1. Field of the Invention
The invention relates to tapered roller bearings and power transmission devices.
2. Description of the Related Art
Tapered roller bearings are characterized by larger loading capacity and higher rigidity compared to other rolling bearings of the same size. The tapered roller bearings are therefore used for drive transmission devices such as differential gear units and transaxle units in automobiles that require such characteristics. FIG. 10 is an axial section of a conventional tapered roller bearing. As shown in FIG. 10, a tapered roller bearing 100 includes an inner ring 101, an outer ring 102, a plurality of tapered rollers 103, and an annular cage 104. The tapered rollers 103 are interposed between the inner and outer rings 101, 102 in a rollable manner. The cage 104 holds the tapered rollers 103 at regular intervals in the circumferential direction. A large end face 103a of each tapered roller 103 is formed as a convex surface and a cone back face rib (hereinafter referred to as a large rib) end face 101a of the inner ring 101 is formed as a concave surface, and thus sliding friction between the end faces 103a, 101a is reduced (see, e.g., Japanese Utility Model Application Publication No. H05-75520 (JP H05-75520 U))
In this tapered roller bearing, no clear guidelines are given regarding specific values of the respective curvature radii of the large end face 103a of the tapered roller 103 and the large rib end face 101a of the inner ring 101. Therefore, the large end face 103a of each tapered roller 103 may contact an edge of the large rib end face 101a of the inner ring 101 in the radial direction depending on the curvature radii of the end faces 103a, 101a, causing an edge load.