To improve fuel economy upon automatic restart in an idling-stop vehicle.
A bypass passage 9 in which a bypass catalyst 8 is arranged is connected to an upstream portion of a main passage 7 in which a main catalyst 6 is arranged, in parallel with the main passage 7. A selector valve 10 capable of closing the main passage 7 is arranged at the portion of the main passage 7 from which the bypass passage 9 branches. Automatic stop of an engine 1 is performed after scavenging for a predetermined period of time after fuel cut. During the scavenging, the temperature of the bypass catalyst 8 is so controlled as to be within a predetermined temperature range and the main passage 7 is closed by the selector valve 10. Thus, because the main catalyst 6 can be used in a stoichiometric atmosphere upon the automatic restart of the engine, it is possible to relatively reduce a fuel injection amount and to improve the fuel economy.
COPYRIGHT: (C)2009,JPO&INPIT
Tetsuro Goto
Koichi Mori
Hironobu Yoshida
Masahiro Hirano
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Tomioka Kiyoshi
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