Lubricating structure of multi-link piston-crank mechanism of internal combustion engine

摘要

PROBLEM TO BE SOLVED: To ensure the hardness of a pin boss portion and to improve lubrication performance to a pin shaft bearing part, with a structure which injects and supplies lubricant from a lower link to the pin boss portion of an upper link.SOLUTION: On a lower link 4, a lower link oil passage 22 penetrating a pin boss opposite surface 4C opposing to a pin boss portion 5A of an upper link 5, and a bearing surface of a crank pin 3 is formed. At a predetermined crank angle, a crank pin oil passage 21 formed on the crank pin 3 and the lower link oil passage 22 are communicated to inject and supply lubricant to the pin boss portion 5A. At that time, on a straight line 25 connecting a rotation center sA of a crank shaft and an end portion 22A on the pin boss opposite surface side of the lower link oil passage 22, the pin boss portion 5 to be supplied the lubricant is disposed. On an axial side surface of the pin boss portion 5A, a recessed portion 23 depressed in an axial direction is provided.SELECTED DRAWING: Figure 2