Tapered roller bearing

A tapered roller bearing of an inner ring guidance design comprising:

• an inner ring having a raceway surface and having opposite ribs including a smaller rib and a larger rib;
• an outer member having an annular raceway surface in opposition to the raceway surface of the inner ring;
• a plurality of tapered rollers interposed between the inner ring and the outer member;
• and
• a cage retaining the plurality of tapered rollers, the cage including a smaller diameter annular part, a larger diameter annular part, and pillars connecting the smaller diameter annular part and the larger diameter annular part at more than one circumferential location, the pillars being adjacent to each other to define, therebetween, pockets in which the tapered rollers are retained, the smaller diameter annular part and the smaller rib of the inner ring defining a smaller diameter-side clearance S1 therebetween, the larger diameter annular part and the larger rib of the inner ring defining a larger diameter-side clearance S2 therebetween, and the tapered roller bearing defining a dimensionless number Y which is in the range of at least 0.39 to no more than 0.88 according to the following equation (1):
• Y
• =
• (
• S
• ma
• ⁢
• x
• /
• S
• 3
• )
• ×
• (
• d
• /
• 1
• )
• (
• 1
• )
• where d is a mean roller diameter, l is a roller length, S3 corresponds to the equation:
• S3=(W/2)/tan θ−(PCD/2+(d/2)/sin θ−((D/2)2−(W/2)2)1/2), Smax is chosen from the maximum values of S1 and S2, W is a pocket width representing a width of a pocket at a location that corresponds to the mean roller diameter d, θ is a pillar angle which is a half of an angle formed, in a section corresponding to the mean roller diameter d, by surfaces of adjacent pillars that make contact with a tapered roller located in between, PCD is a diameter of roller centers representing a pitch circle diameter of an arrangement of the tapered rollers, and D is a cage inner diameter representing an inner diameter of the cage.