Method for machining and generating toothed portions in a workpiece - Patent Application 20070122997

Abstract

The present invention relates to a method for machining or producing a toothed portion (2) on a workpiece by means of a tool toothed portion (4), wherein the tool toothed portion is brought into first machining engagement with a rotating workpiece toothed portion clamped in a clamping mechanism such that there is a rolling engagement that assigns the teeth of the tool toothed portion to the tooth spaces of the workpiece toothed portion, and the tool toothed portion is brought into second machining engagement that is phase-shifted by at least one-quarter of a pitch compared to the rolling engagement of the first machining engagement at the machining distance of its deepest advance, and the second machining engagement has an increased machining distance from the workpiece toothed portion clamped in the same clamping mechanism of the first machining engagement compared to the deepest advance of the first machining engagement. The present invention also relates to a control program having control instructions that, when executed on a controller of the gear cutting machine, cause the gear cutting machine to perform the method. The present invention also relates to a gear cutting machine therefor.

Description

[Technical Field]

[0001] The present invention relates to a method for machining or producing a toothed portion in a workpiece by means of a tool toothing, whereby the tool toothing is brought into first machining engagement with a rotating workpiece toothing clamped in a clamping mechanism such that there is a gear connection that assigns the teeth of the tool toothing to the tooth spaces of the workpiece toothed portion. [Background technology]

[0002] Such gear machining is, of course, well known and is carried out, for example, in the form of gear hobbing, gear shaping, or gear skiving. In gear coupling, the tool teeth are assigned to the tooth spaces of the workpiece toothing, so that the tooth tips of the tool teeth act on the foot area of ​​the workpiece toothing and shape it as required, while the tooth tips of the workpiece toothing are located in the foot area of ​​the tool toothing and can be influenced by its shaping. In this way, for example, the height of the tooth tips can be set on the workpiece, unless this is done using a separate tool such as a roller.

[0003] The invention is based on the object of improving a method of the above type with regard to an advantageous combination of as simple a method design as possible and sufficient accuracy for subsequent further processing. Summary of the Invention

[0004] This object is achieved, in terms of process engineering, by a further development of a method of the type mentioned at the outset, which method is essentially characterized in that the tool toothing is brought into the second machining engagement phase-shifted by at least one-quarter of a pitch compared to such an allocation of the gear linkage of the first machining engagement, in particular in the machining distance of the deepest advance, and that the second machining engagement has an increased machining distance from the workpiece toothing clamped in the same clamping mechanism of the first machining engagement compared to the deepest advance of the first machining engagement.

[0005] Therefore, according to the present invention, machining the workpiece toothing in a phase-shifted manner compared to a conventional gear coupling allows, for example, tooth machining of the tip of the workpiece toothing independently of the shaping of the tool toothing foot area, increasing flexibility in this respect and simplifying the method by eliminating additional tools. Nevertheless, it was recognized that this allows the reference rotation axis of the gear generation / machining and the machining surface of the second machining engagement to remain the same by coupling the machining engagement via the same workpiece clamping mechanism. In this way, for example, the tooth tip diameter can be used as a positioning surface for a gripper or when clamping for subsequent additional machining without positioning or clamping errors caused by different rotation axis references of the positioning surface relative to the rotation axis reference of the workpiece toothing. This allows the synchronization of the rotation axis of the gear coupling of the first machining engagement to be maintained.

[0006] In a preferred embodiment, as described above, the second machining engagement causes the tips of the workpiece teeth to be machined by the tips of the tool teeth, with a phase shift within about half the pitch corresponding to the circumferential extent of the workpiece teeth.

[0007] In this connection, it is provided that the machining area of ​​the second machining engagement covers different phase shifts, which on the one hand allows machining of workpiece tooth tips with asymmetric workpiece designs and on the other hand increases the flexibility and / or precision of the method.

[0008] In a preferred form of the method, the tip diameter of the workpiece toothing is determined by the contact line of the second machining engagement. Therefore, the method is used to selectively set the tip diameter, not (only) to shape it. However, these are also contemplated. For example, tip phasing can be generated using the method according to the invention by superimposing a radial (x) machine axis movement in addition to an axial (z) machine axis movement on a phase-shifted gear connection.

[0009] In a particularly preferred embodiment, the deviation of the tip diameter of the workpiece toothing from the average value of the tip diameters taken over a workpiece tooth is less than 200 μm, preferably less than 80 μm, in particular less than 20 μm. If necessary, for this purpose, a different phase shift is used during the second machining engagement, so that the tip diameter is obtained via the encirclement of the contact lines for the part machining operations that are phase-shifted relative to each other.

[0010] In a particularly preferred embodiment, the method is carried out in a feed motion of the second machining engagement, the main motion component of which is directed along the workpiece rotation axis (Z), so that the above-mentioned effects can be extended, for example, over the entire face width or, if desired, only over a portion thereof.

[0011] In a similarly preferred embodiment, a continuous phase shift, particularly an oscillating phase shift, is used in the second machining engagement. The tips of the workpiece teeth are then machined, figuratively speaking, once from the right side to the left side and once from the left side to the right side at different heights across the tooth width. It is understood that the feed motion must be adjusted for this purpose.

[0012] In the method, preferably the ratio of the vibration frequency of the phase shift to the workpiece speed is given by (2k+1) / (2m), where m is greater than 2 and preferably less than 10, in particular less than 7, preferably less than or equal to 4, and k is greater than or equal to 0, preferably less than 10, in particular less than 7, and preferably k and / or m are integers.

[0013] In a preferred embodiment, the first machining engagement is a gear or hard skiving engagement, particularly a skiving wheel ground by step grinding. The flexibility of the present invention is particularly useful for this machining operation. Preferably, the first and second machining operations are performed at the same cross-axis angle.

[0014] In a preferred embodiment, the phase shift is formed by an additional rotation of the workpiece tooth and / or the tool tooth, in particular by an additional rotation of the workpiece tooth. However, a tangential linear machine axis can also be used to achieve the phase shift position. However, it is preferred that the tangential axis is the same as in the first machining.

[0015] Therefore, with regard to the surface formed in the second machining engagement and its suitability as a grippable and / or position-determining surface, the invention also relates to a method for machining or generating a toothing on a workpiece by means of a tool toothing, wherein the tool toothing is brought into first machining engagement with a workpiece toothing rotating in a clamped set-up under a gear coupling that assigns the teeth of the tool toothing to the tooth spaces of the workpiece toothing, in particular according to one of the above-mentioned aspects, and wherein an optionally discontinuous surface, distinct from the foot region of the workpiece tooth, which serves as a grippable and / or position-determining surface and which is substantially annular in a cross section perpendicular to the workpiece rotation axis, is generated by the tip region of the tool toothing by removing material by cutting on a workpiece clamped in the same clamped set-up.

[0016] Furthermore, the invention also relates to a control program comprising control instructions defined according to the method aspects defined above, and also to a gear cutting machine capable of carrying out such a method by means of corresponding control instructions. [Brief explanation of the drawings]

[0017] Further features, details and advantages of the invention can be found in the following description, taken in conjunction with the accompanying drawings.

[0018] [Figure 1] The relative positions of the workpiece and the tool teeth are shown. [Figure 2] 10 illustrates another relative position of the workpiece and the tool tooth. [Figure 3] A more detailed view of the tooth tip is shown. [Figure 4] The contact lines of different phase shifts are shown. [Figure 5] The contact lines of different phase shifts are shown. [Figure 6] 1 shows a diagram of the contact line with feed motion. [Figure 7] 1 shows another view of the contact line with feed motion. [Figure 8] 1 shows a skiving wheel with step grinding. DETAILED DESCRIPTION OF THE INVENTION

[0019] Figure 1 shows a workpiece toothing, in this case an internal toothing, which is indicated at 2. The tool toothing 4 is shown in a position which substantially corresponds to the deepest advance position with respect to the gear engagement of the machining method for producing the toothing 2 (a very short contact line 3 is at the tooth foot of the workpiece toothing 2 at the deepest advance). The phase position shown in Figure 1 therefore corresponds, for example, to a situation where, after formation of the workpiece toothing 2, the tool has retracted radially from the workpiece while the gear engagement is maintained.

[0020] Typically, in conventional machining methods, this is the end of machining (in continuous roll machining methods, all tooth spaces of the workpiece toothing are formed simultaneously), and the workpiece is unclamped and, if necessary, transferred to another machining station, for example for a tooth flank chamfering step.

[0021] In contrast to this, however, another machining operation is performed in a machining engagement in which one of the tooth tips of the workpiece toothing 2 is phase-shifted relative to the gear combination of the first machining engagement. As can be seen from FIGS. 1 and 2, the phase shift here is half a pitch. As a result, the tip of the tool tooth 4 comes into machining contact with the tip of the tooth of the workpiece toothing 2. The area enclosed by the ellipse in FIG. 2 is again shown in another enlarged view in FIG. 3, where the contact line 3 of the machining engagement can be seen, which continues to occur in the first machining, here, for example, in the machining mode of gear skiving. (The contact line 3 arises from this profile, which is not a one-to-one impression of the cutting tooth 4 profile, but rather an envelope of the machining position of the tool tooth in the adopted machine axis kinematics of gear skiving.)

[0022] 1-3 thus illustrate the principle of the phase shift used for the second machining engagement, but preferably several different phase shifts are superimposed to achieve more accurate tip machining of the workpiece toothing 2. These effects are illustrated in FIGS. 4 and 5. FIG. 4 shows two contact lines 3a, 3b with different phase shifts. Compared to FIG. 3, it is clearly visible that the tooth tip surface formed by such contact lines (indicated by arrows, 36 μm in this example) is more uniform, which is even more pronounced in the view of FIG. 5. In FIG. 5, three contact lines 3a, 3b, 3c are depicted, each with a different phase shift between them, such that the deviation (approximately 6 μm) from the illustrated target tooth tip surface is barely visible to the naked eye.

[0023] Thus, by further advancing in the radial direction X using the described method, the tip diameter of the workpiece teeth can be set, followed or designed according to its own requirements.

[0024] If the toothing is already pre-toothed before the first machining engagement of the gear machining operation itself, the second machining engagement can also be performed temporally before the first machining engagement. Thus, the terms "first" and "second" should not be understood as a temporal order, although such a temporal order is a preferred embodiment.

[0025] The engagement by the contact line described in Figures 1 to 5 is shown only in planar cross section relative to the workpiece rotation axis, and this illustration is supplemented by the illustrations in Figures 6 and 7. In this exemplary embodiment, the second machining engagement is carried out over the entire face width of the workpiece toothing 2, so that the axial feed V in the direction of the workpiece rotation axis Z is z Figure 6 shows the contact line in the radial-axial plane X, Z, considering a feed of 1 mm (per workpiece revolution) in Figure 6, which still leads to a deviation of 35 μm compared to the radial reference in this example, while (Figure 7) halving the feed rate already reduces this deviation to 9 μm in this exemplary embodiment.

[0026] It will be understood that the numerical values ​​used herein are for illustrative purposes only and that feed rates may vary, particularly within the preferred ranges set forth above.

[0027] Similarly, with reference to Figures 4 and 5, it will be appreciated that the phase shift does not have to be set abruptly to a discrete phase shift value, but can be set to successively increase the phase shift to cover the entire tip surface of the workpiece toothing 2 in order to establish machining contact between the workpiece tip and the tool toothing after a single phase shift of the correct magnitude.

[0028] For example, Figure 5 shows a division with contact lines 3a, 3b, 3c with different phase shifts (but always within the range of half a pitch in the deepest advance compared to the first machining), which contact lines are located together at the same tooth height in terms of the face width and are guided by axial feed over the entire face width, but in comparison with this division, for example with axial feed as explained with reference to Figure 7, it is understood that contact line 3c from Figure 5 can extend over the entire face width with axial feed, followed by contact line 3b and finally contact line 3a, or a different sequence or mixture of these two variants.

[0029] Preferably, when the machining engagement is a gear skiving or hard skiving engagement, a tool 40 whose cutting surface 5 is ground with a stepped grind, as shown in Figure 8, is used for the machining operation. This tool forms and / or machines the workpiece toothing 2 by tooth flank machining and also machines its tip or tip surface, thereby in particular setting the tip diameter of the workpiece toothing 2.

[0030] The surfaces thus formed in the form of the tooth tips of the workpiece teeth 2 can also be used as positioning or gripping surfaces for grippers of an automated system or clamping device. As both the teeth themselves and the tooth tip surfaces are machined in the same workpiece clamping mechanism with the same rolling machining engagement, precise clamping for subsequent machining steps is facilitated.

[0031] The invention is not limited to the individual features of the exemplary embodiments, but rather the features of the above description and the following claims may be important both individually and in combination for realizing the invention in its different embodiments.

Claims

1. 1. A method for machining or generating toothing (2) on a workpiece by means of a tool toothing, the tool toothing being brought into first machining engagement with a rotating workpiece toothing clamped in a clamping mechanism such that there is a gear connection that assigns the teeth (4) of the tool toothing to the tooth spaces of the workpiece toothing, The method of claim 1, wherein the tool toothing is brought to a second machining engagement that is phase-shifted circumferentially of the workpiece toothing by at least one-quarter of the pitch of the workpiece toothing compared to such an allocation of the gear combination of the first machining engagement, and the second machining engagement is at an increased distance from the workpiece toothing clamped in the same clamping mechanism of the first machining engagement compared to the first machining engagement.

2. The method of claim 1 , wherein the second machining engagement causes the tips of the workpiece teeth to be machined by the tips of the tool teeth.

3. The method of claim 1 or 2, wherein the machining areas of the second machining engagement encompass different phase shifts.

4. The method according to any one of claims 1 to 3, wherein the tip diameter of the workpiece toothing is determined by the contact line of the second machining engagement.

5. 5. The method according to claim 4, wherein the deviation of the tip diameter of the workpiece toothing from the average value of the tip diameters taken over the workpiece toothing is less than 200 μm, preferably less than 80 μm, in particular less than 20 μm.

6. The method of any one of claims 1 to 5, including a feed motion of the second machining engagement, the main motion component of the feed motion being directed along a workpiece rotation axis.

7. The method according to any one of claims 1 to 6, wherein the first machining engagement is a gear skiving or hard skiving machining engagement.

8. 8. The method according to claim 7, wherein the tool tooth is a skiving wheel having a cutting surface ground with a stepped grind.

9. 9. The method according to claim 1, wherein the phase shift is generated by an additional rotation of the workpiece and / or tool toothing relative to the rotation in the second machining engagement, in particular by an additional rotation of the workpiece toothing.

10. 10. A method for machining or generating teeth on a workpiece by means of a tool toothing, in particular according to the method of claims 1 to 9, comprising a feed movement of the second machining engagement, the main motion component of which is directed along the workpiece rotation axis, the tool toothing being brought into first machining engagement with the workpiece toothing rotating in a clamping mechanism under a gear connection which assigns the teeth of the tool toothing to the tooth spaces of the workpiece toothing, and by removal of material by cutting of the workpiece clamped in the same clamping mechanism an optional discontinuous surface is generated in the tip region of the tool toothing, which optional discontinuous surface is different from the foot region of the workpiece toothing and serves as a grippable and / or positioning determining surface and is substantially annular in a cross section perpendicular to the workpiece rotation axis.

11. A control program including control instructions which, when executed in a controller of a gear cutting machine, cause the machine to perform a method according to any one of claims 1 to 10.

12. 11. A gear cutting machine comprising: a workpiece spindle for clamping a rotationally drivable workpiece; a tool spindle for driving a tool toothing in the rotational direction; at least one, in particular a plurality of positioning and / or setting axes for positioning a tool rotation axis relative to the workpiece rotation axis; and a control device controlled by control commands for carrying out the method according to any one of claims 1 to 10.

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