| 摘要 |
PROBLEM TO BE SOLVED: To quickly recover the storage quantity of a catalyst at the time of restarting an engine by calculating the storage quantity of the catalyst set in an exhaust passage, and correcting a target air-fuel ratio to rich side according to the storage quantity calculated in the previous operation at the time of restarting the engine. SOLUTION: A three way catalyst 21 and a NOx occlusive reduction type three way catalyst 23 are vertically set in the exhaust passage 15 of an engine body 2. A control unit 11 controls the fuel quantity to be injected from an injector 14 set in an intake passage 12 on the basis of each detection signal from a crank angle sensor 32, an O2 sensor and an air flow meter 33 to ensure an intended air-fuel ratio. In the control unit 11, the O2 storage quantity of storing oxygen of each catalyst 21, 23 is calculated. At the time of restarting the engine body 2, the air-fuel ratio is corrected to rich side according to the increase in O2 storage quantity detected in the previous operation to quickly recover the purifying performance of each catalyst 21, 23. |
