PURPOSE: To improve fuel consumption performance and rigidity and prevent deterioration of lubricating oil by decreasing outer diameters of main journals to which an oil passage introducing the lubricating oil to a crank pin is opened compared to those of the remaining main journals with a specified ratio, and providing a means which supplies the low temperature lubricating oil.
CONSTITUTION: Diameters of main journals 12, 14 of a crank shaft 1 are set smaller than those of remaining main journals 11, 13, 15. An oil passage which is opened to the main journals 12, 14 through a hole 20, and opened to a crank pin 2 through a hole 21 is formed inside the crank shaft 1. The temperature of lubricating oil from an oil pump 13 is controlled by an oil cooler 26, a bypass passage 28, a temperature sensor 29, and a control unit C/U to be lower than the temperature of the oil to an oil passage 16, at a part between a sub-gallery 17 and an oil passage 18. It is thus possible to improve fuel consumption performance, prevent seizure or deterioration of the lubricating oil, increase rigidity and decrease oscillations.
MATSUMOTO YASUO
MASUDA GOJI
