Rolling bearing unit

A rolling bearing unit comprising:

• an inner race supporting a rotary shaft;
• an outer race fixed to a housing, the inner race and the outer race defining a bearing space therebetween, the bearing space having an opening at one axial end thereof;
• rolling elements disposed in the bearing space;
• and
• a seal member attached to one axial end of the outer race at the one axial end of the bearing space so as to cover the opening of the bearing space, wherein the bearing space defines a circulation path for lubricating oil, the circulation path having an outlet at a position where there is the seal member,
• the seal member including, either:
• (i) a circular annular support frame having a plurality of window holes, and a filter having a predetermined mesh size, the filter being fixedly joined to the support frame, or the support frame and the filter are formed by integral molding such that the window holes are closed by the filter, wherein the support frame has an inner diameter determined such that a passage through which lubricating oil can pass is defined between the support frame and a radially outer surface of the inner race, and wherein the filter includes a protruding portion protruding radially inwardly beyond a radially inner surface of the support frame such that a radially inner edge of the protruding portion is in contact with the inner race, or such that the protruding portion surrounds the radially outer surface of the inner race through a gap defined therebetween and smaller than the mesh size of the filter;
• or
• (ii) a support frame having no window holes and having a large number of holes, each of a size equivalent to the mesh size of the filter, at locations where the window holes are to be provided, the seal member being free of the filter.