In the tapered roller bearing, at least any one of an outer ring, an inner ring, and a plurality of tapered rollers includes a nitrogen enriched layer. An oil retaining hole is provided in a larger annular portion of a cage. A value of a ratio R/R.sub.BASE is not smaller than 0.75 and not greater than 0.87 where R represents a set radius of curvature of a larger end face of the tapered roller and R.sub.BASE represents a distance from a point which is an apex of a cone angle of the tapered roller to a larger flange surface of the inner ring. A ratio R.sub.process/R is than not lower 0.5 where R.sub.process represents an actual radius of curvature after grinding of the larger end face of the tapered roller and R represents a set radius of curvature.

A value of R/R.sub.BASE is not smaller than 0.75 and not greater than 0.87 where R represents a reference radius of curvature of a larger end face of a roller and R.sub.BASE represents a distance from an apex of a cone angle of the roller to a larger flange surface of an inner ring 13. A distance from an outermost surface of at least any one of an outer ring, the inner ring, and a plurality of rollers to a bottom of a nitrogen enriched layer is not shorter than 0.2 mm. A crowning profile is formed on a rolling surface of the roller.

A tiltrotor aircraft may be provided and may include a mast assembly, in which the mast assembly may include a mast; a bearing system; a housing; and a housing cap secured to the housing, wherein the bearing system is between the mast and the housing. The bearing system may further include a first bearing assembly including a first inner race, a first outer race, and a plurality of first tapered roller bearings; a second bearing assembly including a second inner race, a second outer race, and a plurality of second tapered roller bearings; an inner spacer and an outer spacer in which the inner and outer spacers are between the first and second bearing assemblies; and a retaining device in which the retaining device and the housing cap provide, at least in part, pre-loading for the first and second bearing assemblies.

An inner ring unit includes an inner ring, a plurality of tapered rollers, and a cage having an annular shape. The cage includes a plurality of cage bars. The cage includes a stopper portion that is provided to protrude from an axial intermediate portion of the cage bar in the circumferential direction of the cage and configured to hinder the tapered rollers from falling off toward a radially outer side by bringing an axial intermediate portion on an outer peripheral surface of each tapered roller housed in a pocket into contact with the stopper portion. The axial intermediate portion on the outer peripheral surface of the tapered roller is a portion that is disposed on a one axial side and on the radially outer side of the tapered roller with respect to the center of gravity of the tapered roller.

A cage for a tapered roller bearing is provided which includes a large-diameter-side annular portion circumferentially extending along the large end surfaces of a plurality of tapered rollers; a small-diameter-side annular portion circumferentially extending along the small end surfaces of the tapered rollers; and a plurality of pillars coupling together the large-diameter-side annular portion and the small-diameter-side annular portion. The large-diameter-side annular portion has large-diameter-side pocket surfaces opposed to the large end surfaces of the respective tapered rollers. The large-diameter-side pocket surfaces include oil retaining holes in the form of blind holes. Lubricating oil is introduced into the oil retaining holes and retained therein by capillary action.

A rolling bearing cage includes at least one cage side ring and a plurality of cage bars extending from the cage side ring so as to form a plurality of pockets, each pocket being defined between a separate pair of adjacent bars, for receiving rolling bodies of the rolling bearing. A cage breakage detection unit includes at least one conductive track and a module for wireless cage breakage monitoring. The cage has at least one recess, in which at least a prefabricated part of the cage breakage detection unit is inserted and fixed.

A cage and roller assembly includes a plurality of rollers to be brought into rolling contact with a raceway surface provided on the outer periphery of a shaft, and an annular cage that retains the rollers. Lubricating oil is supplied through an oil supply hole that is provided inside the shaft and is open at the raceway surface. The cage includes a pair of annular portions, and a plurality of cage bars that couple the annular portions together and are arranged with intervals in a circumferential direction. The rollers are housed in pockets each formed between the pair of annular portions and between the cage bars that are adjacent to each other in the circumferential direction. The cage has an inner recessed groove that is provided on a radially inner surface of the cage bar and extends through the annular portions in an axial direction.

A cage and roller assembly includes a plurality of rollers to be brought into rolling contact with a raceway surface provided on the outer periphery of a shaft, and an annular cage that retains the rollers. Lubricating oil is supplied through an oil supply hole that is provided inside the shaft and is open at the raceway surface. The cage includes a pair of annular portions, and a plurality of cage bars that couple the annular portions together and are arranged with intervals in a circumferential direction. The rollers are housed in pockets each formed between the pair of annular portions and between the cage bars that are adjacent to each other in the circumferential direction. The cage has an inner recessed groove that is provided on a radially inner surface of the cage bar and extends through the annular portions in an axial direction.

A rolling bearing is mounted on a gear shaft, which extends along an axis and carries a first and a second toothing axially separated from each other by a cylindrical portion of the gear shaft. Such a cylindrical portion has an outer diameter smaller than that of the first toothing. The bearing is provided with rolling bodies, a cage with seats engageable by the rolling bodies, and an outer ring defining an outer rolling path for the rolling bodies. During assembly, the cage is fitted around the first toothing and axially displaced towards the second toothing until it is arranged around the cylindrical portion. In this step, the tenons of the cage pass in the slots between the teeth of the first toothing. Subsequently, the rolling bodies are radially inserted in the respective seats so as to be arranged against the cylindrical portion.

Two projecting portions (45a and 45b) configured to guide a tapered roller (3) on distal end surfaces thereof are formed on a side surface (43a) of a pillar portion (43) of a retainer (4) so as to be separated apart from each other in a roller axis direction. The projecting portions (45a and 45b) are separated apart from each other in the roller axis direction with respect to both a small-diameter-side annular portion (41) and a large-diameter-side annular portion (42). The projecting portions (45a and 45b) each have a force-fit margin (F).