A strain wave gearing has a wave generator provided with a plug and a roller bearing. The roller bearing is provided with flange plates fixed to both sides of the plug, and outer circumferential edge portions of the flange plates protrude outwardly from a plug outer circumferential surface so as to locate on both sides, in an axial line direction, of the raceway of rollers. The movements of the rollers in the axial line direction are constrained by the outer circumferential edge portions. The movement of retainer in the axial line direction is constrained by engaging with the rollers. The movement of each component part of the roller bearing in the axial line direction can be constrained without using additional components.

A bearing ring for a rolling-element bearing includes a rolling-element raceway that is axially delimited by a guide flange and a retaining flange. At least the retaining flange is configured as a separate element that is fixedly connectable to the bearing ring, and the bearing ring includes a substantially radially extending stop that is offset inward from an axial end of the bearing towards the raceway.

A cylindrical roller bearing includes a flanged outer race having two inwardly extending flanges. One of the flanges is a flange ring separate from the outer race and fixed to the outer race. Cylindrical rollers are mounted between the outer race and a flangeless inner race, and retained by a retainer which are located radially inwardly of the pitch circle of the cylindrical rollers. With this arrangement, it is not necessary to reduce the widths of pillars of the retainer even if the load capacity is increased by increasing the size or the number of the cylindrical rollers, so that it is possible to increase the load capacity while ensuring strength of the retainer. Also, even if the inner race is separated from the bearing, it is possible to prevent separation of the cylindrical rollers as well as the retainer, which retains the cylindrical rollers, from the outer race.

An inner ring has a rib face as a concave surface that is formed on the larger diameter side of an inner ring and that contacts large end faces of tapered rollers. A tapered roller bearing satisfies Ri>RRr, where Rr represents a curvature radius of the large end face, Ri represents a curvature radius of the rib face 8 in a longitudinal section of the inner ring 2, R represents a distance from a cone center to a reference point. The distance R is the distance from the cone center to the reference point, where the reference point is the intersection of the rib face and an imaginary line extending from the cone center and along an inner ring raceway surface in the longitudinal section of the inner ring 2. Surface roughness of the rib face is greater than that of the large end face.

A cylindrical roller bearing includes a flanged outer race having two inwardly extending flanges. One of the flanges is a flange ring separate from the outer race and fixed to the outer race. Cylindrical rollers are mounted between the outer race and a flangeless inner race, and retained by a retainer which are located radially inwardly of the pitch circle of the cylindrical rollers. With this arrangement, it is not necessary to reduce the widths of pillars of the retainer even if the load capacity is increased by increasing the size or the number of the cylindrical rollers, so that it is possible to increase the load capacity while ensuring strength of the retainer. Also, even if the inner race is separated from the bearing, it is possible to prevent separation of the cylindrical rollers as well as the retainer, which retains the cylindrical rollers, from the outer race.

A bearing ring for a roller bearing includes a raceway configured to support at least one rolling-element roller and a flange at an end of the raceway extending away from the raceway and having an abutment surface for guiding the at least one rolling-element roller on the raceway. The abutment surface has a curvature that decreases monotonically from a starting point on the abutment surface to an end of the abutment surface, and the abutment surface includes at least one strongly monotonically decreasing segment.

A low friction tapered roller bearing is provided that implements either needle rollers, nested needle rollers, nested balls, or a thrust washer between the tapered rollers and the large rib of the inner ring. The nested needle rollers and balls options can either be cage guided or full complement.