Patent ID: 8882359

Claim:
A wheel rolling bearing unit comprising: an inner ring member including a flange on one end, a wheel being mountable to the flange; an outer ring member disposed concentrically on an outer peripheral side of the inner ring member so that an annular space is formed between the inner ring member and the outer ring member, the annular space including openings at opposed ends; a plurality of rolling elements arranged in double rows and disposed between the inner ring member and the outer ring member; a pair of cage segments disposed circumferentially within the annular space along the double rows of the plurality of rolling elements to retain the rolling elements in a circumferential direction; sealing members configured to hermetically seal the openings at the opposed ends of the annular space, grease for lubricating the respective members having been introduced into the annular space; and a concave section and a convex section provided on an inner peripheral surface of each of the cage segments, the concave section forming a dent oriented toward an outside of the wheel rolling bearing unit in a radial direction to hold the grease, wherein the dent is formed from an outside end section to an inside end section in an axial direction, and the convex section of each of the cage segments extends radially from the dent and the convex sections are adjacent to each other.