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JP3729994B2 - Exhaust gas recirculation device - Google Patents

Exhaust gas recirculation device Download PDF

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Publication number
JP3729994B2
JP3729994B2 JP29068797A JP29068797A JP3729994B2 JP 3729994 B2 JP3729994 B2 JP 3729994B2 JP 29068797 A JP29068797 A JP 29068797A JP 29068797 A JP29068797 A JP 29068797A JP 3729994 B2 JP3729994 B2 JP 3729994B2
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Japan
Prior art keywords
exhaust gas
cooling water
engine
gas recirculation
egr cooler
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Expired - Fee Related
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JP29068797A
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Japanese (ja)
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JPH11125151A (en
Inventor
徳昭 小野
陽厳 囲
泰弘 筒井
洋 及川
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Mitsubishi Fuso Truck and Bus Corp
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Mitsubishi Fuso Truck and Bus Corp
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Priority to JP29068797A priority Critical patent/JP3729994B2/en
Publication of JPH11125151A publication Critical patent/JPH11125151A/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/45—Sensors specially adapted for EGR systems
    • F02M26/46—Sensors specially adapted for EGR systems for determining the characteristics of gases, e.g. composition
    • F02M26/47—Sensors specially adapted for EGR systems for determining the characteristics of gases, e.g. composition the characteristics being temperatures, pressures or flow rates
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/23—Layout, e.g. schematics
    • F02M26/28—Layout, e.g. schematics with liquid-cooled heat exchangers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B29/00—Engines characterised by provision for charging or scavenging not provided for in groups F02B25/00, F02B27/00 or F02B33/00 - F02B39/00; Details thereof
    • F02B29/04—Cooling of air intake supply
    • F02B29/0406—Layout of the intake air cooling or coolant circuit
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/02—EGR systems specially adapted for supercharged engines
    • F02M26/04—EGR systems specially adapted for supercharged engines with a single turbocharger
    • F02M26/05—High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/33—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage controlling the temperature of the recirculated gases

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Analytical Chemistry (AREA)
  • Exhaust-Gas Circulating Devices (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、車両の内燃機関から排出された排気ガスの一部を吸気通路に還流させる排気ガス還流装置に関する。
【０００２】
【従来の技術】
一般に、車両の内燃機関を駆動することによって排出される排気ガス中には、窒素酸化物などの有害物質が含まれており、これらの窒素酸化物は有害成分としてその排出量が規制されている。この窒素酸化物を低減するものとして、排気ガスを吸気通路に還流させ、燃焼温度の上昇を抑えることで窒素酸化物の生成量を抑制する排気ガス還流装置（ＥＧＲ装置）が知られている。
【０００３】
図３に従来の排気ガス還流装置の概略を示す。図３に示すように、上流端部にエアクリーナ101が装着された吸気管102は、ターボ装置103のコンプレッサ側に接続され、更に、インタークーラ104を介してエンジン105の吸気マニホールド106に接続されている。一方、エンジン105の排気マニホールド107には排気管108の上流端部が接続され、この排気管108はターボ装置103のタービン側に接続され、下流端部にマフラ109が接続されている。また、排気管108から分岐するように排気ガス還流管110が接続され、この排気ガス還流管110の下流端部は吸気管102に接続されており、排気ガス還流管110にはＥＧＲクーラ111が装着されている。このＥＧＲクーラ111にはエンジン105の冷却水配管112が配設され、排気ガスと冷却水との間で熱交換を行っている。そして、排気ガス還流管110の下流端部にはＥＧＲバルブ113が装着され、このＥＧＲバルブ113はコントロールユニット（ＥＣＵ）114によって開閉制御可能となっている。
【０００４】
従って、エンジン105の排気マニホールド107から排気管108に排出された排気ガスは、ＥＧＲバルブ113の開閉状態に応じて排気ガス還流管110に流動し、ＥＧＲクーラ111にて冷却されてから吸気管102に流動する。そのため、冷却された排気ガスの一部が吸気管102に流れて吸気と共にエンジン105に供給されることとなり、燃焼温度を下げて窒素酸化物を低減できる。
【０００５】
【発明が解決しようとする課題】
ところで、エンジンの冷態時には、燃焼室が低温であるために排気ガス中には多量の黒煙、ハイドロカーボン、窒素酸化物、一酸化炭素などの有害物質が含まれている。そのため、エンジン始動と同時に排気ガス還流を作動させたいが、上述した従来の排気ガス還流装置にあっては、エンジン105の冷態時には、排気ガスが排気ガス還流管110を通して吸気管102に供給されてしまうことから、燃焼が悪化してハイドロカーボンや一酸化炭素が増大してしまう虞がある。また、エンジン105の冷態時に、排気ガスが排気ガス還流管110を通してＥＧＲクーラ111に流動すると、排気ガスとエンジン冷却水との温度差が大きいため、排気ガスが冷却されすぎ、このＥＧＲクーラ111内にて排気ガスの水分が凝縮し、この排気ガス中の硫黄成分と混合されて硫酸となり、排気ガス還流管110や吸気管102、あるいはエンジン105内を腐食させてしまう虞がある。このような理由から、このエンジン105の冷態時には、ＥＧＲバルブ113を閉じて排気ガスを排気ガス還流管110を通して吸気管102に供給しないようにしている。
【０００６】
本発明はこのような問題を解決するものであって、エンジン始動時から早期に排気ガスを吸気系に還流可能としてこの排気ガス還流による窒素酸化物の低減効率の向上を図った排気ガス還流装置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】
上記目的を達成するための請求項１の発明の排気ガス還流装置では、排気ガスを吸気通路に還流させる排気ガス還流通路に、排気ガスを吸気通路に環流させるか否かを選択的に切り換えるＥＧＲバルブと排気ガスを冷却するＥＧＲクーラを設けると共に、エンジン冷却水をエンジンからこのＥＧＲクーラに導いて循環させる冷却水通路を設け、エンジンの冷態時に冷却水通路におけるＥＧＲクーラの上流側のエンジン冷却水を加熱する加熱手段と、エンジン冷却水温が第１冷却水温よりも低い時に加熱手段によりエンジン冷加水を加熱し、エンジン冷却水温が第１冷却水温よりも低い第２冷却水温よりも高い時にＥＧＲバルブを切り換えて排気ガスを吸気通路に環流させるべく制御を行うコントロールユニットとを設けてある。従って、エンジンの冷態時に、加熱手段によって冷却水通路の冷却水が加熱され、ＥＧＲクーラには温まった冷却水が送給されることとなり、排気ガスを排気ガス還流通路からＥＧＲクーラに導いても、冷却水と排気ガスとの温度差が大きくないため、排気ガスの水分が凝縮することはなく適正な熱交換が行われ、その結果、エンジン始動時から早期に排気ガスを吸気系に還流して窒素酸化物を低減でき、燃焼の悪化による黒煙やハイドロカーボンの大量発生や排気ガスの水分凝縮によって発生した硫酸による腐食を防止できる。
【０００８】
また、請求項２の発明の排気ガス還流装置の発明では、加熱手段は、ＥＧＲクーラ内で排気ガスと冷却水との熱交換が行われるときに、排気ガス中の水分が凝縮しない温度まで冷却水を加熱するようにしてある。従って、加熱手段の制御をエンジン冷却水の温度に応じて行うこととなり、構造が簡素化される。
【０００９】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて詳細に説明する。
【００１０】
図１に本発明の一実施形態に係る排気ガス還流装置の概略構成、図２に本実施形態の排気ガス還流装置による制御のフローチャートを示す。
【００１１】
本実施形態の排気ガス還流装置において、図１に示すように、上流端部にエアクリーナ１１が装着された吸気通路としての吸気管１２は、ターボ装置１３のコンプレッサ側に接続され、更に、インタークーラ１４を介してエンジン１５の吸気マニホールド１６に接続されている。一方、エンジン１５の排気マニホールド１７には排気通路としての排気管１８の上流端部が接続され、この排気管１８はターボ装置１３のタービン側に接続され、下流端部にマフラ１９が接続されている。また、排気管１８から分岐するように排気ガス還流通路としての排気ガス還流管２０が接続され、この排気ガス還流管２０の下流端部は吸気管１２に接続されると共に、ここにはＥＧＲバルブ２１が装着されている。
【００１２】
また、この排気ガス還流管２０にはＥＧＲクーラ２２が装着されている。このＥＧＲクーラ２２はエンジン１５との間に冷却水通路としての冷却水配管２３ａ，２３ｂが配設され、この冷却水配管２３ａ，２３ｂによってエンジン１５とＥＧＲクーラ２２との間でエンジン冷却水を循環させることで、この冷却水と排気ガスとの間で熱交換を行っている。この冷却水配管２３ａ，２３ｂにおけるＥＧＲクーラ２２の上流側の冷却水配管２３ａには、エンジン冷却水を加熱する加熱手段としての燃焼式ヒータ２４が設けられている。そして、ＥＧＲバルブ２１及び燃焼式ヒータ２４にはコントロールユニット（ＥＣＵ）２５が接続されている。即ち、このＥＣＵ２５には図示しない各種のセンサからエンジン冷却水温Ｔとエンジン回転数Ｎｅとアクセル開度ＬＰが入力されており、ＥＣＵ２５はこのエンジン冷却水温Ｔとエンジン回転数Ｎｅとアクセル開度ＬＰとに基づいてＥＧＲバルブ２１及び燃焼式ヒータ２４の駆動制御を行うようになっている。
【００１３】
従って、図２に示すように、ステップＳ１において、ＥＣＵ２５がエンジン冷却水温Ｔとエンジン回転数Ｎｅとアクセル開度ＬＰとを読み込む。そして、ステップＳ２において、エンジン冷却水温Ｔが所定の第１冷却水温Ｔ1 （例えば、８０℃）より低いかどうかを判定し、エンジン冷却水温Ｔが所定の第１冷却水温Ｔ1 より低ければ、ステップＳ３に移行して燃焼式ヒータ２４を点火とする。更に、ステップＳ４において、エンジン冷却水温Ｔが所定の第２冷却水温Ｔ2 （例えば、５０℃）より低いかどうかを判定し、エンジン冷却水温Ｔが所定の第２冷却水温Ｔ2 より低ければ、ステップＳ５に移行してＥＧＲバルブ２１の開閉制御は行わないようにする。
【００１４】
そのため、図１に示すように、エンジン冷却水温Ｔが所定の第１冷却水温Ｔ1 より低いエンジンの冷態時には、燃焼式ヒータ２４が点火されることでＥＧＲクーラ２２の上流側にある冷却水配管２３ａ内のエンジン冷却水が加熱されることとなる。すると、温まったエンジン冷却水がＥＧＲクーラ２２内に供給され、且つ、冷却水配管２３ｂを通ってエンジン１５に戻ることとなり、冷却水配管２３ａ，２３ｂによって循環するエンジン冷却水を、燃焼式ヒータ２４によって加熱することでエンジンの暖機が促進される。
【００１５】
そして、このように燃焼式ヒータ２４によってエンジン冷却水を温める一方、図２に示すように、ステップＳ１〜Ｓ５の処理を繰り返し行っており、ステップＳ５にて、エンジン冷却水温Ｔが所定の第２冷却水温Ｔ2 以上になると、ステップＳ６に移行して燃焼式ヒータ２４を点火したまま、ＥＧＲバルブ２１の開閉制御を行う。即ち、エンジン１５を暖機しながらＥＧＲを行うこととなる。この場合、ＥＣＵ２５はエンジン回転数Ｎｅとアクセル開度ＬＰに基づいて制御を行う。また、ステップＳ２にて、エンジン冷却水温Ｔが上昇して所定の第１冷却水温Ｔ1 以上となると、ステップＳ７に移行して燃焼式ヒータ２４を消火してから、ステップＳ６にてＥＧＲバルブ２１の開閉制御を行う。
【００１６】
そのため、図１に示すように、排気ガスが排気ガス還流管２０からＥＧＲクーラ２２に導かれ、ここでエンジン冷却水との間で熱交換が行われて排気ガスが冷却され、排気ガス還流管２０を通って吸気管１２に流動する。そのため、排気ガスの一部が吸気管１２に流れて吸気と共にエンジン１５に供給されることとなり、このエンジン１５内では燃焼温度を下げて窒素酸化物を低減できる。
【００１７】
このように本実施形態の排気ガス還流装置にあっては、排気ガス還流管２０にＥＧＲクーラ２２を装着すると共に、エンジン冷却水をエンジン１５からこのＥＧＲクーラ２２に導いて循環させる冷却水配管２３ａ，２３ｂを装着し、このＥＧＲクーラ２２の上流側の冷却水配管２３ａに内部のエンジン冷却水を加熱する燃焼式ヒータ２４を設け、エンジンの冷態時にはこの燃焼式ヒータ２４によってエンジン冷却水を加熱するようにしており、エンジン１５の暖機が促進されてエンジン始動時から早期に排気ガスを吸気管１２に還流して吸気と共にエンジン１５に供給することができ、黒煙やハイドロカーボンや窒素酸化物や一酸化炭素などの有害物質の発生を抑制できる。
【００１８】
また、エンジン冷却水温Ｔが第１冷却水温Ｔ1 より低く第２冷却水温Ｔ2 より高い（５０℃＜Ｔ８０℃）ときには、燃焼式ヒータ２４でエンジン冷却水を加熱しながら、ＥＧＲバルブ２１を開閉制御して排気ガスを吸気管１２に還流して吸気と共にエンジン１５に供給するようにしており、排気ガス還流による窒素酸化物等の低減効率を向上できる。
【００１９】
このとき、燃焼式ヒータ２４によってＥＧＲクーラ２１に流れるエンジン冷却水を加熱しており、エンジンの冷態時であっても、ＥＧＲクーラ２１に導かれる排気ガスとエンジン冷却水との温度差は大きくないので、ＥＧＲクーラ２１にて排気ガス中の水分が凝縮することはなく、硫酸の発生を阻止して排気ガス還流管２０や吸気管１２やエンジン１５内などの腐食を防止できる。
【００２０】
なお、上述した本実施形態において、加熱手段を燃焼式ヒータ２４としたが、本発明の排気ガス還流装置はこれに限定されるものではなく、例えば、電気式セラミックヒータであってもよい。
【００２１】
【発明の効果】
以上、実施形態において詳細に説明したように請求項１の発明の排気ガス還流装置によれば、排気ガス還流通路にＥＧＲバルブとＥＧＲクーラを設けると共にエンジン冷却水をエンジンからこのＥＧＲクーラに導いて循環させる冷却水通路を設け、エンジンの冷態時に冷却水通路におけるＥＧＲクーラの上流側のエンジン冷却水を加熱する加熱手段と、エンジン冷却水温が第１冷却水温よりも低い時に加熱手段によりエンジン冷加水を加熱し、エンジン冷却水温が第１冷却水温よりも低い第２冷却水温よりも高い時にＥＧＲバルブを切り換えて排気ガスを吸気通路に環流させるべく制御を行うコントロールユニットとを設けたので、エンジンの冷態時には加熱手段によって冷却水通路の冷却水を加熱してＥＧＲクーラには温まった冷却水が送給され、且つ、エンジンとの間で循環することとなり、エンジンの暖機を促進することでエンジン始動時から早期に排気ガスを吸気系に還流して窒素酸化物を低減してこの排気ガス還流による窒素酸化物等の低減効率の向上を図ることができ、また、排気ガスを排気ガス還流通路からＥＧＲクーラに導いても、冷却水と排気ガスとの温度差が大きくないため、排気ガスの水分が凝縮することはなく適正な熱交換が行われ、燃焼の悪化による黒煙やハイドロカーボンの大量発生や排気ガスの水分凝縮によって発生した硫酸による腐食を防止することができる。
【００２２】
また、請求項２の発明の排気ガス還流装置によれば、加熱手段は、ＥＧＲクーラ内で排気ガスと冷却水との熱交換が行われるときに、排気ガス中の水分が凝縮しない温度まで冷却水を加熱するようにしたので、加熱手段の制御をエンジン冷却水の温度に応じて行うこととなり、構造が簡素化することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る排気ガス還流装置の概略構成図である。
【図２】本実施形態の排気ガス還流装置による制御のフローチャートである。
【図３】従来の排気ガス還流装置の概略図である。
【符号の説明】
１２ 吸気管（吸気通路）
１５ エンジン
１８ 排気管（排気通路）
２０ 排気ガス還流管（排気ガス還流通路）
２１ ＥＲＧバルブ
２２ ＥＧＲクーラ
２３ａ，２３ｂ 冷却水配管（冷却水通路）
２４ 燃焼用ヒータ（加熱手段）
２５ コントロールユニット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas recirculation device that recirculates part of exhaust gas discharged from an internal combustion engine of a vehicle to an intake passage.
[0002]
[Prior art]
In general, exhaust gas discharged by driving an internal combustion engine of a vehicle contains harmful substances such as nitrogen oxides, and the emission amounts of these nitrogen oxides are regulated as harmful components. . As a means for reducing this nitrogen oxide, an exhaust gas recirculation device (EGR device) that recirculates exhaust gas to the intake passage and suppresses the increase in combustion temperature to suppress the amount of nitrogen oxide produced is known.
[0003]
FIG. 3 shows an outline of a conventional exhaust gas recirculation device. As shown in FIG. 3, the intake pipe 102 with the air cleaner 101 mounted at the upstream end is connected to the compressor side of the turbo device 103 and further connected to the intake manifold 106 of the engine 105 via the intercooler 104. Yes. On the other hand, an upstream end portion of an exhaust pipe 108 is connected to the exhaust manifold 107 of the engine 105. The exhaust pipe 108 is connected to the turbine side of the turbo device 103, and a muffler 109 is connected to the downstream end portion. Further, an exhaust gas recirculation pipe 110 is connected so as to branch from the exhaust pipe 108, and a downstream end portion of the exhaust gas recirculation pipe 110 is connected to the intake pipe 102. The exhaust gas recirculation pipe 110 is provided with an EGR cooler 111. It is installed. The EGR cooler 111 is provided with a cooling water pipe 112 of the engine 105 to exchange heat between the exhaust gas and the cooling water. An EGR valve 113 is mounted at the downstream end of the exhaust gas recirculation pipe 110, and the EGR valve 113 can be controlled to open and close by a control unit (ECU) 114.
[0004]
Therefore, the exhaust gas discharged from the exhaust manifold 107 of the engine 105 to the exhaust pipe 108 flows to the exhaust gas recirculation pipe 110 according to the open / close state of the EGR valve 113, and after being cooled by the EGR cooler 111, To flow. Therefore, part of the cooled exhaust gas flows into the intake pipe 102 and is supplied to the engine 105 together with the intake air, so that the combustion temperature can be lowered and nitrogen oxides can be reduced.
[0005]
[Problems to be solved by the invention]
By the way, when the engine is cold, the combustion chamber is at a low temperature, and the exhaust gas contains a large amount of harmful substances such as black smoke, hydrocarbons, nitrogen oxides, and carbon monoxide. Therefore, it is desired to operate exhaust gas recirculation at the same time as starting the engine. In the above-described conventional exhaust gas recirculation device, when the engine 105 is cold, exhaust gas is supplied to the intake pipe 102 through the exhaust gas recirculation pipe 110. Therefore, there is a possibility that combustion deteriorates and hydrocarbons and carbon monoxide increase. Further, if the exhaust gas flows to the EGR cooler 111 through the exhaust gas recirculation pipe 110 when the engine 105 is in a cold state, the exhaust gas is excessively cooled because the temperature difference between the exhaust gas and the engine coolant is large, and this EGR cooler 111 There is a risk that moisture in the exhaust gas will condense inside and will be mixed with sulfur components in the exhaust gas to become sulfuric acid, which will corrode the exhaust gas recirculation pipe 110, the intake pipe 102, or the engine 105. For this reason, when the engine 105 is cold, the EGR valve 113 is closed so that the exhaust gas is not supplied to the intake pipe 102 through the exhaust gas recirculation pipe 110.
[0006]
The present invention solves such a problem, and the exhaust gas recirculation device is designed to improve the reduction efficiency of nitrogen oxides by exhaust gas recirculation so that the exhaust gas can be recirculated to the intake system at an early stage from the start of the engine. The purpose is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the exhaust gas recirculation device according to the first aspect of the present invention selectively switches whether the exhaust gas is recirculated to the intake passage or the exhaust gas recirculation passage for recirculating the exhaust gas to the intake passage. An EGR cooler for cooling the valve and the exhaust gas is provided, and a cooling water passage for circulating the engine cooling water from the engine to the EGR cooler is provided, and the engine cooling on the upstream side of the EGR cooler in the cooling water passage when the engine is cold. Heating means for heating water, and when the engine cooling water temperature is lower than the first cooling water temperature, the engine cooling water is heated by the heating means, and when the engine cooling water temperature is higher than the second cooling water temperature lower than the first cooling water temperature, EGR A control unit is provided for controlling the valve to switch the exhaust gas back to the intake passage . Accordingly, when the engine is cold, the cooling water in the cooling water passage is heated by the heating means, and the warm cooling water is supplied to the EGR cooler, leading the exhaust gas from the exhaust gas recirculation passage to the EGR cooler. However, since the temperature difference between the cooling water and the exhaust gas is not large, the moisture of the exhaust gas does not condense and proper heat exchange is performed. As a result, the exhaust gas is circulated back to the intake system early from the start of the engine. Thus, nitrogen oxides can be reduced, and corrosion due to sulfuric acid generated by the generation of a large amount of black smoke and hydrocarbons due to deterioration of combustion and moisture condensation of exhaust gas can be prevented.
[0008]
In the exhaust gas recirculation device according to the second aspect of the invention, the heating means cools to a temperature at which moisture in the exhaust gas does not condense when heat exchange is performed between the exhaust gas and the cooling water in the EGR cooler. The water is heated. Therefore, the heating means is controlled according to the temperature of the engine cooling water, and the structure is simplified.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0010]
FIG. 1 shows a schematic configuration of an exhaust gas recirculation apparatus according to an embodiment of the present invention, and FIG.
[0011]
In the exhaust gas recirculation device of this embodiment, as shown in FIG. 1, an intake pipe 12 as an intake passage having an air cleaner 11 mounted at the upstream end is connected to the compressor side of the turbo device 13, and further, an intercooler 14 is connected to the intake manifold 16 of the engine 15. On the other hand, an upstream end portion of an exhaust pipe 18 serving as an exhaust passage is connected to the exhaust manifold 17 of the engine 15. The exhaust pipe 18 is connected to the turbine side of the turbo device 13, and a muffler 19 is connected to the downstream end portion. Yes. An exhaust gas recirculation pipe 20 as an exhaust gas recirculation passage is connected so as to branch from the exhaust pipe 18, and a downstream end portion of the exhaust gas recirculation pipe 20 is connected to the intake pipe 12. 21 is attached.
[0012]
The exhaust gas recirculation pipe 20 is equipped with an EGR cooler 22. The EGR cooler 22 is provided with cooling water pipes 23 a and 23 b as cooling water passages between the engine 15 and the cooling water pipes 23 a and 23 b for circulating engine cooling water between the engine 15 and the EGR cooler 22. By doing so, heat exchange is performed between the cooling water and the exhaust gas. In the cooling water pipes 23a and 23b, the cooling water pipe 23a on the upstream side of the EGR cooler 22 is provided with a combustion heater 24 as a heating means for heating the engine cooling water. A control unit (ECU) 25 is connected to the EGR valve 21 and the combustion heater 24. That is, the ECU 25 receives the engine coolant temperature T, the engine speed Ne, and the accelerator opening LP from various sensors (not shown). The ECU 25 receives the engine coolant temperature T, the engine speed Ne, and the accelerator opening LP. Based on the above, drive control of the EGR valve 21 and the combustion heater 24 is performed.
[0013]
Therefore, as shown in FIG. 2, in step S1, the ECU 25 reads the engine coolant temperature T, the engine speed Ne, and the accelerator opening LP. In step S2, it is determined whether the engine cooling water temperature T is lower than a predetermined first cooling water temperature T 1 (for example, 80 ° C.), and if the engine cooling water temperature T is lower than the predetermined first cooling water temperature T 1 , In step S3, the combustion heater 24 is ignited. Further, in step S4, it is determined whether or not the engine cooling water temperature T is lower than a predetermined second cooling water temperature T 2 (for example, 50 ° C.), and if the engine cooling water temperature T is lower than the predetermined second cooling water temperature T 2 , The process proceeds to step S5 so that the opening / closing control of the EGR valve 21 is not performed.
[0014]
Therefore, as shown in FIG. 1, when the engine cooling water temperature T is lower than a predetermined first cooling water temperature T 1 , the cooling water on the upstream side of the EGR cooler 22 is ignited by igniting the combustion heater 24. The engine coolant in the pipe 23a will be heated. Then, the warm engine cooling water is supplied into the EGR cooler 22 and returns to the engine 15 through the cooling water pipe 23b, and the engine cooling water circulated by the cooling water pipes 23a and 23b is used as the combustion heater 24. The engine warm-up is promoted by heating by.
[0015]
Then, while the engine coolant is warmed by the combustion heater 24 as described above, the processes of steps S1 to S5 are repeated as shown in FIG. 2, and the engine coolant temperature T is a predetermined second value in step S5. becomes the cooling water temperature T 2 above, while ignition of the combustion heater 24 proceeds to step S6, controls the opening and closing of the EGR valve 21. That is, EGR is performed while the engine 15 is warmed up. In this case, the ECU 25 performs control based on the engine speed Ne and the accelerator opening LP. Further, at step S2, the engine coolant temperature T rises a predetermined first coolant temperature T 1 or more, after extinguishing the combustion heater 24 proceeds to step S7, EGR valve 21 at step S6 Open / close control is performed.
[0016]
Therefore, as shown in FIG. 1, the exhaust gas is led from the exhaust gas recirculation pipe 20 to the EGR cooler 22, where heat exchange is performed with the engine cooling water to cool the exhaust gas, and the exhaust gas recirculation pipe 20 flows to the intake pipe 12. Therefore, a part of the exhaust gas flows into the intake pipe 12 and is supplied to the engine 15 together with the intake air. In the engine 15, the combustion temperature can be lowered to reduce nitrogen oxides.
[0017]
As described above, in the exhaust gas recirculation device according to the present embodiment, the EGR cooler 22 is attached to the exhaust gas recirculation pipe 20, and the cooling water pipe 23a for circulating the engine cooling water from the engine 15 to the EGR cooler 22 is circulated. , 23b and a combustion heater 24 for heating the engine cooling water inside is provided in the cooling water pipe 23a upstream of the EGR cooler 22, and the engine cooling water is heated by the combustion heater 24 when the engine is cold. As the engine 15 is warmed up, the exhaust gas can be recirculated to the intake pipe 12 at an early stage from the start of the engine and supplied to the engine 15 together with the intake air. Generation of harmful substances such as substances and carbon monoxide.
[0018]
When the engine coolant temperature T is lower than the first coolant temperature T 1 and higher than the second coolant temperature T 2 (50 ° C. <T80 ° C.), the EGR valve 21 is opened and closed while the engine coolant is heated by the combustion heater 24. The exhaust gas is controlled to be recirculated to the intake pipe 12 and supplied to the engine 15 together with the intake air, so that the reduction efficiency of nitrogen oxides and the like due to the exhaust gas recirculation can be improved.
[0019]
At this time, the engine cooling water flowing to the EGR cooler 21 is heated by the combustion heater 24, and the temperature difference between the exhaust gas guided to the EGR cooler 21 and the engine cooling water is large even when the engine is cold. Therefore, the EGR cooler 21 does not condense moisture in the exhaust gas, and the generation of sulfuric acid can be prevented to prevent corrosion of the exhaust gas recirculation pipe 20, the intake pipe 12, the engine 15, and the like.
[0020]
In the above-described embodiment, the heating means is the combustion heater 24. However, the exhaust gas recirculation device of the present invention is not limited to this, and may be, for example, an electric ceramic heater.
[0021]
【The invention's effect】
As described above in detail in the embodiment, according to the exhaust gas recirculation device of the first aspect of the present invention, the EGR valve and the EGR cooler are provided in the exhaust gas recirculation passage, and the engine coolant is led from the engine to the EGR cooler. A cooling water passage to be circulated is provided, and heating means for heating the engine cooling water upstream of the EGR cooler in the cooling water passage when the engine is cold, and the engine cooling by the heating means when the engine cooling water temperature is lower than the first cooling water temperature. Since the engine is provided with a control unit for heating the water and controlling the EGR valve to switch the exhaust gas to the intake passage when the engine coolant temperature is higher than the second coolant temperature lower than the first coolant temperature. During cooling, the cooling water in the cooling water passage is heated by the heating means, and the warming cooling water is sent to the EGR cooler. In addition, it circulates between the engine and promotes warm-up of the engine, so that exhaust gas is recirculated to the intake system at an early stage from the start of the engine to reduce nitrogen oxides. It is possible to improve the reduction efficiency of nitrogen oxides and the like, and even if the exhaust gas is led from the exhaust gas recirculation passage to the EGR cooler, the temperature difference between the cooling water and the exhaust gas is not large. Therefore, the heat exchange is performed properly, and corrosion due to sulfuric acid generated due to a large amount of black smoke and hydrocarbons due to deterioration of combustion and moisture condensation of exhaust gas can be prevented.
[0022]
According to the exhaust gas recirculation device of the second aspect of the present invention, the heating means cools to a temperature at which moisture in the exhaust gas does not condense when heat exchange between the exhaust gas and the cooling water is performed in the EGR cooler. Since the water is heated, the heating means is controlled according to the temperature of the engine cooling water, and the structure can be simplified.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an exhaust gas recirculation apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart of control by the exhaust gas recirculation device of the present embodiment.
FIG. 3 is a schematic view of a conventional exhaust gas recirculation device.
[Explanation of symbols]
12 Intake pipe (intake passage)
15 Engine 18 Exhaust pipe (exhaust passage)
20 Exhaust gas recirculation pipe (exhaust gas recirculation passage)
21 ERG valve 22 EGR cooler 23a, 23b Cooling water piping (cooling water passage)
24 Combustion heater (heating means)
25 Control unit

Claims (2)

排気ガスを吸気通路に還流させる排気ガス還流通路と、
前記排気ガス還流通路に設けられ排気ガスを吸気通路に環流させるか否かを選択的に切り換えるＥＧＲバルブと、
該排気ガス還流通路に設けられて排気ガスを冷却するＥＧＲクーラと、
前記エンジンから該ＥＧＲクーラに導かれてエンジン冷却水を循環する冷却水通路と、
エンジンの冷態時に前記冷却水通路における前記ＥＧＲクーラの上流側のエンジン冷却水を加熱する加熱手段と、
エンジン冷却水温が第１冷却水温よりも低い時に前記加熱手段によりエンジン冷加水を加熱し、エンジン冷却水温が第１冷却水温よりも低い第２冷却水温よりも高い時に前記ＥＧＲバルブを切り換えて排気ガスを吸気通路に環流させるべく制御を行うコントロールユニットと、を具えたことを特徴とする排気ガス還流装置。An exhaust gas recirculation passage for recirculating exhaust gas to the intake passage;
An EGR valve which is provided in the exhaust gas recirculation passage and selectively switches whether exhaust gas is circulated to the intake passage;
An EGR cooler provided in the exhaust gas recirculation passage for cooling the exhaust gas;
A cooling water passage which is led from the engine to the EGR cooler and circulates the engine cooling water;
Heating means for heating engine cooling water upstream of the EGR cooler in the cooling water passage when the engine is cold ;
When the engine cooling water temperature is lower than the first cooling water temperature, the engine cooling water is heated by the heating means, and when the engine cooling water temperature is higher than the second cooling water temperature lower than the first cooling water temperature, the EGR valve is switched to exhaust gas. An exhaust gas recirculation device comprising: a control unit that performs control to circulate the air in the intake passage . 請求項１記載の排気ガス還流装置において、
前記加熱手段は、前記ＥＧＲクーラ内で排気ガスと冷却水との熱交換が行われるときに該排気ガス中の水分が凝縮しない温度まで該冷却水を加熱することを特徴とする排気ガス還流装置。The exhaust gas recirculation device according to claim 1,
The heating means heats the cooling water to a temperature at which moisture in the exhaust gas does not condense when heat exchange between the exhaust gas and the cooling water is performed in the EGR cooler. .
JP29068797A 1997-10-23 1997-10-23 Exhaust gas recirculation device Expired - Fee Related JP3729994B2 (en)

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KR100391410B1 (en) * 2000-11-15 2003-07-16 기아자동차주식회사 Exhaust gas recirculation system
SE530583C2 (en) * 2006-11-29 2008-07-08 Scania Cv Ab Radiator arrangement of a vehicle
JP4561817B2 (en) 2007-12-04 2010-10-13 トヨタ自動車株式会社 Internal combustion engine
DE102008064015A1 (en) 2008-12-19 2010-07-01 Daimler Ag Waste heat recovery device for utilization of waste heat of internal combustion engine of motor vehicle, has working fluid circuit connected with coolant heat exchanger, and coolant circuit fluid coupled with engine cooling circuit
FR2943389A1 (en) * 2009-03-20 2010-09-24 Inst Francais Du Petrole Device for controlling circulation of exhaust gas of internal combustion engine e.g. auto-ignition diesel engine, has exhaust gas circulation circuit circulating gas from energy of exhaust collector toward intake splitter by channel
JP5742529B2 (en) * 2011-07-19 2015-07-01 トヨタ自動車株式会社 Exhaust gas recirculation device for internal combustion engine
JP2014009634A (en) * 2012-06-29 2014-01-20 Toyota Motor Corp Control device of cooling system
KR101583889B1 (en) 2013-12-20 2016-01-21 현대자동차주식회사 Oil temperature control apparatus and control method thereof
JP2018119423A (en) * 2017-01-23 2018-08-02 いすゞ自動車株式会社 Engine cooling system
JP6809300B2 (en) 2017-03-06 2021-01-06 株式会社デンソー Exhaust recirculation device

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