METHOD FOR MACHINING A SET OF TEETH, TOOL ARRANGEMENT, AND TOOTH-CUTTING MACHINE

Abstract

The invention relates to a method for machining a toothing, wherein to form a chamfer on a tooth edge formed between an end face of the toothing and a tooth flank belonging to a tooth space of the toothing, material is removed from the tooth edge by cutting, by means of a machining tool equipped with a cutting edge, in a machining operation, wherein the machining tool is toothed and the machining operation is a skiving machining operation at an axis intersection angle between the rotational axes of the machining tool and the toothing, which does not extend beyond the tooth root section of the tooth space

Claims

1. A method for machining a toothing (2), wherein to form a chamfer (5) on a tooth edge formed between an end face (6) of the toothing and a tooth flank belonging to a tooth space (4) of the toothing, material is removed from the tooth edge by cutting, by means of a machining tool (15) equipped with a cutting edge, in a machining operation, characterized in that the machining tool is toothed and the machining operation is a skiving machining operation at an axis intersection angle (Σ) between the rotational axes (Z10, Z2) of the machining tool and the toothing, which does not extend beyond the tooth root section of the tooth space.

2. The method according to claim 1, wherein a chamfer (9) on the other tooth edge of the same tooth space (4) is also generated on the same end face (6), but in a subsequent, separate other machining operation.

3. The method according to claim 1, wherein the other machining operation is carried out with a different other machining tool (19).

4. The method according to claim 2 wherein the other machining operation is executed at a different axis intersection angle.

5. The method according to claim 1 wherein first toothing data of a first equivalent toothing (B), whose helix angle is determined by the orientation of the chamfer (5), wherein the transverse section profile thereof matches that of the toothing being machined in the transition (8) from the tooth flank into the tooth edge chamfer being formed, is determined from predetermined chamfer parameters for the chamfer which relate to its size and its orientation to the end face, as well as from toothing parameters of the toothing being machined, relating to its profile, or, profile and helix angle.

6. The method according to claim 2 wherein second toothing data of a second equivalent toothing (C), whose helix angle is determined by the orientation of the chamfer (9), wherein the transverse section profile thereof matches that of the toothing being machined in the transition from the tooth flank into the other tooth edge chamfer being formed, is determined from predetermined chamfer parameters for the chamfer which relate to its size and its orientation to the end face, as well as from toothing parameters of the toothing being machined, relating to its profile, or, profile and helix angle.

7. The method according to claim 5, wherein the machining tool is configured according to the first toothing data, and the machining tool is a circular skiving tool (15) designed to generate the first equivalent toothing by skiving.

8. The method according to claim 6 wherein the other machining tool is configured according to the second toothing data, and the other machining tool is a circular skiving tool (19) designed to generate the second equivalent toothing by skiving.

9. The method according to claim 3 wherein the machining tool and the other machining tool have a shared axis of rotation (Z10) which can pivot by more than 180°.

10. The method according to claim 3 wherein at least one of the machining tool and the other machining tool designed as a straight-toothed circular skiving tool.

11. The method according to claim 3 wherein the axis intersection angle of at least one of the machining tool and the other machining tool is set to the helix angle (β.sub.B, β.sub.C) of the first or second equivalent toothing.

12. The method according to claim 1 wherein a non-zero tilt angle is set between the axis of rotation of the machining tool and a plane which is orthogonal to the connecting direction between the centers of the toothing and the machining tool, by means of an offset in the plane which is orthogonal to the toothing axis.

13. A tool arrangement (10) for forming a chamfer (5; 9) on the tooth edges formed between an end face of a toothing and its tooth flanks, having a first wheel-like machining tool (15) which is toothed on the front, the axis of rotation (Z10) of which can be pivoted by more than 180° to form the chamfer (5) on one side of the tooth space (4) of the toothing, and having a second wheel-like machining tool (19) which is toothed on the front, with the same axis of rotation (Z10) to form the chamfer (9) on the other side of the tooth space.

14. The tool arrangement according to claim 13, wherein the first and/or second machining tool (15; 19) has straight teeth.

15. The tool arrangement according to claim 13, wherein the first and second machining tools are each made in the form of a cylindrical skiving tool (15; 19), the crown circle diameters of the tools do not differ by more than 15%, and the machining tools are formed without at least one of a cutting face angle and relief grinding.

16. The tool arrangement according to claim 13 having a shared drive for both machining tools, engaging between the machining tools.

17. The tool arrangement according to claim 13 wherein a cutting surface of the machining tools is a direct contact surface on the tool spindle.

18. The tool arrangement according to claim 13 wherein the front sides with the cutting edges of the machining tools face toward each another or face away from each other.

19. A chamfering station having a tool arrangement (10) according to claim 13 with at least one linearly independent linear machine axes (X, Y, Z) for positioning the tool arrangement with respect to a workpiece position.

20. A toothing machine, having a workpiece spindle to receive a workpiece in a manner allowing rotary drive, having a primary tool for generating a toothing (2) on the workpiece, and having a machine axis (A10) for setting an axis intersection angle between a toothed machining tool (15; 19) for forming a chamfer (5; 9) on a tooth edge formed between an end face (62) of the toothing and a tooth flank belonging to a tooth space (4) of the toothing, characterized by a control device which is programmed to allow running a method on the toothing machine according to claim 1.

Description

[0030] The invention is described with reference to the drawings; reference is expressly made to the drawings for all details which are essential to the invention and are not exhibited in greater detail in the description, wherein:

[0031] FIG. 1 shows a sectional view of a toothing and the normal section profile of the toothing, and two virtual equivalent toothings,

[0032] FIG. 2 shows a tool arrangement with two chamfering circular skiving tools,

[0033] FIG. 3 shows a positional relationship between the axes of rotation of the toothing and the circular skiving tool, and

[0034] FIG. 4 shows another positional relationship of the axes of rotation of the toothing and the circular skiving tool.

[0035] The lower region of FIG. 1 shows an axial sectional view of a toothing 2, wherein the sectional plane passes through two teeth of the toothing 2, wherein the tooth space 4 lies between their mutually facing tooth flanks 3 and 7. The sectional plane is thus orthogonal to the end face 6 and is parallel to the toothing axis Z2 of the toothing 2.

[0036] In the upper portion of FIG. 1, the normal section profile of the toothing 2 is shown, and the toothing 2 is denoted by A.

[0037] Since the toothing 2 is a helical toothing, an obtuse angle is formed between the tooth flank 3 and the end face 6, while between the tooth flank 7 and the end face 6, an acute angle is formed. This leads to different orientations of the chamfer 5 to be formed on the front edge of the tooth flank 3 and of the chamfer 9 to be formed on the front edge of the tooth flank 7, which are also plotted in FIG. 1 below. These orientations, as well as the chamfer size—here measured as the distance of the end face 6 to a front transverse plane 8 where the tooth flanks 3, 7 transition into the chamfers 5, 9—are prespecified, for example as part of the above-mentioned tolerance ranges. The toothing 2 is with the chamfers 5, and 9 is thus defined by, on one hand, the toothing parameters for the generation of the toothing, which include the normal section profile of A, as well as the helix angle R of the toothing, and the chamfer parameters of the chamfers 5 and 9, which include the orientation relative to the transverse plane and the chamfer size thereof. The profile of the toothing A can be, for example, an involute profile; the toothing parameters of the toothing 2 could be, by way of example: module=5 mm, pressure angle=20°, helix angle β=25°, and profile shift coefficient of 0.17.

[0038] For now, the toothing 2 will be considered only in the region between the transverse plane 8 and the end face 6—that is, only a “thin” slice of the toothing 2, the width of which is determined by the chamfer size. In this thin slice, the normal section profile is determined for both sides of the space, representing the virtual equivalent toothings B, C in the wording of the claims. Because of the chamfers 5, 9 which will be formed, different toothing data results for these equivalent toothings B, C.

[0039] FIG. 1 illustrates the normal section profile of the particular equivalent toothing B determined on the side of the chamfer 5, and the equivalent toothing C belonging to the chamfer 9. Specifically, for the embodiment of the equivalent toothing B, a module of 3.472 mm, a helix angle of 55.09° right, and a profile shift coefficient of −2.915 result, while the toothing data for the equivalent toothing C is: module 5.162 mm, helix angle 19.91° left, profile shift coefficient 0.291. In the transverse plane 8, the transverse section profiles of A and B transition into one another on the side of the tooth flank 3; on the side of the tooth flank 7, the end section profiles of A and C transition into each other.

[0040] According to this perspective, the toothing 2 with the chamfers 5 and 9 is thus composed of the region between the end face 6 and the transverse plane 8 of the toothing B on the side of the chamfer 5, and the toothing C on the side of the chamfer 9 and the adjoining region up to the other end face (or the chamfers formed there) of the toothing A. The formation of the chamfers 5, 9 is then achieved by designing circular skiving tools, wherein the design in chosen such that using these circular skiving tools, the equivalent toothings B and/or C could be generated in the circular skiving tool kinematics. If at this point a previously-generated toothing 2 is assumed which corresponds to the toothing A, and no chamfers have been formed on the front edges, then the chamfer 5 and the chamfer 9 are formed one after the other with the circular skiving tool designed for the toothings B and/or C, under the kinematic conditions of the skiving.

[0041] FIG. 2 illustrates a tool arrangement 10 in a perspective view. A CNC-controlled drive, here a belt drive (not shown) of the tool arrangement 10, drives the single tool spindle thereof, whose spindle axis defines the tool rotational axis Z10 of the circular skiving tools 15 and 19, the same directly contacting the tool spindle with their mutually-facing cutting surfaces. In addition, the tool arrangement 10 must be housed in a chamfer station, able to pivot about a pivot axis A10, such that the circular skiving tools 15, 19 for chamfering are able to switch the positions shown in FIG. 2, and can be set for the machining to a desired axis intersection angle for the toothing axis Z2.

[0042] The tool spindle thus receives both circular skiving tools 15, 19 for the chamfering simultaneously, yet only one of the two circular skiving tools 15, 19 is in machining engagement with the toothing 2.

[0043] Both the circular skiving tool 15 for the chamfering, which is provided to generate the chamfer 5, and the circular skiving tool 19 for the chamfering, which is provided to generate the chamfer 9, are simply designed in the form of straight-toothed, cylindrical spur gears, wherein the teeth thereof are not illustrated in FIG. 2 on the end face of the circular skiving tools. After each regrinding, the cutting surfaces are in turn used as a contact surface on the tool spindle, such that the axial position of the cutting edge relative to the tool spindle does not change. In addition, due to the cylindrical shape of the straight circular skiving tool teeth, the radial position of the teeth relative to the tool spindle also does not change. The setup of the chamfering station, and its operation, are accordingly simple.

[0044] It is understood that the design of the tool arrangement with the circular skiving tools 15 and 19 for chamfering, as described above, is only an example, and that of course there is also the possibility of using ground circular skiving tools, or circular skiving tools with cutting face angle, as well as helical circular skiving tools and/or circular skiving tools with step cut, and combinations thereof.

[0045] The machine axes of a chamfering station comprising this tool arrangement 10 are therefore the rotation axis Z10, which can be operated by the CNC-controlled drive in synchronism with the rotation of the toothing axis Z2 of the workpiece, and the pivot axis A10. Furthermore, the tool arrangement 10 can be positioned relative to the workpiece via three linear axes (X, Y, Z,) by a pivot unit which is responsible for the axis A10, for example via cross-carriage assemblies. Thus, a linear movement axis Z can be configured for a movement parallel to the toothing axis Z2, a linear axis X can allow a radial approach/dip movement, and a linear axis Y can provide a tangential, additional linearly independent movement axis. The chamfering station thus acquires similar machine axes to those which primary tool assemblies (for instance with hobs) typically have.

[0046] FIG. 3 illustrates the relative position of the axes of rotation Z2 of the toothing 2 and Z10 of one of the circular skiving tool 15 or 19 for chamfering, in a simplest variant, in a perspective view (FIG. 3a), a top view (FIG. 3b) and a rear view (FIG. 3c), in viewing direction X. A plane E1 is thereby defined, in which lie the rotation axis Z2 of the toothing 2, as well as the tool center point of the circular skiving tools 15 (19) for chamfering. The axis intersection angle >arises from a plane E2 which is orthogonal to the plane E1 and passes through the tool center point; it is the angle between the axis of intersection of the planes E1 and E2 and the tool axis of rotation Z10. In this embodiment, the chamfering circular skiving tool has straight teeth and the axis intersection angle is set to the angle of inclination β of the respective equivalent toothing—that is, in the machining operation of the circular skiving tool 15 for chamfering, to form the chamfer 9 the axis intersection angle is set to the helix angle of the equivalent toothing C (Σ=β.sub.C); the machining proceeds analogously in the machining operation of the chamfering circular skiving tool 19 to form the chamfer 5, at an axis intersection angle which is set to the helix angle of the equivalent toothing B (Σ=β.sub.B). With balancing corrections, ρ≠β.sub.C could also be used.

[0047] If, by way of example, the circular skiving tool 15 in the illustration of FIG. 3 works by single-flank machining to form the chamfer 9, then after the withdrawal of the chamfering circular skiving tool 15, the chamfering circular skiving tool 19 can be brought into machining engagement with the tooth flank 3 to form the chamfer 5, by the pivot axis A10 being used to set the right axis intersection angle β.sub.B and by positioning axes X, Y, Z being used to actuate the positioning movements for the machining operation. Because of the axial distance between the chamfering circular skiving tools 15 and 19, there is no risk of collision of the respective chamfering circular skiving tool which is not operating with the toothing 2.

[0048] A corresponding machining operation can follow on the other end face of the toothing 2 in an analogous manner, wherein the positioning axis Z enables the correct height, and due to the pivoting ability of the pivot axis A10, both chamfering circular skiving tools 15, 19 can switch their roles, since on the other end face the tooth flank 3 forms the acute angle and receives the chamfer 9, while the tooth flank 7 assumes an obtuse angle with the other end face and receives the chamfer 5.

[0049] For the machining operations, the correct skiving positions of the chamfering circular skiving tools relative to the toothing 2 of the workpiece must be maintained. In addition, depending on the accuracy requirements, the height of the end faces 6 of the toothing must be determined exactly for achieving the correct chamfer size.

[0050] As already explained further above, centering operations are carried out for this purpose with respect to the synchronous skiving motions. If, however, the rotational position of the chamfering circular skiving tools is known, and the workpiece toothing is not clamped in place between operations, the required phase position of the chamfering circular skiving tool for the workpiece toothing may already be available from the synchronous skiving motion, for example when the toothing 2 is generated by means of skiving, such that no additional centering operations are required due to a shared control. The determination of the height of the end faces of the toothings can be performed by sensors, as explained above—and also outside the machining station.

[0051] FIG. 3 illustrates the E1 plane—the X, Z plane—while the E2 plane is the Y, Z plane, and the connecting line between the centers of the toothing 2 and the chamfering circular skiving tool 15 (19) runs along the radial positioning axis X.

[0052] In the method variant shown in FIG. 4, the chamfering circular skiving tool, with its tool center, is offset out of the plane E1 (offset Y) relative to the variant in FIG. 3, and optionally also offset by other offset quantities X, Z. In this case, the connecting line CC between the workpiece center and the tool center, as well as the workpiece axis, defines a plane E3 which intersects plane E1 at an angle φ. The tool axis Z10 running in E2 then no longer lies in a normal plane E4 to CC passing through the tool center. Rather, it is inclined with respect to the same (additional tilt angle). By way of example, the helix angle β.sub.C (for chamfering circular skiving tool 15) and/or β.sub.B (for chamfering circular skiving tool 19) will be used for further operations (with straight-toothed chamfering circular skiving tools). The pivot angle to be set on the pivot axis A10 then no longer corresponds to the helix angle β.sub.C (and/or β.sub.B). Rather, it is modified as in a projection (for a base setting: tan ρ′=cos φ tan Σ). The machine axis configuration with a non-zero tilt angle increases the variability of the method, and, because of the change in the cutting direction, allows additional opportunities to influence the formation of the chamfer without needing to require an additional pivot axis (the offset is sufficient).

[0053] The invention is not limited to the specific features indicated in the preceding description of the figures. Rather, the features of the appended claims and the above description can be essential individually and in combination to the implementation of the invention in its various embodiments.