JP3618272B2 - Failure diagnosis device for fuel vapor purge system and fuel vapor purge system - Google Patents

Description

となる。燃料タンク１への燃料の給油時以外には圧力Ｐα＝Ｐβとなるため、

となる。
【００３９】
従って、燃料タンク１の圧力Ｐαがキャニスタ２の圧力Ｐγよりも所定圧力Ｐ０＝１．８９ｋＰａ（＝１４ｍｍＨｇ）以上低くなると、ダイヤフラム５ａが開放され、キャニスタ２から燃料タンク１へのバックパージが行われることとなる。例えば、エンジン運転状態において、タンク内圧が−１．８９ｋＰａ（＝−１４ｍｍＨｇ）よりも小さな値であれば、パージ制御弁１１を閉弁してキャニスタ２内に大気圧を導入することにより、差圧弁５が開弁することとなる。
【００４０】
燃料注入管３６の下部側先端部には絞り３６ａが形成されている。給油された燃料がこの絞り３６ａを通過すると、燃料注入管３６内部の燃料蒸気の流れ方向は給油口３６ｂから燃料タンク１側に流れる方向に規制される。従って、給油口３６ｂから燃料蒸気が外部に漏出することを防止できる。なお、燃料タンク１の上部と燃料注入管３６の上部とを連通させる循環ライン管３７が設けられており、給油時において燃料タンク１内の燃料蒸気を燃料注入管３６との間で循環させて円滑な注油を可能としている。
【００４１】
また、燃料タンク１の上部には燃料タンク１内の圧力を検出するための圧力センサ１ａが設けられている。本実施形態において、圧力センサ１ａは大気圧を基準とする相対圧力を検出するものが用いられている。圧力センサ１ａによる検出信号はパージ制御や故障診断制御を行っているＥＣＵ１０に出力されている。なお、ＥＣＵ１０へは吸気通路９に設けられたエアフローメータ９ｃ等の各種センサからの信号も出力されている。
【００４２】
更に、タンク内圧制御弁４内の正圧室４ｃからキャニスタ２の副室１７へは、バイパス通路４１が形成されている。このことにより、バイパス通路４１は、タンク内圧制御弁４内の正圧室４ｃ及び燃料蒸気導入通路３を介して燃料タンク１とキャニスタ２とを連絡している。このバイパス通路４１には、バイパス制御弁４２が配置されている。このバイパス制御弁４２は通常時には閉じられているが、故障診断時にＥＣＵ１０により後述するごとく制御されて、バイパス通路４１の開閉状態を調節している。このバイパス制御弁４２としては例えばＶＳＶ等が用いられる。
【００４３】
上記構成を備える燃料蒸気パージシステムは以下のように機能する。
燃料タンク１内において燃料が蒸発し、燃料タンク１の内圧が規定圧力値以上に増加すると、タンク内圧制御弁４が開弁する。すると、燃料蒸気導入通路３内には燃料タンク１からキャニスタ２に向かう燃料蒸気の流れが形成される。このため、燃料タンク１の燃料蒸気はタンク内圧制御弁４を介してキャニスタ２側に導入される。
【００４４】
燃料蒸気導入通路３を介してキャニスタ２内部に到達した燃料蒸気は、まず、主室１６側の吸着材層２０ａに充填された活性炭吸着材１９ａによって燃料成分が捕集される。続いて、燃料蒸気は吸着材層２０ａを抜けて拡散室２１に達する。さらに、燃料蒸気は拡散室２１を通過して副室１７に導入され、副室１７側の吸着材層２０ｂにおいて、主室１６側の吸着材層２０ａで捕集しきれなかった燃料成分が捕集される。このように燃料蒸気はキャニスタ２内部をＵ字状の移動経路に沿って流れるため、吸着材層２０ａ，２０ｂの活性炭吸着材１９ａ，１９ｂに接触する時間が長くなり燃料成分が効果的に捕集される。このとき、図３（ａ）に示すように、蒸気ガイド４０によって燃料蒸気の流れが規制され、蒸気ガイド４０よりもパージ通路８側の吸着材層２０ａ領域への燃料蒸気の吸着量は少なくなる。
【００４５】
そして、燃料成分の大部分が吸着材層２０ａ，２０ｂの活性炭吸着材１９ａ，１９ｂによって捕集された気体は大気開放弁１２を開弁するとともに、大気排出ポート２６を通じて外部に放出される。この時、大気導入弁１３の負圧室１３ｂの内圧は大気圧室１３ｄの内圧より大きい正圧となっているため、大気導入弁１３は開弁しない。従って、大気導入弁１３を介して、大気導入通路２７から燃料蒸気が外部に漏出することはない。
【００４６】
次に、キャニスタ２内に捕集された燃料成分は以下のようにして吸気通路９に供給される。エンジンが運転されているとパージ通路８のサージタンク９ａ側開口部近傍は負圧に転じるため、ＥＣＵ１０の制御信号によりパージ制御弁１１が開放駆動される毎に、大気導入弁１３が開弁しパージ通路８の内部にはキャニスタ２側からサージタンク９ａ側へ向かう燃料蒸気の流れが形成される。
【００４７】
従って、キャニスタ２内部は負圧となり、大気導入通路２７を通してキャニスタ２内部に副室１７側から空気が導入される。そして、活性炭吸着材１９ａ，１９ｂに吸着されている燃料成分はその空気により離脱され、空気中に吸収される。このとき、図３（ｂ）に示すように、蒸気ガイド４０によって燃料蒸気の流れが規制され、蒸気ガイド４０よりもベーパ導入ポート２２側の吸着材層２０ａ領域からの燃料蒸気の離脱量は少なくなる。
【００４８】
このようにして導入された空気により燃料蒸気はパージ通路８内に導かれ、パージ制御弁１１を介してサージタンク９ａ内に放出される。サージタンク９ａ内において、燃料蒸気はエアクリーナ９ｂ、エアフローメータ９ｃ及びスロットルバルブ９ｄを通過した吸入空気と混合され、シリンダ（図示略）内に供給される。そして、吸入空気と混合された燃料蒸気は、燃料タンク１内の燃料ポンプ３８を介して燃料噴射弁３９から吐出された燃料とともに、シリンダ内において燃焼される。
【００４９】
また、パージ実行中において、燃料タンク１の内圧が大気圧よりも所定圧力Ｐ０以上低い状態において、パージ制御弁１１を一時的に閉弁すると、キャニスタ２内の圧力Ｐγはほぼ大気圧になるため、差圧弁５が開弁する。このため、図３（ｃ）に示すように、ブリーザ通路７の内部にはキャニスタ２側から燃料タンク１側へ向かう燃料蒸気の流れが形成され、蒸気ガイド４０よりもベーパ導入ポート２２側の吸着材層２０ａ領域からの燃料蒸気が離脱されて燃料タンク１へバックパージされることとなる。そのため、次の給油時において給油エミッションの悪化を抑制することができる。
【００５０】
一方、長時間の駐車等により、燃料タンク１が冷却され、燃料タンク１内の燃料蒸気の発生が止まり、燃料タンク１内部の圧力が相対的にキャニスタ２内部より低くなった場合には、タンク内圧制御弁４の正圧室４ｃの圧力は負圧となる。従って、ベーパリリーフ弁２３のチェックボールが上方に移動し、ベーパリリーフ弁２３が開放される。このため、キャニスタ２内の燃料蒸気は燃料蒸気導入通路３を通じて燃料タンク１に戻される。
【００５１】
また、この故障診断装置では、燃料タンク１の内部、燃料蒸気導入通路３、ブリーザ通路７、キャニスタ２の内部、及びパージ通路８といった燃料蒸気が導入される部位により構成される経路（以下、これらを併せて「パージ経路」と称する）の穴開きや配管の外れ等に起因する漏れ異常の有無をその診断対象とするとともに、パージ経路に設けられた各種バルブの故障を診断対象としている。パージ経路の漏れ異常の診断方法として具体的には、燃料蒸気導入通路内を所定の負圧下で密閉した後の同経路内の圧力挙動に基づいて、同経路における漏れ異常の有無を診断している。
【００５２】
以下、こうした故障診断装置による漏れ異常の故障診断の実行手順について図６に示すタイミングチャートを参照して説明する。
この故障診断は、タンク内圧が安定していること、エンジンの始動時から所定時間が経過していないこと、圧力センサ１ａに異常がないこと等の条件に加え、パージ処理が実行されていること、即ちパージ制御弁１１が運転状態に基づく所定開度で開弁されていること、といった各前提条件が全て成立しているときに実行される。
【００５３】
そして、こうした前提条件が満たされると、まず、ＥＣＵ１０により圧力封鎖弁２７ａが閉駆動され（時刻ｔ１０）、吸気通路９の負圧がパージ経路内に導入される。その結果、パージ経路内の圧力（＝タンク内圧）は徐々に低下するようになる（時刻ｔ１０〜ｔ２０）。
【００５４】
次に、タンク内圧が目標負圧ＰＴに達すると（時刻ｔ２０）、ＥＣＵ１０によりパージ制御弁１１が強制的に閉じられる。その結果、パージ経路内は密閉された状態になる。尚、負圧の導入を開始してから所定時間が経過してもタンク内圧が上記目標負圧ＰＴにまで低下しない場合には、パージ経路内に比較的大きな漏れが発生していると診断される。
【００５５】
上記のようにパージ経路内が低圧（負圧）下に置かれた状態で密閉されると、タンク内圧は、上記所定負圧ＰＴ以下にまで一旦低下するものの、同経路内の燃料（例えば燃料タンク１内の燃料やキャニスタ２の吸着材に吸着されている燃料）が蒸発するのに伴って徐々に上昇し始める（時刻ｔ２１以降）。そして、故障診断、すなわちパージ経路における漏れ異常の有無の判定は、このときのタンク内圧の上昇速度に基づいて行われる。
【００５６】
即ち、
［正常判定］
タンク内圧の上昇速度が所定値（正常判定値）未満である場合には、タンク内圧はパージ経路内における燃料の蒸発によってのみ上昇しており、同経路に漏れ異常は無いと判定される。
［異常判定］
タンク内圧の上昇速度が所定値（異常判定値）以上である場合には、タンク内圧は同経路内における燃料の上昇に加えて、更に同経路への大気の流入によって上昇しており、同経路に漏れ異常が有ると判定される。
［判定保留］
タンク内圧の上昇速度が上記正常判定値以上であって異常判定値未満である場合には、漏れ異常の有無を確実に判定することが困難であるため、その判定が一旦保留される。
といった判定がなされる。
【００５７】
次に、ＥＣＵ１０が実行するパージ制御及びバルブの故障診断処理を図４〜図５に従って説明する。なお、以下の故障診断処理において、燃料タンク内圧は、大気圧を基準とする相対圧力である。
【００５８】
本診断処理はＥＣＵ１０の電源オン後に必要な初期設定が行われ、例えば、圧力センサ１ａやその他のセンサに異常が無く、エンジンが運転を開始してから、ある程度の時間が経過して運転が安定した場合に故障診断処理実行条件は成立する。
【００５９】
前述したように、エンジンの運転が安定すると、まず、ステップ１０２において、エンジン冷却水温ＴＨＷが所定温度Ａ℃（例えば７５℃）以上か否かを判定する。エンジン冷却水温ＴＨＷがＡ℃未満であると判定すると、ステップ１３０に処理を移行する。エンジン冷却水温ＴＨＷがＡ℃以上であると判定すると、ステップ１０４に進む。
【００６０】
ステップ１３０において、タンク内圧が−ＰＡ（例えばＰＡ＝２．６７ｋＰａ＝２０ｍｍＨｇ）未満か否かを判定する。タンク内圧が−ＰＡ以上であると判定すると本ルーチンを一旦終了する。タンク内圧が−ＰＡ未満であると判定すると、次のステップ１３２において、圧力封鎖弁閉異常、又はパージ制御弁及びバイパス制御弁開異常であると診断し、本ルーチンを一旦終了する。これは、パージの開始前にタンク内圧が−ＰＡ未満になる条件はキャニスタ２内が負圧になる場合である。キャニスタ２内が負圧になる故障条件は、パージ制御弁１１が開異常であるとともに、バイパス制御弁４２が開異常の場合に、直接燃料タンク１内にキャニスタ２の負圧が伝わっているので、タンク内圧が負圧になる。また、パージ制御弁１１が正常であっても燃料消費量が多いためにタンク内圧の負圧が大きくなる場合があるが、このとき圧力封鎖弁２７ａが閉異常のときキャニスタ２内が負圧になる。
【００６１】
また、ステップ１０４ではパージ条件成立か否かを判定する。パージ条件が成立していないと判定すると本ルーチンを一旦終了し、パージ条件が成立していると判定するとステップ１０６に進む。
【００６２】
ステップ１０６においてパージ経路内への負圧導入中か否かを判定し、負圧導入中でないと判定するとステップ１０８に進み、負圧導入中であると判定するとステップ１６０の負圧導入漏れ検出ルーチンに進む。
【００６３】
ステップ１０８において、タンク内圧が−ＰＢ（例えばＰＢ＝３．３４ｋＰａ＝２５ｍｍＨｇ）未満か否かを判定する。タンク内圧が−ＰＢ以上であると判定するとステップ１４０に進み、タンク内圧が−ＰＢ未満であると判定するとステップ１１０においてパージ制御弁１１を閉弁してパージを強制的に停止する。
【００６４】
ステップ１４０において、パージ強制停止フラグは１である、すなわちパージ制御弁１１が閉弁状態であるか否かを判定し、肯定判定の場合にはステップ１１４に移行し、否定判定の場合にはステップ１４２に進んで通常パージ制御を実行する。
【００６５】
そしてステップ１１２において、パージ強制停止後ｔ秒経過したか否かを判定し、ｔ秒経過していないと判定すると本ルーチンを一旦終了する。このステップ１１２でパージ強制停止後ｔ秒経過したと判定すると、パージ強制停止フラグを１に設定してステップ１１４に移行する。
【００６６】
ステップ１１４において、タンク内圧が−ＰＡ（例えばＰＡ＝２．６７ｋＰａ＝２０ｍｍＨｇ）未満か否かを判定する。タンク内圧が−ＰＡ以上であると判定するとステップ１５０に移行し、タンク内圧が−ＰＡ未満であると判定すると、次のステップ１１６において、パージ制御弁開異常、又は圧力封鎖弁閉異常、又はバイパス制御弁開及び圧力封鎖弁閉異常であると診断する。これは、パージ実行中にパージ制御弁を閉弁してもタンク内圧が大気側に上昇しない場合にはキャニスタ２内の負圧が維持されるので、パージ制御弁１１が開異常であるか、圧力封鎖弁２７ａが閉異常のためにパージ経路内に大気が導入されないか、バイパス制御弁４２が開異常のためにキャニスタ２内の負圧が直接燃料タンク１内に伝わっているかであることによる。
【００６７】
また、ステップ１１６の処理の後、ステップ１１８において強制パージ停止フラグを０に設定してパージを再開する。
また、ステップ１５０では、タンク内圧が−ＰＣ（例えばＰＣ＝１．３３ｋＰａ＝１０ｍｍＨｇ）未満か否かを判定する。タンク内圧が−ＰＣ以上であると判定するとステップ１５４に移行し、タンク内圧が−ＰＣ未満であると判定すると、ステップ１５２に進む。
【００６８】
ステップ１５２において、パージ制御弁開閉正常、圧力封鎖弁開正常、バイパス制御弁閉正常、差圧弁正常、及びタンクの１．０ｍｍ穴正常であると又はバイパス制御弁開及び圧力封鎖弁閉異常であると診断する。これは、パージ強制停止によってタンク内圧が−ＰＢ（＝−３．３４ｋＰａ）未満の状態から−ＰＣ（＝−１．３３ｋＰａ）未満の状態に変化することから、パージ制御弁１１の開から閉への切り換えによって圧力変化が発生しているので、パージ制御弁１１が開閉ともに正常となる。また、タンク内圧が−ＰＢ（＝−３．３４ｋＰａ）未満の状態から−ＰＣ（＝−１．３３ｋＰａ）未満に上昇することにより圧力封鎖弁２７ａが開正常となって大気が導入され、差圧弁５が正常であり、バイパス制御弁４２が閉正常となる。さらに、差圧弁５が正常であり、バイパス制御弁４２が閉正常であることから、所定時間経過後にタンク内圧が−ＰＣ付近に維持されていればタンクの１．０ｍｍ穴がないことを判定することができる。従って、パージ経路への負圧導入漏れ検出において１．０ｍｍ穴異常が検出されると、キャニスタ２側での１．０ｍｍ穴有りを検出することができる。
【００６９】
ステップ１５０でタンク内圧が−ＰＣ以上であると判定されたとき、ステップ１５４では、パージ制御弁開閉正常、圧力封鎖弁開正常、及びバイパス制御弁開異常であると診断する。これは、パージ強制停止によってタンク内圧が−ＰＢ（＝−３．３４ｋＰａ）未満の状態から−ＰＣ（＝−１．３３ｋＰａ）以上の状態に変化することから、パージ制御弁１１の開から閉への切り換えによって圧力変化が発生しているので、パージ制御弁１１が開閉ともに正常となる。また、タンク内圧が−ＰＣ（＝−１．３３ｋＰａ）以上に上昇することにより圧力封鎖弁２７ａが開正常であり、このときタンク内圧が−ＰＣ以上になることから差圧弁５が開異常であるか、バイパス制御弁４２が閉異常となる。
【００７０】
以上説明した態様をもってバルブ故障診断が実行される本実施形態の燃料蒸気パージシステムによれば、
（１）エンジン運転状態において、パージ実行中にパージ制御弁１１を一時閉弁してパージ強制停止し、そのときのタンク内圧の変化状態を検出することのみによって、パージ制御弁１１、圧力封鎖弁２７ａ、バイパス制御弁４２、及び差圧弁５等のバルブ故障を診断することができる。従って、負圧導入による故障診断はパージ経路の漏れ故障診断だけで済み、故障診断に要する時間を短縮化することができ、よって早期にパージを開始してパージ効率を向上することができる。
【００７１】
（２）また、パージ実行中に燃料タンク１の内圧が所定圧力Ｐ０未満の場合にパージ制御弁１１を一時的に閉弁することにより、差圧弁５を開弁することができ、よってキャニスタ２の蒸気ガイド４０よりもベーパ導入ポート２２側の吸着材層２０ａ領域に残留している燃料蒸気を燃料タンク１へバックパージすることができる。このため、次の給油時においてキャニスタ２から大気への給油エミッションの悪化を抑制することができる。
【００７２】
（第２実施形態）
次に、本発明にかかる燃料蒸気パージシステムの故障診断装置の第２実施形態について、上記第１実施形態との相違点を中心に説明する。なお、この第２実施形態にかかる故障診断装置は、先の第１実施形態で説明したものと同様の構成を有したものを想定しているため、その構成についての説明は省略する。
【００７３】
第１実施形態の故障診断装置では、キャニスタ２から燃料タンク１へバックパージを利用したタンク負圧が大きい条件でパージカットした時のバルブ故障診断について述べた。本実施形態では、タンク内圧が大気圧よりも所定値以上高い若しくはタンク内圧が大気圧よりも所定値以上低い場合に、パージカットに合わせてバルブ故障診断を実施するようにしたものである。
【００７４】
図７，８は、パージカット時のバルブ故障診断処理の実行手順を示すフローチャートであり、このフローチャートに示す一連の処理は、所定時間毎（例えば６５ｍｓ毎）の割り込み処理としてＥＣＵ１０により実行される。
【００７５】
この処理に際しては、先ず、ステップ２０２において、パージカットフラグが１であるか否かに基づいて、パージ制御弁１１が閉弁されているか否かを判断する。このステップ２０２で、パージカットフラグが１すなわちパージ制御弁１１が閉弁されているとステップ２０４に進み、パージカットフラグが０すなわちパージ制御弁１１が開弁されているとステップ２５０の通常パージ制御ルーチンに進む。
【００７６】
ステップ２０４において、パージカット時診断完了フラグが０であるか否かに基づいて、診断が未完了であるか否かを判定する。このステップ２０４で、パージカット時診断完了フラグが０すなわち診断未完了であると判定するとステップ２０６に進み、パージカット時診断完了フラグが１すなわち診断完了済みであると判定されるとステップ２５０の通常パージ制御ルーチンに進む。
【００７７】
ステップ２０６において、バイパス制御弁４２は閉弁しているか否かを判定する。バイパス制御弁４２が開弁していると判定するとステップ２１２に進み、バイパス制御弁４２が閉弁していると判定するとステップ２０８に進む。
【００７８】
ステップ２０８において、タンク内圧の絶対値が所定圧力Ｐ１（Ｐ１＞０）以上か否かを判定する。タンク内圧絶対値がＰ１以下であると判定すると本ルーチンを一旦終了し、タンク内圧絶対値がＰ１より大きいと判定すると、ステップ２１０に進んでバイパス制御弁４２を開弁させる。
【００７９】
そして、次のステップ２１２において、バイパス制御弁開弁後ｔ秒経過したか否かを判定し、ｔ秒経過していないと判定すると本ルーチンを一旦終了する。このステップ２１２でバイパス制御弁開弁後ｔ秒経過したと判定すると、ステップ２１４に進む。
【００８０】
ステップ２１４において、タンク内圧絶対値が所定圧力Ｐ２（Ｐ１＞Ｐ２＞０）未満か否かを判定する。タンク内圧絶対値がＰ２以上であると判定するとステップ２２０に移行し、タンク内圧絶対値がＰ２未満であると判定すると、次のステップ２１６において、パージ制御弁閉正常、パージ制御弁閉正常、及び圧力封鎖弁開正常であると診断する。これは、パージ実行中にパージ制御弁１１の閉弁に合わせてバイパス制御弁４２を閉から開に切り換えることにより、タンク内圧が大気に近づくことにより、バイパス制御弁開閉正常、パージ制御弁閉正常、及び圧力封鎖弁開正常を判断することができることによる。
【００８１】
また、ステップ２１６の処理の後、ステップ２１８においてパージカット時診断完了フラグを０に設定してパージを再開する。
また、ステップ２２０では、タンク内圧が−Ｐ１未満か否かを判定する。タンク内圧が−Ｐ１以上であると判定するとステップ２２４に移行し、タンク内圧が−Ｐ１未満であると判定すると、ステップ２２２に進む。ステップ２２２において、パージ制御弁開異常であると診断し、この後ステップ２１８に進む。
【００８２】
ステップ２２０でタンク内圧が−Ｐ１以上であると判定されると、ステップ２２４では、タンク内圧がＰ１より大きいか否かを判定する。タンク内圧がＰ１以下であると判定すると本ルーチンを一旦終了し、タンク内圧がＰ１より大きいと判定するとステップ２２６に進む。ステップ２２６において、バイパス制御弁閉異常であると診断し、この後ステップ２１８に進む。
【００８３】
以上説明した態様をもってバルブ故障診断が実行される本実施形態の燃料蒸気パージシステムによれば、
（１）負圧導入漏れ診断における負圧導入完了時点において、パージ制御弁開正常、圧力封鎖弁閉正常を判断することができ、従って、負圧導入による故障診断はパージ経路の漏れ故障診断だけで済み、故障診断に要する時間を短縮化することができ、よって早期にパージを開始してパージ効率を向上することができる。
【００８４】
（２）また、本実施形態ではパージ実行中に強制的にパージカットを行うのではなく、車両の走行状態にかかるパージカット時を利用してバルブ故障診断を行うことができるので、走行時のパージ流量を低下させることがない。
【００８５】
なお、上記各実施形態は、以下のようにその構成を変更して実施することもできる。
・ 上記各実施形態では、燃料蒸気パージシステムとして燃料タンク１とキャニスタ２とをバイパス制御弁４２を備えたバイパス通路４１により連通するタイプのものに具体化したが、これに代えて燃料タンクとキャニスタとをオリフィスを連通するタイプの燃料蒸気パージシステムに具体化してもよい。
【００８６】
・ 上記各実施形態における差圧弁５の開弁圧力は必要に応じて任意の値に変更することができる。
次に、上記各実施形態から把握できる他の技術的思想を、以下に記載する。
【００８７】
・ 請求項１に記載の燃料蒸気パージシステムにおいて、前記第１及び第２のポートが管路により互いに接続され、前記管路には、前記閉鎖空間の気密性に係る診断が行われるときに診断用の圧力が導入される一つの導入ポートが設けられ、その導入ポートと前記第２のポートとの間には、前記導入ポートから導入された診断用の圧力が前記第２のポートへ導入されることを許容し、前記第２のポートに作用する圧力が前記導入ポートを通じて外部へ導出されることを阻止するための逆止弁を設けた燃料蒸気パージシステム。
【図面の簡単な説明】
【図１】第１実施形態の燃料蒸気パージシステム及びその故障診断装置を示す概略構成図。
【図２】差圧弁を示す概略断面図。
【図３】キャニスタ内の燃料蒸気の流れを示す説明図。
【図４】第１実施形態におけるパージ制御及びバルブ故障診断処理の処理手順を示すフローチャート。
【図５】第１実施形態におけるパージ制御及びバルブ故障診断処理の処理手順を示すフローチャート。
【図６】故障診断装置による故障診断の手順を説明するためのタイミングチャート。
【図７】第２実施形態におけるパージカット時のバルブ故障診断処理の処理手順を示すフローチャート。
【図８】第２実施形態におけるパージカット時のバルブ故障診断処理の処理手順を示すフローチャート。
【符号の説明】
１…燃料タンク、１ａ…圧力センサ、２…キャニスタ、３…燃料蒸気導入通路、５…差圧弁、７…ブリーザ通路、８…パージ通路、１０…ＥＣＵ、１１…パージ制御弁、２７ａ…圧力封鎖弁、４２…バイパス制御弁。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a failure diagnosis apparatus and a fuel vapor purge system for a fuel vapor purge system that purges and processes fuel vapor generated in a fuel tank into an intake system of an internal combustion engine.
[0002]
[Prior art]
In order to prevent the fuel evaporated in the fuel tank from being released into the atmosphere, the fuel vapor is once adsorbed to the adsorbent in the canister, and the fuel adsorbed while the vehicle is running while introducing the atmosphere into the canister. A fuel vapor purge system that purges and combusts in an intake system via a purge passage is known. In an internal combustion engine equipped with such a fuel vapor purge system, if for some reason the pipe is pierced or disconnected, the fuel vapor leaks and is released from the canister or fuel tank to the atmosphere. .
[0003]
Therefore, it is necessary to automatically diagnose whether or not there is a leakage abnormality in such a fuel vapor purge system.
For this reason, conventionally, after providing a differential pressure between the inside and the outside of the fuel vapor purge system, a system for diagnosing a leakage abnormality by detecting the behavior of the internal pressure has been proposed. For example, after introducing the negative pressure of the intake system of the internal combustion engine into the fuel vapor purge system, the fuel vapor purge system is sealed by closing the atmosphere introduction passage and the purge passage with a valve, and then the fuel vapor purge system It measures the change in internal pressure.
[0004]
However, in such a fuel vapor purge system, it is conceivable that not only a leakage failure but also a failure of a valve provided in the atmosphere introduction passage and the purge passage with respect to the fuel vapor purge system described above occurs. If such a valve failure occurs, purging may not be performed properly, or fuel may be discharged from the canister's atmosphere inlet to the atmosphere. Such a valve failure has a different influence on the internal pressure of the fuel vapor purge system, and the above-described leakage failure diagnosis performed for detecting the hole cannot serve as a valve failure diagnosis.
[0005]
[Problems to be solved by the invention]
However, in this way, in a system that performs two types of failure diagnosis, leakage failure diagnosis and valve failure diagnosis, if all failure diagnosis is not completed at one time, the intake system until all failure diagnosis is completed or stopped The introduction of negative pressure into the fuel vapor purge system, purge stop and purge permission are repeated, the time required for failure diagnosis becomes longer, the purge start timing is delayed, and the purge efficiency is lowered.
[0006]
As a failure diagnosis device for the fuel vapor purge system, when the purge control valve provided in the purge passage and the control valve provided between the canister and the fuel tank are both open, it is provided in the air introduction passage of the canister. Japanese Patent Laid-Open No. 5-19583 proposes a method for diagnosing a malfunction of a control valve.
[0007]
The present invention has been made in view of such circumstances, and an object of the present invention is to shorten the time required for failure diagnosis of the fuel vapor purge system and to start the purge at an early stage to improve the purge efficiency. An object of the present invention is to provide a failure diagnosis device for a vapor purge system and a fuel vapor purge system.
[0008]
[Means for Solving the Problems]
In the following, means for achieving the above-mentioned purpose and the effects thereof are described..
[0010]
Claim1According to the invention described in, the fuel vapor generated in the fuel tank is collected in the canister, and is opened based on the difference between the internal pressure of the fuel tank and the internal pressure on the canister side, and allows the inflow of the fuel vapor from the fuel tank to the canister It is equipped with a differential pressure valve, a purge control valve that opens and closes the purge passage, and a pressure block valve that opens and closes the atmosphere introduction port. The purge control valve and the pressure block valve are opened and air is introduced into the canister and collected in the canister. A fuel vapor purge system for purging the fuel vapor to the intake passage of the internal combustion engine via the purge passage, and a pressure difference between the internal pressure and the external pressure of the purge passage to close the pressure block valve and the purge control valve And a diagnostic means for diagnosing whether or not there is a leakage abnormality in the purge path based on the change state of the internal pressure measured by sealing the purge path. The diagnosis means diagnoses a failure of the purge control valve, the pressure blocking valve and the differential pressure valve based on a change state of the internal pressure of the purge path when the purge control valve is closed during the execution of the purge. Is the gist.
[0011]
According to the above configuration, in the operation state of the internal combustion engine, the purge control valve is closed during the purge execution to stop the purge, and only by detecting the change state of the tank internal pressure at that time, the purge control valve, It is possible to diagnose valve failure of the pressure block valve and the differential pressure valve. Therefore, the failure diagnosis by introducing the negative pressure need only be a leakage failure diagnosis of the purge path, and the time required for the failure diagnosis can be shortened. Therefore, the purge can be started early and the purge efficiency can be improved.
[0012]
Claim2The invention described in claim 11In the fuel vapor purge system failure diagnosis apparatus according to claim 1, the differential pressure valve is opened when the internal pressure of the fuel tank is lower than the internal pressure of the canister by a predetermined value or more.
[0014]
According to the above configuration, the differential pressure valve can be opened by temporarily closing the purge control valve when the internal pressure of the fuel tank is lower than the predetermined pressure during the purge execution, and thus the residual pressure in the canister The fuel vapor can be back purged into the fuel tank. For this reason, at the time of the next refueling, deterioration of the refueling emission from the canister to the atmosphere can be suppressed.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
A fuel vapor purge system according to a first embodiment embodying the present invention will be described below with reference to FIGS.
[0016]
FIG. 1 is a schematic explanatory diagram showing the entire fuel vapor purge system according to this embodiment. The fuel vapor purge system is attached to a gasoline engine installed in an automobile.
[0017]
One end of a fuel vapor introduction passage 3 for introducing fuel vapor generated inside the fuel tank 1 of the gasoline engine into the canister 2 is opened and connected via a float 3a. The other end of the fuel vapor introduction passage 3 is connected to the canister 2 via a tank internal pressure control valve 4 provided in the upper portion of the canister 2. The tank internal pressure control valve 4 is opened when the internal pressure of the fuel tank 1 exceeds a specified value.
[0018]
In addition, the fuel tank 1 is provided with a differential pressure valve 5 that opens during refueling. The differential pressure valve 5 is connected to the canister 2 by a breather passage 7. Accordingly, when the differential pressure valve 5 is opened during refueling, the fuel vapor in the fuel tank 1 is introduced into the canister 2 through the breather passage 7.
[0019]
The inside of the canister 2 is communicated with a surge tank 9 a forming a part of the intake passage 9 by the purge passage 8. A purge control valve 11 is provided in the purge passage 8. The purge control valve 11 is driven to open and close by a drive circuit 11a based on a control signal from an ECU (electronic control unit) 10 configured as a microcomputer.
[0020]
For example, the purge control valve 11 adjusts the amount of fuel supplied to the intake passage 9 from the canister 2 side by purge in the purge control, and shuts off / opens the purge passage 8 in the failure diagnosis control. As the purge control valve 11, for example, a vacuum switching valve (VSV) or the like is used.
[0021]
The interior of the canister 2 is divided into two chambers by a partition plate 15 extending in the vertical direction. The main chamber 16 is located below the tank internal pressure control valve 4, and the air volume is located below the atmospheric control valve 14. A sub chamber 17 smaller than the chamber 16 is formed. Air layers 18a and 18b are formed above the main chamber 16 and the sub chamber 17, respectively, and adsorbent layers 20a and 20b filled with activated carbon adsorbents 19a and 19b are formed below the air layers 18a and 18b, respectively. Has been. A steam guide 40 is provided in the main chamber 16 so as to immerse into the activated carbon adsorbent 19a from the ceiling, and the steam guide 40 is a direct purge passage when fuel vapor is introduced from the fuel tank 1 into the canister 2. 8 is prevented.
[0022]
Filters 20c and 20d are provided above and below the adsorbent layers 20a and 20b, and the activated carbon adsorbents 19a and 19b are filled between the filters 20c and 20d. A space below the filter 20d is a diffusion chamber 21, and the diffusion chamber 21 communicates the main chamber 16 and the sub chamber 17.
[0023]
A vapor introduction port 22 for introducing the fuel vapor generated in the fuel tank 1 into the canister 2 is formed on the end face of the canister 2 on the side where the main chamber 16 is located. In addition, a check ball type vapor ripple valve 23 is provided in the vicinity of the vapor introduction port 22 for venting when the inside of the fuel tank 1 becomes negative pressure.
[0024]
The tank internal pressure control valve 4 is disposed on the same end surface of the canister 2 so as to cover the vapor introduction port 22. The tank internal pressure control valve 4 is provided with a diaphragm 4a, and the diaphragm 4a can close the front end opening of the vapor introduction port 22. Further, the inside of the tank internal pressure control valve 4 is divided into two pressure chambers by a diaphragm 4a, a back pressure chamber 4b is formed on one side of the diaphragm 4a, and a positive pressure chamber 4c is formed on the other side. Yes. In addition, an air release port 24 that maintains the inside of the back pressure chamber 4b at atmospheric pressure is provided on the side surface of the back pressure chamber 4b. Further, the inside of the positive pressure chamber 4 c communicates with the inside of the fuel tank 1 through the fuel vapor introduction passage 3.
[0025]
Since the diaphragm 4a is pressed toward the tip opening side of the vapor introduction port 22 by the urging force of the spring 4d provided in the back pressure chamber 4b, the tank internal pressure control is performed until the internal pressure of the fuel tank 1 becomes a specified pressure or more. The valve 4 is kept closed.
[0026]
One end of the breather passage 7 is connected to the upper surface of the canister 2 above the main chamber 16. A purge passage 8 is connected to the opposite side of the vapor introduction port 22 across the steam guide 40 on the left side of the opening position of the breather passage 7 in the figure.
[0027]
In particular, when the purge control valve 11 is in an open state and a pressure lower than the atmospheric pressure is introduced into the canister 2, the space in the purge passage 8 is sequentially changed into the main chamber 16 → the tank internal pressure control valve. 4 → fuel vapor introduction passage 3 → fuel tank 1 is communicated. Further, since the space in the breather passage 7 is also originally communicated with the main chamber 16, the same space as the purge passage 8 is shared. Hereinafter, in the present specification, a pressure lower than the atmospheric pressure is referred to as a negative pressure, and a pressure higher than the atmospheric pressure is referred to as a positive pressure.
[0028]
As described above, the common space in the fuel vapor purge system that communicates with each other in a state where the negative pressure is introduced into the canister 2 becomes the purge path. The failure diagnosis device for the fuel vapor purge system according to the present embodiment diagnoses the presence or absence of the failure by determining the presence or absence of leakage in the purge path.
[0029]
Further, a ventilation port 25 is formed on the upper surface of the canister 2 above the sub chamber 17. The air control valve 14 is formed by disposing the air release valve 12 and the air introduction valve 13 so as to face the left and right in the drawing. An atmospheric pressure chamber 12 b is formed on the left side of the diaphragm 12 a provided in the atmosphere release valve 12, and a negative pressure chamber 13 b as a pressure chamber is formed on the right side of the diaphragm 13 a provided in the atmosphere introduction valve 13. Yes. A space sandwiched between these two diaphragms 12 a and 13 a is partitioned into two pressure chambers by a partition wall 28. One of the pressure chambers is a positive pressure chamber 12 d of the atmosphere release valve 12, and the other is an atmospheric pressure chamber 13 d of the atmosphere introduction valve 13.
[0030]
A pressure port 28a is formed in a part of the partition wall 28, and a front end opening of the partition wall 28 can be closed by a diaphragm 13a. An atmospheric air introduction passage 27 communicates with the atmospheric pressure chamber 13d. And since the diaphragm 13a is pressed by the urging | biasing force of the spring 13c arrange | positioned at the negative pressure chamber 13b at the front-end | tip opening part side of the pressure port 28a, the air introduction valve 13 is a valve closing state. A pressure blocking valve 27 a is arranged in the middle part of the air introduction passage 27. The pressure block valve 27a is normally opened, but is opened and closed by the ECU 10 during failure diagnosis as will be described later. For example, VSV or the like is used as the pressure sealing valve 27a.
[0031]
Further, the negative pressure chamber 13b is connected to the main chamber 16 through the communication passage 30, and pressure generated in the surge tank 9a of the intake passage 9 is introduced into the negative pressure chamber 13b. That is, when purging is performed, the negative pressure generated in the surge tank 9a with the intake of the engine is introduced into the negative pressure chamber 13b, and the negative pressure in the negative pressure chamber 13b becomes equal to or higher than the pressing force of the spring 13c. The diaphragm 13a is separated from the opening of the pressure port 28a and the atmosphere introduction valve 13 is opened. At the time of purge cut, the diaphragm 13a contacts the opening of the pressure port 28a and the atmosphere introduction valve 13 is closed.
[0032]
Therefore, when the adsorbed fuel in the canister 2 is purged (released) to the intake passage 9 side due to the negative pressure generated in the surge tank 9 a during engine operation, the outside air is passed through the air introduction passage 27 and the ventilation port 25. It can be introduced into the canister 2 from the sub chamber 17 side. By introducing the outside air, the fuel vapor adsorbed by the activated carbon adsorbents 19a and 19b in the main chamber 16 and the sub chamber 17 flows toward the purge passage 8 and is purged into the intake air flowing in the surge tank 9a. .
[0033]
In addition, in order to measure the amount of pressure change in the fuel tank 1, that is, the amount of fuel vapor generated, after the introduction of negative pressure during failure diagnosis during engine operation, the pressure block valve 25a is opened while the purge control valve 11 is closed. As a result, the pressure in the canister 2 and the fuel tank 1 is returned to the atmospheric pressure.
[0034]
An air release port 29 that communicates with the atmospheric pressure chamber 12b of the air release valve 12 is formed above the atmosphere control valve 14, and the atmospheric pressure chamber 12b is always at atmospheric pressure. The atmospheric control valve 14 is provided with an atmospheric discharge port 26 through which gas after the fuel component is collected in the canister 2 is led out. The front end opening of the air discharge port 26 can be blocked by the diaphragm 12a of the air release valve 12. The diaphragm 12a is pressed to the opening side of the air discharge port 26 by the urging force of the spring 12c disposed in the atmospheric pressure chamber 12b. For this reason, the air release valve 12 is held in the closed state until the internal pressure of the canister 2 becomes equal to or higher than the specified pressure.
[0035]
When pressure is applied from the breather passage 7 to the canister 2 during refueling, the pressure in the positive pressure chamber 12d of the air release valve 12 increases. When the pressure difference between the pressure in the positive pressure chamber 12d and the atmospheric pressure introduced from the atmosphere opening port 29 to the atmospheric pressure chamber 12b reaches a specified pressure difference, the atmosphere opening valve 12 is opened. As a result, the gas from which the fuel vapor has been removed through the main chamber 16 and the sub chamber 17 is discharged to the outside through the vent port 25 and the air discharge port 26.
[0036]
Next, a fitting insertion hole 31 is formed in the upper portion of the fuel tank 1, and a cylindrical breather pipe 32 forming a part of the breather passage 7 is inserted and fixed in the fitting insertion hole 31. A float valve 33 is formed below the breather pipe 32. A differential pressure valve 5 is disposed at the upper part of the fuel tank 1 so as to cover the upper end opening 32 a of the breather pipe 32.
[0037]
As shown in FIGS. 2 (a) and 2 (b), the inside of the differential pressure valve 5 is vertically divided by a diaphragm 5a. The first pressure chamber 5b is above the diaphragm 5a and the second pressure chamber 5c is below. Are formed respectively. The first pressure chamber 5b is communicated with an upper portion of a fuel injection pipe 36 provided in the fuel tank 1 by a pressure passage 34, and the pressure in the fuel tank 1 is introduced into the first and second pressure chambers 5b and 5c. Has been. The diaphragm 5a is pressed toward the upper end opening 7a side of the breather passage 7 introduced into the second pressure chamber 5c by the urging force of the spring 5d disposed in the first pressure chamber 5b. Thus, the upper end opening 7a of the breather passage 7 can be closed by the diaphragm 5a. In this embodiment, the pressures introduced into the first and second pressure chambers 5b and 5c are Pα and Pβ, the pressure introduced into the breather passage 7 is Pγ, and the pressure of the diaphragm 5a based on the pressing force of the spring 5d is Pδ. And The area of the diaphragm 5a on the first pressure chamber 5b side is S1, the area of the diaphragm 5a on the second pressure chamber 5c side is S2, and the area of the diaphragm 5a on the breather passage 7 side is S3. Then, the force f in the direction to close the diaphragm 5a is
f = Pα * S1 + Pδ * S1-Pβ * S2-Pγ * S3
It becomes. When the force f is a positive value, the diaphragm 5a is closed and the differential pressure valve 5 is closed. When the force f is a negative value, the diaphragm 5a is opened and the differential pressure valve 5 is opened. Become.
[0038]
In the present embodiment, for example, the area ratio of the areas S1, S2, and S3 is 7: 6: 1, and the pressure Pδ per unit area by the spring 5d is 0.27 kPa (= 2 mmHg). Therefore, the force f is

It becomes. Since pressure Pα = Pβ except when fuel is being supplied to the fuel tank 1,

It becomes.
[0039]
Therefore, when the pressure Pα of the fuel tank 1 becomes lower than the pressure Pγ of the canister 2 by a predetermined pressure P0 = 1.89 kPa (= 14 mmHg) or more, the diaphragm 5a is opened, and the back purge from the canister 2 to the fuel tank 1 is performed. It will be. For example, when the tank internal pressure is smaller than −1.89 kPa (= −14 mmHg) in the engine operating state, the purge control valve 11 is closed and the atmospheric pressure is introduced into the canister 2, whereby the differential pressure valve 5 will open.
[0040]
A throttle 36 a is formed at the lower end of the fuel injection pipe 36. When the refueled fuel passes through the throttle 36a, the flow direction of the fuel vapor inside the fuel injection pipe 36 is regulated to flow from the refueling port 36b to the fuel tank 1 side. Therefore, it is possible to prevent the fuel vapor from leaking from the fuel supply port 36b. A circulation line pipe 37 that connects the upper part of the fuel tank 1 and the upper part of the fuel injection pipe 36 is provided, and the fuel vapor in the fuel tank 1 is circulated between the fuel injection pipe 36 during refueling. Smooth lubrication is possible.
[0041]
In addition, a pressure sensor 1 a for detecting the pressure in the fuel tank 1 is provided on the upper portion of the fuel tank 1. In the present embodiment, a pressure sensor 1a that detects a relative pressure based on atmospheric pressure is used. A detection signal from the pressure sensor 1a is output to the ECU 10 that performs purge control and failure diagnosis control. Note that signals from various sensors such as an air flow meter 9 c provided in the intake passage 9 are also output to the ECU 10.
[0042]
Further, a bypass passage 41 is formed from the positive pressure chamber 4 c in the tank internal pressure control valve 4 to the sub chamber 17 of the canister 2. Thus, the bypass passage 41 communicates the fuel tank 1 and the canister 2 via the positive pressure chamber 4 c in the tank internal pressure control valve 4 and the fuel vapor introduction passage 3. A bypass control valve 42 is disposed in the bypass passage 41. The bypass control valve 42 is normally closed, but is controlled by the ECU 10 as described later at the time of failure diagnosis to adjust the open / close state of the bypass passage 41. As the bypass control valve 42, for example, VSV or the like is used.
[0043]
The fuel vapor purge system having the above-described configuration functions as follows.
When the fuel evaporates in the fuel tank 1 and the internal pressure of the fuel tank 1 increases to a specified pressure value or more, the tank internal pressure control valve 4 is opened. Then, a fuel vapor flow from the fuel tank 1 toward the canister 2 is formed in the fuel vapor introduction passage 3. For this reason, the fuel vapor in the fuel tank 1 is introduced to the canister 2 side via the tank internal pressure control valve 4.
[0044]
The fuel vapor that has reached the inside of the canister 2 through the fuel vapor introduction passage 3 is first collected by the activated carbon adsorbent 19a filled in the adsorbent layer 20a on the main chamber 16 side. Subsequently, the fuel vapor passes through the adsorbent layer 20 a and reaches the diffusion chamber 21. Further, the fuel vapor passes through the diffusion chamber 21 and is introduced into the sub chamber 17, and in the adsorbent layer 20 b on the sub chamber 17 side, fuel components that could not be collected by the adsorbent layer 20 a on the main chamber 16 side are trapped. Be collected. Since the fuel vapor flows in the canister 2 along the U-shaped movement path in this way, the time for contacting the activated carbon adsorbents 19a, 19b of the adsorbent layers 20a, 20b is increased, and the fuel components are effectively collected. Is done. At this time, as shown in FIG. 3A, the flow of the fuel vapor is regulated by the vapor guide 40, and the amount of adsorption of the fuel vapor to the adsorbent layer 20a region on the purge passage 8 side is smaller than that of the vapor guide 40. .
[0045]
The gas in which most of the fuel component is collected by the activated carbon adsorbents 19a and 19b of the adsorbent layers 20a and 20b opens the atmosphere release valve 12 and is released to the outside through the atmosphere discharge port 26. At this time, since the internal pressure of the negative pressure chamber 13b of the air introduction valve 13 is a positive pressure larger than the internal pressure of the atmospheric pressure chamber 13d, the air introduction valve 13 does not open. Therefore, the fuel vapor does not leak out from the atmosphere introduction passage 27 through the atmosphere introduction valve 13.
[0046]
Next, the fuel component collected in the canister 2 is supplied to the intake passage 9 as follows. When the engine is in operation, the pressure in the vicinity of the surge tank 9a side opening of the purge passage 8 changes to a negative pressure, so that the air introduction valve 13 is opened each time the purge control valve 11 is driven to open by the control signal of the ECU 10. Inside the purge passage 8, a flow of fuel vapor is formed from the canister 2 side toward the surge tank 9a.
[0047]
Accordingly, the inside of the canister 2 has a negative pressure, and air is introduced from the side of the sub chamber 17 into the canister 2 through the atmosphere introduction passage 27. The fuel component adsorbed on the activated carbon adsorbents 19a and 19b is released by the air and absorbed in the air. At this time, as shown in FIG. 3B, the flow of the fuel vapor is regulated by the steam guide 40, and the amount of fuel vapor released from the adsorbent layer 20 a region on the vapor introduction port 22 side is smaller than that of the steam guide 40. Become.
[0048]
The fuel vapor is guided into the purge passage 8 by the air thus introduced, and is discharged into the surge tank 9a through the purge control valve 11. In the surge tank 9a, the fuel vapor is mixed with the intake air that has passed through the air cleaner 9b, the air flow meter 9c, and the throttle valve 9d, and supplied to a cylinder (not shown). The fuel vapor mixed with the intake air is combusted in the cylinder together with the fuel discharged from the fuel injection valve 39 via the fuel pump 38 in the fuel tank 1.
[0049]
In addition, when the purge control valve 11 is temporarily closed while the purge is being executed and the internal pressure of the fuel tank 1 is lower than the atmospheric pressure by a predetermined pressure P0 or more, the pressure Pγ in the canister 2 becomes almost atmospheric pressure. The differential pressure valve 5 is opened. For this reason, as shown in FIG. 3C, a flow of fuel vapor from the canister 2 side toward the fuel tank 1 side is formed inside the breather passage 7, and is adsorbed closer to the vapor introduction port 22 than the vapor guide 40. The fuel vapor from the material layer 20a region is released and back-purged to the fuel tank 1. Therefore, it is possible to suppress the deterioration of the fueling emission at the time of the next fueling.
[0050]
On the other hand, when the fuel tank 1 is cooled by parking for a long time, the generation of fuel vapor in the fuel tank 1 is stopped, and the pressure inside the fuel tank 1 becomes relatively lower than the inside of the canister 2, the tank The pressure in the positive pressure chamber 4c of the internal pressure control valve 4 is a negative pressure. Accordingly, the check ball of the vapory leaf valve 23 moves upward, and the vapory leaf valve 23 is opened. For this reason, the fuel vapor in the canister 2 is returned to the fuel tank 1 through the fuel vapor introduction passage 3.
[0051]
Further, in this failure diagnosis apparatus, a path (hereinafter referred to as these) constituted by fuel vapor introduction portions such as the inside of the fuel tank 1, the fuel vapor introduction passage 3, the breather passage 7, the inside of the canister 2, and the purge passage 8. Are also referred to as a “purge path”), and whether or not there is a leakage abnormality due to a perforated hole or a disconnection of piping is a diagnosis target, and a failure of various valves provided in the purge path is a diagnosis target. Specifically, as a method of diagnosing leakage abnormality in the purge path, the presence or absence of leakage abnormality in the same path is diagnosed based on the pressure behavior in the same path after the fuel vapor introduction passage is sealed under a predetermined negative pressure. Yes.
[0052]
Hereinafter, the execution procedure of the fault diagnosis for leakage abnormality by such a fault diagnosis apparatus will be described with reference to the timing chart shown in FIG.
In addition to conditions such as that the tank internal pressure is stable, that a predetermined time has not elapsed since the engine was started, and that there is no abnormality in the pressure sensor 1a, the failure diagnosis is performed by performing a purge process. That is, it is executed when all the preconditions such as the purge control valve 11 being opened at a predetermined opening based on the operating state are satisfied.
[0053]
When these preconditions are satisfied, first, the pressure blocking valve 27a is driven to close by the ECU 10 (time t10), and the negative pressure of the intake passage 9 is introduced into the purge path. As a result, the pressure in the purge path (= tank internal pressure) gradually decreases (time t10 to t20).
[0054]
Next, when the tank internal pressure reaches the target negative pressure PT (time t20), the purge control valve 11 is forcibly closed by the ECU 10. As a result, the purge path is sealed. If the tank internal pressure does not decrease to the target negative pressure PT even after a predetermined time has elapsed after the introduction of the negative pressure is started, it is diagnosed that a relatively large leak has occurred in the purge path. The
[0055]
As described above, when the inside of the purge path is sealed under a low pressure (negative pressure), the tank internal pressure once decreases to the predetermined negative pressure PT or less, but the fuel in the path (for example, fuel) As the fuel in the tank 1 and the fuel adsorbed by the adsorbent of the canister 2 evaporate, it gradually rises (after time t21). The failure diagnosis, that is, the determination of the presence or absence of leakage abnormality in the purge path is performed based on the rate of increase of the tank internal pressure at this time.
[0056]
That is,
[Normal judgment]
When the increase rate of the tank internal pressure is less than a predetermined value (normal determination value), it is determined that the tank internal pressure is increased only by the evaporation of fuel in the purge path, and there is no leakage abnormality in the same path.
[Abnormal judgment]
When the increase rate of the tank internal pressure is equal to or higher than a predetermined value (abnormality determination value), the tank internal pressure increases due to the inflow of air into the same path in addition to the fuel increase in the same path. It is determined that there is a leakage abnormality.
[Judgment pending]
If the increase rate of the tank internal pressure is equal to or higher than the normal determination value and lower than the abnormality determination value, it is difficult to reliably determine whether there is a leakage abnormality, so that determination is temporarily suspended.
Such a determination is made.
[0057]
Next, purge control and valve failure diagnosis processing executed by the ECU 10 will be described with reference to FIGS. In the following failure diagnosis processing, the fuel tank internal pressure is a relative pressure based on the atmospheric pressure.
[0058]
In this diagnosis process, necessary initial settings are made after the ECU 10 is turned on. For example, there is no abnormality in the pressure sensor 1a and other sensors, and the operation is stable after a certain period of time has elapsed since the engine started operation. In this case, the failure diagnosis process execution condition is satisfied.
[0059]
As described above, when the engine operation is stabilized, first, in step 102, it is determined whether or not the engine coolant temperature THW is equal to or higher than a predetermined temperature A ° C. (for example, 75 ° C.). If it is determined that the engine coolant temperature THW is lower than A ° C., the process proceeds to step 130. If it is determined that the engine coolant temperature THW is equal to or higher than A ° C, the routine proceeds to step 104.
[0060]
In step 130, it is determined whether or not the tank internal pressure is less than -PA (for example, PA = 2.67 kPa = 20 mmHg). If it is determined that the tank internal pressure is equal to or higher than -PA, this routine is once terminated. If it is determined that the tank internal pressure is less than -PA, in the next step 132, it is diagnosed that the pressure block valve is closed abnormally, or the purge control valve and bypass control valve is opened abnormally, and this routine is once ended. This is the case where the tank internal pressure becomes less than -PA before the purge is started when the canister 2 has a negative pressure. The failure condition in which the inside of the canister 2 becomes negative is that the negative pressure of the canister 2 is directly transmitted to the fuel tank 1 when the purge control valve 11 is abnormally opened and the bypass control valve 42 is abnormally opened. The tank internal pressure becomes negative. Further, even if the purge control valve 11 is normal, the fuel consumption is large, so the negative pressure of the tank internal pressure may increase. At this time, when the pressure block valve 27a is abnormally closed, the inside of the canister 2 becomes negative pressure. Become.
[0061]
In step 104, it is determined whether the purge condition is satisfied. If it is determined that the purge condition is not satisfied, the present routine is terminated once. If it is determined that the purge condition is satisfied, the routine proceeds to step 106.
[0062]
In step 106, it is determined whether or not the negative pressure is being introduced into the purge path. If it is determined that the negative pressure is not being introduced, the process proceeds to step 108. If it is determined that the negative pressure is being introduced, the negative pressure introduction leakage detection routine in step 160 is performed. Proceed to
[0063]
In step 108, it is determined whether or not the tank internal pressure is less than -PB (for example, PB = 3.34 kPa = 25 mmHg). If it is determined that the tank internal pressure is equal to or higher than -PB, the process proceeds to step 140. If it is determined that the tank internal pressure is lower than -PB, the purge control valve 11 is closed in step 110 to forcibly stop the purge.
[0064]
In step 140, it is determined whether or not the purge forced stop flag is 1, that is, whether or not the purge control valve 11 is in the closed state. If the determination is affirmative, the process proceeds to step 114. Proceeding to 142, normal purge control is executed.
[0065]
In step 112, it is determined whether t seconds have elapsed after the forced purge stop. If it is determined that t seconds have not elapsed, this routine is once terminated. If it is determined in step 112 that t seconds have elapsed after the forced purge stop, the purge forced stop flag is set to 1 and the process proceeds to step 114.
[0066]
In step 114, it is determined whether or not the tank internal pressure is less than −PA (for example, PA = 2.67 kPa = 20 mmHg). If it is determined that the tank internal pressure is equal to or higher than -PA, the process proceeds to step 150. If it is determined that the tank internal pressure is lower than -PA, in the next step 116, the purge control valve opening abnormality, the pressure block valve closing abnormality, or the bypass is performed. Diagnose abnormalities in control valve opening and pressure block valve closing. This is because the negative pressure in the canister 2 is maintained when the tank internal pressure does not rise to the atmosphere side even if the purge control valve is closed during the purge execution, so that the purge control valve 11 is abnormally opened, Depending on whether the pressure closing valve 27a is closed abnormally, the atmosphere is not introduced into the purge path, or the bypass control valve 42 is opened abnormally, so that the negative pressure in the canister 2 is directly transmitted to the fuel tank 1. .
[0067]
Further, after the processing of step 116, the forced purge stop flag is set to 0 in step 118 and the purge is restarted.
In step 150, it is determined whether the tank internal pressure is less than −PC (for example, PC = 1.33 kPa = 10 mmHg). If it is determined that the tank internal pressure is equal to or higher than -PC, the process proceeds to step 154. If it is determined that the tank internal pressure is lower than -PC, the process proceeds to step 152.
[0068]
In step 152, the purge control valve is normally open / closed, the pressure block valve is open normally, the bypass control valve is closed normally, the differential pressure valve is normal, and the tank's 1.0 mm hole is normal, or the bypass control valve is open and the pressure block valve is abnormal. Diagnose. This is because the internal pressure of the tank changes from a state of less than −PB (= −3.34 kPa) to a state of less than −PC (= −1.33 kPa) by forced purge stop, so that the purge control valve 11 is opened to closed. Since the pressure change has occurred due to the switching, the purge control valve 11 is normally opened and closed. Further, when the internal pressure of the tank rises from less than −PB (= −3.34 kPa) to less than −PC (= −1.33 kPa), the pressure blocking valve 27a is normally opened and the atmosphere is introduced, and the differential pressure valve 5 is normal, and the bypass control valve 42 is normally closed. Further, since the differential pressure valve 5 is normal and the bypass control valve 42 is normally closed, it is determined that there is no 1.0 mm hole in the tank if the tank internal pressure is maintained near -PC after a predetermined time has elapsed. be able to. Therefore, if a 1.0 mm hole abnormality is detected in the detection of a negative pressure introduction leak to the purge path, it is possible to detect the presence of a 1.0 mm hole on the canister 2 side.
[0069]
When it is determined in step 150 that the tank internal pressure is equal to or higher than -PC, in step 154, it is diagnosed that the purge control valve is normally open, the pressure block valve is normally open, and the bypass control valve is abnormal. This is because the internal pressure of the tank changes from a state of less than −PB (= −3.34 kPa) to a state of −PC (= −1.33 kPa) or more due to the forced purge stop, so that the purge control valve 11 is opened to closed. Since the pressure change has occurred due to the switching, the purge control valve 11 is normally opened and closed. Further, when the internal pressure of the tank rises to -PC (= 1.33 kPa) or higher, the pressure block valve 27a is normally open. At this time, the internal pressure of the tank becomes -PC or higher, so that the differential pressure valve 5 is abnormally open. Alternatively, the bypass control valve 42 is closed abnormally.
[0070]
According to the fuel vapor purge system of the present embodiment in which valve failure diagnosis is executed with the aspect described above,
(1) In the engine operating state, the purge control valve 11 is temporarily closed during the purge execution to forcibly stop the purge, and the purge control valve 11, the pressure blocking valve are detected only by detecting the change state of the tank internal pressure at that time. Valve failures such as 27a, bypass control valve 42, and differential pressure valve 5 can be diagnosed. Therefore, the failure diagnosis by introducing the negative pressure need only be a leakage failure diagnosis of the purge path, and the time required for the failure diagnosis can be shortened. Therefore, the purge can be started early and the purge efficiency can be improved.
[0071]
(2) In addition, when the internal pressure of the fuel tank 1 is less than the predetermined pressure P0 during the purge execution, the differential pressure valve 5 can be opened by temporarily closing the purge control valve 11, and thus the canister 2 The fuel vapor remaining in the adsorbent layer 20a region closer to the vapor introduction port 22 than the vapor guide 40 can be back purged into the fuel tank 1. For this reason, at the time of the next refueling, deterioration of the refueling emission from the canister 2 to the atmosphere can be suppressed.
[0072]
(Second Embodiment)
Next, a fuel vapor purge system failure diagnosis apparatus according to a second embodiment of the present invention will be described focusing on differences from the first embodiment. Note that the failure diagnosis apparatus according to the second embodiment is assumed to have the same configuration as that described in the previous first embodiment, and a description thereof will be omitted.
[0073]
In the failure diagnosis apparatus of the first embodiment, the valve failure diagnosis when purge cut is performed from the canister 2 to the fuel tank 1 under the condition that the tank negative pressure using the back purge is large has been described. In this embodiment, when the tank internal pressure is higher than the atmospheric pressure by a predetermined value or more, or when the tank internal pressure is lower than the atmospheric pressure by a predetermined value or more, the valve failure diagnosis is performed in accordance with the purge cut.
[0074]
FIGS. 7 and 8 are flowcharts showing the execution procedure of the valve failure diagnosis process at the time of purge cut, and a series of processes shown in this flowchart is executed by the ECU 10 as an interrupt process every predetermined time (for example, every 65 ms).
[0075]
In this process, first, in step 202, it is determined whether the purge control valve 11 is closed based on whether the purge cut flag is 1 or not. In step 202, if the purge cut flag is 1, that is, if the purge control valve 11 is closed, the process proceeds to step 204. If the purge cut flag is 0, that is, if the purge control valve 11 is opened, the normal purge control in step 250 is performed. Proceed to the routine.
[0076]
In step 204, it is determined whether or not the diagnosis is incomplete based on whether or not the purge cut time diagnosis completion flag is zero. If it is determined in step 204 that the purge cut time diagnosis completion flag is 0, that is, the diagnosis has not been completed, the process proceeds to step 206. If it is determined that the purge cut time diagnosis completion flag is 1, that is, the diagnosis has been completed, Proceed to the purge control routine.
[0077]
In step 206, it is determined whether or not the bypass control valve 42 is closed. If it is determined that the bypass control valve 42 is open, the process proceeds to step 212, and if it is determined that the bypass control valve 42 is closed, the process proceeds to step 208.
[0078]
In step 208, it is determined whether or not the absolute value of the tank internal pressure is equal to or greater than a predetermined pressure P1 (P1> 0). If it is determined that the tank internal pressure absolute value is less than or equal to P1, this routine is terminated. If it is determined that the tank internal pressure absolute value is greater than P1, the routine proceeds to step 210, where the bypass control valve 42 is opened.
[0079]
Then, in the next step 212, it is determined whether t seconds have elapsed after the bypass control valve is opened. If it is determined that t seconds have not elapsed, this routine is once terminated. If it is determined in step 212 that t seconds have elapsed after the bypass control valve is opened, the routine proceeds to step 214.
[0080]
In step 214, it is determined whether the tank internal pressure absolute value is less than a predetermined pressure P2 (P1> P2> 0). If it is determined that the tank internal pressure absolute value is greater than or equal to P2, the process proceeds to step 220. If it is determined that the tank internal pressure absolute value is less than P2, in the next step 216, the purge control valve close normal, the purge control valve close normal, and Diagnose that the pressure-blocking valve is open normally. When the purge control valve 11 is closed during the purge execution, the bypass control valve 42 is switched from the closed state to the open state, so that the tank internal pressure approaches the atmosphere, so that the bypass control valve is normally opened and closed, and the purge control valve is normally closed. , And the fact that the pressure block valve is normally open can be determined.
[0081]
Further, after the process of step 216, the purge cut diagnosis completion flag is set to 0 in step 218, and the purge is resumed.
In step 220, it is determined whether the tank internal pressure is less than -P1. If it is determined that the tank internal pressure is equal to or higher than -P1, the process proceeds to step 224. If it is determined that the tank internal pressure is less than -P1, the process proceeds to step 222. In step 222, it is diagnosed that the purge control valve is open abnormally, and thereafter, the process proceeds to step 218.
[0082]
If it is determined in step 220 that the tank internal pressure is equal to or higher than -P1, it is determined in step 224 whether the tank internal pressure is greater than P1. If it is determined that the tank internal pressure is less than or equal to P1, this routine is once terminated. If it is determined that the tank internal pressure is greater than P1, the routine proceeds to step 226. In step 226, it is diagnosed that the bypass control valve is closed abnormally, and thereafter, the process proceeds to step 218.
[0083]
According to the fuel vapor purge system of the present embodiment in which valve failure diagnosis is executed with the aspect described above,
(1) At the time of completion of negative pressure introduction in the negative pressure introduction leak diagnosis, it is possible to determine whether the purge control valve is open normally or the pressure block valve is closed normally. Therefore, the time required for failure diagnosis can be shortened, and thus the purge can be started early to improve the purge efficiency.
[0084]
(2) Further, in this embodiment, instead of forcibly performing a purge cut during the purge execution, the valve failure diagnosis can be performed using the purge cut applied to the traveling state of the vehicle. The purge flow rate is not reduced.
[0085]
In addition, each said embodiment can also be implemented by changing the structure as follows.
In each of the above-described embodiments, the fuel tank 1 and the canister 2 are embodied as a fuel vapor purge system in a type in which the fuel tank 1 and the canister 2 are communicated with each other by the bypass passage 41 including the bypass control valve 42. May be embodied in a fuel vapor purge system of the type that communicates with the orifice.
[0086]
-The valve opening pressure of the differential pressure valve 5 in each said embodiment can be changed into arbitrary values as needed.
Next, other technical ideas that can be grasped from the above embodiments will be described below.
[0087]
The fuel vapor purge system according to claim 1, wherein the first and second ports are connected to each other by a pipe line, and the pipe line is diagnosed when a diagnosis relating to airtightness of the enclosed space is performed. There is provided one introduction port for introducing a pressure for use, and a diagnostic pressure introduced from the introduction port is introduced into the second port between the introduction port and the second port. And a fuel vapor purge system provided with a check valve for preventing the pressure acting on the second port from being led to the outside through the introduction port.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a fuel vapor purge system and a failure diagnosis device of a first embodiment.
FIG. 2 is a schematic sectional view showing a differential pressure valve.
FIG. 3 is an explanatory view showing the flow of fuel vapor in the canister.
FIG. 4 is a flowchart showing a processing procedure of purge control and valve failure diagnosis processing in the first embodiment.
FIG. 5 is a flowchart showing a processing procedure of purge control and valve failure diagnosis processing in the first embodiment.
FIG. 6 is a timing chart for explaining a procedure of failure diagnosis by the failure diagnosis apparatus.
FIG. 7 is a flowchart showing a processing procedure of valve failure diagnosis processing at the time of purge cut in the second embodiment.
FIG. 8 is a flowchart showing a processing procedure of valve failure diagnosis processing at the time of purge cut in the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 1a ... Pressure sensor, 2 ... Canister, 3 ... Fuel vapor introduction passage, 5 ... Differential pressure valve, 7 ... Breather passage, 8 ... Purge passage, 10 ... ECU, 11 ... Purge control valve, 27a ... Pressure blockade Valve, 42 ... Bypass control valve.

Claims (2)

A differential pressure valve that collects fuel vapor generated in the fuel tank in the canister, opens based on the difference between the internal pressure of the fuel tank and the internal pressure on the canister side, and allows the inflow of fuel vapor from the fuel tank to the canister, and a purge passage A purge control valve that opens and closes the air inlet and a pressure block valve that opens and closes the air inlet, and purges the fuel vapor collected in the canister while opening the purge control valve and the pressure block valve to introduce the atmosphere into the canister A fuel vapor purge system that purges to the intake passage of the internal combustion engine through the passage, and the purge passage is sealed by closing the pressure block valve and the purge control valve by providing a differential pressure between the internal pressure and the external pressure of the purge passage Diagnostic means for diagnosing whether there is a leakage abnormality in the purge path based on the change state of the internal pressure measured
In a fault diagnosis apparatus for a fuel vapor purge system comprising:
  The fuel vapor purge wherein the diagnosis means diagnoses a failure of the purge control valve, the pressure block valve and the differential pressure valve based on a change state of the internal pressure of the purge path when the purge control valve is closed during the purge. System fault diagnosis device. 2. The failure diagnosis apparatus for a fuel vapor purge system according to claim 1, wherein the differential pressure valve is opened when the internal pressure of the fuel tank is lower than a predetermined value by a predetermined value or more than the internal pressure of the canister.

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