A fluid dynamic bearing system having pressure-generating asymmetric
surface patterns, having at least two bearing parts that are rotatable
with respect to each other and form a bearing gap filled with a bearing
fluid between associated bearing surfaces. The surface patterns are
disposed on at least one bearing surface so that hydrodynamic pressure is
generated within the bearing gap when the bearing parts rotate with
respect to each other. Each surface pattern comprises at least three
sections, each section generating a pumping action in a defined
direction, and the pumping actions of adjacent sections being
substantially aligned in opposite directions. Due to the special geometry
of the surface patterns, tolerances in the geometry of the bearing gap
have a less significant effect on the pre-defined pumping direction.