| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control system comprising two exhaust emission control devices arranged in series upstream and downstream in an exhaust passage of an internal combustion engine and a bypass passage for letting exhaust gas bypass the upstream exhaust emission control device and performing temperature rise control of both the exhaust emission control devices with simpler construction and control. <P>SOLUTION: When a temperature rise treatment of both the exhaust emission control devices is performed, fuel is added to exhaust gas on a more upstream side of the upstream exhaust emission control device (S104) and an air-fuel ratio of exhaust gas introduced into the upstream exhaust emission control device is lowered below the stoichiometric air-fuel ratio. The upstream exhaust emission control device is raised in temperature and excess fuel is supplied to the downstream exhaust emission control device as it remains unreacted. The supplied fuel is reacted with exhaust gas from the bypass passage and the downstream exhaust emission control device is raised in temperature. At that time, a quantity of fuel added from a fuel addition valve is set to be a quantity corresponding to a temperature raising amount required to the downstream exhaust emission control device (S101-S103). <P>COPYRIGHT: (C)2009,JPO&INPIT |
