Patent ID: 8257210

Claim:
A rotation urging mechanism comprising: an outer member which includes an outer raceway surface on an inner periphery thereof and is rotatable about a first axis; an inner member which includes, on an outer periphery thereof, an inner raceway surface disposed in face-to-face relation to a radially inner side of the outer raceway surface over an entire circumference thereof and is rotatable about the first axis; and a plurality of balls disposed rollably between the outer raceway surface and the inner raceway surface, wherein the outer raceway surface is formed about a second axis which is inclined with respect to the first axis, and the inner raceway surface is formed about a third axis which is inclined with respect to the first axis, wherein cages, for respectively maintaining intervals between adjacent ones of the balls, are respectively provided between the adjacent ones of the plurality of balls, wherein the cages are separated from each other in a circumferential direction, and wherein the inner raceway surface comprises a concave shape and the outer raceway surface comprises a concave shape such that, as the plurality of balls move in an axial direction of the first axis, a relative rotation between the outer raceway surface and the inner raceway surface is restricted such that the inner member and the outer member rotate integrally.