Disk drive spindle with fluid journal bearing having increased radial clearance in axial end regions
View Patent ↗A method to fabricate a fluid bearing spindle includes creating a hollow cylindrical bore through a solid workpiece. The hollow cylindrical bore has a journal bearing portion including first and second distal tapered bearing segments separated by a central bearing segment having a constant radius. Each of the first and second distal tapered bearing segments has a tapered bearing radius that increases with distance from the central bearing segment to a maximum tapered bearing radius that is in the range of 0.5 microns to 1.5 microns greater than the constant radius. Subsequently, a cylindrical spindle shaft is inserted into the hollow cylindrical bore. In an alternative embodiment, a cylindrical outer surface of the spindle shaft includes the tapered bearing segments, rather than the hollow cylindrical bore.
1. A method to fabricate a fluid bearing spindle, the method comprising:
creating a hollow cylindrical bore through a solid workpiece, the hollow cylindrical bore defining a spindle axis of rotation and being concentric about the spindle axis of rotation, the hollow cylindrical bore having a journal bearing portion including:
first and second distal tapered bearing segments, and
a central bearing segment disposed axially adjacent to and between the first and second distal tapered bearing segments,
wherein the central bearing segment has a constant radius along a central bearing segment axial extent, and each of the first and second distal tapered bearing segments has a tapered bearing segment axial extent and a tapered bearing radius that increases with distance from the central bearing segment along the tapered bearing segment axial extent to a maximum tapered bearing radius that is in a range of 0.5 microns to 1.5 microns greater than the constant radius, the tapered bearing segment axial extent being in a range of 0.7 mm to 1.3 mm, and
subsequently inserting a cylindrical spindle shaft into the hollow cylindrical bore.
2. The method of claim 1 , further comprising creating a pattern of grooves in the journal bearing portion of the hollow cylindrical bore.
3. The method of claim 2 , wherein the pattern of grooves extends into the first and second distal tapered bearing segments, and the central bearing segment.
4. The method of claim 3 , wherein the pattern of grooves is a herringbone pattern of chevron shaped grooves.
5. The method of claim 4 , wherein a first plurality of the chevron shaped grooves each define an apex that is axially coincident with where the first distal tapered bearing segment meets the axially adjacent central bearing segment.
6. The method of claim 2 , wherein the radial tool clearance is greater than 20 microns.
7. The method of claim 2 , wherein passing the electrical current is continued until the pattern of grooves defines a groove depth in the range of 2 microns to 7 microns.
8. The method of claim 1 , wherein a radial bearing clearance between an outer bearing surface of the cylindrical spindle shaft and the journal bearing portion of the hollow cylindrical bore is no greater than 5 microns.
9. The method of claim 8 , further comprising completely filling the radial bearing clearance with a bearing lubricant.