Reciprocating piston internal combustion engine

摘要

In a reciprocating piston internal combustion engine its cylinder bores are reduced in the area of the combustion chamber by an annular projection on the cylinder head. In order to permit immersion into the internal space of the annular projection on the compression stroke, the pistons are designed as stepped pistons. The diameter of the fire land on the stepped piston and the diameter of the inside wall on the annular projection are matched to one another in such a way that the fire land, on the upwards stroke of the stepped piston, after immersion into the internal space of the annular projection forms a clearance fit with this with minimum annular clearance and together with the bottom edge on the annular projection projecting radially inwards and a transverse surface on the stepped piston located on the bottom end of the fire land and the wall of the bottom cylinder bore area defines a fresh air buffer space. During the further upwards stroke of the piston the cubic capacity of the fresh air buffer space is reduced, as a result of which the air enclosed in this is compressed to a pressure always in excess of that prevailing in the combustion chamber and in the final stage of the piston stroke also in excess of the ignition pressure. In addition in this process some of the air enclosed in the fresh air buffer space is pumped by way of the annular gap forming a severe restriction into the combustion chamber. The latter at the same time provides for intensive cooling of the wall parts defining the combustion chamber and for intensive swirling of the combustion air enclosed in the combustion chamber.