In recent years, with the performance improvement of OA · AV equipment, the bearing have been required to have high rotation accuracy and quietness. But there are increasing number of areas where this required characteristics can not be satisfied by the rolling bearing, which is mainly used, replacement to the fluid dynamic bearing has been paid attention.
NTN has developed hydrodynamic bearing using technology of the sintered bearing. We adopt sintered oil-impregnated bearings as material, and take mass production of the Hydrodynamic BEARPHITE with herringbone type dynamic pressure grooves in the inner surface.
Examples of use : Spindle motor for HDD, Polygon scanner motor, Cooling fan motor.

• High rotational accuracy
  High rotational accuracy can be obtained because the shaft is held by an oil film over the entire circumference due to the dynamic pressure effect.
• Excellent quietness
  The shaft is held by oil film, and noise due to metal contact is not caused.
• High reliability
  Has long life because lubricating oil exists inside the bearing and the amount of oil retained is large.

Fig.1 Measurement result of NRRO and Current

Fig.2 Measurement result of oil film formation rate