Trunk piston for internal combustion engines

摘要

In a reciprocating piston, especially one of metal, for internal combustion engines, it is proposed to improve the exhaust emission performance by means of a tighter radial clearance between the piston top land and the cylinder wall guiding the piston. The intention is that, despite a low top land clearance, there should be no risk of friction on the piston or the cylinder wall due to too tight a clearance. To this end the piston top land is coated with a layer which has a lower abrasion resistance than the top land base material, the diameter of the coated top land being designed for a clearance in relation to the cylinder guiding the piston, which is less than the minimum which would be admissible for a serviceable piston in engine operation in the absence of a coating.