Fluid dynamic bearing system

Abstract

Fluid dynamic bearing systems produced by specified methods are provided. In one example, a method for designing a fluid dynamic bearing system includes determining a first stability ratio for a first journal bearing configuration. The method further includes determining a second stability ratio for a second journal bearing configuration. In a further example system, the first configuration has two sub-journal bearings and the second configuration has three sub-journal bearings. The method may comprise comparing the two stability ratios to determine whether adding a sub-journal increases the stability ratio of the bearing system.

1 . A fluid dynamic bearing system, comprising:
 a gap region between an inner member and an outer member;   an optimal journal bearing configuration, including at least three sub-journal bearings, disposed along the gap region, wherein the optimal configuration is determined by a method, including the steps of:   determining a first stability ratio for a first journal bearing configuration;
 determining a second stability ratio for a second journal bearing configuration; 
 comparing the two stability ratios; and 
 determining that the second stability ratio is greater than the first stability ratio. 
   
   
   
       2 . The system of  claim 1 , wherein the first configuration comprises two sub-journal bearings and the second configuration comprises three sub-journal bearings. 
   
   
       3 . The system of  claim 2 , wherein each sub-journal bearing of the first configuration has a length equal to substantially one-half of a total journal length and each sub-journal bearing of the second journal configuration has a length equal to substantially one-third of the total journal length. 
   
   
       4 . The system of  claim 1 , wherein the method further comprises the steps of: determining a third stability ratio of a third journal bearing configuration; and comparing the third stability ratio to the second stability ratio. 
   
   
       5 . The system of  claim 4 , wherein the first configuration comprises two sub-journal bearings, the second configuration comprises three sub-journal bearings, and the third configuration comprises four sub-journal bearings. 
   
   
       6 . The system of  claim 5 , wherein each sub-journal bearing of the first configuration has a length equal to substantially one-half of a total journal length, each sub-journal bearing of the second journal configuration has a length equal to substantially one-third of the total journal length, and each sub-journal bearing of the third journal configuration has a length equal to substantially one-fourth of the total journal length. 
   
   
       7 . The system of  claim 1 , wherein the first configuration comprises N number of sub-journals and the second configuration comprises (N+1) number of sub-journals. 
   
   
       8 . The system of  claim 7 , wherein the method further comprises the steps of: determining a third stability ratio of a third journal bearing configuration, the third configuration comprising (N+2) number of sub-journals; and comparing the third stability ratio to the second stability ratio. 
   
   
       9 . A fluid dynamic bearing system, comprising:
 a first gap region between an inner member and an outer member; and   at least three sub-journal bearings disposed along the first gap region, the at least three sub-journal bearings associated with a first stability ratio, the first stability ratio greater than a second stability ratio associated with having only two sub-journal bearings disposed along the first gap region of the fluid dynamic bearing system.   
   
   
       10 . The system of  claim 9 , further comprising a hub coupled to the outer member and configured to rotate relative to the inner member. 
   
   
       11 . The system of  claim 9 , further comprising a hub coupled to the inner member and configured to rotate relative to the outer member. 
   
   
       12 . A fluid dynamic bearing system, comprising:
 a gap region between an inner member and an outer member;   a journal bearing disposed along the gap region, wherein a configuration of the journal bearing is determined by steps of:
 determining a first stability ratio for a first journal bearing configuration having at least two sub-journal bearing; 
 determining a second stability ratio for a second journal bearing configuration having at least three sub-journal bearings, wherein each of the at least three sub-journal bearings provides radial stiffness; and 
 implementing the second journal bearing configuration to improve the second stability ratio relative to the first stability ratio. 
   
   
   
       13 . The system of  claim 12 , wherein each sub-journal bearing of the first configuration has a length equal to substantially one-half of a total journal length and each sub-journal bearing of the second journal configuration has a length equal to substantially one-third of the total journal length. 
   
   
       14 . The system of  claim 12 , further including a third journal bearing configuration. 
   
   
       15 . The system of  claim 14 , further including the step of determining a third stability ratio of the third journal bearing. 
   
   
       16 . The system of  claim 14 , wherein the first journal bearing configuration comprises two sub-journal bearings, the second journal bearing configuration comprises three sub-journal bearings, and the third journal bearing configuration comprises four sub-journal bearings. 
   
   
       17 . The system of  claim 16 , wherein each sub-journal bearing of the first journal bearing configuration has a length equal to substantially one-half of a total journal length, each sub-journal bearing of the second journal bearing configuration has a length equal to substantially one-third of the total journal length, and each sub-journal bearing of the third journal bearing configuration has a length equal to substantially one-fourth of the total journal length. 
   
   
       18 . The system of  claim 12 , wherein the first journal bearing configuration comprises 2+N number of sub-journal bearings and the second journal bearing configuration comprises 3+N number of sub journal bearings. 
   
   
       19 . The system of  claim 18 , further including a third journal bearing configuration comprising 4+N number of sub journal bearings. 
   
   
       20 . The system of  claim 1 , wherein the second stability ratio is greater than the first stability ratio.