A tapered roller bearing includes an inner ring having a tapered raceway surface and a large-collar surface on a large-diameter side of the raceway surface, and tapered rollers. Each of the rollers has a large end surface guided by the large-collar surface. When R represents a set curvature radius of the large end surface and R.sub.BASE represents a base curvature radius from a vertex of a cone angle of each of the tapered rollers to the large-collar surface, the base curvature radius R.sub.BASE is 100 mm or less, and a ratio R/R.sub.BASE of the set curvature radius R to the base curvature radius R.sub.BASE is set to 0.90 or less. When R.sub.ACTUAL represents an actual curvature radius of the large end surface of each of the tapered rollers, a ratio R.sub.ACTUAL/R of the actual curvature radius R.sub.ACTUAL to the set curvature radius R exceeds 0.5.

The contact portion of the end face of a conical roller, which is a portion to be slidingly contacted with a collar portion, is ground such that the outer contour line of the section thereof has a continuously curved line which passes through at least not only the first point but also between the third position and fourth position.

A motion guide apparatus which can prevent the motion guide apparatus from rattling when being used in an environment Where an excessive moment works thereon. A crowning is formed at an end of a loaded rolling element rolling surface of a movable member, and a chamfer is formed at an end of the crowning. Let a total length of the crowning and the chamfer in a length direction of the loaded rolling element rolling surface be L. Let the diameter of a ball be Da. L/Da>4 is set. A maximum depth D of the chamfer is set to equal to or greater than the elastic deformation amount of a rolling element rolling surface of a track member, the loaded rolling element rolling surface of the movable member, and the rolling element under a radial load equal to or greater than 60% of the basic dynamic load rating.

A roller bearing includes an inner race ring, an outer race ring, and a roller arranged between and in contact with the inner and outer rings. The bearing has a flange (31,131) on the inner race ring at one axial end, and a flange (21,121) on the outer race ring at an opposite axial end. One of the flanges, and/or an end of the roller, includes at least one principal segment (53,153) intermediate two additional segments (52,152; 54,154). The principle segment is tangentially blended with the two additional segments, and the principle segment has a first curvature that is different from the respective curvatures of the two additional segments. A non-elliptical contact footprint can be obtained by composite profiles at the contact location between the roller end and the mating flange face.

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 ring for use in a roller bearing includes an outer wall. The ring further includes two side walls extending away from the outer wall, defining a cavity therebetween for receiving at least one roller, and each of the two side walls having an outer edge at a location facing the cavity and farthest from the outer wall. The ring further includes a curved crown extending inward from at least one of the two side walls and configured to contact the at least one roller to reduce wear of the outer edge.

A roller bearing includes an inner race ring, an outer race ring, and a roller arranged between and in contact with the inner and outer rings. The bearing has a flange (31,131) on the inner race ring at one axial end, and a flange (21,121) on the outer race ring at an opposite axial end. One of the flanges, and/or an end of the roller, includes at least one principal segment (53,153) intermediate two additional segments (52,152; 54,154). The principle segment is tangentially blended with the two additional segments, and the principle segment has a first curvature that is different from the respective curvatures of the two additional segments. A non-elliptical contact footprint can be obtained by composite profiles at the contact location between the roller end and the mating flange face.

A ring for use in a roller bearing includes an outer wall. The ring further includes two side walls extending away from the outer wall, defining a cavity therebetween for receiving at least one roller, and each of the two side walls having an outer edge at a location facing the cavity and farthest from the outer wall. The ring further includes a curved crown extending inward from at least one of the two side walls and configured to contact the at least one roller to reduce wear of the outer edge.

In a tapered roller bearing, a cage includes a plurality of trapezoidal pockets and the pockets accommodate and hold a plurality of rollers. A notch having a width is provided in a post on a smaller width side of the pocket of the cage from a boundary between a smaller annular portion and a post toward a larger annular portion. Lubricating oil which flows from an inner diameter side of the cage toward an inner ring is quickly discharged through the notch toward an outer ring on an outer diameter side. A distance from an outermost surface of at least any one of the outer ring and the inner ring of the roller and a plurality of rollers to a bottom of a nitrogen enriched layer is equal to or longer than 0.2 mm. A rolling surface of the roller is provided with a logarithmic crowning profile.