Air inlet structure for exhaust passage in engine

摘要

An internal combustion engine has a cylinder assembly including a cylinder block and a cylinder head mounted thereon, the cylinder assembly having an exhaust passage defined in the cylinder block and a water jacket defined therein around the exhaust passage. A water jacket cover is mounted on an outer surface of the cylinder block in covering relation to the water jacket, and has an opening defined therein. The cylinder block has an air inlet passage defined therein across the water jacket and communicating with the opening and the exhaust passage. A valve cover is mounted on an outer surface of the water jacket cover. The water jacket cover and the valve cover jointly define a valve chamber therebetween. A valve is disposed in the valve chamber for selectively introducing air from the valve chamber through the opening and the air inlet passage into the exhaust passage to assist in burning harmful unburned components contained in an exhaust gas flowing through the exhaust passage. The water jacket is positioned between the exhaust passage and the valve for preventing the valve from being adversely affected by the heat of the exhaust gas flowing through the exhaust passage.