| 摘要 |
In a reciprocating-piston internal combustion engine, its cylinder bores are reduced in the area of the combustion chamber by the through-bore of an annular insert. In order to permit immersion into the through-bore of the insert during the compression stroke, the pistons are designed as stepped pistons. The diameter of the piston in the area of its fire land and the diameter of the through-bore in the insert are so matched to one another that the fire land, during the upward stroke of the piston, after immersion into the through-bore of the insert, forms a clearance fit with this through-bore with minimum annular gap and, together with the bottom edge of the insert projecting radially inwards and a transverse surface, located on the bottom end of the fire land, on the piston and together with the cylinder bore wall, defines a fresh air buffer space. During the further upward stroke of the piston, the volume of the fresh air buffer space is reduced, as a result of which the air enclosed in this is compressed to a pressure always exceeding that prevailing in the combustion chamber and in the terminal stage of the piston stroke also in excess of the firing pressure. In addition, in this process a part of the air enclosed in the fresh air buffer space is pumped into the combustion chamber by way of the annular gap forming a strong restrictor. At the same time the latter provides for intensive cooling of the wall parts defining the combustion chamber and for an intense swirling of the combustion air enclosed in the combustion chamber.
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