| 摘要 |
PURPOSE:To dispense with any machining for a conventional escape groove, by forming an escape opening, to be interconnected to a piston inner wall surface, in a ring groove at the lowermost part of plural ring grooves installed in a piston outer wall surface with each partial notch at a lower surface part of this ring groove and the inmost recess part. CONSTITUTION:In a piston 4 of an internal combustion engine, both first and second ring grooves 12, 14 and an oil scraping groove 16 are formed in the ring part 8 in order from the upper part, and each of pressure rings 24 and 26 is attached to these ring grooves 12 and 14 respectively. In addition, a combinational oil scraping ring 28 is attached to this oil scraping ring groove 16. In this case, a concavity 32 is formed in a piston inner wall surface 4b in a part of the ring part 8 of the piston 4 so as to interconnect a part of a lower surface part 16a of the oil scraping ring groove 16 and a part of the inmost recess part 16b by means of cast molding or the like. And, at the time of machining the oil scraping groove 16, a part of the lower surface part 16a of this groove 16 and a part of the inmost recess part 16b are opened to the concavity 32, and this opening is set down to an escape opening 34. |
