초록 ▼

An ECU computes a transit time from a time when the fuel vapor passes the purge valve right after the purge valve is opened until a time when the fuel vapor reaches a vicinity of the fuel injector. Further more, the ECU computes a fuel vapor concentration at the vicinity of the fuel injector after t

An ECU computes a transit time from a time when the fuel vapor passes the purge valve right after the purge valve is opened until a time when the fuel vapor reaches a vicinity of the fuel injector. Further more, the ECU computes a fuel vapor concentration at the vicinity of the fuel injector after the transit time has elapsed based on a first-order lag curve which is defined by a maximum variation of the fuel vapor concentration and a time constant. Correcting the fuel injection quantity according to the fuel vapor concentration at the vicinity of the injector restricts a disturbance of air-fuel ratio at a time of starting purge process.

대표청구항 ▼

What is claimed is: 1. A fuel vapor treatment system mounted on an internal combustion engine which has a fuel injector for injecting fuel into an intake pipe, comprising: a canister containing an adsorbent which temporarily adsorbs fuel vapor generated in a fuel tank; a purge passage which introdu

What is claimed is: 1. A fuel vapor treatment system mounted on an internal combustion engine which has a fuel injector for injecting fuel into an intake pipe, comprising: a canister containing an adsorbent which temporarily adsorbs fuel vapor generated in a fuel tank; a purge passage which introduces fuel vapor desorbed from the canister into the intake pipe; a purge valve which opens/closes the purge passage; a transit time computing means for computing a first transit time from a time when the fuel vapor passes the purge valve right after the purge valve is opened until a time when the fuel vapor reaches a vicinity of the fuel injector; and a concentration computing means for computing a fuel vapor concentration at the vicinity of the fuel injector after the first transit time has elapsed based on a first-order lag curve which is defined by a maximum variation of the fuel vapor concentration and a time constant. 2. A fuel vapor treatment system mounted on an internal combustion engine which has a fuel injector for injecting fuel into an intake pipe, comprising: a canister containing an adsorbent which temporarily adsorbs fuel vapor generated in a fuel tank; a purge passage which introduces fuel vapor desorbed from the canister into the intake pipe; a purge valve which opens/closes the purge passage; a transit time computing means for computing a second transit time from a time when the fuel vapor passes the purge valve right before the purge valve is closed until a time when the fuel vapor reaches a vicinity of the fuel injector; and a concentration computing means for computing a fuel vapor concentration at the vicinity of the fuel injector after the second transit time has elapsed based on a first-order lag curve which is defined by a maximum variation of the fuel vapor concentration and a time constant. 3. A fuel vapor treatment system according to claim 1, wherein the concentration computing means increases the time constant as an intake air pressure of the internal combustion engine increases. 4. A fuel vapor treatment system according to claim 2, wherein the concentration computing means increases the time constant as an intake air pressure of the internal combustion engine increases. 5. A fuel vapor treatment system according to claim 3, wherein the concentration computing means decreases the time constant as an intake air flow rate increases. 6. A fuel vapor treatment system according to claim 4, wherein the concentration computing means decreases the time constant as an intake air flow rate increases. 7. A fuel vapor treatment system according to claim 1 wherein the first transit time increases as an intake air pressure increases. 8. A fuel vapor treatment system according to claim 2, wherein the second transit time increases as an intake air pressure increases. 9. A fuel vapor treatment system according to claim 7, wherein the first transit time decreases as the intake air flow rate increases. 10. A fuel vapor treatment system according to claim 8, wherein the second transit time decreases as the intake air flow rate increases.