| 摘要 |
<p>In the stationary and/or the movable valve part (1, 4) of the exhaust valve there is provided an annular chamber (9) formed as a circumferential recess in the surface of the valve part (4) in question facing the other valve part. The annular chamber is located intermediate the seating surfaces (5, 6) of the valve parts and the combustion chamber (10) of the engine cylinder and it communicates with the combustion chamber through a relatively narrow inlet when the valve is closed. During the compression period of the engine cylinder's working cycle the annular chamber is filled by pure and relatively cool air, and if local gaps are present between the seating surfaces, that air acts as a barrier preventing the leakage of substantial amounts of hot and aggressive combustion gases through the gaps during the initial part of the expansion period. This prevents the valve parts from being subjected, adjacent to said gaps, to a high temperature rise and concomitant heavy corrosive attacks which would lead to a rapid enlargement of the gaps. The invention, therefore, prolongs the lifetime of the valve by delaying the moment when a refurbishing of the seating surfaces becomes necessary.</p> |
