaust purification catalyst is used mainly in a lean atmosphere, such as when the internal combustion engine 1 is a diesel engine or a lean burn type internal combustion engine, the exhaust purification catalyst is poisoned by oxygen and the activation capacity is reduced. In such a case, when the exhaust gas purifying catalyst is regenerated, the exhaust gas purifying catalyst is once exposed to a stoichiometric air-fuel ratio or exhaust gas in a rich atmosphere to eliminate oxygen poisoning. It is preferable to perform an exhaust temperature raising process.
[0074]
【The invention's effect】
In the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, at the time when the unburned fuel component discharged from the internal combustion engine is to be reduced, the opening degree of the exhaust throttle valve is almost fully closed and the main fuel is injected. Since the injection of the auxiliary fuel is performed later, the pressure and temperature of the exhaust gas increase from the exhaust passage upstream of the exhaust throttle valve into the cylinder of the internal combustion engine, and the flow velocity of the exhaust gas decreases. As a result, the unburned fuel component, which is the unburned main fuel, and the auxiliary fuel are burned at a high temperature for a long time, and the amount of the unburned fuel component remaining in the exhaust gas is reduced. At that time, since particulate matter such as soot contained in the exhaust gas is removed by the PM removing means provided in the exhaust passage, it is not released into the atmosphere.
[0075]
Therefore, according to the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, the unburned fuel component is reliably reduced at the time when the unburned fuel component discharged from the internal combustion engine should be reduced, and the particulate matter air It is also possible to prevent release into the inside.
[0076]
Further, in the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, when the PM trap is used as the PM removing means, when the adsorption capacity of the PM trap is regenerated, the opening degree of the exhaust throttle valve is set to a substantially fully closed state. At the same time, since the auxiliary fuel is injected after the injection of the main fuel, the temperature of the exhaust gas flowing into the PM trap increases, and as a result, the particulate matter adsorbed in the PM trap is burned and removed.
[0077]
At this time, if the PM trap is disposed in the exhaust passage upstream of the exhaust throttle valve, the PM trap is exposed to high-temperature exhaust gas remaining in the exhaust passage upstream of the exhaust throttle valve for a long time. It is possible to improve the regeneration efficiency.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas heating device for an internal combustion engine according to the present invention is applied;
FIG. 2 is a diagram (1) showing an internal configuration of an exhaust purification catalyst.
FIG. 3 is a diagram (2) showing an internal configuration of an exhaust purification catalyst.
FIG. 4 is a flowchart showing an exhaust gas temperature rise control routine.
FIG. 5 is a diagram showing the relationship between the timing of auxiliary fuel injection and the emission amounts of particulate matter and unburned HC.
FIG. 6 is a flowchart illustrating an exhaust purification catalyst regeneration control routine.
[Explanation of symbols]
1 ... Internal combustion engine
21 ... cylinder
24 ... combustion chamber
27 ・ ・ ・ Exhaust port
29 ・ ・ ・ Exhaust valve
32 ... fuel injection valve
45 ・ ・ ・ Exhaust branch pipe
46 ・ ・ ・ Exhaust purification catalyst
47 ・ ・ ・ Exhaust pipe
49 ・ ・ ・ Exhaust throttle valve
50 Actuator

Claims (3)

内燃機関の排気通路に設けられ、前記排気通路を流れる排気の流量を調節する排気絞り弁と、
前記内燃機関の気筒内に直接燃料を噴射する燃料噴射弁と、
前記内燃機関から排出される未燃燃料成分を低減すべきときに、前記排気絞り弁をほぼ全閉に制御する弁制御手段と、
前記排気絞り弁がほぼ全閉に制御されたときに、前記燃料噴射弁から噴射される主たる燃料量を増加させる主燃料噴射制御手段と、
前記主燃料噴射制御手段による主燃料の噴射後に、前記燃料噴射弁から副次的に燃料を噴射させる副燃料噴射制御手段と、
前記排気通路に設けられ、前記排気通路を流れる排気に含まれる粒子状物質を除去するＰＭ除去手段と、を備え、
前記副燃料噴射制御手段は、前記内燃機関から排出される未燃燃料成分の量が最も少なくなる時期に副燃料の噴射を実行するとともに、前記ＰＭ除去手段によって粒子状物質を除去することを特徴とする内燃機関の排気昇温装置。An exhaust throttle valve provided in an exhaust passage of the internal combustion engine, for adjusting a flow rate of exhaust flowing through the exhaust passage;
A fuel injection valve that injects fuel directly into a cylinder of the internal combustion engine,
Valve control means for controlling the exhaust throttle valve to be almost fully closed when an unburned fuel component discharged from the internal combustion engine is to be reduced;
Main fuel injection control means for increasing a main fuel amount injected from the fuel injection valve when the exhaust throttle valve is controlled to be almost fully closed;
After injection of the main fuel by the main fuel injection control means, sub fuel injection control means for injecting fuel secondary from the fuel injection valve,
PM removal means provided in the exhaust passage, for removing particulate matter contained in exhaust flowing through the exhaust passage ,
The auxiliary fuel injection control means executes the injection of the auxiliary fuel at a time when the amount of the unburned fuel component discharged from the internal combustion engine is minimized, and removes particulate matter by the PM removal means. An exhaust gas heating device for an internal combustion engine. 前記ＰＭ除去手段は、排気中に含まれる粒子状物質を物理的に吸着するＰＭトラップであり、前記ＰＭトラップを再生する場合は、前記弁制御手段が前記排気絞り弁をほぼ全閉に制御し、前記主燃料噴射制御手段が主燃料の噴射量を増加すべく前記燃料噴射弁を制御し、前記副燃料噴射制御手段が副燃料の噴射を実行すべく前記燃料噴射弁を制御することを特徴とする請求項１に記載の内燃機関の排気昇温装置。The PM removal unit is a PM trap that physically adsorbs particulate matter contained in exhaust gas.When regenerating the PM trap, the valve control unit controls the exhaust throttle valve to be almost fully closed. The main fuel injection control means controls the fuel injection valve to increase the injection amount of the main fuel, and the auxiliary fuel injection control means controls the fuel injection valve to execute the injection of the auxiliary fuel. The exhaust gas temperature raising device for an internal combustion engine according to claim 1, wherein 前記ＰＭ除去手段は、前記排気絞り弁より上流の排気通路に設けられることを特徴とする請求項１に記載の内燃機関の排気昇温装置。The exhaust temperature raising device for an internal combustion engine according to claim 1, wherein the PM removing means is provided in an exhaust passage upstream of the exhaust throttle valve.
JP29216899A 1999-10-14 1999-10-14 Exhaust gas heating device for internal combustion engine Expired - Fee Related JP3596378B2 (en)

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JP29216899A JP3596378B2 (en) 1999-10-14 1999-10-14 Exhaust gas heating device for internal combustion engine
DE10045548A DE10045548B4 (en) 1999-10-14 2000-09-14 Exhaust gas temperature raising device and method for an internal combustion engine
FR0013020A FR2799794B1 (en) 1999-10-14 2000-10-11 METHOD AND APPARATUS FOR RAISING EXHAUST TEMPERATURE FOR AN INTERNAL COMBUSTION ENGINE

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US8631642B2 (en) 2009-12-22 2014-01-21 Perkins Engines Company Limited Regeneration assist calibration
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