| 摘要 |
<p>PROBLEM TO BE SOLVED: To perform a high inner surface size accuracy simultaneously upon molding by specifying a material hardness by a duct having an undercut part obtained by injection molding a polyolefin thermoplastic elastomer, thereby incorporating a flexibility and a strength similar to those of a vulcanized rubber. SOLUTION: The resin duct 1 is used as an air duct for coupling an engine body of an automobile to an air cleaner. And, its both ends 6 are connected fixedly to the body or the cleaner by clampers. The duct 1 is integrally formed by injection molding a polyolefin thermoplastic elastomer as a molding material. A bellows part 2 in which a plurality of large diameter ridges 3 and a plurality of small diameter troughs 4 are alternately formed along a duct axially central direction is formed near a lengthwise central part. A hardness Hs (JISA) of the used resin is in a range of 50 to 95. Its hardness is performed by selecting types and amounts of sub-materials such as a plasticizer, filler, coloring agent and the like to be blended and kneaded with the resin.</p> |
