| 摘要 |
PROBLEM TO BE SOLVED: To remarkably reduce an HC discharge amount during starting of an engine. SOLUTION: An upstream catalyst 17 is installed in the vicinity of the exhaust manifold 19 of an engine 11, and an HC absorbent 20 and a downstream catalyst 18 are installed in series in a spot situated downstream therefrom. During unactivation of the catalyst on the upstream catalyst 17, HCX passing through the upstream catalyst 17 is absorbed at the HC adsorbent 20. After activation of the upstream catalyst 17, HC effecting desorption from the HC adsorbent 20 is returned to the spot, situated upper stream, of the upstream catalyst 17 through a return flow passage 26 and purified by the upstream catalyst 17. In this case, an ECU 28 executes catalyst rapid warming-up control (, for example, ignition timing delay control and air-fuel ratio lean control) from a time right after starting and rapidly increases the temperature of the catalyst 17 on the upper stream side from a time right after starting, and a time in which activation is completed is shortened. This constitution reliably activates the upstream catalyst 17 before an HC adsorption amount of the HC adsorbent 20 attains a saturation level and reliably purifies the desorption HC and remarkably reduces an HC discharge amount during starting. |
