Tapered roller bearing and manufacturing method for retainer of tapered roller bearing

A tapered roller bearing, comprising:

• an outer ring having a partial tapered concave shaped outer raceway formed around an inner circumferential surface thereof;
• an inner ring that is placed on an inner-diameter side of the outer ring so as to be concentric with the outer ring, and has a partial tapered convex inner raceway formed around an outer circumferential surface thereof, and a large-diameter side flange section that protrudes outward in the radial direction from an end section on the large-diameter side of the inner raceway;
• a plurality of tapered rollers that are placed between the inner raceway and the outer raceway so as to be able to roll freely and such that an end surface on the large-diameter side of the rollers face a side surface in the axial direction of the large-diameter side flange section;
• and
• a retainer for holding the tapered rollers;
• the retainer comprising:
• a large-diameter side rim section and a small-diameter side rim section that are ring shaped and that are placed concentric with each other about a center axis and spaced apart in the axial direction, and a plurality of column sections that span between both of the rim sections such that portions that are surrounded by both rim sections and a pair of column sections that are adjacent to each other in the circumferential direction form pockets for holding the tapered rollers;
• and
• an oil retaining concave section that is recessed outward in the radial direction are formed in a portion of the inner circumferential surface of the large-diameter side rim section which coincides with at least part of the pockets in the circumferential direction, so as to be independent from each other, a portion of the bottom surface of each of the oil retaining concave section that is the deepest with respect to the inner circumferential surface of the large-diameter side run section being open toward each if the pockets,
• the deepest portion of the bottom surface of each of the oil retaining concave sections that is open to an inner surface of each of the pockets faces toward the end surface on the large-diameter side of the tapered roller that is held inside the pocket,
• a cross-sectional shape of each of the oil retaining concave sections in a plane perpendicular to a center axis of the retainer is a circular arc shape,
• a curvature radius of the cross-sectional circular arc shape of the bottom surface of each of the oil retaining concave sections is less than a curvature radius of the inner circumferential surface of the large-diameter side rim section, and
• the inner circumferential surface of the large-diameter side rim section, is a cylindrical shape surface that is parallel with the center axis if the retainer, or is an inclined surface that inclines in a direction outward in the radial direction going toward the pocket side with respect to the center axis of the retainer.