Abstract: The raceway groove width (W) of the inner ring 2 and the length (L) of the tapered roller 3 are finished within predetermined dimensional tolerances. The retaining rib face 2b of the inner ring 2 is machined such that it is a surface parallel to the small end faces 3b of the tapered rollers 3. The clearances .delta. which are defined when the tapered rollers 3 are disposed on the raceway surface 2a of the inner ring 2 and are contacted at the large end faces 3a thereof with the cone back face rib face 2c is secured to be within the dimensional range, .delta..ltoreq.0.4 mm.

Abstract: An autotensioner for a belt has a pulley support shaft secured to a base and an eccentric ring rotatably supported by the pulley support shaft with the center of its outer peripheral surface offset from the center of the pulley support shaft. A pulley is rotatably supported around the eccentric shaft through a rolling bearing. A spring for biasing the eccentric ring is provided to press the pulley against the belt. A damper for imparting resistance to rotation to the eccentric ring is provided to restrain the pivoting motion of the pulley. The resistance to rotation is imparted to the eccentric ring by the damper at the side of the rolling bearing opposite to the base.