| 摘要 |
PURPOSE:To obviate the need of the burr removing work and achieve cost cut and improve lubricity by forming a plurality of recessed parts on the skirt part on the outer periphery of a piston and drilling an oil reservoir and small holes which penetrate through the inside at the center part of the recessed part according to necessity. CONSTITUTION:A plurality of recessed parts 3 are formed on the lower part skirt part 2 on the outer periphery of a piston 1. The recessed part 3 is formed into an oil storage, and lubricating oil can be stored. If the situation is not sufficient by only foring the recessed part 3, small holes 4 are formed by a stwisting drill, and even if burrs are left, the burrs are formed on the recessed part, and no burr is formed on the side having sliding surface for a cylinder, and the need of burr removing work is obviated. The lubricating oil splashed up from inside is introduced into the small hole 4, and the stay of the lubricating oil in the recesed part 3 is improved further, and sufficient lubrication is permit ted. |
