To suppress sliding abrasion and to improve impulse resistance by containing micro particles with size smaller than a clearance formed with a shaft and a sleeve in lubricating oil filled into a bearing.

A clearance R is radially provided between a shaft 5 and a sleeve 6, lubricating oil 4 is filled into a bearing, and this contains micro particles 1 with size smaller than the clearance R. At this time, the shaft 5 and the sleeve 6 respectively come into contact with the micro particles 1, and the micro particles 1 circulate in the bearing, so that the micro particles 1 related to the contacts with the shaft 5 and the sleeve 6 always exchange with each other, and contact points depend on the circulation movement of the micro particles 1. Therefore, the sliding track of the surface of the shaft 5 and the inner peripheral surface of the sleeve 6 are not always same, and abrasion resistance can be improved. The micro particles 1 can cool heat occurring by contact of the micro particles 1 on the entire surface, prevent thermal degradation of the lubricating oil 4 to extend service life, and improve impulse resistance.