| 摘要 |
PURPOSE:To display a sufficient HC adsorption effect by an adsorbent trapper by circulating exhaust gas to the adsorbent trapper and a catalytic converter in the optimum circulation condition under respective temperature conditions. CONSTITUTION:A temperature sensor 12 to detect exhaust gas temperature, an adsorbent trapper 1 containing hydrocarbon adsorbent 2, and a catalytic converter 6 containing an exhaust gas purifying catalyst 7 are provided to exhaust gas system pipes 8-10. The pipe 8 on the upstream side of the adsorbent trapper 1 and the pipe 9 in the middle part of the adsorbent trapper 1 and the catalytic converter 6 are connected by a bypass pipe 11, and a switching valve 13 to open/close an opening based on the temperature detected by the temperature sensor 12 is provided in the vicinity of the opening of the bypass pipe 11. With these means, the desorption of HC from the hydrocarbon adsorbent 2 up to the temperature whereat purification by the exhaust gas purifying catalyst 7 becomes possible is prevented. Therefore, HC emission volume can be reduced as a whole. |
