US Patent 7441957 Fluid dynamic bearing

A fluid dynamic bearing assembly includes a bearing sleeve (30) having an inner surface and a rotary shaft (30) rotatably received in the bearing sleeve. The rotary shaft has an outer surface. One of the inner surface of the bearing sleeve and the outer surface of the rotary shaft forms a dynamic pressure generating groove pattern (10). The groove pattern includes a plurality of grooves (12) extending from a center area toward one edge of the groove pattern. Each of the grooves has at least one of a depth and a width decreasing from the center area toward the edge.