Exhaust gas-purifying system for internal combustion engines

An exhaust gas-purifying system for an internal combustion engine having an exhaust passage, comprising:

• unburnt gas component-adsorbing means arranged in said exhaust passage of said engine, for adsorbing unburnt gas components present in exhaust gases emitted from said engine;
• at least one exhaust gas-purifying catalyzer arranged in said exhaust passage at a location downstream of said unburnt gas component-absorbing means, for purifying exhaust gases;
• a bypass passage bypassing said unburnt gas component-absorbing means, said bypass passage having an upstream end thereof connected to said exhaust passage to form a branchpoint together therewith;
• a changeover valve arranged in said exhaust passage at said branchpoint, for selecting a first flow path in which exhaust gases are guided to said unburnt gas component-adsorbing means, or a second flow path in which exhaust gases are guided through said bypass passage;
• first exhaust gas concentration sensor means arranged in said exhaust passage at a location upstream of said unburnt gas component-adsorbing means;
• second exhaust gas concentration sensor means arranged in said exhaust passage at a location downstream of said unburnt gas component-adsorbing means;
• and
• control means for controlling said changeover valve to select said first flow path or said second flow path, based on outputs from said first and second exhaust gas concentration sensor means.