| 摘要 |
<P>PROBLEM TO BE SOLVED: To rapidly cope with introduction of the large number of fuel steam into a canister due to opening of a blockade valve for blocking a fuel tank to prevent roughness of air-fuel ratio of an internal combustion engine. <P>SOLUTION: A purge fuel concentration variation Δfgpg is calculated (S108) from a tank internal pressure "Ptf" and an output duty "Duty" to the blockade valve, a restriction purge ratio "Ltpg" for preventing roughness of air-fuel ratio to be caused is calculated (S110) from the resultant value, and thereby a purge ratio is restricted (S114 and S116). The restriction purge ratio "Ltpg" is set to restrict the purge ratio with taking an allowance air-fuel ratio on a rich side as limitation. Accordingly, even purge fuel concentration is suddenly made high concentration due to the opening of the blockade valve, a purge amount is restricted by the purge ratio in response to the high concentration to prevent the case where mixture is largely unbalanced to the rich side. As a result, the opening of the blockade valve is rapidly coped with, and the roughness of air-fuel ratio is prevented. <P>COPYRIGHT: (C)2013,JPO&INPIT |
