Self-aligning roller bearing

A self-aligning roller bearing comprising:

• an outer ring having an outer raceway surface that is a recessed curve on an inner periphery of the outer ring;
• an inner ring having two rows of inner raceway surfaces that are recessed curves side by side on an outer periphery of the inner ring and having a rib portion at each axially outward end;
• a plurality of spherical rollers disposed between the outer raceway surface and the inner raceway surface in two rows side by side;
• a cage having a plurality of pockets that accommodate the spherical rollers to hold each row of the spherical rollers at intervals in a circumferential direction;
• and
• a guide ring disposed between the cage and the inner ring as well as between the two rows of the spherical rollers, wherein
• in a longitudinal section viewed from a direction perpendicular to a center line of one of the plurality of spherical rollers and directed toward an axis of the self-aligning roller bearing, a clearance X between an outer end surface of the spherical roller on an axially outer side of the self-aligning roller bearing and the rib portion, and a clearance Y between an inner end surface of the spherical roller on an axially inner side of the self-aligning roller bearing and the guide ring have a relation of X<Y−ΔS, where ΔS is a difference between S1 and S2, S1 is a difference between (i) a clearance between an axially inner side surface of the rib portion and the outer end surface of the spherical roller that faces the axially inner side surface at the center line and (ii) a clearance between an axially inner side surface of the rib portion and the outer end surface of the spherical roller that faces the axially inner side surface at a radial distance from the center line in the circumferential direction, and S2 is a difference between (i) a clearance between an axially outer side surface of the guide ring and the inner end surface of the spherical roller that faces the axially outer side surface at the center line and (ii) a clearance between an axially outer side surface of the guide ring and the inner end surface of the spherical roller that faces the axially outer side surface at the center line at the radial distance from the center line in the circumferential direction, and
• in the longitudinal section, the inner side surface of the rib portion is formed as an arc surface, and the outer side surface of the guide ring is formed as an arc surface, and the outer end surface and the inner end surface of the spherical roller are each formed as a flat surface.