Foley & Lardner
Exhaust emission control device for engine
 A three-way catalyst (9) which has an oxygen storage capacity is disposed in an exhaust passage (3) and HC adsorbent-catalysts (10, 11) which can adsorb and oxidize HC are disposed further downstream. If release of HC from the HC adsorbent-catalysts is determined, the lean level of an air-fuel ratio is increased temporarily after HC release is commenced. Thereafter the air-fuel ratio is controlled to a lower lean level which corresponds to an HC concentration during release. In this way, after lean control is commenced, the three-way catalyst is saturated in a short time and oxygen is sent to the HC adsorbent-catalysts (10, 11) and released HC is oxidized. 
Nissan Motor Co., Ltd.
F B Y B F F F F F F
F02D B01D Y02T B01D F01N F02D F01N F01N F01N F02D
inventional inventional additional inventional inventional inventional additional inventional inventional inventional
Kimiyoshi Ritsuo Mikio
Nishizawa Sato Tsuzuki