Patent ID: 7666062

Claim:
A grinding apparatus for grinding a workpiece, comprising: a casing relatively movable with respect to the workpiece; a wheel spindle that is contactlessly supported with respect to the casing; a controlled type axial magnetic bearing provided at the casing for contactlessly supporting the wheel spindle in an axial direction thereof; a controlled type radial magnetic bearing provided at the casing for contactlessly supporting the wheel spindle in a radial direction thereof; an electric motor that rotates the wheel spindle; and a grinding wheel which is disposed on the wheel spindle and includes a convex grinding surface for grinding a groove formed on a cylindrical peripheral surface of the workpiece, wherein after the casing is axially positioned with respect to the workpiece, the grinding wheel grinds the workpiece while the casing is radially moved with respect to the workpiece, wherein before the casing is put into contact with the workpiece when the casing is radially moved toward the workpiece, a stiffness value of the axial magnetic bearing is set to be lower than a normal value, and wherein when it is detected that the grinding surface of the grinding wheel touches the entire groove of the workpiece and the entire surface of the workpiece is started to be ground, the stiffness value of the axial magnetic bearing is set to the normal value.