JP3552670B2

JP3552670B2 - Abnormality diagnosis method and abnormality diagnosis apparatus for evaporative fuel purge device

Info

Publication number: JP3552670B2
Application number: JP2001007808A
Authority: JP
Inventors: 秀樹宮原; 登喜司伊藤; 修一花井
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2001-01-16
Filing date: 2001-01-16
Publication date: 2004-08-11
Anticipated expiration: 2021-01-16
Also published as: JP2002213305A

Description

【０００１】
【発明の属する技術分野】
本発明は、車両において燃料タンクから蒸発する燃料を内燃機関の吸気系に放出する蒸発燃料パージ装置の異常診断方法及び異常診断装置に関するものである。
【０００２】
【従来の技術】
上記のような蒸発燃料パージ装置は、燃料タンクで発生した燃料蒸気をベーパ管を介してチャコールキャニスタ（以下、キャニスタという。）に一旦捕集し、捕集した蒸発燃料をパージ管を介して内燃機関の吸気系に放出する。このとき、パージ管を介して吸気系からキャニスタ及び燃料タンクまで負圧を導入するとともに、新気導入管を介してキャニスタに外気を導入することで捕集されている燃料蒸気を放出（パージ）させる。
【０００３】
一方、異常診断装置は、吸気系から負圧が導入されるパージ管からキャニスタを経て燃料タンクまで至る燃料蒸気放出流路上に、燃料蒸気が外気に漏出するピンホールや亀裂が生じているか否かその気密状態を検査する異常診断を行う。
【０００４】
この異常診断は、図４に示すように、パージ管上のパージ量調節弁を開けたまま新気導入管上の新気量調節弁を閉じてパージを中断し、吸気系から導入する負圧によって燃料タンクの内圧Ｐを第１基準値Ｐ２まで低下させた後にパージ量調節弁でパージ管を遮断することで行う。この状態では、燃料タンクからキャニスタを経てパージ管の途中に至るまでの診断流路が外気から密封される。
【０００５】
この密封された診断流路の内圧Ｐは、燃料タンク内での燃料の蒸発により、この診断流路内にある空気及び燃料蒸気の平衡圧に近づくように徐々に上昇していく。このとき、診断流路上にピンホールや亀裂が存在していると、そこから燃料蒸気が外部に漏出することで内圧Ｐはより急速に上昇する。そこで、燃料タンクに設けた圧力センサで内圧Ｐを検出し、この内圧Ｐの変化様態を監視することでピンホール等の有無を検査する。
【０００６】
ところが、車両が悪路を走行する場合には、燃料タンク内の燃料が激しく揺れ、その油面が揺れることで燃料の気化が促進される。このため、悪路を走行中に診断流路の異常診断を行うと、検出される内圧Ｐがより急速に上昇する。また、燃料温度が高くなった状況でも、燃料の気化が促進される。このため、燃料温度が高くなった状態で異常診断を行ったときにも、診断流路の内圧Ｐがより急速に上昇する。従って、車両が悪路を走行している状態や、燃料温度が高くなった状態で診断流路の異常診断を行うと、内圧Ｐの変化様態から診断流路の気密性を確実に検査することが困難となり、診断結果の信頼性が低下したり、誤診断する可能性がある。そこで、従来の異常診断装置では、異常診断を行う前に、車両の走行状態が燃料の激しい油面揺れを招くような状態でなく、また、燃料温度が高くなっておらず、異常診断が可能な状態であることを確認する診断条件の判定を行なっている。
【０００７】
この診断条件の判定方法としては、例えば特開平１０−２６０５５号公報で開示されているエバポパージシステムの故障診断装置で行うように、異なるサンプリング様態で検出する２つのサンプリング値の差分値ΔＰが判定値を超えたことをもって、燃料の激しい油面揺れが発生していると判定する方法がある。また、図４に示すように、燃料タンクの内圧Ｐの判定時間Ｔ１当たりの変化量ΔＰ１が判定値を超えたことをもって、燃料温度が高くなった状態であると判定する方法が提案されている。さらに、一定時間離れた時点で検出する内圧Ｐの各変化量ΔＰから２階差分積算値ΣΔΔＰを算出し、この２階差分積算値ΣΔΔＰが判定値を超えたことをもって燃料の激しい油面揺れが発生したと判定する方法が提案されている。
【０００８】
ところで、キャニスタから蒸発燃料のパージを行なっているときには、吸気系からパージ管を介してキャニスタに導入される負圧が燃料タンクにまで導入される。従って、燃料タンクで検出する内圧Ｐが、エンジンの運転状態に応じて変動する吸気圧によっても変動する。このため、診断条件の判定を内圧Ｐの変化量ΔＰや２階差分値ΔＰＰが判定値を超えたことをもって判定することが困難となる。そこで、従来の異常診断装置には、ベーパ管上に設けた差圧弁を迂回する負圧導入管と、負圧導入管を開閉する開閉弁とが設けられていた。そして、診断条件の判定を行うときには開閉弁を閉じて吸気系からキャニスタに導入する負圧が燃料タンクに直接導入されないようにし、異常診断を行うときには開閉弁を開けて負圧導入管を介して燃料タンクに負圧を導入するようにしていた。ところが、異常診断の判定を行うためだけに負圧導入管及び開閉弁を設けているので、異常診断装置が複雑になり原価が高くなっていた。
【０００９】
そこで、負圧導入管及び開閉弁を設けてない異常診断装置とし、図４に示すように、変化量ΔＰ１や２階差分積算値ΔΔＰを求めて診断条件の判定を行うときにはパージ量調節弁を閉じてパージを中断（パージカット）することが考えられる。この場合には、診断条件の判定中に吸気管から負圧がキャニスタ及び燃料タンクに導入されないので、吸気管内の負圧の変動の影響を受けない内圧Ｐから求めた例えば２階差分積算値ΔΔＰが判定値αを超えたことをもって、燃料の過度の油面揺れが発生したことを検知することができる。
【００１０】
【発明が解決しようとする課題】
しかしながら、パージを中断した状態で診断条件の判定を行うようにすると、車両が悪路を走行中であった場合には、診断条件の判定を行う毎にパージを中断することになる。そして、診断条件の判定によって燃料の激しい油面揺れが発生していると判定した後に、異常診断を行うことなくパージを再開することになる。このため、車両が悪路を走行する状態が続くと、頻繁にパージが中断されることになり、パージが実行される時間が全体として短くなってしまう。
【００１１】
本発明は、上記課題を解決するためになされたものであって、その目的は、蒸発燃料捕集装置に捕集した蒸発燃料の放出を中断する時間をより短縮することができる蒸発燃料パージ装置の異常診断方法及び異常診断装置を提供することにある。
【００１２】
【課題を解決するための手段】
上記問題点を解決するため、請求項１に記載の発明は、燃料タンクで発生する燃料蒸気をベーパ流路を介して蒸発燃料捕集装置に捕集し、内燃機関の吸気系からパージ流路を介して負圧を蒸発燃料捕集装置に導入するとともに新気導入流路を介して新気を蒸発燃料捕集装置に導入することで該蒸発燃料捕集装置に捕集した燃料蒸気を前記パージ流路を介して前記吸気系に放出する蒸発燃料パージ装置の異常診断方法において、前記新気導入流路及びパージ流路を共に遮断することで前記燃料タンクを含んで密封される診断流路内の内圧を検出し、燃料の液面揺れを検知するための検知量を、前記蒸発燃料捕集装置から燃料蒸気を放出している状態で検出する前記内圧の変化量から予め設定されている方法で求め、予め設定されている第１判定値をこの検知量が超えたことをもって前記内圧を異常な様態で上昇させる燃料の液面揺れが発生したと判定し、前記検知量が第１判定値を超えないときには、前記蒸発燃料捕集装置からの燃料蒸気の放出を停止した状態で検出する内圧の変化量から前記検知量を求め、前記第１判定値よりも小さい値で予め設定されている第２判定値をこの検知量が超えたことをもって前記内圧を異常な様態で上昇させる燃料の液面揺れが発生したと改めて判定し、前記検知量が第２判定値を超えないときに、前記診断流路を密封した状態での前記内圧の経時的な変化様態から該診断流路の気密状態を診断することを要旨とする。
【００１３】
請求項１に記載の発明によれば、吸気系から導入する負圧の変動が診断流路で検出する内圧の変動に影響する状態で内圧を検出し、この内圧から求めた検知量が第１判定値を超えることをもって、車両の走行状態に基づく燃料タンク内の燃料の液面揺れが、内圧の異常な変動を招く状態であることが判定される。そして、車両の走行状態が内圧の異常な上昇を招かない状態であると判定したときに初めて負圧の導入が停止され、負圧の変動が内圧に影響しない状態で、改めて車両の走行状態に基づく燃料の液面揺れが判定される。従って、車両の走行状態が燃料の激しい液面揺れを招くような状態であって、内圧の変化様態から診断流路の気密状態を検査することが容易でないような状況で、異常診断が実行されないにも拘らず蒸発燃料の放出が頻繁に中断されことがない。
【００１４】
請求項２に記載の発明は、請求項１に記載の発明において、前記蒸発燃料捕集装置から蒸発燃料の放出を停止した状態で検出する内圧の計時的な変化様態に基づいて該内圧を異常な様態で上昇させる燃料温度の上昇が発生したか否かを判定し、前記内圧を異常な様態で燃料の液面揺れが発生していないと判定し、かつ、内圧を異常な様態で上昇させる燃料温度の上昇が発生していないと判定したときに前記診断流路を密封した状態での前記内圧の経時的な変化様態から該診断流路の気密状態を診断することを要旨とする。
【００１５】
請求項２に記載の発明によれば、請求項１に記載の発明の作用に加えて、燃料の液面揺れに起因する内圧の異常な変動が小さいと判定したことに加え、燃料温度の上昇に起因する内圧の変動が小さいと判定したときに、内圧の変化様態に基づいて診断流路の気密状態が検査される。このため、診断流路の気密状態に関する診断結果の信頼性がより向上し、また、誤診断がより発生し難い。
【００１６】
請求項３に記載の発明は、燃料タンクで発生する燃料蒸気をベーパ流路を介して蒸発燃料捕集装置に捕集するとともに、内燃機関の吸気系からパージ流路を介して負圧を蒸発燃料捕集装置に導入し、新気導入流路を介して新気を蒸発燃料捕集装置に導入することで、蒸発燃料捕集装置に捕集した燃料蒸気をパージ流路を介して前記吸気系に放出する蒸発燃料パージ装置の異常診断装置において、前記新気導入流路を遮断可能な新気流路遮断手段と、前記パージ流路を遮断可能なパージ流路遮断手段と、前記新気流路開閉手段及びパージ流路開閉手段を制御する流路制御手段と、前記新気導入流路及びパージ流路が共に遮断されることで前記燃料タンクを含んで密封される診断流路内の内圧を検出する内圧検出手段と、燃料の液面揺れを検知するための検知量を予め設定されている方法で前記内圧の変化量から求める検知量取得手段と、前記流路制御手段を制御し、前記新気導入流路及びパージ流路を共に遮断しない状態で検出された前記内圧の変化量から求めた前記検知量が予め設定されている第１判定値を超えたときに前記新気導入流路を遮断しない状態でパージ流路を遮断し、この状態で検出された内圧から求めた前記検知量が前記第１判定値よりも小さい値に予め設定されている第２判定値を超えたときに前記新気導入流路を遮断するとともにパージ流路を遮断しなくすることで前記内圧を下げた後、新気導入流路を遮断したままでパージ流路を遮断して前記診断流路を密封する内圧制御手段と、前記診断流路を密封した状態での前記内圧の変化様態から該診断流路の気密状態を検査する流路検査手段とを備えたことを要旨とする。
【００１７】
請求項３に記載の発明によれば、吸気系から導入する負圧の変動が診断流路で検出する内圧の変動に影響する状態で内圧を検出し、この内圧から求めた検知量が第１判定値を超えることをもって、車両の走行状態に基づく燃料タンク内の燃料の液面揺れが、内圧の異常な変動を招く状態であることが判定される。そして、車両の走行状態が内圧の異常な上昇を招かない状態であると判定したときに初めて負圧の導入が停止され、負圧の変動が内圧に影響しない状態で、改めて車両の走行状態に基づく燃料の液面揺れが判定される。従って、車両の走行状態が燃料の激しい液面揺れを招くような状態であって、内圧の変化様態から診断流路の気密状態を検査することが容易でないような状況で、異常診断が実行されないにも拘らず蒸発燃料の放出が頻繁に中断されことがない。
【００１８】
請求項４に記載の発明は、請求項３に記載の発明において、前記内圧制御手段が前記新気導入流路を遮断せずパージ流路を遮断している状態で検出された前記内圧の経時的な変化様態に基づいて燃料温度の過度の上昇を検知する燃料温度上昇検知手段を備え、前記内圧制御手段は、前記新気導入流路を遮断せずパージ流路を遮断した状態で検出された内圧から求めた前記検知量が前記第２判定値を超えず、かつ、燃料温度の過度の上昇が検知されないときに前記新気導入流路を遮断するとともにパージ流路を遮断しなくして前記内圧を下げることを要旨とする。
【００１９】
請求項４に記載の発明によれば、請求項３に記載の発明の作用に加えて、燃料の液面揺れに起因する内圧の異常な変動が小さいと判定したことに加え、燃料温度の上昇に起因する内圧の変動が小さいと判定したときに、内圧の変化様態に基づいて診断流路の気密状態が検査される。このため、診断流路の気密状態の診断結果の信頼性がより向上し、また、誤診断がより発生し難い。
【００２０】
請求項５に記載の発明は、請求項３または請求項４に記載の発明において、
前記検知量は、前記内圧の変化量から求めた２階差分値を積算した２階差分積算値であることを要旨とする。
【００２１】
請求項５に記載の発明によれば、請求項３または請求項４に記載の発明の作用に加えて、内圧の変化量から求めた２階差分値を積算した２階差分積算値が予め設定した判定値を超えたことをもって、車両の走行状態に基づく燃料の液面揺れが内圧の異常な上昇を招く状態であると判定するので、内圧の変化様態に基づいて行う診断流路の気密性の検査精度がより向上する。
【００２２】
【発明の実施の形態】
以下、本発明を車両の内燃機関に設けられた蒸発燃料パージ装置の異常診断装置に具体化した一実施形態を図１〜図４に従って説明する。
【００２３】
図２に示すように、蒸発燃料パージ装置１０は、ベーパ管１１、差圧弁１２、蒸発燃料捕集装置としてのチャコールキャニスタ（以下、単にキャニスタという。）１３、パージ流路としてのパージ管１４、パージ流路遮断手段としてのパージ量調節弁１５、新気導入流路としての新気導入管１６、新気流路遮断手段としての新気量調節弁１７、防塵フィルタ１８及び電子制御装置（以下、ＥＣＵという。）１９等から構成されている。また、異常診断装置２０は、パージ量調節弁１５、新気量調節弁１７、内圧検出手段としての圧力センサ２１及びＥＣＵ１９等から構成されている。
【００２４】
キャニスタ１３は、ベーパ管１１を介して燃料タンク２２の上部にある気室２２ａに連通されている。ベーパ管１１は、燃料の流入を防止するフロート式逆止弁２３を介して気室２２ａ内に連通されている。ベーパ管１１の途中には、差圧弁１２が設けられている。
【００２５】
差圧弁１２はダイアフラム式の自律動作弁であって、燃料タンク２２の気室２２ａの内圧Ｐとキャニスタ１３側の内圧との差圧が、設定されている差圧値を超えるときに開弁し、気室２２ａ内のの燃料蒸気をキャニスタ１３側に放出する。なお、差圧弁１２の内部には、ダイアフラムの弁部を迂回して燃料タンク２２とキャニスタ１３とを常時連通する連通孔１２ａが設けられている。
【００２６】
また、キャニスタ１３は、パージ管１４を介して図示しない吸気ポートに連通されている。パージ管１４の途中にはパージ量調節弁１５が設けられている。
パージ量調節弁１５はＥＣＵ１９によって制御される負圧作動式の電磁弁であって、パージ管１４を介して吸気管側に放出される燃料蒸気の流量を調節するとともにパージ管１４を遮断する。
【００２７】
また、キャニスタ１３は、新気導入管１６を介して外気に連通されている。新気導入管１６は、給油口２４の近傍に開口されるとともに、その途中には大気防塵フィルタ１８が設けられている。大気防塵フィルタ１８は、新気導入管１６を介してキャニスタ１３に導入される新気中の塵を除去する。新気導入管１６の端部には、新気量調節弁１７が設けられている。
【００２８】
新気量調節弁１７はＥＣＵ１９によって制御される電磁式の流量調節弁であって、新気導入管１６を介して大気中からキャニスタ１３に導入される新気の流量を調節するとともに新気導入管１６を遮断する。
【００２９】
キャニスタ１３は、活性炭を主成分とする吸着材が収容された密閉容器であって、ベーパ管１１を介して放出される燃料蒸気を吸着材に吸着することで一時的に捕集する。キャニスタ１３の内部は、第１室２５及び第２室２６に区画され、両室２５，２６は通気性フィルタ２７を介して連通されている。第１室２５及び第２室２６はそれぞれ２室に区画され、通気性フィルタ２７に隣接する各室には吸着材が充填され、反対側の各室はそれぞれ第１気室２５ａ及び第２気室２６ａとされている。第１気室２５ａには、ベーパ管１１とパージ管１４とがそれぞれ連通されている。第２気室２６ａには、新気導入管１６が連通されている。
【００３０】
以上のように構成された蒸発燃料パージ装置１０では、燃料タンク２２の内圧と、キャニスタ１３の第１気室２５ａの内圧との差圧が、設定されている差圧値を超えているときに、差圧弁１２が開いて燃料タンク２２の気室２２ａから燃料蒸気をキャニスタ１３側に放出する。そして、キャニスタ１３側に放出された燃料蒸気はキャニスタ１３に一時的に捕集される。また、エンジンが運転されているときに吸気管内に発生する負圧により、新気導入管１６を介して新気がキャニスタ１３の第２室２６側から導入するときには、キャニスタ１３に捕集されている蒸発燃料をパージ管１４を介して吸気管に放出する。
【００３１】
次に、上記のように構成された蒸発燃料パージ装置の異常診断装置の電気的構成について説明する。
圧力センサ２１は、燃料タンク２２の気室２２ａの内圧を検出し、その圧力信号ＳＰをＥＣＵ１９に出力する。
【００３２】
ＥＣＵ１９は、パージ量調節弁１５に出力する制御信号ＳＶ１によってその弁開度を調節する。また、新気量調節弁１７に出力する制御信号ＳＶ２によってその弁開度を調節する。
【００３３】
ＥＣＵ１９は、マイクロコンピュータ（以下、マイコンという。）３０、駆動装置３１等からなる。本実施形態では、マイコン３０及び駆動装置３１が、内圧制御手段を構成する。また、マイコン３０が、検知量取得手段、流路検査手段及び燃料温度上昇検知手段である。
【００３４】
マイコン３０は、記憶されている制御プログラムに従い、公知の制御である燃料噴射制御、点火時期制御、アイドル回転数制御、キャニスタパージ制御、各種自己診断等を行う。
（キャニスタパージ制御）
キャニスタパージ制御として、マイコン３０は、冷却水温、エンジン回転数等の検出値に基づいてパージ量調節弁１５及び新気量調節弁１７を制御し、キャニスタ１３からのパージ量を制御する。詳述すると、パージ量調節弁１５を開状態として吸気管からパージ管１４を介して負圧をキャニスタ１３側に作用させるとともに、新気量調節弁１７を開状態として新気導入管１６を介して新気をキャニスタ１３に導入することで、キャニスタ１３に捕集されている蒸発燃料を吸気管に放出させる。また、パージ量調節弁１５及び新気量調節弁１７の各弁開度を調節することでパージ量を調節する。
（異常診断処理）
また、マイコン３０は、新たな処理である蒸発燃料パージ装置の異常診断処理を行う。マイコン３０は、異常診断処理を、キャニスタパージ制御においてキャニスタ１３から蒸発燃料の放出を行なっているとき（以下、パージ時という。）に、予め設定されている制御時間が経過する毎に周期的に実行するルーチンによって行う。この異常診断処理として、マイコン３０は、診断条件判定処理及び診断処理を実行する。そして、診断条件判定処理として、車両の状態が蒸発燃料パージ装置の異常診断を行うことができる状態であるか否かを判定する。また、診断条件判定処理において異常診断を行うことができる状態であると判定したときに診断処理を実行し、この診断処理において蒸発燃料パージ装置１０の実際の異常診断を行う。
（診断条件判定処理）
異常診断処理の処理内容を、図１に示すフローチャートに従って説明する。
【００３５】
診断条件判定処理として、マイコン３０は、先ず、ステップ（以下、Ｓと表記する。）１０で、予め設定されている判定時間（例えば３０秒）内で予め設定されている検出時間（例えば０．５秒）が経過する毎に検出した内圧Ｐから、燃料の油面揺れを判定する検知量としての２階差分積算値ΣΔΔＰを求める。そして、この２階差分積算値ΣΔΔＰが予め設定されている第１判定値α１以下であるか否かを判断する。
【００３６】
詳述すると、周期的に実行するルーチンにおいて今回検出した内圧Ｐと前回検出した内圧Ｐとの差分を変化量ΔＰとして毎回求め、過去の異なる時期に求めた複数の変化量ΔＰと今回求めた変化量ΔＰとから、予め設定されている関係式を用いて変化量ΔＰの経時的な変化量である２階差分値ΔΔＰを算出する。次に、予め設定されている判定時間が経過する毎に、この判定時間内に求めた各２階差分値ΔΔＰを積算した２階差分積算値ΣΔΔＰを算出する。
【００３７】
ここで、２階差分値ΔΔＰは、燃料タンク２２に蓄えられている燃料の油面揺れに基づく内圧Ｐの変動を反映する変数であり、その２階差分積算値ΣΔΔＰは、同じ燃料の油面揺れ量を反映する変数である。また、第１判定値α１は、パージ時において、２階差分積算値ΣΔΔＰがこの第１判定値α１を超えることをもって、燃料の油面揺れに起因する内圧Ｐの上昇程度が過度であると判定することができるように設定されている。そして、内圧Ｐの上昇程度が、診断処理において内圧Ｐの変化様態に基づいて異常診断を行うことができる限度を超える状態であると判定することができるように設定されている。
【００３８】
このＳ１０での処理内容を詳述する。キャニスタ１３からの蒸発燃料の放出が行われているとき（パージ時）には、吸気管からパージ管１４を介してキャニスタ１３に導入される負圧が、差圧弁１２の連通孔１２ａを介して燃料タンク２２まで導入される。このとき、内圧Ｐの変動量は、エンジンの運転状態に応じた負圧の変動が影響する分だけ、蒸発燃料の放出を行なっておらず負圧が燃料タンク２２まで導入されていないとき（パージカット時）よりも大きくなる。その結果、内圧Ｐの変化量ΔＰから求めた２階差分値ΔΔＰ、さらに、２階差分値ΔΔＰを積算した２階差分積算値ΣΔΔＰは、図３に示すように、負圧の変動が影響する分だけ大きくなる。従って、パージ中に検出する内圧Ｐから求めた２階差分積算値ΣΔΔＰを判定する第１判定値α１は、車両の走行状態に応じた燃料の油面揺れに基づく内圧Ｐの変動量に対応した従来の判定値αよりも、負圧の変動が影響する分だけ大きくした値を基にして設定されている。
【００３９】
また、通気抵抗を有する大気防塵フィルタ１８が新気導入管１６に設けられているので、パージ中のパージ率が大きいほど、吸気の変動に基づく２階差分積算値ΣΔΔＰの増分値が大きくなる。このため、使用する大気防塵フィルタ１８の通気抵抗に応じパージ率が１００％のときの２階差分積算値ΣΔΔＰの増分値を実験で求め、負圧の影響を除いた状態で設定する判定値αにこの増分値を加算した値をも基にして第１判定値α１が設定されている。
【００４０】
従って、このＳ１０においてマイコン３０は、パージを行なっている状態において、燃料の油面揺れを招く車両の走行状態が、蒸発燃料パージ装置１０の異常診断を行うことができる状態であるか否かを判定する。
【００４１】
そして、Ｓ１０で２階差分積算値ΣΔΔＰが判定値α１を超えていたときには、診断処理を実行することなく本処理を終了する。
一方、Ｓ１０で２階差分積算値ΣΔΔＰが判定値α１以下であったときには、Ｓ１１で、パージ量調節弁１５を閉弁させて、キャニスタパージ制御で実行しているパージを中断させる。
【００４２】
次に、Ｓ１２で、パージを中断している状態で検出する内圧Ｐの変化量ΔＰから２階差分値ΔΔＰさらに２階差分積算値ΣΔΔＰを求め、この２階差分積算値ΣΔΔＰが予め設定されている第２判定値α２以下であるか否かを判定する。さらに、予め設定されている判定時間Ｔ１が経過する間の内圧Ｐの変化量ΔＰ１が、予め設定されている判定値β以下であるか否かを判定する。そして、この両方の条件が共に成立するか否かを判定する。
【００４３】
ここで、第２判定値α２は第１判定値α１よりも小さい値に設定され、パージを行っていない状態において検出する内圧Ｐから求めた２階差分積算値ΣΔΔＰがこの第２判定値α２を超えることをもって、燃料の油面揺れが過度であると判定することができるように設定されている。そして、第２判定値α２は、燃料の油面揺れに起因する内圧Ｐの上昇程度が、診断処理において内圧Ｐの変化様態に基づいて異常診断を行うことができる限度を超える状態であると判定することができるように設定されている。
【００４４】
即ち、パージカット時には燃料タンク２２まで吸気管から負圧が導入されず、内圧Ｐの変動に負圧の変動が影響しない。従って、車両の走行状態が変化しなくても内圧Ｐの変動が小さくなり、図３に示すように、この内圧Ｐから求める２階差分積算値ΣΔΔＰも小さくなる。このため、パージカット状態で検出する内圧Ｐから求めた２階差分積算値ΣΔΔＰが、第１判定値α１よりも小さい値に設定した第２判定値α２を超えたことをもって内圧Ｐの異常な上昇を招く燃料の油面揺れが発生したと判定する。従って、この第２判定値α２は、従来において、パージを中断した状態で検出する内圧Ｐから求めた２階差分積算値ΔΔＰに基づいて燃料の過度な油面揺れを判定する場合の判定値αと同じであってもよい。
【００４５】
また、内圧Ｐの変化量ΔＰ１は、燃料タンク２２の燃料温度の上昇様態を反映する変数である。判定値βは、変化量ΔＰ１がこの判定値βを超えることをもって、車両状況に応じた燃料温度の上昇程度が内圧Ｐの異常な上昇を招く状態であると判定することができるように設定されている。そして、診断処理において内圧Ｐの変化様態に基づいて異常診断を行うことができる限度を超える状態であると判定することができるように設定されている。
【００４６】
従って、このＳ１２で、マイコン３０は、パージカット状態において、車両の走行状態に応じた燃料の油面揺れ状態と、車両状況に応じた燃料温度の上昇状態とが、共に診断処理において異常診断を行うことができる状態であるか否かを判定する。
【００４７】
Ｓ１２で条件が成立しなかったときには、Ｓ１３でパージを再開させた後、Ｓ１４で異常フラグをリセットして本処理を終了する。一方、Ｓ１２で条件が成立したときには診断処理を実行する。
（診断処理）
診断処理として、マイコン３０は、Ｓ１５で、パージ量調節弁１５を閉弁から開弁させ、新気量調節弁１７を開弁から閉弁させることで、吸気管から負圧をパージ管１４を介してキャニスタ１３に導入する。そして、キャニスタ１３から差圧弁１２の連通孔１２ａを介して燃料タンク２２まで負圧を導入し、図３に示すように、内圧Ｐを予め設定されている第１基準値Ｐ２以下まで低下させる。
【００４８】
次に、Ｓ１６で、新気量調節弁１７を閉弁させたままパージ量調節弁１５を開弁から閉弁させ、パージ管１４からキャニスタ１３を経て燃料タンク２２に至るまでの診断流路を密封する。そして、密封された燃料タンク２２の内圧Ｐが、燃料の気化に伴って上昇し再び第１基準値Ｐ２に達した時点から、図３に示すように、予め設定されている検出時間ΔＴｓだけ経過する間の内圧Ｐの変化量ΔＰ２を取得する。
【００４９】
次に、Ｓ１７で、図３に示すように、第１基準値Ｐ２に達した時点から、予め設定されている判定時間Ｔｄが経過した時点での内圧Ｐが、第２基準値Ｐ３以上となったか否かを判定する。
【００５０】
ここで、第２基準値Ｐ３及び判定時間Ｔｄは、判定時間Ｔｄが経過する間に内圧Ｐが第１基準値Ｐ２から第２基準値Ｐ３を超えて上昇したことをもって、燃料タンク２２を含む診断流路の気密状態に異常がないと判定することができるように設定されている。
【００５１】
詳述すると、第１基準値Ｐ２まで下げられた内圧Ｐは、燃料タンク２２内での燃料の蒸発によって時間の経過とともに次第に上昇する。このとき、密封された診断流路内に燃料蒸気が外部に漏出するピンホールや亀裂がなければ、内圧Ｐの上昇様態は、燃料タンク２２の形状、診断流路の容積等の車両に固有の固定値によってほぼ決定される。そして、第２基準値Ｐ３及び判定時間Ｔｄは、この蒸発燃料パージ装置１０において、密封される診断流路からの燃料蒸気の漏出がない状態で内圧Ｐが第１基準値Ｐ２からある第２基準値Ｐ３まで達するまでに要する時間を基に設定されている。
【００５２】
従って、このＳ１７で、マイコン３０は、燃料タンク２２を含む診断流路の気密状態を判定する。
Ｓ１７で、判定時間Ｔｄが経過した時点での内圧Ｐが、第２基準値Ｐ３未満であったときには、Ｓ１３でパージを再開させた後、Ｓ１４で異常フラグをリセットして本処理を終了する。
【００５３】
従って、このＳ１７で、燃料タンク２２を含む診断流路に、燃料蒸気が漏出するピンホールや亀裂を検知しなかったときには、以後の処理を実行せず、キャニスタ１３からの蒸発燃料の放出を再開させる。
【００５４】
一方、Ｓ１７で、判定時間Ｔｄが経過した時点での内圧Ｐが、第２基準値Ｐ３以上であったときには、Ｓ１８で、図３に示すように、第２基準値Ｐ３に達した時点から検出時間ΔＴｓが経過するまでの間の内圧Ｐの変化量ΔＰ３を取得する。
【００５５】
次に、Ｓ１９で、変化量ΔＰ２及びＰ３から圧力変化率ΔＰ２／ΔＰ３を求め、この圧力変化率ΔＰ２／ΔＰ３と変化量ΔＰ３とを、予め記憶されているマップに照らし合わせることで、密封する診断流路内に燃料蒸気が漏出するピンホールや亀裂等があるか否かを改めてより高い検知精度で判定する。
【００５６】
ここで、第２基準値Ｐ３及び圧力変化率ΔＰ２／ΔＰ３を照合するマップは、密封する診断流路に燃料蒸気が漏出するピンホールや亀裂がある場合とない場合とにおける、第１基準値Ｐ２から第２基準値Ｐ３までの内圧Ｐの上昇様態の相違点を反映する第２基準値Ｐ３及び圧力変化率ΔＰ２／ΔＰ３とを、二次元で正常領域、異常領域及び判定保留領域に対応させたものである。
【００５７】
詳述すると、第１基準値Ｐ２からの内圧Ｐの上昇様態は、以下の４つの条件によって特徴づけられることが分かっている。第１は、内圧Ｐが第１基準値Ｐ２からより大きくなるほどその変化量ΔＰが次第に小さくなる。第２は、燃料タンク２２の燃料残量が少ないほど内圧Ｐの上昇速度が遅くなる。第３は、診断流路から燃料蒸気が漏出するときには内圧Ｐが直線的に速く上昇する。第４は、第１基準値Ｐ２からの内圧Ｐの変化量は、燃料蒸気が漏出するときの変化量が漏出しないときの変化量を上回るが、内圧Ｐがある値まで上昇して以降は、燃料蒸気が漏出しないとき変化量が漏出するときの変化量を上回るようになる。そして、この各特徴点を、第２基準値Ｐ３及び圧力変化率ΔＰ２／ΔＰ３に置き換え、この両値の組み合せによって、燃料蒸気が漏れてない状態と、漏れていない状態と、いずれとも判定できない状態とを判定する。
【００５８】
従って、Ｓ１９で、マイコン３０は、燃料タンク２２を含む診断流路の気密状態を改めて判定する。
Ｓ１９で、診断流路の気密状態が正常であると判定したときには、Ｓ１３でパージを再開させた後、Ｓ１４で異常フラグをリセットして本処理を終了する。
【００５９】
一方、Ｓ１９で、診断流路の気密状態が異常であると判定するか、または、判定を保留したときには、Ｓ２０で異常フラグをセットして本処理を終了する。
（実施形態の効果）
以上詳述した本実施形態によれば、以下の効果を得ることができる。
【００６０】
（１）パージをしている状態で内圧Ｐを検出し、この内圧Ｐの変化量ΔＰから求めた２階差分積算値ΣΔΔＰが第１判定値α１を超えることをもって、車両の走行状態に基づく燃料の油面揺れが、内圧Ｐの異常な上昇を招く状態であることが判定される。そして、車両の走行状態が内圧Ｐの異常な上昇を招かない状態であると判定されたときに初めてパージが中断され、負圧の変動が内圧Ｐに影響しない状態で改めて車両の走行状態に基づく燃料の油面揺れと、車両状況に応じた燃料温度の異常な上昇とが判定される。この両条件が満たされたときに、診断流路を密封した状態での内圧Ｐの変動様態から、診断流路の気密性が検査される。
【００６１】
従って、車両の走行状態が燃料タンク２２の燃料の激しい油面揺れを招くような状態であって、内圧Ｐの変化様態から診断流路の気密状態を検査することが容易でないような状況で、異常診断が実行されないにも拘らずパージが頻繁に中断されることがない。このため、パージを中断する時間を全体としてより短縮することができる。
【００６２】
（２）パージを中断した状態において、車両の走行状態に基づく燃料の油面揺れに起因する内圧Ｐの異常な変動がないと判定したことに加え、車両の状況に基づく燃料温度の上昇に起因する内圧Ｐの異常な変動がないと判定したことをもって、異常診断を行うことができる車両状況であると判定される。このため、診断流路の気密状態の診断結果の信頼性をより向上させ、誤診断がより発生し難くすることができる。
（その他の実施形態）
以下、上記実施形態以外の実施形態を箇条書で記載する。
【００６３】
・上記実施形態の診断条件判定処理で、内圧Ｐの異常な上昇を招く燃料の油面揺れを検知するための検知量を、異なるサンプリング周期及び徐変量でサンプリングした内圧Ｐの２つの検出値の差分値ΔＰとし、この差分値ΔＰが判定値を超えたことをもって判定する。
【００６４】
・上記実施形態の診断条件判定処理で、内圧Ｐの異常な上昇を招く燃料の油面揺れを検知するための検知量を、内圧Ｐの変化量ΔＰから求めた２次差分値ΔΔＰとする。
【００６５】
・上記実施形態の診断処理で、診断流路の気密状態を検査する方法は、上記実施形態に記載する方法に限らない。
・上記実施形態で、内圧検出手段を、ベーパ管１１上、差圧弁１２、キャニスタ１３、あるいは、パージ管１４におけるパージ量調節弁１５よりもキャニスタ１３側の部分に設けた圧力センサとする。
【００６６】
・上記実施形態で、新気流路遮断手段を、新気量調節弁１７と別に新気導入管１６上に設けた電磁開閉弁とする。また、パージ流路遮断手段を、パージ量調節弁１５とは別にパージ管１４上に設けた電磁開閉弁とする。
（その他の技術思想）
以下、前述した各実施形態から把握される技術的思想をその効果とともに記載する。
【００６７】
（１）請求項１または請求項２に記載の発明において、前記診断流路を密封した状態での内圧の計時的な変化様態を、前記蒸発燃料捕集装置から蒸発燃料を放出させているときの内圧よりも低い値で予め設定されている第１基準値（Ｐ２）に達してからの内圧の変化量と、該第１基準値よりも高い値で予め設定されている第２基準値（Ｐ３）に達してからの内圧の変化量との比に基づいて把握することを特徴とする蒸発燃料パージ装置の異常診断方法。このような構成によれば、診断流路に漏出がない状態とある状態とを明確に判別することができるので、診断流路の気密状態をより高精度に診断することができる。
【００６８】
（２）請求項３〜請求項５のいずれか一項に記載の発明において、前記流路検査手段は、前記診断流路を密封した状態での内圧の計時的な変化様態を、前記蒸発燃料捕集装置から蒸発燃料を放出させているときの内圧よりも低い値で予め設定されている第１基準値（Ｐ２）に達してからの内圧の変化量と、該第１基準値よりも高い値で予め設定されている第２基準値（Ｐ３）に達してからの内圧の変化量との比に基づいて把握することを特徴とする蒸発燃料パージ装置の異常診断装置。このような構成によれば、診断流路に漏出がない状態とある状態とを明確に判別することができるので、診断流路の気密状態をより高精度に診断することができる。
【００６９】
【発明の効果】
請求項１〜請求項５に記載の発明によれば、車両の走行状態が燃料の激しい油面揺れを招くような状態であって、内圧の変化様態から診断流路の気密状態を検査することが容易でないような状況で、異常診断が実行されないにも拘らず蒸発燃料の放出が頻繁に中断されことがない。このため、パージを中断する時間を全体としてより短縮することができる。
【図面の簡単な説明】
【図１】本実施形態の蒸発燃料パージ装置の異常診断装置が行う診断条件判定処理のフローチャート。
【図２】蒸発燃料パージ装置及び異常診断装置の概略構成図。
【図３】パージカットと２階差分積算値及び変化量の判定時期との関係を示すタイムチャート。
【図４】同じく従来におけるタイムチャート。
【符号の説明】
１０…蒸発燃料パージ装置、１１…ベーパ管、１３…蒸発燃料捕集装置としてのチャコールキャニスタ、１４…パージ流路としてのパージ管、１５…パージ流路遮断手段としてのパージ量調節弁、１６…新気導入流路としての新気導入管、１７…新気流路遮断手段としての新気量調節弁、１９…電子制御装置、２０…異常診断装置、２１…内圧検出手段としての圧力センサ、２２…燃料タンク、３０…内圧制御手段を構成する検知量取得手段、流路検査手段及び燃料温度上昇検知手段としてのマイクロコンピュータ、３１…内圧制御手段を構成する駆動回路、Ｐ…内圧、ΔＰ…変化量、ΔΔＰ…２階差分値、ΣΔΔＰ…検知量としての２階差分積算値。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for diagnosing an abnormality of an evaporative fuel purge device that discharges fuel evaporating from a fuel tank in a vehicle to an intake system of an internal combustion engine.
[0002]
[Prior art]
The above-described evaporative fuel purging apparatus once collects fuel vapor generated in a fuel tank through a vapor pipe into a charcoal canister (hereinafter, referred to as a canister), and internalizes the collected evaporative fuel through a purge pipe. Release to the intake system of the engine. At this time, a negative pressure is introduced from the intake system to the canister and the fuel tank through the purge pipe, and outside air is introduced into the canister through the fresh air introduction pipe to release the collected fuel vapor (purge). Let it.
[0003]
On the other hand, the abnormality diagnosis device determines whether there is a pinhole or a crack in which fuel vapor leaks to the outside air on a fuel vapor discharge flow path from a purge pipe into which a negative pressure is introduced from an intake system to a fuel tank via a canister. An abnormality diagnosis for inspecting the airtight state is performed.
[0004]
As shown in FIG. 4, this abnormality diagnosis is performed by closing the fresh air flow control valve on the fresh air inlet pipe while keeping the purge air flow control valve on the purge pipe open, interrupting the purge, and removing the negative pressure introduced from the intake system. After the internal pressure P of the fuel tank is reduced to the first reference value P2, the purge pipe is shut off by the purge amount control valve. In this state, the diagnostic flow path from the fuel tank to the middle of the purge pipe via the canister is sealed from the outside air.
[0005]
The internal pressure P of the sealed diagnostic flow path gradually increases due to the evaporation of fuel in the fuel tank so as to approach the equilibrium pressure of air and fuel vapor in the diagnostic flow path. At this time, if there is a pinhole or a crack in the diagnostic flow path, the internal pressure P increases more rapidly because fuel vapor leaks from the pinhole or crack. Therefore, the internal pressure P is detected by a pressure sensor provided in the fuel tank, and the presence or absence of a pinhole or the like is inspected by monitoring a change state of the internal pressure P.
[0006]
However, when the vehicle travels on a rough road, the fuel in the fuel tank vibrates violently, and the fuel level fluctuates, thereby promoting fuel vaporization. For this reason, if abnormality diagnosis of the diagnostic flow path is performed while traveling on a bad road, the detected internal pressure P increases more rapidly. Further, even in a situation where the fuel temperature becomes high, vaporization of the fuel is promoted. For this reason, even when the abnormality diagnosis is performed in a state where the fuel temperature is high, the internal pressure P of the diagnosis flow path increases more rapidly. Therefore, when the abnormality of the diagnostic flow path is diagnosed in a state where the vehicle is traveling on a rough road or in a state where the fuel temperature is high, it is necessary to reliably check the airtightness of the diagnostic flow path based on a change in the internal pressure P. And the reliability of the diagnosis result may be reduced, or erroneous diagnosis may be performed. Therefore, with the conventional abnormality diagnosis device, before the abnormality diagnosis is performed, the abnormality can be diagnosed because the running state of the vehicle is not in a state that causes severe fuel level fluctuation of the fuel and the fuel temperature is not high. Diagnostic conditions are determined to confirm that the condition is correct.
[0007]
As a method of determining the diagnostic conditions, for example, a difference value ΔP between two sampled values detected in different sampling modes is determined by a failure diagnostic device of an evaporative purge system disclosed in Japanese Patent Application Laid-Open No. 10-26055. There is a method of judging that the fuel level sway has occurred due to exceeding the value. In addition, as shown in FIG. 4, a method has been proposed in which a change in the internal pressure P of the fuel tank per determination time T1 exceeds a determination value, and a determination is made that the fuel temperature is high. . Further, a second-order difference integrated value ΣΔΔP is calculated from each change amount ΔP of the internal pressure P detected at a point in time when a predetermined time has elapsed, and when the second-order difference integrated value ΣΔΔP exceeds the determination value, severe fuel level fluctuation of the fuel is caused. There has been proposed a method of determining that the occurrence has occurred.
[0008]
By the way, when the fuel vapor is purged from the canister, the negative pressure introduced into the canister from the intake system via the purge pipe is introduced into the fuel tank. Therefore, the internal pressure P detected by the fuel tank also varies due to the intake pressure that varies according to the operating state of the engine. For this reason, it is difficult to determine the diagnosis condition based on the change amount ΔP of the internal pressure P or the second-order difference value ΔPP exceeding the determination value. Therefore, the conventional abnormality diagnosis device is provided with a negative pressure introducing pipe that bypasses the differential pressure valve provided on the vapor pipe, and an on-off valve that opens and closes the negative pressure introducing pipe. When the diagnosis condition is determined, the on-off valve is closed to prevent the negative pressure introduced from the intake system into the canister from being directly introduced into the fuel tank. Negative pressure was introduced into the fuel tank. However, since the negative pressure introducing pipe and the on-off valve are provided only for determining the abnormality diagnosis, the abnormality diagnosis device is complicated and the cost is increased.
[0009]
In view of the above, an abnormality diagnosis device without a negative pressure introduction pipe and an on-off valve is provided. As shown in FIG. 4, when determining a diagnosis condition by obtaining the change amount ΔP1 and the second-order difference integrated value ΔΔP, the purge amount adjustment valve is used. It is considered that the purge is closed to interrupt the purge (purge cut). In this case, since the negative pressure is not introduced into the canister and the fuel tank from the intake pipe during the determination of the diagnostic condition, for example, the second-order difference integrated value ΔΔP obtained from the internal pressure P which is not affected by the fluctuation of the negative pressure in the intake pipe. Exceeds the determination value α, it can be detected that excessive fuel level fluctuation of the fuel has occurred.
[0010]
[Problems to be solved by the invention]
However, if the determination of the diagnostic condition is performed in a state where the purge is interrupted, the purge is interrupted every time the diagnostic condition is determined when the vehicle is traveling on a rough road. Then, purging is restarted without performing abnormality diagnosis after it is determined that severe fuel level fluctuation of the fuel has occurred by the determination of the diagnostic conditions. For this reason, if the state in which the vehicle travels on a rough road continues, the purge is frequently interrupted, and the time during which the purge is performed is shortened as a whole.
[0011]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an evaporative fuel purging apparatus capable of further shortening a time for interrupting the release of evaporative fuel collected by an evaporative fuel collector. It is an object of the present invention to provide an abnormality diagnosis method and an abnormality diagnosis device.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the invention according to claim 1 collects fuel vapor generated in a fuel tank through a vapor flow path in an evaporative fuel collecting device, and purges the fuel vapor from an intake system of an internal combustion engine into a purge flow path. The negative pressure is introduced into the evaporative fuel trap through the evaporative fuel trap, and the fresh air is introduced into the evaporative fuel trap through the fresh air introduction passage, whereby the fuel vapor trapped in the evaporative fuel trap is discharged from the evaporative fuel trap. In the method for diagnosing an abnormality of an evaporative fuel purge device that discharges to the intake system via a purge flow path, a diagnostic flow path including the fuel tank is sealed by shutting off both the fresh air introduction flow path and the purge flow path. The internal pressure inside the fuel tank is detected in advance, and the detection amount for detecting the fuel level fluctuation is set in advance from the change amount of the internal pressure detected in a state where the fuel vapor is released from the evaporated fuel collecting device. Determined by the first method It is determined that the fuel level fluctuation that raises the internal pressure in an abnormal manner has occurred due to the detection amount exceeding the detection amount, and when the detection amount does not exceed the first determination value, the evaporative fuel collecting device The detection amount is obtained from the change amount of the internal pressure detected in a state where the release of the fuel vapor is stopped, and the detection amount exceeds a second determination value which is smaller than the first determination value and is set in advance. It is determined again that the liquid level fluctuation of the fuel that raises the internal pressure in an abnormal manner has occurred, and when the detected amount does not exceed the second determination value, the internal pressure of the diagnostic flow path is sealed. The gist of the present invention is to diagnose the hermetic state of the diagnostic flow channel from the change over time.
[0013]
According to the first aspect of the present invention, the internal pressure is detected in a state where the fluctuation of the negative pressure introduced from the intake system affects the fluctuation of the internal pressure detected in the diagnostic flow path, and the detection amount obtained from the internal pressure is the first amount. When the determination value is exceeded, it is determined that the fuel level fluctuation in the fuel tank in the fuel tank based on the running state of the vehicle is a state that causes an abnormal fluctuation of the internal pressure. Then, when it is determined that the running state of the vehicle does not cause an abnormal increase in the internal pressure, the introduction of the negative pressure is stopped only when the change in the negative pressure does not affect the internal pressure. Based on the result, the fuel level fluctuation is determined. Therefore, the abnormality diagnosis is not performed in a state where the running state of the vehicle causes a severe fuel level fluctuation of the fuel, and it is not easy to inspect the airtight state of the diagnostic flow path from the state of the internal pressure change. Nevertheless, the emission of fuel vapor is not interrupted frequently.
[0014]
According to a second aspect of the present invention, in the first aspect of the invention, the internal pressure is abnormal based on a time-dependent change in the internal pressure detected in a state where the release of the vaporized fuel from the vaporized fuel collecting device is stopped. It is determined whether or not the fuel temperature to be raised has increased in a certain manner, the internal pressure has been determined to be abnormal and the fuel level fluctuation has not occurred, and the internal pressure has been increased in an abnormal manner. The gist of the present invention is to diagnose the airtight state of the diagnostic flow path from the change over time of the internal pressure in a state where the diagnostic flow path is sealed when it is determined that the fuel temperature has not risen.
[0015]
According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, it is determined that the abnormal fluctuation of the internal pressure due to the fuel level fluctuation is small, and the fuel temperature rises. When it is determined that the fluctuation of the internal pressure caused by the internal pressure is small, the airtight state of the diagnostic flow path is inspected based on the change state of the internal pressure. For this reason, the reliability of the diagnosis result regarding the airtight state of the diagnosis channel is further improved, and erroneous diagnosis is less likely to occur.
[0016]
According to a third aspect of the present invention, the fuel vapor generated in the fuel tank is collected by the evaporative fuel collecting device through the vapor flow path, and the negative pressure is evaporated from the intake system of the internal combustion engine through the purge flow path. By introducing the fresh air into the evaporative fuel collecting device through the fresh air introducing passage through the fresh air introducing passage, the fuel vapor collected in the evaporative fuel collecting device is sucked into the intake air through the purge passage. An abnormality diagnosis device for an evaporative fuel purge device that discharges fuel into a system, a fresh air flow passage shutoff means capable of shutting off the fresh air introduction flow passage, a purge flow passage shutoff device capable of shutting off the purge flow passage, and the fresh air flow passage A flow path control means for controlling the opening / closing means and the purge flow path opening / closing means; and an internal pressure in a diagnostic flow path sealed including the fuel tank by shutting off both the fresh air introduction flow path and the purge flow path. Internal pressure detecting means for detecting fuel level fluctuations A detection amount obtaining means for obtaining a detection amount for the change amount of the internal pressure by a preset method, and controlling the flow path control means so that both the fresh air introduction flow path and the purge flow path are not shut off. When the detected amount obtained from the detected amount of change in the internal pressure exceeds a first determination value set in advance, the purge flow path is shut off without shutting off the fresh air introduction flow path. When the detection amount obtained from the detected internal pressure exceeds a second determination value set in advance to a value smaller than the first determination value, the fresh air introduction flow path is shut off and the purge flow path is shut off. After reducing the internal pressure by eliminating the internal pressure control means for closing the purge flow path while closing the fresh air introduction flow path and sealing the diagnostic flow path, and in a state where the diagnostic flow path is sealed Airtightness of the diagnostic flow path from And gist that a flow path inspecting means for inspecting.
[0017]
According to the third aspect of the present invention, the internal pressure is detected in a state where the fluctuation of the negative pressure introduced from the intake system affects the fluctuation of the internal pressure detected in the diagnostic flow path, and the detected amount obtained from the internal pressure is the first amount. When the determination value is exceeded, it is determined that the fuel level fluctuation in the fuel tank in the fuel tank based on the running state of the vehicle is a state that causes an abnormal fluctuation of the internal pressure. Then, when it is determined that the running state of the vehicle does not cause an abnormal increase in the internal pressure, the introduction of the negative pressure is stopped only when the change in the negative pressure does not affect the internal pressure. Based on the result, the fuel level fluctuation is determined. Therefore, the abnormality diagnosis is not performed in a state where the running state of the vehicle causes a severe fuel level fluctuation of the fuel, and it is not easy to inspect the airtight state of the diagnostic flow path from the state of the internal pressure change. Nevertheless, the emission of fuel vapor is not interrupted frequently.
[0018]
According to a fourth aspect of the present invention, in the third aspect of the present invention, the internal pressure control means detects the time of the internal pressure detected in a state in which the fresh air introduction flow path is not blocked and the purge flow path is blocked. Temperature rise detection means for detecting an excessive rise in the fuel temperature based on a typical change mode, wherein the internal pressure control means is detected in a state where the purge flow path is shut off without shutting off the fresh air introduction flow path. When the detected amount obtained from the internal pressure does not exceed the second determination value, and when an excessive rise in the fuel temperature is not detected, the fresh air introduction passage is shut off and the purge passage is not shut off. The gist is to reduce the internal pressure.
[0019]
According to the fourth aspect of the invention, in addition to the effect of the third aspect of the invention, it is determined that the abnormal fluctuation of the internal pressure due to the fuel level fluctuation is small, and the fuel temperature rises. When it is determined that the fluctuation of the internal pressure caused by the internal pressure is small, the airtight state of the diagnostic flow path is inspected based on the change state of the internal pressure. For this reason, the reliability of the diagnosis result of the airtight state of the diagnosis channel is further improved, and erroneous diagnosis is less likely to occur.
[0020]
The invention according to claim 5 is the invention according to claim 3 or 4,
The gist is that the detection amount is a second-order difference integrated value obtained by integrating a second-order difference value obtained from the change amount of the internal pressure.
[0021]
According to the fifth aspect of the invention, in addition to the operation of the third or fourth aspect, the second-order difference integrated value obtained by integrating the second-order difference value obtained from the change amount of the internal pressure is set in advance. Since the determination value exceeds the determined value, it is determined that the liquid level fluctuation of the fuel based on the traveling state of the vehicle causes an abnormal increase in the internal pressure. Inspection accuracy is further improved.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment in which the present invention is embodied in an abnormality diagnosis device for an evaporative fuel purge device provided in an internal combustion engine of a vehicle will be described with reference to FIGS.
[0023]
As shown in FIG. 2, the evaporative fuel purge device 10 includes a vapor pipe 11, a differential pressure valve 12, a charcoal canister (hereinafter simply referred to as a canister) 13 as an evaporative fuel collecting device, a purge pipe 14 as a purge flow path, A purge amount control valve 15 as a purge flow path shutoff means, a fresh air introduction pipe 16 as a fresh air flow path, a fresh air flow control valve 17 as a fresh air flow path cutoff means, a dustproof filter 18 and an electronic control unit ECU 19). The abnormality diagnosis device 20 includes a purge amount adjusting valve 15, a fresh air amount adjusting valve 17, a pressure sensor 21 as an internal pressure detecting means, an ECU 19, and the like.
[0024]
The canister 13 communicates with an air chamber 22 a above the fuel tank 22 via a vapor pipe 11. The vapor pipe 11 is connected to the inside of the air chamber 22a via a float check valve 23 for preventing fuel from flowing into the air chamber 22a. A differential pressure valve 12 is provided in the middle of the vapor pipe 11.
[0025]
The differential pressure valve 12 is a diaphragm type autonomously operating valve, and is opened when a differential pressure between the internal pressure P of the air chamber 22a of the fuel tank 22 and the internal pressure of the canister 13 exceeds a set differential pressure value. The fuel vapor in the air chamber 22a is discharged to the canister 13 side. A communication hole 12a is provided inside the differential pressure valve 12 so as to always communicate between the fuel tank 22 and the canister 13, bypassing the valve portion of the diaphragm.
[0026]
The canister 13 is connected to an intake port (not shown) via a purge pipe 14. A purge amount adjusting valve 15 is provided in the middle of the purge pipe 14.
The purge amount control valve 15 is a negative pressure operated solenoid valve controlled by the ECU 19, and controls the flow rate of fuel vapor discharged to the intake pipe side via the purge pipe 14 and shuts off the purge pipe 14.
[0027]
Further, the canister 13 is communicated with the outside air via a fresh air introduction pipe 16. The fresh air introduction pipe 16 is opened in the vicinity of the oil supply port 24, and an air dust filter 18 is provided in the middle thereof. The air dust filter 18 removes dust in fresh air introduced into the canister 13 through the fresh air introducing pipe 16. A fresh air control valve 17 is provided at an end of the fresh air introduction pipe 16.
[0028]
The fresh air control valve 17 is an electromagnetic flow control valve controlled by the ECU 19, and controls the flow rate of fresh air introduced into the canister 13 from the atmosphere through the fresh air introduction pipe 16 and introduces fresh air. Shut off tube 16.
[0029]
The canister 13 is a closed container containing an adsorbent containing activated carbon as a main component, and temporarily collects the fuel vapor discharged through the vapor pipe 11 by adsorbing the adsorbent onto the adsorbent. The interior of the canister 13 is partitioned into a first chamber 25 and a second chamber 26, and both chambers 25 and 26 are communicated via a permeable filter 27. The first chamber 25 and the second chamber 26 are each divided into two chambers, each of the chambers adjacent to the gas permeable filter 27 is filled with an adsorbent, and each of the opposite chambers is a first air chamber 25a and a second air chamber 25, respectively. A chamber 26a is provided. The vapor pipe 11 and the purge pipe 14 communicate with the first air chamber 25a, respectively. The fresh air introduction pipe 16 is connected to the second air chamber 26a.
[0030]
In the evaporative fuel purge device 10 configured as described above, when the differential pressure between the internal pressure of the fuel tank 22 and the internal pressure of the first air chamber 25a of the canister 13 exceeds the set differential pressure value. Then, the differential pressure valve 12 is opened to discharge fuel vapor from the air chamber 22a of the fuel tank 22 to the canister 13 side. Then, the fuel vapor discharged to the canister 13 side is temporarily collected in the canister 13. Further, when fresh air is introduced from the second chamber 26 side of the canister 13 through the fresh air introduction pipe 16 due to the negative pressure generated in the intake pipe when the engine is operating, the fresh air is collected by the canister 13. The fuel vapor is discharged to the intake pipe through the purge pipe 14.
[0031]
Next, the electrical configuration of the abnormality diagnosis device for the evaporated fuel purge device configured as described above will be described.
The pressure sensor 21 detects the internal pressure of the air chamber 22 a of the fuel tank 22 and outputs a pressure signal SP to the ECU 19.
[0032]
The ECU 19 adjusts the valve opening in accordance with the control signal SV1 output to the purge amount adjusting valve 15. Further, the valve opening is adjusted by a control signal SV2 output to the fresh air amount adjusting valve 17.
[0033]
The ECU 19 includes a microcomputer (hereinafter, referred to as a microcomputer) 30, a driving device 31, and the like. In the present embodiment, the microcomputer 30 and the driving device 31 constitute an internal pressure control unit. Further, the microcomputer 30 is a detection amount acquisition unit, a flow path inspection unit, and a fuel temperature rise detection unit.
[0034]
The microcomputer 30 performs well-known control such as fuel injection control, ignition timing control, idle speed control, canister purge control, and various self-diagnoses according to the stored control program.
(Canister purge control)
As the canister purge control, the microcomputer 30 controls the purge amount control valve 15 and the fresh air amount control valve 17 based on detected values of the cooling water temperature, the engine speed, and the like, and controls the purge amount from the canister 13. More specifically, the purge amount control valve 15 is opened to apply a negative pressure from the intake pipe to the canister 13 through the purge pipe 14, and the fresh air control valve 17 is opened to open the fresh air introduction pipe 16. By introducing fresh air into the canister 13, the fuel vapor collected by the canister 13 is discharged to the intake pipe. Further, the purge amount is adjusted by adjusting the respective valve openings of the purge amount control valve 15 and the fresh air amount control valve 17.
(Abnormality diagnosis processing)
Further, the microcomputer 30 performs a new process of diagnosing abnormality of the evaporated fuel purge device. The microcomputer 30 performs the abnormality diagnosis process periodically every time a preset control time elapses when the evaporative fuel is being discharged from the canister 13 in the canister purge control (hereinafter, referred to as purge time). Performed by the routine to be executed. As the abnormality diagnosis processing, the microcomputer 30 executes a diagnosis condition determination processing and a diagnosis processing. Then, as a diagnosis condition determination process, it is determined whether or not the vehicle is in a state in which abnormality diagnosis of the evaporated fuel purge device can be performed. Further, when it is determined in the diagnosis condition determination processing that it is in a state where abnormality diagnosis can be performed, the diagnosis processing is executed, and in this diagnosis processing, the actual abnormality diagnosis of the evaporative fuel purge device 10 is performed.
(Diagnosis condition judgment processing)
The processing contents of the abnormality diagnosis processing will be described with reference to the flowchart shown in FIG.
[0035]
As a diagnosis condition determination process, the microcomputer 30 firstly performs a detection time (for example, 0. 0) within a predetermined determination time (for example, 30 seconds) in step (hereinafter referred to as S) 10. From the internal pressure P detected every 5 seconds), a second-order difference integrated value ΣΔΔP as a detection amount for determining the oil level fluctuation of the fuel is obtained. Then, it is determined whether or not the second-order difference integrated value ΣΔΔP is equal to or smaller than a first determination value α1 set in advance.
[0036]
More specifically, in a routine that is periodically executed, the difference between the presently detected internal pressure P and the previously detected internal pressure P is obtained as a change amount ΔP every time, and a plurality of change amounts ΔP obtained at different times in the past and the change obtained this time are used. From the amount ΔP, a second-order difference value ΔΔP, which is a change amount of the change amount ΔP over time, is calculated using a preset relational expression. Next, every time the preset determination time elapses, a second-order difference integrated value ΣΔP is calculated by integrating the respective second-order difference values ΔΔP obtained within the determination time.
[0037]
Here, the second-order difference value ΔΔP is a variable reflecting the fluctuation of the internal pressure P based on the fluctuation of the oil level of the fuel stored in the fuel tank 22, and the second-order difference integrated value ΣΔΔP is the oil level of the same fuel. It is a variable that reflects the amount of shaking. Further, the first determination value α1 is determined to be excessive when the internal pressure P due to fuel level fluctuation of the fuel is excessive when the second-order difference integrated value ΣΔΔP exceeds the first determination value α1 at the time of purging. Is set to be able to. The degree of increase in the internal pressure P is set so that it can be determined that the internal pressure P exceeds a limit in which abnormality diagnosis can be performed based on a change state of the internal pressure P in the diagnosis processing.
[0038]
The details of the processing in S10 will be described in detail. When the evaporative fuel is being released from the canister 13 (at the time of purging), the negative pressure introduced into the canister 13 from the intake pipe via the purge pipe 14 via the communication hole 12 a of the differential pressure valve 12. The fuel tank 22 is introduced. At this time, the amount of fluctuation of the internal pressure P is determined by the amount of the fluctuation of the negative pressure according to the operating state of the engine, when the fuel vapor is not discharged and the negative pressure is not introduced to the fuel tank 22 (the purge (When cutting). As a result, as shown in FIG. 3, the second-order difference value ΔΔP obtained from the change amount ΔP of the internal pressure P, and the second-order difference integrated value ΣΔΔP obtained by integrating the second-order difference value ΔΔP, as shown in FIG. It gets bigger by the minute. Accordingly, the first determination value α1 for determining the second-order difference integrated value ΣΔΔP obtained from the internal pressure P detected during the purge corresponds to the variation of the internal pressure P based on the fuel level fluctuation of the fuel according to the running state of the vehicle. It is set based on a value which is larger than the conventional determination value α by an amount affected by the fluctuation of the negative pressure.
[0039]
Further, since the air dust filter 18 having ventilation resistance is provided in the fresh air introduction pipe 16, the larger the purge rate during the purge, the larger the increment value of the second-order difference integrated value ΣΔΔP based on the fluctuation of the intake air. For this reason, the increment value of the second-order difference integrated value ΣΔΔP when the purge rate is 100% is experimentally obtained according to the ventilation resistance of the atmospheric dust filter 18 to be used, and the determination value α is set in a state excluding the influence of the negative pressure. The first determination value α1 is also set based on a value obtained by adding the increment value to the above.
[0040]
Therefore, in this S10, the microcomputer 30 determines whether or not the running state of the vehicle that causes the fuel oil level sway in the purging state is a state in which the abnormality diagnosis of the evaporative fuel purge device 10 can be performed. judge.
[0041]
If the second-order difference integrated value ΣΔΔP has exceeded the determination value α1 in S10, the process ends without executing the diagnostic process.
On the other hand, when the second-order difference integrated value ΣΔΔP is equal to or smaller than the determination value α1 in S10, the purge amount control valve 15 is closed in S11 to interrupt the purge executed in the canister purge control.
[0042]
Next, at S12, a second-order difference value ΔΔP and a second-order difference integrated value ΣΔΔP are obtained from the change amount ΔP of the internal pressure P detected while the purge is suspended, and the second-order difference integrated value ΣΔΔP is set in advance. It is determined whether or not it is equal to or less than a second determination value α2. Further, it is determined whether or not the change amount ΔP1 of the internal pressure P during the elapse of the predetermined determination time T1 is equal to or less than a predetermined determination value β. Then, it is determined whether or not both conditions are satisfied.
[0043]
Here, the second determination value α2 is set to a value smaller than the first determination value α1, and the second-order difference integrated value ΣΔΔP obtained from the internal pressure P detected in a state where the purging is not performed determines the second determination value α2. It is set so that the oil level fluctuation of the fuel can be determined to be excessive by exceeding. Then, the second determination value α2 determines that the degree of increase of the internal pressure P due to the fluctuation of the oil level of the fuel exceeds the limit in which the abnormality diagnosis can be performed based on the change state of the internal pressure P in the diagnosis processing. Is set to be able to.
[0044]
That is, at the time of the purge cut, the negative pressure is not introduced from the intake pipe to the fuel tank 22, and the fluctuation of the internal pressure P does not affect the fluctuation of the internal pressure P. Accordingly, even if the running state of the vehicle does not change, the fluctuation of the internal pressure P is reduced, and the second-order difference integrated value ΣΔP obtained from the internal pressure P is also reduced as shown in FIG. For this reason, the second-order difference integrated value ΔΔΔP obtained from the internal pressure P detected in the purge cut state exceeds the second determination value α2 set to a value smaller than the first determination value α1, so that the internal pressure P abnormally increases. It is determined that the fuel oil level sway has occurred. Therefore, the second determination value α2 is conventionally a determination value α for determining excessive fuel level fluctuation of the fuel based on the second-order difference integrated value ΔΔP obtained from the internal pressure P detected while the purge is interrupted. May be the same as
[0045]
The change amount ΔP1 of the internal pressure P is a variable that reflects the manner in which the fuel temperature of the fuel tank 22 rises. The determination value β is set such that when the change amount ΔP1 exceeds the determination value β, it can be determined that the degree of increase in the fuel temperature according to the vehicle condition is a state that causes an abnormal increase in the internal pressure P. ing. Then, the setting is made so that it can be determined that the state exceeds the limit in which the abnormality diagnosis can be performed based on the change state of the internal pressure P in the diagnosis processing.
[0046]
Therefore, in this S12, in the purge cut state, the microcomputer 30 determines whether the fuel oil level fluctuation state according to the running state of the vehicle and the fuel temperature rise state according to the vehicle state both in the diagnosis processing. It is determined whether or not the state can be performed.
[0047]
When the condition is not satisfied in S12, after the purge is restarted in S13, the abnormality flag is reset in S14, and this processing is ended. On the other hand, when the condition is satisfied in S12, a diagnosis process is executed.
(Diagnosis processing)
As a diagnosis process, the microcomputer 30 opens the purge amount control valve 15 from the closed state and opens the fresh air amount control valve 17 from the open state to close the purge line 14 from the intake pipe in S15. Through the canister 13. Then, a negative pressure is introduced from the canister 13 to the fuel tank 22 through the communication hole 12a of the differential pressure valve 12, and the internal pressure P is reduced to a predetermined first reference value P2 or less as shown in FIG.
[0048]
Next, in S16, the purge amount control valve 15 is closed from the open state while the fresh air amount control valve 17 is closed, and the diagnostic flow path from the purge pipe 14 through the canister 13 to the fuel tank 22 is opened. Seal. Then, as shown in FIG. 3, a predetermined detection time ΔTs elapses from the time when the internal pressure P of the sealed fuel tank 22 rises with the vaporization of the fuel and reaches the first reference value P2 again. The change amount ΔP2 of the internal pressure P during the operation is acquired.
[0049]
Next, in S17, as shown in FIG. 3, the internal pressure P at the time when a predetermined determination time Td has elapsed from the time when the first reference value P2 is reached is equal to or more than the second reference value P3. Is determined.
[0050]
Here, the second reference value P3 and the determination time Td are determined based on the fact that the internal pressure P has increased from the first reference value P2 to exceed the second reference value P3 during the elapse of the determination time Td. It is set so that it can be determined that there is no abnormality in the airtight state of the flow path.
[0051]
More specifically, the internal pressure P reduced to the first reference value P2 gradually increases with time due to the evaporation of fuel in the fuel tank 22. At this time, if there is no pinhole or crack in which the fuel vapor leaks to the outside in the sealed diagnostic flow path, the manner of increasing the internal pressure P depends on the shape of the fuel tank 22, the volume of the diagnostic flow path, etc. It is almost determined by the fixed value. The second reference value P3 and the determination time Td correspond to the second reference value in which the internal pressure P is higher than the first reference value P2 in the fuel vapor purge device 10 in a state where the fuel vapor does not leak from the sealed diagnostic flow path. It is set based on the time required to reach the value P3.
[0052]
Therefore, in S17, the microcomputer 30 determines the airtight state of the diagnostic flow path including the fuel tank 22.
In S17, when the internal pressure P at the time when the determination time Td has elapsed is less than the second reference value P3, the purge is restarted in S13, the abnormality flag is reset in S14, and the present process ends.
[0053]
Therefore, in step S17, when the pinhole or the crack in which the fuel vapor leaks is not detected in the diagnostic flow path including the fuel tank 22, the subsequent processing is not performed, and the discharge of the evaporated fuel from the canister 13 is restarted. Let it.
[0054]
On the other hand, when the internal pressure P at the time when the determination time Td has elapsed is equal to or more than the second reference value P3 in S17, the detection is performed in S18 from the time when the internal pressure P reaches the second reference value P3, as shown in FIG. The change amount ΔP3 of the internal pressure P until the time ΔTs elapses is acquired.
[0055]
Next, in S19, the pressure change rate ΔP2 / ΔP3 is obtained from the change amounts ΔP2 and P3, and the pressure change rate ΔP2 / ΔP3 and the change amount ΔP3 are compared with a map stored in advance to make a diagnosis for sealing. Whether or not there is a pinhole or a crack in which the fuel vapor leaks in the flow path is determined again with higher detection accuracy.
[0056]
Here, the map for collating the second reference value P3 and the pressure change rate ΔP2 / ΔP3 is based on the first reference value P2 in the case where there is a pinhole or a crack through which the fuel vapor leaks in the sealed diagnostic flow path. The second reference value P3 and the pressure change rate ΔP2 / ΔP3, which reflect the difference in the manner of increase of the internal pressure P from to the second reference value P3, are made to correspond two-dimensionally to a normal region, an abnormal region, and a determination suspension region. Things.
[0057]
More specifically, it is known that the manner in which the internal pressure P increases from the first reference value P2 is characterized by the following four conditions. First, as the internal pressure P increases from the first reference value P2, the change amount ΔP gradually decreases. Second, the lower the remaining amount of fuel in the fuel tank 22, the lower the speed at which the internal pressure P rises. Third, when fuel vapor leaks from the diagnostic flow path, the internal pressure P increases linearly and quickly. Fourth, the change amount of the internal pressure P from the first reference value P2 is greater than the change amount when the fuel vapor leaks when the fuel vapor does not leak, but after the internal pressure P increases to a certain value, When the fuel vapor does not leak, the change amount exceeds the change amount when the fuel vapor leaks. Then, each of these characteristic points is replaced with a second reference value P3 and a pressure change rate ΔP2 / ΔP3, and a state where no fuel vapor leaks and a state where no fuel vapor leaks cannot be determined by a combination of these two values. Is determined.
[0058]
Therefore, in S19, the microcomputer 30 determines again the airtight state of the diagnostic flow path including the fuel tank 22.
If it is determined in step S19 that the airtight state of the diagnostic flow path is normal, the purge is restarted in step S13, and then the abnormality flag is reset in step S14, and the process ends.
[0059]
On the other hand, if it is determined in S19 that the airtightness of the diagnostic flow path is abnormal, or if the determination is suspended, an abnormal flag is set in S20, and the process ends.
(Effects of the embodiment)
According to the embodiment described above, the following effects can be obtained.
[0060]
(1) When the internal pressure P is detected while purging is being performed, and the second-order difference integrated value ΣΔΔP obtained from the variation ΔP of the internal pressure P exceeds the first determination value α1, the fuel based on the traveling state of the vehicle is determined. Is determined to be a state in which the fluctuation of the oil level causes an abnormal increase in the internal pressure P. Purging is interrupted only when it is determined that the running state of the vehicle does not cause an abnormal increase in the internal pressure P, and the purging is stopped again based on the running state of the vehicle in a state where the change in the negative pressure does not affect the internal pressure P. An oil level fluctuation of the fuel and an abnormal rise in the fuel temperature according to the vehicle condition are determined. When both of these conditions are satisfied, the airtightness of the diagnostic flow path is inspected from the variation of the internal pressure P with the diagnostic flow path sealed.
[0061]
Therefore, in a situation where the running state of the vehicle is such that the fuel level of the fuel in the fuel tank 22 is severely shaken, and it is not easy to inspect the airtight state of the diagnostic flow path from the change state of the internal pressure P, Purge is not interrupted frequently even though abnormality diagnosis is not executed. For this reason, the time for interrupting the purge can be further reduced as a whole.
[0062]
(2) In the state where the purge is interrupted, it is determined that there is no abnormal fluctuation of the internal pressure P due to the fuel level fluctuation of the fuel based on the running state of the vehicle, and the fuel temperature is increased due to the situation of the vehicle. When it is determined that there is no abnormal change in the internal pressure P, it is determined that the vehicle is in a state in which abnormality diagnosis can be performed. For this reason, the reliability of the diagnostic result of the airtight state of the diagnostic flow path can be further improved, and erroneous diagnosis can be made more difficult to occur.
(Other embodiments)
Hereinafter, embodiments other than the above-described embodiment will be described in an itemized manner.
[0063]
In the diagnostic condition determination processing of the above embodiment, the detection amount for detecting the oil level fluctuation of the fuel that causes an abnormal increase in the internal pressure P is determined by dividing the detected value of the two detected values of the internal pressure P sampled at different sampling periods and gradually changing amounts. The difference value ΔP is used, and the determination is made based on the fact that the difference value ΔP exceeds the determination value.
[0064]
In the diagnosis condition determination processing of the above embodiment, the detection amount for detecting the oil level fluctuation of the fuel that causes an abnormal increase in the internal pressure P is a secondary difference value ΔΔP obtained from the change amount ΔP of the internal pressure P.
[0065]
The method of inspecting the airtight state of the diagnostic flow path in the diagnostic processing of the above embodiment is not limited to the method described in the above embodiment.
In the above embodiment, the internal pressure detecting means is a pressure sensor provided on the vapor pipe 11, the differential pressure valve 12, the canister 13, or a portion of the purge pipe 14 closer to the canister 13 than the purge amount adjusting valve 15.
[0066]
In the above embodiment, the fresh air flow path shutoff means is an electromagnetic on-off valve provided on the fresh air introduction pipe 16 separately from the fresh air flow control valve 17. Further, the purge passage shutoff means is an electromagnetic opening / closing valve provided on the purge pipe 14 separately from the purge amount adjusting valve 15.
(Other technical ideas)
Hereinafter, technical ideas grasped from each of the above embodiments will be described together with their effects.
[0067]
(1) In the invention according to claim 1 or 2, the time-dependent change mode of the internal pressure in a state in which the diagnostic flow path is sealed is determined when the fuel vapor is discharged from the fuel vapor collecting device. Of the internal pressure after the preset first reference value (P2) is reached at a value lower than the internal pressure, and a second reference value (preset at a value higher than the first reference value (P2)). An abnormality diagnosis method for an evaporative fuel purge device, wherein the abnormality is grasped based on a ratio to a change amount of the internal pressure after reaching P3). According to such a configuration, a state in which there is no leakage in the diagnostic flow path and a state in which there is no leakage can be clearly determined, so that the airtight state of the diagnostic flow path can be diagnosed with higher accuracy.
[0068]
(2) In the invention according to any one of claims 3 to 5, the flow path inspection means may determine a timewise change state of the internal pressure in a state where the diagnostic flow path is sealed, by the evaporative fuel. The amount of change in the internal pressure after the preset pressure reaches a first reference value (P2) that is lower than the internal pressure when the fuel vapor is released from the trapping device, and is higher than the first reference value. An abnormality diagnosis device for an evaporative fuel purge device, characterized in that the abnormality is grasped based on a ratio with a change amount of an internal pressure after a predetermined reference value (P3) is reached. According to such a configuration, a state in which there is no leakage in the diagnostic flow path and a state in which there is no leakage can be clearly determined, so that the airtight state of the diagnostic flow path can be diagnosed with higher accuracy.
[0069]
【The invention's effect】
According to the first to fifth aspects of the present invention, the airtight state of the diagnostic flow path is inspected from the state of change of the internal pressure when the running state of the vehicle is a state in which the fuel level vibrates sharply. In such a situation, the emission of fuel vapor is not interrupted frequently even though the abnormality diagnosis is not executed. For this reason, the time for interrupting the purge can be further reduced as a whole.
[Brief description of the drawings]
FIG. 1 is a flowchart of a diagnosis condition determination process performed by an abnormality diagnosis device for an evaporative fuel purge device according to an embodiment.
FIG. 2 is a schematic configuration diagram of an evaporative fuel purge device and an abnormality diagnosis device.
FIG. 3 is a time chart showing a relationship between a purge cut and a second-order difference integrated value and a determination time of a change amount.
FIG. 4 is a time chart in the related art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Evaporated fuel purging apparatus, 11 ... Vapor pipe, 13 ... Charcoal canister as an evaporative fuel collecting apparatus, 14 ... Purge pipe as a purge flow path, 15 ... Purge amount control valve as a purge flow path shutoff means, 16 ... A fresh air introduction pipe as a fresh air introduction flow path, 17 a fresh air flow control valve as a fresh air flow path shutoff means, 19 an electronic control device, 20 an abnormality diagnosis device, 21 a pressure sensor as an internal pressure detection means, 22 .., A fuel tank, 30... A microcomputer as detection amount acquisition means constituting the internal pressure control means, a flow path inspection means and a fuel temperature rise detection means, 31... A drive circuit constituting the internal pressure control means, P.. Amount, ΔΔP: second-order difference value, ΣΔΔP: second-order difference integrated value as detection amount.

Claims

The fuel vapor generated in the fuel tank is collected by the evaporative fuel collecting device via the vapor flow passage, and a negative pressure is introduced from the intake system of the internal combustion engine to the evaporative fuel collecting device via the purge flow passage, and the fresh air is collected. An evaporative fuel purging device that introduces fresh air into the evaporative fuel trap through the introduction flow path and discharges fuel vapor collected by the evaporative fuel trap to the intake system through the purge flow path; In the abnormality diagnosis method,
By detecting both the fresh air introduction flow path and the purge flow path, the internal pressure in the diagnosis flow path sealed including the fuel tank is detected,
A detection amount for detecting the fuel level fluctuation of the fuel is obtained by a preset method from a change amount of the internal pressure detected in a state where the fuel vapor is released from the evaporative fuel collecting device,
It is determined that the fuel level fluctuation that raises the internal pressure in an abnormal manner has occurred when the detection amount exceeds the first determination value set in advance,
When the detected amount does not exceed the first determination value, the detected amount is obtained from a change amount of the internal pressure detected in a state where the release of the fuel vapor from the evaporative fuel collecting device is stopped,
When the detection amount exceeds a second determination value set in advance with a value smaller than the first determination value, it is determined again that the liquid level fluctuation of the fuel that raises the internal pressure in an abnormal manner has occurred,
When the detected amount does not exceed the second determination value, an abnormality diagnosis of the evaporative fuel purge device for diagnosing an airtight state of the diagnostic flow path from a temporal change state of the internal pressure in a state where the diagnostic flow path is sealed. Method.

A determination is made as to whether or not a rise in the fuel temperature has occurred in which the internal pressure is increased in an abnormal manner based on a temporal change in the internal pressure detected in a state where the release of the fuel vapor from the fuel vapor collection device is stopped. And
When it is determined that the liquid level fluctuation of the fuel has not occurred in the internal pressure in an abnormal manner, and that it has been determined that the increase in the fuel temperature to increase the internal pressure in the abnormal manner has not occurred, the diagnostic flow path is determined. 2. The method for diagnosing an abnormality of an evaporative fuel purge device according to claim 1, wherein the airtight state of the diagnostic flow path is diagnosed from a temporal change of the internal pressure in a sealed state.

The fuel vapor generated in the fuel tank is collected by the evaporative fuel collecting device via the vapor flow passage, and a negative pressure is introduced from the intake system of the internal combustion engine to the evaporative fuel collecting device via the purge flow passage. By introducing fresh air into the evaporative fuel collecting device through the air introducing flow passage, the evaporative fuel purging device discharges the fuel vapor collected by the evaporative fuel collecting device to the intake system through the purge flow passage. In the abnormality diagnosis device,
A fresh air flow path blocking means capable of blocking the fresh air introduction flow path,
A purge flow path blocking unit capable of blocking the purge flow path;
Flow path control means for controlling the fresh air flow path opening / closing means and the purge flow path opening / closing means,
Internal pressure detecting means for detecting an internal pressure in a diagnostic flow path that is sealed including the fuel tank by shutting off both the fresh air introduction flow path and the purge flow path,
Detection amount obtaining means for obtaining a detection amount for detecting fuel level fluctuation from a change amount of the internal pressure by a preset method,
The flow path control means is controlled, and the detection amount obtained from the change amount of the internal pressure detected in a state where the fresh air introduction flow path and the purge flow path are not shut off is set to a first determination value set in advance. When exceeding, the purge flow path is shut off without shutting off the fresh air introduction flow path, and the detection amount obtained from the internal pressure detected in this state is set in advance to a value smaller than the first determination value. When the internal pressure is reduced by shutting off the fresh air introduction flow path and not shutting off the purge flow path when the second flow rate exceeds the second determination value, the purge flow path is kept shut off. Internal pressure control means for shutting off and sealing the diagnostic flow path,
An abnormality diagnosis device for an evaporative fuel purge device, comprising: flow path inspection means for inspecting an airtight state of the diagnostic flow path from a change state of the internal pressure in a state where the diagnostic flow path is sealed.

A fuel temperature for detecting an excessive rise in fuel temperature based on a change over time of the internal pressure detected in a state where the internal pressure control means does not block the fresh air introduction flow path but blocks the purge flow path. Equipped with rise detection means,
The internal pressure control means is configured such that the detection amount obtained from the internal pressure detected in a state where the fresh air introduction flow path is not shut off and the purge flow path is shut off does not exceed the second determination value, and the fuel temperature is excessive. 4. The abnormality diagnosis device for an evaporative fuel purge device according to claim 3, wherein when the rise of the fuel pressure is not detected, the internal pressure is decreased without shutting off the fresh air introduction flow passage and without shutting off the purge flow passage.

5. The abnormality diagnosis device for an evaporative fuel purge device according to claim 3, wherein the detection amount is a second-order difference integrated value obtained by integrating a second-order difference value obtained from the change amount of the internal pressure. 6. .