Centerless grinding through the application of a helical twist to axial grooves

Abstract

A cylindrical workpiece with a helical axial groove allowing for centerless grinding which has an angular overlap around the outer circumference on the body of the workpiece. The angular overlap ensures continuous tangential contact with the grinding wheels as the workpiece is rotated.

Claims

1. A workpiece for grinding between two grinding wheels and a platform comprising: a body with an outer circumference having a first end and a second end separated by a length; a continuous helical groove extending from a first end to the second end along the entire length of the body a depth from the outer circumference, the helical groove having a surface the depth from the outer circumference connected to a first side and a second side; wherein the helical groove has an angular overlap along the entire length of the body and around the outer circumference of the body measured between an imaginary line drawn from a first edge of the first side at the first end to the second end and to a second edge of the first side at the second end, the imaginary line remaining confined within the continuous helical groove, such that during grinding between the two grinding wheels and the platform, the angular overlap ensures an unbroken, intact, outer circumference continuous tangential contact with the two grinding wheels and the platform as the workpiece is rotated freely on the platform.

2. The workpiece of claim 1, wherein the workpiece is a sleeve of a control valve.

3. The workpiece of claim 1, wherein the workpiece is a control valve of a variable camshaft timing phaser.

4. The workpiece of claim 1, wherein the workpiece is a lock pin.

5. The workpiece of claim 1, wherein the workpiece is a detent valve.

6. The workpiece of claim 1, wherein the surface of the second axial slot is flat.

7. The workpiece of claim 1, wherein the surface of the second axial slot is curved.

8. The workpiece of claim 1, wherein the grinding is centerless grinding.

9. A workpiece for grinding between two grinding wheels and a platform comprising: a body with an outer circumference having a first end and a second end separated by a length; a continuous helical slot comprising: a first axial slot at a first end extending a length towards the second end having a depth from the outer circumference, the first axial slot having a flat surface at the depth from the outer circumference, the flat surface connected to a first side and a second side; a helical jog having a surface at the depth having first helical jog side and a second helical jog side connected to the first side and the second side of the first axial slot, the helical jog extending a length towards the second end; and a second axial slot having a surface at the depth adjoined to a first side and a second side connected to the first helical jog side and the second helical jog side; wherein the continuous helical slot has an angular overlap around the outer circumference of the body measured between an imaginary line drawn from a first edge of the first side of the first axial slot at the first end with the flat surface to an edge of the second side of the second axial slot of the continuous helical slot, the imaginary line confined to the second side of the first axial slot, the surface of the helical jog, and first side of the second axial slot, covering a portion of the circumferential surface of the workpiece, such that during grinding between the two grinding wheels and the platform, the angular overlap ensures an unbroken, intact, outer circumference continuous tangential contact with the two grinding wheels and the platform as the workpiece is rotated on the platform.

10. The workpiece of claim 9, wherein the workpiece is a sleeve of a control valve.

11. The workpiece of claim 9, wherein the workpiece is a control valve of a variable camshaft timing phaser.

12. The workpiece of claim 9, wherein the workpiece is a lock pin.

13. The workpiece of claim 9, wherein the workpiece is a detent valve.

14. The workpiece of claim 9, wherein the grinding is centerless grinding.

15. The workpiece of claim 9, wherein the workpiece has a single continuous helical slot.

16. The workpiece of claim 9, wherein the continuous helical slot has a length less than the length of the body between the first end and the second end.

17. The workpiece of claim 9, wherein the continuous helical slot has a length equal to the length of the body between the first end and the second end.

18. A method of manufacturing a control sleeve for a variable cam timing phaser comprising the steps of: placing a workpiece on a platform, the workpiece comprising: a body with an outer circumference having a first end and a second end separated by a length; and a continuous helical groove extending from a first end to the second end along the entire length of the body a depth from the outer circumference, the helical groove having a surface the depth from the outer circumference connected to a first side and a second side; wherein the helical groove has an angular overlap along the entire length of the body and around the outer circumference of the body measured between an imaginary line drawn from a first edge of the first side at the first end to the second end and to a second edge of the first side at the second end, the imaginary line remaining confined within the continuous helical groove; feeding the workpiece between two rotary grinding wheels which rotate at the same rotational speed in different directions, but different tangential speeds; grinding the workpiece such that the angular overlap ensures continuous tangential contact with the two rotary grinding wheels as the workpiece is rotated.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 shows a schematic of a conventional workpiece containing an axial slot along an axis.

(2) FIG. 2 shows a schematic of a workpiece of a first embodiment with an uninterrupted helical slot on the outer circumference of the workpiece for centerless grinding.

(3) FIG. 3 shows a schematic of a workpiece of a second embodiment with helical slot with a planar surface on an outer circumference of the workpiece for centerless grinding.

(4) FIG. 4 shows a schematic of another conventional workpiece with a jog on the outer circumference of the workpiece.

(5) FIG. 5a shows a schematic of a centerless grinding layout with a conventional workpiece containing a axial slot.

(6) FIG. 5b shows a close-up of the conventional workpiece containing an axial slot.

(7) FIG. 6a shows a schematic of a centerless grinding layout with a workpiece containing a helical axial slot.

(8) FIG. 6b shows a close-up of the workpiece containing a helical axial slot.

DETAILED DESCRIPTION OF THE INVENTION

(9) FIG. 2 shows a schematic of a workpiece 102 of a first embodiment with an uninterrupted axial helical groove or slot 107 on the outer circumference 102a of the workpiece 102. The axial helical slot 107 extends a length from a first end 102b of the workpiece 102 to the second end 102c. The axial helical slot 107 has a surface 107c and two axial slot sides 109a, 109b which extend from the outer circumference 102a to the surface 107c a depth D. Each of the axial slot sides 109a, 109b each have a first helical slot edge 107a and a second helical slot edge 107b.

(10) By adding a helical slot 107 relative to the outer circumference 102a, helical overlap is present to ensure that contact is consistently maintained between the outer circumference 102a of the workpiece 102 and the grinding wheels 5, 6. The helical overlap is shown in FIG. 2 as distance D1 and represents the angular overlap of the start of the helical slot edge or first helical slot edge 107a at a first end 102b of a first axial slot side 109a when compared to the end of the slot edge or second helical slot edge 107b of the second axial slot side 109b at the opposite, second end 102c.

(11) To measure D1, an imaginary line IL is extended from the first helical slot edge 107a at a first end 102b to the second end 102c, with the distance between the imaginary line IL and the second helical slot edge 107b at the second end 102c being D1 and representative of the helical overlap. The first helical slot edge 107a and the second helical slot edge 107b overlap to allow the grinding wheel to contact continuously around the outer circumference of the workpiece 102.

(12) The helical overlap D1 on the outer circumference 102a of the workpiece 102 is sized such that the workpiece 102 can rotate freely and maintain continuous tangential contact with the grinding wheels 5, 6 and the platform 3, as the grinding wheels 5, 6 consider the outer circumference 102a of the cylindrical workpiece 102 to have no interruptions or to be completely intact as shown in FIGS. 6a-6b. FIG. 6b shows the outside diameter 102a of the workpiece 102 in continuous tangential contact with grinding wheels 5, 6 and platform 3 as the workpiece 102 is ground to size.

(13) A control sleeve or control valve can be manufactured using a workpiece 102 described above. The workpiece 102 is placed on a platform 3. The workpiece 102 is secured between two rotary grinding wheels 5, 6 which rotate at the same speed in different directions; grinding the workpiece 102 such that the angular overlap ensures continuous tangential contact with the two rotary grinding wheels as the workpiece 102 is rotated.

(14) It should be noted that in the prior art FIGS. 5a-5b, the outer circumference 2a of the workpiece 2 is interrupted by the straight axial slot 7 such that the outer straight axial slot 7 causes the workpiece 2 to stop when contact occurs between the outer straight axial slot 7 and either the grinding wheels 5, 6 or the platform 3 and that no sizing of the workpiece 2 can occur.

(15) One advantage of the helical slot 107 of an embodiment of the present invention is that the actual cut path is shorter than separate axial slots 9, 10 and angular jogs 11 as shown in the conventional workpiece 20 of FIG. 4. This enables longer tool life and faster machining times for the machine that cuts the slot. Another advantage is that actual fluid flow distance through the helical slot 107 is shorter and results in less pressure drop across the workpiece 102 than compared to multiple axial slots 9, 10 and angular jogs 11 of a conventional workpiece 20. In yet another advantage, the helical slot 107 could be used as an orientation feature in a mating assembly increasing ease of installation.

(16) FIG. 3 shows a schematic of a workpiece 202 of a second embodiment for centerless grinding. The workpiece 202 has a first end 202b, a second end 202c, and an outer circumference 202a. The outer circumference 202a has a first axial flat slot 207 which is connected to a second axial flat slot 210 ending in a hole 211 through a helical jog 208. While the second axial flat slot 210 is shown as ending in a hole 211, the second axial slot 210 or a connecting slot could extend to end 202c along the outer circumference 202a of the workpiece 202. The first axial flat slot 207 has a flat surface 212 and two axial slot sides 213, 214 which extend a depth d4 from the outer circumference 202a. The helical jog 208 has a surface 219 and two helical jog sides 215, 216 which extend a depth d5 to the surface 219 from the outer circumference 202a. The second axial flat slot 210 has a surface 220 and two axial slot sides 217, 218 which extend a depth d6 to the flat surface 220 from the outer circumference 202a. While the surface 220 is shown is flat in FIG. 3, the surface 220 may also be curved. The axial slot sides 213, 214 are connected to the helical jog sides 215, 216 and the helical jog sides 215, 216 are connected to the axial slot sides 217, 218. The depths d4, d5, d6 of the sides 213, 214, 215, 216, 217, 218 may be the same or different.

(17) The helical jog 208 between the first axial flat slot 207 and the second axial slot 210 has a length L. The helical overlap D2 represents the angular overlap of the first axial flat slot 207 to the second axial flat slot 210. To measure D2, an imaginary line IL is extended from the edge 207a of axial flat slot side 214 at a first end 202b to the second end 202c, with the distance between the imaginary line IL and the edge 210a of the axial flat slot side 218 of the second axial flat slot 210 being the helical overlap.

(18) Due to the helical overlap D2 of the helical jog 208, the grinding wheels 5, 6 and the platform 3 are continuously maintained in contact with the outer circumference 202a of the workpiece 202.

(19) A control sleeve or control valve can be manufactured using a workpiece 202 described above. The workpiece 202 is placed on a platform 3. The workpiece 202 is secured between two rotary grinding wheels 5, 6 which rotate at the same speed in different directions; grinding the workpiece 202 such that the angular overlap ensures continuous tangential contact with the two rotary grinding wheels as the workpiece 202 is rotated.

(20) In an embodiment of the present invention, the workpiece 102 and 202 is a sleeve for a control valve, or a control valve associated with a variable cam timing phaser. In an alternate embodiment, the workpiece 102 and 202 is a lock pin or detent valve for use with a variable cam timing phaser. In yet other embodiments, the workpiece 102 and 202 is a lock pin or detent valve for use within an engine.

(21) Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.