| 摘要 |
PURPOSE:To prevent a back flow of exhaust gas to a secondary air passage at the time of blow down, by providing a valve device which is closed by interlocking with an intake and an exhaust valves at an exhaust valve location where a blow down is generated in the secondary air passage which opens in an exhaust passage. CONSTITUTION:When an exhaust valve 16 is seated on a valve seat 17 as shown by a dotted line a groove 16a of a valve stem 16' is connected with a secondary air nozzle 20a of a tip loop part 20' of a secondary air duct 20. In this instance, when negative pressure is existing in an exhaust port 12, a reed valve 26 is opened and fresh air is led to the exhaust port 12 from the secondary air nozzle 20a for removal of ingredients of CO and HC in exhaust gas. Then, the above nozzle 20a is sealed with the stem part 16' and the secondary air passage 20 is closed to the exhaust port 12 when the exhaust valve 16 starts to separate from the valve seat as shown by a full line. Then, a back flow phenomenon of the exhaust gas to the secondary air duct at the time of blow down of exhaust gas is prevented from occurring. |
