METHOD FOR HARD FINE MACHINING OF TWO TOOTHINGS ON A WORKPIECE, AND GEAR CUTTING MACHINE, CONTROL PROGRAM, HARD FINE MACHINING COMBINATION TOOLS AND SENSOR ASSEMBLY THEREFOR

Abstract

A method for hard finishing two different toothings on a workpiece, wherein, prior to each machining process, to set the correct tool engagement position for the machining process, a first relative rotational angle position of a first rotational position reference of the first toothing is determined relative to an axial rotational position of the workpiece spindle holding and clamping the workpiece for the first machining, and a second relative rotational angle position of a second rotational position reference of the second toothing is determined relative to an axial rotational position of a workpiece spindle holding and clamping the workpiece for the second machining, wherein the machining operations are carried out on the same workpiece spindle with no intervening clamping change, and with the first and second rotational position references coupled to each other as the basis thereof.

Claims

1. A method for hard finishing two different toothings (1, 2) provided on a workpiece (4), wherein, prior to each machining process, to set the correct tool engagement for the machining process, a first relative rotational angle position of a first rotational position reference (φ1) of the first toothing (1) is determined relative to an axial rotational position of a workpiece spindle holding and clamping the workpiece clamped for the first machining, and a second relative rotational angle position of a second rotational position reference (φ2) of the second toothing is determined relative to an axial rotational position of a workpiece spindle holding and clamping the workpiece clamped for the second machining, characterized in that the machining operations are carried out on the same workpiece spindle (108; 208) with no intervening clamping change, and with the first and second rotational position references coupled to each other as the basis thereof.

2. The method according to claim 1, wherein the coupling consists of a rotational angle difference (Δφ) between the first and second rotational position references which is within a tolerance (±δΔφ) by a prespecified rotational angle (Δφ.sub.0)

3. The method according to claim 1, wherein the first and second rotational position references are assigned to a prespecified reference comprising a selected reference tooth (21) of a toothing (2).

4. The method according to claim 3, wherein the prespecified selection of the reference tooth is determined by a marking (3) which is arranged on the workpiece itself.

5. The method according to claim 1 wherein, for the first machined workpiece of a batch of identical workpieces, and/or for the first machined workpiece after a replacement or resharpening/profiling of at least one of the tools, the first and/or second relative rotational angle position is/are determined via sensor-detected contact between the workpiece toothing and the tool, and the appropriate axial rotational positions for the tool engagement are determined therefrom.

6. The method according to claim 5, wherein the workpieces following the first machined workpieces are set to the correct axial rotational position for the tool engagement based on the first and/or second relative rotational angle positions determined for this workpiece by means of a contactless sensor.

7. The method according to claim 3 wherein the specified reference comprising the selected reference tooth, is also identified for each workpiece and, for this purpose, the rotational position of the marking is detected by sensors in a contactless manner.

8. The method according to claim 1 wherein the determination of the second relative rotational angle position is carried out before the machining of the first toothing is started, and vice versa.

9. The method according to claim 1 wherein dressing tools (401, 402) for the tools (101, 102), in the form of diamond dressing wheels having toothings, are arranged with a coupling of the rotational positions fixed relative to each other and are also arranged on the same workpiece spindle (108) as the first and second toothings (1, 2).

10. A tooth cutting machine (100; 200) for hard finishing two different toothings (1, 2) provided on a workpiece (4), having at least one workpiece spindle (108; 208) for rotating the workpieces by a drive, a tool head (104; 204) for mounting a first hard finishing tool (101; 201) driven by the same drive for hard finishing the first toothing (1) and a second hard finishing tool (102; 202) for hard finishing the second toothing, at least two, in particular contactless, sensors (110, 120), and a control device (99) with control instructions for executing a method according to claim 1.

11. The tooth cutting machine according to claim 10, having a third sensor (130) for detecting a marking (3) which is arranged on the workpiece and which identifies a reference for one of the rotational position references.

12. The tooth cutting machine according to claim 10 having a resharpening or profiling device (401, 402) for the hard finishing tools coupled in a fixed rotational position to each other, and arranged on the workpiece spindle (108).

13. A control program with control instructions which, when executed in a control device of a tooth cutting machine, controls it to execute a method according to claim 1.

14. A hard finishing combination tool having two toothed hard finishing tools with geometrically undefined cutting edges, in particular in the form of internally toothed honing rings (101, 102) with a shared axis of rotation (C1) and shared coupling via the same rotationally-fixed clamping in a tool head (104), wherein the first hard finishing tool is designed for hard finishing a first toothing of a workpiece, and the second hard finishing tool is designed for hard finishing a second toothing of the workpiece which is different therefrom.

15. A hard finishing combination tool having two hard finishing tools with geometrically determined cutting edges in the form of, in particular, externally toothed skiving wheels (201, 202) for a hard skiving process in a mutually rotationally-fixed position, and coupled with the same axis of rotation, wherein the first hard finishing tool is designed for the hard finishing of a first toothing of a workpiece, and the second hard finishing tool is designed for the hard finishing of a second toothing of the workpiece which is different therefrom.

16. The method of claim 1 including a sensor arrangement for a centering operation during the hard finishing of workpieces (4) with two different toothings, having a first contactless, sensor (110) for detecting a tooth gap of a first of the toothings, a second contactless, sensor (120) detecting a tooth gap of the second toothing, and a third sensor (130) for detecting a marking (3) on the workpiece (4) which serves as a reference for a difference in rotational position references of the first and second toothing.

17. The method according to claim 16, wherein two or three of the sensors are arranged in a defined, fixed positional relationship to each other via their attachment to the same carrier which can be brought into a working position of the sensor in particular via a movement mechanism.

18. The method according to claim 16, wherein two or three of the sensors can be moved in position relative to each other via at least one positioning movement axis.

19. The method of claim 18 wherein one or more sensors are arranged to allow movement via a slide arrangement or a swivel arm.

20. The machine of claim 11 wherein said one of the rotational position references comprises a prespecified tooth of the workpiece.

Description

[0024] Further features, details, and advantages of the invention can be found in the following description with reference to the accompanying drawings, in which

[0025] FIG. 1 is a perspective view of a workpiece with two toothings,

[0026] FIG. 2 is a schematic illustration of rotational position references, in a projection plane to which the workpiece axis is perpendicular,

[0027] FIG. 3 shows the structure of a honing machine with two internally toothed honing rings,

[0028] FIG. 4 is a schematic illustration in which, in addition to the honing rings and the workpiece toothings, sensors and dressing tools are also shown,

[0029] FIG. 5 shows a skiving machine, and

[0030] FIG. 6 shows a hard finishing tool with two hard skiving wheels.

[0031] In FIG. 1, a workpiece 4 is shown in a perspective view. The workpiece 4 is roughed with two toothings, a larger (greater diameter) toothing 1 and a smaller (smaller diameter) toothing 2, which are connected to each other via a shaft and whose axes of rotation are coaxial. The two toothings also form the two axial ends of the workpiece 4. For the hard finishing process, the workpiece 4 is clamped onto a workpiece spindle, the workpiece spindle axis of which runs coaxially with the toothing axes of rotation. The toothing 1 could be produced, for example, by hobbing, and the toothing 2 by shaping or skiving; or other combinations could also have been used. The invention proceeds from the moment of hard finishing.

[0032] This means that the toothings 1 and 2 still have, with respect to their final tooth flank geometry, a machining allowance which was left when the toothings 1, 2 were created; hardening may also result in hardening deformations, and thus slightly changed tooth shapes. With the hard finishing, the remaining machining allowance, along with hardening deformation, should be removed in order to give the toothings 1, 2 their final geometry.

[0033] Also visible in FIG. 1 is a bore 3 formed in the wheel body of the toothing 1. As can be seen better from FIG. 2, the bore 3 serves as a marker for identifying a tooth 21 of the toothing 2, namely for example, a tooth 21 at a rotational position which substantially corresponds to that of the marking 3. The accuracy of the correspondence is not important. An angular offset could be provided, and the tooth of the toothing 2 next to it in the counterclockwise or clockwise direction could be marked as the tooth 21 identified by the marking 3. One could also use the marking 3 to mark a tooth gap 22 or a tooth—for example, tooth 12 of the toothing 1—or a tooth gap of the larger toothing 1.

[0034] Relative to the marking 3—in this case of the tooth center of the tooth 21 of the toothing 2 and of the tooth gap center of the next tooth gap 22—there is an angle of rotation φ2 which, in this case, is determined on the basis of the module of the toothing 2. However, an angle value may not be known in advance if there is a different position of the marking. There is an angle φ1 between the rotational position determined by the marking 3 (and/or its center) and the next tooth gap 12 of the toothing 1 in the clockwise direction, and a relative rotational position of the toothing 1 with respect to the toothing 2 is defined relative to the reference determined by the marking 3 by the rotational angle difference Δφ=φ2−φ1 between the two tooth gap centers 22 and 12. This angular difference Lisp should correspond to a prespecified angular difference Δφ.sub.0 for the workpiece 4 within a very small tolerance ±δΔφ of only 5 angular minutes or less, preferably 1 angular minute or less, in particular 25 angular seconds or less.

[0035] For the following, it is assumed that not only a workpiece 4 of the type shown in FIG. 1 is to be hard finished, but also that a larger workpiece batch of these workpieces 4 is present. This batch has undergone the same production process with regard to the generation of the toothings 1, 2 and the hardening process, but may have slightly different machining allowance distributions due to the manufacturing process, or may have different hardening deformations.

[0036] The workpieces 4 of a workpiece batch are clamped for hard finishing on a workpiece spindle (with the workpiece spindle axis of rotation C2 in the embodiment of FIG. 3), and the hard finishing of the toothing 1 and of the toothing 2 is carried out without an intervening clamping change—that is, in the same clamping on the same workpiece spindle. Furthermore, the hard finishing of the toothing 1 and of the toothing 2 is carried out using the same hard finishing method, which is gear honing (shaving) with internally toothed honing rings in the example of FIG. 3, or hard skiving with externally toothed hard skiving wheels in embodiment 2 (FIG. 5). The hard finishing accordingly preferably takes place in the machining engagement of a helical gear unit with axes of rotation of the machined toothing and the machining tool that are at a cross-axis angle. As for the tool, the relative rotational positions of the two different gear cutting tools (due to the different toothings 1, 2) should also be coupled to each other in a rotationally fixed manner; this may be termed a tandem tool. The workpiece spindle reference is then a specified axis position of the C2 axis.

[0037] The explanations below are based on the embodiment according to FIGS. 3 and 4, in which the toothings 1 and 2 are honed by means of two internally toothed honing rings 101, 102 which are firmly clamped in a honing head 104.

[0038] A more detailed explanation of the tooth honing machine 100 shown in FIG. 3 is omitted, since such designs are already known to the person skilled in the art. It goes without saying that the gear honing machine has a machine bed 180 and the required carriages and machine axes in order to be able to carry out gear honing with internally toothed honing rings. In the embodiment shown in FIG. 3, the axis of rotation C1 of the honing rings 101 and 102 can be set by means of a swivel axis A1 to a cross-axis angle with respect to the workpiece spindle axis C2, which is fixed in terms of its axial position; the machine also has a further swivel angle B1 with a swivel axis which is linearly independent from the swivel axis A1, and which is preferably perpendicular to the swivel axis A1 and the axial direction of the workpiece axis C2. This in turn is parallel to a linear travel axis Z2 of the workpiece spindle. The honing head 104 is attached to a compound slide 161, 162 on the tool, which is displaceable parallel to the workpiece axis (Z1 axis) and radially to the workpiece axis Z2 (through linear axis X1). The B1 axis, which can typically be used for tooth trace modifications or influencing the same, can be used in this case as a further movement axis in order to take into account machining that is eccentric with respect to the axis intersection. Alternatively, an additional linear axis Y1, for example, orthogonal to X1 and Z1, could be provided.

[0039] The workpiece axis of rotation C2 has, as is conventional, a drive and a rotary encoder, by means of which a rotational position of the workpiece spindle (rotational axis reference) relative to a prespecified reference position, such as an internal zero crossing of the workpiece spindle, is known. The tool spindle C1 also has such a rotary encoder.

[0040] If a new workpiece is clamped onto the workpiece spindle to undergo hard finishing, the position of the tooth gaps, for example of the toothing 2, relative to the workpiece spindle reference, is usually unknown after clamping. By means of a preferably contactless sensor (index sensor), for example an inductive sensor, the positions of the tooth gaps relative to the reference of the workpiece spindle can be determined by moving the toothing 2 past the sensor 120 by a few tooth gaps. If the mutual angular position of the workpiece spindle axis and the tool axis of rotation is determined by the initial configuration of the machining engagement of the honing ring 102 with the toothing 2 for the first time (a conventional initial centering operation, for example by lowering the tool into a tooth gap, rotating it into contact with the tooth flank on the left and the tooth flank on the right of the gap while holding the rotational positions upon contact, and calculating by averaging the tooth gap center), the machine controller 99 of the tooth cutting machine 100 knows the rotational position to which the workpiece spindle is to be moved in relation to its own reference in order to be in the correct rotational position for the machining operation. These methods are already well known per se for individual toothings, and can likewise be carried out for the toothing 1 (and its machining engagement with the honing ring 101).

[0041] When machining individual gears of this type, however, it normally does not matter which tooth gap is moved into the machining position. In the present case, however, the relative rotational position of the toothing 1 with respect to the toothing 2, expressed by the rotational angle difference Δφ, should be adhered to within very strict tolerances, with the reference provided by the marking 3. For this purpose, a third sensor, for example also a contactless inductive sensor, is provided in this embodiment, and detects the rotational position of the marking 3 in order to form the basis for the reference for the rotational angle difference Δφ. In these configurations, three contactless sensors 120, 130, 110 are provided which determine the rotational positions of the tooth gaps of the toothing 2, of the marking 3, and of the tooth gaps of the toothing 1. The sensors 110, 120, 130 can be fixed in position via a common support arm 150 (as illustrated), or movably arranged via slides/movable arms and/or combinations thereof. The support arm 150 could also be retractable.

[0042] Since the honing rings 101 and 102 cannot be rotated relative to each other, and the toothing 1 cannot be rotated relative to the toothing 2, all the information is available to allow working within the individual tolerance specified for the individual machining process for the machining work on the toothing 1 by the honing wheel 1—that is, to depart from the rotational position of the tooth gap centers in relation to the workpiece spindle reference in comparison to that of the “master wheel” from the initial setup, for the machining rotational position within the individual tolerances relative to the master wheel—and in this way to ensure that there is in any case enough removable allowance relative to the final tooth flank geometry (such that movements are made proceeding from the manufacturing tolerances of the toothing 1 itself). The same must be done for the toothing 2, and both configurations should preferably be coordinated with each other in advance in such a manner that the rotational position difference Δφ lies within the specified tolerance δΔφ.

[0043] The effects are discussed below using an example that is greatly simplified for explanatory purposes. It goes without saying that the settings for the “master wheel”—that is, a workpiece to be machined first in the workpiece batch and/or the first workpiece of the resumed machining, are configured after re-profiling the honing rings 101, 102 to the appropriate rotational engagement positions while maintaining the angular difference Δφ. If one exaggeratedly assumes that the hardening of the toothing 2 caused a deformation with a tendency to shift the tooth gap centers clockwise, and, for toothing 1, counterclockwise, the controller would make a correction by comparing the relative rotational positions of the first rotational position reference of the toothing 1 to the reference of the workpiece spindle relative to that of the master wheel to determine the appropriate rotational position setting for machining relative to that of the master wheel, ideally to be in the center of the tolerance field for the toothing 1, and, for example, to move −|δφ1|; and, with the same approach, to move+1421 for the toothing 2. However, there would then be a difference for this workpiece in the angle of rotation of the toothing 2 relative to toothing 1 of Δφ*=φ2+|δφ2|−(φ1−|δφ1|)=Δφ+(|δφ1|+|δφ2|), and, where |δφ2|+|δφ1|>δΔφ, this would lead to a workpiece that no longer meets the requirements.

[0044] The coupling of the rotational position references of the toothing 1 and the toothing 2 (with reference to the constellation identified by the marking 3, or otherwise identified) ensures that Δφ* (if theoretically still possible) is always within the tolerance of Δφ.sub.0, and, in addition, the respective individual tolerances are still observed—however, the optimal center of the tolerance field of the individual tolerances of the individual toothings 1, 2, are no longer observed for the individual machining processes of the toothings 1, 2.

[0045] In the conventional provision of such workpieces 4, in which a first toothing is machined by grinding and, after changing the clamping, the other toothing is machined by, for example, honing, or the opposite sequence is used, hard finishing has already taken place and, ignoring the non-implemented identical workpiece clamping, there is no longer any leeway with regard to the tolerance field that could be used to ensure the rotational position difference Δφ lies within the tolerance.

[0046] In the schematic illustration of FIG. 4, the rotational position-coupled honing wheels 101 and 102 in the honing head 104, and the sensors 110, 120 and 130, are shown again. A tailstock center 109 and diamond dressing wheels 401, 402 are also provided on the workpiece spindle 108 for dressing the honing rings 101, 102.

[0047] It goes without saying that the type of marking 3 as a hole in the disk body of the toothing 1, and the sensor-based detection of its rotational position, is only one of several options for determining the reference for the application of the specified rotational angle difference Δφ (if one considers the rotational angle difference between two tooth gaps of the toothing 1 and 2 adjacent in the projection plane at any other point, as a rule this will differ significantly from Δφ.sub.0 due to the different toothing, so the reference determination is favorable in itself).

[0048] For example, one could also think of using the above-described detection of the rotational positions of the tooth gaps of the toothing 1 to reference the workpiece spindle, and of the tooth gaps of the toothing 2 to reference the workpiece spindle, to identify a characteristic pairing of two teeth or tooth gaps of the toothing 1 and toothing 2 which occurs only once, and for this characteristic pairing to determine the angular position difference Δφ′ and to introduce it as a constraint for the setting of the rotational positions for the respective machining operations.

[0049] A second embodiment is shown in FIGS. 5 and 6. The hard skiving machine 200 shown in FIG. 5 has a machine bed 280, on one side of which a workpiece table with a workpiece spindle 270 is arranged. The latter can be equipped with an adapter clamp (not shown) for receiving the workpiece 4 shown in FIG. 1. A tailstock arrangement for the counter mounting point is not shown (similar to the tailstock center 109 of FIG. 4).

[0050] On the tool, a main stand 261 is provided which can be moved along a radial direction X, and on which a vertical carriage 262 can be moved in the Z direction parallel to the workpiece axis. It carries a tangential carriage 263 (Y direction in the rotational position A shown) which is rotatable with the axis of rotation A for setting a cross-axis angle. The hard skiving head is attached to the tangential carriage 263. In FIG. 5, the machine is shown with only one single tool with a hard skiving wheel; however the tandem tool shown in FIG. 6 is preferably used. The machine 200 and its axial machine movements are controlled by a controller 299.

[0051] In this case, the hard finishing is carried out on a hard skiving machine, with the structure of the combination tool, shown only roughly schematically in FIG. 6, consisting of two hard skiving wheels 201 and 202 for hard skiving the toothings 1 and 2. The approach to the determination of the rotational position is as described with reference to the first embodiment; however, the type of hard finishing changes due to machining with a geometrically defined cutting edge. In this case as well, the two hard skiving wheels 201, 202 are rotationally coupled, and the relative rotational position settings of the two hard skiving wheels that are the same on the tool therefore prevail for all workpieces 4 of the batch. In this case as well, although it is not shown, preferably three sensors are provided, for example attached to the tool head via a support structure, for detecting the rotational positions of the first and second rotational position reference, and of the reference (the marking 3).

[0052] However, internally toothed skiving rings—that is, tools which are similar in shape to the honing rings 101, 102, but with a geometrically defined cutting edge—could also be used. Toothing honing with externally toothed wheels, similar to the form of the hard skiving wheels 201, 202 but with a geometrically undefined cutting edge, is also conceivable.

[0053] As can be seen, the invention is not restricted to the details shown in the above embodiments. Rather, the individual features of the following claims and of the above description and the following claims may be essential, individually and in combination, for implementing the invention in its different embodiments.