Exhaust gas purifying apparatus for internal combustion engine

摘要

An exhaust gas purifying apparatus for an internal combustion engine is provided for simultaneously realizing sufficient recovery of the adsorbing capability of an adsorbent and limitation to an increase in exhaust resistance. The exhaust gas purifying apparatus for an internal combustion engine comprises a flow path switching valve for switching an exhaust gas flow path to a bypass exhaust passage or to a main exhaust passage, three-way catalysts, and an HC adsorbent arranged in the bypass exhaust passage for adsorbing hydrocarbons in exhaust gases and fully desorbing the adsorbed hydrocarbons when it is heated to a full desorption temperature or higher. A troidal passage of the main exhaust passage completely surrounds a portion of the bypass exhaust passage in which the HC adsorbent is arranged. A ratio S1/S2 of the cross-sectional area S2 of the troidal passage to the cross-sectional area of a flow-in passage is set in a range from 1.0 at which the exhaust resistance begins gradually decreasing as the ratio S2/S1 increases to 3.0 at which the HC adsorbent can be heated to the full desorption temperature or higher.