Liquid bearing assembly and method of constructing same
A bearing assembly is disclosed that includes a sleeve having an opening formed therein and a shaft positioned within the opening of the sleeve such that a gap is formed between an inner surface of the sleeve and an outer surface of the shaft. A lubricant is disposed in the gap and a plurality of grooves are formed on at least one of the outer surface of the shaft and the inner surface of the sleeve. An anti-wetting coating is disposed on the at least one of the outer surface of the shaft and the inner surface of the sleeve between adjacent grooves of the plurality of grooves.
1. A bearing comprising:
a sleeve having an opening formed therein;
a shaft positioned within the opening of the sleeve such that a gap is formed between an inner surface of the sleeve and an outer surface of the shaft;
a lubricant disposed in the gap;
a plurality of grooves formed on at least one of the outer surface of the shaft and the inner surface of the sleeve; and
an anti-wetting coating disposed on the at least one of the outer surface of the shaft and the inner surface of the sleeve between adjacent grooves of the plurality of grooves.
2. The bearing of claim 1 wherein the plurality of grooves comprise at least one of a herringbone geometry and a spiral geometry.
3. The bearing of claim 1 wherein the plurality of grooves are non-symmetrical across an axial length of the self-acting bearing.
4. The bearing of claim 1 wherein the plurality of grooves are formed on at least one of a thrust bearing surface and a radial bearing surface of the self-acting bearing.
5. The bearing of claim 1 wherein the anti-wetting coating comprises a refractory metal.
6. The bearing of claim 1 wherein the anti-wetting coating comprises a ceramic.
7. The bearing of claim 1 wherein the anti-wetting coating comprises one of Titanium Nitride, Titanium Oxide, and Titanium Oxynitride.
8. The bearing of claim 1 wherein the lubricant comprises Gallium.
9. The bearing of claim 1 wherein the lubricant comprises a liquid metal.
10. The bearing of claim 1 wherein the anti-wetting coating is applied to bearing surfaces of at least one of the outer surface of the shaft and the inner surface of the sleeve; and
wherein the plurality of grooves comprise non-bearing surfaces of the at least one of the outer surface of the shaft and the inner surface of the sleeve.
11. The bearing of claim 1 wherein the plurality of grooves are wetting.
12. The bearing of claim 1 wherein a depth of the plurality of grooves is approximately equal to a thickness of the anti-wetting coating.
13. The bearing of claim 1 wherein the plurality of grooves are formed in a non-circumferential pattern.
14. A method of manufacturing a bearing comprising the steps of:
providing a bearing assembly, the bearing assembly comprising:
a shaft; and
a sleeve having an inner diameter greater than an outer diameter of the shaft, wherein a gap is formed between an inner surface of the bearing sleeve and an outer surface of the shaft;
forming an anti-wetting coating on at least one of the outer surface of the shaft and the inner surface of the sleeve;
forming a plurality of grooves on at least one of the outer surface of the shaft and the inner surface of the sleeve, wherein the plurality of grooves are absent the anti-wetting coating, and wherein the plurality of grooves and the anti-wetting coating are formed on a common surface of the bearing assembly; and
disposing a lubricant in the gap.
15. The method of claim 14 further comprising forming the plurality of grooves in at least one of a herringbone pattern and a spiral pattern.
16. The method of claim 14 further comprising patterning the anti-wetting coating on the common surface of the bearing assembly to define a plurality of anti-wetting portions and a plurality of wetting portions on the common surface.
17. The method of claim 14 wherein forming the anti-wetting coating comprises coating the at least one of the outer surface of the shaft and the inner surface of the sleeve with a material that exhibits anti-wetting properties when exposed to the lubricant.
18. The method of claim 14 further comprising forming the plurality of grooves in a non-circumferential pattern.
19. An x-ray tube comprising:
a cathode; and
a target assembly positioned to receive electrons emitted from the cathode, the target assembly comprising:
a target; and
a self-lubricating bearing configured to support the target, the self-lubricating bearing comprising:
a rotatable component having a first surface;
a stationary component positioned with respect to the rotatable component such that a gap is formed between a first surface of the rotatable component and a first surface of the stationary component; and
a liquid lubricant disposed within the gap; and
wherein a bearing surface of the self-lubricating bearing comprises an anti-wetting surface; and
wherein a non-bearing surface of the self-lubricating bearing comprises a wetting surface; and
wherein the anti-wetting surface and the wetting surface are alternately located on a common surface of the self-lubricating bearing, the common surface comprising at least one of a thrust bearing surface and a radial bearing surface of the self-lubricating bearing.
20. The x-ray tube of claim 19 wherein the stationary component comprises a center shaft and the rotatable component comprises a sleeve, the sleeve having the target attached thereto.
21. The x-ray tube of claim 19 wherein the bearing surface comprises an anti-wetting coating formed on at least one of the first surface of the rotatable component and the first surface of the stationary component.
22. The x-ray tube of claim 21 wherein the anti-wetting coating comprises at least one of Titanium, a ceramic, a refractory metal, an oxide of a base metal of the self-lubricating bearing.
23. The x-ray tube of claim 19 wherein the non-bearing surface comprises a pattern of grooves formed on at least one of the first surface of the rotatable component and the first surface of the stationary component.
24. A bearing comprising:
at least one friction-reducing surface comprising a plurality of alternating anti-wetting and wetting portions, wherein the wetting portions of the at least one friction-reducing surface have one of a helical spiral and a herringbone geometry.
25. The bearing of claim 24 further comprising a first friction-reducing surface a rotating component of the bearing; and
a second friction-reducing surface on a stationary component of the bearing.
26. The bearing of claim 24 wherein the anti-wetting portions of the at least one friction-reducing surface comprise bearing surfaces; and
wherein the wetting portions of the at least one friction-reducing surface comprise non-bearing surfaces.
27. The bearing of claim 24 wherein the wetting portions of the at least one friction-reducing surface comprise grooves formed in the at least one friction reducing surface.
28. The bearing of claim 24 wherein the anti-wetting portions of the at least one friction-reducing surface comprises at least one of Titanium, a ceramic, a refractory metal, and an oxide of a base metal of the bearing.