Grinding apparatus and method of controlling grinding apparatus

• US 20090042479A1
• Filed: 08/05/2008
• Published: 02/12/2009
• Est. Priority Date: 08/07/2007
• Status: Abandoned Application

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Inventors: Kubo, Atsushi, Kameno, Hironori, Ishigami, Takayuki
• Application Number:
  US12/222,218
• Publication Number:
  US 20090042479A1
• Time in Patent Office: Days
• US Class Current: 451/5
• CPC Class Codes: B24B 41/044 Grinding spindles with magnetic or electromagnetic bearings; Features related thereto electric motors with magnetic bearings H02K7/09
• CPC Class Codes: B24B 49/00 Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation B24B33/06, B24B37/005 take precedence; if applicable to other machine tools, B23Q15/00 - B23Q17/00 take precedence

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.

Claims

1. A grinding apparatus comprising:

a casing movable relative to a workpiece to be ground;

a grinding wheel spindle disposed in the casing;

a axial active magnetic bearing that axially supports the grinding wheel spindle relative to the casing in a noncontact manner;

a radial active magnetic bearing that radially supports the grinding wheel spindle relative to the casing in a noncontact manner;

an electric motor that rotates the grinding wheel spindle; and

a grinding wheel that includes a grinding surface, for grinding the workpiece, formed on an outer peripheral surface thereof and is attached to the grinding wheel spindle,

wherein the casing is first positioned axially and is then positioned radially to grind the workpiece,

wherein before the casing moves radially and the grinding wheel comes in contact with the workpiece, a stiffness value of the radial magnetic bearing is set to an initialization value lower than a value at a usual grinding time, and

wherein 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.

2. The grinding apparatus according to claim 1, wherein the grinding surface of the grinding wheel is a center-high grinding surface and a part of the workpiece to be ground is a groove formed on a cylindrical peripheral surface of the workpiece.

3. A grinding apparatus comprising:

a casing movable relative to a workpiece to be ground;

a grinding wheel spindle disposed in the casing;

a axial active magnetic bearing that axially supports the grinding wheel spindle relative to the casing in a noncontact manner;

a radial active magnetic bearing that radially supports the grinding wheel spindle relative to the casing in a noncontact manner;

an electric motor that rotates the grinding wheel spindle;

a grinding wheel that includes a grinding surface, for grinding the workpiece, formed on an outer peripheral surface thereof and is attached to the grinding wheel spindle; and

a radial magnetic bearing controller that includes an integration operation section for integrating radial displacement of the grinding wheel spindle using an integration constant and controls the radial magnetic bearing, wherein when integration output of the integration operation section is smaller than a predetermined reference value, the radial magnetic bearing controller sets the integration constant of the integration operation section to an initialization value lower than the value at the usual grinding time and when the integration output exceeds the reference value, the radial magnetic bearing controller increases the integration constant in response to the integration output,

wherein the casing is first positioned axially and is then positioned radially to grind the workpiece.

4. The grinding apparatus according to claim 3, wherein the grinding surface of the grinding wheel is a center-high grinding surface and a part of the workpiece to be ground is a groove formed on a cylindrical peripheral surface of the workpiece.

5. A method of controlling a grinding apparatus which comprises:

a casing movable relative to a workpiece to be ground;

a grinding wheel spindle disposed in the casing;

a axial active magnetic bearing that axially supports the grinding wheel spindle relative to the casing in a noncontact manner;

a radial active magnetic bearing that radially supports the grinding wheel spindle relative to the casing in a noncontact manner;

an electric motor that rotates the grinding wheel spindle; and

a grinding wheel that includes a grinding surface, for grinding the workpiece, formed on an outer peripheral surface thereof and is attached to the grinding wheel spindle, the method comprising;

axially positioning the casing;

setting a stiffness value of the radial magnetic bearing to an initialization value lower than a value at a usual grinding time before the grinding wheel comes in contact with the workpiece;

radially positioning the casing so that the grinding surface of the grinding wheel comes in contact with the workpiece; and

setting the stiffness value of the radial magnetic bearings to a value higher than the initialization value for grinding the workpiece after the grinding surface of the grinding wheel comes in contact with the workpiece.

6. A method of controlling a grinding apparatus which comprises:

a casing movable relative to a workpiece to be ground;

a grinding wheel spindle disposed in the casing;

a axial active magnetic bearing that axially supports the grinding wheel spindle relative to the casing in a noncontact manner;

a radial active magnetic bearing that radially supports the grinding wheel spindle relative to the casing in a noncontact manner;

an electric motor that rotates the grinding wheel spindle;

a grinding wheel that includes a grinding surface, for grinding the workpiece, formed on an outer peripheral surface thereof and is attached to the grinding wheel spindle; and

a radial magnetic bearing controller that includes an integration operation section for integrating radial displacement of the grinding wheel spindle using an integration constant and controls the radial magnetic bearing, the method comprising;

setting the integration constant of the integration operation section to an initialization value lower than the value at the usual grinding time when integration output of the integration operation section is smaller than a predetermined reference value;

increasing the integration constant in response to the integration output when the integration output exceeds the reference value;

axially positioning the casing; and

radially positioning the casing to grind the workpiece.