JP4026005B2

JP4026005B2 - Failure diagnosis device for fuel transpiration prevention system

Info

Publication number: JP4026005B2
Application number: JP2003120518A
Authority: JP
Inventors: 健司齋藤; 英嗣金尾
Original assignee: Mitsubishi Motors Corp
Current assignee: Mitsubishi Motors Corp
Priority date: 2003-04-24
Filing date: 2003-04-24
Publication date: 2007-12-26
Anticipated expiration: 2023-04-24
Also published as: JP2004324529A

Description

【０００１】
【発明の属する技術分野】
本発明は、燃料蒸散防止システムの故障診断装置に関し、特に、故障診断中の大気圧変化の影響を受けることなく、同システムでの微量リークや極微量リークによる異常の有無を診断可能な故障診断装置に関する。
【０００２】
【従来の技術】
燃料タンク内で発生した蒸散燃料の大気中への放出を防止すべく、車両には燃料蒸散防止システムが装備される。燃料蒸散防止システムは、キャニスタと、燃料タンクとキャニスタ間に延びパージ弁が介装されたベーパ通路と、キャニスタと内燃機関の吸気通路間に延びるパージ通路とを有しており、燃料タンク内の蒸散燃料をベーパ通路を通してキャニスタに吸着させる一方、所定条件下でパージ弁を開くことにより、キャニスタに吸着された蒸散燃料をパージ通路を通して内燃機関の吸気通路へパージするようになっている。
【０００３】
そして、燃料蒸散防止システムには同システムのリーク異常を検出する故障診断装置が装備される。この故障診断装置は、キャニスタに装着されたベント弁と、燃料タンク内の圧力を検出する圧力センサと、圧力センサからの検出情報を入力すると共にベント弁及びパージ弁を開閉制御する電子制御ユニット（ＥＣＵ）とを備えている。故障診断の際、故障診断装置は、パージ弁を開くと共にベント弁を閉じて、燃料蒸散防止システムの故障診断対象領域である燃料タンク、ベーパ通路及びパージ通路を所定負圧状態とした後にパージ弁を閉じて故障診断対象領域を閉塞した状態で燃料タンク内圧を測定し、タンク内圧の増大量が判定値よりも大きい場合にリーク異常ありと判定するようになっている。
【０００４】
しかしながら、タンク内圧の増大は種々の要因によって生じるので、タンク内圧の増大量と判定値との比較結果に基づいてリーク判定を行うと誤判定のおそれがある。タンク内圧の増大要因のひとつは、燃料タンクに開いた***を介して外気がタンク内に流入することにある。一方、燃料タンクにリークが無くてもタンク内の燃料蒸気飽和度合いが低い場合には、燃料の蒸散によりタンク内圧が上昇する。また、内燃機関からその低圧燃料経路を介して燃料が燃料タンク内へ戻されるが、このリターン燃料も蒸散量の増大要因になり、特にタンク内の燃料残量が少なくなるとリターン燃料によるタンク内での燃料蒸散が顕著になる。さらに、冷間地では秋口から春先にかけて冬季用燃料が使用されるが、冬季用燃料はアルコール分が多くひいては蒸散量が多く、特に温暖な日には燃料蒸散が顕著になる。この様に、故障診断の目安となる燃料タンク内圧の増大要因はリーク穴と燃料蒸散とに大別されるが、正確な故障診断を行うにはタンク内圧の増大要因を的確に判別する必要がある。
【０００５】
そこで、故障診断対象領域を負圧状態にした後に閉鎖条件下で測定されるタンク内圧の増大量が第１判定値を上回った場合に仮の故障判定を行い、次に、故障診断対象領域を大気開放した後に閉塞状態にしてタンク内圧の増大量を測定し、この測定値を第２判定値と比較して最終判定を行うようにしている。すなわち、大気開放後のタンク内圧の増大量が第２判定値よりも小さければリーク穴があると最終判定する一方、タンク内圧の増大が第２判定値よりも大きければ燃料蒸散に起因してタンク内圧が増大したと判断し、仮の故障判定を撤回してリーク穴有無不明（高蒸散判定による診断結果無効）と最終判定するようにしている。
【０００６】
この様な故障診断方法によれば、燃料蒸散に起因したリーク判定上の誤りを低減することができるが、燃料タンク内圧の検出にあたり燃料タンク内外の相対圧を検出する相対圧センサを用いる場合、大気圧変化による誤判定をきたすおそれがある。すなわち、故障診断対象領域での負圧形成後に閉鎖条件下で燃料タンク内圧を測定している間に例えば車両の急勾配登坂走行に伴って燃料タンク外の大気圧が減少変化すると、相対圧センサにより検出される燃料タンク内圧が、大気圧の減少変化分だけ相対的に増大するので、リーク異常が無いにもかかわらず「リーク穴有り」と誤判定することがある。
【０００７】
そこで、特許文献１に記載の診断装置では、診断中に検出される大気圧の変化が所定量以上のときに診断処理を停止もしくは診断結果を無効にし、これにより大気圧変化による誤判定を防止するようにしている。
【０００８】
【特許文献１】
特開平８−２１８９５１号公報
【０００９】
【発明が解決しようとする課題】
特許文献１に記載の診断装置によれば、大気圧変化による誤判定を防止することはできるものの、大気圧が大きく変化した場合には故障診断が行われず、故障診断の頻度がその分少なくなり、燃料蒸散防止システムの異常を適時に検出できなくなるおそれがある。
【００１０】
また、燃料蒸散防止システムでは、近年、微量リークばかりでなく極微量のリークをも防止することが要請されており、この様な要請に応えるためには、同システムの故障診断において微量リークと極微量リークの双方を判別する必要がある。この点、仮判定と最終判定とからなる既述の故障診断を行うことにより、微量リークに関しては誤判定を低減可能であるが、この様な故障診断手法によっても微量リークと極微量リークの双方を確実に判別することは困難である。つまり、極微量リークの主たる要因となる極小リーク穴はその直径が約０．５ｍｍである一方、これまで検出対象とされてきた小リーク穴の直径は約１．０ｍｍであり、この様に種々の大きさのリーク穴を検出対象とする場合、タンク内圧の増大がリーク穴によるものであるか或いは燃料蒸散によるものであるかを的確に判別することはより困難になる。
【００１１】
すなわち、リーク穴に起因するタンク内圧の増大度合いは穴径が小さいほど小さくなるので、極小リーク穴によるタンク内圧増大と燃料蒸散によるタンク内圧増大とを区別するために用いられる第２判定値を小さくする必要があるが、第２判定値を小さく設定すると小リーク穴がある場合は大気開放後の閉塞状態でのタンク内圧の増大量が第２判定値を上回り易くなる。このため、小リーク穴が存在して小リーク穴ありとの仮判定が行われたとしても、大気解放後の閉塞状態でのタンク内圧の増大量が第２判定値を上回ってリーク判定が撤回されることが多くなり、小リーク穴に起因する微量リークを検出することができなくなる。
【００１２】
本発明の目的は、故障診断中の大気圧変化の影響を受けることなく、蒸発燃料蒸散防止システムでの微量リークや極微量リークによる異常を的確に判定できる故障診断装置を提供することにある。
【００１３】
【課題を解決するための手段】
請求項１に記載の故障診断装置では、燃料蒸散防止システムの故障診断対象領域を減圧した後に測定した第１復圧量が第１判定値又はこれより大きな第２判定値を越えた場合、故障診断対象領域に大気圧を導入した後に故障診断対象領域を密閉して第２復圧量を測定し、第１復圧量が第１判定値と第２判定値との間であれば第２復圧量を第３判定値と比較する一方、第１復圧量が第２判定値を越えていれば第２復圧量を第３判定値よりも大きな第４判定値と比較する。そして、第１復圧量が第１判定値を越え且つ第２復圧量が第３判定値を越えないとき、或いは、第１復圧量が第２判定値を越え且つ第２復圧量が第４判定値を越えないときに、蒸発燃料蒸散防止システムを異常と判定する。
【００１４】
リーク穴に起因する第１復圧量の増大度合いはリーク穴径によって変化するので、種々の穴径のリーク穴について燃料蒸散の影響を受けずにリーク穴の有無を判定することは困難であるが、この点、請求項１の故障診断装置では、第１及び第２判定値を極微量リーク及び微量リーク（たとえば、極微量リーク及び微量リークを生起させる極小リーク穴及び小リーク穴）にそれぞれ対応づけて設定すると共に、第３および第４判定値を極微量リーク及び微量リークによる異常と燃料蒸散による異常とを区別可能なようにそれぞれ設定することができ、これにより、極微量リークや微量リークを、復圧量に基づき且つ燃料蒸散による復圧量の増大から区別して的確に判定することができる。
【００１５】
すなわち、第１復圧量が、極微量リークの判定基準である第１判定値を上回り且つ微量リークの判定基準である第２判定値を下回っていれば、極微量リークによる異常が仮判定され、次に、この様な第１復圧量の増大が極微量リークによるものか或いは燃料蒸散によるものであるのかを判別するために第２復圧量が測定される。そして、第２復圧量が第３判定値を越えたときは、燃料蒸散が第１復圧量の増大要因であると判断され、極微量リーク異常の仮判定が撤回されて極微量リーク有無不明（高蒸散判定による診断結果無効）と最終判定される。一方、第２復圧量が第３判定値を越えなければ、極微量リークが第１復圧量の増大要因であると判断されて、極微量リーク異常が最終判定される。
【００１６】
また、第１復圧量が第２判定値を越えたときには微量リークによる異常が仮判定され、次に、第１復圧量の増大要因の判別のために第２復圧量が測定される。そして、第２復圧量が第４判定値を越えた場合は燃料蒸散が第１復圧量の増大要因であると判断されて微量リーク有無不明（高蒸散判定による診断結果無効）と最終判定される一方、第２復圧量が第４判定値を越えない場合には微量リークが第１復圧量の増大要因であると判断されて微量リーク異常ありと最終判定される。
【００１７】
以上のように、請求項１の故障診断装置によれば、極小リーク穴や小リーク穴などに起因する極微量リークや微量リークの有無を的確に判定することができる。
ところで、燃料タンク内外の相対圧を検出する相対圧センサにより燃料タンク内圧を計測する場合、燃料タンク内圧の測定中に大気圧が減少変化すると、相対圧センサにより検出される燃料タンク内圧が大気圧の減少変化分だけ相対的に増大する。その一方、本発明では、第１復圧量が判定値（第１または第２判定値）を越えた場合、リーク異常ありと仮判定すると共に故障診断対象領域への大気導入後に密閉条件下で第２復圧量を測定して、高蒸散判定値（第３または第４判定値）と比較するようにしており、第１復圧量の測定中に大気圧が減少変化した場合には、実際には微量リーク異常がなくても第１復圧量が第１判定値より大きい第２判定値を上回ることがあり、第３判定値より大きい第４判定値が高蒸散判定値として設定されることになる。そして、その後の高蒸散判定において大気圧減少変化がない場合と同一の第４判定値を用いると、第４判定値が大気圧の減少変化分だけ過大であることに起因して、実際には微量リーク異常がないにもかかわらず微量リークありとの誤判定がなされるおそれがある。
【００１８】
この点、請求項１の発明では、第１復圧量の増大要因が微量リークであるか或いは燃料蒸散であるかを判別するための高蒸散判定において、第２復圧量と比較される第４判定値（高蒸散判定値）を、第１復圧量の測定中に大気圧が減少変化した場合に減少補正するので、微量リーク異常ありと不用意に判定するおそれが低減する。
【００１９】
このように、本発明によれば、相対圧センサによる燃料タンク内圧の測定中における大気圧変化の影響を受けることなく、蒸発燃料蒸散防止システムでの微量リーク異常の有無を的確に判定可能であり、従って、例えば急勾配登坂中にもリーク異常の有無を適時に判定することができる。
なお、第１復圧量の測定中に大気圧が減少変化した場合に第３判定値と第４判定値の双方を減少補正するようにしても良く、この場合、蒸発燃料蒸散防止システムにおける微量リークや極微量リークによる異常の有無を大気圧変化の影響を受けずに判定することができる。
【００２０】
請求項２に記載の故障診断装置では、第１復圧量の測定中の大気圧の減少変化量に応じて第４判定値が減少補正される。この好適態様によれば、大気圧が減少変化した場合における第４判定値の減少補正量が大気圧の減少変化量に対応したものになるので、第２復圧量と比較される第４判定値がより適正になり、微量リーク異常の有無をより的確に判定可能になる。なお、第３判定値を第４判定値と同様に減少補正して、極微量リーク異常の有無を的確に判定可能である。
【００２１】
既述のように、本発明では、第１復圧量の増大要因が微量リークであるか燃料蒸散であるかの判別に第４判定値を用いる一方、同要因が極微量リークであるか燃料蒸散であるかを判別する際には第４判定値よりも小さい第３判定値を用いている。
請求項３の発明では、第１復圧量の測定中に大気圧が所定圧以上減少変化した場合に第４判定値を第３判定値に置き換える。この好適態様によれば、大気圧の減少変化の有無に応じて第４判定値として第３判定値または第４判定値自体を選択的に用いるという簡易な構成により、大気圧が減少変化した場合に第４判定値を減少補正して誤判定を防止することができる。
【００２２】
なお、第２復圧量との比較に供される判定値として、第３判定値及び第４判定値に加えて第３判定値より小さい第５判定値を予め設定しておき、第１復圧量の測定中の大気圧が所定圧以上減少変化した場合に第３判定値を第５判定値に置き換えるようにしても良く、これにより、大気圧が減少変化した場合にも極微量リーク異常の有無を簡易な構成で的確に判定可能になる。
【００２３】
請求項４に記載の故障診断装置では、故障診断対象領域を減圧した後に測定された第１復圧量を第１判定値およびこれよりも大きな第２判定値と順次比較し、第１復圧量が第１判定値又は第２判定値よりも大きければ、故障診断対象領域に大気圧を導入した後に同領域を密閉して第２復圧量を測定し、次に、第１復圧量が第１判定値よりも大きく且つ第２判定値よりも小さい場合は第２復圧量を第１復圧量に応じて設定された第３判定値と比較する一方、第１復圧量が第２判定値以上の場合には第２復圧量を第１復圧量に応じて設定された第４判定値と比較し、第１復圧量が第１判定値よりも大きく且つ第２復圧量が第３判定値よりも小さいとき、或いは、第１復圧量が第２判定値よりも大きく且つ第２復圧量が第４判定値よりも小さいときに燃料蒸散防止システムを異常と判定する。
【００２４】
請求項４に記載の故障診断装置によれば、第１復圧量が、極微量リークや微量リークの判定基準となる第１判定値または第２判定値を上回ると、リーク異常が仮判定され、次に、第１復圧量の増大要因の判別のために第２復圧量が計測される。そして、第１復圧量が第１判定値と第２判定値の間にあれば第２復圧量が第３判定値と比較される。第３判定値は、第１復圧量に応じて設定されて極微量リークに適合したものになっており、第２復圧量が第３判定値を上回れば第１復圧量の増大が燃料蒸散によるものであると判断されてリーク異常の仮判定が撤回される一方、第２復圧量が第３判定値を下回れば第１復圧量の増大がリーク異常に起因すると判断され、極微量リークによる異常が最終判定される。これに対して、第１復圧量が第２判定値以上であれば、第２復圧量が、第１復圧量に応じて微量リークに適合するように設定した第４判定値と比較され、第４判定値を上回ればリーク異常の仮判定が撤回される一方、第４判定値を下回れば微量リークによる異常が最終判定される。この様に、第１復圧量に適合した第３判定値および第４判定値を用いて、燃料蒸散による誤判定を防止しつつ極微量リークや微量リークの有無が的確に判別される。
【００２５】
さらに、請求項４に記載の発明では、第１復圧量の測定中に大気圧が減少変化した場合に、第３判定値又は第４判定値を減少補正するようにしている。
この発明では、第１復圧量の測定中に大気圧が減少変化すると、第１復圧量の増大要因の判定（高蒸散判定）のために第２復圧量と比較される第３判定値または第４判定値が減少補正されるので、相対圧センサを用いて燃料タンク内圧（第１復圧量）を測定する場合も、大気圧の減少変化を伴う急勾配登坂などに際して微量リークや極微量リークによる異常の有無を的確に判定可能である。
【００２６】
請求項５に記載の発明では、第１復圧量の測定中の大気圧の減少変化量に応じて第３判定値または第４判定値が減少補正される。この好適態様によれば、第３判定値または第４判定値の減少補正量がより適正になり、微量リークや極微量リークによる異常の有無がより的確に判定される。
【００２７】
【発明の実施の形態】
以下、添付図面を参照して、本発明の故障診断装置について説明する。
故障診断装置が装備される車両用の燃料蒸散防止システムは、図１に示すように、燃料タンク１内の蒸散燃料をベーパ通路２を通してキャニスタ３に吸着させておき、所定のパージ条件が成立したときに、ＥＣＵ１１の制御下で、パージ通路４に設けたパージ弁７を開いて、キャニスタ３内に吸着された蒸散燃料をパージ通路４を通して内燃機関５の吸気通路６へ放出し、これにより蒸散燃料の大気中への放出を防止するようになっている。
【００２８】
本発明の一実施形態に係る故障診断装置は、燃料蒸散防止システムにおけるリーク異常の有無を診断するものであって、キャニスタ３に装着されたベント弁８と、燃料タンク１に装着されタンク内圧を検出する圧力センサ１０と、パージ弁７及びベント弁８を開閉制御するＥＣＵ１１と、ＥＣＵ１１の入力側に接続された大気圧センサ１２とを備えている。圧力センサ１０は、燃料タンク１の内外の相対圧を燃料タンク内圧として検出する相対圧センサから構成されており、圧力センサ１０により検出される燃料タンク内圧は、本装置を搭載した車両の登坂走行に伴って大気圧が減少変化すると、大気圧の減少分増大することになる。
【００２９】
故障診断装置付きの燃料蒸散防止システムにおいて、パージ弁７を開くと共にベント弁８を閉じると、燃料タンク１がベーパ通路２およびパージ通路４を介して吸気通路６と連通するため、吸気通路６内の負圧の作用で燃料タンク１内が減圧される。一方、パージ弁７を閉じると共にベント弁８を開くと、燃料タンク１内は大気圧程度に増圧する。その後、パージ弁７及びベント弁８の双方を閉じると、燃料タンク１内での燃料の蒸散により燃料タンク１内は大気圧以上に増圧する。
【００３０】
故障診断装置のＥＣＵ１１は、例えば車両のイグニッションキーがオンされたコールドスタート時に、図２及び図３に示す故障診断ルーチンを実行する。
故障診断ルーチンのステップＳ１では、ＥＣＵ１１は、始動時冷却水温度及び吸気温度が所定温度以下で、且つ燃料温度が所定温度以下、燃料残量が所定値以内である等の故障診断条件が成立しているか否かを判別する。
【００３１】
ステップＳ１で故障診断条件の不成立が判別されると今回周期における故障診断を終了する。一方、故障診断条件が成立したことをステップＳ１で判別すると、図４に記号ΔＰ１で示すタンク内圧上昇量の測定が行われる（ステップＳ２）。ΔＰ１の測定にあたり、パージ弁７が閉じると共にベント弁８が開いて燃料蒸散防止システムの故障診断対象領域が大気開放される。この際、パージ弁７を徐々に閉じるようにしても良い。そして、大気開放状態におけるタンク内圧Ｐ１を表す圧力センサ１０の出力が読み込まれる。タンク内圧Ｐ１の測定後、ベント弁８を閉じると、図４に示すようにタンク内圧が時間経過につれて増大する。
【００３２】
そして、タンク内圧Ｐ１の測定時点から所定時間Ｔ１が経過したときに圧力センサ１０の出力が読み込まれ、当該時点でのタンク内圧Ｐ２が測定される。次に、タンク内圧Ｐ１、Ｐ２からタンク内圧上昇量ΔＰ１が算出され、これによりステップＳ２でのΔＰ１の測定を終了する。
次のステップＳ３ではステップＳ２で求めたタンク内圧上昇量ΔＰ１が高蒸散判定値Ｌ１よりも小さいか否かが判定され、この判定結果が否定であれば燃料蒸散過大のため正確な故障診断不能と判断して（ステップＳ３ａ）、故障診断を終了する。
【００３３】
一方、タンク内圧上昇量ΔＰ１がリーク判定値Ｌ１以下であれば、更なる故障判定が行われる。このため、先ず、図２のステップＳ４において、パージ弁７を開いて故障診断対象領域を減圧し、圧力センサ１０により検出される圧力が図４に記号Ｐ３で示す所定負圧値に達したときにパージ弁７を閉じて故障診断対象領域を閉塞状態とする。閉塞状態の故障診断対象領域では、燃料タンク１内での燃料の蒸発あるいはリークにより、図４に示すようにタンク内圧が時間経過につれて増大する。そして、パージ弁７を閉じた時点から所定時間Ｔ２が経過したときに当該時点でのタンク内圧Ｐ４を表す圧力センサ１０の出力が読み込まれ、タンク内圧Ｐ３、Ｐ４から第１復圧量としてのタンク内圧上昇量ΔＰが算出される。
【００３４】
次のステップＳ５では、ステップＳ４で算出した第１復圧量ΔＰが、主に極小リーク穴に起因して生起する極微量リークの判定に適した第１判定値Ｌ１１よりも大きいか否かが判定され、この判別結果が否定であればリーク異常なしと判断して（ステップＳ５ａ）、故障診断を終了する。
一方、第１復圧量ΔＰが第１判定値Ｌ１１よりも大きければ、第１復圧量ΔＰが、主に小リーク穴に起因して生起する微量リークの判定に適した第２判定値Ｌ１２よりも大きいか否かが判定される（ステップＳ６）。そして、ステップＳ６での判定結果が肯定であれば、第１復圧量ΔＰが第２判定値Ｌ１２を越えた回数を表すフラグＦの値を「１」だけインクリメントし（ステップＳ７）、次に、制御フローがステップＳ８へ移行する。一方、ステップＳ６での判別結果が否定すなわち第１復圧量ΔＰが第２判定値Ｌ１２を下回ればステップ６からステップＳ８へ移行する。
【００３５】
ステップＳ８では、フラグＦｂｐが、第１復圧量ΔＰの測定中の大気圧ＢＰの減少変化量ΔＢＰが所定量ＢＰａ以上であったことを表す値「１」であるか否かが判別され、このステップＳ８での判別結果が肯定（フラグＦｂｐ＝１）であれば制御フローは図３のステップＳ１２へ移行する。
一方、ステップＳ８での判別結果が否定（Ｆｂｐ≠１）、すなわち前回までのΔＰ測定中に大気圧が減少変化しなかったことが判別された場合には、今回のΔＰ測定中に大気圧減少変化があったか否かを判別する。このため、タンク内圧が所定負圧Ｐ３に到達したときに大気圧センサ１２により検出され且つメモリに一時記憶された大気圧ＢＰ１と所定負圧Ｐ３への到達時点から所定時間Ｔ２が経過したときに検出されて一時記憶された大気圧ＢＰ２とをメモリから読み出し、ＢＰ１からＢＰ２を減じて大気圧減少変化量ΔＢＰを求め、さらに、変化量ΔＢＰが所定量ＢＰａ以上であるか否かを判別する（ステップＳ９）。そして、第１復圧量ΔＰの測定中に所定量ＢＰａ以上の大気圧減少変化があったことを判別した場合にはフラグＦｂｐを値１にセットし（ステップＳ１０）、その様な大気圧減少変化がなかった場合にはフラグＦｂｐを値０にリセットする（ステップＳ１１）。
【００３６】
ステップＳ８、Ｓ１０またはＳ１１に続くステップＳ１２では、第１復圧量ΔＰの測定回数Ｎを「１」だけインクリメントし、次に、測定回数Ｎが「３」に等しいか否かを判定する（ステップＳ１３）。第１復圧量ΔＰの測定回数が３回に満たなければ、図２のステップＳ４に移行して第１復圧量ΔＰを再度測定する。そして、第１復圧量ΔＰを３回にわたって測定すると、ステップＳ１３での判定結果が肯定になり、次のステップＳ１４ではフラグＦの値が「３」であるか否かが判定される。
【００３７】
ステップＳ１４の判別結果が否定、すなわち３度測定された第１復圧量ΔＰのいずれかが第２判定値Ｌ１２を下回ったと判別すると、主に極小リーク穴に起因する極微量リークがあることを仮に判定し、後述の高蒸散判定で用いられる判定値Ｌを、極微量リークと高蒸散とを区別するのに適した第３判定値Ｌ２１に設定する（ステップＳ１６）。
【００３８】
これに対して、３度測定された第１復圧量ΔＰのいずれもが第２判定値Ｌ１２を越えていたことがステップＳ１４で判別されると、次のステップＳ１５ではフラグＦｂｐが値１であるか否かが判別される。
ステップＳ１５での判別結果が否定、すなわち、第１復圧量ΔＰを３度測定している間に大気圧が所定量ＢＰａ以上減少変化しなかった場合には、主に小リーク穴に起因する微量リークがあることを仮に判定し、高蒸散判定値Ｌを、微量リークと高蒸散とを区別するのに適した第４判定値Ｌ２２に設定する（ステップＳ１７）。一方、ステップＳ１５での判別結果が肯定、すなわち３度にわたる第１復圧量ΔＰの測定中に所定量ＢＰａ以上の大気圧減少変化が１度でも検出されたことを判別すると、ステップＳ１４で第１復圧量ΔＰが大であって微量リークの可能性があると判定されたにもかかわらず、高蒸散判定値Ｌを微量リーク判定に適した第４判定値Ｌ２２よりも小さい第３判定値Ｌ２１に設定する（ステップＳ１５）。
【００３９】
すなわち、ΔＰ測定中に急勾配登坂走行などに起因して大気圧ＢＰが所定圧以上減少変化した場合には、相対圧センサからなる圧力センサ１０による燃料タンク内圧の測定値が、図４に一点鎖線で示すタンク内圧変化曲線から実線で示す曲線へ向かって白抜き矢印で示すように相対的に増大するので、大気圧減少変化を伴わない平地走行時の高蒸散判定値と同一の判定値Ｌを用いて高蒸散判定を行うと、判定値Ｌが大気圧減少変化分だけ過大になって、実際にはリーク異常がないにもかかわらずリーク異常ありと誤判定するおそれがある。
【００４０】
この点、第１復圧量が大であっても大気圧の減少変化時に上記ステップＳ１５において、図４に太い下向き矢印で示すと共に図５に示すように、第４判定値Ｌ２２を第３判定値Ｌ２１に置き換えると、第４判定値Ｌ２２が減少補正されて誤判定を回避することができる。
故障診断ルーチンのステップＳ１８では、パージ弁７を閉じると共にベント弁８を開いて故障診断対象領域を大気開放し、この大気開放状態におけるタンク内圧Ｐ５が圧力センサ１０により測定された後でベント弁８を閉じて故障診断対象領域を閉塞状態にする。この閉塞状態ではタンク内圧が図４に示すように時間経過につれて増大する。そして、タンク内圧Ｐ５の測定が終了した時点から所定時間Ｔ３が経過したときに圧力センサ１０の出力を読み込み、当該時点のタンク内圧Ｐ６を測定し、タンク内圧Ｐ５、Ｐ６から第２復圧量としての再ΔＰ１を算出する。
【００４１】
次のステップＳ１９では再ΔＰ１が、ステップＳ１６またはＳ１７で設定された判定値Ｌよりも大きいか否かが判定され、この判定結果が否定であればステップＳ２０でリークありとの最終判定がなされる一方、ステップＳ１９での判定結果が肯定であれば、第１復元量ΔＰの増大が高蒸散によるものであるのでリークありとの仮判定を撤回すべきと判断し（ステップＳ２１）、リーク判定を行うことなしに故障診断を終了する。ここで、大気圧減少変化時には最終判定に用いられる第４判定値Ｌ２２が既述のように減少補正されるので、同判定値が大気圧減少変化分だけ過剰であることに起因してリーク異常ありと誤判定するおそれが低減する。なお、ステップＳ２０でリークありと判定された場合は、警報ランプや警報ブザーなどを用いてリーク判定結果を通知する。
【００４２】
以上を要約すれば、本実施形態では、第１及び第２判定値Ｌ１１、Ｌ１２が極微量リーク及び微量リークにそれぞれ対応づけて設定され、また、第３及び第４判定値Ｌ２１、Ｌ２２が極微量リーク及び微量リークによる異常と燃料蒸散による異常とを区別可能なようにそれぞれ設定される。そして、第１復圧量ΔＰが、極微量リークの判定基準である第１判定値Ｌ１１を上回り且つ微量リークの判定基準である第２判定値Ｌ１２を下回っていれば、極微量リークによる異常が仮判定され、次に、この様な第１復圧量の増大が極微量リークによるものか或いは過大な燃料蒸散によるものであるのかを判別するために第２復圧量（再ΔＰ１）が測定される。そして、第２復圧量が第３判定値Ｌ２１を越えたときは、燃料蒸散が第１復圧量ΔＰの増大要因であると判断され、極微量リーク異常の仮判定が撤回されて極微量リーク有無不明（高蒸散判定による診断無効）と最終判定される。一方、第２復圧量が第３判定値を越えなければ、極微量リークが第１復圧量の増大要因であると判断されて、極微量リーク異常が最終判定される。また、第１復圧量ΔＰが第２判定値Ｌ１２を越えたときには微量リークによる異常が仮判定され、次に、第１復圧量の増大要因の判別のために第２復圧量（再ΔＰ１）が測定され、第２復圧量が第４判定値Ｌ２２を越えた場合は燃料蒸散が第１復圧量ΔＰの増大要因であると判断されて微量リーク有無不明（高蒸散判定による診断無効）と最終判定される一方、第２復圧量が第４判定値Ｌ２２を越えない場合には微量リークが第１復圧量の増大要因であると判断されて微量リーク異常ありと最終判定される。この様にして、極微量リークや微量リークを的確に判定することができる。
【００４３】
また、本実施形態では、燃料タンク内圧Ｐ１〜Ｐ６の測定に燃料タンク内外の相対圧を検出する圧力センサ１０を用いるので、タンク内圧測定中に大気圧が減少変化すると大気圧の減少変化分だけ測定値が相対的に増大してリーク判定に誤りが生じるおそれがあるが、ΔＰ測定中に大気圧が所定量ＢＰａ以上減少変化した場合には、その後の高蒸散判定において第２復圧量（再ΔＰ１）と比較される第４判定値Ｌ２２を減少補正するので、微量リーク異常の有無を的確に判定することができ、ΔＰ測定中の大気圧変化の影響を受けることなく微量リーク異常を判定することができる。また、第４判定値Ｌ２２の減少補正を、第４判定値Ｌ２２を第３判定値Ｌ２１に置き換えることにより行うので、リーク判定に係る構成や判定手順が簡易になる。
【００４４】
付言すれば、故障診断装置のＥＣＵ１１は、故障診断対象領域の減圧後に測定した第１復圧量ΔＰを第１判定値Ｌ１１または第２判定値Ｌ１２と比較する第１診断手段として機能し、また、故障診断対象領域を大気開放した後に閉塞した状態で測定した第２復圧量（再ΔＰ１）を第３判定値Ｌ２１または第４判定値Ｌ２２と比較する第２診断手段として機能し、第１及び第２復圧量に基づいて燃料蒸散防止システムの異常を判定する異常判定手段として機能し、さらには、大気圧ＢＰが減少変化した場合に第４判定値Ｌ２２を減少補正する補正手段として機能する。
【００４５】
さて、本発明者らは、上記実施形態による故障診断装置を装備した燃料蒸散防止システムを製作し、第１〜第４判定値Ｌ１１、Ｌ１２、Ｌ２１及びＬ２２を設定して故障診断精度を評価した。図６は燃料タンク１内の燃料残量が４０〜８５％の場合についての故障診断結果を示し、図７は燃料残量が１５〜４０％の場合についての故障診断結果を示す。図６及び図７中、○マークはリークなしの燃料蒸散防止システムについての診断結果を示し、●マークは、極微量リークを生起させる０．５ｍｍ径の極小リーク穴を設けた燃料蒸散防止システムに係る診断結果を示し、△マークは、微量リークを生起させる１．０ｍｍ径の小リーク穴を設けた燃料蒸散防止システムに係る診断結果を示す。
【００４６】
図６から分かるように、リークなしの燃料蒸散防止システムでは、○マークで示すように、第１復圧量ΔＰが第１判定値Ｌ１１を下回る場合が多いので殆どが正しく正常判定され、また、第１復圧量ΔＰが第１判定値Ｌ１１を上回る場合は再ΔＰ１が第３判定値Ｌ２１又は第４判定値Ｌ２２を上回って高蒸散判定される。すなわち、第１復圧量ΔＰと再ΔＰ１との間に相関があって、第１復圧量ΔＰが増大するにつれて再ΔＰ１が増大するので、リーク判定されることはなかった。図６中に楕円領域で示す場合については第１判定値Ｌ１１を燃料温度と燃料残量に応じて可変設定することにより正常判定可能である。極小リーク穴のあるシステムでは、●マークで示すように、殆どの場合は正しくリーク判定されるが、燃料蒸散が大きい場合には高蒸散判定されることもあった。小リーク穴のあるシステムでは、△マークで示すように殆どの場合、正しくリーク判定され、特に図６中に円領域で示すように、第１復圧量ΔＰが第２判定値Ｌ１２を上回る場合については第２復圧値（再ΔＰ１）に係る判定基準値として第３判定値Ｌ２１よりも大きい第４判定値Ｌ２２を用いることにより正しくリーク判定されることが明らかになった。
【００４７】
図７から分かるように、燃料残量が少ない場合にも図６の場合と同様の故障診断精度が得られ、特に、図７に円領域で示すように第４判定値Ｌ２２を用いる効果が顕著に現れている。この様に、故障診断装置は、低燃料量域での故障診断にも好適することが分かった。ただし、図７に楕円領域で示すように極小リークを高蒸散判定する場合があった。
【００４８】
以上で本発明の一実施形態の説明を終えるが、本発明は上記実施形態に限定されず、種々に変形可能である。
例えば、上記実施形態では、３度にわたるΔＰ測定中に所定量ＢＰａ以上の大気圧減少変化が１度でも検出された場合に第４判定値Ｌ２２を減少補正するようにしたが、大気圧の減少変化が複数回検出された場合、或いは、３度のΔＰ測定中の大気圧減少変化量の最大値、最小値または平均値が所定量ＢＰａを上回った場合に、減少補正を行うようにしてもよい。なお、ΔＰ測定は３回に限定されない。
【００４９】
また、大気圧減少変化量ΔＢＰが所定量ＢＰａ以上である場合に、高蒸散判定値Ｌを図５に示すようにＬ２２からＬ２１にステップ状に減少補正することは必須ではなく、たとえば、図８に示すように大気圧減少変化量ΔＢＰが増大するにつれて値１から減少する補正係数ＫＬを判定値Ｌに乗じることにより、判定値Ｌを減少補正するようにしてもよい。
【００５０】
また、上記実施形態では大気圧減少変化時に第４判定値Ｌ２２のみを減少補正するようにしたが、第３判定値Ｌ２１および第４判定値Ｌ２２の双方を補正してもよい。この際、各判定値を、図５に示すように所定量ＢＰａにおいてステップ状に補正し、または複数の所定量のそれぞれにおいてステップ状に補正し、或いは図８に示すように漸減補正することができる。
【００５１】
さらに、上記実施形態では第３判定値Ｌ２１および第４判定値Ｌ２２を第１復圧量ΔＰの値にかかわらず一定としたが、両判定値Ｌ２１、Ｌ２２を第１復圧量ΔＰに応じて可変設定し、または、両判定値のうち第２復圧量（再ΔＰ１）と比較されるものをΔＰに応じて可変設定するようにしてもよい。この変形例においても、ΔＰ測定中に所定圧以上の大気圧減少変化があった場合には第３判定値Ｌ２１または第４判定値Ｌ２２あるいは両判定値を減少補正し、好ましくは、大気圧の減少変化量に応じて減少補正する。
【００５２】
その他、本発明はその発明概念の範囲内で種々に変形可能である。
【００５３】
【発明の効果】
請求項１、４に記載の故障診断装置では、燃料蒸散防止システムの故障診断対象領域を減圧した後に測定した第１復圧量が第１判定値又はこれより大きな第２判定値を越えた場合、故障診断対象領域に大気圧を導入した後に故障診断対象領域を密閉して第２復圧量を測定し、第１復圧量が第１判定値と第２判定値との間であれば第２復圧量を第３判定値と比較する一方、第１復圧量が第２判定値を越えていれば第２復圧量を第３判定値よりも大きな第４判定値と比較し、第１復圧量が第１判定値を越え且つ第２復圧量が第３判定値を越えないとき、或いは、第１復圧量が第２判定値を越え且つ第２復圧量が第４判定値を越えないときに、蒸発燃料蒸散防止システムを異常と判定するので、極小リーク穴や小リーク穴などに起因する極微量リークや微量リークの有無を過大な燃料蒸散による誤判定を防止しつつ的確に判定することができる。請求項４の発明では、第３判定値および第４判定値を第１復圧量に応じて極微量リークおよび微量リークにそれぞれ適合したものにするので、より的確にリーク判定を行うことができる。
【００５４】
また、請求項１の発明では、第１復圧量の測定中に大気圧が減少変化した場合、第１復圧量の増大要因を判別するために第２復圧量と比較される第４判定値を減少補正するので、燃料タンク内外の相対圧を検出する相対圧センサを用いて検出された燃料タンク内圧に基づいて第１および第２復圧量を測定する故障診断装置にあっても、燃料タンク内圧の測定中における大気圧変化の影響を受けることなく、蒸発燃料蒸散防止システムでの微量リークによる異常の有無を的確に判定することができる。請求項４の発明では、大気圧減少変化時に第３判定値または第４判定値を減少補正するので、極微量リークや微量リークによる異常の有無を大気圧変化の影響を受けずに的確に判定可能である。
【００５５】
請求項２、５に記載の故障診断装置では、第１復圧量の測定中の大気圧の減少変化量に応じて第４判定値を減少補正しあるいは第３判定値または第４判定値を減少補正するので、第４判定値の減少補正量、あるいは第３判定値または第４判定値の減少補正量が大気圧の減少変化量に対応したものになり、第２復圧量と比較される第４判定値、あるいは第３判定値または第４判定値を、より適正にすることができ、微量リーク異常の有無をより的確に判定することができる。
【００５６】
請求項３の発明では、第１復圧量の測定中に大気圧が所定圧以上減少変化した場合に第４判定値を第３判定値に置き換えるので、大気圧減少変化時の第４判定値の減少補正を、判定値の置き換えという簡易な構成により行うことができる。
【図面の簡単な説明】
【図１】本発明の第１実施形態による故障診断装置を装備した燃料蒸散防止システムの概略図である。
【図２】図１に示したＥＣＵが実施する故障診断ルーチンの一部を示すフローチャートである。
【図３】図２に続く故障診断ルーチンの残部を示すフローチャートである。
【図４】故障診断中の燃料タンク内圧の、時間経過に伴う変化を示す図である。
【図５】図２および図３に示した故障診断ルーチンで用いられる高蒸散判定値Ｌと第１復圧量ΔＰの計測中の大気圧減少変化量ΔＢＰとの関係を示す図である。
【図６】燃料残量が多い場合における本発明の故障診断装置による故障診断精度を示す図である。
【図７】燃料残量が少ない場合についての故障診断精度を示す図である。
【図８】本発明の変形例に係る故障診断ルーチンでの高蒸散判定値Ｌの設定に用いられる補正係数ＫＬと大気圧減少変化量ΔＢＰとの関係を示す図である。
【符号の説明】
１燃料タンク
２ベーパ通路
３キャニスタ
４パージ通路
５内燃機関
６吸気通路
７パージ弁
８ベント弁
１０圧力センサ
１１ＥＣＵ（第１、第２診断手段、異常判定手段、補正手段）
１２大気圧センサ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a failure diagnosis apparatus for a fuel transpiration prevention system, and in particular, a failure diagnosis capable of diagnosing the presence or absence of an abnormality due to a minute leak or a minute amount leak in the system without being affected by a change in atmospheric pressure during the failure diagnosis. Relates to the device.
[0002]
[Prior art]
The vehicle is equipped with a fuel transpiration prevention system in order to prevent the transpiration fuel generated in the fuel tank from being released into the atmosphere. The fuel transpiration prevention system has a canister, a vapor passage extending between the fuel tank and the canister and having a purge valve interposed therein, and a purge passage extending between the canister and the intake passage of the internal combustion engine. While the vaporized fuel is adsorbed to the canister through the vapor passage, the vaporized fuel adsorbed to the canister is purged to the intake passage of the internal combustion engine through the purge passage by opening the purge valve under a predetermined condition.
[0003]
The fuel transpiration prevention system is equipped with a failure diagnosis device that detects a leakage abnormality of the system. This failure diagnosis apparatus includes a vent valve mounted on a canister, a pressure sensor for detecting pressure in the fuel tank, and an electronic control unit for inputting detection information from the pressure sensor and controlling opening / closing of the vent valve and purge valve ( ECU). At the time of failure diagnosis, the failure diagnosis device opens the purge valve and closes the vent valve so that the fuel tank, the vapor passage and the purge passage, which are the failure diagnosis target areas of the fuel evaporation prevention system, are in a predetermined negative pressure state. The fuel tank internal pressure is measured in a state where the failure diagnosis target region is closed and the increase in the tank internal pressure is larger than the determination value, and it is determined that there is a leak abnormality.
[0004]
However, since the increase in the tank internal pressure is caused by various factors, there is a risk of erroneous determination if the leak determination is performed based on the comparison result between the increase amount of the tank internal pressure and the determination value. One factor for increasing the tank internal pressure is that outside air flows into the tank through a small hole opened in the fuel tank. On the other hand, even if there is no leak in the fuel tank, if the degree of fuel vapor saturation in the tank is low, the tank internal pressure will increase due to fuel evaporation. In addition, the fuel is returned from the internal combustion engine to the fuel tank through the low-pressure fuel path. This return fuel also increases the transpiration amount, and particularly when the remaining fuel amount in the tank decreases, The fuel transpiration becomes remarkable. Further, in cold regions, winter fuel is used from the beginning of autumn to early spring, but winter fuel has a high alcohol content and a large amount of transpiration, and fuel transpiration is particularly noticeable on warm days. In this way, the increase factor of the fuel tank internal pressure, which is a guideline for failure diagnosis, is roughly divided into leak holes and fuel evaporation, but it is necessary to accurately determine the increase factor of the tank internal pressure to perform accurate failure diagnosis. is there.
[0005]
Therefore, a temporary failure determination is performed when the increase amount of the tank internal pressure measured under the closed condition after the failure diagnosis target region is set to a negative pressure state exceeds the first determination value, and then the failure diagnosis target region is After opening to the atmosphere, the tank is closed and the amount of increase in the tank internal pressure is measured, and this measurement value is compared with the second determination value to make a final determination. That is, if the increase amount of the tank internal pressure after opening to the atmosphere is smaller than the second determination value, it is finally determined that there is a leak hole, while if the increase of the tank internal pressure is larger than the second determination value, the tank is caused by fuel evaporation. It is determined that the internal pressure has increased, the provisional failure determination is withdrawn, and the final determination is made that the leak hole presence / absence is unknown (diagnosis result invalid due to high transpiration determination).
[0006]
According to such a failure diagnosis method, it is possible to reduce an error in leak determination due to fuel transpiration, but when using a relative pressure sensor that detects a relative pressure inside and outside the fuel tank in detecting the fuel tank internal pressure, There is a risk of misjudgment due to changes in atmospheric pressure. That is, when the pressure inside the fuel tank is measured under closed conditions after the negative pressure is formed in the failure diagnosis target area, for example, when the atmospheric pressure outside the fuel tank decreases and changes as the vehicle travels uphill, the relative pressure sensor Since the internal pressure of the fuel tank detected by the above increases relatively by the amount of decrease in atmospheric pressure, it may be erroneously determined that there is a leak hole even though there is no leak abnormality.
[0007]
Therefore, in the diagnostic device described in Patent Document 1, when the change in atmospheric pressure detected during diagnosis is greater than or equal to a predetermined amount, the diagnosis process is stopped or the diagnosis result is invalidated, thereby preventing erroneous determination due to atmospheric pressure change. Like to do.
[0008]
[Patent Document 1]
JP-A-8-218951
[0009]
[Problems to be solved by the invention]
According to the diagnostic device described in Patent Document 1, although erroneous determination due to changes in atmospheric pressure can be prevented, failure diagnosis is not performed when the atmospheric pressure changes greatly, and the frequency of failure diagnosis is reduced accordingly. There is a risk that the abnormality of the fuel transpiration prevention system cannot be detected in a timely manner.
[0010]
In recent years, fuel evaporation prevention systems have been required to prevent not only trace amounts of leaks but also trace amounts of leaks. It is necessary to discriminate both of the trace leaks. In this respect, it is possible to reduce misjudgment regarding trace leakage by performing the above-described failure diagnosis consisting of provisional judgment and final judgment. It is difficult to reliably discriminate. In other words, the diameter of the small leak hole, which is the main cause of the very small amount of leak, is about 0.5 mm, while the diameter of the small leak hole that has been the detection target so far is about 1.0 mm. When a leak hole having a size of 2 is set as a detection target, it becomes more difficult to accurately determine whether the increase in tank internal pressure is due to the leak hole or fuel evaporation.
[0011]
That is, the degree of increase in the tank internal pressure due to the leak hole decreases as the hole diameter decreases, so the second judgment value used to distinguish between the tank internal pressure increase due to the minimal leak hole and the tank internal pressure increase due to fuel evaporation is reduced. However, if the second determination value is set small, if there is a small leak hole, the increase amount of the tank internal pressure in the closed state after opening to the atmosphere will easily exceed the second determination value. For this reason, even if a small leak hole exists and a provisional determination is made that there is a small leak hole, the increase in the tank internal pressure in the closed state after release to the atmosphere exceeds the second determination value, and the leak determination is withdrawn. In many cases, a small amount of leak due to a small leak hole cannot be detected.
[0012]
An object of the present invention is to provide a failure diagnosis device that can accurately determine an abnormality due to a minute leak or a very small amount leak in an evaporated fuel transpiration prevention system without being affected by a change in atmospheric pressure during failure diagnosis.
[0013]
[Means for Solving the Problems]
In the failure diagnosis apparatus according to claim 1, when the first return pressure measured after depressurizing the failure diagnosis target area of the fuel transpiration prevention system exceeds a first determination value or a second determination value larger than this, After the atmospheric pressure is introduced into the diagnosis target area, the failure diagnosis target area is sealed and the second return pressure is measured. If the first return pressure is between the first determination value and the second determination value, the second return pressure is measured. While the return pressure amount is compared with the third determination value, if the first return pressure amount exceeds the second determination value, the second return pressure amount is compared with a fourth determination value that is larger than the third determination value. Then, when the first return pressure amount exceeds the first determination value and the second return pressure amount does not exceed the third determination value, or the first return pressure amount exceeds the second determination value and the second return pressure amount. Does not exceed the fourth determination value, it is determined that the evaporated fuel transpiration prevention system is abnormal.
[0014]
Since the degree of increase in the first return pressure due to the leak hole varies depending on the leak hole diameter, it is difficult to determine the presence or absence of a leak hole without being affected by fuel evaporation for leak holes of various hole diameters. However, in this point, the failure diagnosis apparatus according to claim 1 uses the first and second determination values for a very small leak and a very small leak (for example, a very small leak hole and a small leak hole that cause a very small leak and a very small leak), respectively. In addition to being set in correspondence, the third and fourth judgment values can be set so as to be able to distinguish between abnormalities caused by trace leaks and trace leaks, and abnormalities caused by fuel evaporation. Leakage can be accurately determined based on the amount of return pressure and distinguished from an increase in return pressure due to fuel evaporation.
[0015]
In other words, if the first return pressure amount exceeds the first determination value that is the determination criterion for the trace leak and is lower than the second determination value that is the determination criterion for the trace leak, an abnormality due to the trace leak is provisionally determined. Next, the second return pressure is measured in order to determine whether the increase in the first return pressure is due to a very small amount of leak or due to fuel evaporation. When the second return pressure exceeds the third determination value, it is determined that the fuel transpiration is an increase factor of the first return pressure, and the provisional determination of the extremely small amount of leak abnormality is withdrawn, and the presence or absence of the very small amount of leak is determined. It is finally judged as unknown (diagnostic result is invalid due to high transpiration determination). On the other hand, if the second return pressure amount does not exceed the third determination value, it is determined that a very small amount of leak is an increase factor of the first return pressure amount, and a very small amount of leak abnormality is finally determined.
[0016]
Further, when the first return pressure amount exceeds the second determination value, an abnormality due to a slight leak is provisionally determined, and then the second return pressure amount is measured in order to determine the increase factor of the first return pressure amount. . When the second recuperation amount exceeds the fourth determination value, it is determined that the fuel transpiration is an increase factor of the first recuperation amount, and the final determination is made that the presence or absence of a slight leak is unknown (the diagnosis result is invalid due to the high transpiration determination). On the other hand, when the second return pressure amount does not exceed the fourth determination value, it is determined that the slight leak is an increase factor of the first return pressure amount, and it is finally determined that there is a slight leak abnormality.
[0017]
As described above, according to the failure diagnosis apparatus of the first aspect, it is possible to accurately determine the presence or absence of a very small amount of leak or a small amount of leak due to a very small leak hole or a small leak hole.
By the way, when the fuel tank internal pressure is measured by a relative pressure sensor that detects the relative pressure inside and outside the fuel tank, if the atmospheric pressure decreases and changes during the measurement of the fuel tank internal pressure, the fuel tank internal pressure detected by the relative pressure sensor becomes the atmospheric pressure. Relatively increases by the amount of change of decrease. On the other hand, in the present invention, when the first return pressure exceeds the determination value (first or second determination value), it is temporarily determined that there is a leak abnormality and the air is introduced into the failure diagnosis target area under the sealed condition. The second return pressure is measured and compared with the high transpiration judgment value (third or fourth judgment value), and when the atmospheric pressure decreases during the measurement of the first return pressure, In fact, even if there is no minute leak abnormality, the first return pressure amount may exceed the second determination value that is larger than the first determination value, and the fourth determination value that is larger than the third determination value is set as the high transpiration determination value. Will be. Then, when the same fourth determination value is used as in the case where there is no change in atmospheric pressure in the subsequent high transpiration determination, the fourth determination value is actually excessive by the amount corresponding to the decrease in atmospheric pressure. There is a risk of erroneous determination that there is a trace leak despite no trace leak abnormality.
[0018]
In this regard, in the first aspect of the present invention, in the high transpiration determination for determining whether the increase factor of the first return pressure amount is a slight leak or fuel evaporation, the first return pressure amount is compared with the second return pressure amount. Since the 4 determination value (high transpiration determination value) is corrected to decrease when the atmospheric pressure decreases during the measurement of the first return pressure, the possibility of inadvertently determining that there is a slight leak abnormality is reduced.
[0019]
Thus, according to the present invention, it is possible to accurately determine the presence or absence of a slight leak abnormality in the evaporated fuel transpiration prevention system without being affected by atmospheric pressure changes during measurement of the fuel tank internal pressure by the relative pressure sensor. Therefore, for example, the presence or absence of a leak abnormality can be determined in a timely manner even during a steep climb.
If the atmospheric pressure decreases during the measurement of the first return pressure, both the third determination value and the fourth determination value may be corrected to decrease. In this case, a slight amount in the evaporated fuel transpiration prevention system may be used. It is possible to determine whether there is an abnormality due to a leak or a very small amount of leak without being affected by changes in atmospheric pressure.
[0020]
In the failure diagnosis apparatus according to the second aspect, the fourth determination value is corrected to decrease according to the decrease change amount of the atmospheric pressure during the measurement of the first return pressure amount. According to this preferred aspect, since the decrease correction amount of the fourth determination value when the atmospheric pressure changes decreases corresponds to the decrease change amount of the atmospheric pressure, the fourth determination compared with the second return pressure amount. The value becomes more appropriate, and it is possible to more accurately determine the presence or absence of a minute leak abnormality. Note that it is possible to accurately determine the presence or absence of an extremely small amount of leak abnormality by correcting the third determination value to be decreased similarly to the fourth determination value.
[0021]
As described above, in the present invention, the fourth determination value is used to determine whether the increase factor of the first return pressure amount is a minute leak or the fuel transpiration, while the fuel is used to determine whether the cause is an extremely small amount of leak. When discriminating whether it is transpiration, a third determination value smaller than the fourth determination value is used.
In the invention of claim 3, the fourth determination value is replaced with the third determination value when the atmospheric pressure decreases and changes by a predetermined pressure or more during the measurement of the first return pressure amount. According to this preferred embodiment, when the atmospheric pressure decreases and changes with a simple configuration in which the third determination value or the fourth determination value itself is selectively used as the fourth determination value depending on whether or not there is a decrease in atmospheric pressure. In addition, the fourth determination value can be decreased and corrected to prevent erroneous determination.
[0022]
In addition to the third determination value and the fourth determination value, a fifth determination value smaller than the third determination value is set in advance as a determination value used for comparison with the second return pressure amount, and the first recovery value is set. The third determination value may be replaced with the fifth determination value when the atmospheric pressure during the pressure measurement is decreased or changed by a predetermined pressure or more, so that even when the atmospheric pressure is decreased and changed, a very small amount of leak abnormality is detected. Presence / absence can be accurately determined with a simple configuration.
[0023]
In the failure diagnosis apparatus according to claim 4, the first return pressure measured after reducing the failure diagnosis target region is sequentially compared with the first determination value and the second determination value larger than the first determination pressure, If the amount is larger than the first determination value or the second determination value, the atmospheric pressure is introduced into the failure diagnosis target region, then the region is sealed, the second return pressure amount is measured, and then the first return pressure amount is measured. Is larger than the first determination value and smaller than the second determination value, the second return pressure amount is compared with a third determination value set according to the first return pressure amount, while the first return pressure amount is If the second determination value is greater than or equal to the second determination value, the second return pressure amount is compared with a fourth determination value set in accordance with the first return pressure amount, and the first return pressure amount is greater than the first determination value and When the return pressure amount is smaller than the third determination value, or when the first return pressure amount is larger than the second determination value and the second return pressure amount is smaller than the fourth determination value. Determining fuel evaporative emission system to be abnormal.
[0024]
According to the failure diagnosis apparatus of the fourth aspect, when the first return pressure amount exceeds the first determination value or the second determination value, which is a determination criterion for a very small amount of leak or a very small amount of leak, a leakage abnormality is temporarily determined. Next, the second return pressure amount is measured in order to determine the increase factor of the first return pressure amount. If the first return pressure amount is between the first determination value and the second determination value, the second return pressure amount is compared with the third determination value. The third determination value is set in accordance with the first return pressure amount and is adapted to the extremely small amount of leak, and if the second return pressure amount exceeds the third determination value, the first return pressure amount increases. While it is determined that the transpiration is due to fuel evaporation, the provisional determination of the leakage abnormality is withdrawn. On the other hand, if the second return pressure is less than the third determination value, it is determined that the increase in the first recovery pressure is due to the leakage abnormality. Anomalies due to trace leaks are finally determined. On the other hand, if the first return pressure amount is equal to or greater than the second determination value, the second return pressure amount is compared with a fourth determination value set so as to be adapted to a slight leak according to the first return pressure amount. If the value exceeds the fourth determination value, the provisional determination of the leakage abnormality is withdrawn, whereas if the value is below the fourth determination value, the abnormality due to the small amount of leak is finally determined. In this way, by using the third determination value and the fourth determination value adapted to the first return pressure amount, it is possible to accurately determine the presence or absence of an extremely small amount of leak or a small amount of leak while preventing erroneous determination due to fuel evaporation.
[0025]
Furthermore, in the invention described in claim 4, when the atmospheric pressure decreases and changes during the measurement of the first return pressure amount, the third determination value or the fourth determination value is corrected to decrease.
In the present invention, when the atmospheric pressure decreases and changes during the measurement of the first return pressure, the third determination is compared with the second return pressure for the determination of the increase factor of the first return pressure (high transpiration determination). The value or the fourth determination value is corrected to decrease, so even when measuring the internal pressure of the fuel tank (first return pressure) using a relative pressure sensor, It is possible to accurately determine whether there is an abnormality due to a very small amount of leak.
[0026]
According to the fifth aspect of the present invention, the third determination value or the fourth determination value is corrected to decrease in accordance with the decrease change amount of the atmospheric pressure during the measurement of the first return pressure amount. According to this preferred aspect, the amount of decrease correction of the third determination value or the fourth determination value becomes more appropriate, and the presence or absence of an abnormality due to a trace leak or a trace trace leak is more accurately determined.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
The failure diagnosis apparatus of the present invention will be described below with reference to the accompanying drawings.
As shown in FIG. 1, the fuel evaporation prevention system for a vehicle equipped with the failure diagnosis device is configured such that the evaporation fuel in the fuel tank 1 is adsorbed to the canister 3 through the vapor passage 2 and a predetermined purge condition is established. Sometimes, under the control of the ECU 11, the purge valve 7 provided in the purge passage 4 is opened, and the vaporized fuel adsorbed in the canister 3 is discharged to the intake passage 6 of the internal combustion engine 5 through the purge passage 4. The release of fuel into the atmosphere is prevented.
[0028]
A failure diagnosis apparatus according to an embodiment of the present invention diagnoses the presence or absence of a leak abnormality in a fuel transpiration prevention system, and includes a vent valve 8 attached to a canister 3 and a tank internal pressure attached to a fuel tank 1. The pressure sensor 10 to detect, ECU11 which controls opening and closing of the purge valve 7 and the vent valve 8, and the atmospheric pressure sensor 12 connected to the input side of ECU11 are provided. The pressure sensor 10 is composed of a relative pressure sensor that detects a relative pressure inside and outside the fuel tank 1 as a fuel tank internal pressure, and the fuel tank internal pressure detected by the pressure sensor 10 is used to drive a vehicle equipped with this apparatus uphill. If the atmospheric pressure decreases with the increase, the amount of decrease in the atmospheric pressure increases.
[0029]
In the fuel evaporation prevention system with a failure diagnosis device, when the purge valve 7 is opened and the vent valve 8 is closed, the fuel tank 1 communicates with the intake passage 6 via the vapor passage 2 and the purge passage 4. The pressure in the fuel tank 1 is reduced by the negative pressure. On the other hand, when the purge valve 7 is closed and the vent valve 8 is opened, the pressure in the fuel tank 1 is increased to about atmospheric pressure. Thereafter, when both the purge valve 7 and the vent valve 8 are closed, the pressure in the fuel tank 1 is increased to an atmospheric pressure or higher due to the evaporation of fuel in the fuel tank 1.
[0030]
The ECU 11 of the failure diagnosis apparatus executes a failure diagnosis routine shown in FIGS. 2 and 3 at a cold start when the ignition key of the vehicle is turned on, for example.
In step S1 of the failure diagnosis routine, the ECU 11 establishes a failure diagnosis condition such that the start-up coolant temperature and the intake air temperature are equal to or lower than predetermined temperatures, the fuel temperature is equal to or lower than a predetermined temperature, and the remaining amount of fuel is within a predetermined value. It is determined whether or not.
[0031]
If it is determined in step S1 that the failure diagnosis condition is not satisfied, the failure diagnosis in the current cycle is terminated. On the other hand, when it is determined in step S1 that the failure diagnosis condition has been established, the tank internal pressure increase amount indicated by symbol ΔP1 in FIG. 4 is measured (step S2). In the measurement of ΔP1, the purge valve 7 is closed and the vent valve 8 is opened to open the failure diagnosis target area of the fuel transpiration prevention system to the atmosphere. At this time, the purge valve 7 may be gradually closed. Then, the output of the pressure sensor 10 representing the tank internal pressure P1 in the atmosphere open state is read. When the vent valve 8 is closed after the measurement of the tank internal pressure P1, the tank internal pressure increases with time as shown in FIG.
[0032]
The output of the pressure sensor 10 is read when a predetermined time T1 has elapsed from the time when the tank internal pressure P1 is measured, and the tank internal pressure P2 at that time is measured. Next, the tank internal pressure increase amount ΔP1 is calculated from the tank internal pressures P1 and P2, and the measurement of ΔP1 in step S2 is thereby completed.
In the next step S3, it is determined whether or not the tank internal pressure increase ΔP1 obtained in step S2 is smaller than the high transpiration determination value L1, and if this determination result is negative, it is determined that accurate failure diagnosis is impossible due to excessive fuel transpiration. Judgment is made (step S3a), and the failure diagnosis is terminated.
[0033]
On the other hand, if the tank internal pressure increase amount ΔP1 is equal to or less than the leak determination value L1, further failure determination is performed. For this reason, first, in step S4 of FIG. 2, when the purge valve 7 is opened and the failure diagnosis target area is depressurized, the pressure detected by the pressure sensor 10 reaches a predetermined negative pressure value indicated by symbol P3 in FIG. Then, the purge valve 7 is closed to close the failure diagnosis target region. In the failure diagnosis target region in the closed state, the tank internal pressure increases with time as shown in FIG. 4 due to the evaporation or leakage of fuel in the fuel tank 1. When a predetermined time T2 elapses from the time when the purge valve 7 is closed, the output of the pressure sensor 10 indicating the tank internal pressure P4 at that time is read, and the tank as the first return pressure amount is read from the tank internal pressures P3 and P4. An internal pressure increase amount ΔP is calculated.
[0034]
In the next step S5, it is determined whether or not the first return pressure ΔP calculated in step S4 is larger than a first determination value L11 suitable for determination of a very small amount of leak that mainly occurs due to a minimum leak hole. If the determination result is negative, it is determined that there is no leak abnormality (step S5a), and the failure diagnosis is terminated.
On the other hand, if the first return pressure amount ΔP is larger than the first determination value L11, the first return pressure amount ΔP is suitable for the determination of the minute leak that occurs mainly due to the small leak hole. It is determined whether it is larger than (step S6). If the determination result in step S6 is affirmative, the value of the flag F indicating the number of times that the first return pressure ΔP exceeds the second determination value L12 is incremented by “1” (step S7), and then The control flow moves to step S8. On the other hand, if the determination result in step S6 is negative, that is, if the first return pressure ΔP is less than the second determination value L12, the process proceeds from step 6 to step S8.
[0035]
In step S8, it is determined whether or not the flag Fbp is a value “1” indicating that the decrease amount ΔBP of the atmospheric pressure BP during the measurement of the first return pressure ΔP is equal to or greater than a predetermined amount BPa. If the determination result in step S8 is affirmative (flag Fbp = 1), the control flow proceeds to step S12 in FIG.
On the other hand, if the determination result in step S8 is negative (Fbp ≠ 1), that is, if it is determined that the atmospheric pressure has not decreased during the previous ΔP measurement, the atmospheric pressure decreases during the current ΔP measurement. It is determined whether or not there has been a change. For this reason, when the predetermined time T2 has elapsed from the time when the tank internal pressure reaches the predetermined negative pressure P3 and the atmospheric pressure BP1 detected by the atmospheric pressure sensor 12 and temporarily stored in the memory and the predetermined negative pressure P3 is reached. The detected and temporarily stored atmospheric pressure BP2 is read from the memory, and BP2 is subtracted from BP1 to obtain an atmospheric pressure decrease change amount ΔBP. Further, it is determined whether or not the change amount ΔBP is equal to or greater than a predetermined amount BPa ( Step S9). When it is determined that there is a change in the atmospheric pressure that is greater than or equal to the predetermined amount BPa during the measurement of the first return pressure ΔP, the flag Fbp is set to a value 1 (step S10). If there is no change, the flag Fbp is reset to 0 (step S11).
[0036]
In step S12 following step S8, S10 or S11, the number N of times of measurement of the first return pressure ΔP is incremented by “1”, and then it is determined whether or not the number of times of measurement N is equal to “3” (step S12). S13). If the number of measurements of the first return pressure ΔP is less than 3, the process proceeds to step S4 in FIG. 2 and the first return pressure ΔP is measured again. When the first return pressure ΔP is measured three times, the determination result in step S13 is affirmative, and in the next step S14, it is determined whether or not the value of the flag F is “3”.
[0037]
If the determination result of step S14 is negative, that is, if it is determined that any of the first return pressure ΔP measured three times is lower than the second determination value L12, it is confirmed that there is a trace amount leak mainly due to the minimum leak hole. Temporarily determining and determining value L used in high transpiration determination, which will be described later, is set to a third determination value L21 suitable for distinguishing between a very small leak and high transpiration (step S16).
[0038]
On the other hand, if it is determined in step S14 that all of the first return pressures ΔP measured three times have exceeded the second determination value L12, the flag Fbp is set to 1 in the next step S15. It is determined whether or not there is.
If the determination result in step S15 is negative, that is, if the atmospheric pressure does not change more than the predetermined amount BPa while measuring the first return pressure ΔP three times, it is mainly due to the small leak hole. It is temporarily determined that there is a trace leak, and the high transpiration judgment value L is set to a fourth judgment value L22 suitable for distinguishing between the trace leak and the high transpiration (step S17). On the other hand, if the determination result in step S15 is affirmative, that is, if it is determined that an atmospheric pressure decrease change of a predetermined amount BPa or more is detected even once during the measurement of the first return pressure ΔP over 3 degrees, the determination is made in step S14. The third determination value is smaller than the fourth determination value L22 suitable for the minute leak determination although the high recuperation amount ΔP is large and it is determined that there is a possibility of the minute leak. L21 is set (step S15).
[0039]
That is, when the atmospheric pressure BP is decreased and changed by a predetermined pressure or more due to steep climbing during the ΔP measurement, the measured value of the fuel tank internal pressure by the pressure sensor 10 composed of a relative pressure sensor is shown in FIG. Since the tank internal pressure change curve indicated by the chain line increases relatively as shown by the white arrow from the curve indicated by the solid line, the determination value L is the same as the high transpiration determination value at the time of traveling on the flat ground without the atmospheric pressure decrease change. When the high transpiration determination is performed using the, the determination value L becomes excessive by the amount corresponding to the atmospheric pressure decrease, and there is a possibility that the leakage abnormality is erroneously determined even though there is no actual leakage abnormality.
[0040]
In this regard, even if the first return pressure amount is large, when the atmospheric pressure decreases, the fourth determination value L22 is determined as the third determination in step S15 as indicated by the thick downward arrow in FIG. 4 and as shown in FIG. When the value is replaced with the value L21, the fourth determination value L22 is corrected to decrease, and an erroneous determination can be avoided.
In step S18 of the failure diagnosis routine, the purge valve 7 is closed and the vent valve 8 is opened to open the failure diagnosis target region to the atmosphere. After the tank internal pressure P5 in the open state is measured by the pressure sensor 10, the vent valve 8 To close the failure diagnosis target area. In this closed state, the tank internal pressure increases with time as shown in FIG. Then, the output of the pressure sensor 10 is read when a predetermined time T3 has elapsed from the time when the measurement of the tank internal pressure P5 is completed, the tank internal pressure P6 at that time is measured, and the tank internal pressure P5, P6 is used as a second return pressure amount. The re-ΔP1 is calculated.
[0041]
In the next step S19, it is determined whether or not the re-ΔP1 is larger than the determination value L set in step S16 or S17. If the determination result is negative, a final determination is made in step S20 that there is a leak. On the other hand, if the determination result in step S19 is affirmative, it is determined that the provisional determination that there is a leak should be withdrawn because the increase in the first restoration amount ΔP is due to high transpiration (step S21). The fault diagnosis is terminated without performing it. Here, when the atmospheric pressure decrease changes, the fourth determination value L22 used for the final determination is corrected for decrease as described above. Therefore, the leak abnormality is caused because the determination value is excessive by the amount corresponding to the atmospheric pressure decrease change. The risk of misjudging is reduced. When it is determined in step S20 that there is a leak, a leak determination result is notified using an alarm lamp, an alarm buzzer, or the like.
[0042]
Summarizing the above, in the present embodiment, the first and second determination values L11 and L12 are set in correspondence with the extremely small amount of leak and the very small amount of leak, respectively, and the third and fourth determination values L21 and L22 are extremely small. The minute leak and the abnormality due to the minute leak are set to be distinguishable from the abnormality due to fuel evaporation. If the first return pressure ΔP exceeds the first determination value L11 that is the determination criterion of the very small amount of leak and is lower than the second determination value L12 that is the determination criterion of the very small amount of leak, an abnormality due to the very small amount of leakage is present. Next, a temporary determination is made, and then the second return pressure (re-ΔP1) is measured to determine whether the increase in the first return pressure is due to a very small amount of leak or excessive fuel evaporation. Is done. When the second return pressure exceeds the third determination value L21, it is determined that the fuel transpiration is an increase factor of the first return pressure ΔP, and the provisional determination of the trace amount leak abnormality is withdrawn and the trace amount is reduced. It is finally determined that the presence or absence of leak is unknown (diagnosis is invalid due to high transpiration determination). On the other hand, if the second return pressure amount does not exceed the third determination value, it is determined that a very small amount of leak is an increase factor of the first return pressure amount, and a very small amount of leak abnormality is finally determined. Further, when the first return pressure amount ΔP exceeds the second determination value L12, an abnormality due to a slight leak is tentatively determined, and then the second return pressure amount (re-establishment is performed to determine the increase factor of the first return pressure amount. When ΔP1) is measured and the second return pressure exceeds the fourth determination value L22, it is determined that fuel evaporation is an increase factor of the first return pressure ΔP, and the presence or absence of a slight leak is unknown (diagnosis by high evaporation determination). When the second return pressure amount does not exceed the fourth determination value L22, it is determined that the slight leak is an increase factor of the first return pressure amount, and the final determination is made that there is a minute leak abnormality. Is done. In this way, it is possible to accurately determine a very small amount of leak or a very small amount of leak.
[0043]
Further, in this embodiment, the pressure sensor 10 that detects the relative pressure inside and outside the fuel tank is used to measure the fuel tank internal pressures P1 to P6. Therefore, if the atmospheric pressure decreases during the tank internal pressure measurement, only the decrease in the atmospheric pressure is changed. There is a possibility that an error may occur in the leak determination due to a relative increase in the measured value. However, when the atmospheric pressure decreases and changes by a predetermined amount BPa or more during the ΔP measurement, the second reversion amount ( Since the fourth determination value L22 compared with ΔP1) is corrected to decrease, it is possible to accurately determine the presence or absence of a minute leak abnormality, and to determine a minute leak abnormality without being affected by atmospheric pressure changes during the ΔP measurement. can do. Further, since the decrease correction of the fourth determination value L22 is performed by replacing the fourth determination value L22 with the third determination value L21, the configuration and determination procedure relating to the leak determination are simplified.
[0044]
In other words, the ECU 11 of the failure diagnosis device functions as a first diagnosis unit that compares the first return pressure ΔP measured after the pressure reduction of the failure diagnosis target region with the first determination value L11 or the second determination value L12, and , Functioning as a second diagnosis means for comparing the second return pressure amount (re-ΔP1) measured in a state where the failure diagnosis target area is closed after being released to the atmosphere with the third determination value L21 or the fourth determination value L22, And function as an abnormality determining means for determining an abnormality of the fuel transpiration prevention system based on the second return pressure amount, and further functioning as a correcting means for reducing and correcting the fourth determination value L22 when the atmospheric pressure BP decreases and changes. To do.
[0045]
Now, the present inventors manufactured a fuel transpiration prevention system equipped with the failure diagnosis device according to the above embodiment, set the first to fourth determination values L11, L12, L21 and L22, and evaluated the failure diagnosis accuracy. . FIG. 6 shows a failure diagnosis result when the remaining amount of fuel in the fuel tank 1 is 40 to 85%, and FIG. 7 shows a failure diagnosis result when the remaining amount of fuel is 15 to 40%. 6 and 7, the ○ mark indicates the diagnosis result of the fuel transpiration prevention system without leak, and the ● mark indicates the fuel transpiration prevention system provided with a 0.5 mm diameter minimum leak hole that causes a very small amount of leak. The △ mark indicates the diagnosis result related to the fuel transpiration prevention system provided with a small leak hole having a diameter of 1.0 mm that causes a slight leak.
[0046]
As can be seen from FIG. 6, in the fuel transpiration prevention system without leakage, as indicated by a circle, the first return pressure ΔP is often less than the first determination value L11, so that most of them are correctly determined correctly, When the first return pressure ΔP exceeds the first determination value L11, the re-ΔP1 exceeds the third determination value L21 or the fourth determination value L22, and the high transpiration determination is made. That is, there is a correlation between the first return pressure amount ΔP and the re-ΔP1, and the re-ΔP1 increases as the first return pressure amount ΔP increases. In the case indicated by an elliptical area in FIG. 6, normality can be determined by variably setting the first determination value L11 according to the fuel temperature and the remaining amount of fuel. In a system with a very small leak hole, as shown by the mark ●, in most cases, the leak judgment is correct, but when the fuel transpiration is large, a high transpiration judgment is sometimes made. In a system having a small leak hole, in most cases, the leak is correctly determined as indicated by the Δ mark, and particularly when the first return pressure ΔP exceeds the second determination value L12 as indicated by the circular area in FIG. It has been clarified that the leak determination is correctly performed by using the fourth determination value L22 larger than the third determination value L21 as the determination reference value related to the second return pressure value (re-ΔP1).
[0047]
As can be seen from FIG. 7, even when the remaining amount of fuel is small, the same failure diagnosis accuracy as in FIG. 6 can be obtained, and in particular, the effect of using the fourth determination value L22 as shown by the circular area in FIG. It is appearing in. Thus, it has been found that the failure diagnosis apparatus is suitable for failure diagnosis in a low fuel amount region. However, as shown by the elliptical area in FIG.
[0048]
Although the description of one embodiment of the present invention has been completed above, the present invention is not limited to the above embodiment and can be variously modified.
For example, in the above-described embodiment, the fourth determination value L22 is corrected to decrease when an atmospheric pressure decrease change of a predetermined amount BPa or more is detected even once during ΔP measurement over 3 degrees. When the change is detected a plurality of times, or when the maximum value, the minimum value, or the average value of the atmospheric pressure decrease change amount during the third ΔP measurement exceeds the predetermined amount BPa, the decrease correction may be performed. Good. Note that ΔP measurement is not limited to three times.
[0049]
Further, when the atmospheric pressure decrease change amount ΔBP is equal to or greater than the predetermined amount BPa, it is not essential to correct the high transpiration determination value L in a stepped manner from L22 to L21 as shown in FIG. As shown, the determination value L may be corrected to decrease by multiplying the determination value L by a correction coefficient KL that decreases from the value 1 as the atmospheric pressure decrease change amount ΔBP increases.
[0050]
In the above embodiment, only the fourth determination value L22 is corrected to decrease when the atmospheric pressure decreases, but both the third determination value L21 and the fourth determination value L22 may be corrected. At this time, each determination value may be corrected stepwise at a predetermined amount BPa as shown in FIG. 5, or may be corrected stepwise at each of a plurality of predetermined amounts, or may be gradually reduced as shown in FIG. it can.
[0051]
Furthermore, in the above embodiment, the third determination value L21 and the fourth determination value L22 are constant regardless of the value of the first return pressure ΔP, but both the determination values L21, L22 are set according to the first return pressure ΔP. It is also possible to variably set, or to variably set one of the determination values to be compared with the second return pressure amount (re-ΔP1) according to ΔP. Also in this modified example, if there is a change in atmospheric pressure that is greater than or equal to a predetermined pressure during the ΔP measurement, the third determination value L21 or the fourth determination value L22 or both determination values are corrected to decrease, preferably, the atmospheric pressure Decrease correction according to the decrease change amount.
[0052]
In addition, the present invention can be variously modified within the scope of the inventive concept.
[0053]
【The invention's effect】
5. The failure diagnosis apparatus according to claim 1, wherein the first return pressure measured after depressurizing the failure diagnosis target area of the fuel transpiration prevention system exceeds a first determination value or a second determination value larger than the first determination value. After the atmospheric pressure is introduced into the failure diagnosis target region, the failure diagnosis target region is sealed and the second return pressure is measured. If the first return pressure is between the first determination value and the second determination value, While comparing the second return pressure amount with the third determination value, if the first return pressure amount exceeds the second determination value, the second return pressure amount is compared with a fourth determination value that is greater than the third determination value. When the first return pressure exceeds the first determination value and the second return pressure does not exceed the third determination value, or the first return pressure exceeds the second determination value and the second return pressure is When the fourth judgment value is not exceeded, the evaporative fuel transpiration prevention system is judged to be abnormal. While the existence of and trace leakage preventing erroneous determination due to excessive fuel transpiration can be determined accurately. In the invention according to claim 4, since the third determination value and the fourth determination value are adapted to the extremely small amount of leak and the very small amount of leak according to the first return pressure amount, the leak determination can be performed more accurately. .
[0054]
In the first aspect of the present invention, when the atmospheric pressure decreases and changes during the measurement of the first return pressure amount, the fourth return pressure is compared with the second return pressure amount in order to determine an increase factor of the first return pressure amount. Since the determination value is corrected to decrease, even in the failure diagnosis device that measures the first and second return pressure amounts based on the fuel tank internal pressure detected using the relative pressure sensor that detects the relative pressure inside and outside the fuel tank. In addition, it is possible to accurately determine whether there is an abnormality due to a slight leak in the evaporated fuel transpiration prevention system without being affected by changes in atmospheric pressure during measurement of the fuel tank internal pressure. In the invention of claim 4, since the third judgment value or the fourth judgment value is decreased and corrected when the atmospheric pressure decreases, the presence or absence of an abnormality due to a very small amount of leak or a minute amount of leak is accurately determined without being affected by the change in atmospheric pressure. Is possible.
[0055]
In the failure diagnosis apparatus according to claim 2, the fourth determination value is corrected to decrease or the third determination value or the fourth determination value is set in accordance with a decrease change amount of the atmospheric pressure during measurement of the first return pressure amount. Since the decrease correction is performed, the decrease correction amount of the fourth determination value, or the decrease correction amount of the third determination value or the fourth determination value corresponds to the decrease change amount of the atmospheric pressure, and is compared with the second return pressure amount. The fourth determination value, or the third determination value or the fourth determination value can be made more appropriate, and the presence or absence of a slight leak abnormality can be determined more accurately.
[0056]
According to the third aspect of the present invention, the fourth determination value is replaced with the third determination value when the atmospheric pressure decreases and changes by a predetermined pressure or more during the measurement of the first return pressure amount. Can be corrected with a simple configuration of replacement of the determination value.
[Brief description of the drawings]
FIG. 1 is a schematic view of a fuel transpiration prevention system equipped with a failure diagnosis apparatus according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing a part of a failure diagnosis routine executed by an ECU shown in FIG. 1;
FIG. 3 is a flowchart showing the remaining part of the failure diagnosis routine following FIG. 2;
FIG. 4 is a diagram showing a change with time in fuel tank internal pressure during failure diagnosis.
FIG. 5 is a diagram showing a relationship between a high transpiration determination value L used in the failure diagnosis routine shown in FIGS. 2 and 3 and an atmospheric pressure decrease change amount ΔBP during measurement of the first return pressure amount ΔP.
FIG. 6 is a diagram showing failure diagnosis accuracy by the failure diagnosis apparatus of the present invention when the remaining amount of fuel is large.
FIG. 7 is a diagram showing failure diagnosis accuracy when the remaining amount of fuel is low.
FIG. 8 is a diagram showing a relationship between a correction coefficient KL and an atmospheric pressure decrease change amount ΔBP used for setting a high transpiration determination value L in a failure diagnosis routine according to a modification of the present invention.
[Explanation of symbols]
1 Fuel tank
2 Vapor passage
3 Canister
4 Purge passage
5 Internal combustion engine
6 Air intake passage
7 Purge valve
8 Vent valve
10 Pressure sensor
11 ECU (first and second diagnosis means, abnormality determination means, correction means)
12 Atmospheric pressure sensor

Claims

燃料タンク内で発生する蒸発燃料をキャニスタに捕集して内燃機関の吸気通路へ導入する燃料蒸散防止システムの故障診断装置において、
前記燃料蒸散防止システムの故障診断対象領域を減圧した後に測定した第１復圧量を第１判定値および前記第１判定値よりも大きな第２判定値と順次比較する第１診断手段と、
前記第１診断手段により測定された前記第１復圧量が前記第１判定値又は第２判定値よりも大きければ、前記故障診断対象領域に大気圧を導入した後に前記故障診断対象領域を密閉して第２復圧量を測定し、次に、前記第１復圧量が前記第１判定値よりも大きく且つ前記第２判定値よりも小さい場合は前記第２復圧量を第３判定値と比較する一方、前記第１復圧量が前記第２判定値よりも大きい場合には前記第２復圧量を前記第３判定値よりも大きな第４判定値と比較する第２診断手段と、
前記第１診断手段により測定された第１復圧量が前記第１判定値よりも大きく且つ前記第２診断手段により測定された第２復圧量が前記第３判定値よりも小さいとき、或いは、前記第１復圧量が前記第２判定値よりも大きく且つ前記第２復圧量が前記第４判定値よりも小さいときに、前記燃料蒸散防止システムを異常と判定する異常判定手段と、
前記第１診断手段による前記第１復圧量の測定中に大気圧が減少変化した場合に、前記第２診断手段により前記第２復圧量と比較される前記第４判定値を減少補正する補正手段と
を備えたことを特徴とする燃料蒸散防止システムの故障診断装置。In a failure diagnosis device for a fuel transpiration prevention system that collects evaporated fuel generated in a fuel tank in a canister and introduces it into an intake passage of an internal combustion engine,
First diagnostic means for sequentially comparing a first return pressure measured after depressurizing a failure diagnosis target area of the fuel transpiration prevention system with a first determination value and a second determination value larger than the first determination value;
If the first return pressure measured by the first diagnosis means is larger than the first determination value or the second determination value, the failure diagnosis target region is sealed after introducing atmospheric pressure into the failure diagnosis target region. The second return pressure amount is measured, and then, when the first return pressure amount is larger than the first determination value and smaller than the second determination value, the second return pressure amount is determined as a third determination. A second diagnosis means for comparing the second return pressure amount with a fourth determination value greater than the third determination value when the first return pressure amount is greater than the second determination value. When,
When the first return pressure measured by the first diagnosis means is larger than the first determination value and the second return pressure measured by the second diagnosis means is smaller than the third determination value; or An abnormality determination means for determining that the fuel transpiration prevention system is abnormal when the first return pressure amount is larger than the second determination value and the second return pressure amount is smaller than the fourth determination value;
When atmospheric pressure decreases and changes during measurement of the first return pressure amount by the first diagnosis means, the fourth determination value to be compared with the second return pressure amount is reduced and corrected by the second diagnosis means. A failure diagnosis apparatus for a fuel transpiration prevention system, comprising: a correction unit.

前記補正手段は、前記第１診断手段による前記第１復圧量の測定中の大気圧の減少変化量に応じて前記第４判定値を減少補正することを特徴とする請求項１に記載の燃料蒸散防止システムの故障診断装置。2. The correction unit according to claim 1, wherein the correction unit corrects the fourth determination value in a reduced manner according to a decrease change amount of atmospheric pressure during the measurement of the first return pressure amount by the first diagnosis unit. Failure diagnosis device for fuel transpiration prevention system.

前記補正手段は、前記第１診断手段による前記第１復圧量の測定中に、大気圧が所定圧以上減少変化した場合に、前記第４判定値を前記第３判定値に置き換えることを特徴とする請求項１に記載の燃料蒸散防止システムの故障診断装置。The correction means replaces the fourth determination value with the third determination value when the atmospheric pressure decreases and changes by a predetermined pressure or more during measurement of the first return pressure amount by the first diagnosis means. The failure diagnosis apparatus for a fuel transpiration prevention system according to claim 1.

燃料タンク内で発生する蒸発燃料をキャニスタに捕集して内燃機関の吸気通路へ導入する燃料蒸散防止システムの故障診断装置において、
前記燃料蒸散防止システムの故障診断対象領域を減圧した後に測定した第１復圧量を第１判定値および前記第１判定値よりも大きな第２判定値と順次比較する第１診断手段と、
前記第１診断手段により測定された前記第１復圧量が前記第１判定値又は第２判定値よりも大きければ、前記故障診断対象領域に大気圧を導入した後に前記故障診断対象領域を密閉して第２復圧量を測定し、次に、前記第１復圧量が前記第１判定値よりも大きく且つ前記第２判定値よりも小さい場合は前記第２復圧量を前記第１復圧量に応じて設定された第３判定値と比較する一方、前記第１復圧量が前記第２判定値以上の場合には前記第２復圧量を前記第１復圧量に応じて設定された第４判定値と比較する第２診断手段と、
前記第１診断手段により測定された第１復圧量が前記第１判定値よりも大きく且つ前記第２診断手段により測定された第２復圧量が前記第３判定値よりも小さいとき、或いは、前記第１復圧量が前記第２判定値よりも大きく且つ前記第２復圧量が前記第４判定値よりも小さいときに、前記燃料蒸散防止システムを異常と判定する異常判定手段と、
前記第１診断手段による前記第１復圧量の測定中に大気圧が減少変化した場合に、前記第２診断手段により前記第２復圧量と比較される前記第３判定値又は前記第４判定値を減少補正する補正手段と
を備えたことを特徴とする燃料蒸散防止システムの故障診断装置。In a failure diagnosis device for a fuel transpiration prevention system that collects evaporated fuel generated in a fuel tank in a canister and introduces it into an intake passage of an internal combustion engine,
First diagnostic means for sequentially comparing a first return pressure measured after depressurizing a failure diagnosis target area of the fuel transpiration prevention system with a first determination value and a second determination value larger than the first determination value;
If the first return pressure measured by the first diagnosis means is larger than the first determination value or the second determination value, the failure diagnosis target region is sealed after introducing atmospheric pressure into the failure diagnosis target region. Then, the second return pressure amount is measured, and then, when the first return pressure amount is larger than the first determination value and smaller than the second determination value, the second return pressure amount is determined as the first return pressure amount. While comparing with the third determination value set according to the return pressure amount, when the first return pressure amount is greater than or equal to the second determination value, the second return pressure amount is set according to the first return pressure amount. Second diagnostic means for comparing with the fourth determination value set in
When the first return pressure measured by the first diagnosis means is larger than the first determination value and the second return pressure measured by the second diagnosis means is smaller than the third determination value; or An abnormality determination means for determining that the fuel transpiration prevention system is abnormal when the first return pressure amount is larger than the second determination value and the second return pressure amount is smaller than the fourth determination value;
The third determination value or the fourth determination value compared with the second return pressure amount by the second diagnosis means when the atmospheric pressure decreases and changes during the measurement of the first return pressure amount by the first diagnosis means. A failure diagnosing device for a fuel transpiration prevention system, comprising: a correction means for reducing and correcting a determination value.

前記補正手段は、前記第１診断手段による前記第１復圧量の測定中の大気圧の減少変化量に応じて前記第３判定値又は前記第４判定値を減少補正することを特徴とする請求項４に記載の燃料蒸散防止システムの故障診断装置。The correction means corrects the third determination value or the fourth determination value in accordance with a decrease change amount of atmospheric pressure during measurement of the first return pressure amount by the first diagnosis means. The failure diagnosis apparatus for a fuel transpiration prevention system according to claim 4.