Hydrodynamic bearing assembly

Abstract

This invention provides a hydrodynamic bearing assembly which realizes a high rotation rate in a stable manner with robust rigidity. The hydrodynamic bearing assembly has a total radial gap of 3 microns or less for preventing contact with the thrust bearing. The thrust bearing is a pump-out type, and the radial bearing has offset grooves on the surface thereof to supply fluid flow to the thrust bearing. A depth ratio of the grooves relative to the diameter of the shaft is preferably 0.005 or less to avoid reduced translational rigidity.

1 - 45 . (canceled) 
   
   
       46 . A hydrodynamic bearing assembly, comprising:
 a radial bearing; and   a pair of thrust bearings provided on both ends of said radial bearing along an axis of the bearing assembly, each thrust bearing communicating in fluid with said radial bearing, and at least one of said thrust bearings being a pump-out type thrust bearing for conducting the fluid in the direction from the axis to a circumference thereof.   
   
   
       47 . A hydrodynamic bearing assembly, comprising:
 a column shaft having a pair of small columns concentrically formed on end surfaces;   a hollow cylindrical sleeve rotatably arranged around an outer surface of said shaft parallel to the axis of the shaft; and   a pair of donut-shaped thrust plates arranged on both ends of said sleeve, each of said thrust plate including a through-hole, through which the small column extends;   a radial bearing defined between the outer surface of said shaft and the inner surface of said sleeve; and   a thrust bearing defined between the pair of thrust plates and thrust opposing surfaces opposing to the thrust plates;   wherein each thrust bearing communicating in fluid with said radial bearing, and grooves are formed on either one of said thrust plate and thrust opposing surface to generate a thrust dynamic pressure due to a relative rotation between said thrust plate and thrust opposing surface, and   wherein the grooves of at least one of said thrust bearings being a pump-out type groove for conducting the fluid in the direction from the axis to a circumference thereof.   
   
   
       48 . A hydrodynamic bearing assembly, comprising:
 a column shaft having a small column concentrically formed on one end surfaces along an axis;   a hollow cylindrical sleeve rotatably arranged around an outer surface of said shaft parallel to the axis of the shaft; and   a first donut-shaped thrust plate arranged on one end of said sleeve, including a through-hole, through which the small column extends;   a second disk-shaped thrust plate arranged on the other end of said sleeve for covering thereof,   a radial bearing defined between the outer surface of said shaft and the inner surface of said sleeve; and   a first thrust bearing defined between said first thrust plate and a first thrust opposing surface opposing to said first thrust plates, the first thrust opposing surface having the trough-hole;   a second thrust bearing defined between said second thrust plate and a second thrust opposing surface opposing to said second thrust plates, the second thrust opposing surface having no trough-hole;   said radial bearing connects with said first and second thrust bearings;   a plurality of pump-out type grooves formed on either one of said first thrust plate and the first thrust opposing surface, for conducting the fluid in a direction from the axis to a circumference of said first thrust bearing so as to generate a pump-out type thrust dynamic pressure due to a relative rotation between said: first thrust plate and the first thrust opposing surface;   a plurality of pump-in type grooves formed on either one of said second thrust plate and the second thrust opposing surface, for conducting the fluid in a direction from a circumference of said second thrust bearing to the axis so as to generate a pump-in type thrust dynamic pressure due to a relative rotation between said second thrust plate and the second thrust opposing surface.   
   
   
       49 . The hydrodynamic bearing assembly according to  claim 46 , further comprising:
 a groove formed on the outer surface of said shaft and the inner surface of said sleeve for promoting the fluid flow between said both thrust bearings.   
   
   
       50 . The hydrodynamic bearing assembly according to  claim 49 ,
 wherein said groove is a groove parallel or offset to the axis, or a herringbone groove.   
   
   
       51 . The hydrodynamic bearing assembly according to  claim 50 ,
 wherein, if one of said thrust bearing is the pump-out type one and the other one of said thrust bearing is the pump-in type, the offset or herringbone groove is formed such that the fluid in the radial bearing is directed from said pump-out type thrust bearing to said pump-in type thrust bearing due to a relative rotation between the outer surface of said shaft and the inner surface of said sleeve.   
   
   
       52 . The hydrodynamic bearing assembly according to  claim 51 ,
 wherein a central angle of the off groove defined the line from the center of the axis to start point of the off groove and the line from the center of the axis to end point of the off groove is within the range of 10 to 120 degrees.   
   
   
       53 . The hydrodynamic bearing assembly according to  claim 47 ,
 wherein said shaft includes,   a first conduit extending parallel to the axis from at least one end of said shaft or small column to a middle portion thereof,   at least one second conduit extending substantially perpendicular to the axis from the outer surface of said shaft to the first conduit, and   said radial bearing communicates in fluid to the atmosphere through the first and second conduits.   
   
   
       54 . The hydrodynamic bearing assembly according to  claim 47 ,
 wherein said shaft is a stationary member and said sleeve is a rotational member rotating around said shaft.   
   
   
       55 . A hydrodynamic bearing assembly comprising:
 a radial bearing including a hollow cylindrical shaft having an outer surface parallel to an axis, a hollow cylindrical sleeve having an inner surface rotatably arranged around the outer surface of said shaft, said radial bearing for generating a radial dynamic pressure due to a relative rotation between said sleeve and said shaft; and   a thrust bearing including a disk-shaped thrust plate secured perpendicularly onto one end of the axis of said shaft the thrust plate having a through-hole formed concentrically to the axis, and a thrust opposing surface of one end surface of said sleeve, opposing to said thrust plate, said thrust bearing for generating a thrust dynamic pressure due to the relative rotation between said thrust plate and said thrust opposing surface;   a constraint member closely fit within the inner surface of a hollow space of said shaft for securing said shaft thereto; and   a fastening member having means for engaging with said constraint member;   wherein the engaging means extends through the through-hole of the thrust plate to engage with the constraint member so that said shaft and said sleeve are secured.   
   
   
       56 . The hydrodynamic bearing assembly according to  claim 47 , further comprising:
 a groove formed on the outer surface of said shaft and the inner surface of said sleeve for promoting the fluid flow between said both thrust bearings.   
   
   
       57 . The hydrodynamic bearing assembly according to  claim 56 ,
 wherein said groove is a groove parallel or offset to the axis, or a herringbone groove.   
   
   
       58 . The hydrodynamic bearing assembly according to  claim 57 ,
 wherein, if one of said thrust bearing is the pump-out type one and the other one of said thrust bearing is the pump-in type, the offset or herringbone groove is formed such that the fluid in the radial bearing is directed from said pump-out type thrust bearing to said pump-in type thrust bearing due to a relative rotation between the outer surface of said shaft and the inner surface of said sleeve.   
   
   
       59 . The hydrodynamic bearing assembly according to  claim 58 ,
 wherein a central angle of the off groove defined the line from the center of the axis to start point of the off groove and the line from the center of the axis to end point of the off groove is within the range of 10 to 120 degrees.   
   
   
       60 . The hydrodynamic bearing assembly according to  claim 48 , further comprising:
 a groove formed on the outer surface of said shaft and the inner surface of said sleeve for promoting the fluid flow between said both thrust bearings.   
   
   
       61 . The hydrodynamic bearing assembly according to Chum  60 ,
 wherein said groove is a groove parallel or offset to the axis, or a herringbone groove.   
   
   
       62 . The hydrodynamic bearing assembly according to  claim 61 ,
 wherein, if one of said thrust bearing is the pump-out type one and the other one of said thrust bearing is the pump-in type, the offset or herringbone groove is formed such that the fluid in the radial bearing is directed from said pump-out type thrust bearing to said pump-in type thrust bearing due to a relative rotation between the outer surface of said shaft and the inner surface of said sleeve.   
   
   
       63 . The hydrodynamic bearing assembly according to  claim 62 ,
 wherein a central angle of the off groove defined the line from the center of the axis to start point of the off groove and the line from the center of the axis to end point of the off groove is within the range of 10 to 120 degrees.   
   
   
       64 . The hydrodynamic bearing assembly according to  claim 48 ,
 wherein said shaft includes,   a first conduit extending parallel to the axis from at least one end of said shaft or small column to a middle portion thereof,   at least one second conduit extending substantially perpendicular to the axis from the outer surface of said shaft to the first conduit, and   said radial bearing communicates in fluid to the atmosphere through the first and second conduits.   
   
   
       65 . The hydrodynamic bearing assembly according to  claim 48 ,
 wherein said shaft is a stationary member and said sleeve is a rotational member rotating around said shaft.   
   
   
       66 . A hydrodynamic bearing assembly comprising:
 a column shaft having an outer surface parallel to an axis;   a hollow cylindrical sleeve having an inner surface rotatably arranged around the outer surface of said shaft; and   a radial bearing for generating a radial dynamic pressure due to a relative rotation between said sleeve and said shaft to keep them away from each other, wherein   either one of the outer surface of said shaft and the inner surface of said sleeve has a plurality of scratched notches extending in parallel to the axis, and   each scratched notch is formed on the surface having the plurality of scratched notches with an interval of an arc of at most 200 microns to another notch, each notch has a depth within the range of approximately 1 micron to approximately 20 microns and a width within the range of approximately 200 microns to approximately 500 microns.