| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control system of an engine by which increase in temperature of a HC-trap can be accelerated, while rapidly refluxing HC desorbed from the HC-trap to an intake system. <P>SOLUTION: The exhaust emission control system includes a bypass 15 provided parallel with an exhaust pipe 12 installed in the exhaust system of the engine 1 and the HC trap 16 provided in the bypass. An EGR passage 19 is provided in order to reflux HC desorbed from the HC-trap into the intake system. In order to detect the state of HC desorbed from the HC-trap, a vehicle-speed-sensor, an exhaust-gas temperature sensor 18, a throttle-position sensor 6, etc. are provided. Further, a variable valve timing mechanism 2A capable of changing the EGR amount within the engine, an EGR control valve 20 capable of changing the amount of external EGR refluxed from the EGR passage 19 to the intake system, and an electronic control unit (ECU)8 are provided. If HC desorption from the HC-trap is judged to be insufficient on the basis of detection signals of the vehicle-speed sensor, the exhaust-gas temperature sensor 18, the throttle-position sensor 6, etc., the ECU 8 reduces the amount of internal EGR by the variable valve timing mechanism, and at the same time increases the amount of the exterior EGR by the EGR control valve 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
