Method for producing a modified tool surface geometry of a machining tool, machining tool and method for machining a pre-toothed workpiece in a rolling engagement

Abstract

The invention relates to a method for producing a modified tool surface geometry of a helically profiled machining tool (1), which is designed for machining a pre-toothed workpiece (2) in a rolling engagement, wherein a tooth flank surface geometry of a tooth flank of the workpiece (2) is specified, the machining tool (1), which has a reference surface geometry with a reference profile (PR), is provided, the reference surface geometry being based on a conjugate image of the specified tooth flank surface geometry, and a modified tool surface geometry is produced by producing a profile modification (K,F), the profile modification being selected such that the modified tool surface geometry produces a surface pressure distribution with a smaller spatial fluctuation on the tooth flank of the pre-toothed workpiece (2) compared to the reference surface geometry when the machining tool (1) and the pre-toothed workpiece (2) are in rolling engagement.

Description

[0001] TITLE

[0002] MODIFICATION OF THE TOOL SURFACE GEOMETRY OF A MACHINING TOOL FOR MACHINING A PRE-TOUCHED WORKPIECE

[0003] TECHNICAL AREA

[0004] The present invention relates to a method for producing a modified tool surface geometry of a machining tool which is helically profiled and designed for machining a pre-toothed workpiece in a rolling engagement, a machining tool with a correspondingly modified tool surface geometry, and a method for machining a pre-toothed workpiece in a rolling engagement with the said machining tool.

[0005] STATE OF THE ART

[0006] The finishing of a geared workpiece by gear machining with a helical-profile machining tool, also called a grinding worm, typically involves one or more grinding processes in which material is selectively removed to create a predetermined tooth flank surface geometry with a predefined tooth profile on the workpiece. Such grinding processes include, for example, roughing and finishing the workpiece. Following these shaping grinding processes, a polishing process can be performed, which generally does not alter the tooth flank surface geometry but serves to influence the surface quality, in particular the roughness of the tooth flank surfaces of the workpiece. The grinding and polishing processes can be carried out with a single machining tool that has different machining areas designed for the respective process.Alternatively, each process can be carried out using a separate processing tool.

[0007] EP0282046A2 discloses a tool which has a grinding screw and a polishing screw arranged one behind the other at axial distance on one and the same tool spindle, the tooth profiles of which are essentially the same, wherein the polishing screw consists of a soft-elastic plastic material with embedded hard grains, the elasticity of which allows it to adapt to the existing flank geometry of the workpiece and only improve the surface roughness.

[0008] WO2022028871 discloses a grinding screw with two machining sections, wherein the two machining sections are geometrically identical but have different surface structures to achieve a higher surface quality on the workpiece.

[0009] However, if the geometrically identical machining areas (or the successively used machining tools with the same profile) exhibit different deformation behavior, for example, due to different bonding agents, undesirable cutting and / or friction effects can occur, negatively impacting the surface quality of the workpiece. In particular, machining the workpiece with a machining area or tool that has a lower modulus of elasticity compared to the preceding machining area or tool can lead to undesirable local increases in surface pressure.

[0010] Critical areas of a tooth flank, where pressure build-up can occur and lead to thermal damage to the workpiece surface, include, in particular, the tip and / or root of the toothed workpiece. While it is conceivable to reduce the surface pressure between the machining tool and the tooth flanks in these critical areas by adjusting the kinematic process parameters, this also reduces the surface pressure in other, non-critical areas of the tooth flank, such as the area between the tip and root of the workpiece tooth flank. Consequently, the surface pressure in these non-critical areas of the tooth flank drops to a value that is too low to achieve the desired surface quality.

[0011] PRESENTATION OF THE INVENTION

[0012] In a first aspect, it is therefore an object of the present invention to specify a method which results in a machining tool with a tool surface geometry that is suitable for minimizing local thermal damage during the machining of a pre-geared workpiece.

[0013] This problem is solved by a method according to claim 1. Further embodiments are specified in the dependent claims.

[0014] A method for generating a modified tool surface geometry of a machining tool is proposed, wherein the machining tool has a helical profile and is designed for machining a pre-toothed workpiece in a rolling engagement, and the method comprises:

[0015] Specifying a tooth flank surface geometry of a tooth flank of the workpiece;

[0016] Providing the machining tool, wherein the machining tool defines a tool rotation axis and has a machining area axially along the tool rotation axis, which has a reference surface geometry with a reference profile, wherein the reference surface geometry is based on a conjugate mapping of the specified tooth flank surface geometry;

[0017] Generating the modified tool surface geometry along the machining area of ​​the machining tool by generating a profile modification, in particular a profile angle modification and / or a profile shape modification, of the reference profile over at least one section of the reference profile,

[0018] wherein the profile modification is chosen such that the modified tool surface geometry, compared to the reference surface geometry, produces a surface pressure distribution with a lower spatial variation on the tooth flank of the pre-toothed workpiece when the machining tool and the pre-toothed workpiece are in rolling engagement.

[0019] In this context, the term "surface pressure" refers to the force per contact area, in other words, compressive stress. The smaller the spatial variation in the surface pressure distribution, the more homogeneous the surface pressure is across the tooth flank of the workpiece.

[0020] In particular, a tooth profile and flank lines of the workpiece can be specified, which together define the tooth flank surface geometry of the workpiece. The tooth profile can, in particular, be based on an involute profile. The specified tooth flank surface geometry preferably corresponds to a final tooth flank surface geometry that is to be achieved after finishing the workpiece.

[0021] In this context, the term "surface geometry" is used for the macroscopic shape of the tooth flanks of the workpiece or machining tool. In contrast, the terms "surface quality" and "surface roughness" refer to the microscopic properties.

[0022] A conjugate mapping is a mapping of the tooth flank surface geometry of the workpiece onto the machining tool, calculated taking into account the gear law.

[0023] The profile modification can be calculated, for example, by numerical simulation of the surface pressure distribution between the workpiece and the machining tool, especially taking into account material properties of the machining tool, such as the modulus of elasticity (E-modulus).

[0024] Additionally or alternatively, the profile modification may have been determined experimentally, for example by an iterative dressing process of the machining tool with subsequent machining of the workpiece, whereby a characteristic value for the surface finish, in particular the surface roughness of the tooth flank of the workpiece, is determined, and wherein the profile modification is adjusted such that the characteristic value varies across the tooth flank of the workpiece by less than 30%, in particular less than 20%, preferably less than 10%.

[0025] The average roughness value R can be used as a key indicator, for example. aor the roughness depth R z The value specified in VDI / VDE 2612 Sheet 5 can be used. Alternatively, a characteristic value from the Abbott curve according to DIN ISO 13565-1 can be used.

[0026] In particular, profile modification can include head and / or foot removal. In this context, head removal refers to material removal relative to the reference profile in the head region of the machining tool. Similarly, foot removal refers to material removal relative to the reference profile in the foot region of the machining tool.

[0027] Additionally or alternatively, the profile modification can include a profile shape modification in an area between the head area and the foot area of ​​the machining tool, which specifically influences the surface roughness in a corresponding sub-area of ​​the tooth flank of the workpiece.

[0028] Alternatively, the profile modification can include a profile angle modification, which affects the surface roughness over the entire tooth flank between the head and root of the workpiece.

[0029] In particular, the profile modification can be a convex or concave profile modification.

[0030] Preferably, the machining area along which the modified tool surface geometry is created is designed as a polishing area for polishing the workpiece.

[0031] In this context, the term "polishing" refers to a process that affects the microscopic texture, but not the surface geometry, i.e., not the shape, of the tooth flanks of the workpiece.

[0032] The polishing area can have a density of 1.1 - 1.5 g / cm³. 3 and / or have an E-modulus of 1.5-6 GPa, in particular of 1.9 - 4.2 GPa.

[0033] The machining tool can have a first machining area and a second machining area axially along the tool rotation axis, whereby the reference surface geometry is maintained in the first machining area and the modified tool surface geometry is generated in the second machining area.

[0034] The machining tool can be, in particular, a multi-range grinding screw, especially a dual-range grinding screw, in which the first machining area and the second machining area are seamlessly adjacent to each other. Alternatively, the first machining area can be provided by a first grinding screw and the second machining area by a second grinding screw, wherein the first grinding screw and the second grinding screw are separated from each other by an axial gap and arranged on a common tool carrier.

[0035] Alternatively, the machining area along which the modified tool surface geometry is generated can extend along the entire machining tool. This can be the case, in particular, if the machining tool is a polishing screw, which is intended as a separate machining tool for polishing the workpiece.

[0036] In particular, generating the modified tool surface geometry can include:

[0037] Creating the profile modification by line dressing, in particular with a single-radius forming roller or a double-radius forming roller.

[0038] Alternatively, generating the modified tool surface geometry can include:

[0039] Producing the profile modification by single-flank profile dressing or double-flank profile dressing with a dressing tool that has straight, concave or convex dressing flanks.

[0040] In particular, providing the machining tool with the reference surface geometry may include:

[0041] Primary dressing of the machining tool with a primary dressing tool to generate the reference surface geometry,

[0042] generating the modified tool surface geometry includes:

[0043] Secondary dressing of the machining tool with a secondary dressing tool that differs from the primary dressing tool to generate the profile modification.

[0044] The primary dressing tool can be, in particular, a double-conical disc, a profile roller, a set of profile rollers, or a solid profile roller. The secondary dressing tool can be, in particular, a single-radius forming roller, a double-radius forming roller, or a dressing tool with concave dressing flanks.

[0045] Alternatively, providing the machining tool with the reference surface geometry can include:

[0046] Primary dressing of the machining tool with a dressing tool to generate the reference surface geometry, wherein the dressing tool is in a primary dressing position,

[0047] generating the modified tool surface geometry includes:

[0048] Secondary dressing of the machining tool with said dressing tool, wherein the dressing tool is pivoted relative to the primary dressing position to generate the profile modification and / or follows a pitch movement which deviates from a screw pitch of the reference surface geometry.

[0049] The pivoting relative to the primary dressing position can be carried out in particular about a pivot axis which is perpendicular to the tool rotation axis of the machining tool.

[0050] In particular, in a case where the primary dressing and the secondary dressing are carried out with the same dressing tool, the dressing tool may in particular be a double conical disc, a profile roller or a set profile roller.

[0051] In a second aspect, the present invention provides a machining tool for machining a pre-toothed workpiece in a rolling engagement, wherein the machining tool has a helical profile, wherein the machining tool defines a tool rotation axis and has a machining area axially along the tool rotation axis, and

[0052] wherein the machining tool has a modified tool surface geometry along the machining area with a profile that is modified over at least one section of the profile by a profile modification, wherein the profile modification is selected such that the modified tool surface geometry enables a surface pressure distribution with a lower spatial variation on the tooth flank of the pre-toothed workpiece when the machining tool and the pre-toothed workpiece are in a rolling engagement, compared to a non-modified tool surface geometry.

[0053] The machining tool may have been modified, in particular by the aforementioned method.

[0054] In particular, the workpiece can have a specified tooth flank surface geometry, wherein the profile of the modified tool surface geometry differs from a reference profile of a reference surface geometry, which is based on a conjugate mapping of the specified tooth flank surface geometry, by the said profile modification, and

[0055] where the modified tool surface geometry, compared to the reference surface geometry, enables a surface pressure distribution with less spatial variation on the tooth flank of the pre-toothed workpiece when the machining tool and the pre-toothed workpiece are in a rolling engagement.

[0056] The profile modification may include, in particular, a head retraction and / or a foot retraction.

[0057] Preferably, the machining area with the modified tool surface geometry is designed as a polishing area for polishing the toothed workpiece. The polishing area can, in particular, be made of polyurethane. The polishing area can, in particular, have a density of 1.1–1.42 g / cm³. 3 and / or have an elastic modulus of 1.9 - 4.2 GPa.

[0058] The machining tool can have a first machining area and a second machining area axially along the tool rotation axis.

[0059] wherein the first machining area has the unmodified tool surface geometry, in particular the reference surface geometry, and

[0060] the second machining area features the modified tool surface geometry.

[0061] In particular, the first machining area of ​​the machining tool can have an E-modulus that is at least three times the E-modulus of the second machining area of ​​the machining tool.

[0062] Alternatively, the modified tool surface geometry can extend along the entire machining tool. This can be the case, in particular, if the machining tool is a polishing screw, which is intended as a separate machining tool for polishing the workpiece.

[0063] In another aspect, the invention provides a method for machining a pre-toothed workpiece in a rolling action, comprising:

[0064] Machining, in particular polishing, of the workpiece with a machining tool described above.

[0065] In the method for machining the workpiece, the machining of the workpiece can in particular be carried out with a machining tool which has a first machining area and a second machining area axially along the tool rotation axis, wherein the first machining area has the unmodified tool surface geometry, in particular the reference surface geometry, and wherein the second machining area has the modified tool surface geometry, wherein the machining of the workpiece comprises:

[0066] Machining the workpiece with the first machining area to generate the specified tooth flank surface geometry, and

[0067] Polishing the workpiece with the second machining area to achieve a desired workpiece surface quality.

[0068] BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Preferred embodiments of the invention are described below with reference to the drawings, which serve only for illustration and are not to be interpreted restrictively. The drawings show:

[0070] Fig. 1 schematically shows a typical prior art method for the gearing of a pre-geared workpiece;

[0071] Fig. 2 shows a section of a sectional view through a machining area of ​​a machining tool that is in rolling engagement with a tooth flank of a pre-toothed workpiece;

[0072] Fig. 3 shows a tooth flank profile of a workpiece, in which areas with increased surface pressure are shown;

[0073] Fig. 4 in a flowchart shows an example of a method for producing a modified tool surface geometry of a machining tool according to the present invention;

[0074] Fig. 5 shows an exemplary profile modification produced using a method according to Fig. 4;

[0075] Fig. 6 shows the gear machining of a workpiece with a grinding screw having two machining areas; Fig. 7 shows the gear machining of a workpiece with a grinding screw having a single machining area;

[0076] Fig. 8 shows an example of a dressing device;

[0077] Fig. 9 shows a first embodiment of the method shown in Fig. 4;

[0078] Fig. 10 shows a second embodiment of the method shown in Fig. 4;

[0079] Fig. 11 shows a third embodiment of the method shown in Fig. 4;

[0080] Fig. 12 shows a fourth embodiment of the method shown in Fig. 4;

[0081] Fig. 13 shows a fifth embodiment of the method shown in Fig. 4.

[0082] DESCRIPTION OF PREFERRED EXECUTION FORMS

[0083] Fig. 1 shows a typical prior art method for the gear grinding of a pre-cut workpiece. In a first step, a tooth flank surface geometry is specified that corresponds to a desired final geometry of the workpiece's tooth flanks. In a second step, a grinding tool is provided that has a reference profile suitable for generating this specified tooth flank surface geometry. The reference profile of the grinding tool required for the desired shaping of the workpiece's tooth flanks can be calculated based on a conjugate mapping of the specified tooth flank surface geometry, taking the gear kinematics into account, in a known manner, as disclosed, for example, by H. Schriefer et al. in "Continuous Gear Grinding of Gears", Reishauer AG, June 2008.A polishing tool with a profile identical to the reference profile is then provided to polish the tooth flanks of the workpiece. This polishing step serves to influence, and in particular reduce, the surface roughness of the tooth flanks of the workpiece, without altering the tooth flank surface geometry.

[0084] Typically, a machining tool with a lower modulus of elasticity (E-modulus) than the grinding tool previously used to create the tooth flank surface geometry is used in the polishing step. Due to the lower E-modulus, this machining tool exhibits less resistance to deformation. This lower resistance can lead to a locally increased surface pressure between the workpiece and the machining tool during machining, as illustrated in Fig. 2: Fig. 2 shows a section of an axial sectional view through a machining area of ​​a machining tool 1, which is in rolling engagement with a tooth flank of a pre-machined workpiece 2. The area shown in Fig.The dotted area 2 schematically represents the surface pressure distribution that occurs between the machining tool 1 and the tooth flank of the workpiece 2, with the surface pressure being increased in the region of the tooth flank edge 21 of the workpiece 2. The increased surface pressure in the region of the tooth flank edges can be explained as follows: In the region of the tooth flank, the material of the machining tool is compressed, while in an area outside the tooth flank it is not. Since the material has shear stiffness, the uncompressed area exerts shear forces on the compressed area at the tooth flank edge, leading to an increased surface pressure at said tooth flank edges. This inhomogeneous surface pressure, particularly the increased pressure in the region of the tooth flank edges, can lead to inhomogeneous heat input via the tooth flank.Locally increased heat input due to increased surface pressure can then lead to thermal damage in these areas.

[0085] Fig. 3 shows a section of an end face of a workpiece 2 with a tooth flank profile PW. A left tooth flank L and a right tooth flank R of the workpiece 2 are shown, with tooth tip regions KW and tooth root regions FW of the workpiece 2 schematically marked on the left tooth flank L and on the right tooth flank R, in which an increased surface pressure, as shown in Fig. 2, can occur.

[0086] Figure 4 shows a flowchart illustrating an embodiment of a method according to the invention for generating a modified tool surface geometry, which is proposed to solve this problem: In a first step, a tooth flank surface geometry is specified that corresponds to a desired final geometry of the workpiece tooth flanks. Additionally, a characteristic value for a range of variation in the surface finish, in particular the surface roughness of the workpiece tooth flank, can be specified, which corresponds to a desired final surface roughness. In a second step, a machining tool is provided that has a reference profile suitable for generating the specified tooth flank surface geometry. In a third step, head and root recesses are generated on the machining tool, resulting in a more homogeneous surface pressure, i.e.,a surface pressure distribution with a lower spatial variation across the tooth flank is generated between the machining tool 1 and the tooth flank of the pre-toothed workpiece 2 when the machining tool 1 and the pre-toothed workpiece 2 are in rolling engagement, in order to obtain the desired final surface roughness.

[0087] The result of the method according to Fig. 4 is illustrated by way of example in Fig. 5: Fig. 5 shows a section of an end face of the workpiece 2 and a helically profiled machining tool 1, which is in rolling engagement with the workpiece 2. The machining tool 1 has a reference surface geometry with a reference profile PR. The reference surface geometry is selected such that a predetermined, i.e., desired, tooth flank surface geometry is generated during the rolling machining of the workpiece 2. The reference surface geometry, in particular the reference profile PR, is therefore based on a conjugate mapping of the predetermined tooth flank surface geometry, in particular a predetermined tooth profile PW to be generated on the workpiece 2. In addition, profile modifications (thickened lines) are shown in Fig. 5, which are applied in a method according to Fig.4 were generated to homogenize the surface pressure between the machining tool 1 and the workpiece 2, i.e., to reduce fluctuations in the surface pressure distribution. In the example shown in Fig. 5, the profile modifications are head recesses K and root recesses F, which were specifically generated on the machining tool 1 to reduce the surface pressure between the machining tool 1 and the workpiece 2 in the head and root regions of the tooth flanks of the workpiece 2 and thereby prevent thermal damage in the head and root regions of the tooth flanks of the workpiece 2.

[0088] Figures 6 and 7 illustrate the kinematics of continuous rolling machining of the workpiece 2 with the helically profiled machining tool 1. The helically profiled machining tool 1 (grinding worm) rotates about a tool rotation axis B. The machining tool 1 engages with the gear-shaped workpiece 2 in the manner of a helical gear drive. The workpiece 2 rotates about a workpiece axis C. During a grinding or polishing stroke, the machining tool 1 is moved relative to the workpiece 2 along an axial feed direction Z, which runs parallel or inclined to the workpiece axis, preferably across the entire width of the workpiece teeth (so-called axial feed movement). The position of the machining tool 1 relative to the workpiece along a radial infeed direction X determines the amount of material removed during the grinding stroke.In order to bring new, unused areas of the machining tool 1 into engagement with the workpiece 2, the grinding screw can be moved continuously or discontinuously along a shift direction Y, which runs parallel to the tool rotation axis, i.e. to the screw axis B, relative to the workpiece 2 (so-called tangential shift movement).

[0089] All the aforementioned linear movements (feed, axial feed movement, shift movement) are understood as relative movements that can be generated either by a corresponding movement of the machining tool 1 in space and / or by a movement of the workpiece 2 in space.

[0090] In Fig. 6, the machining tool has a first machining area 11 and a second machining area 12 (shaded darker in Fig. 6). The first machining area 11 has the unmodified tool surface geometry, i.e., preferably the reference surface geometry, and can therefore be used in a method for machining the workpiece 2 to produce the specified tooth flank surface geometry in a first step. The second machining area 12 has the modified tool surface geometry and can, in particular, be used as a polishing area for polishing the workpiece 2 after producing the specified tooth flank surface geometry to achieve the desired tooth flank surface quality. The two machining areas 11 and 12 are delimited in Fig.6 directly adjacent to each other, such that kinematically a seamless transition, or a transition with a shift jump in shift direction Y, from the grinding to the polishing process is possible, which leads to a particularly efficient machining of the workpiece 2.

[0091] In Fig. 7, the modified tool surface geometry extends along the entire machining tool 1. The machining tool 1 can in particular be a polishing screw, which can be used in a set together with a corresponding separate grinding screw (not shown) that has the reference surface geometry.

[0092] The aforementioned profile modifications on the machining tool 1 can be produced, in particular, by a dressing process with one or more dressing tools. Fig. 8 shows an exemplary dressing device 30, which can be installed in a machine tool, in particular a gear grinding machine, designed for gear machining, especially continuous gear grinding of the workpiece using the helically profiled machining tool. A dressing spindle 34 is arranged on a rotary drive 33, pivotable about a pivot axis C4, and a dressing tool 31 is mounted on it.

[0093] Figures 9-13 show by way of example how the aforementioned profile modifications can be produced using one or more dressing tools.

[0094] Figures 9-12 show, in the left half of each figure, how the reference surface geometry, in particular the reference profile, is initially produced in a primary dressing step using a primary dressing tool 31 by single-flank dressing in a primary dressing position. In the examples shown in Figures 9-12, the primary dressing tool 31 is a double-conical disk with straight dressing flanks 311. Alternatively, the dressing tool 31 can have concave or convex dressing flanks.

[0095] Figures 9 and 10 each show, in the right half of the figure, how the dressing tool is pivoted relative to the primary dressing position in a secondary dressing step to generate the profile modification, for example, about the C4 axis shown in Figure 8. In a first pivot position (Figure 9), toe recesses F are generated in the example shown here. In a second pivot position (Figure 10), which differs from the first pivot position, head recesses K are generated.

[0096] Fig. 11 (right half of the figure) shows the production of head returns K and foot returns F by line alignment with a double-radius forming roller 32. Alternatively, a single-radius forming roller can be used for line alignment.

[0097] Fig. 12 (right half of the figure) shows the production of head recesses K and foot recesses F by single-flank dressing with a secondary dressing tool 32', which differs from the primary dressing tool 31 in that it has concave dressing flanks 32T instead of straight dressing flanks and thereby produces material recesses in the head and foot area of ​​the reference profile produced with the primary dressing tool 31.

[0098] Figure 13 shows, in the left half of the figure, how the reference surface geometry, in particular the reference profile, is initially generated in a primary dressing step using a primary dressing tool 3T by two-flank dressing in a primary dressing position. In the example shown in Figure 13, the primary dressing tool 3T is a profile roller with straight dressing flanks 31T. The right half of the figure shows the generation of head recesses K and toe recesses F by two-flank dressing with a secondary dressing tool 32", which differs from the primary dressing tool 31 in that it has convex dressing flanks 321" instead of straight dressing flanks, thereby generating material recesses in the head and toe regions of the reference profile produced with the primary dressing tool 3T.Alternatively, the primary dressing tool 3T can have concave or convex dressing flanks (not shown), wherein the secondary dressing tool 32" in such a case can, for example, have concave or convex dressing flanks with a radius of curvature that differs from the radius of curvature of the dressing flanks of the primary dressing tool 3T in order to produce the specified profile modification. REFERENCE SIGN LIST.

[0099] 1 machining tool

[0100] 11. Machining area with reference surface geometry

[0101] 12 Machining area with modified tool surface geometry 2 Workpiece

[0102] 21 Tooth flank edge

[0103] 30 Dressing device

[0104] 31.3T primary dressing tool

[0105] 311 Dressing flank

[0106] 32, 32', 32" secondary dressing tool

[0107] 32T, 321" dressing flank

[0108] 33 Swivel drive

[0109] 34 Dressing spindle

[0110] PW Tooth flank profile of the workpiece

[0111] KW tooth head area of ​​the workpiece

[0112] FW Tooth root area of ​​the workpiece

[0113] L left tooth flank

[0114] R right tooth flank

[0115] PR Reference Profile

[0116] K head return

[0117] F Foot return

[0118] B Tool rotation axis

[0119] C workpiece axis

[0120] C4 swivel axis

[0121] X Delivery direction

[0122] Y shift direction

[0123] Z feed direction

Claims

PATENT CLAIMS 1. Method for producing a modified tool surface geometry of a machining tool (1), wherein the machining tool (1) is helically profiled and designed for machining a pre-toothed workpiece (2) in a rolling engagement, the procedure includes: Specifying a tooth flank surface geometry of a tooth flank of the workpiece (2); Providing the machining tool (1), wherein the machining tool (1) defines a tool rotation axis (B) and has a machining area (12) axially along the tool rotation axis (B) which has a reference surface geometry with a reference profile (PR), wherein the reference surface geometry is based on a conjugate mapping of the specified tooth flank surface geometry; Generating the modified tool surface geometry along the machining area (12) of the machining tool (1) by generating a profile modification, in particular a profile angle modification and / or a profile shape modification, of the reference profile (PR) over at least one section of the reference profile (PR), wherein the profile modification is chosen such that the modified tool surface geometry generates a surface pressure distribution with a lower spatial variation on the tooth flank of the pre-toothed workpiece (2) when the machining tool (1) and the pre-toothed workpiece (2) are in rolling engagement compared to the reference surface geometry.

2. The method of claim 1, wherein the profile modification comprises a head retraction (K) and / or a foot retraction (F).

3. Method according to claim 1 or 2, wherein the machining area (12) along which the modified tool surface geometry is produced is designed as a polishing area for polishing the workpiece (2).

4. Method according to one of the preceding claims, wherein the machining tool (1) has a first machining area (11) and a second machining area (12) axially along the tool rotation axis (B), wherein the reference surface geometry is maintained in the first machining area (11) and the modified tool surface geometry is generated in the second machining area (12).

5. Method according to one of claims 1-3, wherein the machining area (12) along which the modified tool surface geometry is generated extends along the entire machining tool (1).

6. A method according to any of the preceding claims, wherein generating the modified tool surface geometry comprises: Producing the profile modification by line dressing, in particular with a single-radius forming roller or a double-radius forming roller (32).

7. Method according to any one of claims 1-5, wherein generating the modified tool surface geometry comprises: Producing the profile modification by single-flank profile dressing or double-flank profile dressing with a dressing tool (32', 32") having straight, concave or convex dressing flanks.

8. Method according to any of the preceding claims, wherein providing the machining tool (1) with the reference surface geometry comprises: Primary dressing of the machining tool (1) with a primary dressing tool (31, 3T) to generate the reference surface geometry, and comprising generating the modified tool surface geometry: Secondary dressing of the machining tool (1) with a secondary dressing tool (32, 32', 32") which differs from the primary dressing tool to produce the profile modification.

9. Method according to any one of claims 1-5, wherein providing the machining tool (1) with the reference surface geometry comprises: Primary dressing of the machining tool (1) with a dressing tool (31) to generate the reference surface geometry, wherein the dressing tool is in a primary dressing position, and generating the modified tool surface geometry includes: 19 Secondary dressing of the machining tool (1) with said dressing tool (31), wherein the dressing tool is pivoted relative to the primary dressing position to generate the profile modification and / or follows a pitch movement which deviates from a screw pitch of the reference surface geometry.

10. Method according to claim 9, wherein the dressing tool (31) is a double conical disc, a profile roller or a set profile roller.

11. Machining tool for machining a pre-toothed workpiece (2) in a rolling engagement, in particular manufactured by a method according to one of claims 1-10, wherein the machining tool (1) has a helical profile, wherein the machining tool (1) defines a tool rotation axis (B) and has a machining area (12) axially along the tool rotation axis (B), and wherein the machining tool (1) has a modified tool surface geometry along the machining area (12) with a profile that is modified over at least one section of the profile by a profile modification, wherein the profile modification is selected such that the modified tool surface geometry enables a surface pressure distribution with a lower spatial variation on the tooth flank of the pre-toothed workpiece (2) compared to a non-modified tool surface geometry.when the machining tool (1) and the pre-toothed workpiece are in a rolling engagement.

12. Machining tool according to claim 11 , wherein the workpiece (2) defines a tooth flank surface geometry and wherein the profile of the modified tool surface geometry differs from a reference profile of a reference surface geometry, which is based on a conjugate mapping of the defined tooth flank surface geometry, by the said profile modification, and wherein the modified tool surface geometry enables a surface pressure distribution with a lower spatial variation on the tooth flank of the pre-toothed workpiece (2) compared to the reference surface geometry when the machining tool (1) and the pre-toothed workpiece (2) are in a rolling engagement.

13. Machining tool according to claim 11 or 12, wherein the 20 Profile modification includes a head retraction (K) and / or a foot retraction (F).

14. Machining tool according to one of claims 11-13, wherein the machining area (12) with the modified tool surface geometry is designed as a polishing area for polishing the toothed workpiece (2).

15. Machining tool according to one of claims 11-14, wherein the machining tool has a first machining area (11) and a second machining area (12) axially along the tool rotation axis, wherein the first machining area (11) has the unmodified tool surface geometry, and wherein the second machining area (12) has the modified tool surface geometry.

16. Machining tool according to claim 15, wherein the first machining area (11) of the machining tool (1) has an E-modulus which is at least three times the E-modulus of the second machining area (12) of the machining tool (1).

17. Machining tool according to one of claims 11-14, wherein the modified tool surface geometry extends along the entire machining tool (1).

18. Method for machining a pre-geared workpiece (2) in a rolling action, comprising: Machining, in particular polishing, of the workpiece (2) with a machining tool (1) according to one of claims 11-17.

19. Method for machining according to claim 18, wherein the machining of the workpiece (2) is carried out with a machining tool (1) according to claim 15 and wherein the machining of the workpiece (2) comprises: Machining the workpiece (2) with the first machining area (11) to generate the specified tooth flank surface geometry, and Polishing the workpiece using the second machining area (12).

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