| 摘要 |
PROBLEM TO BE SOLVED: To use inexpensive plastic parts when exhaust gas recirculation is employed by arranging a means capable of cooling a valve sleeve in a contact area between the valve sleeve and an air intake duct so as to correspond to the valve sleeve. SOLUTION: When an internal combustion engine is operated, a valve sleeve 34 is normally loaded by exhaust gas having the temperature of about 40 deg.C through a pipe. The hot exhaust gas gives a great part of its heat energy to the valve sleeve 34, and a greater part of heat is transmitted to a flange 50 through a contact surface 52. The flange 50 has a large radiating area, and the valve sleeve 34 can continuously take out heat from the exhaust gas. Further, a partial air flow 68 having relatively lower temperature or the temperature of fresh air is guided around a reduced diameter portion 44 of the valve sleeve 34 to discharge a large part of residual heat. Thus, the contact surface of exhaust gas with the valve sleeve 34, especially a wall part 36 made of plastics is cooled up to the temperature below the melting point of plastics. |
