| 摘要 |
<P>PROBLEM TO BE SOLVED: To accurately calculate the engine intake air flow rate upon supplying secondary air. <P>SOLUTION: A NOx occlusion reduction catalyst 40 is arranged in a discharge passage 3 in an internal combustion engine having a variable valve system 60. Upon raising the temperature of the catalyst 40 for sulfur poisoning detoxification, the engine 1 is operated at a rich air-fuel ratio and secondary air is supplied to an intake passage 2 on the downstream side of a supercharger 35. An electronic control unit (ECU) 30 calculates the engine intake air flow rate based on the output of an air flow meter 10 arranged at the intake passage entrance in operation other than during supplying of secondary air. When supplying secondary air, changing of a valve-opening characteristic of a cylinder valve by a variable valve device 60 is prohibited, the valve-opening characteristic of each of the valves is fixed to a state wherein cylinder pump loss is at the maximum, and the engine intake flow rate is calculated based on the output of an intake air pressure sensor 15 in place of he airflow meter 10. The engine air flow rate thereby is accurately calculated during supplying of secondary air. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
