Rolling bearing and power transmission device including rolling bearing

1. A rolling bearing comprising:

an inner ring;

an outer ring coaxially disposed around an outer peripheral surface of the inner ring with an annular space between the inner ring and the outer ring;

a plurality of rolling elements rollably disposed in the annular space;

a cage that retains the rolling elements; and

a bubble generating mechanism that generates bubbles in liquid lubricant during bearing rotation, wherein the liquid lubricant flows through the annular space.

2. The rolling bearing according to claim 1 , wherein

the bubble generating mechanism is a bearing-ring bubble generating mechanism provided in a rotation-side bearing ring that rotates during the bearing rotation, the rotation-side bearing ring being either one of the inner ring and the outer ring.

3. The rolling bearing according to claim 2 , wherein:

the rolling elements are rollers; and

the bearing-ring bubble generating mechanism is constituted by multiple recessed portions formed on at least one of a peripheral surface of a rib portion of the rotation-side bearing ring and an axial end face of the rotation-side bearing ring, the rib portion facing end faces of the rollers.

4. The rolling bearing according to claim 3 , wherein:

the rollers are tapered rollers; and

the rib portion includes at least one of a small rib portion formed in the rotation-side bearing ring so as to face small-diameter end faces of the tapered rollers, and a large rib portion formed in the rotation-side bearing ring so as to face large-diameter end faces of the tapered rollers.

5. The rolling bearing according to claim 3 , wherein:

the multiple recessed portions constituting the bearing-ring bubble generating mechanism decrease a pressure of the lubricant in the recessed portions so that the pressure of the lubricant in the recessed portions is equal to or lower than a dissolution limit pressure during the bearing rotation.

6. The rolling bearing according to claim 3 , wherein:

the multiple recessed portions constituting the bearing-ring bubble generating mechanism decrease a pressure of the lubricant in the recessed portions so that the pressure of the lubricant in the recessed portions is equal to or lower than a saturation vapor pressure at which the lubricant is changed from a liquid phase to a vapor phase during the bearing rotation.

7. The rolling bearing according to claim 1 , wherein:

the bubble generating mechanism is a cage bubble generating mechanism provided in the cage.

8. The rolling bearing according to claim 7 , wherein:

the cage bubble generating mechanism is constituted by multiple recessed portions formed on an axial end face of the cage.

9. The rolling bearing according to claim 8 , wherein:

the multiple recessed portions constituting the cage bubble generating mechanism decrease a pressure of the lubricant in the recessed portions so that the pressure of the lubricant in the recessed portions is equal to or lower than a dissolution limit pressure during the bearing rotation.

10. The rolling bearing according to claim 8 , wherein:

the multiple recessed portions constituting the cage bubble generating mechanism decrease a pressure of the lubricant in the recessed portions so that the pressure of the lubricant in the recessed portions is equal to or lower than a saturation vapor pressure at which the lubricant is changed from a liquid phase to a vapor phase during the bearing rotation.

11. The rolling bearing according to claim 7 , wherein:

the rolling elements are tapered rollers;

a flange portion extending inwardly in a radial direction is formed in a small-diameter annular portion of the cage; and

the cage bubble generating mechanism is constituted by multiple recessed portions formed on an axial end face of the flange portion.

12. A power transmission device comprising:

the rolling bearing according to claim 1 , wherein

the rolling bearing is provided inside the power transmission device so as to rotatably support a rotary shaft.