US Patent 7435007 Self-aligning roller bearing

A roughness of an outer ring raceway surface 14 formed on an inner peripheral surface of an outer ring 13 is made larger than a roughness of inner ring raceway surfaces 12a, 12b of an inner ring 11. Also, an average roughness Ra of the outer ring raceway surface 14 is set within 0.1 μm≦Ra≦0.5 μm in an axial direction and a circumferential direction in ranges of b1/(B/2)≦0.9, b2/ (B/2)≦0.9 and in a measured length of 0.1 mm to 1.0 mm where B is a width of the outer ring 13 and b1, b2 are a distance from both end surfaces of the outer ring 13 in the axial direction respectively. A roughness parameter S of the outer ring raceway surface is set within 0<S≦20 μm.