Abstract: A radial ball bearing has a pair of bearing rings each of which has at least one raceway groove with a certain radius of curvature in an axial direction and a shoulder of the raceway groove. The raceway groove of one of the bearing rings is opposed to the raceway groove of the other bearing ring, and a plurality of balls are rotatably provided between the opposite raceway grooves of the bearing rings. Each of the bearing rings has a curved portion with a radius of curvature in the axial direction which is equal to or greater than that of the raceway groove between the raceway groove and the shoulder of the raceway groove. The curved portion extends from a point within an ellipse of contact produced at the bearing ring by a predetermined axial load and is smoothly continuous from the raceway groove, the point making an inflection point between the raceway groove and the curved portion.

Abstract: A radial roller bearing consisting of rings and rollers, either the rolling contact surface of each roller or the raceway surfaces of the rings or both are crowned, the amount of crowning which is defined as .DELTA.t/l i.e., the depth of crowning .DELTA.t to the effective roller length of l, is set to 0.0007 to 0.002, the ring has a rib at its one end, the end surface of each roller which makes contact with the rib is spherically convex, while the contacted surface of the rib is spherically concave.

Abstract: A bearing, having an inner ring, an outer ring, rolling members, inner seal members, outer seal members, a first grease having good heat resistance which is contained inward of the inner seal member, and a second grease having water-resistance and corrosion-prevention which is contained between the inner seal member and the outer seal member. The second grease prevents rusting in the outer and inner rings even if water enters the inner side of the outer seal member. The first grease assures satisfactory lubrication of the rolling members, the outer and inner rings under high speed and high temperature conditions.