PURPOSE: To prevent the occurrence of fretting abrasion between the large end parts of a connecting rod and the outer peripheral surface of a bearing metal.
CONSTITUTION: Large end holes 17 are provided on the large end parts 15 of a connecting rod 13, and here, connecting rod metals 18 and 19 are engaged. The crank pin of a crank shaft is supported by the connecting rod metals 18 and 19. Communicating holes 28, guiding lubricating oil supplied from the crank pin side to the connecting rod metals 18 and 19 and the engaged parts of the large end parts 15, are provided on the connecting rod metals 18 and 19. Oil grooves 31, having a ratio of the area of them to the surface area of the large end part 15 in an engaged part of 0.1-0.4 and a width of 30-100μm, are formed on the nearly whole surface of the inner peripheral surface of the large end holes 17. Both the ends of the oil grooves 31 are opened in the axis line direction end surface 15a of the large end parts 15 in order to guide the lubrication oil, introduced into the oil grooves 31 via the communicating holes 28, outside the engaged part.
NAKAKOHARA TAKESHI
FUWA YOSHIO
