| 摘要 |
<P>PROBLEM TO BE SOLVED: To suppress the generation of large vibration of a cantilever supported secondary vibration mode due to resonance when a catalyst is provided in a collection section. Ž<P>SOLUTION: In this exhaust collecting pipe 1, the catalyst 5 is provided in the collection section 4, and the position of the catalyst 5 is determined so that the vibrational frequency of the cantilever supported secondary vibration mode with a mounting part 2 as a support point becomes higher than the upper limit frequency of the abnormal noise generating frequency band of an engine 50. When the position of the catalyst 5 is determined, a frequency f represents the vibrational frequency of the cantilever supported secondary vibration mode when included in the abnormal noise generating frequency band, and length L represents the whole length with the catalyst 5 as a rear end when the vibrational frequency of the cantilever supported secondary vibration mode is the frequency f. In this case, length L' calculated in a manner that the frequency f is divided by a frequency higher than the upper limit frequency in the abnormal noise frequency band and subsequently multiplied by the L is regarded as the whole length. Further, in comparison with the case that the whole length is the L, the length of the part of the collection section 4X, located upstream of the catalyst 5, is shortened by a difference between the L and the L'. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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