METHOD FOR SKIVING MACHINING OF A WORKPIECE FOR PRODUCTION OF A CHAMFER

Abstract

A method for skiving machining a toothed workpiece includes the steps of: providing the toothed workpiece rotatable about a workpiece axis; providing a toothed tool rotatable about a tool axis; tilting the tool axis through an azimuth angle >0 with respect to an x direction; tilting the tool axis furthermore through a polar angle <90 with respect to a z direction; rotating the toothed tool about the tool axis, the toothed tool in a contact zone sliding over the toothed workpiece rotating about the workpiece axis. The workpiece axis defines the x direction and the perpendicular of the contact zone to the workpiece axis defines a z direction. The x direction, a y direction and the z direction form a Cartesian coordinate system. This method can easily produce a chamber on the toothed workpiece with the toothed tool which is subject to fewer geometric restrictions.

Claims

1. A method for skiving machining a toothed workpiece, the method comprising the steps of: providing the toothed workpiece rotatable about a workpiece axis; providing a toothed tool rotatable about a tool axis; tilting the tool axis through an azimuth angle >0 with respect to an x direction; tilting the tool axis furthermore through a polar angle <90 with respect to a z direction; rotating the toothed tool about the tool axis, the toothed tool in a contact zone sliding over the toothed workpiece rotating about the workpiece axis; wherein the workpiece axis defines the x direction and the perpendicular of the contact zone to the workpiece axis defines a z direction, and the x direction, a y direction and the z direction form a Cartesian coordinate system; and producing a chamfer on the toothed workpiece with the toothed tool.

2. The method for skiving machining a toothed workpiece of claim 1, wherein the azimuth angle is greater than or equal to 10.

3. The method for skiving machining a toothed workpiece of claim 1, wherein the azimuth angle is 2060.

4. The method for skiving machining a toothed workpiece of claim 1, wherein the polar angle is less than or equal to 70.

5. The method for skiving machining a toothed workpiece of claim 1, wherein the polar angle is 1050.

6. The method for skiving machining a toothed workpiece of claim 1, wherein while the chamfer is being produced, the toothed tool is moved in a relative manner only in the x direction toward the toothed workpiece.

7. The method for skiving machining a toothed workpiece of claim 1, wherein while the chamfer is being produced, the toothed tool is moved both in a relative manner in the x direction toward the toothed workpiece and in a relative manner in the z direction away from the toothed workpiece.

8. The method for skiving machining a toothed workpiece of claim 1, wherein while the chamfer is being produced, the toothed tool and the toothed workpiece are rotated synchronously with a smooth differential ratio.

9. The method for skiving machining a toothed workpiece of claim 1, wherein while the chamfer is being produced, the toothed tool and the toothed workpiece are rotated with a non-smooth differential ratio.

10. The method for skiving machining a toothed workpiece of claim 1, wherein only one chamfer of the toothed workpiece is produced at a time on an end side of the toothed workpiece.

11. The method for skiving machining a toothed workpiece of claim 1, wherein a chamfer of the toothed workpiece is produced on respective axially opposite end sides of the toothed workpiece at the same time.

12. The method for skiving machining a toothed workpiece of claim 1, wherein the toothed tool has asymmetrical tooth flanks in cross section perpendicularly to the tool axis.

13. The method for skiving machining a toothed workpiece of claim 12, wherein the toothed tool has, on its tooth flanks, an active cutting edge for contact with the toothed workpiece, having a cutting-edge angle 1 measured with respect to a radial direction, and an opposite, non-active cutting edge without contact with the toothed workpiece, having a cutting-edge angle 2 measured with respect to the radial direction, and in that |1||2|+10.

14. The method for skiving machining a toothed workpiece of claim 12, wherein the toothed tool has, on its tooth flanks, an active cutting edge for contact with the toothed workpiece, having a cutting-edge angle 1 measured with respect to a radial direction, and an opposite, non-active cutting edge without contact with the toothed workpiece, having a cutting-edge angle 2 measured with respect to the radial direction, and in that |1||2|+20.

15. The method for skiving machining a toothed workpiece of claim 1, wherein the toothed tool extends axially along the tool axis 8 mm or less away from the contact zone.

16. The method for skiving machining a toothed workpiece of claim 1, wherein the toothed tool extends axially along the tool axis 4 mm or less away from the contact zone.

17. The method for skiving machining a toothed workpiece of claim 1, wherein the toothed tool narrows, away from the contact zone in an axial section along the tool axis.

18. The method for skiving machining a toothed workpiece of claim 1, wherein the toothed tool narrows conically, away from the contact zone in an axial section along the tool axis.

19. An apparatus for skiving machining a toothed workpiece, comprising: a workpiece spindle for rotating the toothed workpiece about a workpiece axis that extends in an x direction; a tool spindle for rotating a toothed tool about a tool axis; a tool-spindle mount on which the tool spindle is held and which is displaceable in each case linearly in the x direction, a y direction and a z direction by means of a motorized displacement device, wherein the x direction, the y direction and the z direction form a Cartesian coordinate system; wherein the tool axis is tilted through an azimuth angle >0 with respect to the x direction; and wherein the tool axis is furthermore tilted through a polar angle <90 with respect to the z direction.

20. The apparatus of claim 19, wherein the tool-spindle mount is rotatable about an axis of rotation by means of a motorized turning device.

21. The apparatus of claim 20, wherein the axis of rotation about which the tool-spindle mount is rotatable extends in the z direction.

22. The apparatus of claim 19, wherein the tool spindle and a further tool spindle for rotating a further toothed tool about a further tool axis are held on the tool-spindle mount.

23. The apparatus of claim 22, wherein the further tool axis is tilted through a further azimuth angle , mirror-inverted in relation to the azimuth angle of the tool axis, with respect to the x direction, and wherein the further tool axis is tilted through the same polar angle with respect to the z direction as the tool axis.

24. The apparatus of claim 19, including a turning holder on which the workpiece spindle and at least one further workpiece spindle are arranged, and wherein at least one station having a gear hobbing head for hobbing machining the toothed workpiece on one of the workpiece spindles and furthermore a station having the tool-spindle mount for chamfering the toothed workpiece on another of the workpiece spindles by way of the skiving machining operation are set up on the apparatus.

25. The apparatus of claim 19, wherein the x direction and the z direction lie in a horizontal plane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The invention is illustrated in the drawing and explained in more detail by way of exemplary embodiments. In the drawings:

[0041] FIG. 1 shows a schematic illustration of the orientation of the workpiece and tool in the method according to the invention;

[0042] FIG. 2a shows a schematic illustration of the azimuth angle tilt of the tool in the method according to the invention;

[0043] FIG. 2b shows a schematic illustration of the further polar angle tilt of the tool in the method according to the invention;

[0044] FIG. 3 shows a schematic illustration of the rolling of the workpiece and tool in the method according to the invention; and

[0045] FIG. 4 shows a schematic oblique view of an embodiment of an apparatus according to the invention for skiving machining, for carrying out the method according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] FIG. 1 illustrates the method according to the invention for producing a chamfer on a toothed workpiece 1, in this case a gearwheel, by way of a tooth tool 2.

[0047] The toothed workpiece 1 is held in a workpiece spindle (not illustrated) which rotates the workpiece 1 about a workpiece axis WSA (cf. also arrow direction 3). The workpiece axis WSA at the same time defines an x direction. The workpiece 1 has a toothing 4 in which the individual teeth 5 extend substantially parallel to the workpiece axis WSA, in this case with a slight helix angle of about 15 with respect to the workpiece axis WSA. The tooth end edges 6 of the teeth 5 are substantially perpendicular to the workpiece axis WSA both on the front side 8 of the workpiece 1 and on the rear side 7 of the workpiece 1.

[0048] A chamfer is intended to be applied to the edges of the tooth end faces of the teeth 5 on the rear side 7 of the workpiece 1, which faces away from the observer. To this end, the workpiece 1 rolls against the tool 2. The tool 2 touches the workpiece 1 in the region of a contact zone KZ, which is located on the rear side 7 of the workpiece 1 in the variant shown, directly above the workpiece axis WSA. The perpendicular of the contact zone KZ to the workpiece axis WSA or the x-axis defines a z direction; the positive z direction is defined in this case from the x-axis to the contact zone KZ. It should be noted that the contact zone KZ has been illustrated in an exaggerated manner in FIG. 1; in actual fact, the spatial region in which the contact between the workpiece 1 and tool 2 takes place is very small.

[0049] The tool 2 has a toothing 9, wherein the teeth 10 are arranged substantially parallel to a tool axis WZA, about which the tool 2 rotates in a tool spindle (not illustrated), cf. also arrow direction 14. The tooth end faces 11, 12 of the teeth 10 are oriented substantially perpendicularly to the tool axis WZA.

[0050] According to the invention, the tool axis WZA is oriented in a particular manner with respect to the workpiece axis WSA or the x direction; this orientation can be described best in a Cartesian coordinate system having the axes x, y and z and with reference to conventional angle designations in spherical coordinates.

[0051] The tool axis WZA is tilted through an azimuth angle which is greater than 0 with respect to the x direction in the xy plane. In the variant shown, the azimuth angle is about 30. In order to identify this azimuth angle better, the projection 13 of the tool axis WZA onto the xy plane has additionally been indicated; the coordinates x, y, z represent a coordinate system that is shifted parallel to the xyz system and in which the tilt angle of the tool axis WZA can easily be directly identified.

[0052] The tool axis WZA is also tilted through a polar angle with respect to the z direction, wherein this polar angle is less than 90. In other words, the tool axis WZA is tilted through an angle out of the xy plane toward the z axis, wherein y=90. In the variant shown, the polar angle is about 50 and the angle accordingly about 40.

[0053] During the production of the chamfer, the workpiece 1 and the tool 2 are rotated as per the arrow directions 3, 14, and at the same time the tool 2 is moved relative to the workpiece 1 at least in the x direction toward the workpiece 1; if desired, in order to adapt the chamfer shape, a relative z movement can also be overlaid. The ratio of the rotational speeds (angular speeds) in this case corresponds generally to the inverse ratio of the numbers of teeth, i.e. the number of rotating teeth per unit time is the same for the workpiece 1 and for the tool 2. In the variant shown, the workpiece 1 has 29 teeth 5 around the circumference, whereas the tool 2 has 44 teeth 10 around its circumference. Accordingly, the rotational speed of the workpiece 1 is selected to be 44/29 times the rotational speed of the tool 2 (synchronous rotation with a smooth differential ratio). Alternatively, it is also possible to provide a difference in speed, i.e. the number of rotating teeth per unit time is slightly different for the workpiece 1 and for the tool 2 (rotation with a non-smooth differential ratio); for example, the rotational speed of the workpiece 1 could be 44.1/29 times the rotational speed of the tool 2, in order to influence the shape of the chamfer.

[0054] In the embodiment shown, the axial thickness AD of the tool 2 is relatively small, in particular compared with the depth of the toothing 4 of the workpiece 1. Furthermore, the tool 2 narrows away from the top side 15, in this case over its entire axial thickness AD in a substantially conical manner, i.e. the external radius of the teeth 10 is greater close to the top side 15 (on which the rake faces of the tool 2 are formed, cf. in this regard also FIG. 3) than close to the underside. As a result of these two measures, contact between the workpiece 1 and the tool 2 is restricted reliably to the region of the edges of the upper tooth end faces 11 of the teeth 10; in particular, the tooth flanks of the teeth 10 do not create any interfering contour on the workpiece 1 away from the upper end face 11 and the lower tooth end faces 12.

[0055] In FIGS. 2a and 2b, the tilt of the tool axis WZA with respect to the workpiece axis WSA is explained again in stages.

[0056] Proceeding from an initially parallel orientation of the workpiece axis WSA of the workpiece 1 (oriented in the x direction) and the tool axis WZA of the tool 2, first of all the tool 2 is tilted through the azimuth angle toward the y-axis, cf. FIG. 2a, this ending in the orientation provided with the reference sign 2. Such a tilt corresponds to conventional skiving.

[0057] With regard to this position, according to the invention, a further tilt through the angle toward the z direction (or the z axis) takes place, this ending with the orientation 2 of the tool 2, cf. FIG. 2b. As a result, the polar angle =90 is set up.

[0058] It goes without saying, that in practice, the angles and can be set in any desired order or even simultaneously relative to one another; similarly, the angles and can also be fixed on a machine tool. What is relevant for the method according to the invention is the final orientation (denoted by reference sign 2 here) of the tool 2 relative to the workpiece 1 during chamfer production.

[0059] FIG. 3 explains in more detail how the tool 2 creates a chamfer 30 on the teeth 5 of the workpiece 1. In the perspective shown, the viewing direction is approximately along the tool axis WZA onto the tool 2 and the workpiece 1.

[0060] The teeth 10 of the tool 2 each have, on the tooth end faces 31 facing the workpiece 1, an active cutting edge 32 that is on the left-hand side in FIG. 3. This active cutting edge 32, or the associated tooth flank, has in this case a cutting edge angle 1 of about 45 with respect to a radial direction 33 of the tool 2. A non-active cutting edge 34, or the associated tooth flank, which is located on the opposite side from the active cutting edge 32, has a cutting edge angle 2 of about 35 with respect to the radial direction 33. The teeth 10 thus have asymmetrical tooth flanks.

[0061] In the variant in FIG. 3, while the workpiece 1 and tool 2 roll, cf. the arrow directions 3, 14, the teeth 10 of the tool 2 dip from the side into the intermediate spaces between the teeth 5 of the workpiece 1. In the process, the active cutting edge 32 bears initially against a lower part of the edge, facing the tool 2, of the right-hand tooth flank 35 of a tooth 5 and then scrapes upward along the edge of the tooth flank 35; the tooth end face 31 of the tooth 10 is thus used as a rake face. As a result, the chamfer 30 is produced. The chamfer 30 is thus created here by a cutting movement from (axially) outside to inside. Chips are conveyed out of the intermediate spaces between the teeth 5 during this sequence. The non-active cutting edge 34, by contrast, does not touch the workpiece 1.

[0062] By moving the tool 2 along the workpiece axis WSA toward the workpiece 1 at least with one movement component, the chamfer 30 is enlarged (i.e. deepened and widened).

[0063] In the variant shown, the chamfer angle , that is to say the angle between the face of the chamfer 30 and the adjacent face of the tooth flank 35 (which in this case extends with a helix angle of about 25) is approximately 30 in the case of the teeth 5.

[0064] It should be noted that, by reversing the directions of rotation, scraping of the active cutting edge 32 from top to bottom along the edge of the tooth flank 35 of the tooth 5 can be set up.

[0065] FIG. 4 shows an apparatus 40 according to the invention (machine tool) for chamfering toothed workpieces 1, in particular in accordance with the method according to the invention.

[0066] The apparatus 40 has a station 41 for hobbing machining workpieces 1, having a gear hobber 42 which is equipped with conventional axes of rotation and movement. Furthermore, the apparatus 40 has a station 43 for chamfering workpieces 1, which is explained in more detail below; the station 43 is usually also used for changing workpieces, since chamfering a workpiece 1 usually requires less time than gear hobbing a workpiece 1.

[0067] In the embodiment shown, a turning holder 44 is provided, which is rotatable in the arrow direction 45 and can, as a result, position, in particular interchange, two workpiece spindles 46, 47 at the stations 41, 43. The turning holder 44 is in this case rotatable about a horizontal axis, and the workpiece spindle axes, about which the workpiece is 1 rotatable, are likewise arranged horizontally here. Typically, workpieces 1 are clamped on a workpiece spindle 46, 47 at the station 43, moved to the station 41 for gear hobbing by turning the turning holder 44, moved back to the station 41 for chamfering by turning the turning holder 44, and unclamped again; this sequence takes place in parallel on both workpiece spindles 46, 47 and in a manner offset through half a phase.

[0068] The station 43 for chamfering workpieces 1 is explained in more detail in the following text.

[0069] Arranged on a tool-spindle mount 48 are, in this case, a tool spindle 49 having a toothed tool 2 and also a further tool spindle 50 having a further toothed tool 51. The tool-spindle mount 48 can be moved linearly in the directions x, y, z, which are orthogonal to one another, by means of a motorized moving device (compound slide system) 52, and also be turned, by means of a motorized turning device 53, about an axis of rotation DA, which extends parallel to the z direction. The x direction is in this case oriented horizontally and parallel to the workpiece spindle axis of the workpiece spindle 46, the y direction extends vertically, and the z direction extends horizontally again.

[0070] In the moved position shown, a first chamfer is just being produced on the underside of the workpiece 1 on the workpiece spindle 46 with the tool 2 on the tool spindle 49; to this end, the tool 2 comes into contact with the workpiece 1 from the left-hand side, that is to say coming from the z direction. In order to produce the second chamfer on the underside, the tool-spindle mount 48 is repositioned with the motorized moving device (compound slide system) 52 such that the further tool 51 on the further tool spindle 50 comes into contact with the workpiece 1 from the left-hand side.

[0071] It should be noted that the tool axis WZA of the tool spindle 49 is tilted downward through an azimuth angle with respect to the x direction (cf. the associated parallel-shifted x axis and the projection 13 of the tool axis WZA), and that the further tool axis WWZA of the further tool spindle 50 is tilted upward through a mirror inverted azimuth angle with respect to the x direction (cf. the associated parallel-shifted x axis and the projection 13a of the further tool axis WWZA). It should also be noted that the tool axis WZA of the tool spindle 49 is tilted through a polar angle with respect to the z direction (cf. the associated parallel-shifted axis z), and the further tool axis WWZA of the further tool spindle 50 is pivoted through the same polar angle with respect to the z direction (cf. again the associated parallel-shifted axis z).

[0072] In order to produce the two chamfers on the top side 8 of the workpiece 1 in the workpiece spindle 46, the tool-spindle mount 48 is tilted through 180 about the rotation axis of rotation DA with the motorized turning device 53. Then, the first chamfer can be applied to the top side 8 of the workpiece 1 with the tool 2 and the second chamfer can be applied thereto with the further tool 51 (this not being illustrated in more detail).

[0073] It is noted that the total of four chamfers can in principle be applied to the workpiece 1 in any desired order. However, it is generally advantageous in terms of time to produce the two chamfers in each case on one side of the workpiece 1 (top side or underside) one directly after the other.

[0074] In summary, the invention describes a method for producing a chamfer (30) on a toothed workpiece (1), wherein a toothed tool (2) having tooth end edges (11, 31) that serve as rake faces and extend approximately perpendicularly to the tool axis (WZA) are rolled against the workpiece (1). In the process, an active cutting edge (32) formed on a lateral edge of the rake face (11, 31) slides over the edges of the tooth end faces (6) of the workpiece (1). The tool axis (WZA) is not only tilted through an azimuth angle with respect to the workpiece axis (WSA), as in conventional skiving, but additionally tilted through a polar angle of less than 90 with respect to the perpendicular of the contact zone (KZ) of the workpiece (1) and tool (2) to the workpiece axis (WSA). The application of the chamfers can, in the scope of the invention, be used for toothed workpieces of all kinds, in particular gearwheels, axles having toothed regions or gears, in particular when no or only a small clearance is present axially beyond the toothing on the workpiece and/or large chamfer angles are desired.