| 摘要 |
PROBLEM TO BE SOLVED: To improve a cooling capacity of a piston by securing an angle in the vertical direction of an inlet hole or an outlet hole so as to make at least either hole of both first and second communicating holes promote the circulation of oil in a cavity for cooling use by blow-by gas. SOLUTION: Blow-by gas so far passing through two compression rings 43 and 44 flows into an inner space of a low pressure piston from a combustion chamber after passing a first communicating hole 39 and a second communicating hole. For example, since the fist communicating hole 39 has an angleα(0<α<90 deg.) to a direction vertical with the outlet hole 37 so as to head for an apex 31a of a piston head in proportion as heading for an oil ring groove 32 from the outlet hole 37, a cooling cavity 36 turns to negative pressure against the outlet hole 37 by means of the blow-by gas reaching to this hole 37 after passing the first communicating hole 39, whereby oil in the cooling cavity 36 is discharged into the piston inner space via the outlet hole 37.
|
