| 摘要 |
Sparking across between metal objects, when in close proximity, is an unwanted occurrence when microwave radiation is present. This phenomenon could seriously impair the performance and even cause damage to an internal combustion engine when running, eg by pre-ignition, if microwaves are present within the cylinder. To reduce this problem, non-metallic materials, eg suitable glasses and ceramics, are used for the valves, valve guides and/or piston rings. A valve made mainly of steel may have a partial coating of non-metallic material; a valve made entirely of non-metallic material may have a metal cap at the end of the stem to resist wear by the tappet or cam. To prevent chance sparks between the piston rings and the piston or the cylinder wall, piston rings of non-metallic material may replace the conventional metal rings, or an additional piston ring may be provided above the usual topmost ring. |
