Inner ring unit and tapered roller bearing

A tapered roller bearing, comprising:

• an inner ring unit including an inner ring, a plurality of tapered rollers, and a cage having an annular shape, the inner ring including an inner ring raceway surface, a small rib, and a large rib that is larger than the small rib, the inner ring raceway surface being on an outer periphery of the inner ring, the small rib being provided on a first axial side of the inner ring with respect to the inner ring raceway surface and protruding toward a radially outer side, the large rib being provided on a second axial side of the inner ring with respect to the inner ring raceway surface and protruding toward the radially outer side, the plurality of tapered rollers arranged to roll on the inner ring raceway surface, the cage including a small-diameter annular body, a large-diameter annular body that is larger than the small-diameter annular body, and a plurality of cage bars, the small-diameter annular body being provided on a first axial side of the cage and the large-diameter annular body being provided on a second axial side of the cage, the plurality of cage bars connecting the small-diameter annular body and the large-diameter annular body to each other, the cage configured to hold the tapered rollers in respective pockets, each of which is a space defined between the cage bars adjacent to each other in a circumferential direction of the cage between the large-diameter annular body and the small-diameter annular body, each of the cage bars including a stopper portion that protrudes in the circumferential direction of the cage at an axial intermediate portion of each of the cage bars and is configured to hinder each of the tapered rollers from falling off toward the radially outer side by bringing an axial intermediate portion on an outer peripheral surface of the tapered roller held in the pocket into contact with the stopper portion, the axial intermediate portion on the outer peripheral surface of the tapered roller being disposed on a first axial side of the tapered roller and on a radially outer side of the tapered roller with respect to a center of gravity of the tapered roller;
• and
• an outer ring that is provided on the radially outer side with respect to the inner ring of the inner ring unit,
• wherein each of the stopper portions has a triangular prism shape in which an axial width is gradually decreased as the stopper portion protrudes from each of the cage bars in the circumferential direction of the cage, and a first surface that constitutes the triangular prism shape and that is disposed on the first axial side of the cage with respect to a protrusion edge of the stopper portion is a contact surface that is brought into contact with the axial intermediate portion on the outer peripheral surface of the tapered roller.