PURPOSE: To increase the quantity of feeding oil by providing an oil feeding groove for transferring a lubricating oil from one side bearing to the other side bearing on the eccentric part of a rotary shaft being formed along its peripheral direction centering around the axis of a main bearing part.

CONSTITUTION: An oil pump 11 is connected to a main bearing 7 to feed a lubricating oil along a rotary shaft 4. An oil feeding groove 14 is formed on the eccentric part 6 of the rotary shaft 4 while a sub-shaft side oil groove 15 is formed on a sub-shaft part 4b. Thereby, a large centrifugal force can be applied to and transfer a lubricating oil which passes through the oil feeding groove 14, enabling a sufficient quantity of lubricating oil to be fed to a sub- bearing 8.