Grinding apparatus and method of controlling grinding apparatus

Abstract

A grinding wheel formed on an outer peripheral surface with a grinding surface is attached to a grinding wheel spindle supported by axial active magnetic bearings and radial active magnetic bearings in a noncontact manner axially and radially and rotated by an electric motor. A casing is axially positioned and then is radially moved and a ground part of a workpiece is ground. Before the casing moves radially and the grinding wheel comes in contact with the workpiece, the stiffness value of the radial magnetic bearings is set to an initialization value lower than a value at the usual grinding time and after the grinding surface of the grinding wheel comes in contact with the workpiece, the stiffness value of the radial magnetic bearings is set to a value higher than the initialization value for grinding the workpiece.

Description

BACKGROUND OF THE INVENTION[0001]This invention relates to a grinding wheel for grinding a workpiece on a grinding surface of the outer peripheral surface of the grinding wheel attached to a grinding wheel spindle and in particular to a grinding apparatus adapted to grind a groove formed on a cylindrical peripheral surface of a workpiece, such as a raceway groove formed on the inner peripheral surface of an outer ring of a ball bearing, for example, using a grinding wheel formed on the outer peripheral surface with a center-high grinding surface, and relates to a method of controlling the grinding apparatus.[0002]An internal cylindrical grinding machine is known as a grinding apparatus for performing finishing grinding of a raceway groove formed on the inner peripheral surface of an inner ring of a ball bearing or the inner peripheral surface of an outer ring.[0003]In a usual internal cylindrical grinding machine, a grinding wheel formed on the outer peripheral surface with a grindi...

AI Technical Summary

Benefits of technology

The invention is a grinding apparatus that reduces the impact force and wear of the grinding wheel when the axial and radial magnetic bearings are not perfectly aligned. The apparatus includes a casing and a grinding wheel spindle, with an axial active magnetic bearing and a radial active magnetic bearing that support the spindle in a noncontact manner. The stiffness value of the radial magnetic bearing is set to an initialization value lower than the usual grinding time when the grinding wheel comes in contact with the workpiece. The apparatus also includes a radial magnetic bearing controller that adjusts the stiffness value of the bearings based on the excitation current of the magnets. This allows for a soft landing of the grinding wheel when it comes in contact with the workpiece, reducing the impact force and wear.

Problems solved by technology

At this time, if the axial position of the groove formed on the inner peripheral surface of the workpiece in the preceding step does not involve any error, an impact force only acts; however, if an error occurs and the axial position of the groove deviates axially from the correct position, not only an impact force, but also so-called grinding wheel wear of extreme wearing (or chip) of a part of the grinding surface of the grinding wheel occurs and the grinding wheel life is shortened.

In addition to finishing grinding of the raceway groove on the inner peripheral surface of the outer ring, to grind a groove formed on the cylindrical peripheral surface (inner peripheral surface or outer peripheral surface) of the workpiece, a similar problem is involved.

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