| 摘要 |
PURPOSE: To sufficiently eliminate poisonous elements in exhaust gas by means of a thin catalyst even under a low load operation area by arranging the thin catalyst and an exhaust control valve on the way of an exhaust passage of an internal combustion engine. CONSTITUTION: A valve case 11 of an exhaust control valve 10 is integrally fixed to a downstream end, while a flange 12 is formed on a downstream end of the valve case 11. In the valve case 11, a disc-like valve body 14 is integrally fixed to a valve shaft 13 penetrating in a diameter direction. A communication hole 14a is formed on the valve body 14. A thin catalyst 15 is concentrically fitted into an exhaust pipe 9 through an elastic holding member 17. A clearance 14 of a measurement δ is set between an inner peripheral surface of the exhaust pipe 9 and an outer peripheral edge 14b of the valve body 14 which is farthest from the valve shaft 13 under the state that the exhaust control valve 10 is throttled uppermost. The measurement δis substantially equal to a spacing (d) between the inner peripheral surface of the exhaust pipe 9 and the inner peripheral surface of the thin catalyst 14, or slightly larger than that. Even when the exhaust control valve 10 is closed uppermost, not only the exhaust communication hole 14a but also the clearance 14c serving as a communication passage are functioned. |
