To suppress the thermal damage and improve the durability by specifying the inner and outer rings groove curvature radiuses in a protecting bearing in a magnetic bearing device.
A full type bearing consisting of an outer ring 1, an inner ring 2 and a ball 3 is used as the touch-down rolling bearing for a magnetic bearing device of a type in which a rotor makes contact with the inner surface of the inner ring or the outer surface of the outer ring 1. The outer ring 1 is constituted so that the outer ring groove curvature radius is 0.70>fe>0.58 when the curvature radius of an outer ring groove 1a is fe, and the inner ring 2 is constituted so that the inner ring groove curvature radius is 0.50<fi<0.53 when the curvature radius of an inner ring groove 2a is fi. In the drawing, Da designates the diameter of the ball 3. Since no spin is caused between the inner ring 2 and the ball 2 even under high speed rotation by setting the curvature radiuses in such a manner, a so-called inner ring control can be performed. When the outer ring groove curvature radius Fe is larger than 0.7, the surface pressure on the outer ring side is increased to cause a problem in life, and when the inner ring groove curvature radius fi is smaller than 0.50, aground is caused.
OURA YUKIO
UEDA KIYOTOSHI
