Bearing cage and manufacturing method therefor

A manufacturing method of a bearing cage, the method comprising:

• forming the bearing cage by injecting melted resin from a resin injection gate, which is provided at a peripheral edge part of a substantially circular ring-shaped cavity formed in an injection mold, into the substantially circular ring-shaped cavity,
• wherein the bearing cage includes:
• a substantially circular ring-shaped base part,
• a plurality of pillar parts spaced with predetermined intervals in a circumferential direction and protruding axially from one axial end side surface of the base part, the plurality of pillar parts including at least a first pillar part and a second pillar part, and
• pockets whose number is equal to a number of the pillar parts formed by facing surfaces of a pair of the pillar parts adjacent to each other and one axial end side surface of the base part,
• wherein the resin injection gate is disposed at the first pillar part,
• wherein when the bearing cage is divided into first and second regions by an imaginary line connecting the resin injection gate and a weld line to be formed at a position radially facing the resin injection gate, a resin reservoir that can store therein the melted resin is formed at the second pillar part in only one of the regions,
• wherein a circumferential distance between the resin reservoir and the weld line is smaller than a circumferential distance between the resin reservoir and the resin injection gate,
• wherein a cross-sectional area of a communicating part of the resin reservoir, which is configured to communicate with the second pillar part, is equal to or less than a quarter of a cross-sectional area of the resin injection gate,
• wherein the resin reservoir is provided at the second pillar part where a thickness in a radial direction, of the second pillar part, is a largest thickness, in the radial direction, of the second pillar part, and
• wherein the radial direction is a direction from a radial center of the bearing cage to the second pillar part.