| 摘要 |
An exhaust gas control valve includes a valve seat, a valve plate having a first exhaust gas pressure receiving area corresponding to an opening area and a second exhaust gas pressure receiving area larger than the first area; and a spring for closing the valve. In a closed state, gas pressure during a low engine speed operation acts on only the first exhaust area for shutting the opening. In an intermediate state, the pressure during a the middle engine speed operation acts on the first and second areas for opening the opening but closing the valve by overlap of wall portions of the valve plate and the valve seat overlap. In an opening state, the pressure during a high engine speed operation acts on the first and second areas for forming a gap between the wall portions to pass the gas therethrough.
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