| 摘要 |
<p>PURPOSE:To increase the reliability of an exhaust emission control device by providing a main passage and a by-pass passage with an adsorbent interposed therein, in parallel upstream of the catalyst of an exhaust passage, and controlling the exhaust flow ratio of both passages from the degree-of-degradation of the catalyst, the exhaust gas temperature, and the like according to the operating state of an engine so as to desorb HC from the adsorbent according to the degree of degradation. CONSTITUTION:Part of the exhaust passage 13 of an engine 11 is formed of a main passage 13a and a by-pass passage 14 with an adsorbent 15 interposed therein. A pre-three-way catalyst 19a and a main three-way catalyst 19b are provided upstream and downstream of both passages 13a, 14, and oxygen sensors 21a, 21b are provided. The degree-of-degradation of the three-way catalyst 19b is obtained from the oxygen sensors 21a, 21b, and the opening of a control valve 16 is controlled by the output of an exhaust gas temperature sensor 22. When the temperature of the exhaust gas is low, the exhaust gas is made flow mainly to the adsorbent 15 side, and part of the exhaust gas is made flow to the catalyst 19b side to accelerate temperature rise. Upon exceeding the specified temperature, a flow ratio on the by-pass passage 14 side is made zero. The opening of the control valve 16 is regulated according to the operating state so as to desorb HC from the adsorbent 15. The reliability of an exhaust emission control device is thus increased.</p> |
