GRINDING MACHINE AND GRINDING METHOD

• US 20090258576A1
• Filed: 04/09/2009
• Published: 10/15/2009
• Est. Priority Date: 04/11/2008
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Inventors: Kobayashi, Yuuta, Mizutani, Yoshihiro, Morita, Hiroshi
• Granted Patent: US 8,172,644 B2
• Time in Patent Office: Days
• US Class Current: 451/53
• CPC Class Codes: B24B 19/12 for grinding cams or camshafts
• CPC Class Codes: B24B 5/42 for grinding crankshafts or crankpins
• CPC Class Codes: B24D 5/06 with inserted abrasive blocks, e.g. segmental
• CPC Class Codes: B24D 5/10 with cooling provisions, e.g. with radial slots

Abstract

A grinding machine is provided with first and second grinding wheels selectively used in dependence on the steps of machining operations. The second grinding wheel is grooved so that at least one oblique groove vertically crosses a contact surface on which a grinding surface of the second grinding wheel contacts with a workpiece, and thus, is capable of releasing a dynamic pressure in coolant generated between the grinding surface and the workpiece since coolant supplied from over the contact surface flows out from both of the upper and lower sides of the contact surface through the at least one oblique groove. Since it does not occur that fluctuations in the dynamic pressure generated in coolant cause the distance between the second grinding wheel and the workpiece to be varied, the accuracy in grinding the workpiece with the second grinding wheel can be enhanced.

Claims

1. A grinding machine having first and second grinding wheels selectively used in dependence on steps of grinding operations for grinding a workpiece with each of the grinding wheels with coolant supplied to a contact surface on a grinding surface of each grinding wheel and the workpiece, wherein:

the first grinding wheel comprises a grinding wheel having a grinding surface formed to be plane; and

the second grinding wheel comprises a grinding wheel having a plurality of oblique grooves formed on a grinding surface thereof to be inclined relative to a wheel circumferential direction.

2. The grinding machine as set forth in claim 1, wherein:

the plurality of oblique grooves are inclined at a predetermined angle relative to the wheel circumferential direction and are formed at equiangular intervals in such an arrangement that where one side intersection point is defined as an intersection point of each oblique groove and an extension line of one side edge parallel to the wheel circumferential direction of the contact surface and the other side intersection point is defined as an intersection point of each oblique groove and an extension line of the other edge, the other side intersection point of each oblique groove overlaps the one side intersection point of an oblique groove next to each such oblique groove by a predetermined overlap amount in the wheel circumferential direction; and

in grinding the workpiece with the second grinding wheel, an infeed amount of the second grinding wheel against the workpiece and at least one of the inclination angle and the intervals of the oblique grooves are set so that the length in the wheel circumferential direction of the contact surface on the grinding surface of the second grinding wheel and the workpiece becomes shorter than the overlap amount.

3. The grinding machine as set forth in claim 1, wherein:

the plurality of oblique grooves are inclined by a predetermined angle relative to the wheel circumferential direction and are formed on the grinding surface at equiangular intervals to open at both sides of the second grinding wheel so that a part of each oblique groove on one side of the second grinding wheel overlaps a part of a circumferentially adjoining oblique groove on the other side of the second grinding wheel by a predetermined overlap amount in the wheel circumferential direction; and

in grinding the workpiece with the second grinding wheel, an infeed amount of the second grinding wheel against the workpiece and at least one of the inclination angle and the intervals of the oblique grooves are set so that the length in the wheel circumferential direction of the contact surface on the grinding surface of the second grinding wheel and the workpiece becomes shorter than the overlap amount.

4. The grinding machine as set forth in claim 1, wherein the sum of widths of adjoining oblique grooves which are within the contact surface on the grinding surface of the second grinding wheel and the workpiece and which exist on a cutting-plane line becomes constant at all times, the cutting-plane line being taken when radially cutting the second grinding wheel at an arbitrary position in the circumferential direction and in parallel to a wheel spindle of the grinding machine.

5. The grinding machine as set forth in claim 1, wherein a mechanism is provided to selectively bring the first and second grinding wheels before the workpiece to use the first grinding wheel in a rough grinding of the workpiece and to use the second grinding wheel in a finish grinding of the workpiece.

6. The grinding machine as set forth in claim 1, wherein a mechanism is provided to selectively bring the first and second grinding wheels before the workpiece to grind a smooth cylindrical surface portion of the workpiece with the first grinding wheel and to grind an uneven cylindrical surface portion of the workpiece with the second grinding wheel.

7. The grinding machine as set forth in claim 1, wherein the first and second grinding wheels are rotatably carried on opposite sides of a wheel head and wherein the mechanism comprises:

a wheel head swivel device for turning the wheel head about an axis perpendicular to a plane including the axis of the workpiece and the axes of the first and second grinding wheels.

8. The grinding machine as set forth in claim 1, wherein the first grinding wheel and the second grinding wheel are arranged in a juxtaposed relation.

9. The grinding machine as set forth in claim 8, wherein the first and second grinding wheels are juxtaposed by fitting and fastening the second grinding wheel on a wheel spindle of the grinding machine and then, by fitting the first grinding wheel on the wheel spindle and fastening the first grinding wheel on the second grinding wheel.

10. The grinding machine as set forth in claim 9, wherein the first and second grinding wheels are juxtaposed on the wheel spindle with a space therebetween in the axial direction of the wheel spindle.

11. The grinding machine as set forth in claim 8, wherein the first and second grinding wheels are arranged in the juxtaposed relation by being attached respectively on respective wheel spindles which are rotatably supported respectively by first and second wheel heads movable independently in the axial direction of the workpiece.

12. The grinding machine as set forth in claim 1, wherein:

at least the grinding surface of the second grinding wheel is formed to be inclined relative to the axis of the second grinding wheel; and

a wheel head rotatably supporting the first and second grinding wheels is constructed as a swivel head which is turnable about an axis extending to be perpendicular to a plane including the axis of the workpiece and the axis of a wheel spindle rotatably supported by the swivel head.

13. A grinding method for grinding a workpiece with each of first and second grinding wheels with coolant supplied to a contact surface on a grinding surface of each grinding wheel and the workpiece, the method comprising the steps of:

forming a grinding surface of the first grinding wheel to be plane;

forming a plurality of oblique grooves on a grinding surface of the second grinding wheel to be inclined relative to a wheel circumferential direction; and

selectively using the first and second grinding wheels in dependence on the steps of grinding operations which are performed in turn on the workpiece.

14. The grinding method as set forth in claim 13, wherein the first grinding wheel is used in a rough grinding of the workpiece, whereas the second grinding wheel is used in a finish grinding of the workpiece.

15. The grinding method as set forth in claim 13, wherein the first grinding wheel is used in grinding a smooth cylindrical surface portion of the workpiece, whereas the second grinding wheel is used in grinding an uneven cylindrical surface portion of the workpiece.