Method for machining a tooth flank area of a workpiece gear, use of a chamfering tool, control program with control instructions for carrying out the method, and gear cutting machine

Description

[0001] The invention relates to the field of supplementary tooth forming and, more specifically, to a method for machining a tooth edge formed between a tooth flank and a face of a workpiece toothing with a tool toothing, in which the toothings rotate in rolling engagement with one another about their respective tooth rotation axes. Such a method according to the preamble of claim 1 is known from document DE 94 18 253 U.

[0002] Processes for supplementary tooth forming are known; an overview can be found in Thomas Bausch's "Innovative Gear Manufacturing," 3rd edition, on page 304. The starting point for supplementary tooth forming is the gear after its creation, for example, by hobbing, shaping, or skiving. In such machining processes for gear production, so-called primary burrs initially form along the tooth face edge where the cutting edges of the machining tool emerge, as shown, for example, in the Bausch reference in Figure 8.1-1, top center, on page 304. These burrs are sharp-edged and hard; they must be removed to avoid injuries and to improve the gear geometry for the subsequent process. This is usually done using stationary deburring tools, rotating deburring wheels, or filing wheels, usually directly related to the gear production process.

[0003] Such mere removal of the primary burr, for example by turning or, as disclosed in DE 10 2014 018 328, by shearing with the back of a skiving wheel, often does not meet the quality requirements of the tooth edges. For this reason, a chamfer is usually formed on the tooth edges (front edges). In the Bausch reference, the front edge is labeled B in Figure 8.1-1, top left, and is shown in the image, top right, with the chamfer created on it for a straight tooth. The invention relates to such methods in which the tooth edge, in the shape it had after gear production, is removed by material removal, and thus goes beyond the shearing off of primary burrs protruding from the tooth edge, which leaves the shape of the existing tooth edge unchanged.

[0004] A chamfering technique that has long been widespread and is still frequently used is so-called roller deburring or roller deburring. Here, the edges are plastically formed into the chamfer by pressing them with roller deburring wheels. However, the resulting material displacement leads to material accumulations (secondary burrs) on the tooth flanks and end faces, which then have to be removed by suitable means. Such systems are described, for example, in EP 1 279 127 A1.

[0005] While roller press deburring is a very simple process (usually the gear-shaped tools do not even need to be driven in rotation, rather they can be held freely with contact pressure against the workpiece toothing to be chamfered and then run in rolling coupling with the driven workpiece), the secondary burrs created in the process represent a disadvantage of this process. While the secondary burrs on the end faces can be sheared off relatively easily, for example using a deburring tool, the secondary burrs created on the tooth flanks are a problem for any hard fine machining that may take place after the workpieces have been hardened.If these flank-side secondary burrs are to be removed in advance, a further machining pass on the machine producing the gear teeth at the deepest infeed is possible, or the use of special tools, as described in DE 10 2009 018 405 A1.

[0006] WO 2009 / 017248 proposes shifting the emphasis on secondary burr generation away from the tooth flank and toward the face. However, other technical approaches aim to achieve material removal / chamfer formation by cutting rather than pressing, by removing material with a geometrically defined or geometrically undefined cutting edge (DE 10 2016 004 112 A1).

[0007] For cutting chamfering with a geometrically defined cutting edge, variants have become known (EP 1 495 824 A2), in which a machining tool used to chamfer the tooth edges is arranged on the same shaft as a hob used to produce the workpiece toothing, but also separate arrangements (DE 10 2009 019 433 A1), which allow the cut to be made from the inside outwards by pivoting the chamfering tool when machining the front ends on one front side as well as on the other front side.

[0008] DE 10 2013 015 240 A1 discloses so-called "chamfer-cut milling cutters," which resemble hob cutters, but in which the cutting circles of identical profile areas overlap. The profiles are designed in such a way that when a chamfer cutter tooth passes through a tooth gap in the workpiece gearing, the latter is completely chamfered on both flanks of the tooth gap. Another cutting chamfering method, which is even more closely based on hobbing, is described in DE 10 2018 001 477 A1. Here, chamfering is performed using a single-flank method in several cuts as several tool teeth pass through the workpiece tooth gap. For example, for machining a flank, the swivel angle, which swivels the tool rotation axis relative to the horizontal when the workpiece axis is vertical, can even be set to zero.

[0009] Following a similar principle to the "chamfer-cut milling cutter" disclosed in DE 10 2013 015 240 A1, there is also fly-knife-type removal at the tooth edge, used to create a chamfer, e.g., for gear teeth. In this method, rotating fly knives, for example in the form of an end mill, are positioned with their tool rotation axis skewed to the axis of the workpiece toothing such that one tooth flank of the workpiece toothing is machined during a single pass through the machining zone by a cutting process parallel to the final geometry to be created. A second fly-knife tool can be positioned for the other workpiece tooth flank. This is described, for example, in the Bausch reference on page 323.

[0010] Yet another method for cutting chamfering is disclosed in WO 2015 / 014448. This method is based on the gear engagement of skiving with an axis cross angle. An additional tilt of the tool axis compared to the normal position in the skiving process ensures a change in the cutting movement, which then creates the chamfer. The method disclosed in DE 10 2014 218 082 A1 is based on the same principle; a skewed axis configuration is already structurally integrated into the gear cutting machine. In these two chamfering processes, which operate according to the principle of skiving, the cutting mechanism is controlled by the axis cross angle, just as in skiving.

[0011] Another chamfering technique is known from DE 10 2018 108 632, in which a pin cutter is moved along the tooth edge by machine axis movement. This chamfering technique is particularly suitable for front edges that are difficult to reach with chamfer-cut cutters or hob-type tools due to interfering contours on the workpiece.

[0012] The invention is based on the object of developing a method of the type mentioned at the outset with the aim of achieving a good combination of comparative simplicity and satisfactory flexibility in tooth edge machining.

[0013] This object is achieved from a process engineering point of view by a process engineering development which is essentially characterized in that the two gearing rotation axes are essentially parallel to one another and the machining takes place over a plurality of workpiece rotations, wherein a first relative movement parallel to the workpiece rotation axis is carried out between the workpiece toothing and the tool toothing and by a second relative movement which is varied in particular as a function of the movement state of the first relative movement, the position of the envelope curve of the tool tooth rolling positions relative to their engagement position with the tooth flank of the workpiece toothing is shifted in the plane orthogonal to the workpiece rotation axis transversely to the profile of the workpiece toothing.

[0014] In the method according to the invention as claimed in claim 1, cutting is not performed along or parallel to the surface of the new surface shape to be formed, in particular a chamfer, but rather, due to the essentially parallel tooth rotation axes and the displacement of the envelope curve, in slices in planes essentially orthogonal to the workpiece rotation axis. The surface formed in place of the original tooth edge, e.g., a chamfer, is composed of the end regions of the slice-like material removal achieved via the envelope curve, which varies depending on the state of motion of the first relative movement. Depending on the desired lower roughness of, for example, the chamfer surface, the number of cutting operations or workpiece rotations performed during the axial first relative movement can be selected to be correspondingly higher, and thus the number of "slices" can be selected to be higher.This results in material removal from the workpiece tooth flanks. The tooth flanks of the tool toothing act as the chip surfaces for the machining process.

[0015] In a simple design, the first relative movement can be carried out as an axial feed movement with a correspondingly high number of feed steps. In this case, the second relative movement could be oscillating, with the engagement position (zero position) being returned to before each subsequent feed step. However, with a view to faster machining times, it is preferred that the first relative movement is carried out as a continuous feed movement, for example with a linear progression over time, e.g. along a machine axis Z parallel to the workpiece rotation axis C. As the feed Z(t) increases, the tool toothing, viewed with respect to the workpiece rotation axis, comes into increasing overlap with the tooth gap in the area of ​​the machined end face of the workpiece toothing.For example, during machining, the tool toothing plunges into the workpiece toothing to the extent that machining of the tooth edge is desired, creating a chamfer to the chamfer depth. Without the additional shift of the envelope relative to the engagement position of the envelope with the workpiece toothing in rolling coupling, the workpiece toothing and tool toothing could, for example, roll on each other like a gear and mating gear, at least partially or even completely along at least one tooth flank if, according to a preferred embodiment, the profile of the tool toothing is designed as a counter profile to the tooth profile of the workpiece toothing. However, due to the shift of the envelope into the material of the workpiece teeth, the above-described "slice-by-slice" material removal occurs, which initially extends on the face side to the desired extent of the machined area, for example, the chamfer width.By reducing the displacement with increasing feed, the desired chamfer surface can then be created. If the displacement movement is also carried out as a linear displacement over time, essentially planar surface areas can be formed in the example of the generated chamfer surface (or essentially straight profiles as seen in the section along the pitch circle). By deviating or selecting V(Z) as a non-linear value, where V stands for the second relative movement and Z for the first relative movement, almost any desired profile of the machining area and thus, for example, even curved chamfers can be generated.

[0016] In a particularly preferred embodiment, a transverse movement of the workpiece and / or tool gearing running transversely to the center distance axis of the rotation axes contributes to the second relative movement. A displacement in the direction of the center distance axis (radial) is also conceivable, but the aforementioned transverse movements are more suitable, especially for the typical pressure angles of a large number of workpiece gearings. The radial movement can be included, particularly if (as explained later) machining in the root area is also desired.

[0017] In a further preferred embodiment in this context, the transverse movement comprises an additional rotation ΔC of the workpiece gearing. This is easy to implement in terms of control technology and allows the realization of simple machining centers, for example, even without a tangential machine axis. This additional rotation is understood to be an additional rotation that goes beyond any additional rotation that may occur with helical gearing to maintain the rolling coupling.

[0018] In an alternative or additional variant, the transverse movement can comprise a movement of a linear machine axis, the directional component of which predominates orthogonal to the workpiece rotation axis and orthogonal to the center distance axis, the respective directional component along these axes. In a simply designed machine axis configuration, this linear axis could be a tangential axis Y, which extends transversely, in particular orthogonally to the radial axis (X) and an axial axis (parallel to the workpiece axis) Z. Since the effect of the additional rotation ΔC, depending on the tool, also includes a radial component compared to, for example, such a Y component, a combination of these two transverse movement components of additional rotation ΔC on the one hand and linear movement ΔY on the other hand can be used to adjust a variation in the machining across the tooth height of the workpiece gearing.Instead of or together with an additional rotation of the workpiece toothing, an additional rotation ΔB of the tool toothing could also be used.

[0019] The method also provides for the tooth edge in the tooth root of the workpiece toothing to be machined. In particular, it is preferably provided for this purpose that a radial movement of the workpiece and / or tool toothing running in the direction of the center distance axis of the rotational axes contributes to the second relative movement. In a particularly simple design, it is also possible to work with only the radial movement as the second relative movement; however, in the case of creating a chamfer, this would couple the chamfer in the root area with the chamfer shape in the flank area. It is therefore particularly preferably provided that, in addition to the radial movement, a transverse movement is also carried out according to one of the mechanisms described above. The second relative movement is then guided in a form having tangential and radial components.

[0020] In this context, it can also be provided that the shape of the chamfer in the tooth root is determined by adjusting the radial movement depending on the state of motion of the first relative movement, and the shape of the material removal at the tooth edge in the tooth flank area is determined by adjusting the transverse movement depending on the state of motion of the first relative movement and the state of motion of the radial movement. This allows the design of the reworked tooth edge in the flank area to be decoupled from that in the root area. As usual, a chamfer width for the tangential direction Y can be converted from a value related to the flank normal directions via the pressure angle.

[0021] In a further preferred embodiment, the material removal profile in the tooth height direction is determined by superimposing the transverse movement contributions of the additional rotation and the linear machine axis movement. As already indicated above, this achieves greater variability in the design of, for example, a reworked tooth edge, such as a chamfer.

[0022] A further expedient embodiment could be carried out with a further machining pass, in particular with otherwise identical or preferably phase-shifted (e.g. by 180°) coupling of the movements, and preferably with the movement control carried out in the opposite direction of the first relative movement. With such a further machining pass, any chips that have not been completely removed from the material of the remaining workpiece tooth can be sheared off. The displacement or retraction movement is thus preferably used to smooth the surface formed during the plunging. For example, with the same return stroke as the feed per workpiece revolution, the height of the (see later Fig. 2 ) Steps on the chamfer surface are halved, for example, by a phase shift of 180°. If chip removal is required as an alternative or in addition, brushes could also be used.

[0023] In a particularly preferred embodiment, the rotational speed at the tooth tip of the workpiece is at least 10 m / min, more preferably at least 20 m / min, in particular at least 40 m / min. More preferably, these rotational speeds are even higher than 60 m / min, more preferably than 120 m / min, in particular than 180 m / min. Machining can therefore take place at speeds approximately in the order of magnitude of those that also occur during power skiving of typical gears. In this way, under reasonable cutting conditions, the total machining time remains within reasonable limits even when a high number of workpiece rotations are carried out, for example 3 or more, even 6 or more, even 10 or more.

[0024] In a preferred embodiment, the feed per workpiece revolution for the first relative movement is at least 2 µm, preferably at least 4 µm, even more preferably at least 10 µm, in particular at least 20 µm, and / or not more than 0.6 mm, preferably not more than 0.4 mm, in particular not more than 0.2 mm.

[0025] The process could be used to create not only chamfers, but also, for example, slope-like structures on gears, such as those used for gear shifting. In a particularly preferred process configuration, the machining process creates a chamfer on the tooth edge, the chamfer width of which is preferably less than 30%, in particular less than 20%, of the tooth thickness at the pitch circle.

[0026] Variants are conceivable in which the tool toothing has differently designed areas and is designed in particular as a toothing covering a certain range of profiles, and if necessary, the machining is carried out in several machining passes in which different toothing areas carry out the machining on different areas in the tooth height direction of the workpiece toothing. In a particularly preferred embodiment, however, the profile of the tool toothing is essentially that of the counter toothing of the workpiece toothing with regard to the rolling coupling. In this case, the tool toothing is a workpiece-specific toothing, in contrast to universal tools. This does not mean, however, that the machining must be carried out using the double-flank method. Rather, it is preferred that the machining be carried out using the single-flank method, in which case, for example,Following the machining of one tooth flank(s) at one of the respective tooth gap(s) of the workpiece, the other tooth flank(s) are machined.

[0027] Even with such a single-flank machining process, it is preferred that the other tooth flank(s) be machined with the same tool and / or the same setup as the one tooth flank(s). This simplifies the process and reduces the number of tools required.

[0028] In another advantageous embodiment, the tooth thickness of the tool toothing is reduced compared to that required for double-flank machining in the rolling coupling. This reduces the risk of collision on the opposing flank.

[0029] In the sense of a full toothing, the tool toothing can also have a matching tool tooth for each tooth gap of the workpiece (pitch without a step factor). However, the process can also be carried out with fewer teeth than the full toothing, for example, with a step factor of 2 or 3, but preferably with at least enough teeth to ensure that an average step factor of 4 is not exceeded, and in particular a step factor of 3 is not exceeded.

[0030] In a preferred embodiment, the tool toothing can be designed to be thin with respect to the dimension in the direction of the tool rotation axis, for example with a dimension of no more than 1.5 cm. Since the work output of the tool toothing is lower than that of tools that create toothing, even significantly thinner toothings can be used, even with dimensions less than 1 cm, more preferably less than 0.7 cm. However, variants with thinner disc thicknesses of the tool toothing of 0.4 cm or less are also conceivable, down to disc thicknesses no greater than 3 mm, even 2 mm are conceivable. If work is to be carried out in the miniature range, disc thicknesses of no more than 1 mm, even no more than 0.5 mm, in particular no more than 0.3 mm are also considered, for example by wire erosion.Such tools can also be used to machine tooth edges when there is little (axial) machining space available due to shoulders or other interfering contours, for example on workpieces with multiple gears.

[0031] The tool can be made of solid material, even sintered, and is particularly suitable as a disposable tool. A base body could also be equipped with cutting teeth or groups of cutting teeth, for example in the form of cutting inserts, especially indexable inserts. Constructive clearance angles can be created by recesses in the tooth faces. Wedge angles of less than 90° can be achieved alternatively or additionally by conically shaped tool tooth flanks.

[0032] To superimpose contributions from different machine axes to realize the displacement movement of the envelope, it is advantageous to assume a discrete infeed in the axial direction and to consider the (desired) displacement to be achieved for a given axial penetration depth. For example, one could first define the radial movement X(Z) via the desired radial penetration depth at the tooth root, where neither tangential nor additional rotations contribute significantly to the shape change. The definition of Y(Z), for example, is then carried out taking into account that, depending on the pressure angle, the radial displacement X(Z) also causes an additional contribution in the Y direction.If the workpiece rotation axis is integrated, depending on the accuracy requirements, it can be considered that the displacement via ΔC also has a component in the radial direction that must be included, which varies slightly across the tooth height of the workpiece gearing. Using both ΔC and ΔY results in an additional degree of freedom with which the chamfer design can be varied even across the tooth height, for example, to create comma-shaped chamfers. For the latter, which already omits the tooth root, the radial axis X is also available as an additional degree of freedom.

[0033] As already explained above, a surface formed by the method can be composed of the end regions of the material removal achieved via the envelope curve, which varies depending on the state of movement of the first relative movement. This type of generation of new tooth surfaces (regions) is disclosed by the invention as independently worthy of protection, regardless of the exact function of the new tooth surface and the specific orientation of the tooth rotation axes relative to one another. For this purpose, the invention provides, in a further aspect, a

[0034] Method for machining a tooth flank region of a workpiece toothing, in particular a tooth edge formed between a tooth flank and a face of a workpiece toothing, with a tool toothing, in which the toothings rotate in rolling coupling about their respective toothing axes, and in which a new toothing surface is formed by machining the tooth flank region, which is essentially characterized in that the machining takes place over a plurality of workpiece rotations,wherein a first relative movement is carried out with a directional component parallel to the workpiece rotation axis between the workpiece toothing and the tool toothing, and by means of a second relative movement, which varies in particular depending on the movement state of the first relative movement, the position of the envelope curve of the tool tooth rolling positions relative to their engagement position with the tooth flank of the workpiece toothing, as seen in projection onto the plane orthogonal to the workpiece rotation axis C, is shifted transversely to the profile of the workpiece toothing and in particular orthogonal to the tool rotation axis, and thereby material is removed along a cutting surface during each pass of a respective workpiece rotation, wherein the shape of the new toothing surface is composed of the end regions of the cutting surfaces from the plurality of workpiece rotations. Thus, cutting is preferably carried out in a plane that is substantially orthogonal to the tool rotation axis.

[0035] It is understood that the aspects explained above regarding preferred designs, in particular for the formation of a phase as a new gear surface, can also be used for the method just defined.

[0036] In a preferred design, the gear axes of the tool and workpiece could both lie in the same plane, but one could be inclined at an angle to the other. This axis position can be particularly suitable for cases where an area close to the front edge is being machined, and the relevant front plane of the gearing is not orthogonal to the workpiece axis, but is also inclined relative to it. The inclination of the relative axes could then be adjusted to this inclination value of the front surface relative to the orthogonal plane to the workpiece rotation axis.

[0037] In addition to the creation of phases as new tooth surface areas, the creation of slopes has already been discussed. In this context, a lead-in surface for a starter pinion could also be created.

[0038] With regard to the above-mentioned inclination angle, it is also considered to create new tooth surfaces on conical or beveloid gears, whereby the tool is applied at such an angle that the cutting profile of the tool is arranged parallel to the profile of the phase on a conical outer side of the conical gear, by means of the axis orientation of the tool and the bevel gear.

[0039] In this context, it is also envisaged that for the creation of the new gear surface, in particular a phase, not only cylindrically toothed workpieces are used, but also crowned gears or, in particular, bevel gears. In this context, it is preferred to work with bevel gears (beveloids and hypoids) designed for shaft angles of less than 60°, more preferably less than 40°, in particular less than 30° (for the individual workpiece, correspondingly with a conicity of approximately half of these values). Accordingly, the inclination angle of the tool could then be adjusted to the pitch cone angle of the bevel gear.

[0040] In a further preferred embodiment, the gear cutting tool could already be integrated into a tool arrangement with a main tool or into the main tool which is integrated into the workpiece gearing on which a new gear surface, in particular a chamfer, is created using the method. In particular, the gearing could be created using the back of a shaping wheel (in gear shaping) or skiving wheel (in power skiving). In particular for a main machining operation for production by power skiving, it could be considered to also design the tool as a combination tool with the chamfering tool, in particular in the form of two disk-like tools which are arranged directly one above the other in the axial direction so that their axes of rotation coincide.Such a gear cutting tool could also be formed on a first end face with the cutting edges for skiving with a profile designed for skiving, and on the back face with a profile designed for gear shaping of the identical toothing, which could then be carried out under parallel axes (as in gear shaping) or possibly under axes that are preferably in one plane but at an angle of inclination to one another, while for the gear skiving process that produces the toothing, an axis crossing angle is set to which the gear skiving process is designed.

[0041] According to a further aspect, the new gear surface would not necessarily have to be adjacent to a front side of the machined gear. For example, the creation of backings, in particular with axes of rotation that are inclined to one another or, in particular, with parallel axes of rotation, is also being considered. For this purpose, the gear cutting tool could also be manufactured as a very thin disk and, in a first step, a correspondingly thin incision could be created that does not yet cover the full backing width. If necessary, this could be done with a second, oscillating relative movement up to the desired backing depth but still at the same height in the workpiece axis direction. The process steps could then be used as for creating a phase according to the description above, but with the same extent of the transverse movement to create uniformly deep incisions until the full axial backing width is reached.

[0042] In this respect, it is recognizable and disclosed that the method can certainly and preferably be carried out with gearing axes of rotation that are parallel to one another in order to machine a tooth edge, in particular to produce a chamfer, by machining with the first and second relative movement, but on the other hand the method with the composition of the new gearing surface from the end regions of the cutting surfaces from the plurality of workpiece rotations is also applicable for new gearing surfaces, in which work is carried out with non-parallel gearing axes of rotation or in which no machining of the tooth edge, in particular no formation of a chamfer surface as a new gearing surface, takes place.

[0043] In terms of device technology, the use according to claim 17 of a chamfering tool is provided for machining a tooth edge formed between a tooth flank and end face of a workpiece toothing, with machining carried out essentially with mutually parallel toothing axes of rotation in rolling coupling with one another in the form of a tool toothing with chip surfaces formed by the tooth flanks of the tool toothing, in particular designed for machining according to a method according to one of the aspects explained above and / or with the design properties specified above.

[0044] The invention is also protected by a control program according to claim 18, which contains control instructions which control the machine to carry out a method according to one of the aforementioned method aspects when executed on a control device of the gear cutting machine.

[0045] Furthermore, the invention provides a gear cutting machine according to claim 19 with at least one workpiece spindle for rotatingly driving a workpiece toothing about its workpiece rotational axis, and at least one tool spindle for rotatingly driving a tool toothing about its rotational axis, at least one first machine axis which allows a first relative movement between the workpiece toothing and the tool toothing parallel to the workpiece rotational axis, characterized by a control device which has control instructions for carrying out a method according to one of the aforementioned method aspects.

[0046] The gear cutting machine can be a larger machine complex that also includes a main tool spindle for producing the gears. However, the gear cutting machine can also be designed as a standalone machining station. In a simple design, a machine axis is provided with the main component oriented in the direction of the workpiece rotation axis, preferably in the direction of the workpiece rotation axis for the initial movement. For vertical machines, this would be the vertical axis.

[0047] Preferably, a radial axis is also provided to keep the station usable for workpieces and tools of different diameters, and optionally as an additional feed axis. In a further embodiment, a tangential axis can also be implemented as a linear machine axis, preferably orthogonal to the radial axis and orthogonal to the workpiece rotation axis. In a particularly preferred embodiment, the gripping station has no pivot axis or tilt axis, which could change the parallel arrangement of the tool rotation axis and the workpiece rotation axis. Likewise, the linear tangential axis can preferably be omitted in order to simplify the station design.

[0048] The tool rotation axis is preferably a driven axis, either via a direct drive or an indirect drive. It goes without saying that a control system for the machine axes, which are designed as NC axes, is present, which is capable of maintaining a synchronous rolling coupling and de-phased in a targeted and controlled manner through additional rotations. In this context, a centering device is preferably provided, which, for example, has a contactless centering sensor.

[0049] The chamfering wheels, which are also designed very thin according to the invention, also allow tooth edge machining under unfavorable spatial conditions, such as those caused by interfering contours, and can also be designed, for example, as a tandem tool. A rotationally fixed combination of a skiving wheel for producing the workpiece toothing and the chamfering wheel according to the invention is also conceivable. The machine axes of the main machining unit are then available for chamfering, albeit at the expense of longer idle times. It is also possible to rotationally fixedly couple two chamfering wheels according to the invention designed for different workpiece toothings to form a tandem tool, for example for tool-change-free chamfering of different workpiece batches or for machining workpieces with two or more different toothings.

[0050] Further features, details and advantages of the invention will become apparent from the following description with reference to the accompanying figures, of which Fig. 1 shows a gear-shaped tool and a toothing machined by the tool, Fig. 2 shows a section of the workpiece with a generated chamfer, Fig. 3a is an explanatory view for generating the chamfer, Fig. 3b is an enlarged section of Fig. 3a shows, Fig. 4 shows a moment position during a retraction movement, Fig. 5 shows an envelope curve shifted with respect to a workpiece tooth profile, Fig. 6a, 6 are explanatory views of a single-flank machining, Fig. 7 is an illustration of a comparatively thin tool toothing, Fig. 8a, b are schematic illustrations for the machining of tooth edges that are difficult to access and Fig. 9 schematically shows a chamfering unit.

[0051] In Fig. 1 A perspective view of a workpiece 2 with an already manufactured internal gear 3 is shown. The internal gear 3 is straight-toothed in this embodiment, but helical gears can also be machined, as can external gears.

[0052] The Fig. 1 The machining operation shown takes place on the lower end face 2b of the workpiece 2. In this exemplary embodiment, the tooth edges of the essentially involute teeth 4 of the internal gearing 3 are to be provided with a chamfer on the end face 2b. It is understood that further chamfering can then also be performed on the other end face 2a. However, the method is also suitable for non-involute workpiece gearings that can be generated.

[0053] Machining is carried out with a tool toothing 13. For this purpose, in this embodiment, a disk-shaped tool 10 is provided, which is externally toothed with the tool toothing 13. In this embodiment, the tool toothing 13 is the counter toothing of the internal toothing 3. This means that when the workpiece 2 and tool 10 mesh with each other in synchronous rolling coupling, the teeth 14 of the tool toothing 13 plunge into the tooth gaps formed between the teeth 4 of the internal toothing 3 and roll on the workpiece tooth flanks. The envelope curve of the rolling positions of the tool teeth 14 reflects the essentially involute profile on the tooth flank of the workpiece tooth 4. If, as in preferred process designs, machining is carried out using the single-flank method, the tooth thicknesses of the tool teeth 14 can also be made thinner than required for a contacting double-flank rolling engagement. As also shown in Fig. 1 As can be seen, no axis crossing angle is provided between the rotational axes C of the workpiece toothing 3 and B of the tool toothing 13, the rotational axes B and C run parallel. The other axes X, Y and Z, which are used as a coordinate system in Fig. 1 can be realized partly or entirely as linear machine axes of a processing machine not shown, such as Z (feed, parallel to C), X radial axis (axis distance direction), Y tangential direction.

[0054] The Fig. 1 The relative position shown between the tool toothing 13 and the workpiece toothing 3 is essentially the situation at the start of machining. Before machining begins, the edges 6 formed between the end face 2b of the workpiece 2 and the adjacent tooth flanks of the teeth 4 are still sharp-edged, for example in a shape resulting from a previous process for producing the internal toothing 3, such as by gear skiving, hobbing, gear shaping, or other shaping processes, wherein primary burrs formed during the machining of the toothing may already have been removed.

[0055] The aim of the tooth edge machining of this embodiment and numerous preferred process designs is the formation of a chamfer 8 at the location of the former tooth edge 6, as shown, for example, in the illustration of Fig. 2 For the purpose of an enlarged view, Fig. 2 only the area near the base of a tooth gap 5 and the area near the head of a tool tooth 14.

[0056] Based on Fig. 3a A preferred example for creating the chamfer 8 will now be described. By means of an axial relative movement, the workpiece toothing 13 is moved by Δz above the axially viewed height level of the lower end face 2b of the workpiece toothing 3. In addition, for example, by an additional rotation ΔC of the workpiece relative to the phase position of the synchronized rolling coupling, the envelope curve of the tool tooth rolling positions is shifted in the tangential direction Y by an amount that corresponds to a chamfer width w, which in this exemplary embodiment is, for example, 0.3 mm. As a result, a sharp edge 19, which is provided between the end face 12 of the tool 10 and the cutting surface 18 on the tool 10 formed by the tooth flank surface of the tool toothing 13, cuts off material on the end face 2b of the workpiece 2 while executing the rolling movement of the rolling engagement. The cutting movement here is essentially in the plane orthogonal to the rotation axis C.It ends at a distance from the previous tooth edge 6 equal to the chamfer width w. By repeating this process with the tool 10 axially immersed deeper, but with a reduced displacement by ΔY, the next cut in the next revolution only reaches up to w- ΔY, and so on, as in . Fig. 3a This results in a slicing removal of material with varying cutting depths in the tangential direction and thus also with varying extensions in the flank normal direction. At the end of the axial movement, when the axial penetration depth equal to the desired chamfer depth d is reached, the displacement is back to zero and, in this embodiment of implementing the transverse movement via an additional rotation ΔC, the phase position of the synchronous rolling coupling is again achieved.

[0057] If the displacement movement were to be accomplished only via linear machine axes, the phase position of the synchronous rolling coupling would be maintained during machining, and the effect of slice-by-slice removal would be achieved by a corresponding displacement of the envelope curve via machine axis settings, for example via the tangential axis Y. It is also conceivable that the radial axis X could act or contribute. In addition, combinations of axis movements X,Y; X, ΔC; Y, ΔC; X, Y, ΔC can be used. Participation of the radial axis is preferred if a root chamfer is also to be created, as in Fig. 2 shown.

[0058] Preferably, and as in this example, the axial movement is carried out by means of a continuous feed movement with an adjustable feed per workpiece revolution. In the illustrated embodiment, for example, a workpiece speed of 1000 rpm and a feed per workpiece revolution of 0.02 mm are set. To generate the Fig. 3 For the chamfer shown with, for example, a chamfer width of approximately 0.3 mm and a chamfer depth d of approximately 0.3 mm corresponding to a chamfer angle of approximately 45°, 15 workpiece revolutions are carried out (in Fig. 3 and their enlarged section in Fig. 3a For the purpose of simplicity, only a small number of stages of step-by-step and slice-by-slice removal are shown).

[0059] To smooth the surface of the chamfer 8, in this embodiment, the edge 19 of the tool toothing 13 is guided again along the chamfer 8. For this purpose, the direction of movement in the axial direction is reversed and the relationship between the displacement of the envelope curve and the current axial plunge depth is maintained, but preferably a phase shift by α is provided, preferably in the range [90°-270°]. It is also possible to work with a lower feed rate during the plunge movement than during the retraction movement. A moment situation of this smoothing retraction movement is shown in Fig. 4 shown.

[0060] In Fig. 5 it is shown again how the envelope curve 28 from the individual rolling positions 29i is offset from its zero position corresponding to the profile of the workpiece tooth flank due to the displacement movement.

[0061] From the Figuren 6a und 6b Displacement movements can be seen again, as well as the single-flank process chosen in preferred process designs (right and left flanks are not chamfered simultaneously, but one after the other, but in this example with the same tool).

[0062] Fig. 7 shows a chamfering tool in plan view and in a side view. From the latter it can be seen that the wheel thickness h of the tool toothing in this embodiment is only 3 mm. Fig. 7 The chamfering wheel shown has 40 teeth with a module of 2 and a pressure angle of 20°. It is understood that the gearing data, such as the number of teeth or wheel thickness, can also take on other values.

[0063] Comparatively thin chamfering wheels are also well suited for machining hard-to-reach tooth edges, such as in the Fig. 8a schematically illustrated situation in which a workpiece 2' has two different external toothings 3' and the lower end face of the upper toothing 3'a is axially only a small distance from the upper end face of the lower toothing 3'b. In Fig. 8b The tool is designed as a tandem tool with two tool teeth. One tool tooth 13'a is used for chamfering the workpiece tooth 3'a, and the second tool tooth 13'b is used for chamfering the other workpiece tooth 3'b.

[0064] From the Figuren 8a , bIt is also clear that the presented method can be used to chamfer external gears just as well as those produced using Fig. 1 described chamfered internal gearing 3.

[0065] It is also understood that, although in Fig. 1 While the chamfering process for spur gearing is shown, the process can also be used for chamfering helical gearing. In this case, the tool gearing could also be designed as helical gearing to match the rolling engagement with parallel axes, matching the helix angle of the workpiece gearing. Alternatively, narrow, particularly conically shaped, but still spur-toothed tool gearing can be considered.

[0066] One in Fig. 9 The chamfering unit 100 shown is capable of positioning the tool rotation axis B relative to the workpiece rotation axis C (C parallel to B) via three linear axes X, Y, Z, realized via corresponding slide arrangements 110, 130, 120. The axis movements X, Y, Z, B, C are NC-controlled via control 99. For an alternative, simpler design, the slide 130 could also be omitted.

[0067] The Fig. 9The schematically illustrated chamfering unit 100 could be integrated into a gear cutting machine whose tool-side main spindle carries a tool that produces the workpiece gear teeth, such as a skiving wheel, a hob, or a gear shaping wheel. Then, chamfering could still be performed in the same workpiece clamping as the main machining operation, or at a different location, transported from the main machining location to the chamfering location by appropriate automation such as a ring loader, gripper, or a double-spindle arrangement. Likewise, the chamfering unit can be designed as a standalone chamfering machine, and the workpieces can be obtained by workpiece automation, even from multiple gear cutting machines that supply the already produced gears for supplementary tooth machining.

[0068] In particular, if the main machining and the supplementary machining are not carried out in the same clamping of the workpiece, it is provided that the (chamfering) machining unit also has means for centering, such as contactless centering sensors, in order to determine the in-phase relative rotational position for the synchronous rolling coupling.

[0069] Furthermore, the invention is not limited to the embodiments shown in the previous examples.

Claims

1. A method for machining a tooth edge formed between a tooth flank and an end face (2b) of a workpiece toothing (3), by means of a tool toothing (13), wherein the toothings (3, 13) rotate about their respective toothing rotational axes (C, B) in mutual rolling coupling, wherein the two toothing rotational axes (C, B) are substantially parallel to each other; characterized in that the machining is carried out over a plurality of workpiece rotations, wherein a first relative movement (Z) between the workpiece toothing (3) and the tool toothing (13), parallel to the workpiece rotational axis, is carried out, and, by means of a second relative movement (V), which is in particular varied according to the movement state of the first relative movement, the position of the envelope (28) of the tool tooth rolling positions (29i) is shifted relative to the engagement position of said envelope with the tooth flank of the workpiece toothing in the plane (X-Y) orthogonal to the workpiece rotational axis (C), transversely to the profile of the workpiece toothing.

2. The method according to claim 1, wherein a transverse movement (Q) of the workpiece toothing and / or tool toothing running transversely to the centre distance axis of the rotational axes contributes to the second relative movement.

3. The method according to claim 2, wherein the transverse movement (Q) comprises an additional rotation (ΔC) of the workpiece toothing.

4. The method according to claim 2 or 3, wherein the transverse movement comprises a movement of a linear machine axis (Y) whose directional component orthogonal to the workpiece rotational axis and orthogonal to the centre distance axis (X) predominates over the respective directional component along these axes.

5. The method according to one of the preceding claims, wherein the tooth edge in the tooth base of the workpiece toothing is also machined.

6. The method according to one of the preceding claims, wherein a radial movement (ΔX) of the workpiece and / or tool toothing running in the direction of the centre distance axis of the rotational axes contributes to the second relative movement.

7. The method according to one of claims 2, 5 and 6, wherein the shape of the chamfer (8) is effected on the tooth base by adjusting the radial movement according to the movement state of the first relative movement, and the shape of the material removal at the tooth edge in the tooth flank region is determined by adjusting the transverse movement according to the movement state of the first relative movement and the movement state of the radial movement.

8. The method according to one of claims 3 and 4, wherein the profile of the material removal in the tooth height direction is determined by superimposing the transverse movement contributions from the additional rotation (ΔC) and the linear machine axis movement (ΔX, ΔY).

9. The method according to one of the preceding claims, comprising a further machining pass, which has in particular an otherwise identical or phase-shifted coupling of the first and second relative movement, and a movement control which is however carried out with a reverse movement direction of the first relative movement.

10. The method according to one of the preceding claims, wherein the rotational speed at the tooth tip of the workpiece is at least 10 m / min, preferably at least 20 m / min, more preferably at least 40 m / min.

11. The method according to one of the preceding claims, wherein a chamfer (8) is produced on the tooth edge during machining.

12. The method according to one of the preceding claims, wherein the profile of the tool toothing is substantially that of the counter-toothing of the workpiece toothing with respect to the rolling coupling.

13. The method according to one of the preceding claims, which is carried out using a single-flank process, wherein following the machining of one or more tooth flanks on one or more of the respective tooth gaps of the workpiece, one or more other tooth flanks are machined.

14. The method according to claim 12, wherein the machining of the one or more other tooth flanks is carried out with the same tool and / or in the same clamping process as those used for the one or more tooth flanks.

15. The method according to one of the preceding claims, wherein the tooth thickness of the tool toothing is reduced when compared to the tooth thickness required for a two-flank machining using rolling coupling.

16. The method according to one of the preceding claims, wherein the dimension (h) of the tool toothing along the tool rotational axis is less than 1.5 cm, preferably less than 1 cm, more preferably less than 0.7 cm and most preferably less than 0.4 cm.

17. Use of a chamfering tool (10) in the form of a tool toothing with machining surfaces formed by the tooth flanks of the tool toothing for machining - according to one of the preceding claims - a tooth edge formed between a tooth flank and the end face of a workpiece toothing, using toothing rotational axes that are substantially parallel to each other and with mutual rolling coupling.

18. A control program comprising control instructions which, when executed on a gear-cutting machine, controls the machine for carrying out a method according to one of claims 1 to 16.

19. A gear-cutting machine (100) comprising at least one workpiece spindle for rotatingly driving a workpiece toothing about its workpiece rotational axis (C), and at least one tool spindle for rotatingly driving a tool toothing about its rotational axis (B), and having at least one first machine axis (Z) which allows for a first relative movement between the workpiece toothing and tool toothing, parallel to the workpiece rotational axis, characterized by a control device (99) having control instructions for carrying out a method according to one of claims 1 to 16.