US Patent 7748954 Centrifugal fan

A centrifugal fan includes a space in which the dimension between a shroud-facing wall and a shroud, from the outer peripheral side to the inner peripheral side of the shroud, is substantially uniform, wherein the shroud-facing wall includes a recess extending in the circumferential direction, the recess being disposed at the inner peripheral side of the outer peripheral end of the shroud-facing wall forming the space having the uniform dimension so that the recess forms a space larger than the other part.