Gear processing by hob peeling, hard peeling or gear forming, and corresponding gear cutting tools

Abstract

The present invention relates to a method for producing or machining at least one gear tooth section on at least two workpieces by hob peeling, hard peeling or gear forming using a toothed tool in the form of a peeling or forming wheel having cutting edges on a first end face along first and second tooth flanks of the tool teeth, wherein the contour of the cutting edges of the first tooth flank on the first end face is formed asymmetrically with respect to the contour of the cutting edges of the second tooth flank on the first end face, and wherein gear machining of one of the at least two workpieces is performed with the cutting edges on the first end face, and cutting edges are similarly formed on a second end face of the tool opposite the first end face, for gear machining of another of the at least two workpieces, where the contour of the cutting edges of the first tooth flank is identical to the contour of the cutting edges of the second tooth flank on the first end face and the contour of the cutting edges of the second tooth flank is identical to the contour of the cutting edges of the first tooth flank on the first end face.

Description

[Technical Field]

[0001] The present invention relates to a method for producing or machining at least one gear toothing on at least two workpieces by hob peeling, hard peeling or gear forming using a toothed tool in the form of a peeling or forming wheel having cutting edges on a first end surface along first and second tooth flanks of the tool teeth. [Background technology]

[0002] All three methods are known in gear technology. Hob peeling and gear shaping are soft machining methods, while hard peeling is a hard finishing process of pre-cut hardened gear teeth using the kinematics of hob peeling. Furthermore, all three methods involve tools (shaping wheels or peeling wheels) with geometrically defined cutting edges. When machining multiple workpieces, in particular large batches of more than 40, especially more than 100, or even several hundred workpieces, the cutting edges wear due to continuous machining. To remedy this, the tools are reground as needed. For example, it is common practice to remove the tool from the machine, reground it, and then recoat it. DE 102017011978 A1 explains how and why regrinding can also be performed on the gear cutting machine itself. German Patent Application Publication No. 102021108379 (A1) discusses disposable hob peeling tools that are no longer used after reaching their wear limit. These are designed as spur teeth with a symmetrical profile, and the basic shape of the tool is that of a cylindrical disk. German Patent Application Publication No. 102017114088 (A1) also discloses a symmetrical tool. German Patent Application Publication No. 102014008475 (A1) discloses the use of the rear part of a peeling wheel as a tool for removing burrs. German Patent Application Publication No. 102012012617 (A1) discloses a feed strategy that reduces tool wear primarily by avoiding U-shaped chipping. Summary of the Invention

[0003] The present invention is based on the object of improving a method of the type mentioned above with regard to a favourable combination of flexibility in terms of feed strategy and tool design, with a satisfactory tool life and high machining accuracy.

[0004] This object is achieved in terms of machining technology by developing a method of the type mentioned at the beginning, which is essentially characterized in that the contour of the cutting edges of a first tooth flank on a first end face is formed asymmetrically with respect to the contour of the cutting edges of a second tooth flank on the first end face, gear machining of one of the at least two workpieces is carried out by the cutting edges of the first end face, and cutting edges are similarly formed on a second end face of the tool opposite the first end face and are used to gear machine another of the at least two workpieces, where on the second end face the contour of the cutting edges of the first tooth flank is identical to the contour of the cutting edges of the second tooth flank on the first end face and the contour of the cutting edges of the second tooth flank is identical to the contour of the cutting edges of the first tooth flank on the first end face.

[0005] The method according to the invention achieves, on the one hand, a relatively high machining accuracy and a sufficiently simple machining process, since the minimal deviations in the machining result that would otherwise occur due to the machining positions of the trailing flank and the leading flank are compensated for by the asymmetry of the cutting edge contour on one of the end faces, and, on the other hand, due to the asymmetry of the contour, the back surface of the tool can also be used to machine workpieces of a workpiece batch without the need to calculate and set new machining and engagement positions and, for example, regardless of the helix angle (β≧0) of the tool gear tooth.

[0006] In a preferred method variant, it is assumed that the sign of the scalar product of the outward normal to the first end face and the workpiece rotation axis during gear machining of the first workpiece is the same as the sign of the scalar product of the outward normal to the second end face and the workpiece rotation axis during machining of the second workpiece. In one possible variant, this can be achieved by re-clamping the tool with respect to its orientation on the tool spindle. In another variant, this can be achieved by utilizing the motion axes of the gear cutting machine. In this context, it is considered that the gear cutting machine preferably has three linear motion axes and at least one pivot axis, and the pivotability of the tool spindle supporting the tool is greater than 180°, preferably greater than 210°, in particular greater than 240°.

[0007] In a further preferred embodiment, it is envisaged that the base circle of the left flank of the tool gear toothing is different from the base circle of the right flank of the tool gear toothing.

[0008] In this context, it is preferably envisaged that the magnitude of the base circle diameter difference is greater than 0.03 mm, preferably greater than 0.04 mm, in particular greater than 0.05 mm, and more preferably less than 0.8 mm, more preferably less than 0.7 mm, in particular less than 0.6 mm, which leads to particularly high-precision machining results.

[0009] Furthermore, it is preferred that when generating or machining left-hand helical gear toothing the base circle diameter of the right flank of the tool gear toothing is larger than the base circle diameter of the left flank of the tool gear toothing, and vice versa when generating / machining right-hand helical gear toothing. Preferably, the axis intersection angle is greater than 5°, in particular greater than 10°, and more preferably equal to or less than 40°, in particular equal to or less than 35°.

[0010] Furthermore, the normal module of the tool is preferably greater than 0.4 mm, more preferably greater than 0.6 mm, and in particular less than or equal to 4 mm, more preferably less than or equal to 3.5 mm, which provides particularly high-precision machining results.

[0011] In one possible design, the tool has straight teeth. However, such a tool cannot be used to produce straight-toothed workpieces using hob peeling. Therefore, in another preferred variant, the tool is helical, in particular with step grinding on both end faces, and the rake face contours are substantially parallel in the circumferential direction on both end faces.

[0012] As materials for the tools, for example, hard metals (HM) are used, although variants in which the tools are manufactured using powder metallurgy (high-speed steel (HSS), powder metallurgy high-speed steel (PM-HSS)) are also contemplated.

[0013] To save material or avoid collisions with interference profiles, the tool gear tooth width (the axial tool dimension relative to the tool rotation axis) can be small, less than approximately 1.8 cm, in particular less than 1.5 cm, or even less than 1 cm. However, for sufficient rigidity, it is preferred that the tool gear tooth width be at least 4 mm. The tool can have a coating that is more wear-resistant than its substrate; in this regard, German Patent Application Publication No. 102017011978 A1 is incorporated by reference. The tool can be designed as a disposable tool.

[0014] In addition to the basic cylindrical shape for straight gear cutting tools, a double conical shape can also be considered, with the outer diameter being the same at both end faces but tapering towards the axial tool centre (the axial tool is centred between the two end faces).

[0015] In gear forming variants, it is understood that a second tool end face requires a different clamping mechanism. In addition to double-flank machining, hard-peel machining also involves a single-flank method, where only one flank of the workpiece gear tooth is machined at a time. The teeth of tools prepared for this purpose are thinner in the circumferential direction to ensure no contact with the opposite flank while maintaining the asymmetry of the profile.

[0016] With regard to tool technology, the invention provides a tool for producing or machining at least one gear toothing on at least two workpieces by hob peeling, hard peeling or gear forming, the tool being essentially characterized in that the cutting edge profile of a first tooth flank on a first end face is asymmetrically formed relative to the cutting edge profile of a second tooth flank on the first end face, and that the cutting edges are similarly formed on a second end face of the tool opposite the first end face, where the cutting edge profile of the first tooth flank is identical to the cutting edge profile of the second tooth flank on the first end face and vice versa.

[0017] The advantages of the tool according to the invention arise from the above description of the method according to the invention, which is preferably carried out in the hob peeling variant (soft machining).

[0018] The invention also provides a method for generating such a tool, for which purpose it is envisaged that in one method step a basic gear toothing is generated on the tool, which still has room for the final tool geometry, and in a subsequent machining step an asymmetric cutting edge contour is formed on one end face and an inverted asymmetric machining contour is formed on the other end face.

[0019] Furthermore, the invention also provides a gear cutting machine that is suitable for carrying out the method according to the invention and is controlled for that purpose, as well as a corresponding control program. [Brief explanation of the drawings]

[0020] Further features, details and advantages of the invention can be found in the following description, taken in conjunction with the accompanying drawings. [Figure 1] FIG. 2 is a perspective view of a peeling wheel. [Figure 2] FIG. 1 is an enlarged view of a peeling wheel tooth, showing the asymmetrical profile in a schematic (exaggerated) manner. [Figure 3] 1 shows a variation of the double cone design. [Figure 4] 1 shows a variant with double step grinding. [Figure 5A] Illustrate the machining operation. [Figure 5B] Illustrate the machining operation. DETAILED DESCRIPTION OF THE INVENTION

[0021] The peeling wheel 100 shown in Figure 1 has a radially central through opening 3 that can be used to clamp the peeling wheel 100 to a tool spindle (not shown) of a gear cutting machine in a manner known to those skilled in the art, and a plurality of radially outwardly directed teeth 4. In this embodiment, the peeling wheel 100 is toothed all around, i.e., there is a tooth 4 at every pitch. In other embodiments, the teeth may be omitted, meaning that there are no teeth 4 at every pitch.

[0022] The peeling wheel 100 has cutting edges 11, 12 on its first end face 10, with the first cutting edge 11 being formed at the edge between the first end face 10 and the first tooth flank 5, and the second tooth edge 12 being formed at the edge between the first end face 10 and the second tooth flank 6 of the tool teeth 4. The peeling wheel 100 also has cutting edges on its opposite second end face 20, namely cutting edges 21 and 22. The cutting edge 21 is formed at the edge between the second end face 20 and the first tooth flank 5, and the other tooth edge 22 is formed at the edge between the second end face 20 and the second tooth flank 6 of the peeling wheel teeth 4.

[0023] 1 does not yet reveal the asymmetry provided according to the invention between the cutting edges 11, 12 of the first end face 10 and the cutting edges 22, 21 of the second end face 20. This asymmetry is also so slight that it is practically invisible to the naked eye, even under magnification as in FIG. 2. For this reason, the cutting edge contours P, Q in FIG. 2 clearly exaggerate the schematic asymmetry. FIG. 2 shows how the cutting edge contour P of the first tooth flank 5 differs from the cutting edge contour Q of the second tooth flank 6 at the first end face 10. At the opposite end face 20, this same asymmetry is reversed, so that the cutting edge of the second tooth flank 6 has a contour P and the cutting edge of the first tooth flank 5 has a contour Q. Considering only one tooth flank, the intersection of the tooth flanks is provided when viewed in its end face region, similar to the term used for toothed workpieces.

[0024] 5A shows the machining of the first workpiece gear tooth 201 by the peeling wheel 100. A typical axis crossing angle Σ between the rotation axis ω2 of the workpiece gear tooth 201 and the ω1 of the tool can be seen. The machining of the gear tooth 201 is performed by the cutting edge of the first end face 10 of the peeling wheel 100, which in the example shown has its outward normal vector n 10and the workpiece rotation axis ω2 is negative. The example in FIG. 5B shows a machining operation for producing the same gear tooth 202, but on a different workpiece. Here, the cutting edge intersects at the second end face 20, and likewise, the scalar product of its outward normal vector and the rotation axis ω2 of the gear tooth 202 is negative. To produce the machining positions shown in FIGS. 5A and 5B, the clamping orientation of the peeling wheel 100 can be changed. However, without changing the clamping, the pivot axis of the gear cutting machine performing the machining, which is also provided for setting the axis intersection angle Σ, can also be pivoted 180°, and the machining position can be adjusted by adjusting the linear axes, for example, by superimposing the movement of a linear axis extending along the workpiece rotation axis, the movement of a tangential axis (positioning axis) extending perpendicular to this axis, and the movement of a radial axis.

[0025] In one embodiment, larger batches of workpieces are machined having identical gear teeth 201, 202. For this purpose, a first group of workpieces is machined as shown in Figure 5A, followed by a second group of workpieces as shown in Figure 5B. Only afterwards is the peeling wheel 100 replaced and, if necessary, both end faces thereof reground.

[0026] When a cylindrical peeling wheel is used, as shown in FIG. 1, machining is preferably performed off-center, i.e., offset, as shown in FIG. 5. The axis intersection point X and the machining location BP are spaced apart to provide a kinematic clearance angle. When a double cone configuration is used instead of a cylindrical configuration, as shown in FIG. 3, machining can also be performed at the axis intersection point since a constructive clearance angle exists. FIG. 3 shows how the outer diameter D varies across the width B of the peeling wheel 100 in the double cone shape.

[0027] When a straight-toothed workpiece gear tooth is to be produced or machined, a helical peeling wheel is used instead of a straight-toothed tool, as shown in Figure 1. In this case, both end faces of the peeling wheel are preferably ground with a step grinding pattern, and the step grinding direction extends parallel to the circumferential direction of the upper and lower end faces (Figure 4).

[0028] In a first exemplary embodiment, the workpiece gear toothing 201 / 202 is produced with the following parameters: number of teeth 85, helix angle = 0°. For this purpose, a peeling wheel with asymmetrical profiles P and Q is produced with a difference Δ P-Q is used at about 0.59 mm, Q is the profile of the leading flank being machined, and P is the profile of the trailing flank being machined. Other tool parameters are the normal module m n = 2.97, helix angle 20°, pressure angle 25°, and number of teeth 51.

[0029] In a second exemplary embodiment, a right-hand helical workpiece with a 14° helix angle and 84 teeth is produced by a helical tool with a 20° cross-axis angle and a 6° helix angle. The peeling wheel has a module of 2.0, an engagement angle of 20°, and 50 teeth. The asymmetry, expressed as a base diameter difference, is 0.055 mm.

[0030] In yet another third exemplary embodiment, a straight gear toothing is produced, but here with 52 teeth and here with a cross-axis angle of 15°. A peeling wheel with a module of 0.75 and a helix angle of 15° is used, with an engagement angle of 30° and 39 teeth. The asymmetry between the right and left flanks of the workpiece gear toothing, expressed as a base diameter difference, is 0.11 mm.

[0031] In yet another fourth exemplary embodiment, a left-hand helical gear toothing with 59 teeth is produced. In this case, the base diameter of the left tool flank is larger than that of the right tool flank by 0.15 mm. Other tool data are a module of 1.3, an engagement angle of 20°, and the peeling wheel is a straight toothed wheel with 80 teeth.

[0032] On the opposite end face of the exemplary cutter, the asymmetry between the left and right flanks is reversed.

[0033] The present invention is not limited to the specific embodiments and examples described above, but rather the features of the above description and the following claims may be essential both individually and in combination to implement the invention in its different embodiments.

Claims

1. 1. A method for producing or machining at least one gear tooth portion (201, 202) on at least two workpieces by hob peeling, hard peeling or gear forming using a toothed tool (100) in the form of a peeling or forming wheel having cutting edges (11, 12) on a first end face (10) along first and second tooth flanks of the tool tooth (4), comprising: a profile (P) of the cutting edge (11) of the first tooth flank (5) at the first end face is formed asymmetrically with respect to a profile (Q) of the cutting edge (12) of the second tooth flank (6) at the first end face, gear machining of one of the at least two workpieces is performed by the cutting edge on the first end face, and cutting edges (21, 22) are similarly formed on a second end face (20) of the tool opposite the first end face to perform gear machining of another of the at least two workpieces, wherein at the second end face, the profile (Q) of the cutting edge (21) of the first tooth flank is identical to the profile (Q) of the cutting edge of the second tooth flank (12) at the first end face and the profile (P) of the cutting edge (22) of the second tooth flank is identical to the profile (P) of the cutting edge of the first tooth flank (11) at the first end face.

2. During gear machining of the first workpiece, an outward normal (n 10 ) and the workpiece rotation axis (W 2 ) during machining of the second workpiece, the sign of the scalar product with the outward normal (n 20 ) and the workpiece rotation axis (W 2 2. The method of claim 1, wherein the sign of the scalar product of

3. 3. The method according to claim 1, wherein the asymmetry of the cutting edge profile (P⇔Q) increases from the cutting edge to the root relative to a symmetrical reference profile.

4. 4. The method according to claim 1, wherein the base circle of the left flank of the tool gear toothing is different from the base circle of the right flank of said tool gear toothing.

5. The method according to any one of claims 1 to 4, wherein the tool is straight-toothed.

6. 5. The method according to claim 1, wherein the tool is helical, in particular with step grinding on both end faces, and the rake face contour is substantially parallel to the circumferential direction on both end faces.

7. The method according to any one of claims 1 to 6, wherein the method is a hard peeling and is carried out as a single flank method.

8. A tool for producing or machining at least one gear toothing on at least two workpieces by hob peeling, hard peeling or gear forming, the tool being toothed and designed as a peeling wheel or forming wheel having cutting edges (11, 12) on a first end face (10) along first and second tooth flanks of the tool teeth (4), 1. A tool characterized in that the contour (P) of the cutting edge (11) of the first tooth flank (5) at the first end face is formed asymmetrically with respect to the contour (Q) of the cutting edge (12) of the second tooth flank (6) at the first end face, and that cutting edges (21, 22) are similarly formed on a second end face (20) of the tool opposite the first end face, wherein at the second end face, the contour (Q) of the cutting edge (21) of the first tooth flank is identical to the contour (Q) of the cutting edge of the second tooth flank (12) at the first end face, and the contour (P) of the cutting edge (22) of the second tooth flank is identical to the contour (P) of the cutting edge of the first tooth flank (11) at the first end face.

9. 9. The tool of claim 8, wherein the teeth are straight.

10. 9. The tool according to claim 8, which is helical, in particular with step grinding on both end faces, and the rake face contour is substantially parallel in the circumferential direction on both end faces.

11. 11. A method for generating a tool designed according to any one of claims 8 to 10, wherein in one method step a basic gear toothing is generated on the tool, which is still in line with the final tool geometry, and in a subsequent machining step an asymmetric cutting edge contour is formed on one end face and an inverted asymmetric machining contour is formed on the other end face.

12. 11. A gear cutting machine comprising at least one workpiece spindle and at least one tool spindle for receiving a gear cutting tool according to any one of claims 8 to 10, and a control device designed to perform gear machining according to any one of claims 1 to 7.

13. A control program which, when executed on a control device of a gear cutting machine, controls the gear cutting machine to perform the method according to any one of claims 1 to 7.

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