Method of finishing bevel gears to produce a diffuse surface structure
View Patent ↗A method for providing a surface structure wherein conventional grinding micro scratches are broken up to provide a diffuse structure of micro scratches and micro flats resulting from grinding wheel motion comprising an eccentric revolving of the grinding wheel and/or grinding wheel pulsing.
1. A method of grinding at least one tooth flank of a bevel gear with a grinding tool rotatable about a tool axis of a gear grinding machine having a plurality of machine axes, said method comprising:
rotating said tool and bringing said tool and said at least one tooth flank into engagement;
providing relative movement between said tool and said gear to traverse said tool across said at least one tooth flank in accordance with a predetermined relative rolling motion, said rolling motion comprising a plurality of contact lines between said tool and said at least one tooth flank thereby producing a predetermined number of grinding flats and a plurality of grinding scratches on said at least one tooth surface;
simultaneously with said generating roll, revolving said tool axis about an eccentric axis spaced from said tool axis, whereby a grinding tool generating cone is formed;
shifting the generating cone surface to introduce grinding flat modifications to at least one grinding flat during the predetermined relative rolling motion, said shifting comprising a shift in a direction of the root line of said at least one tooth flank and a shift in a direction generally perpendicular to the tooth profile symmetry line of said at least one tooth flank.
2. The grinding method of claim 1 wherein each of said contact lines is defined by a plurality of axes positions of said grinding machine, said method further comprising:
pulsing said tool simultaneously with said shifting, said pulsing occurring for at least one of said contact lines and being effected by modifying one or more of said plurality of axes positions for the respective said at least one of said contact lines.
3. The method of claim 1 wherein said shift in a direction of the root line of said at least one tooth flank and said shift in a direction generally perpendicular to the tooth profile symmetry line of said at least one tooth flank are defined, respectively, by:
Δ
FSO
(
t
)
=
R
E
[
cos
(
φ
E
)
-
cos
(
φ
E
+
2
π
n
60
·
t
)
]
Δ
FRA
(
t
)
=
R
E
[
sin
(
φ
E
)
-
sin
(
φ
E
+
2
π
n
60
·
t
)
]
where:
n=RPM of eccentric axis;
t=time in generating process from one flat to the next;
R E =radius of eccentric circle;
φ E =angle of rotation about the eccentric axis.
4. The method of claim 1 wherein said direction of the root line of said at least one tooth flank and said direction generally perpendicular to the tooth profile symmetry line of said at least one tooth flank are located in a plane, said tool axis being normal to said plane.
5. The method of claim 2 wherein said modifying one or more of said plurality of axes positions comprises adding and/or subtracting respective axis positioning units from theoretical axis positioning values.
6. The method of claim 5 wherein said adding and/or subtracting is carried out in accordance with a linear or higher order function.
7. The method of claim 5 wherein said adding and/or subtracting is carried out in a random manner.
8. The method of claim 2 wherein flat-to-flat modifications are limited to a predetermined amount.
9. The method of claim 2 wherein the first flat-to-last flat modifications are limited to a predetermined amount.
10. The method of claim 2 wherein pulsing directions are defined with respect to said generating cone vectors.
11. The method of claim 10 wherein the pulsing cone vectors extend in at least one of the following directions:
a) tangential to a grinding flat represented on the periphery of the cone section;
b) tangential to the peripheral surface of the cone section in the axial plane of the grinding tool;
c) in the axial direction of said tool;
d) radially in a direction normal to said flat;
e) radially in a direction tangential to said flat.
12. The method according to claim 2 wherein the combination of the modified one or more axes positions changes from flat-to-flat.
13. The method according to claim 2 wherein the quantity of the modified change of the one or more axes positions changes from flat-to-flat.
14. The method of claim 1 wherein said gear is a pinion member of a bevel gear set.
15. The method of claim 1 wherein said gear is a ring gear member of a bevel gear set.
16. The method of claim 2 wherein said gear is a pinion member of a bevel gear set.
17. The method of claim 2 wherein said gear is a ring gear member of a bevel gear set.
18. The method of claim 1 wherein said method is carried out on a pinion member of a bevel gear set and a ring gear member of said bevel gear set, and wherein shifting is effected in different amounts for each of the pinion and the ring gear.
19. The method of claim 2 wherein said method is carried out on a pinion member of a bevel gear set and a ring gear member of said bevel gear set, and wherein shifting is effected in different amounts for each of the pinion and the ring gear and pulsing is effected by different axes position modifications for each of the pinion and the ring gear.
20. The method of claim 3 wherein the RPM value varies during said relative rolling motion.