Bearing assemblies and apparatuses including superhard bearing elements

1. A radial bearing assembly, comprising:

an inner support ring circumferentially surrounding a central bearing axis;

a plurality of superhard bearing elements coupled to the inner support ring, each of the plurality of superhard bearing elements comprising:

a base;

a superhard bearing surface comprising a partial-spherical surface shape oriented outwardly from the central bearing axis;

a side surface centered about a central element axis, the side surface and the central element axis extending between the base and the superhard bearing surface;

wherein:

the superhard bearing surfaces of the plurality of superhard bearing elements collectively substantially conform to a common spherical reference surface;

the central element axes of the plurality of superhard bearing elements are oriented substantially perpendicular to the central bearing axis.

2. The bearing assembly of claim 1 , wherein the superhard bearing surface has a radius of curvature that is substantially centered about the central bearing axis.

3. The bearing assembly of claim 1 , wherein the superhard bearing surface comprises a convex surface oriented outwardly from the central bearing axis.

4. The bearing assembly of claim 1 , wherein each of the plurality of superhard bearing elements is fixed within a respective bearing-element recess defined within the inner support ring.

5. The bearing assembly of claim 1 , wherein each of the plurality of superhard bearing elements comprises a polycrystalline diamond table bonded to a substrate, the polycrystalline diamond table comprising the superhard bearing surface.

6. A bearing apparatus, comprising:

an inner bearing assembly comprising:

an inner support ring circumferentially surrounding an inner ring axis;

a first plurality of superhard bearing elements coupled to the inner support ring, each of the first plurality of superhard bearing elements having a side surface centered about a central element axis, the side surface and the central element axis extending between a base and a superhard bearing surface, the superhard bearing surface comprising a partial-spherical surface shape oriented outwardly from the inner ring axis, wherein:

the superhard bearing surfaces of the first plurality of superhard bearing elements collectively substantially conform to a common spherical reference surface;

the central element axes of the first plurality of superhard bearing elements are oriented substantially perpendicular to the inner ring axis;

an outer bearing assembly comprising

an outer support ring circumferentially surrounding an outer ring axis;

a second plurality of superhard bearing elements coupled to the outer support ring, each of the second plurality of superhard bearing elements having a side surface extending between a base and a superhard bearing surface, the superhard bearing surface of each of the second plurality of superhard bearing elements contacting a superhard bearing surface of at least an opposing one of the first plurality of superhard bearing elements.

7. The bearing apparatus of claim 6 , wherein the superhard bearing surface of each of the second plurality of superhard bearing elements comprises an arcuate surface.

8. The bearing apparatus of claim 6 , wherein:

the superhard bearing surface of each of the first plurality of superhard bearing elements comprises a convex surface;

the superhard bearing surface of each of the second plurality of superhard bearing elements comprises a concave surface.

9. The bearing apparatus of claim 6 , wherein the superhard bearing surface of each of the second plurality of superhard bearing elements comprises a flat surface.

10. The bearing apparatus of claim 6 , wherein the inner bearing assembly is rotatable relative to the outer bearing assembly when the inner ring axis is oriented at an angle from the outer ring axis.

11. The bearing assembly of claim 6 , wherein each of the first plurality of superhard bearing elements and each of the second plurality of superhard bearing elements comprises a polycrystalline diamond table bonded to a substrate, the polycrystalline diamond table comprising the superhard bearing surface.

12. The bearing apparatus of claim 6 , wherein:

the inner bearing assembly is configured as one of a rotor and a stator;

the outer bearing assembly is configured as the other of the rotor and the stator.

13. A subterranean drilling system, comprising:

an output shaft operable to apply torque to a rotary drill tool, the output shaft operably coupled to a bearing apparatus, the bearing apparatus comprising:

an inner bearing assembly comprising:

an inner support ring circumferentially surrounding an inner ring axis;

a first plurality of superhard bearing elements coupled to the inner support ring, each of the first plurality of superhard bearing elements having a side surface centered about a central element axis, the side surface and the central element axis extending between a base and a superhard bearing surface, the superhard bearing surface comprising a partial-spherical surface shape oriented outwardly from the inner ring axis, wherein:

the superhard bearing surfaces of the first plurality of superhard bearing elements collectively substantially conform to a common spherical reference surface;

the central element axes of the first plurality of superhard bearing elements are oriented substantially perpendicular to the inner ring axis;

an outer bearing assembly comprising

an outer support ring;

a second plurality of superhard bearing elements coupled to the outer support ring, each of the second plurality of superhard bearing elements having a side surface extending between a base and a superhard bearing surface, the superhard bearing surface of each of the second plurality of superhard bearing elements contacting a superhard bearing surface of at least an adjacent one of the first plurality of superhard bearing element.