Hydrodynamic bearing arrangement for an electric motor

The invention relates to a hydrodynamic bearing arrangement for an electric motor, particularly for a spindle motor to drive the platters of a hard disk drive. The bearing arrangement comprises a shaft, a bearing bush and a thrust plate disposed fixedly on the shaft, the shaft and the thrust plate rotating with respect to the bearing bush, grooved patterns to generate fluid-dynamic pressure being provided on the thrust plate and/or the surfaces located opposite the thrust plate of the bearing sleeve and/or the cover plate. The grooved pattern comprises a number g of grooves distributed over the surface of the bearing sleeve, the thrust plate or the cover plate, wherein in the shaft and/or in the thrust plate, a number h of holes and/or recesses are provided at the inner edge of the thrust plate and/or at the outer edge of the shaft. According to the invention, the number g of grooves cannot be integrally divided by the number h of holes and likewise that h cannot be integrally divided by g.