| 摘要 |
PROBLEM TO BE SOLVED: To eliminate projection of a holding part holding a duct wall to improve loading ability and maintain the sound absorbing effect of the duct wall for a long term by containing fiber of heat shrinkage in the duct wall made of porous material, and fitting the duct wall to a main body through heat shrinkage of the heat shrinkable fiber. SOLUTION: A cylindrical duct wall 20 is formed into a porous construction, in which a weft (axial direction) fiber body and a warp (circumferential direction) fiber body are knitted together. At least, the warp fiber body is contained with a polyethylene series fiber body which shrinks at a fixed shrinkage factor at applying heat thereto. When the duct wall 20 is fitted to a duct main body 10, the duct wall 20 is inserted through the duct main body 10 and positioned on the fitting part 14, and the duct wall 20 is heated in this condition. Then the warp fiber body is shrinked in the circumferential direction to make small the inner diameter of the duct wall 20, the duct wall is stuck onto the fitting part 14 of the duct main body 10 by the shrinkage force to cover small holes 12, and this condition is maintained.
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