Single thrust bearing fluid dynamic bearing motor

Abstract

A typical dynamic bearing design comprises a ring shaped or circular thrust plate mounted at or near the end of a shaft, the shaft defining together with a surrounding sleeve a journal bearing by providing grooves on only one of the two surfaces facing the gap between the shaft and sleeve. On the ring shaped thrust plate supported by the shaft, the traditional upward thrust bearing defined between the lower face of the thrust plate and the facing surface of the sleeve is maintained; but no grooves are on the surface of the thrust plate distant from the shaft and a facing counterplate surface. Further, the journal bearing is defined to have an asymmetry so that a bias force pressure along the surface of the shaft toward the thrust plate is established. The combination of the journal groove asymmetry pumping action toward the shoulder or thrust plate, together with the single grooved thrust bearing, is sufficient to establish a constant pressure between the distal surface of the thrust plate and the facing counterplate, as well as between the groove thrust plate and the facing shoulder surface.

What is claimed is:  
     
         1 . A fluid dynamic bearing arrangement comprising a sleeve defining a bore and further defining a thrust surface extending transversely to the bore, 
 a shaft supported in the bore the shaft and bore together defining a fluid dynamic journal bearing which supports rotation of the shaft and the sleeve relative to one another,    a thrust plate extending transversely from the shaft and having first and second axially directed surfaces, the first thrust surface and the sleeve thrust surface defining together a first fluid dynamic thrust bearing, and    an ungrooved counterplate mounted to the journal sleeve and defining together with the second axially directed surface of the thrust plate a gap which is in fluid communication with the first thrust bearing and the fluid dynamic journal bearing.    
     
     
         2 . A fluid dynamic bearing arrangement as claimed in  claim 1  including an asymmetric journal bearing defined between the shaft and the sleeve establishing an asymmetric pressure directed toward the first thrust bearing.  
     
     
         3 . A fluid dynamic bearing arrangement as claimed in  claim 1  wherein the asymmetric journal bearing includes a grooved surface on one of the journal sleeve or the shaft.  
     
     
         4 . A fluid dynamic bearing arrangement as claimed in  claim 2  wherein the grooved pattern on the thrust plate surface is a balanced groove pattern, with the thrust apex diameter being slightly displaced toward the distal edge of the thrust plate from the shaft.  
     
     
         5 . A fluid dynamic bearing arrangement according to  claim 3  wherein the thrust bearing pattern is chosen from a group comprising a chevron pattern or an outward spiral.  
     
     
         6 . A fluid dynamic bearing arrangement as claimed in  claim 5  further comprising a circulation path extending from the second thrust bearing gap to the journal bearing.  
     
     
         7 . A fluid dynamic bearing arrangement as claimed in  claim 6  wherein the circulation path comprises a groove extending axially through the thrust plate.  
     
     
         8 . A fluid dynamic bearing arrangement as claimed in  claim 2  wherein the journal bearing comprises first and second groove patterns along the gap between the shaft and the sleeve, the second section being more distant from the thrust plate than the first section and being modified relative to the first section to create the journal asymmetric pumping action toward the thrust plate along the shaft.  
     
     
         9 . A fluid dynamic bearing arrangement as claimed in  claim 2  wherein the journal bearing groove asymmetry pumping action is sufficient to create a journal asymmetry pressure against the second thrust plate surface toward an end of the shaft to support the distancing of the counterplate from the second thrust plate surface.  
     
     
         10 . A fluid dynamic bearing arrangement as claimed in  claim 2  wherein the journal bearing creates asymmetry pumping pressure sufficient to act as a constant force to axially bias the spacing of the thrust plate relative to the sleeve thrust surface and counterplate surface such that the first thrust plate grooved surface gap with the translate sleeve surface closes until axial force equilibrium is achieved.  
     
     
         11 . A fluid dynamic bearing arrangement as claimed in  claim 8  wherein in operation the gap between the thrust plate second surface and the counterplate is substantially larger than the gap between the first thrust plate groove surface and the sleeve transverse surface.  
     
     
         12 . A fluid dynamic bearing arrangement comprising a sleeve defining a bore and further defining a thrust surface extending transversely to the bore, 
 a shaft supported in the bore the shaft and bore together defining a journal bearing means for supporting rotation of the shaft and the sleeve relative to one another,    a thrust plate extending transversely from the shaft and having first and second axially directed surfaces, and thrust bearing means comprising the first thrust surface and the sleeve thrust surface for axially supporting relative rotation of the shaft and the sleeve.    
     
     
         13 . A fluid dynamic bearing arrangement as claimed in  claim 12  wherein one of the first thrust surface and the sleeve thrust surface comprises a groove pattern to establish the thrust bearing means.  
     
     
         14 . A fluid dynamic bearing arrangement as claimed in  claim 13  wherein the journal bearing means comprises an asymmetric journal bearing defined between the shaft and the sleeve establishing an asymmetric pressure directed toward the first thrust bearing.  
     
     
         15 . A fluid dynamic bearing arrangement as claimed in  claim 14  further comprising an ungrooved counterplate mounted to the journal sleeve and defining together with the second axially directed surface of the thrust plate a gap which is in fluid communication with the first thrust bearing and the fluid dynamic journal bearing.  
     
     
         16 . A fluid dynamic bearing arrangement as claimed in  claim 5  further comprising a circulation path extending from the second thrust bearing gap to the journal bearing.  
     
     
         17 . A fluid dynamic bearing arrangement as claimed in  claim 6  wherein the circulation path comprises a groove extending axially through the thrust plate.  
     
     
         18 . A disc drive comprising a housing, a spindle motor supported from the housing and supporting one or more discs for rotation, the spindle motor including a fluid dynamic bearing arrangement comprising a sleeve defining a bore and further defining a thrust surface extending transversely to the bore, 
 a shaft supported in the bore the shaft and bore together defining a fluid dynamic journal bearing which supports rotation of the shaft and the sleeve relative to one another,    a thrust plate extending transversely from the shaft and having first and second axially directed surfaces, the first thrust surface and the sleeve thrust surface defining together a first fluid dynamic thrust bearing, and    an ungrooved counterplate mounted to the journal sleeve and defining together with the second axially directed surface of the thrust plate a gap which is in fluid communication with the first thrust bearing and the fluid dynamic journal bearing.    
     
     
         19 . A disc drive as claimed in  claim 18  including an asymmetric journal bearing defined between the shaft and the sleeve establishing an asymmetric pressure directed toward the first thrust bearing.  
     
     
         20 . A disc drive as claimed in  claim 19  wherein the journal bearing groove asymmetry pumping action is sufficient to create a journal asymmetry pressure against the second thrust plate surface toward an end of the shaft to support the distancing of the counterplate from the second thrust plate surface.