Plunger piston for internal combustion engines

In a plunger piston for internal combustion engines, having a cylindrical piston head with an annular ring zone having annular grooves therein for receiving piston rings, a cylindrical piston skirt having a distal end, and gudgeon pin bosses with coaxial gudgeon pin bores therein for containment of a coacting gudgeon pin, said bosses extending perpendicularly from the piston head into a space within the piston skirt and having radially outer boss faces, the improvement comprising selecting the following ratios and dimensions

• (H/D)=0.20-0.35
• (T/D)=0.22-0.38
• (A/D)=0.15-0.25
• (B/D).ltoreq.(A/D)
• wherein D=piston diameter
• H=compression height between a top of the head and the gudgeon pin bore axis
• T=distance from the radially outer boss faces to the piston axis
• A=axial skirt dimension below annular groove nearest the pin bore axis at a peripheral zone of the skirt extending over an angle .alpha. of 15 to 60 degrees to either side of a connecting rod oscillating plane
• B=axial skirt dimension below said annular groove in a direction along said gudgeon pin axis;
• and further wherein the distal end of the skirt is reduced radially over an axial dimension of 10-25% of an axial length of the skirt in said direction along said gudgeon pin axis, said distal end being reduced at its edge by 0.01-0.15 mm.