| 摘要 |
An internal combustion engine including an air intake manifold having a rotary valve for regulating air flow within the manifold. The valve comprises a cylindrical shaft formed of stainless steel and butterfly vanes formed of plastic overmolded onto the shaft. The composite valve has a natural frequency of about 300 Hz and can resonate with engine noise. In accordance with the invention, the valve shaft is additionally provided with one or more sound-absorbing elastomeric dampers, formed preferably of a silicone rubber, that make contact with saddles in the intake manifold for extinguishing harmonic frequency response of the valve below 660 Hz. Preferably, the plastic butterfly vanes also are overcoated with the elastomer to further damp harmonic flexure and wave propagation in the valve.
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