Gear processing by hob peeling, hard peeling or gear shaping, and corresponding gear cutting machine

Abstract

The invention relates to a method for generating or processing at least one gear toothing on at least two workpieces by hob peeling, hard peeling or gear shaping, with a toothed tool in the form of a peeling wheel or shaping wheel which on a first end face has a cutting edge along a first tooth flank and along a second tooth flank of a tool tooth, wherein the profile of the cutting edge on the first tooth flank on the first end face is formed asymmetrically with respect to the profile of the cutting edge on the second tooth flank on the first end face, and the gear processing of one of the at least two workpieces is carried out with the cutting edges of the first end face, and cutting edges are likewise formed on the second end face of the tool opposite the first end face and carry out the gear processing of another of the at least two workpieces, wherein on the second end face the profile of the cutting edge on the first tooth flank is identical to the profile of the cutting edge on the second tooth flank on the first end face and the profile of the cutting edge on the second tooth flank is identical to the profile of the cutting edge on the first tooth flank on the first end face.

Description

[0001] GEAR MACHINING BY POWER SKEWING, HARD SKEWING OR

[0002] Gear shaping and corresponding gear cutting tools

[0003] The invention relates to a method of producing or machining at least one toothing on at least two workpieces by skiving, hard skiving or gear shaping, with a toothed tool in the form of a skiving wheel or shaping wheel, which has a cutting edge along a first and along a second tooth flank of a tool tooth on a first end face,

[0004] All three of these processes are well known in gear cutting technology. Gear skiving and shaping are soft machining processes, while hard skiving is a hard finishing process of previously cut, hardened gears, carried out using the kinematics of gear skiving. Furthermore, all three processes involve tools (shaping wheels or skiving wheels) with geometrically defined cutting edges. When machining multiple workpieces, and especially larger workpiece batches of more than 40, especially more than 100, or even several hundred, the cutting edges wear down through continuous machining. To counteract this, the tools are resharpened from time to time. For example, it is common practice to resharpen them outside of the machine and then recoat them. DE 10 2017 011 978 A1 describes how and why resharpening can also be performed on the gear cutting machine itself.DE 102021 108 379 A1 addresses disposable skiving tools that are no longer used after reaching their wear limit. These are designed as straight teeth with a symmetrical profile, and the basic shape of the tool is that of a cylindrical disk. DE 10 2017 114088 A1 also discloses symmetrical tools. DE 10 2014 008 475 A1 discloses the use of the back of a skiving wheel as a tool for removing burrs. DE 10 2012 012 617 A1 discloses an infeed strategy in which reduced tool wear is achieved by avoiding predominantly U-shaped chips.

[0005] The invention is based on the object of improving methods of the type mentioned above with regard to a favorable combination of flexibility with regard to feed strategy and tool design, satisfactory tool service life and high machining accuracy.

[0006] This object is achieved in terms of process technology by a further development of the method of the type mentioned at the outset, which is essentially characterized in that the profile of the cutting edge on the first tooth flank on the first end face is formed asymmetrically to the profile of the cutting edge on the second tooth flank on the first end face and the gear machining of one of the at least two workpieces is carried out with the cutting edges of the first end face, and that on the first

[0007] Cutting edges are also formed on the second end face of the tool opposite the end face, with which the gear machining of another of the at least two workpieces takes place, wherein on the second end face the profile of the cutting edge on the first tooth flank is equal to the profile of the cutting edge on the second tooth flank on the first end face and the profile of the cutting edge on the second tooth flank is equal to the profile of the cutting edge on the first tooth flank on the first end face.

[0008] The method according to the invention achieves, on the one hand, a comparatively high machining accuracy and satisfactorily simple machining, since minimal deviations in the machining result that would otherwise result from the machining position of the trailing and leading flanks are compensated for by an asymmetry of the cutting edge profiles on one end face, whereas the back of the tool can also be used for machining workpieces of the workpiece batch without having to calculate and set new machining and engagement positions due to the profile asymmetry, and this regardless of, for example, the helix angle (ß>0) of the tool toothing.

[0009] In a preferred method variant, the sign of the scalar product of the external normal to the first end face with the workpiece rotation axis during gear cutting of the first workpiece is the same as the sign of the scalar product of the external normal to the second end face with the workpiece rotation axis during machining of the second workpiece. In one possible variant, this could be achieved by reclamping the tool with regard to its orientation on the tool spindle. In another variant, this could be achieved by using the movement axes of a gear cutting machine. In this context, gear cutting machines are preferably considered which have three linear movement axes and at least one pivot axis, wherein the pivotability of a tool spindle carrying the tool exceeds 180°, preferably exceeds 210°, in particular exceeds 240°.

[0010] In a further preferred embodiment, it is provided that the base circle of the tool toothing on its left flank differs from that on its right flank.

[0011] In this context, it is particularly preferred that the base circle diameter difference be greater than 0.03 mm, preferably than 0.04 mm, in particular than 0.05 mm, and more preferably less than 0.8 mm, more preferably than 0.7 mm, in particular than 0.6 mm. This provides particularly precise machining results.

[0012] Furthermore, it is preferred that the base circle diameter for the right flank of the tool toothing is larger than that for the left flank of the tool toothing when a left-hand helical toothing is being produced or machined, and vice versa for the production / machining of a right-hand helical toothing. Preferably, work is carried out with an axis crossing angle of greater than 5°, in particular greater than 10°, and more preferably not greater than 40°, in particular not greater than 35°. Furthermore, it is preferred that the normal module of the tool is greater than 0.4 mm, more preferably than 0.6 mm, and in particular not greater than 4 mm, more preferably not greater than 3.5 mm. This delivers particularly precise machining results.

[0013] In one possible design, the tool has straight teeth. However, such a tool cannot be used to produce straight-toothed workpieces using the power skiving process. In a similarly preferred variant, the tool is therefore helical, with a step-grind on both faces, and the rake face profile is essentially parallel in the circumferential direction on both faces.

[0014] For example, a hard metal (HM) is used for the tool. Versions with tools manufactured using powder metallurgy (high-speed steel HSS, PM-HSS) are also being considered.

[0015] To save material or to avoid collisions with interfering contours, the width of the tool toothing (tool dimension axial to the tool rotation axis) can be small, approximately less than 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 toothing width of the tool toothing be at least 4 mm. The tool can have a coating that is more wear-resistant than its base material; in this regard, DE 10 2017 011 978 A1 is incorporated by reference. The tool can be designed as a disposable tool.

[0016] In addition to a cylindrical basic shape for the straight-shaped gear cutting tool, a double-cone shape can also be considered, in which the outer diameter is the same on both end faces, but tapers towards the axial tool center (where the axial tool center is the center between the two end faces).

[0017] In the gear shaping variant, it is understood that a change in clamping is required for the use of the second tool face. In the case of hard skiving, in addition to double-flank machining, a process in which only one flank side of the workpiece gear is machined at a time, i.e., the single-flank process, is also preferred. The teeth of a tool prepared for this purpose are thinner in the circumferential direction to ensure contact-free contact on the opposing flank while maintaining profile asymmetry.From a tool technology perspective, the invention provides a tool for producing or machining at least one toothing on at least two workpieces by gear skiving, hard skiving or gear shaping, which is essentially characterized in that the profile of the cutting edge on the first tooth flank on the first end face is formed asymmetrically to the profile of the cutting edge on the second tooth flank on the first end face and that cutting edges are also formed on the second end face of the tool opposite the first end face, wherein on the second end face the profile of the cutting edge on the first tooth flank is equal to the profile of the cutting edge on the second tooth flank on the first end face and the profile of the cutting edge on the second tooth flank is equal to the profile of the cutting edge on the first tooth flank on the first end face.

[0018] The advantages of the tool according to the invention result from the above description of the method according to the invention, which is preferably carried out in the variant of gear skiving (soft machining).

[0019] The invention also provides a method for producing such a tool. For this purpose, it is preferably provided that, in one process step, a basic toothing is created on the tool, which still has an allowance compared to the final tool geometry, and in a subsequent machining step, the asymmetric cutting edge profile is formed on one end face and the inversely asymmetric machining profile is formed on the other end face.

[0020] Furthermore, the invention also provides a gear cutting machine suitable and controlled for carrying out the method according to the invention, as well as a corresponding control program.

[0021] Further features, details and advantages of the invention will become apparent from the following description with reference to the accompanying figures, of which

[0022] Fig. 1 shows a peeling wheel in a perspective view,

[0023] Fig. 2 shows an enlarged view of a skiving wheel tooth with a schematically shown (exaggerated) asymmetrical profile,

[0024] Fig. 3 shows a variant of a double cone-shaped design, Fig. 4 shows a variant with double step grinding, and

[0025] Figures 5A, 5B show machining operations.

[0026] The skiving wheel 100 shown in Fig. 1 has a radially central through-opening 3 which can be used in a manner known to those skilled in the art for clamping the skiving wheel 100 on a tool spindle (not shown) of a gear cutting machine, and a plurality of teeth 4 radially outwardly. In this embodiment, the skiving wheel 100 is fully toothed, ie there is a tooth 4 at each pitch. In other embodiments, teeth could be omitted, ie not every pitch is occupied by a tooth 4.

[0027] The skiving wheel 100 has cutting edges 11, 12 on its first end face 10, wherein a first cutting edge 11 is formed on the edge between the first end face 10 and a first tooth flank 5, and a second tooth edge 12 is formed on the edge between the first end face 10 and the second tooth flank 6 of a tool tooth 4. On its opposite second end face 20, the skiving wheel 100 also has cutting edges, namely cutting edges 21 and 22. The cutting edge 21 is formed on the edge between the second end face 20 and the first tooth flank 5, the other tooth edge 22 is formed on the edge between the second end face 20 and the second tooth flank 6 of a skiving wheel tooth 4.

[0028] An asymmetry provided according to the invention between the cutting edges 11, 12 on the first end face 10 and 22, 21 on the second end face 20 is not yet visible from Fig. 1. Moreover, the asymmetry is so slight that it would not actually be visible to the naked eye, even in an enlarged view such as in Fig. 2, and therefore a schematic asymmetry is shown to be significantly exaggerated in the profiles P, Q of the cutting edges in Fig. 2. It can be seen from Fig. 2 on the first end face 10 how the profile P on the cutting edge on the first tooth flank 5 differs from the profile Q on the cutting edge on the second tooth flank 6. On the opposite end face 20, this same asymmetry is provided in reverse, so that there the profile P is present at the cutting edge with the second tooth flank 6 and the profile Q is present at the cutting edge with the first tooth flank 5.If only one tooth flank is considered, analogous to the terminology used for toothed workpieces, an interlacing of the tooth flank results when viewed at its end faces. Fig. 5A shows the machining of a first workpiece toothing 201 by the skiving wheel 100. The typical axial cross angle Z between the rotational axes ω2 of a workpiece toothing 201 and ω1 of the tool can be seen. The machining of the toothing 201 is carried out with the cutting edges on the first end face 10 of the skiving wheel 100, the scalar product of its outer normal vector n. 10and the workpiece rotation axis is negative in the illustration shown. The illustration in Fig. 5B shows the machining engagement for producing an identical toothing 202, albeit on a different workpiece. Here, the cutting edges intersect on the second face 20, whose outer normal vector also forms a negative scalar product with the rotation axis ω2 of the toothing 202. To produce the machining positions shown in Figs. 5A and 5B, the skiving wheel 100 could be changed in its clamping orientation.However, without changing the clamping, a swivel axis of a gear cutting machine carrying out the machining, which is also intended for setting the axis crossing angle Z, for example, could be swiveled by 180°, and the machining position could be adjusted by linear axis adjustments, for example by superimposing a linear axis movement running along the workpiece rotation axis and a tangential axis movement (positioning axes) running orthogonal to this and a radial axis.

[0029] In one embodiment, a larger batch of workpieces with identical gears 201, 202 is machined. For this purpose, a first number of workpieces is machined, as shown in Fig. 5A, and subsequently a second number of workpieces is machined, as shown in Fig. 5B. Only then is the skiving wheel 100 replaced and, if necessary, resharpened on both its end faces. If a cylindrical skiving wheel is used, as shown in Fig. 1, the

[0030] Machining is preferably off-center, i.e., with an offset as shown in Fig. 5. The axis intersection point X and the machining point BP are separated to provide a kinematic clearance angle. If a double-conical configuration is used instead of a cylindrical configuration, as shown in Fig. 3, machining can also be performed at the axis intersection point, since constructive clearance angles are available. Shown in Fig.

[0031] 3 is the course of the outer diameter D, as it changes in a double cone shape over the width B of the skiving wheel 100.

[0032] If straight-toothed workpiece gears are to be produced or machined, a straight-toothed tool as shown in Fig. 1 is no longer used, but rather a helical-toothed skiving wheel. In this case, it is preferred that the skiving wheel be ground in a step-grind pattern on both faces, with the step-grinding direction running parallel in the circumferential direction on the upper and lower faces (Fig. 4).

[0033] In a first embodiment, a workpiece toothing 201 / 202 is produced with the following parameters: Number of teeth: 85, helix angle = 0. For this purpose, a skiving wheel with an asymmetry of the profiles P, Q with a difference AP-Q of approximately 0.59 mm expressed as a base circle diameter difference is used at an axis cross angle of Z = 20°, where Q is the profile of the flank running in during machining and P is the profile of the flank running out during machining. The other parameters of the tool are normal module m n-2.97, helix angle 20°, pressure angle 25° and number of teeth 51.

[0034] In a further second embodiment, a right-hand helical workpiece with a helix angle of 14° and a number of 84 teeth is manufactured using a helical tool with a helix angle of 6° and an axis intersection angle of 20°. The skiving wheel has a module of 2.0, a pressure angle of 20°, and 50 teeth. The asymmetry, expressed as a base circle diameter difference, is 0.055 mm.

[0035] In yet another third embodiment, a straight toothing is again produced, this time with 52 teeth, but this time at an axis intersection angle of 15°. A skiving wheel with a module of 0.75 and a helix angle of 15° is used, with a pressure angle of 30° and 39 teeth. The asymmetry between the right and left flanks of the workpiece toothing, expressed as the base circle diameter difference, is 0.11 mm.

[0036] In yet another fourth embodiment, a left-hand helical gear with 59 teeth is produced. In this case, the base circle diameter on the left tool flank is larger than on the right tool flank, with a difference of 0.15 mm. The remaining tool data are module 1.3, pressure angle 20°, and the spur-toothed skiving wheel has 80 teeth.

[0037] On the opposite end face of the exemplary cutters, the asymmetry regarding the left and right flanks is reversed.

[0038] The invention is not limited to the specific embodiments and examples mentioned above. Rather, the features of the above description and the following claims, individually and in combination, may be essential for the realization of the invention in its various embodiments.

Claims

A n s p r ü c h e 1. A method of producing or machining at least one toothing (201; 202) on at least two workpieces by skiving, hard skiving or gear shaping, with a toothed tool (100) in the form of a skiving wheel or shaping wheel, which has a cutting edge (11, 12) along a first and a second tooth flank of a tool tooth (4) on a first end face (10), characterized in that the profile (P) of the cutting edge (11) on the first tooth flank (5) on the first end face is formed asymmetrically to the profile (Q) of the cutting edge (12) on the second tooth flank (6) on the first end face and the gear machining of one of the at least two workpieces takes place with the cutting edges of the first end face, and that on the second end face (20) of the tool opposite the first end face, cutting edges (21, 22) are also formed, with which the gear machining of another of the at least two workpieces is carried out,wherein on the second end face, the profile (Q) of the cutting edge (21) on the first tooth flank is equal to the profile (Q) of the cutting edge on the second tooth flank (12) on the first end face, and the profile (P) of the cutting edge (22) on the second tooth flank is equal to the profile (P) of the cutting edge on the first tooth flank (11) on the first end face.

2. Method according to claim 1, wherein the sign of the scalar product of the external normal (nw) to the first end face with the workpiece rotation axis (W2) during gear machining of the first workpiece is equal to the sign of the scalar product of the external normal (nao) to the second end face with the workpiece rotation axis (W2) during machining of the second workpiece.

3. Method according to claim 1 or 2, wherein the asymmetry (P<->Q) of the cutting edge profiles increases with respect to a symmetrical reference profile from the tooth tip to the tooth root.

4. Method according to one of the preceding claims, in which the base circle of the tool toothing on its left flank differs from that on its right flank.

5. Method according to one of the preceding claims, wherein the tool has straight teeth.

6. Method according to one of claims 1 to 4, in which the tool is helically toothed, with a step grind being present in particular on both end faces, and the rake surface profile in the circumferential direction on both end faces is substantially parallel.

7. A method according to any one of the preceding claims, wherein the method is hard-peeling carried out as a single-flank method.

8. Tool for producing or machining at least one toothing on at least two workpieces by gear skiving, hard skiving or gear shaping, wherein the tool is toothed and acts as a skiving wheel orShaping wheel is formed, which has on a first end face (10) a cutting edge (11, 12) along a first and along a second tooth flank of a tool tooth (4), characterized in that the profile (P) of the cutting edge (11) on the first tooth flank (5) on the first end face is formed asymmetrically to the profile (Q) of the cutting edge (12) on the second tooth flank (6) on the first end face, and that cutting edges (21, 22) are also formed on the second end face (20) of the tool opposite the first end face, wherein on the second end face the profile (Q) of the cutting edge (21) on the first tooth flank is equal to the profile (Q) of the cutting edge on the second tooth flank (12) on the first end face, and the profile (P) of the cutting edge (22) on the second tooth flank is equal to the profile (P) of the cutting edge on the first tooth flank (11). on the first front side.

9. Tool according to claim 8, which is straight-toothed.

10. Tool according to claim 8, which is helical-toothed, wherein in particular on both There is a step grind on the end faces and the rake face is essentially parallel in the circumferential direction on both end faces.

11. A method for producing a tool designed according to one of claims 8 to 10, in which in one method step a basic toothing is produced on the tool, which still has an allowance compared to the final tool geometry, and in a subsequent machining step the asymmetrical cutting edge profile is formed on one end face and the inversely asymmetrical machining profile is formed on the other end face.

12. Gear cutting machine with at least one workpiece spindle and at least one tool spindle for receiving a gear cutting tool according to one of claims 8 to 10 and a control device which is designed to carry out gear cutting according to one of claims 1 to 7.

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

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