| 摘要 |
PURPOSE: To keep sounds caused inside a resin cover covering one side of a member having a noise source therein from being transmitted through the cover so that the transmitted sounds can be reduced by machining the interior wall of the cover so that it has projecting and recessed portions. CONSTITUTION: A cylinder head cover 1a made from a resin, when employed as the cylinder head cover of an engine, is formed into a single-layer structure made from a resin material containing a fiber reinforced material 2a, with cover-reinforcing ribs 3a... formed on the interior wall of the cylinder head cover 1a. In such a cylinder head cover 1a, the wall surface of the cover is machined to have projecting and recessed portions 4a except at the ribs 3a. Thus sounds caused inside the cover are absorbed by the recessed portions so as to reduce resonating sounds that echo inward from the interior wall, and the sounds transmitted through the projecting portions are absorbed by the accumulation of sound pressure vibrations inside the projecting portions, with the result that the transmitted sounds can be reduced. |
