| 摘要 |
<p>PURPOSE:To provide the captioned device having simpler structure and increased durability and safety for lowering an operational cost, by compensating for a reducing air volume which can take place through an engine throttling operation with a secondary air introduced into an upstream of trap. CONSTITUTION:A trap 23 has a secondary air supplying tube 21 provided at an upstream end thereof, the tube 21 having an outlet end 20 opened to the trap inside. The secondary air supplying tube 21 is connected with an air pump via an opening/closing control valve 22. The control valve 22 is adapted to selectively supply the second air to an upstream of arresting material 28. That is, by throttling a throttle valve 6 for refreshing a trap, an exhaust is raised its temperature and such a heat is used for burning fine particles arrested in the trap. At this moment, O2 concentration in the exhaust is apt to decrease and as a result an air volume necessary for buring the fine particles becomes deficient. To overcome such a problem, a fresh air necessary for refreshing the trap is forcibly drawn from atmosphere.</p> |
