| 摘要 |
PROBLEM TO BE SOLVED: To improve accuracy of an air-fuel ratio control by correcting purge concentration by taking into consideration detachment delay of fuel vapor according to a change of purge flow rate when suddenly changing the purge flow rate. SOLUTION: Fuel vapor generated within a fuel tank 1 is scavenged in a canister 14, and the scavenged fuel vapor is purged in an intake passage 10 of an engine 8 via a purge control valve 22. An ECU 31 detects the purge flow rate of purge gas and detects concentration of fuel vapor in purge gas. The ECU 31 calculates fuel vapor amount to be supplied to a combustion chamber based on the purge concentration and the purge flow rate and sets fuel injection quantity so that an air-fuel ratio may be a target air-fuel ratio by taking into consideration the fuel vapor amount. The ECU 31 corrects the purge concentration by taking into consideration the change of the purge flow rate and determines reflection timing of the corrected purge concentration by taking into consideration a time difference of detection timing for the purge flow rate and timing for actually sucking purge gas detected by the timing into the combustion chamber.
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