Dressing tool for dressing a grinding worm for roll-type machining of workpieces with pre-cut teeth

Abstract

A dressing tool for dressing a grinding worm for roll-type machining of workpieces with pre-cut teeth is designed for rotation about a dressing axis of rotation (A) and has a dressing flank surface which forms a circular ring in a projection plane perpendicular to a dressing axis of rotation of the dressing tool, wherein the circular ring defines a radial direction with a radial coordinate (r) and a circumferential direction with an angle coordinate (φ). The dressing flank surface is provided with a specifically generated dressing flank modification, wherein the dressing flank modification projected onto the circular ring can be described as a two-dimensional Fourier series according to the radial coordinate (r) and the angle coordinate (φ), and wherein the Fourier series has at least one Fourier coefficient not equal to zero for a circumferential frequency component not equal to zero with respect to the angle coordinate.

Description

[0001] TITLE DRESSING TOOL FOR DRESSING A GRINDING WORM FOR THE HARVING OF PRE-TOOTHED WORKPIECES TECHNICAL FIELD The present invention relates to a dressing tool for dressing a grinding worm for the generating machining of pre-toothed workpieces, a method for producing such a dressing tool, and a conditioning device designed to carry out such a manufacturing method. The invention further relates to a method for dressing a grinding worm for the generating machining of pre-toothed workpieces using such a dressing tool, as well as a method for producing a modified surface structure on a tooth flank of a pre-toothed workpiece by means of a grinding worm dressed using such a dressing tool. PRIOR ART Particularly in the context of electromobility, the topic of NVH (Noise-Vibration-Harshness) is gaining in importance, especially in the area of ​​the transmission of a vehicle due to theThe lack of a dominant noise background of the combustion engine is gaining in importance. The requirements for noise excitation behavior are often specified in the form of predefined limit values ​​in a noise frequency spectrum. Whether a workpiece meets these requirements is usually tested randomly on an end-of-line (EOL) test bench. If the measured amplitudes of isolated noise frequencies exceed the predefined limit value, the corresponding workpiece is rejected. A typical noise frequency spectrum of a rotating gear exhibits dominant amplitudes at noise frequencies that correspond to the tooth meshing frequency (fZE = gear rotation frequency x number of teeth) and the associated higher harmonics at the corresponding tooth meshing orders (ZEO). These dominant noise frequencies usually result from rotational path deviations, which arise as a result of a meshing stiffness that varies over the meshing distance. The course of theMesh stiffness as a function of position along the meshing path repeats periodically with the meshing pitch and leads to the dominant noise frequencies mentioned above. Another cause can be a "rolling hole" created during production, i.e., material that is recessed relative to the desired profile line. Overall, all rotational path deviations of a gear under load can lead to noise excitation, which is perceived as a disturbing noise. For example, if a dressing tool exhibits a certain waviness across the profile height, this is transferred to the worm flank and subsequently leads to a profile form deviation on the workpiece. Constant vibrations in the periphery of the machine tool used to machine the pre-toothed workpiece can also lead to tooth flank waviness on the tooth flank, which can be measured and result in disturbing noise characteristics of the gear.Grooves extending across the width of the gearing can lead to noise excitation. Overall, any periodic surface structure, especially in a direction perpendicular to the line of contact of paired spur gears, can lead to the excitation of a noise frequency that is dominant in the noise frequency spectrum of the gearing. Several approaches exist to improve the noise excitation behavior of a gearing. Rotational path deviations resulting from deformation of the gearing under load can be effectively reduced by a targeted modification of the tooth flank. A rolling hole can be almost completely eliminated by optimized process control. DE 102012015846 A1 discloses a generating grinding process in which a workpiece is machined with a grinding worm, wherein by means of the targeted generation of an unbalance-induced wobbling movement of the grinding worm and / or an eccentricity of the grinding worm, it is achieved that a modification,in particular a profile modification or profile waviness and / or a defined periodic flank waviness is generated on the active surface of the workpiece being machined in order to modify or prevent unwanted flank waviness. A flank waviness on the workpiece resulting from imbalance or eccentricity of a grinding worm always has order one with respect to the worm rotation frequency, i.e. it is not possible to generate a flank waviness in this way which has a higher order with respect to the worm rotation frequency. DE 102013003795 A1 discloses a method for hard fine machining of tooth flanks with corrections and / or modifications on a gear cutting machine, wherein gear pairs which are in engagement with one another within a gear unit or a testing device are machined taking into account the respective counter flanks and wherein the tooth flanks of the workpieces concerned are subjected to periodicWaviness corrections or modifications can be applied. According to the invention, the rotational error profile is determined by measuring the rotational path error of the gear pairs in a gear measuring device and / or gearbox. This measurement result serves as an input variable for defining the amplitude, frequency, and phase position for the periodic flank waviness corrections on the tooth flanks of the gear pairs for production in the gear cutting machine. A periodically repeating surface structure tends to lead to excitation within a relatively narrow noise frequency band. A surface structure that is as irregular as possible, in turn, leads to a very broad noise frequency spectrum, which approximates "white" noise, i.e., a noise frequency spectrum with the same amplitude for all noise frequencies. Such a noise frequency spectrum, in which the dominance of individual noise frequencies tends to be reduced, is considered psychoacoustically less disturbing.perceived and is therefore advantageous. In addition, with excitations with a broad noise frequency spectrum, the total excitation energy is distributed over a large frequency range, so that the noise amplitude of each individual frequency component tends to be lower than with excitations in a narrow frequency band. If the workpiece is machined using a generating grinding process with a grinding worm, periodically repeating surface structures can occur on a tooth flank, which may arise, for example, from the dressing of the grinding worm with which the tooth flank is machined: The dressing wheel used for dressing can, due to technological reasons, have differences in grain size and shape around its circumference, as well as a different grain distribution, which leads to a dressing pattern on the surface of the dressing wheel. Since the dressing wheel usually performs a large number of revolutions during one revolution of the grinding worm, thisDressing patterns are periodically projected onto the grinding worm during dressing in the worm thread direction. During the subsequent grinding of the workpiece, periodic fluctuations in the tooth flank surface in the form of grooves can then occur on the tooth flanks of the workpiece, which extend across the tooth width. DE 19905136 A 1 discloses a method in which the angle of rotation of the dressing wheel is coupled to the angle of rotation of the grinding worm with an adjustable, fixed, or programmable, variable, or a stored, stochastically changing ratio, wherein the grinding worm is moved along its axis relative to the workpiece during grinding (shift feed), so that each point on the tooth flanks of the workpiece toothing corresponds exactly to one point on the flanks of the grinding worm thread. By carefully selecting the shift feed, the above-mentioned grooves can be broken. Thus, the periodicity of theTooth flank surface structure is broken and thus, in principle, a more pleasant noise behavior is achieved. However, the structure transferred to the tooth flank is strongly dependent on the production-related stochastic dressing pattern on the surface of the dressing wheel and can therefore only be influenced via the shift feed during grinding of the workpiece. SUMMARY OF THE INVENTION In a first aspect, it is an object of the present invention to provide a dressing tool with which a grinding worm for generating pre-toothed workpieces can be dressed such that the grinding worm specifically creates a modified surface structure on a tooth flank of a pre-toothed workpiece, wherein this modified surface structure is suitable for influencing the noise behavior of the workpiece. This object is achieved by a method according to claim 1. Further embodiments are specified in the dependent claims. It isThus, a dressing tool for dressing a grinding worm for generating pre-toothed workpieces is proposed, wherein the dressing tool is designed to rotate about a dressing axis of rotation and has a dressing flank surface which forms a circular ring in a projection plane perpendicular to the dressing axis of rotation, wherein the circular ring defines a radial direction with a radial coordinate and a circumferential direction with an angular coordinate, wherein the dressing flank surface is provided with a specifically generated dressing flank modification, wherein the dressing flank modification projected onto the circular ring can be described as a two-dimensional Fourier series depending on the radial coordinate and the angular coordinate. The Fourier series has at least one Fourier coefficient not equal to zero for a circumferential frequency component not equal to zero with respect to the angular coordinate. Figuratively speaking, this means that the dressing flank modificationhas a waviness in the circumferential direction. The waviness of the dressing tool in the circumferential direction can be transferred to a grinding worm flank of a worm thread during dressing by appropriately specifying the speed ratio or the rotational angle coupling between the dressing tool and the grinding worm to be dressed, so that a worm modification with a thread waviness is formed on this grinding worm flank. This thread waviness can in turn be used to create targeted tooth flank waviness on the tooth flanks of a pre-toothed workpiece that is machined with the grinding worm. The dressing tool proposed here therefore represents a particularly simple and elegant way of dressing a grinding worm in such a way that targeted tooth flank waviness can be created on a workpiece with this grinding worm, with great flexibility regarding the wavelength and phase position of the tooth flank waviness. In contrast toA purely radial waviness of the dressing tool, which is transmitted independently of the speed ratio between the dressing tool and the grinding worm to be dressed, a waviness in the circumferential direction can be transmitted in a desired manner to a grinding worm to be dressed by specifically specifying a speed ratio or a rotational angle coupling between the dressing tool and the grinding worm to be dressed. A waviness in the circumferential direction on the dressing tool surface thus offers an additional degree of freedom with regard to a targeted transmission of the dressing flank modifications. In order to obtain a continuous transition after one revolution of the dressing tool, particularly when dressing the grinding worm, the dressing flank modification preferably has a 2π periodicity with respect to the angular coordinate, i.e. the dressing flank modification has an integer periodicity with respect to the angular coordinate.Number of wave periods. The term "wavefronts" is understood below to mean lines of constant phase position or, in other words, lines along which no amplitude modulations occur. In one embodiment, the Fourier series has no non-zero Fourier coefficient for a non-zero radial frequency component in the radial direction, such that the deliberately generated dressing flank modification is wave-shaped with respect to the circumferential direction and has wavefronts in the form of lines of constant phase position, which, when projected onto the annulus, are radially aligned. In other words, in this embodiment, the dressing flank modification has a waviness occurring exclusively in the circumferential direction. In another embodiment, the two-dimensional Fourier series has at least one non-zero Fourier coefficient for a radial frequency component and for a non-zero circumferential frequency component, such thatThe dressing flank modification, projected onto the circular ring, forms a checkerboard-like structure with wave crests and troughs arranged in a checkerboard-like manner. Adjacent wave troughs and wave crests can be offset in such a way that they each form a radial waviness along radial paths running parallel to the radial direction. If the radial wavinesses of adjacent radial paths are offset by exactly 180°, a circumferential waviness is created along circumferential paths running parallel to the circumferential direction, with the circumferential paths being spaced apart from each other in the radial direction by half a radial wavelength of the radial waviness. Such a checkerboard-like structure can be described mathematically as the additive superposition of two partial waves, with the partial waves projected onto the unwound circular ring having oblique wavefronts, i.e. wavefronts that are inclined by an angle of inclination α relative to the unwound circumferential direction.are inclined at an angle unequal to 0°, ±90° or ±180°, wherein the obliquely running wave fronts of the first partial wave have a positive slope (^ > 0°) and the obliquely running wave fronts of the second partial wave have a negative slope (^ < 0°), and wherein the first partial wave has the same order (i.e., the same number of wave periods) in the circumferential direction and the same order in the radial direction as the second partial wave. In a preferred embodiment, the checkerboard-like structure is aligned on the circular ring in such a way that adjacent wave troughs and wave crests in the circumferential direction are arranged along a spiral branch running spirally on the circular ring, wherein the number of wave periods along the spiral branch in an angular coordinate range of 2π (i.e., counted over one revolution of the dressing tool) is referred to in the present context as the order in the spiral branch direction. The checkerboard-like structure can also be aligned in such a wayand / or distorted so that two or more spiral branches occur. Preferably, the transition of the spiral branch or the spiral branches after one rotation of the dressing tool is continuous. Such a structure with spirally running spiral branches can also be described mathematically as an additive superposition of two partial waves, wherein the partial waves projected onto the circular ring have obliquely running wavefronts. If the number of spiral branches is less than twice the order in the spiral branch direction, the structure can be described by means of an additive superposition, in which the obliquely running wavefronts of the first partial wave have a positive gradient and the obliquely running wavefronts of the second partial wave have a negative gradient, wherein the first partial wave has an order in the circumferential direction which is greater by the number of spiral branches than the order in the circumferential direction of the second partial wave. If the number ofSpiral branches greater than twice the order in the spiral branch direction or equal to twice the order in the spiral branch direction, the structure can be described by an additive superposition, in which the obliquely running wave fronts of the first partial wave and the second partial wave either both have a positive or both a negative slope, wherein the first partial wave has an order in the circumferential direction which is twice the order in the spiral branch direction greater than the order in the circumferential direction of the second partial wave. In a further aspect, the present invention provides a method for producing a dressing tool as described above. The method for production comprises: producing a coated base body of the dressing tool in a positive process, and targeted creation of the dressing flank modification by means of a conditioning tool, in particular a dressing flank surface perpendicular to the dressing flank surfacestationary rotating conditioning disk. Preferably, a narrow rotating conditioning disk is used, e.g. a conditioning disk which has a tip rounding on its outer circumference (i.e. a crowning of a lateral surface of the conditioning disk in the axial direction) with a rounding radius which corresponds at most to a quarter of a radial wavelength in the radial direction, wherein the radial wavelength of the wave period corresponds to the waviness in the radial direction. The targeted generation of the dressing flank modifications can in particular comprise: driving the dressing tool to rotate about the dressing axis of rotation; driving the conditioning tool to rotate about a conditioning axis of rotation of the conditioning tool, and advancing the conditioning tool relative to the dressing tool in a direction which has a portion running normal to the dressing flank surface, in order to generate the dressing flank modifications by removing material from theDressing flank surface. Material removal can create a conditioning track in the dressing flank surface, which corresponds to a wave trough and has a width equal to half a radial wave length in the radial direction. However, the width of the conditioning track can also be less than half the radial wave length of the desired dressing flank modification in the radial direction. In such a case, the creation of several adjacent conditioning tracks may be necessary to create a complete wave trough. Instead of a narrow conditioning wheel, the conditioning tool can also have a ribbed outer circumference with at least two conditioning ribs, whereby the conditioning ribs each have a tip rounding with a rounding radius equal to a maximum of one-quarter of the radial wave length in the radial direction, and whereby each conditioning rib can create a conditioning track in the dressing flank surface.In such a case, the conditioning tool can generate several conditioning tracks simultaneously and thus, depending on the number of conditioning ribs, create the entire pattern of dressing flank modifications in a single pass. The orientation of the wave fronts can be adjusted via a kinematic movement of the conditioning tool relative to the dressing tool, as in the case of a conditioning wheel (which corresponds to a conditioning tool with a single conditioning rib). The infeed movement of the conditioning tool relative to the dressing tool can be achieved by a movement of the conditioning tool in space and / or a movement of the dressing tool in space. The infeed movement or the resulting infeed position of the conditioning tool in the direction normal to the dressing flank surface can oscillate at an infeed frequency that is in a predetermined fixed ratio to the rotational frequency of theDressing tool. This allows the material removal along the conditioning track to be varied, resulting in a corresponding waviness along the conditioning track. Depending on the dressing flank modification, the targeted generation of said dressing flank modification can, alternatively or in addition to the oscillating infeed movement, include generating a discontinuous or continuous conditioning axial movement along the conditioning rotational axis. "Continuous" in this context means that the conditioning axial movement is performed while the conditioning tool is in contact with the dressing tool, thus material removal occurs during the conditioning axial movement. "Discontinuous" in this context means that the conditioning axial movement is performed while the conditioning tool is not in contact with the dressing tool, thus no material removal occurs during the conditioning axial movement.takes place. The conditioning axial movement is to be understood as the relative movement between the dressing tool and the conditioning tool along the conditioning axis of rotation. The conditioning tool and / or the dressing tool can be driven to carry out the conditioning axial movement. Depending on the dressing flank modification, the targeted generation of said dressing flank modification can further comprise: generating a plurality of conditioning tracks intersecting at a predetermined angle with the conditioning tool on the dressing flank surface by means of a discontinuous and / or continuous conditioning axial movement along the conditioning axis of rotation, wherein the infeed position of the conditioning tool to the dressing flank surface in the direction normal to the dressing flank surface can have a constant value or wherein the infeed movement or infeed position of the conditioning tool can oscillate at an infeed frequency.For example, a structure can be created in which wave troughs intersect and intermediate material areas of the dressing flank surface form elevations. Depending on the orientation of the intersecting wave troughs on the dressing flank surface, these elevations can be arranged along a spiral branch running spirally on the circular ring. Alternatively, the method for producing the dressing tool can comprise: producing the dressing tool in a negative process, wherein the negative process comprises: producing a negative form by turning a negative base body; turning a targeted negative modification into the turned negative form such that the negative modification effects the dressing flank modification and / or generating a mechanical and / or hydraulic clamping of the negative base body during turning such that the turned negative form, after the mechanical clamping is released, exhibits a negative modificationwhich effects the dressing flank modification. The turning of the targeted negative modification into the turned negative form can be carried out with a suitable machining tool, in particular a turning tool, which is preferably movable along a negative form rotation axis of the negative form relative to the negative form. In particular, the targeted generation of the negative modifications can comprise: driving the negative form to rotate about a negative form rotation axis at a rotational frequency; positioning the turning tool such that it generates a negative track in at least one inner flank of the negative form. In a further aspect, the invention provides a method for dressing a grinding worm for generating pre-toothed workpieces. The method for dressing a grinding worm for generating pre-toothed workpieces comprises: dressing the grinding worm with a dressing tool as described above, such that theDressing flank modification causes a worm modification on a grinding worm flank of a worm thread of the grinding worm. A predefined fixed angle of rotation coupling can exist between the dressing tool and the grinding worm in order to specifically generate a periodic worm modification on the grinding worm flank along the worm thread. In this case, the worm modification represents a compressed image of the dressing flank modification with a constant compression factor, whereby the compression factor depends on the speed ratio between the rotation of the dressing tool and the rotation of the grinding worm. Alternatively, a predefined time-variable angle of rotation coupling can exist between the dressing tool and the grinding worm in order to specifically generate a non-periodic worm modification on the grinding worm flank along the worm thread. In this case, the dressing flank modification is carried out with a non-constantCompression factor mapped into the worm modification. In a further aspect, the invention provides a method for dressing a grinding worm for generating a pre-toothed workpiece, in particular comprising the method described above, comprising: defining a desired worm modification on a grinding worm flank of a worm thread of the grinding worm; calculating the desired worm modification back to a corresponding dressing flank modification of a dressing tool for a selected fixed or variable rotation angle coupling between the dressing tool and the grinding worm; producing the dressing tool having the corresponding dressing flank modifications, in particular with a method as described above; dressing the grinding worm with the dressing tool, with the selected fixed or variable rotation angle coupling, wherein the dressing flank modification along the worm threaddesired worm modification is generated. In a further aspect, the invention provides a method for generating a modified surface structure on a tooth flank of a pre-toothed workpiece. The method for generating a modified surface structure on a tooth flank of a pre-toothed workpiece comprises: dressing a grinding worm suitable for generating pre-toothed workpieces using the method described above; driving the grinding worm to rotate about a worm axis; driving the pre-toothed workpiece to rotate about a workpiece axis; generating a relative movement between the grinding worm and the pre-toothed workpiece in a shift direction parallel to the worm axis ("shift movement") at a shift feed rate, and generating a relative movement between the grinding worm and the pre-toothed workpiece in an axial direction parallel to the workpiece axis ("axialFeed movement") with an axial feed rate, whereby the grinding worm and the pre-toothed workpiece are in rolling engagement and whereby the shift feed rate and the axial feed rate are in a predetermined diagonal ratio such that the worm modification is mapped onto the tooth flank of the pre-toothed workpiece and thereby specifically modifies the surface structure of the tooth flank. The diagonal ratio refers to the ratio of the shift feed rate of the grinding worm in the shift direction to the axial feed rate of the grinding worm in the axial direction parallel to the workpiece axis. The diagonal ratio can be zero or non-zero. If the diagonal ratio is zero, a profile modification occurs on the tooth flank along a height direction of the tooth flank. If the diagonal ratio is non-zero, the resulting modification of the surface structure of the tooth flank can be atopological modification, i.e., a modification that has components in both the height direction and the width direction of the tooth flank. In addition, the method can also comprise generating a relative movement between the grinding worm and the pre-toothed workpiece in a radial direction perpendicular to the workpiece axis ("radial feed movement"). This allows further modifications to be superimposed on the above-described modification of the surface structure of the tooth flank. In the case of a conical workpiece, the radial feed movement and the axial feed movement can be coupled depending on a cone angle of the conical toothing. During generating machining, the worm modification leads to a variation in the penetration depth between the grinding worm and the pre-toothed workpiece and thus generates a tooth flank waviness along a contact track on the tooth flank, wherein the contact track corresponds to a line on whichthe contact point between the grinding worm and the pre-toothed workpiece in rolling engagement moves on the tooth flank during generating machining. If the dressing tool has a checkerboard-like structure that is aligned in such a way that adjacent wave troughs and wave crests in the circumferential direction are arranged along a spiral branch running spirally on the circular ring and thus form a spiral undulation, a fixed angle of rotation coupling can be selected during dressing between the dressing tool and the grinding worm such that the spiral branch is mapped onto a worm contact path on the grinding worm flank, wherein the worm contact path corresponds to a line on which a contact point between the grinding worm and the pre-toothed workpiece in rolling engagement moves on the grinding worm flank during generating machining. Thus, the contact point along the spiral branch on the dressing flank surfaceThe resulting spiral waviness is transferred from the dressing tool via the grinding worm along the contact track to the tooth flank. In some embodiments, the targeted movements of the grinding worm in the shift direction and in the axial direction relative to the pre-toothed workpiece are superimposed with uncontrolled, particularly stochastically occurring additional movements, which lead to uncontrolled variations in the penetration depth. Such uncontrolled additional movements can be caused, for example, by unavoidable vibrations of the generating grinding machine used for generating machining. By specifically varying the penetration depth based on the worm modifications of the grinding worm dressed as described above, a suitable carrier pattern can be created on the tooth flank, which can be made more diffuse by superimposing the uncontrolled variations in the penetration depth, resulting in aOptimization of the noise behavior can lead to. In this way, for example, unavoidable vibrations can specifically contribute to improving the noise behavior. Preferably, the targeted variation of the penetration depth due to the grinding worm dressed as described above has a modulation amplitude which lies in a range between 0.2 times and 5 times a fluctuation measure for the uncontrolled deviations of the penetration depth, wherein the fluctuation measure corresponds in particular to a standard deviation or an interquartile range of the uncontrolled deviations of the penetration depth, in particular, wherein the fluctuation measure of the uncontrolled variations of the penetration depth is determined and the modulation amplitude, and thereby in particular an amplitude of the worm modifications and thereby in turn in particular an amplitude of the dressing flank modifications, is specifically determined depending on the determinedA further aspect of the invention provides a conditioning device comprising: a conditioning tool clamped on a conditioning spindle, in particular a narrow conditioning disk, i.e. a conditioning disk having a tip rounding on its outer circumference with a rounding radius corresponding to at most a quarter of a radial wavelength in the radial direction, wherein the radial wavelength of the wave period corresponds to the waviness in the radial direction; a dressing spindle designed to accommodate a dressing tool for rotation about the dressing axis of rotation; a conditioning control designed to move the conditioning tool relative to the dressing tool such that the dressing tool is provided with the dressing flank modifications as shown above. BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention are described below with reference toof the drawings, which are merely illustrative and are not to be interpreted as limiting. In the drawings: Fig. 1A shows a schematic end view of a dressing tool in a projection plane perpendicular to a dressing rotational axis of the dressing tool; Fig. 1B shows a projection of a dressing flank surface in developed form; Fig. 2 shows a first example pattern of a dressing flank modification; Fig. 3 shows a second example pattern of a dressing flank modification; Fig. 4 shows a third example pattern of a dressing flank modification; Fig. 5 shows a fourth example pattern of a dressing flank modification; Fig. 6A shows a fifth example pattern of a dressing flank modification; Fig. 6B shows a first partial wave pattern for the additive mathematical description of the fifth example pattern of Fig. 6A; Fig. 6C shows a second partial wave pattern for the additive mathematical description of the fifth example pattern of Fig. 6A; Fig. 7A shows a first exemplary arrangement of aSpiral branch on the dressing flank surface; Fig. 7B shows a second exemplary arrangement of two spiral branches on the dressing flank surface; Fig. 7C shows a third exemplary arrangement of three spiral branches on the dressing flank surface; Fig. 7D shows a sixth exemplary pattern of a dressing flank modification with two spiral branches; Fig. 7E shows the sixth exemplary pattern transferred to the projection of the dressing flank surface; Fig. 8A shows a conditioning device according to an embodiment of the present invention; Fig. 8B shows an enlarged cross-sectional view of a section of a conditioning tool with several conditioning ribs; Fig. 9 shows a turned negative mold for producing a dressing tool according to the present invention; Fig. 10A shows a negative mold clamped by means of a deformation device; Fig. 10B shows a relaxed and turned negative mold for producing a dressing tool according to the present invention; Fig. 11 shows a projection of a grinding worm flank of aworm thread of a grinding worm in developed form; Fig. 12 is a schematic view of a generating grinding machine, and Fig. 13 is an enlarged section of Fig. 12. DESCRIPTION OF PREFERRED EMBODIMENTS Dressing tool Fig. 1A shows a schematic end view of a dressing tool 33, wherein the dressing tool 33 has a dressing flank surface 331 which forms a circular ring in a projection plane perpendicular to a dressing rotational axis A of the dressing tool 33, wherein the circular ring defines a radial direction with a radial coordinate r and a circumferential direction with an angular coordinate φ and wherein the circular ring has an inner radius r AIn Fig. 1B, this circular ring, which has a profile height d in the radial direction and a length of 2π in the circumferential direction, is shown schematically in a developed form. Figures 2 - 6A schematically represent, by way of example, various wave-shaped patterns which the deliberately produced dressing flank modifications can have on the dressing flank surface shown in Fig. 1B, with wave crests schematically shown in light shade and wave troughs in dark shade. The following explains how these two-dimensional wave-shaped patterns can be described mathematically. For this purpose, a pattern rectangle with a pattern height Δ^′ in the height direction, which is referred to below as the radial direction, and a pattern length 2π in the longitudinal direction, which is referred to below as the circumferential direction, is used. The patterns can each be described as a two-dimensional real-valued Fourier series f(φ, r′) (iea real-valued Fourier series in two real-valued variables ^ and ^′) as a function of the angular coordinate ^ ∈ [0,2π] and a radial coordinate of the pattern rectangle ^′ ∈ [0, Δ^′]:. where the circumferential frequency components ^ ^ = ^^ ^ is unitless and the radial frequency components ^ ^ = ^^ ^ the unit [1 / mm]. The angular coordinate φ of the pattern rectangle corresponds in this definition to the angular coordinate φ of the previously mentioned circular ring. The radial coordinate ^' of the coordinate system of the pattern rectangle can also be expressed as the radial coordinate ^ in the coordinate system of the circular ring using a linear transformation, e.g., using the relationship ^ = ^ ^ + ^ ^ , where ^ ^ denotes the inner radius of the annulus. The indices ^ ∈ ℤ and ^ ∈ ℤ are integers, whereby the circumferential frequency components ^ ^ or the radial frequency components ^ ^integer ^ multiples of a fundamental frequency = 1 or a radial fundamental frequency ^ ^ = The Fourier coefficients, which indicate the amplitude and phase of the corresponding frequency components, are called ^ ^,^ The Fourier coefficients can generally be written in complex form as ^ ^,^ = ^ ^,^ + ^^ ^,^ = ^ ^,^ ∙ ^ ^^^,^ , where ^ ^,^ the real part, ^ ^,^ the imaginary part, the amplitude and ^ ^,^ is the phase. The complex conjugate coefficient is The imaginary part determines, in particular, the phase position of the pattern. If, as here, a continuous transition is assumed after one revolution of the dressing tool (2π periodicity), the phase position of the pattern in the circumferential direction is irrelevant. Due to the previously chosen definition of the radial fundamental frequency, the pattern repeats periodically in the radial direction with a pattern period of ∆^′. The phase position of the dressing flank modifications ^(^, ^) on the dressing flank surface 331 in the radial direction can be chosen arbitrarily and can be expressed as a corresponding linear coordinate translation from the radial coordinate ^ ^ of the pattern rectangle to the radial coordinate of the dressing flank surface ^ can be expressed, ^ ( ^, ^′ ) → , where the profile height d, over which the dressing flank modifications extend, corresponds to the pattern period ∆^ ^can correspond to, or can be selected to be smaller or larger (since the pattern continues periodically with a pattern period of ∆^′). In other words, this means that any radial section of the periodic example patterns mathematically described below can be applied to the dressing tool as a dressing flank modification. Thus, the phase position of the pattern on the pattern rectangle is irrelevant and, for a simplified description, the Fourier coefficients ^ ^,^ and ^ ^^,^^ complex conjugate, ie ^ ^,^ = ^^ ^ ^^ ^ ^ , ^ ^ ^^ ^ ^ = ∙ ^ ^^^,^. Figuratively speaking, the dressing flank modification can be described as a section of a wave-shaped pattern on the pattern rectangle or a superposition of two or more wave-shaped partial patterns on the pattern rectangle, whereby each of these wave-shaped partial patterns can exhibit periodic waviness in the radial direction and / or in the circumferential direction. It should be noted that only the absolute phase position of the resulting pattern is irrelevant. If several wave-shaped partial patterns are superimposed to describe the resulting pattern, the relative phase position of the partial patterns to one another is relevant. The number of wave periods on the pattern rectangle in the radial direction is referred to below for each of these wave-shaped patterns / partial patterns as the order in the radial direction N and the number of wave periods in the circumferential direction as the order in the circumferential direction M. One wave period in the radial direction has a radial wavelength ^ ^^and a wave period in the circumferential direction is expressed in the following context as an offset angle ∆φU ("wavelength in the circumferential direction"). Since the circumferential fundamental frequency ^ ^ = 1, the order in the circumferential direction M corresponds to the index value | ^ | , and since ^ the radial fundamental frequency ^ ^ = was selected, the order in the radial direction N corresponds to the index value |^|. In the embodiment shown in Fig. 2, the pattern has wavefronts in the form of lines of constant phase, with the wavefronts projected onto the unwound annulus forming continuous, straight lines. These lines are, as shown in Fig. 2, inclined relative to the unwound circumferential direction by an inclination angle α and offset in the circumferential direction by an offset angle Δφ Uspaced from each other. In order to ensure that the pattern of the dressing flank modification can be continued periodically after one revolution, only discrete values ​​for the inclination angle α are possible, ie ^ = ± arctan where ^ ^ ∈ ℕ, where the lines of constant phase for ^ < 0° have a negative slope (ie, they run from top left to bottom right on the pattern rectangle as in Fig.2) and where the lines of constant phase for ^ > 0° have a positive slope (ie, they run from bottom left to top right on the pattern rectangle). If the lines of constant phase have a negative slope, the following frequency component pairs {^ ^ , ^ ^} a Fourier coefficient not equal to zero: and { ^ ^^^^ , ^ ^^^^ } If, however, the line of constant phase has a positive slope, the following frequency component pairs have a Fourier coefficient not equal to zero: and{ ^ ^^^^ , ^ ^^^^ } The waveform does not necessarily have to be a pure sinusoidal shape, therefore other Fourier coefficients can also be non-zero. In particular, the higher harmonics of the above-mentioned Fourier coefficients can be non-zero, i.e. the Fourier coefficients for which ^ is an integer multiple of ^ and ^ is an integer multiple of ^. In this case, the relative phase angles of the higher harmonics with respect to the lowest frequency must be taken into account, as this has a decisive influence on the resulting pattern. The following table summarizes the parameters of the dressing flank modification from Fig. 2: Direction Wavelength Order Frequency component pairs with Fourier coefficient ≠ zero ∆ In radial direction ^ ∆^′ ^′ ^ ^ = ^ = ^ 5 ^ ^^ = 5 ^^^ = ^ ^^ , ^ ^ = 5^ ∆^ 2^ ^ ^ ^ = − , ^ = −5^ In circumferential direction ∆φ ^ ^^ ^ = = ^ = 5^ ^^ ^^ 5 5 Specifically, the following applies to the pattern in Fig.2: ^ ^,^ = ^^ ^ ^^ ^ ^ , ^ ^ ^ ^ ^ ≠ 0, while all other Fourier coefficients are zero. In Fig.3, the inclination angle α is exactly 90°, meaning that the wavefronts of the dressing flank modification, projected onto the annulus, are radially aligned. This case corresponds to a complex Fourier series, which has no non-zero coefficient for a radial frequency component ^ ^not equal to zero in the radial direction. The dressing flank modification shown here is continuous in the circumferential direction, ie the wave-shaped dressing flank modification has an integer number of wave periods related to a single revolution of the dressing tool (2π periodicity). The following table summarizes the parameters of the dressing flank modification from Fig. 3: Direction Wavelength Order Frequency component pairs with Fourier coefficients ≠ zero In the radial direction ∞ ^ = 0 {^ ^ = 0 , ^ ^ = 4} I n Umfangrichtung ∆φ ∆^ ^ 2^ ^ = = ^ = 4 {^ ^ = 0 , ^ ^^ = −4} 4 4 Specifically, the pattern in Fig.3 applies: ^ ^,^ = ^^ ^ ^ , ^ ^ ^ ^^ ≠ 0, while all other Fourier coefficients are zero. In Fig. 4, the inclination angle α is exactly 0°, ie the wavefronts extend straight parallel to the circumferential direction and form a radial ripple with a radial wavelength λ in the radial direction. r This case corresponds to a complex Fourier series which has no non-zero coefficient for a circumferential frequency component ^ ^ not equal to zero in the circumferential direction. The following table summarizes the parameters of the dressing flank modification from Fig.4: Direction Wavelength Order Frequency component pairs with Fourier coefficients ≠ zero ∆^ ^ In the radial direction ^ ∆^′ ′ ^ ^ = ^ = = 4 ^ , ^ = 0^ 4 ^ ^^ ^ ^ = ^ ^^ ^ ^ ^ ^ ^^ = − , ^ ^ = 0^ In circumferential direction ∞ ^ = 0 ^ ^^Specifically, for the pattern of Fig.4: ^ = ≠ 0, while all other Fourier coefficients are zero. In the embodiment shown in Fig.5, the two-dimensional complex Fourier series has a coefficient not equal to zero for a radial frequency component ^ ^ non-zero and for a circumferential frequency component ^ ^ not equal to zero, such that the wave-shaped dressing flank modification, projected onto the unwound circular ring, forms a checkerboard-like structure with offset wave crests and troughs. Mathematically, the pattern in Fig. 5 can be described as an additive superposition of a first partial wave ^ ^^ (^, ^′), and a second partial wave ^ ^^ (^, ^′) can be described, ^ ( ^, ^′ ) = ^ ^^ ( ^, ^′ ) + ^ ^^ ( ^, ^′ ), wherein the first partial wave and the second partial wave have the same order M in the circumferential direction and the same order N in the radial direction, but the lines of constant phase position have a negative gradient in the first partial wave and a positive gradient in the second partial wave. In Fig.5, adjacent wave troughs and wave crests are offset from one another and thus each form a radial ripple along radial paths R1, R2 running parallel to the radial direction. The radial ripples of adjacent radial paths are offset by exactly 180° in the example shown in Fig.5, whereby each form a circumferential ripple along circumferential paths U1, U2 running parallel to the circumferential direction, wherein the circumferential paths U1, U2 are offset by half the radial wavelength ^ ^^ / 2 in the radial direction. The following table summarizes the parameters of the dressing flank modification from Fig.5: Direction Wavelength Order Frequency components with Fourier coefficients ≠ zero Partial wave 1: direction ^ ∆^ ∆^′ In Radial ′ ^ ^,^^ = ^ = ^ 4 ^^ ^ ^^,^^ = 4 ^^^ = ^ ^^,^^ , ^ ^ = 4 ^ ∆^ ^ In circumferential direction ∆φ^,^^ = ^2^ = ^ = 4 ^^ ^^ = − 4 4 ^^ ^ ^^,^^, ^^^ = −4^Partial wave 2: ∆^′ In radial direction ^ ∆^′ ^ ,^^ = ^ ^^ = ^ = 4 ^^ ^ ^ = , ^ ^^ = −4 ^ 4 ^^,^^ ^ ^^,^^ In circumferential direction ∆φ ^1 ∆^ 2^ ^^ ^^ ^,^^ = = − = ^, ^^ = 4 ^4 4 ^^ = 4 ^ ^^,^^ Specifically, the pattern in Fig.5 applies: ^ ^,^ = ^^ ^ ^^ ^ ^ , ^ ^ ^ ^ ^ ≠ 0 and ^ ^,^^ = ^^ ^ ^^ ^ ^ ,^^ ≠ 0 while all other Fourier coefficients are zero. Fig.6A shows a spiral pattern that can be mathematically described as an additive superposition of a first partial wave ^ shown in Fig. 6B ^^ ( ^, ^′ ) , and a second partial wave shown in Fig. 6C ^ ^^ ( ^, ^′ ) , can be described as: Compared to Fig. 5, the radial wavinesses of the adjacent radial paths R1, R2 in Fig. 6A are offset from each other by a value other than 180°, whereby adjacent wave troughs and wave crests in the circumferential direction are arranged along a spiral branch S1 running spirally on the circular ring, thus forming a spiral waviness. The number of wave periods along the spiral branch S1 is referred to below as the order in the spiral branch direction L. The pitch of a spiral branch over one revolution of the dressing tool depends on half the radial wavelength ^ ^^ / 2 and the number of spiral branches ^ ^ ∈ ℕ ^ . The spiral branches form straight lines on the unwound circular ring that are inclined relative to the circumferential direction, whereby the angle of inclination α (analogous to the situation in Fig.2) can be expressed as: To ensure that the dressing flank modification pattern can be continued periodically after one revolution, only discrete values ​​for the pitch are possible. The pattern can always be continued periodically if the pitch is a multiple of half the radial wavelength ^ ^^ / 2. In order to ensure a continuous transition of the spiral branch after one rotation of the dressing tool, two cases must be distinguished: 1. The freely selected order in the spiral branch direction L is an integer: In this case, the pitch height of the spiral branch must be an even multiple of half the radial wavelength ^ ^^ / 2, ie the number of spiral branches ^ ^is even. 2. The freely chosen order in the spiral branch direction L is half-integer: In this case, the pitch of the spiral branch must be an odd multiple of half the radial wavelength ^ ^^ / 2, ie the number of spiral branches ^ ^ is odd. In Fig.6A, the order in the spiral branch direction is L= 5.5 and the pitch is exactly ^ ^^ / 2, since there is exactly one spiral branch, ie ^ ^ = 1. In order to obtain a certain order L for the spiral waviness in the spiral direction, the order of the waviness in the circumferential direction ^ ^,^ the first partial wave and for the order of the waviness in the circumferential direction ^ ^,^ the second partial wave ^ ^^ ( ^, ^′ ) apply: ^ ^ ^,^ = ^ + ^ 2 ^ ^ ^,^ = ^ ^ − ^^ 2 where, if holds, the second partial wave has a pitch with a sign that is opposite to the sign of the pitch of the first partial wave. If − ^^ ≥ 0, the second partial wave has a pitch with the same sign as the first partial wave. The following table summarizes the parameters of the dressing flank modification from Fig. 6A: Wavelength Order Frequency component pairs with Fourier coefficients ≠ zero Partial wave 1: ∆^′ In radial direction ^ ^^,^^ = ∆^′ ^ ^^ = = 1 ^ ^^,^^ ^ ^ ^^ = ^ ^^,^^ , ^ ^ = 6 ^ ∆^ I n Umfangrichtung ∆φ ^ ^,^^ = 6 ^ = 6 ^ ^ ^ ^^ = − ^ ^^ , ^ ^^ = −6^ 2^ ^^ ,^^ = 6 Partial wave 2: I n Radialrichtung: ^ ∆^′ ^^,^^ = ∆^′ ^^^ == 1 ^ ^^,^^ ^ ^ ^ ^ = ^ ^^,^^ , ^ ^^ = −5^ ∆^ I n Umfangrichtung ∆φ ^ ^,^^ = ^ 5 ^ = 5 ^ ^ ^^ = − ^ ^^,^ , ^^ = 5^ 2^ ^^^ = 5 The first partial wave ^ ^^ ( ^, ^′ ) has wavefronts that have a negative slope (Fig.6B), while the second partial wave ^ ^^ ( ^, ^′ ) wavefronts that have a positive slope (Fig.6C). Specifically, for the pattern in Fig.6A, the following applies: ^ = ^^ ^ ^^ ^ ^ , ^ ^ ^ ^ ^ ≠ 0 and ^ ^,^^ = ≠ 0 while all other Fourier coefficients are zero. Figures 7A-7C schematically show how the spiral branches can be arranged on the dressing flank surface 331 of the dressing tool 33. Fig.7A shows an example in which exactly one spiral branch S1, ie ^ ^ = 1, is formed on the dressing flank surface 331. In Fig. 7B, two spiral branches S1,S2 are formed on the dressing flank surface 331, ie ^ ^= 2, wherein the spiral branches S1,S1 are offset by an offset angle ∆φ in the circumferential direction, which in this example is π. In Fig.7C, three spiral branches S1,S2,S3 are formed, wherein the spiral branches S1,S2,S3, ie ^ ^ = 3, here offset by an angle ∆φ in the circumferential direction, which is 2π / 3. Figures 7D and 7E illustrate another example pattern using concrete numbers. In this example, the number of spiral branches is ^ ^ = 2, the radial wavelength ^ ^^ = 15 mm, the pattern period is ∆^ ^ = 30 mm, the order in the spiral branch direction is L = 50, and the spiral branches S1, S2 run counterclockwise. The spiral waviness has an amplitude of ^ = 3.5 µm. Thus, the orders of the waviness in the circumferential direction of a first partial wave 1 and a second partial wave 2 are calculated using the following equations: Partial wave 1: ^ ^,^ = 1 + ^ = 51 Partial wave 2: ^ ^,^ = | 1 − ^| = 49 The order in radial direction is: ∆^^ Partial wave 1: ^ ^,^ = ^ ^^ = 2 ∆^^ Partial wave 2: ^ ^,^ = ^ ^^ = 2 The non-zero Fourier coefficients, in this case real Fourier coefficients, are thus: ^ 3.5 µm ^ ^^,^^^ = ^ ^^,^^^ = ^ ^^,^^^ = ^ ^^,^^^ = = = 0.875 µm 4 4 The checkerboard waviness can be described with the following equation: = + About the relationship (2 ∙ cos ( ^ ) = ^ ^^ + ^ ^^^ ) can be f ( φ, r′ ) also convert into a real notation: ^ ( ^, ^′ ) = 2 ∙ 0.875 The pattern ^ ( ^, ^′ ) according to this formula with the two spiral branches S1,S2 is shown in Fig. 7D. In Fig. 7E, a section of the pattern from Fig. 7D is shown as a dressing flank modification projected onto the circular ring, with the pattern extending over a profile height d< ∆^ ^ with d = 20 mm and where: = ^ ( ^, ^ ^ + ^ ^ ) with ^ ^= 30 mm. Production of the dressing tool. Dressing tools with the dressing flank modifications explained above can be produced using both a positive process and a negative process. Positive process. In the positive process, a base body, preferably made of steel, is provided, which is coated with hard material particles, typically diamond particles, preferably by electroplating. Methods for producing a base body with a hard material particle coating using the positive process are known from the prior art, for example from publications EP 2535145 A2 and EP 2835220 A1, the disclosures of which are incorporated herein by reference in their entirety. Fig. 8A schematically shows a conditioning device 50 according to an embodiment of the present invention.The conditioning device comprises a dressing tool 33 (here in sectional view), wherein the base body 330 has a hollow cylinder which can be clamped onto a dressing spindle 32 and driven to rotate about the dressing axis of rotation A. A circular disk extends around the hollow cylinder with dressing flanks tapering to a point in the radial direction relative to the dressing axis of rotation A. The hard material particles applied to the dressing flanks form the dressing flank surface 331. In order to provide the dressing flank surface 331 with dressing flank modifications, the dressing flank surface is machined with a conditioning tool 51.In the example schematically illustrated here, this conditioning tool 51 is a narrow conditioning disk which is rotatable about a conditioning axis of rotation K running parallel to the dressing flank to be machined and is movable in a direction normal to the dressing flank surface 331 and parallel to the conditioning axis of rotation K. The conditioning disk preferably has an abrasive coating with bonded hard material particles which have a comparable or higher hardness than the hard material particles of the dressing tool coating. In order to produce the dressing flank modifications, the dressing tool is driven to rotate about the dressing axis of rotation A, while the conditioning tool 51 is driven to rotate about the conditioning axis of rotation K. The rotating conditioning disk is then advanced such that it comes into contact with the dressing flank surface 331, thereby removing material from the dressing flank surface 331.In the example shown in Fig.8A, the infeed movement takes place parallel to a normal of the dressing flank surface 331. The infeed movement of the conditioning tool 51 or the resulting infeed position perpendicular to the dressing flank surface can oscillate with an infeed frequency fK which is matched to a rotational frequency of the dressing tool fA in order to generate the desired waviness, while in addition a discontinuous or continuous conditioning axial movement can take place along the conditioning rotational axis K. In order to obtain a wave-shaped dressing flank modification of the desired order in the circumferential direction M, the following applies in particular: ^. ^ = ^^ ^ The conditioning device comprises a conditioning control 53, which is designed to control the rotational frequency of the dressing tool and the delivery frequency f Kto coordinate with each other, as well as to control the feed movement of the conditioning tool 51 relative to the dressing tool 33. Instead of a narrow conditioning disk, the conditioning tool 51 can also have a ribbed outer circumference. Fig. 8B shows, by way of example, an enlarged section of a cross-section through a conditioning tool 51 having three conditioning ribs 511, wherein the conditioning ribs 511 each have a tip rounding with a rounding radius which corresponds to a quarter of the radial wavelength in the radial direction λr', and wherein each conditioning rib 511 can each produce a conditioning track in the dressing flank surface. Examples: The production of the dressing flank modifications shown as examples in Figures 2-6A is explained below. Production of the dressing flank modification of Fig.2: The wave fronts on the unwound circular ring, which are inclined by the angle of inclination α relative to the circumferential direction, can be generated as follows: Feeding the conditioning tool in the direction normal to the dressing flank surface to a constant feed value; generating a continuous conditioning axial movement of the conditioning tool at a constant axial speed along the conditioning rotational axis K for at least one revolution of the dressing tool 33. The continuous conditioning axial movement can occur either from the inside out or from the outside in with respect to the radial direction of the dressing tool 33. An increase in the desired angle of inclination α is accompanied by an increase in the constant axial speed at a constant rotational frequency fA of the dressing tool. For the dressing tool shown in Fig.2 concrete example, in which the angle of inclination α is chosen such that the wave fronts projected onto the unwound circular ring have a gradient with an amount of ∆r' / 2π, the axial velocity must therefore be for a fixed value of the rotational frequency. of the dressing tool a velocity component projected onto the radial direction of the dressing tool of ^ ^ = ∆^′^ ^ In the example shown in Fig.2, a conditioning track is created in the dressing flank surface per revolution of the dressing tool, running diagonally over the entire length of the unwound circular ring. This conditioning track corresponds to a wave trough (dark shaded in Fig.2) and thus has a width that is half the radial wave length ^ ^^ / 2. In order to create the further wave troughs shown in Fig. 2, the conditioning tool is repositioned after each rotation of the dressing tool, but in relation to the unwound circular ring around the circumferential wave length ∆φ Ushifted in the circumferential direction. If a conditioning tool 51 with multiple conditioning ribs 511 is used, so that all desired conditioning tracks are generated in a single rotation, the repositioning of the conditioning tool 51 can also be omitted. Creating the dressing flank modification of Fig. 3: In Fig. 3, the wave-shaped dressing flank modification has wave fronts that are projected radially onto the circular ring. To create this dressing flank modification, the infeed position of the conditioning tool oscillates normal to the dressing flank surface at an infeed frequency fK that is matched to the rotational frequency fA of the dressing tool, with no conditioning axial movement along the conditioning rotational axis K occurring during this time. To obtain a wave-shaped dressing flank modification of the desired order in the circumferential direction M, the following relationship must be satisfied: ^ ^ = ^^ ^The conditioning tool 51 thus creates a conditioning track running in the circumferential direction with a corresponding waviness of order M. Depending on the profile height d of the circular ring over which the dressing flank modification is to extend and depending on the width of the individual conditioning track, the conditioning tool must be repositioned at a plurality of different positions along the conditioning rotation axis K. In order for conditioning tracks running adjacent in the radial direction to form continuous, radially rectilinear wave fronts, it must be ensured when positioning the conditioning tool at the new position that the oscillating feed movement of the conditioning tool has a phase position which is synchronized with the rotation of the dressing tool 33 in such a way that the waviness of the new conditioning track is in phase with the waviness of the previously created conditioning track.Alternatively, it is also conceivable to generate a continuous axial conditioning movement of the conditioning tool at a constant axial speed along the conditioning axis of rotation K, instead of repositioning the conditioning tool along the conditioning axis of rotation after each rotation of the dressing tool. However, in order to form wave fronts that are essentially straight in the radial direction, the axial speed must be selected such that the conditioning tool, after one rotation of the dressing tool along the conditioning axis of rotation K, has traveled a distance that corresponds at most to the width of the conditioning track. Creating the dressing flank modification shown in Fig. 4: The dressing flank modification shown in Fig.The dressing flank modification shown in Fig. 4 can be created by advancing the conditioning tool to a constant infeed value in the direction normal to the dressing flank surface, whereby (in contrast to the creation of the dressing flank modification in Fig. 2) no continuous conditioning axial movement takes place along the conditioning axis of rotation K, thereby creating a conditioning track running parallel to the circumferential direction. After at least one rotation of the dressing tool, the conditioning tool is repositioned at a plurality of different positions along the conditioning axis of rotation K to create adjacent new conditioning tracks in the radial direction, thereby generating wave fronts which, projected onto the developed circular ring, extend in a straight line parallel to the circumferential direction.If a conditioning tool 51 with several conditioning ribs 511 is used, so that all desired conditioning tracks are created in a single rotation, the re-attachment of the conditioning tool 51 can also be omitted. Creating the dressing flank modification of Fig. 5: The dressing flank modification shown in Fig. 5 can be created by superimposing the steps required to create the dressing flank modification shown in Fig. 3 and Fig. 4: To create the dressing flank modification shown in Fig. 5, the infeed position of the conditioning tool oscillates normal to the dressing flank surface at an infeed frequency fK that is matched to the rotational frequency fA of the dressing tool, whereby no conditioning axial movement along the conditioning rotational axis K takes place.In order to obtain a wave-shaped dressing flank modification of the desired order in the circumferential direction M, the following relationship must be fulfilled: ^. ^ = ^^ ^ The conditioning tool 51 thus produces a conditioning track running in the circumferential direction with a circumferential waviness of order M. The conditioning tool 51 is, after one rotation of the dressing tool 33, at a plurality of different positions along the conditioning rotation axis K to produce adjacent new conditioning tracks in the radial direction with a respective width of half a radial wavelength ^ ^^ / 2 is reattached. This creates the circumferential waviness along circumferential paths U1, U2 running parallel to the circumferential direction. The oscillating feed movement of the conditioning tool has a phase position which is synchronized with the rotation of the dressing tool 33 in such a way that the resulting circumferential wavinesses are shifted by 180° relative to one another. If a conditioning tool 51 with several conditioning ribs 511 is used, so that all desired conditioning tracks are created in a single rotation, the reattaching of the conditioning tool 51 can also be omitted. Creating the dressing flank modification of Fig. 6A: To create the dressing flank modification shown in Fig. 6A, as in the case of the dressing flank modification in Fig.2, also generates a continuous conditioning axial movement of the conditioning tool along the conditioning rotational axis K over at least one revolution of the dressing tool 33 at a constant axial speed, however, the conditioning tool is not advanced to a constant infeed value in the direction normal to the dressing flank surface (in contrast to the situation in Fig.2), but the infeed position of the conditioning tool oscillates instead normal to the dressing flank surface with an infeed frequency f. K , which affects the rotation frequency of the dressing tool f AThis results in a dressing flank modification in which adjacent wave troughs and wave crests are arranged in the circumferential direction along the spiral branch S1, which runs spirally on the circular ring, with the spiral branch S1 forming a straight line on the unwound circular ring that is inclined relative to the circumferential direction. To obtain a wave-shaped dressing flank modification of the desired order in the spiral branch direction L, the following relationship must be fulfilled: To create additional spiral branches S2, S3…, the conditioning tool is repositioned after each spiral branch has been created, but is shifted in the circumferential direction φ relative to the unwound circular ring by an offset angle Δφ. In a preferred variant, the offset angle Δφ is selected such that the following relationship is satisfied: ^ ^ ∆φ = 2π, where ^ ^represents the number of spiral branches. If a conditioning tool 51 with several conditioning ribs 511 is used, so that all desired conditioning tracks are created in a single rotation, the repeated attachment of the conditioning tool 51 can also be omitted. The steps used to create the examples explained can, of course, be combined to create further dressing flank modifications not explicitly illustrated here. In particular, patterns are also conceivable in which continuous wave troughs intersect at any predetermined angle. Purely radially aligned wave troughs can, for example, intersect wave troughs aligned purely in the circumferential direction at an angle of 90° projected onto the circular ring. Alternatively, the intersecting wave troughs can also run obliquely across the dressing flank surface. The rotational frequency of the dressing tool and / or the feed frequency fK of the conditioning tool and / or the conditioning axial movement can be varied over time during machining in order to produce targeted dressing flank modifications that have more complex patterns. Negative process Dressing tools with the dressing flank modifications explained above can alternatively also be manufactured using a negative process. For this purpose, a negative base body, preferably made of aluminum or graphite, is provided, which is turned into a negative form of the desired dressing tool using a turning tool. Negative processes for producing dressing tools are known from the prior art, for example from the publication EP 1110671 A2, the disclosure of which is incorporated herein by reference in its entirety.In order to obtain the desired dressing flank modifications on the dressing flank surface 331, a corresponding negative modification can be specifically turned into the negative mold. Fig. 9 shows a schematic sectional view of a negative mold 60, wherein the negative mold 60 is mounted so as to be rotatable about a negative mold rotation axis D and has inner flanks 61 which taper radially outwards with respect to the negative mold rotation axis D. Fig. 9 schematically shows a turning tool 70 which is introduced into the negative mold 60 and which has a turning tool tip 71 which projects radially with respect to the negative mold rotation axis D and with which material is removed from the inner flanks 61 to produce the negative modifications, while the negative mold rotates at a rotation frequency f. Nrotates around the negative mold rotation axis D. By superimposing an axial movement of the turning tool tip 71 along the negative mold rotation axis D and a radial movement with respect to the negative mold rotation axis D, the turning tool tip 71 can be moved along the entire at least one inner flank 61. By performing the axial movement of the turning tool tip 71 along the negative mold rotation axis D with a turning tool frequency f Doscillates (as shown schematically in Fig. 9 by a sine curve), negative tracks are rotated into the negative mold, which have a circumferential waviness in the circumferential direction, corresponding to a negative imprint of the desired dressing flank modification of the dressing tool produced using this negative mold. The rotational frequency fN of the negative mold and the turning tool frequency fD can each be constant over time, but can also be varied over time. Analogous to the previously explained examples for directly machining the dressing flanks with a conditioning tool, all of the dressing flank modifications shown as examples in Figures 2-6A, as well as further modifications thereof, can be produced by appropriate superposition of the axial and radial movements of the turning tool tip 71 with respect to the negative mold rotational axis D, as well as by appropriate synchronization with the rotation of the negative mold 60.The turning tool frequency fD and / or the rotational frequency fN of the negative mold and / or an axial and / or radial feed movement of the turning tool tip along the inner flank 61 can be varied over time during machining in order to produce targeted dressing flank modifications that have more complex patterns. Alternatively or additionally, the targeted production of the negative modifications can also include a targeted production of tension in the negative mold, as will now be explained with reference to Figures 10A and 10B. Figure 10A shows a schematic sectional view of the negative mold 60 with the turning tool 70, wherein in this embodiment a deformation device 80 is attached to the negative mold 60 and tensions it. In the example shown here, the deformation device 80 exerts a force on the negative mold 60 in the axial direction with respect to the negative mold rotation axis D, such that it is slightly compressed.As a result, regions of the inner flanks 61 are pressed axially closer together. If these regions of the inner flanks 61, which are pressed together, pass the fixed turning tool tip 71 during the rotation of the negative mold, greater material removal takes place in the regions pressed together than in other regions of the negative mold 60 that are not pressed together by the pre-forming device 80. The deformation device 80 preferably has force application regions arranged periodically in the circumferential direction of the negative mold. To generate the force on these force application regions, the deformation device 80 can, for example, have mechanical or hydraulic bracing elements. In particular, the force can be exerted directly on the force application region by a screw. Likewise, the force on the force application region can be generated by a hydraulic piston.Alternatively or additionally, the deformation device can comprise a two-part device which at least partially encompasses the negative mold and is held together by screws and / or hydraulic pistons. In a relaxed state (Fig. 10B), the negative mold then has a negative track with circumferential waviness, with wave troughs occurring in the negative mold where a force has been applied by the deformation device 80. These wave troughs in the negative mold 60 then correspond to the wave crests on the dressing flank surface of the dressing tool produced using this negative mold. The use of a deformation device can of course also be combined with the use of a turning tool center 71 moved relative to the negative mold to produce any desired negative modification / dressing flank modification.Dressing the grinding worm The invention also includes a method for dressing a grinding worm 16 for the generating machining of pre-toothed workpieces, in which method the dressing modifications of the dressing tool 33 are projected onto a grinding worm flank 161 of the grinding worm, whereby a worm modification is generated on the grinding worm flank 161. The dressing tool 33 and the grinding worm flank 161 are in line contact. Fig. 11 shows a circular projection of a grinding worm flank 161 in a plane perpendicular to a worm rotation axis B in developed form, wherein the circular projection has a worm circumferential direction with a worm circumferential coordinate φ. S and a screw radial direction with a screw radial coordinate r Sdefined. On the developed grinding worm flank 161, worm modifications in the form of three spiral branches S1', S1'', S1''' are schematically shown, whereby the three spiral branches S1', S1'', S1''' on the grinding worm flank 161 correspond to the same spiral branch S1 on the dressing flank surface 331, which, however, was transferred to the grinding worm flank 161 with different speed ratios between the dressing tool 33 and the grinding worm. The dashed arrow shown in Fig. 11 points in the direction of an increasing speed ratio between the dressing tool 33 and the grinding worm: the greater the said speed ratio, the steeper the depicted spiral branch S1', S1'', S1''' runs on the developed grinding worm flank 161.The worm modification created by transferring the dressing flank modification to the grinding worm flank 161 has a number of wave periods relative to one rotation of the grinding worm, whereby this number is referred to here as the worm waviness order LS. By varying the speed ratio between the dressing tool 33 and the grinding worm, this worm waviness order LS can be influenced: the greater the said speed ratio, the greater the worm waviness order LS. Typically, the speed ratio is between 10 and 60.The speed ratio can be constant over time or changed during dressing of the grinding worm. In such a case, the spiral branch S1' shown no longer forms a straight line on the unwound grinding worm flank, but is kinked (in the case of an abrupt change in the speed ratio) or curved (in the case of a continuous change in the speed ratio). Depending on the pitch of the spiral branch S1 on the dressing flank surface 33 and the profile height d over which the spiral branch S1 extends on the dressing flank surface 33, several revolutions of the dressing tool are required to map the entire spiral branch S1 onto the grinding worm flank 161: the flatter the pitch, the more revolutions are required.Thus, a desired worm modification can be defined on a grinding worm flank 161 of a worm thread of the grinding worm 16, which can be recalculated to a corresponding dressing flank modification for a selected fixed speed ratio between the dressing tool 33 and the grinding worm. The corresponding dressing flank modification can then be specifically produced according to the manufacturing processes described above. Creating a targeted tooth flank modification on a pre-toothed workpiece. The worm modifications produced by the dressing tool as explained above can be transferred to a tooth flank of a pre-toothed workpiece in a generating machining process. The generating machining process is carried out on a generating grinding machine 1, which is shown as an example in Fig. 12 and which is also referred to below as the "machine."The machine 1 has a machine bed 11 on which a tool holder 12 is guided so as to be displaceable along a radial feed direction X. The tool holder 12 carries an axial slide 13 which is guided so as to be displaceable relative to the tool holder 12 along a feed direction Z. A grinding head is mounted on the axial slide 13 and can be pivoted about a pivot axis running parallel to the X direction (the so-called A axis) in order to adapt to the helix angle of the gear to be machined. The grinding head, in turn, carries a shift slide 14 on which a tool spindle 15 can be displaced relative to the grinding head along a shift direction Y. A helically profiled grinding wheel (grinding worm) 16 is clamped on the tool spindle 15. The grinding worm 16 is driven by the tool spindle 15 to rotate about a worm axis B.The machine bed 11 further supports a pivotable workpiece carrier 20 in the form of a turret, which can be pivoted about a pivot axis C3 between at least three positions. Two identical workpiece spindles are mounted diametrically opposite one another on the workpiece carrier 20, of which only one workpiece spindle 21 is visible in Fig. 1. A workpiece can be clamped onto each of the workpiece spindles and driven to rotate about a workpiece axis. The workpiece spindle 21 visible in Fig. 1 can be driven about the workpiece axis C1 and is in a machining position in which a workpiece 23 clamped thereon can be machined with the grinding worm 16. The other workpiece spindle, offset by 180° and not visible in Fig. 1, is in a workpiece change position in which a finished workpiece can be removed from this spindle and a new blank can be clamped onto it.A dressing device 30 is mounted offset by 90° to the workpiece spindles. Machine 1 thus has a multitude of movable components such as slides or spindles, which can be moved under the control of corresponding drives. These drives are often referred to in the technical world as "NC axes," "machine axes," or simply "axes." This term sometimes also includes the components driven by the drives, such as slides or spindles. Machine 1 also has a multitude of sensors. For example, only two sensors 18 and 19 are schematically indicated in Fig. 12. Sensor 18 is a vibration sensor for detecting vibrations of the housing of grinding spindle 15. Sensor 19 is a position sensor for detecting the position of axial slide 13 relative to tool carrier 12 along the Z-direction. In addition, machine 1 comprises a multitude of other sensors.These sensors include, in particular, additional position sensors for detecting the actual position of a linear axis, angle sensors for detecting the rotational position of a rotary axis, current sensors for detecting the drive current of a rotary axis, and additional vibration sensors for detecting vibrations of a driven component. All driven axes of machine 1 are digitally controlled by a machine control system 40. Machine control system 40 comprises several axis modules 41, a control computer 42, and an operator panel 43. Control computer 42 receives operator commands from operator panel 43 as well as sensor signals from various sensors of machine 1 and uses these to calculate control commands for axis modules 41. It also outputs operating parameters to operator panel 43 for display. The axis modules 41 each provide control signals for a machine axis at their outputs.A monitoring device 44 is connected to the control computer 42 and performs various monitoring tasks during operation of the machine 1. Fig. 13 shows an enlarged section of Fig. 1. The dressing device 30 is particularly clearly visible here. A dressing spindle 32 is arranged on a swivel drive 31 and can be pivoted about a swivel axis C4. A disk-shaped dressing tool 33 is clamped on said spindle. The dressing tool is provided with specifically produced dressing flank modifications. In a helical gear drive, as is the case with a pairing of an externally toothed spur gear (the pre-toothed workpiece 23) and the grinding worm, point contact occurs when the axes of the pre-toothed workpiece 23 and the grinding worm 16 are not parallel.As the pairing is rolled, the contact point moves along a path geometrically determined by the pairing, each over the tooth flank of the pre-toothed workpiece 23 and over the grinding worm flank 161 of the grinding worm 16. In the present context, the path on the tooth flank is referred to as the contact track, and the path on the grinding worm flank is referred to as the worm contact path. In one embodiment of the method for producing a modified surface structure on a tooth flank of a pre-toothed workpiece 23, the grinding worm 16 is first dressed using a dressing method described above with a dressing tool 33 having a spiral waviness along a spiral branch S1.The speed ratio between the dressing tool 33 and the grinding worm is selected such that the spiral waviness is mapped exactly along the worm contact path, which is predetermined by the pairing between the pre-toothed workpiece 23 to be machined and the grinding worm 16. In other words, the speed ratio is selected such that the spiral branch S1' mapped onto the grinding worm flank 161 lies on the worm contact path. This worm modification in the form of a worm waviness along the spiral branch S1' is then specifically transferred to the tooth flank of the pre-toothed workpiece 23: For this purpose, the grinding worm 16 is driven to rotate about the worm axis B, while the pre-toothed workpiece 23 is driven to rotate about the workpiece axis C1, whereby the grinding worm and the pre-toothed workpiece are in rolling engagement.In addition, both a movement of the grinding worm 16 relative to the pre-toothed workpiece 23 in the shift direction Y parallel to the worm axis B and a movement of the grinding worm 16 in an axial direction parallel to the workpiece axis C1 are generated. The movements of the grinding worm in the axial direction and in the shift direction Y are in a diagonal relationship selected such that the worm waviness is specifically projected onto the tooth flank of the pre-toothed workpiece, thereby specifically modifying the surface structure of the tooth flank.Thus, a desired tooth flank modification can be defined on the tooth flank of the pre-toothed workpiece 23, which can be calculated back for a selected diagonal ratio to a corresponding worm waviness along a spiral branch S1' on the grinding worm flank 161, which in turn can be calculated back for a selected speed ratio to a corresponding dressing flank modification, whereby the corresponding dressing flank modification can then be specifically produced according to the manufacturing processes described above.

[0002] LIST OF REFERENCE SYMBOLS Generating grinding machine 60 Negative form Machine bed 61 Inner flank Tool carrier 70 Turning tool Axial slide 71 Turning tool center Shift slide 80 Deformation device Tool spindle A Dressing rotary axis Grinding worm B Worm axis Grinding worm flank C1 Workpiece axis Acoustic sensor C3 Swivel axis Position sensor C4 Swivel axis Workpiece carrier X Feed direction Workpiece spindle Y Shift direction Workpiece spindle drive Z Feed direction Workpiece K Conditioning rotary axis Dressing device D Negative form rotary axis Swivel device r Radial coordinate Dressing spindle r' Radial coordinate of the dressing tool Sample rectangle Base body φ Angular coordinate Dressing flank surface φS Worm circumference coordinate Machine control rS Worm radial coordinate Axis modules λr' Radial shaft length Control computer ∆φU Offset angle Control panel α Inclination angle Monitoring device d Profile height Conditioning device rA inner radius conditioning tool R1,R2 radial path conditioning rib U1,U2 circumferential path conditioning spindle S1,S2,S3 spiral branch conditioning control,

Claims

PATENT CLAIMS 1.Dressing tool for dressing a grinding worm (16) for the generating machining of pre-toothed workpieces (23), wherein the dressing tool (33) is designed for rotation about a dressing axis of rotation (A) and has a dressing flank surface (331) which forms a circular ring in a projection plane perpendicular to the dressing axis of rotation (A), wherein the circular ring defines a radial direction with a radial coordinate (r) and a circumferential direction with an angular coordinate (φ), wherein the dressing flank surface (331) is provided with a specifically generated dressing flank modification, wherein the dressing flank modification, projected onto the circular ring, can be described as a two-dimensional Fourier series as a function of the radial coordinate (r) and the angular coordinate (φ), characterized in that the Fourier series has at least one Fourier coefficient unequal to zero for a circumferential frequency component unequal to zero with respect to the angular coordinate (φ).Dressing tool according to claim 1, wherein the dressing flank modification has a 2π periodicity with respect to the angular coordinate (φ).

3. Dressing tool according to claim 1 or 2, wherein the Fourier series has no non-zero Fourier coefficient for a non-zero radial frequency component in the radial direction, such that the deliberately generated dressing flank modification is wave-shaped with respect to the circumferential direction and has wavefronts in the form of lines of constant phase position, which, when projected onto the annulus, are radially aligned.

4. Dressing tool according to claim 1, wherein the two-dimensional Fourier series has at least one non-zero Fourier coefficient for a radial frequency component and for a non-zero circumferential frequency component, such that the dressing flank modification, when projected onto the annulus, forms a checkerboard-like structure with wave crests and wave troughs arranged in a checkerboard-like manner. 5.Dressing tool according to claim 4, wherein the checkerboard-like structure is aligned such that adjacent wave troughs and. Wave crests are arranged along a spiral branch (S1, S2, S3) running spirally on the circular ring.

6. A method for producing a dressing tool (33) according to one of claims 1-5, the method comprising: producing a coated base body of the dressing tool (33) in a positive process, and deliberately creating the dressing flank modification by means of a conditioning tool (51), in particular a rotating conditioning disk perpendicular to the dressing flank surface.The method according to claim 6, wherein the targeted generation of the dressing flank modification comprises: driving the dressing tool (33) to rotate about the dressing axis of rotation (A); driving the conditioning tool (51) to rotate about a conditioning axis of rotation (K) of the conditioning tool (51); and advancing the conditioning tool (51) relative to the dressing tool (33) in a direction having a portion running normal to the dressing flank surface, to generate the dressing flank modifications by removing material from the dressing flank surface (331). 8.A method for producing a dressing tool (33) according to any one of claims 1-5, the method comprising: producing the dressing tool (33) in a negative process, wherein the negative process comprises: producing a negative mold (60) by turning a negative base body; turning a targeted negative modification into the turned negative mold (60) such that the negative modification effects the dressing flank modification, and / or generating mechanical and / or hydraulic clamping of the negative base body during turning such that the turned negative mold (60) has a negative modification after the mechanical clamping is released, which negative modification effects the dressing flank modification.

9. A method for dressing a grinding worm (16) for the generating machining of pre-toothed workpieces, the method comprising:. Dressing the grinding worm (16) with a dressing tool (33) according to one of claims 1-5, such that the dressing flank modification effects a worm modification on a grinding worm flank (161) of a worm thread of the grinding worm (16).

10. The method according to claim 9, wherein a predetermined fixed rotational angle coupling exists between the dressing tool (33) and the grinding worm (16) in order to specifically generate a periodic worm modification on the grinding worm flank (161) along the worm thread.

11. The method according to claim 9, wherein a predetermined time-variable rotational angle coupling exists between the dressing tool and the grinding worm (16) in order to specifically generate a non-periodic worm modification on the grinding worm flank (161) along the worm thread. 12.A method for dressing a grinding worm (16) for generating a pre-toothed workpiece (23), comprising: defining a desired worm modification on a grinding worm flank (161) of a worm thread of the grinding worm (16); calculating the desired worm modification back to a corresponding dressing flank modification of a dressing tool (33) for a selected fixed or variable rotational angle coupling between the dressing tool (33) and the grinding worm (16); producing the dressing tool (33) having the corresponding dressing flank modifications using a method according to any one of claims 6-8; dressing the grinding worm (16) with the dressing tool (33) with the selected fixed or variable rotational angle coupling, wherein the dressing flank modification along the worm thread produces the desired worm modification.A method for producing a modified surface structure on a tooth flank of a pre-toothed workpiece (23), comprising: dressing a grinding worm suitable for generating pre-toothed workpieces (23) using the method according to any one of claims 9-12; driving the grinding worm (16) to rotate about a worm axis (B); driving the pre-toothed workpiece (23) to rotate about a workpiece axis (C1). Generating a relative movement between the grinding worm (16) and the pre-toothed workpiece (23) in a shift direction (Y) parallel to the worm axis at a shift feed rate, and generating a relative movement between the grinding worm and the pre-toothed workpiece in an axial direction parallel to the workpiece axis (C1) at an axial feed rate, wherein the grinding worm (16) and the pre-toothed workpiece (23) are in rolling engagement and wherein the shift feed rate and the axial feed rate are in a predetermined diagonal ratio such that the worm modification is mapped onto the tooth flank of the pre-toothed workpiece (23) and the surface structure of the tooth flank is thereby specifically modified. 14.Method according to claim 13, wherein the dressing tool is a dressing tool (33) according to claim 5, and wherein, during dressing, a predetermined fixed rotational angle coupling exists between the dressing tool (33) and the grinding worm (16), which coupling is selected such that the spiral branch (S1) is mapped onto a worm contact path, wherein the worm contact path corresponds to a line on which a contact point between the grinding worm (16) and the pre-toothed workpiece (23) in rolling engagement moves on the grinding worm flank during generating machining.Conditioning device, comprising: a conditioning tool (51) clamped on a conditioning spindle (52); a dressing spindle (32) designed to receive a dressing tool (33) for rotation about a dressing axis of rotation (A); a conditioning control (53) designed to move the conditioning tool (51) relative to the dressing tool (33) such that the dressing tool (33) is provided with the dressing flank modifications according to one of claims 1-5.

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