| 摘要 |
PROBLEM TO BE SOLVED: To provide a rolling unit having a superior wear-resistant property under conditions easily causing poor lubrication for along time and capable of easily manufacturing at low cost. SOLUTION: A ball bearing 1 comprises an inner ring 1, an outer ring 3, a plurality of balls 4 rotatably arranged between the inner ring 2 and outer ring 3, and the balls 4 is made of ceramic. A rate of pores whose diameters of the corresponding circles are 2 to 15μm among all pores in the balls 4 is 50% or more, and the number of pores whose diameters of the corresponding circles are 2 to 15μm is 500 to 10,000 pieces per 1 mm<2> .
|
