To provide a pin coupling structure for the piston-crank mechanism of an internal combustion engine embodied in a full float type without forming any engaging groove at the inside surface of a pin bearing hole and capable of dropping the bearing pressure by enlarging the contacting surface with a first coupling pin 12.
A lower link 13 and an upper link 11 constituting the piston- crank mechanism of double link type are coupled together by the first coupling pin 12 swingably. The first coupling pin 12 has a simple cylindrical surface and is fitted rotatably in the third pin bearing hole 27 in the upper link 11 and the first 24 and second pin bearing holes 25 in the lower link 13. Flanges 31 are mounted at the two ends of the first coupling pin 12 by means of screwing, and thereby the first coupling pin 12 is hindered from slipping off. Because the first coupling pin 12 having a length approximately the same as the thickness of the lower link 13 can be used, the contacting area with the lower link 13 becomes large to lead to lessening of the bearing pressure.
IMAZU MASATSUGU
USHIJIMA KENJI
MOGI KATSUYA
