CH719945B1 - Dressing tool for dressing a grinding worm for the rolling machining of pre-toothed workpieces - Google Patents

Abstract

A dressing tool for dressing a grinding worm for the rolling machining of pre-toothed workpieces is designed to rotate about a dressing rotation axis (A) and has a dressing flank surface which forms a circular ring in a projection plane perpendicular to a dressing rotation axis of the dressing tool, the circular ring having a radial direction with a radial coordinate (r) and a circumferential direction with an angular coordinate (ϕ). The dressing flank surface is provided with a specifically generated dressing flank modification, whereby the dressing flank modification can be described as a two-dimensional Fourier series projected onto the circular ring depending on the radial coordinate (r) and the angular coordinate (ϕ), and whereby the Fourier series has at least one Fourier Non-zero coefficients for a non-zero circumferential frequency component with respect to the angular coordinate.

Description

TECHNICAL FIELD

The present invention relates to a dressing tool for dressing a grinding worm for the rolling machining of pre-toothed workpieces, a method for producing such a dressing tool, and a conditioning device which is designed to carry out such a method for producing it. The invention further relates to a method for dressing a grinding worm for the rolling machining of pre-toothed workpieces with 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.

STATE OF THE ART

[0002] Particularly in the context of electromobility, the topic of NVH (noise-vibration-harshness) is becoming increasingly important, especially in the area of the transmission of a vehicle due to the lack of dominant background noise from the internal combustion engine. 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 checked randomly on an end-of-line test bench (EOL). If the measured amplitudes of individual noise frequencies are above the predefined limit, the corresponding workpiece is rejected.

A typical noise frequency spectrum of a rotating gear has dominant amplitudes at noise frequencies which correspond to the tooth meshing frequency (fZE = gear rotation frequency x number of teeth) and the associated higher harmonics in the corresponding tooth meshing orders (ZEO). These dominant noise frequencies usually result from rotational path deviations, which arise as a result of the engagement stiffness varying over the engagement distance. The course of the engagement stiffness as a function of the position along the engagement path repeats periodically with the engagement pitch and leads to the dominant noise frequencies mentioned above. Another cause can be a “rolling hole” that occurred during production, i.e. material that is left behind in relation to the desired profile line.

[0004] Overall, all rotational path deviations of a gearing under load can lead to noise excitation, which can be perceived as a disturbing noise. For example, if a dressing tool has a certain waviness across the profile height, this is transferred to the screw flank and then leads to a profile shape 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 ripples on the tooth flank, which can be detected by measurement and result in disturbing noise properties of the toothing.

[0006] Grooves running across the width of the toothing can also lead to noise. Overall, any periodic surface structure, especially in a direction perpendicular to the line of engagement of paired spur gears, can lead to an excitation of a noise frequency which occurs dominantly in the noise frequency spectrum of the gearing.

[0007] There are several approaches to improve the noise excitation behavior of a gear. Rotational path deviations that result from deformation of the gearing under load can be effectively reduced by targeted modification of the tooth flank. A rolling hole can be almost completely eliminated through optimized process management.

[0008] DE 10 2012 015 846 A1 discloses a generating grinding method in which a workpiece is machined with a grinding worm, whereby by means of targeted generation of an unbalanced 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 edge waviness is generated on the active surface of the workpiece machined with it in order to modify or prevent unwanted edge waviness.

[0009] A flank waviness on the workpiece resulting from unbalance or eccentricity of a grinding worm always has order one with respect to the worm rotational frequency, i.e. it is not possible to generate a flank ripple in this way that has a higher order with respect to the worm rotational frequency.

[0010] DE 10 2013 003 795 A1 discloses a method for hard-fine machining tooth flanks with corrections and/or modifications on a gear cutting machine, wherein pairs of gear wheels that are in mesh with one another within a transmission or a testing device are machined taking the respective counter flanks into account and whereby the tooth flanks of the affected workpieces are provided with periodic waviness corrections or modifications. According to the invention, the rotational error curve is determined by measuring the rotational path error of the gear pairs in a gear measuring device and/or gear. This measurement result serves as an input variable for defining the amplitude, frequency and phase position for the periodic flank ripple 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 in a relatively narrow noise frequency band. A surface structure that is as irregular as possible leads in turn to a very broad noise frequency spectrum, which approaches “white” noise, i.e. a noise frequency spectrum with the same amplitude of all noise frequencies. Such a noise frequency spectrum, in which the dominance of individual noise frequencies tends to be reduced, is perceived as less disruptive from a psychoacoustic perspective and is therefore advantageous. In addition, with excitations with a wide noise frequency spectrum, the entire 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.

[0012] 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 originate, for example, from the dressing of the grinding worm with which the tooth flank is machined: The dressing wheel used during dressing can be over the circumference due to technology Differences in grain size and shape, 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, this dressing pattern is periodically imaged on the grinding worm during dressing in the direction of the worm gear. During the subsequent grinding of the workpiece, periodic fluctuations in the tooth flank surface in the form of grooves can then arise on the tooth flanks of the workpiece, which extend across the tooth width.

[0013] DE 199 05 136 A1 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, the grinding worm moving along its axis relative to the Workpiece is moved (shift feed), so that each point on the tooth flanks of the workpiece teeth corresponds to exactly one point on the flanks of the grinding worm gear.

The above-mentioned grooves can be broken by carefully selecting the shift feed. This means that the periodicity of the tooth flank surface structure is broken and in principle a more pleasant noise behavior is achieved, but the structure transferred to the tooth flank is highly dependent on the manufacturing-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 become.

PRESENTATION OF THE INVENTION

In a first aspect, it is an object of the present invention to provide a dressing tool with which a grinding wheel for the rolling machining of pre-toothed workpieces can be dressed in such a way that the grinding worm specifically produces 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.

[0016] This object is achieved by a method according to claim 1. Further embodiments are specified in the dependent claims.

[0017] A dressing tool for dressing a grinding worm for the rolling machining of pre-toothed workpieces is therefore proposed, wherein the dressing tool is designed to rotate about a dressing rotation axis and has a dressing flank surface which forms a circular ring in a projection plane perpendicular to the dressing rotation axis, the circular ring defining 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 can be described as a two-dimensional Fourier series projected onto the circular ring depending on the radial coordinate and the angular coordinate.

The Fourier series has at least one non-zero Fourier coefficient for a non-zero circumferential frequency component with respect to the angular coordinate. Metaphorically speaking, this means that the dressing flank modification has a waviness in the circumferential direction.

[0019] The waviness of the dressing tool in the circumferential direction can be transferred to a grinding worm flank of a worm gear during dressing by appropriately specifying the speed ratio or the rotation angle coupling between the dressing tool and the grinding worm to be dressed, so that a worm modification with a gear ripple is formed on this grinding worm flank. This gear waviness can in turn be used to generate 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 to dress a grinding worm in such a way that this grinding worm can be used to produce targeted tooth flank ripples on a workpiece, with great flexibility with regard to the wavelength and phase position of the tooth flank ripples.

In contrast to a purely radial ripple of the dressing tool, which is transmitted independently of a speed ratio between the dressing tool and the grinding worm to be dressed, a ripple in the circumferential direction can be transmitted in a desired manner to a grinding worm to be dressed by a speed ratio or a rotation angle coupling between the dressing tool and the grinding worm to be dressed is specified accordingly. 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 number of wave periods with respect to the angular coordinate.

[0022] The term “wave fronts” is understood below to mean lines of constant phase position or, in other words, lines along which no amplitude modulations occur.

[0023] In one embodiment, the Fourier series does not have a non-zero Fourier coefficient for a non-zero radial frequency component in the radial direction, such that the specifically generated dressing flank modification is wave-shaped with respect to the circumferential direction, and has wave fronts in the form of lines of constant phase position, which are projected onto the circular ring and are aligned radially. In other words, in this embodiment the dressing flank modification has a waviness that occurs exclusively in the circumferential direction.

In another embodiment, the two-dimensional Fourier series has at least one Fourier coefficient not equal to zero for a radial frequency component and for a circumferential frequency component not equal to zero, such that the dressing flank modification projects onto the annulus a checkerboard-like structure with a checkerboard-like structure arranged offset from one another in a checkerboard-like manner wave crests and wave troughs. 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 ripples of adjacent radial paths are offset by exactly 180°, a circumferential ripple occurs along circumferential paths running parallel to the circumferential direction, with the circumferential paths being spaced apart from one another in the radial direction by half a radial wavelength of the radial ripple. Such a checkerboard-like structure can be described mathematically as an additive superposition of two partial waves, the partial waves having oblique wave fronts projected onto the unrolled annulus, i.e. wave fronts that are at an angle of inclination α not equal to 0°, ±90° or ± relative to the unrolled circumferential direction 180 ° are inclined, the oblique wave fronts of the first partial wave having a positive slope (α > 0 °) and the oblique wave fronts of the second partial wave having a negative slope (α < 0 °), and the first partial wave each having 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 on the circular ring is aligned in such a way that adjacent wave troughs and wave crests are arranged in the circumferential direction along a spiral branch that runs spirally on the circular ring, the number of wave periods along the spiral branch being 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 order in the spiral branch direction. The checkerboard-like structure can also be aligned and/or distorted in such a way that two or more spiral branches occur. The transition of the spiral branch or of the spiral branches after one revolution of the dressing tool. Such a structure with spiral branches can also be described mathematically as an additive superposition of two partial waves, with the partial waves having oblique wave fronts projected onto the circular ring. If the number of spiral branches is less than twice the order in the spiral branch direction, the structure can be described using an additive superposition in which the oblique wave fronts of the first partial wave have a positive slope and the oblique wave fronts of the second partial wave have a negative slope , 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 of spiral branches is 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 using an additive superposition in which the oblique wave fronts of the first partial wave and the second partial wave are either both positive or both have a negative slope, the first partial wave having 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 shown above. The method for production includes: producing a coated base body of the dressing tool in a positive process, and specifically generating the dressing flank modification by means of a conditioning tool, in particular a rotating conditioning disk perpendicular to the dressing flank surface.

A narrow rotating conditioning disk is preferably used, for example a conditioning disk, which has a rounded head on its outer circumference (i.e. a crowning of a lateral surface of the conditioning disk in the axial direction) with a radius of curvature which corresponds to at most a quarter of a radial wavelength in the radial direction, whereby the radial wavelength corresponds to the wave period of the ripple in the radial direction.

[0028] The targeted generation of the dressing flank modifications can in particular include: driving the dressing tool to rotate about the dressing rotation axis; Driving the conditioning tool to rotate about a conditioning rotation axis of the conditioning tool, and advancing the conditioning tool relative to the dressing tool in a direction that has a portion normal to the dressing flank surface, to produce the dressing flank modifications by removing material from the dressing flank surface.

By removing material, a conditioning track can be created in the dressing flank surface, which corresponds to a wave trough and has a width that corresponds to half a radial wavelength in the radial direction. However, the width of the conditioning track can also be smaller than half the radial wavelength of the desired dressing flank modification in the radial direction. In such a case, it may be necessary to create several adjacent conditioning tracks to create a complete trough.

The feed movement of the conditioning tool relative to the dressing tool can be carried out by a movement of the conditioning tool in space and/or a movement of the dressing tool in space. The feed movement or the resulting feed position of the conditioning tool in the direction normal to the dressing flank surface can oscillate with a feed frequency which is in a predetermined fixed relationship to the rotational frequency of the dressing tool. This allows the material removal along the conditioning track to be varied, which leads to 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 feed movement include: generating a discontinuous or continuous conditioning axial movement along the conditioning rotation axis.

In the present context, “continuous” means that the conditioning axial movement is carried out while the conditioning tool is in contact with the dressing tool and thus material removal takes place during the conditioning axial movement.

In the present context, “discontinuous” means that the conditioning axial movement is carried out while the conditioning tool is not in contact with the dressing tool and thus no material is removed during the conditioning axial movement.

The conditioning axial movement is to be understood as the relative movement between the dressing tool and the conditioning tool along the conditioning rotation axis. The conditioning tool and/or the dressing tool can be driven to carry out the conditioning axial movement.

[0035] Depending on the dressing flank modification, the targeted generation of said dressing flank modification can further include: generating a plurality of conditioning tracks that intersect at a predetermined angle with the conditioning tool on the dressing flank surface by a discontinuous and/or continuous conditioning axial movement along the conditioning rotation axis, the feed position of the conditioning tool to the dressing flank surface can have a constant value in the direction normal to the dressing flank surface or the feed movement or feed position of the conditioning tool can oscillate with a feed 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 that runs spirally on the circular ring.

[0037] Alternatively, the method for producing the dressing tool may include: producing the dressing tool in a negative process, the negative process comprising: producing a negative mold by turning out a negative base body; Turning a targeted negative modification into the turned negative shape in such a way that the negative modification causes the dressing flank modification and/or generating a mechanical and/or hydraulic tension of the negative base body during turning out in such a way that the turned negative shape has a negative modification after the mechanical tension has been released, which too the dressing flank modification is effected.

The targeted negative modification can be turned into the turned negative mold using a suitable machining tool, in particular a turning tool, which is preferably movable along a negative mold rotation axis of the negative mold relative to the negative mold.

In particular, the targeted generation of the negative modifications can include: driving the negative mold to rotate about a negative mold rotation axis at a rotation frequency; Positioning the turning tool in such a way that it creates a negative track in at least one inner flank of the negative mold.

In a further aspect, the invention provides a method for dressing a grinding worm for the rolling machining of pre-toothed workpieces. The method for dressing a grinding worm for the rolling machining of pre-toothed workpieces includes: dressing the grinding worm with a dressing tool shown above, such that the dressing flank modification causes a worm modification on a grinding worm flank of a worm flight of the grinding worm.

[0041] There can be a predetermined fixed angle of rotation coupling 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 flight. 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 predetermined time-variable rotation angle 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 flight. In this case, the dressing flank modification is mapped into the screw modification with a non-constant compression factor.

[0043] In a further aspect, a method for dressing a grinding worm for the rolling machining of a pre-toothed workpiece is described, in particular comprising the method presented above, comprising: defining a desired worm modification on a grinding worm flank of a worm flight of the grinding worm; Dressing the grinding worm with a dressing tool which has a specifically generated dressing flank modification, wherein during dressing there is a fixed or variable rotation angle coupling between the dressing tool and the grinding worm, which is predetermined in such a way that the dressing flank modification along the worm flight produces the desired worm modification.

In a further aspect, the invention provides a method for producing a modified surface structure on a tooth flank of a pre-toothed workpiece. The method for producing a modified surface structure on a tooth flank of a pre-toothed workpiece includes: dressing a grinding worm suitable for the rolling machining of pre-toothed workpieces using the method described above; driving the grinding worm to rotate about a worm axis; driving the pre-cut 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”) with a shift feed speed, and generating a relative movement between the grinding worm and the pre-toothed workpiece in an axial direction parallel to the workpiece axis (“axial feed movement ") with an axial feed rate, whereby the grinding worm and the pre-toothed workpiece are in a rolling engagement and where 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 becomes.

The diagonal ratio refers to the ratio of the shift feed speed of the grinding worm in the shift direction to the axial feed speed of the grinding worm in the axial direction parallel to the workpiece axis. The diagonal ratio can be zero or non-zero. When 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 not equal to zero, the resulting modification of the surface structure of the tooth flank can be a topological modification, i.e. a modification that has components in both the height direction and the width direction of the tooth flank.

[0046] In addition, the method can also include 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”). As a result, further modifications can be superimposed on the modification of the surface structure of the tooth flank described above. 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.

The worm modification leads to a variation of a penetration depth between the grinding worm and the pre-toothed workpiece during rolling machining and thus generates a tooth flank waviness along a contact track on the tooth flank, the contact track corresponding to a line on which the point of contact between the grinding worm and the The pre-toothed workpiece in rolling engagement is moved on the tooth flank during rolling machining.

[0048] If the dressing tool has a checkerboard-like structure, which is aligned in such a way that adjacent wave troughs and wave crests are arranged in the circumferential direction along a spiral branch that runs spirally on the circular ring and thus form a spiral waviness, can be between the dressing tool and the grinding worm during dressing a fixed rotation angle coupling can be selected such that the spiral branch is mapped onto a worm contact path on the grinding worm flank, the worm contact path corresponding to a line on which a point of contact between the grinding worm and the pre-toothed workpiece in rolling engagement moves on the grinding worm flank during rolling machining.

[0049] Thus, the spiral waviness that occurs along the spiral branch on the dressing flank surface can be specifically 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 on uncontrolled, in particular stochastic, 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 roller grinding machine in which the rolling machining is carried out.

Through the targeted variation of the penetration depth based on the worm modifications of the grinding worm dressed as described above, a suitable carrier pattern can be generated on the tooth flank, which can be made more diffuse by superimposing the uncontrolled variations of the penetration depth, which leads to an optimization of the noise behavior can result. In this way, for example, unavoidable vibrations can specifically help to improve noise behavior.

[0052] Preferably, the targeted variation of the penetration depth due to the grinding worm dressed as described above has a modulation amplitude which is in a range between 0.2 times and 5 times a fluctuation mass for the uncontrolled deviations in the penetration depth, wherein the fluctuation measure corresponds in particular to a standard deviation or an interquartile range of the uncontrolled deviations in the penetration depth, in particular, wherein the degree of fluctuation of the uncontrolled variations in the penetration depth is determined and the modulation amplitude, and thereby in particular an amplitude of the screw modifications and thereby in particular an amplitude of the dressing flank modifications, is specifically selected depending on the determined degree of fluctuation.

[0053] In a further aspect, a conditioning device is described, comprising: a conditioning tool clamped on a conditioning spindle, in particular a narrow conditioning disk, i.e. a conditioning disk, which has on its outer circumference a rounded head with a radius of curvature which corresponds to at most a quarter of a radial wavelength in the radial direction , where the radial wavelength corresponds to the wave period of the ripple in the radial direction; a dressing spindle configured to receive a dressing tool for rotation about the dressing rotation axis; a conditioning control, which is 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 to the drawings, which serve only for explanation and are not to be construed as restrictive. The drawings show: FIG. 1A a schematic front view of a dressing tool in a projection plane perpendicular to a dressing rotation axis of the dressing tool; 1B shows a projection of a dressing flank surface in developed form; 2 shows a first example pattern of a dressing flank modification; 3 shows a second example pattern of a dressing flank modification; 4 shows a third example pattern of a dressing flank modification; 5 shows a fourth example pattern of a dressing flank modification; 6A shows a fifth example pattern of a dressing flank modification; 6B shows a first partial wave pattern for the additive mathematical description of the fifth example pattern of FIG. 6A; 6C shows a second partial wave pattern for the additive mathematical description of the fifth example pattern of FIG. 6A; 7A shows a first exemplary arrangement of a spiral branch on the dressing flank surface; 7B shows a second exemplary arrangement of two spiral branches on the dressing flank surface; 7C shows a third exemplary arrangement of three spiral branches on the dressing flank surface; 7D shows a sixth example pattern of a dressing flank modification with two spiral branches; 7E shows the sixth example pattern transferred to the projection of the dressing flank surface; 8 shows a conditioning device according to an embodiment of the present invention; 9 shows a turned negative mold for producing a dressing tool according to the present invention; 10A shows a negative mold clamped using a deformation device; 10B shows a relaxed and turned negative mold for producing a dressing tool according to the present invention; 11 shows a projection of a grinding worm flank of a screw flight of a grinding worm in unwound form; Fig. 12 is a schematic view of a generating grinding machine, and Fig. 13 is an enlarged detail from Fig. 12.

DESCRIPTION OF PREFERRED EMBODIMENTS

dressing tool

1A shows schematically a front 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 rotation axis A of the dressing tool 33, the circular ring having a radial direction with a radial coordinate r and a circumferential direction with an angular coordinate ϕ and where the circular ring has an inner radius rA.

In 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 an unrolled form.

2 - 6A show, by way of example, schematically various wave-shaped patterns which can have the specifically generated dressing flank modifications on the dressing flank surface shown in FIG. 1B, with wave crests shown here schematically in light shade and wave troughs in dark shade.

The following explains how these two-dimensional wavy patterns can be described mathematically. For this purpose, a pattern rectangle with a pattern height Δr' in the height direction, which is hereinafter referred to as the radial direction, and a pattern length 2π in the longitudinal direction, which is hereinafter referred to as the circumferential direction, is used. The patterns can each be represented as a two-dimensional real-valued Fourier series f(ϕ, r') (i.e. a real-valued Fourier series in two real-valued variables ϕ and r') depending on the angular coordinate ϕ ∈ [0,2π] and a radial coordinate of the pattern rectangle r' ∈ [0, Δr']: where the circumferential frequency components km= mk1 is unitless and the radial frequency components Rn= nR1 have the unit [1/mm]. In this definition, the angular coordinate ϕ of the pattern rectangle corresponds to the angular coordinate ϕ of the aforementioned circular ring. The radial coordinate r' of the coordinate system of the pattern rectangle can also be expressed as the radial coordinate r in the coordinate system of the circular ring using a linear transformation, e.g. via the relationship r = r' + rA, where rA denotes the inner radius of the circular ring.

The indices m ∈ and n ∈ are integers, whereby the peripheral frequency components km and respectively. the radial frequency components R are integer multiples of a circumferential fundamental frequency k1 = 1 or a radial fundamental frequency R1 =.

The Fourier coefficients, which indicate the amplitude and phase position of the corresponding frequency components, are referred to as cn,m. The Fourier coefficients can generally be written in complex form as cn,m= an,m+ ibn,m= An,m· e<iθ n,m>, where an,m is the real part, bn,m is the imaginary part, An,m is the amplitude and θn,m is the phase. The complex conjugate coefficient is = an,m- ibn,m= An,m e<-iθ n,m>. 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), then the phase position of the pattern in the circumferential direction is irrelevant.

Due to the definition of the radial fundamental frequency chosen above, the pattern repeats periodically in the radial direction with a pattern period of Δr'.

The phase position of the dressing flank modifications f(ϕ, r) 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 r' of the pattern rectangle to the radial coordinate of the dressing flank surface r, f(ϕ, r ') → f(ϕ, r), whereby the profile height d, over which the dressing flank modifications extend, can correspond to the pattern period Δr', or can be chosen to be smaller or larger (since the pattern continues periodically with a pattern period of Δr'). can. In other words, this means that any radial section of the periodic example patterns described mathematically below can be applied to the dressing tool as a dressing flank modification.

[0063] Thus, the phase position of the pattern on the pattern rectangle is irrelevant and for simplified description on the pattern rectangle the Fourier coefficients cn,and c-n,-m complex conjugate can be chosen, i.e. cn,m==An,m·e<iθ n,m>.

[0064] Metaphorically speaking, the dressing flank modification can be described as a section of a wavy pattern on the pattern rectangle or a superposition of two or more wavy sub-patterns on the pattern rectangle, whereby each of these wavy sub-patterns can have a 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 sub-patterns are superimposed to describe the resulting pattern, the relative phase position of the sub-patterns to one another is relevant.

[0065] The number of wave periods on the pattern rectangle in the radial direction is hereinafter referred to 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 for each of these wave-shaped patterns/partial patterns. A wave period in the radial direction has a radial wavelength λr, and a wave period in the circumferential direction is expressed in the following context as an offset angle ΔϕU (“circumferential wavelength”). Since the circumferential fundamental frequency k1= 1 was chosen, the order in the circumferential direction M corresponds to the index amount |m|, and since the radial fundamental frequency R1= was chosen, the order in the radial direction N corresponds to the index amount |n|.

In the embodiment shown in FIG. 2, the pattern has wave fronts in the form of lines of constant phase position, the wave fronts forming continuous, straight lines when projected onto the unrolled circular ring. As shown in Fig. 2, these lines are inclined with respect to the developed circumferential direction by an inclination angle α and are spaced apart from one another in the circumferential direction by an offset angle ΔϕU. So that the pattern of dressing flank modification can be continued periodically after one revolution, only discrete values for the inclination angle α are possible, i.e. the lines of constant phase position for α < 0 ° have a negative slope (i.e. on the pattern rectangle as in Fig. 2 from the top left run to the bottom right) and where the lines of constant phase position for α > 0° have a positive slope (i.e. run from bottom left to top right on the sample rectangle). If the lines of constant phase position have a negative slope, the following frequency component pairs {Rn, km} have a Fourier coefficient not equal to zero: {Rn=+N, km=+M} and (Rn=-N, km=-M}

[0067] If, on the other hand, the line of constant phase position has a positive slope, the following pairs of frequency components have a Fourier coefficient not equal to zero: {Rn=+N, km=-M}and (Rn=-N, km=+M}

The waveform does not necessarily have to be a pure sine wave, 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 n is an integer multiple of N and m is an integer multiple of M. 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:

[0070] Specifically, the following applies to the pattern in FIG. 2: c5.5= ≠ 0, while all other Fourier coefficients are zero.

3, the angle of inclination α is exactly 90°, i.e. the wave fronts of the dressing flank modification, projected onto the circular ring, are aligned radially. This case corresponds to a complex Fourier series which has no non-zero coefficient for a non-zero radial frequency component Rn in the radial direction. The dressing flank modification shown here runs continuously in the circumferential direction, i.e. the wave-shaped dressing flank modification has an integer number of wave periods based on a single revolution of the dressing tool (2π periodicity). The following table summarizes the parameters of the dressing flank modification from FIG. 3:

[0072] Specifically, the following applies to the pattern in FIG. 3: c0.4= ≠ 0, while all other Fourier coefficients are zero.

4, the inclination angle α is exactly 0°, i.e. the wave fronts extend in a straight line parallel to the circumferential direction and form a radial ripple with a radial wavelength λr in the radial direction. This case corresponds to a complex Fourier series which has no non-zero coefficient for a non-zero circumferential frequency component km in the circumferential direction. The following table summarizes the parameters of the dressing flank modification from FIG. 4:

[0074] Specifically, the following applies to the pattern in FIG. 4: c4,0= ≠ 0, while all other Fourier coefficients are zero.

5, the two-dimensional complex Fourier series has a coefficient not equal to zero for a radial frequency component Rn not equal to zero and for a circumferential frequency component km not equal to zero, such that the wave-shaped dressing flank modification is projected onto the unrolled circular ring in a checkerboard-like manner Structure with offset wave crests and wave troughs. Mathematically, the pattern from Fig. 5 can be described as an additive superposition of a first partial wave fW1(ϕ, r'), and a second partial wave fW2(ϕ, r'), f(ϕ, r') = tW1(ϕ, r' ) + fW2(ϕ, r'), where 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 slope in the first partial wave and in the second partial wave have a positive slope.

5, adjacent wave troughs and wave crests are offset from one another and thus each form a radial ripple along radial paths R1, R2 that run parallel to the radial direction. The radial ripples of adjacent radial paths are offset by exactly 180° in the example shown in FIG Are spaced apart in the radial direction. The following table summarizes the parameters of the dressing flank modification from FIG. 5: Specifically, the following applies to the pattern of FIG. 5: c4,4= ≠ 0 and c4,-4= ≠0 while all other Fourier coefficients are zero.

6A shows a spiral pattern that is mathematically described as an additive superposition of a first partial wave fW1(ϕ, r') shown in FIG. 6B and a second partial wave fW2(ϕ, r') shown in FIG. 6C can be: f(ϕ, r') = tW1(ϕ, r') + fW2(ϕ, r')

5, the radial ripples of the adjacent radial paths R1, R2 in FIG and thus form a spiral ripple. The number of wave periods along the spiral branch S1 is referred to below as the order in the spiral branch direction L.

[0079] The pitch height of a spiral branch over one revolution of the dressing tool results depending on half the radial wavelength λr'/2 and the number of spiral branches is∈ <+>. The spiral branches form straight lines on the unrolled 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:

So that the pattern of dressing flank modification can be continued periodically after one revolution, only discrete values for the pitch height are possible. The pattern can always be continued periodically if the pitch height corresponds to a multiple of half the radial wavelength λr'/2.

In order to ensure a constant transition of the spiral branch after one revolution of the dressing tool, two cases must be distinguished: 1. The freely chosen 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 λr '/2 correspond, i.e. 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 height of the spiral branch must correspond to an odd multiple of half the radial wavelength λr'/2, i.e. the number of spiral branches is odd.

6A, the order in the spiral branch direction is L = 5.5 and the pitch height is exactly λr'/2, since there is exactly one spiral branch, i.e. is = 1.

In order to obtain a specific order L in the spiral branch direction for the spiral waviness, MW,1 of the first partial wave must be tW1(φ, r') for the order of the ripples in the circumferential direction and tW2 must be tW2 for the order of the ripples in the circumferential direction MW,2 (ϕ, r') apply: where, if ( - L) < 0 applies, the second partial wave has a slope with a sign that is opposite to the sign of the slope of the first partial wave. If ( - L) ≥ 0, the second partial wave has a slope with the same sign as the first partial wave. The following table summarizes the parameters of the dressing flank modification from FIG. 6A:

The first sub-wave fW1(ϕ, r') has wave fronts that have a negative slope (FIG. 6B), while the second sub-wave fW2(ϕ, r') has wave fronts that have a positive slope (FIG. 6C ). Specifically, the following applies to the pattern in FIG. 6A: c1,6= ≠ 0 and c1,-5= ≠ 0 while all other Fourier coefficients are zero.

[0085] Figures 7A-7C show schematically how the spiral branches can be arranged on the dressing flank surface 331 of the dressing tool 33. 7A shows an example in which exactly one spiral branch S1, i.e. is = 1, is formed on the dressing flank surface 331.

7B, two spiral branches S1, S2 are formed on the dressing flank surface 331, i.e. is = 2, with the spiral branches S1, S1 being offset by an offset angle Δϕ in the circumferential direction, which in this example is π.

7C, three spiral branches S1, S2, S3 are formed, the spiral branches S1, S2, S3, i.e. is = 3, being offset here by an offset angle Δϕ in the circumferential direction, which is 2π/3.

[0088] A further example pattern is illustrated using concrete numbers in FIGS. 7D and 7E. In this example, the number of spiral branches is = 2, the radial wavelength λr' = 15 mm, the pattern period is Δr' = 30 mm, the order in the spiral branch direction is L = 50 and the spiral branches S1, S2 run counterclockwise. The spiral ripple has an amplitude of A = 3.5 µm.

The orders of the ripples in the circumferential direction of a first partial wave 1 and a second partial wave 2 are thus calculated using the following equations: Partial wave 1: MW,1= 1 + L = 51 Partial wave 2: MW,2≠ |1 - L| = 49

The order in the radial direction is: Partial wave 1:

Partial wave 2:

The non-zero Fourier coefficients, in this case real Fourier coefficients, are therefore:

The checkerboard-like waviness can therefore be described with the following equation:

[0093] Using the relationship (2 · cos(x) = e<ix>+ e<-ix>), f(ϕ, r') can also be converted into a real notation:

The pattern f(ϕ, r') 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 can be seen projected onto the circular ring as a dressing flank modification f(ϕ, r), the pattern here extending over a profile height d<Δr' with d = 20 mm and where applies: f(ϕ, r) = f(ϕ, r' + rA) with rA= 30 mm.

Production of the dressing tool

Dressing tools with the dressing flank modifications explained above can be produced both in a positive process and in a negative process.

Positive procedure

In the positive process, a base body, preferably made of steel, is provided, which is preferably galvanically coated with hard material particles, typically diamond particles. Methods for producing a base body with a hard material particle coating in the positive process are known from the prior art, for example from the publications EP 2535145 A2 and EP 2835220 A1, the disclosure of which is incorporated herein in its entirety by reference.

8 shows schematically a conditioning device 50 according to an embodiment of the present invention. The conditioning device comprises a dressing tool 33 (here in a sectional view), the base body 330 having a hollow cylinder, which can be clamped onto a dressing spindle 32 and driven to rotate about the dressing rotation axis A. A circular disk with dressing flanks that taper to a point in the radial direction with respect to the dressing axis of rotation A extends around the hollow cylinder. 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 shown schematically here, this conditioning tool 51 is a narrow conditioning disk, which can be rotated about a conditioning rotation axis K that runs parallel to the dressing flank to be machined and can be moved in a direction normal to the dressing flank surface 331 and parallel to the conditioning rotation axis K. The conditioning disk preferably has an abrasive coating with bound hard material particles which have a comparable or higher hardness than the hard material particles of the dressing tool coating. To produce the dressing flank modifications, the dressing tool is driven to rotate about the dressing rotation axis A, while the conditioning tool 51 is driven to rotate about the conditioning rotation axis K. The rotating conditioning disk is then advanced in such a way that it comes into contact with the dressing flank surface 331 and material is thereby removed from the dressing flank surface 331. In the example shown in FIG. 8, the feed movement takes place parallel to a normal of the dressing flank surface 331.

[0098] The feed movement of the conditioning tool 51 or the feed position caused thereby perpendicular to the dressing flank surface can oscillate with a feed frequency f, which is coordinated with a rotation frequency of the dressing tool fA, in order to generate the desired ripples, while additionally a discontinuous or continuous conditioning axial movement along the conditioning rotation axis K can take place. In order to obtain a wave-shaped dressing flank modification of the desired order in the circumferential direction M, the following applies in particular: fK + MfA

The conditioning device comprises a conditioning control 53, which is designed to coordinate the rotational frequency of the dressing tool fA and the feed frequency fK, as well as to control the feed movement of the conditioning tool 51 relative to the dressing tool 33.

Examples:

[0100] The generation of the dressing flank modifications listed as examples in FIGS. 2-6A will be explained below.

Generating the dressing flank modification of Fig. 2:

[0101] The wave fronts that are inclined on the unrolled circular ring relative to the circumferential direction by the angle of inclination α can be generated as follows: infeed of the conditioning tool in the direction normal to the dressing flank surface to a constant infeed value; Generating a continuous conditioning axial movement of the conditioning tool with a constant axial speed along the conditioning rotation axis K during at least one revolution of the dressing tool 33.

The continuous conditioning axial movement can take place either from the inside to the outside or from the outside to the inside in relation to the radial direction of the dressing tool 33. An increase in the desired inclination angle α is accompanied by an increase in the constant axial speed while the rotational frequency of the dressing tool remains the same.

2, in which the inclination angle α is selected such that the wave fronts projected onto the unrolled circular ring have a slope with an amount of Δr'/2π, the axial velocity must therefore have a fixed value the rotational frequency fA of the dressing tool has a velocity component of vr=Δr'fA projected onto the radial direction of the dressing tool.

[0104] In the example shown in FIG. 2, per revolution of the dressing tool, a conditioning track running obliquely over the entire length of the unrolled circular ring is created in the dressing flank surface, which corresponds to a wave trough (darkly shaded in FIG. 2) and thus has a width, which corresponds to half the radial wavelength λr'/2. In order to produce the further wave troughs shown in FIG. 2, the conditioning tool is repositioned after each revolution of the dressing tool, but shifted in the circumferential direction with respect to the unrolled circular ring by the circumferential wavelength ΔϕU.

Generating the dressing flank modification of Fig. 3:

3, the wave-shaped dressing flank modification has wave fronts which are projected onto the circular ring and are aligned radially. To generate this dressing flank modification, the feed position of the conditioning tool oscillates normal to the dressing flank surface with a feed frequency fK, which is coordinated with the rotational frequency fA of the dressing tool, during which no conditioning axial movement takes place along the conditioning rotation axis K. 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: fK = MfA

The conditioning tool 51 thus generates a conditioning track running in the circumferential direction with a corresponding ripple of order M.

[0107] 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. So that conditioning tracks running adjacently in the radial direction form continuous, radially straight wave fronts, it must be ensured when the conditioning tool is placed 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 Ripple of the new conditioning track is in phase with the ripple of the previously generated conditioning track.

[0108] Alternatively, it is also conceivable to generate a continuous conditioning axial movement of the conditioning tool with a constant axial speed along the conditioning rotation axis K, instead of repositioning the conditioning tool along the conditioning rotation axis each time after one revolution of the dressing tool. However, in order for essentially straight wave fronts to be formed in the radial direction, the axial speed must be selected such that the conditioning tool has traveled a distance along the conditioning rotation axis K after one revolution of the dressing tool, which corresponds at most to the width of the conditioning track.

Generating the dressing flank modification of Fig. 4:

The dressing flank modification shown in Fig. 4 can be created by advancing the conditioning tool to a constant feed value in the direction normal to the dressing flank surface, whereby (in contrast to the generation of the dressing flank modification in Fig. 2) there is no continuous conditioning axial movement along the conditioning rotation axis K takes place, whereby a conditioning track running parallel to the circumferential direction is created. After at least one revolution of the dressing tool, the conditioning tool is repositioned at a plurality of different positions along the conditioning rotation axis K to produce new conditioning tracks adjacent in the radial direction, whereby wave fronts are generated which, when projected onto the unwound circular ring, extend in a straight line parallel to the circumferential direction.

Generating the dressing flank modification of FIG. 5:

The dressing flank modification shown in FIG. 5 can be generated by superimposing the steps required for generating the dressing flank modification shown in FIGS. 3 and 4: To generate the dressing flank modification shown in FIG to the dressing flank surface with a feed frequency fK, which is coordinated with the rotation frequency fA of the dressing tool, during which no conditioning axial movement takes place along the conditioning rotation axis K. 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: fK = MfA

The conditioning tool 51 thus generates a conditioning track running in the circumferential direction with a circumferential waviness of order M.

[0112] After one revolution of the dressing tool 33, the conditioning tool 51 is repositioned at a plurality of different positions along the conditioning rotation axis K in order to generate new conditioning tracks adjacent in the radial direction with a respective width of half a radial wavelength λr'/2. As a result, the circumferential waviness is formed along circumferential paths U1, U2 that run 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 undulations are shifted by 180° relative to one another.

[0113] Generating the dressing flank modification of FIG. 6A:

To generate the dressing flank modification shown in FIG. 6A, as in the case of the dressing flank modification in FIG the conditioning tool in the direction normal to the dressing flank surface (in contrast to the situation in Fig. 2) is not advanced to a constant feed value, but instead the feed position of the conditioning tool oscillates normal to the dressing flank surface with a feed frequency fK, which is coordinated with the rotational frequency of the dressing tool fA. This results in a dressing flank modification in which adjacent wave troughs and wave crests are arranged in the circumferential direction along spiral branch S1 which runs spirally on the circular ring, with the spiral branch S1 forming a straight line inclined with respect to the circumferential direction on the unwound circular ring.

In order to obtain a wave-shaped dressing flank modification of the desired order in the spiral branch direction L, the following relationship must be fulfilled: fK = LfA

[0116] In order to produce further spiral branches S2, S3..., the conditioning tool is repositioned after a spiral branch has been produced, but is shifted by an offset angle Δϕ in the circumferential direction ϕ with respect to the unrolled circular ring. In a preferred variant, the offset angle Δϕ is chosen such that the following relationship is satisfied: isΔϕ = 2π, where is represents the number of spiral branches.

[0117] The steps used to produce the examples explained can of course be combined to produce further dressing flank modifications that are not explicitly illustrated here.

In particular, patterns are also conceivable, for example, in which continuous wave troughs intersect at an arbitrarily predetermined angle. Purely radially aligned wave troughs can, for example, cross wave troughs aligned purely in the circumferential direction at an angle of 90° projected onto the annulus. Alternatively, the intersecting wave troughs can also run obliquely across the dressing flank surface.

The rotational frequency of the dressing tool fA and/or the feed frequency fK of the conditioning tool and/or the conditioning axial movement can be varied in time during machining in order to generate targeted dressing flank modifications which have more complex patterns.

Negative procedure

Dressing tools with the dressing flank modifications explained above can alternatively also be produced in a negative process. For this purpose, a negative base body, preferably made of aluminum or graphite, is provided, which is turned into a negative shape 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 in its entirety by reference.

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 shape. 9 shows a schematic sectional view of a negative mold 60, wherein the negative mold 60 is rotatably mounted about a negative mold rotation axis D and has inner flanks 61 that taper radially outwards with respect to the negative mold rotation axis D. 9 shows schematically a turning tool 70, which is inserted 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, with which material is removed from the inner flanks 61 to produce the negative modifications, while the negative mold moves with it a rotation frequency fN around which the negative mold rotation axis D rotates.

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.

[0123] By oscillating the axial movement of the turning tool tip 71 along the negative mold rotation axis D with a turning tool frequency f (as shown schematically by a sine curve in FIG. 9), negative tracks are rotated into the negative mold, which have a circumferential waviness in the circumferential direction that corresponds to a negative impression of the desired one Dressing flank modification of the dressing tool produced using this negative mold corresponds. The rotation frequency fN of the negative form and the turning tool frequency fD can each be constant over time, but can also be varied over time. Analogous to the examples explained above for direct machining of the dressing flanks with a conditioning tool, all of those shown as examples in FIGS Dressing flank modifications, as well as other modifications thereof, are generated.

[0124] 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 in time during machining in order to generate targeted dressing flank modifications which have more complex patterns.

[0125] Alternatively or additionally, the targeted generation of the negative modifications can also include a targeted generation of tensions in the negative form, as will now be explained with reference to FIGS. 10A and 10B.

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 clamps 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, areas of the inner flanks 61 are pressed axially closer to one another. If these areas of the inner flanks 61 that are pressed towards one another pass through the fixed turning tool tip 71 during the rotation of the negative mold, a larger amount of material is removed in the areas that are pressed towards one another than in other areas of the negative form 60 which are not compressed by the pre-forming device 80. The deformation device 80 preferably has force application areas arranged periodically in the circumferential direction of the negative mold. To generate the force on these force application areas, the deformation device 80 can have, for example, mechanical or hydraulic tensioning elements. In particular, the force can be exerted directly on the area of force application by a screw. Likewise, the force on the force application area can be generated by a hydraulic piston. Alternatively or additionally, the deformation device can have a two-part device which at least partially surrounds the negative mold and is held together by screws and/or hydraulic pistons. In a relaxed state (FIG. 10B), the negative form then has a negative track with a circumferential waviness, with wave troughs occurring in the negative form 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 tip 71 moved relative to the negative mold to produce any desired negative modification/dressing flank modifications.

Dressing the grinding worm

The invention also includes a method for dressing a grinding worm 16 for the rolling machining of pre-toothed workpieces, in which the dressing modifications of the dressing tool 33 are mapped 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.

11 shows an annular projection of a grinding screw flank 161 in a plane perpendicular to a screw rotation axis B in unrolled form, the annular projection defining a screw circumferential direction with a screw circumferential coordinate ϕS and a screw radial direction with a screw radial coordinate rs.

Screw modifications in the form of three spiral branches S1', S1", S1'" are shown schematically on the unwound grinding worm flank 161, the three spiral branches S1', S1", S1'" on the grinding worm flank 161 being the same spiral branch S1 on the dressing flank surface 331 correspond, 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 larger the said speed ratio, the steeper the spiral branch S1 ', S1", S1'" shown runs on the unwound grinding worm flank 161. The The worm modification generated by transferring the dressing flank modification to the grinding worm flank 161 has a number of wave periods based on one revolution of the grinding worm, this number being referred to here as the worm ripple 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 larger the said speed ratio, the larger the worm waviness order Ls. Typically the speed ratio is between 10 and 60.

The speed ratio can be constant over time, or can be changed during the dressing of the grinding worm, in which case the spiral branch S1 ' shown no longer forms a straight line on the unwound flank of the grinding worm, but is bent (in the event of an abrupt change in the speed ratio) or is arcuate (with a continuous change in the speed ratio).

[0132] Depending on a slope 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 in order to image the complete spiral branch S1 onto the grinding worm flank 161: Depending The flatter the gradient, the more revolutions are required.

[0133] A desired worm modification can therefore be defined on a grinding worm flank 161 of a worm flight of the grinding worm 16, which can be calculated back 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 then being calculated in accordance with the above The manufacturing process described can be produced specifically.

Generation of a targeted tooth flank modification on a pre-toothed workpiece

The worm modifications generated by the dressing tool as explained above can be transferred to a tooth flank of a pre-toothed workpiece in a rolling machining process.

The generating 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 “machine” for short. The machine 1 has a machine bed 11 on which a tool carrier 12 is guided displaceably along a radial feed direction X. The tool carrier 12 carries an axial slide 13, which is guided so as to be displaceable relative to the tool carrier 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) to adapt to the helix angle of the gearing to be machined. The grinding head in turn carries a shift carriage 14, on which a tool spindle 15 can be displaced along a shift direction Y relative to the grinding head. A helical 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.

[0136] The machine bed 11 further carries a pivotable workpiece carrier 20 in the form of a rotating tower, 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. A workpiece can be clamped on 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 processing position in which a workpiece 23 clamped on it can be processed with the grinding worm 16. The other workpiece spindle, which is offset by 180° and is not visible in FIG. 1, is in a workpiece changing position in which a finished workpiece can be removed from this spindle and a new blank can be clamped. A dressing device 30 is mounted at an angle of 90° to the workpiece spindles.

The machine 1 thus has a large number of movable components such as carriages or spindles, which can be moved in a controlled manner by appropriate drives. These drives are often referred to in the professional world as “NC axes”, “machine axes” or, for short, “axes”. In some cases, this term also includes the components driven by the drives, such as slides or spindles.

[0138] The machine 1 also has a large number of sensors. By way of example, only two sensors 18 and 19 are indicated schematically in FIG. 12. The sensor 18 is a vibration sensor for detecting vibrations of the housing of the grinding spindle 15. The sensor 19 is a position sensor for detecting the position of the axial slide 13 relative to the tool carrier 12 along the Z direction. In addition, the machine 1 includes a large number of other sensors. These sensors include, in particular, further position sensors for detecting an actual position of each linear axis, rotation angle sensors for detecting a rotational position of each axis of rotation, current sensors for detecting a drive current of each axis and further vibration sensors for detecting vibrations of each driven component .

All driven axes of the machine 1 are digitally controlled by a machine control 40. The machine control 40 includes several axis modules 41, a control computer 42 and an operator panel 43. The control computer 42 receives operator commands from the operator panel 43 as well as sensor signals from various sensors of the machine 1 and uses them to calculate control commands for the axis modules 41. It also sends operating parameters to the operator panel 43 for display. The axis modules 41 each provide control signals for one machine axis at their outputs.

A monitoring device 44 is connected to the control computer 42 and carries out various monitoring tasks during operation of the machine 1.

[0141] In FIG. 13 a section from FIG. 1 is shown enlarged. The dressing device 30 can be seen particularly well here. A dressing spindle 32 is arranged on a pivot drive 31, pivotable about a pivot axis C4, on which a disk-shaped dressing tool 33 is clamped, which is provided with specifically generated dressing flank modifications.

[0142] In a helical rolling gear, as is the case with a pairing of an externally toothed spur gear (the pre-toothed workpiece 23) and the grinding worm, there is point contact in non-parallel axes of the pre-toothed workpiece 23 and the grinding worm 16. When rolling through the pairing, the contact point moves along a path determined geometrically by the pairing 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, the path on the grinding worm flank as a snail contact path.

[0143] 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 which has 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 screw flank 161 comes to rest on the screw contact path. This worm modification in the form of a worm ripple along the spiral branch S1 'is now 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 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, as well as 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 selected diagonal ratio such that the worm waviness is specifically mapped onto the tooth flank of the pre-toothed workpiece and the surface structure of the tooth flank is thereby specifically modified.

[0144] A desired tooth flank modification can therefore 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 screw waviness along a spiral branch S1 'on the grinding worm flank 161, which in turn can be calculated for a selected speed ratio a corresponding dressing flank modification can be recalculated, whereby the corresponding dressing flank modification can then be specifically generated according to the manufacturing methods described above.

REFERENCE SYMBOL LIST

[0145] 1 generating grinding machine 11 machine bed 12 tool carrier 13 axial slide 14 shift slide 15 tool spindle 16 grinding worm 161 grinding worm flank 18 acoustic sensor 19 position sensor 20 workpiece carrier 21 workpiece spindle 211 workpiece spindle drive 23 workpiece 30 dressing device 31 swivel device 3 2 dressing spindle 33 dressing tool 330 base body 331 dressing flank surface 40 machine control 41 axis modules 42 Control computer 43 Control panel 44 Monitoring device 50 Conditioning device 51 Conditioning tool 52 Conditioning spindle 53 Conditioning control 60 Negative mold 61 Inner flank 70 Turning tool 71 Turning tool tip 80 Deformation device A Dressing rotation axis B Worm axis C1 Workpiece axis C3 Swivel axis C4 Swivel axis X Feed direction Y Shift direction Z Feed direction K Conditioning rotation axis D Negative shape axis of rotation r radial coordinate r' radial coordinate of the pattern rectangle ϕ Angular coordinate ϕSScrew circumference coordinate rSScrew radial coordinate λr'Radial wavelength ΔϕUOffset angle α Inclination angle d Profile height rAInner radius R1,R2 Radial path U1,U2 Circumferential path S1,S2,S3 Spiral branch

Claims (13)

1. Dressing tool for dressing a grinding worm (16) for the rolling machining of pre-toothed workpieces (23), wherein the dressing tool (33) is designed to rotate about a dressing rotation axis (A) and has a dressing flank surface (331) which forms a circular ring in a projection plane perpendicular to the dressing rotation axis (A), the circular ring having a radial direction with a radial coordinate (r) and defines a circumferential direction with an angular coordinate (ϕ), wherein the dressing flank surface (331) is provided with a specifically generated dressing flank modification, the dressing flank modification projected onto the circular ring being described as a two-dimensional Fourier series depending on the radial coordinate (r) and the angular coordinate (ϕ), characterized, that the Fourier series has at least one non-zero Fourier coefficient for a non-zero circumferential frequency component with respect to the angular coordinate (ϕ). 2. 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 does not have a non-zero Fourier coefficient for a non-zero radial frequency component in the radial direction, such that the specifically generated dressing flank modification is wave-shaped with respect to the circumferential direction and wave fronts in the form of lines of constant phase position which are projected onto the circular ring and are aligned radially. 4. Dressing tool according to claim 1, wherein the two-dimensional Fourier series has at least one Fourier coefficient not equal to zero for a radial frequency component and for a circumferential frequency component not equal to zero, such that the dressing flank modification projects onto the annulus a checkerboard-like structure with arranged offset from one another in a checkerboard-like manner wave crests and wave troughs. 5. Dressing tool according to claim 4, wherein the checkerboard-like structure is aligned such that adjacent wave troughs and wave crests are arranged in the circumferential direction along a spiral branch (S1, S2, S3) which runs 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 targeted generation of the dressing flank modification by means of a conditioning tool (51), in particular a rotating conditioning disk perpendicular to the dressing flank surface. 7. 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 rotation axis (A); Driving the conditioning tool (51) to rotate about a conditioning rotation axis (K) of the conditioning tool (51), and Advancement of the conditioning tool (51) relative to the dressing tool (33) in a direction which has a portion that runs normal to the dressing flank surface, in order to produce the dressing flank modifications by removing material from the dressing flank surface (331). 8. A method for producing a dressing tool (33) according to one of claims 1-5, the method comprising: Producing the dressing tool (33) in a negative process, the negative process comprising: Producing a negative mold (60) by turning out a negative base body; Turning a targeted negative modification into the turned negative shape (60) in such a way that the negative modification causes the dressing flank modification, and/or Generating a mechanical and/or hydraulic tension of the negative base body during turning in such a way that the turned negative mold (60) has a negative modification after the mechanical tension has been released, which causes the dressing flank modification. 9. Method for dressing a grinding worm (16) for the rolling 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 flight of the grinding worm (16). 10. The method according to claim 9, wherein there is a predetermined fixed rotation angle coupling 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 flight. 11. The method according to claim 9, wherein there is a predetermined time-variable rotation angle coupling 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 flight. 12. 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 the rolling machining of pre-toothed workpieces (23) using the method according to one of claims 9-11; 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 with a shift feed speed, and Generating a relative movement between the grinding worm and the pre-toothed workpiece in an axial direction parallel to the workpiece axis (C1) with an axial feed speed, wherein the grinding worm (16) and the pre-toothed workpiece (23) are in a rolling engagement and 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 thereby specifically the surface structure the tooth flank is modified. 13. Method according to claim 12, wherein the dressing tool is a dressing tool (33) according to claim 5 and wherein during dressing there is a predetermined fixed rotation angle coupling between the dressing tool (33) and the grinding worm (16), which is selected such that the spiral branch (S1) is mapped onto a worm contact path becomes, wherein the worm contact path corresponds to a line on which a point of contact between the grinding worm (16) and the pre-toothed workpiece (23) in rolling engagement moves on the grinding worm flank during rolling machining.