Method for profile grinding a periodic structure, in particular a toothing

Abstract

A method for profile grinding a periodic structure, in particular a toothing, using a grinding wheel (10) driven in rotation about its axis of rotation, wherein a first side of the grinding wheel surface is provided with a helical dressing track configuration (G1, G2, G3) in a profiling / dressing process, wherein the dressing track configuration contains multiple tracks.

Description

[0001] METHOD FOR PROFILE GRINDING OF A PERIODIC STRUCTURE, IN PARTICULAR OF A TOOTHING

[0002] The invention relates to a method for profile grinding of a periodic structure, in particular a gear tooth, with a grinding wheel driven to rotate about its axis of rotation, in which the grinding wheel surface on a first side is provided with a spiral dressing track configuration by a profile dressing process, and accordingly to a method of profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear tooth, in which a spiral dressing configuration is generated on the grinding wheel surface of a first side of the grinding wheel by means of one or more dressing tools, in particular one or more rotating dressing roller(s).

[0003] Such methods are well known from the field of profile grinding of gears with dressable grinding wheels and the corresponding dressing tools, particularly in the form of dressing rolls (forming rolls), and are described, for example, in T. Bausch, "Innovative Gear Manufacturing," 3rd edition, pp. 450-457. When a dressing tool in the form of a stationary dresser or a forming roll in the form of a rotating dresser is guided along the grinding wheel to dress it, a helical dressing track configuration is created on the grinding wheel surface due to the rotation of the grinding wheel, very similar to the tracks on a record. The result of the dressing process is the grinding wheel topography. Since the grinding wheel wears down during the grinding process, the required macrogeometry of the grinding wheel is restored by the dressing process.

[0004] Important dressing parameters in this context include, among others, the delivery a e d, the overlap ratio Ud, and, for the abrasive grains, also the speed ratio of the rotational speeds of the dressing tool and grinding wheel. If dressing is performed with Ud=1, the axial dressing feed f a d equals the effective width of the dresser a P d, where the resulting theoretical profile depth Rth exactly corresponds to the dressing setting a e d corresponds. The overlap ratio Ud, defined as the ratio of the effective width of the dresser a P d and the axial dressing feed f a Therefore, d indicates in the image of the aforementioned record tracks whether the tracks are rather wide and deep (Ud=1) or narrower and less deep (u d>1). In practice, dressing coverage for roughing is in the range of Ud = 2, ... 4, and for finishing, Ud = 5, ... , 7. To achieve the lowest possible roughness on profile-ground structures, such as the tooth flanks of gears, higher dressing coverage is therefore considered. Furthermore, counter-rotating dressing contributes to higher surface finishes on the workpiece due to more uniform dressing.

[0005] Furthermore, the accuracy of the dressing process, as well as the accuracy of the profile-ground gear surface, depends on various process and tool parameters, such as the flatness and concentricity of the dressing spindle, the runout of the diamonds in the dressing tool (usually specified relative to the dressing roller's test collar at 20° according to the manufacturer), and assembly errors during roller alignment. Precisely checking and aligning the diamond runout of the dressing roller in the mounted state is difficult and time-consuming, and is therefore often reluctantly performed by users of the dressing and grinding process.

[0006] It goes without saying that there are other machine-related influences on the surface quality of the gear teeth, such as those that can occur during the grinding process, like vibrations during grinding, and the type and supply of coolants or lubricants. Even if these are optimally adjusted, the surface quality and roughness of a tooth flank still depend on the microgeometry of the grinding wheel surface as well as the conditioning of the individual grinding wheel grains through dressing.

[0007] In addition to the measures already mentioned above for improving the final surface quality, the precise alignment of the dressing roll at the test points is also of great importance for good final quality, as are rather lower stroke speeds during grinding, i.e. lower feed rates when feeding the grinding wheel when grinding the gear teeth over their full axial width.

[0008] Furthermore, many influencing parameters are exhaustible in their exploitability; for example, accuracy-enhancing overlap ratios and speed ratios as well as stroke speeds can lead to excessively smooth grinding wheel surfaces, a higher risk of grinding burn, longer dressing times or even longer grinding times.

[0009] Furthermore, the final surface quality of the ground workpiece depends on so many influencing parameters and process variables that good results cannot always be reproduced identically without further ado.

[0010] The invention is based on the objective of improving methods of the type mentioned above with regard to achieving a satisfactory surface quality and uniformity of the ground workpiece with satisfactory robustness despite potentially variable initial conditions.

[0011] This problem is solved by the invention in terms of process engineering by a further development of a method of the type mentioned at the outset, which is characterized in that the dressing track configuration is multi-pass (with number of passes G greater than 1).

[0012] The invention is based on the finding that the microgeometry of the grinding wheel surface, which is generated during dressing, has a greater influence on the surface roughness of the ground gear teeth than would be assumed when considering the profile-forming contact groups of the contact line between the grinding wheel and the workpiece. In particular, the effect of the burrs of the dressing tracks and their orientation on the grinding wheel surface plays a role here, and it has been found within the scope of the invention that a multi-start dressing track configuration, even with the same profile orientation in axial section of the wheel as with a single-start dressed grinding wheel, exhibits an effect referred to here as the over-grinding effect, which ensures greater uniformity of the ground surface.Thus, during grinding, a burr taken over a certain azimuthal extent of the disc covers a radially larger area and can therefore move along a different direction compared to the direction in which the dressing track is formed on the surface of the workpiece, especially when unusually fast grinding feed speeds are used during grinding.

[0013] A preferred further development of the method comprises a first relative rotational position of the grinding wheel relative to a predetermined rotational position of the dressing roll when dressing a first pass of the multi-pass dressing track configuration, and a second relative rotational position of the grinding wheel of the nth order relative to the predetermined rotational position of the dressing roll when dressing a further pass of the multi-pass dressing track configuration adjacent to the first pass in nth order.wherein a first reference angle in the plane of rotation of the grinding wheel is given by the rotational position of a predetermined contact point of the contact line of the profile grinding, lying on a burr associated with the first pass of the burrs appearing in the axial section of the grinding wheel between valleys of the dressing track configuration, and wherein a second reference angle of nth order is rotated relative to the first reference angle by the rotational position difference generated during dressing between the second relative rotational position of nth order and the first relative rotational position, and wherein a first direction of travel is determined by the direction of travel of the position of the burr containing the predetermined contact point, associated with the first pass, over the tooth flank in a snapshot of the grinding wheel at contact in the predetermined contact point,and a second direction of nth order is defined as the connection direction between the given contact point and an image of a further burr located on the grinding wheel surface on the tooth flank during profile grinding, adjacent to the burr assigned to the first pass in nth order at the second reference angle of nth order, wherein, during profile grinding, the second direction of first order deviates from the first direction of profiling due to the rotational position differences generated during dressing. The "n"th order effectively counts the adjacent passes (adjacent in the sense of being next to each other in the axial section of the wheel) or burrs, n being an integer with 1 < n < G-1.

[0014] Preferably, it is further provided that the deviation from the first direction of travel also exists for the second direction of travel of the second order, preferably also for the second direction of travel of the third order.

[0015] It is preferably provided that the deviation(s), relative to the grinding wheel as an angle of rotation, is / are preferably greater than 0.05 ■ Aq>G, n , preferably as 0.1 • AcpG.n, in particular as 0.15 ■ AtpG.n, where Acpc.n is given by 3607(2- n d -G), where nd is the speed ratio of the speed of the rotating driven dressing roll to the speed of the grinding wheel during dressing, and G is the number of gears.

[0016] It can also be provided that the deviation is greater than 0.05 ■ A(p n , preferably as 0.1 • Acp n , especially as 0.15 ■ Acp n , where ACP n is given by 3607(2 n d ), where n d The speed ratio of the speed of the rotating driven dressing roll to the speed of the grinding wheel during dressing.

[0017] It is also provided that a third reference angle of order n is additionally rotated by an angle of 3607(2-n) relative to the second reference angle of order n. d ) is a twisted angle, and a third direction of nth order is determined as the connection direction between the specified contact point and an image of a point on the grinding wheel surface on the tooth flank during profile grinding, adjacent to the burr assigned to the first pass in nth order at the third reference angle nth order, wherein during profile grinding the third direction of first order deviates from the first direction of direction with the rotational position differences generated during dressing.

[0018] Here too, the deviation from the first direction of travel can also apply to the third direction of travel of the second order, preferably also to the third direction of travel of the third order, particularly with the same quantifications of the deviation(s) as specified above. These deviation(s) should apply to at least one contact point, preferably to the contact point at half the profile height, alternatively or additionally, also preferably to the contact point where the first direction of travel on the tooth flank forms the largest angle with the flank line direction.

[0019] The invention is not limited to integer or half-integer speed ratios nd (the speed ratio (nd=n)). a br / n s is) of the rotational speed (n a r) of the rotating driven dressing roller at the rotational speed (n sisThe range of possible speeds is limited (e.g., the grinding wheel during dressing), even though periodic disturbances due to runout or concentricity are easier to identify and analyze at such "simple" speed ratios. The following considerations are particularly relevant when rotational position shifts between individual tracks of multi-track dressing configurations are not desired during dressing. As explained above, however, considering rotational position differences between individual tracks, or phase shifts between individual tracks (relative to the dressing position of the dressing roll), can ensure that a wide range of speed ratios remains accessible. Some unfavorable configurations are explained further below in connection with the description of Fig. 7.This also means that for a speed ratio during dressing, for the maintenance of which, according to a variant described in more detail below, a maintenance of a constant speed ratio can also be considered, a changed speed ratio can also be considered by utilizing the phase shifts.

[0020] In this respect, the present invention also discloses, as an independent protectable method, a method for profile grinding of a gear with a dressable profile grinding wheel which is dressed in the meantime, wherein the dressing is carried out under a predetermined speed ratio (in particular -difference or -ratio), wherein a reduced grinding wheel size caused by the continuous dressing is adjusted by adjusting the speed ratio to maintain the speed ratio, and in this adjustment the setting of the phase shift between individual tracks of the multi-track dressing configuration is changed during dressing.

[0021] In this respect, it is preferred in the invention if a phase shift other than zero is set between successive gears.

[0022] In one possible embodiment, it is provided that the rotational speed ratio (nd=n)a br / n s is) of the rotational speed (n a br) of the rotating driven dressing roller to the rotational speed (n s (is) maintains a distance of an integer ratio between the grinding wheel and the surface during dressing, wherein the difference in the rotational speed ratio to the nearest integer ratio is at least 0.15, preferably at least 0.2. This avoids the tendency for a proportion of flatness or runout attributable to the grinding wheel surface (normal runout) to generate a wave structure in the grinding wheel microgeometry, which would be detrimental to the over-grinding effect.

[0023] In this sense, it is also possible that deviations of the speed ratio (nd) from the nearest half-integer speed ratio are less than 0.3, preferably less than 0.2, more preferably less than 0.15, and particularly less than 0.1. Half-integer speed ratios are values ​​of n d =k+0.5, k from the set of integers (or natural numbers if, for the present invention, only the magnitudes of the rotational speeds are considered with regard to this aspect, regardless of counter-rotation / co-rotation). This reduces a tendency towards unevenness.

[0024] Half-integer speed ratios are also considered advantageous by the invention, completely independent of the number of threads of the dressed grinding wheel, i.e., also for single-start dressed grinding wheels, in order to reduce the effects of normal runout. The invention thus discloses, as a separate and independently patentable method, a process for profile grinding of a periodic structure, in particular a gear tooth, with a grinding wheel driven rotating about its axis of rotation, in which the grinding wheel surface on a first side is provided with a spiral dressing track configuration by a profile dressing process, wherein during the dressing process the deviation of the speed ratio (nd) from the nearest half-integer speed ratio is less than 0.1, preferably less than 0.05, and in particular a half-integer speed ratio is present.The invention also discloses as independently applicable and independently patentable a method for profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear tooth, in which a spiral dressing configuration is generated on the grinding wheel surface of a first side of the grinding wheel by means of one or more dressing tools, in particular one or more rotatingly driven dressing roller(s), wherein during the dressing process a deviation of the rotational speed ratio (n <j) vom nächstgelegenen halbzahligen Drehzahlverhältnis geringer ist als 0,1 , bevorzugt geringer als 0,05, und insbesondere ein halbzahliges Drehzahlverhältnis vorliegt.Even even numbers of gears can lead to a noticeable slippage effect; in an even more preferred embodiment, the number of gears in the multi-speed transmission is odd and, in particular, selected from group 3, 5, or 7. This can also contribute to increased smoothness.

[0025] In this context, it is also provided that the multi-start configuration is a five-start configuration and the speed ratio deviates from 1.5 by no more than 0.3, preferably less than 0.2, more preferably no more than 0.15, and in particular no more than 0.1, or that the multi-start configuration is a seven-start configuration and the speed ratio deviates from 1.5 or 2.5 by no more than 0.3, preferably less than 0.2, and in particular no more than 0.15, and in particular no more than 0.1, respectively. With such configurations, the effects of a component attributable to flatness or runout error tangential to the grinding wheel surface (tangential runout) can be associated with less potentially adverse effects on the over-grinding effect.

[0026] Particularly when the aim is to reduce the effects of tangential runout, integer speed ratios are considered advantageous by the invention, even completely independent of the number of threads of the dressed grinding wheel, i.e., also for single-start dressed grinding wheels. The invention thus discloses, as a separate and independently patentable method, a process for profile grinding of a periodic structure, in particular a gear tooth, with a grinding wheel driven rotating about its axis of rotation, in which the grinding wheel surface on a first side is provided with a spiral dressing track configuration by a profile dressing process, wherein during the dressing process the deviation of the speed ratio (nd) from the nearest integer speed ratio is less than 0.1, preferably less than 0.05, and in particular an integer speed ratio is present.The invention also discloses as independently and is independently patentable a method for profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear, in which a spiral dressing configuration is generated on the grinding wheel surface of a first side of the grinding wheel by means of one or more dressing tools, in particular one or more rotating driven dressing roller(s), wherein during the dressing process a deviation of the speed ratio (nd) from the nearest integer speed ratio is less than 0.1, preferably less than 0.05, and in particular an integer speed ratio is present.

[0027] In a suitable embodiment, the spiral shape of the dressing track configuration is of the Archimedean spiral type. This promotes a uniform burr height and thus a global uniformity of the grinding effect.

[0028] Based on the above preferred designs for the speed ratio, the invention also provides a further teaching with regard to further considerations concerning the speed ratio, whether viewed over the lifetime of a grinding screw or over a dressing pass, and places this teaching under protection.

[0029] While conventional dressing methods ensure that the speed ratio of the rotational speed of the dressing roll and the grinding wheel remains constant at a reference radius or reference diameter over the service life of the grinding wheel, the invention represents a completely different teaching in this respect.

[0030] Because of the relationship vumiau.abr / vumiaut, sis = n d ■ (D a br / D ref, sis) During conventional dressing, the rotational speed ratio changes due to its adjustment to the decreasing grinding wheel (reference) diameter. This should be counteracted as much as possible, so that, in accordance with this aspect, and regardless of the common practice of dressing, a method for profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear, is initially disclosed as an independent teaching worthy of protection. In this method, a spiral dressing configuration is generated on the grinding wheel surface of a first side of the grinding wheel by means of one or more dressing tools, in particular one or more rotatingly driven dressing roll(s), and the rotational speeds of the dressing roll and the grinding wheel are controlled during dressing in such a way that...that the speed ratio of the rotational speed of the driven dressing roll to the speed of the grinding wheel remains at least approximately equal with respect to commensurability effects during dressing, in that a distance of not less than an integer ratio and / or not more than a half-integer ratio is not undercut, in particular with respect to the same integer / half-integer ratio, wherein in particular the speed ratio remains essentially constant, on the one hand over the service life of the grinding wheel (uniform dressing for grinding larger batches of workpieces), and / or within a dressing pass (additional uniformity in the profile direction).

[0031] In any case, this should apply to the dressing of the grinding wheel, which dresses the grinding wheel for grinding the surface-determining grinding passes for the workpiece (finishing).

[0032] Furthermore, the invention provides a way to maintain a desired speed situation for dressing (influencing the abrasive grains) consistently, despite a substantially constant speed ratio. However, the invention focuses less on the speed ratio itself and more on the speed difference.The invention provides a method for profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear, in which a spiral dressing configuration is generated on the grinding wheel surface of a first side of the grinding wheel by means of one or more dressing tools, in particular one or more rotatingly driven dressing roller(s), in which the rotational speeds of the dressing roller and the grinding wheel are controlled during dressing in such a way that a change in the speed difference between the wheel and the roller at a reference radius of the grinding wheel is counteracted due to the reduced diameter of the grinding wheel over the service life of the grinding wheel through continuous dressing, in particular primarily by a common increase in both rotational speeds.

[0033] In any case, the invention provides a method for profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear, in which a spiral dressing configuration is generated on the grinding wheel surface of a first side of the grinding wheel by means of one or more dressing tools, in particular one or more rotatingly driven dressing roller(s), in which the rotational speeds of the dressing roller and the grinding wheel are controlled during dressing in such a way that in one dressing pass a change in the speed difference between the wheel and the roller due to the changing diameter of the grinding wheel over the grinding wheel profile in the profiling area is counteracted, in particular primarily by a common change in the direction of the two rotational speeds.

[0034] This teaching is therefore preferably considered for multi-start dressed grinding wheels, but is also considered advantageous for single-start dressed grinding wheels and is accordingly independently worthy of protection.

[0035] Thus, considering the lifetime of the tool and / or during a dressing cycle due to the radial change of the dressing contact, the speed difference can at least be kept constant within certain limits, or at least its change (automatically following the diameter change) can be counteracted. If necessary, this can be achieved by superimposing their effects, for example, by only a slight change in the speed ratio through a slow relative increase in the grinding wheel speed while simultaneously increasing both speeds absolutely. In this superposition, this would mean that both speeds increase, but not directly proportionally; rather, the grinding wheel speed increases somewhat more than that of the dressing roller.

[0036] This aspect, considered over the lifetime of the wheel, is also preferably used for the dressing process with which the grinding wheel is dressed for its surface-determining finishing passes.

[0037] In another preferred process design, it is provided that the rounding (R a The thickness (br) of the dressing area of ​​the dresser is greater than 1.5 mm, preferably greater than 2 mm, and particularly greater than 2.5 mm. This counteracts an impairment of the over-grinding effect that would otherwise be caused by a tangential impact.

[0038] In a further particularly preferred method design, the focus is on ensuring that the height of the burrs on the grinding wheel profile is as uniform as possible (burr height calculated over a predetermined target profile). In this context, it is preferred to work with significantly lower overlap ratios than for conventional dressing methods aimed at high machining accuracies. Thus, Ud* values ​​of less than 3, preferably less than 2.5, particularly less than 2, even less than 1.8, and even less than 1.6, particularly less than 1.4, are quite acceptable. This increases the burr height and thus ensures a more favorable ratio of burr height divided by the amplitude of any wave-like periodic disturbance caused by flatness or runout during dressing. This also leads to a better over-grinding effect. Preferably, the target burr height (h) resulting from the setting of the dressing parameters is spUr) at least 1 pm, preferably at least 1.5 pm, more preferably at least 2.0 pm, more preferably at least 2.5 pm, in particular at least 3 pm, where values ​​of 4 pm or even over 5 pm are also considered.

[0039] It is understood that all previously described properties of the microgeometry and, in particular, the multi-turn spiral dressing track configuration are preferably applied equally to the other side of the grinding wheel.

[0040] In this regard, it is preferably provided that the dressing track configuration has the same chirality on both sides of the grinding wheel. The chirality, as defined in the present invention, corresponds to the handedness when viewed from the perspective of the grinding side (i.e., opposite viewing directions with respect to the two sides). If the spiral rotates counterclockwise from the grinding wheel shoulder to the grinding wheel head, the chirality is left-handed or positive (mathematical direction of rotation) as defined in this application; if the spiral rotates clockwise from the grinding wheel shoulder to the grinding wheel head, the chirality is right-handed or negative as defined in this invention. Accordingly, either the combination (+ / +) or the combination (- / -) is preferably chosen for the chiralities. In this way, a more uniform grinding effect is achieved during double-sided profile grinding.

[0041] The processes and microgeometry of the dressed grinding wheel described above, primarily for dressing, naturally also apply to the grinding process and the design of the grinding wheel surfaces used for this purpose.

[0042] Regarding the speed ratio n again, especially when the aim is to make the effects of tangential and normal runout more uniform, speed ratios with a difference of both integer and half-integer speed ratios are also considered advantageous according to the invention, completely independent of the number of threads of the dressed grinding wheel, i.e., also for single-start dressed grinding wheels. The invention thus discloses, as a separate and independently patentable process, a method for profile grinding of a periodic structure, in particular a gear tooth, with a grinding wheel driven rotating about its axis of rotation, in which the grinding wheel surface on a first side is provided with a spiral dressing track configuration by a profile dressing process, wherein during the dressing process a deviation of the speed ratio (n) dThe invention also discloses, as a separate and independently patentable method, a method for profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear, in which a spiral dressing configuration is generated on the grinding wheel surface of a first side of the grinding wheel by means of one or more dressing tools, in particular one or more rotatingly driven dressing roller(s), wherein during the dressing process a deviation of the speed ratio (nd) from the nearest integer speed ratio and from the nearest integer speed ratio is in each case greater than 0.15, preferably greater than 0.2.

[0043] Furthermore, the inventive method is protected in control engineering form by a computer program product.

[0044] In terms of the device technology, the invention provides a dressing unit for profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear, with a grinding spindle to rotate the grinding wheel, a positioning device for positioning at least one dressing tool to the grinding wheel and a control device that controls the dressing unit in at least one operating mode to carry out a method according to one of the aforementioned aspects.

[0045] In the machine-technical implementation, dependencies or couplings are therefore preferably provided, namely a first coupling from the rotational position of the dressing roll to the rotational position of the grinding wheel, a second coupling from the rotational position of the grinding wheel to an axial position of the dressing roll and / or a third coupling from the rotational position of the grinding wheel to a radial position of the dressing roll (the latter two respectively with reference to the grinding wheel rotation axis).

[0046] Furthermore, the invention provides a gear grinding machine for profile grinding in which a dressing unit, as described above, is integrated into the profile grinding machine, and / or with an internal grinding head for grinding internal gears. In a preferred embodiment, the profile grinding machine could already have the dressing unit integrated and, in particular, could have a control system that controls both the dressing unit and the profile grinding. However, the dressing could also, in principle, be carried out outside the profile grinding machine on a separate dressing unit / dressing machine.

[0047] Further features, details and advantages of the invention will become apparent from the following description with reference to the accompanying figures, of which

[0048] Fig. 1 schematically shows a dressing process in an axial section over a section of the profile area,

[0049] Fig. 2 shows a representation of a multi-start dressed grinding wheel,

[0050] Fig. 3 shows roughness measurements of gear surfaces that were ground with a single-flute dressed side.

[0051] Fig. 4 shows a comparison of roughness representations in the profile direction,

[0052] Fig. 5 shows roughness representations for different speed ratios at higher gear ratios, and

[0053] Fig. 6 shows roughness representations for different speed ratios with an even higher number of gears,

[0054] Fig. 7 shows a rough schematic representation of degree profiles on a tooth flank, and

[0055] Fig. 8 shows rotational position differences on a grinding wheel.

[0056] Fig. 1 shows an axial section of a (schematically represented as a full circle) area of ​​the profiling zone of a grinding wheel, along with an area of ​​a dressing roller 20, which illustrates the formation of a dressing track configuration on the surface of the grinding wheel 10. To the right of the depicted area of ​​the dressing roller, one can see how much material is removed from the grinding wheel in one dressing pass, and to the left of this, a cross-section through the forming dressing tracks. The height of the burrs of the tracks, hspur, is less than the height of the removed material area; however, if dressing were performed with Ud = 1, correspondingly higher and wider tracks would result. In contrast to conventional dressing methods, the grinding wheel 10 is dressed with multiple passes. This is illustrated in Fig. 1 by the fact that the adjacent tracks in the axial section belong to different passes.In this embodiment, this is illustrated for a three-start trained worm gear, G1 designates a track belonging to the first start, G2 to the second start, G3 to the third start and G1 again to the first start.

[0057] Since the dressing feed between passes of the track belonging to a thread is three times greater for the case shown in Fig. 1 than in the case of a single-start spiral, according to the usual definition of the contact ratio, the contact ratio for three-start dressing would only be one-third of the contact ratio for single-start dressing. In order not to have to deviate from the familiar concept that for u d (catchy) = 1 the delivery ei d If the geometric profile depth Rth (or hspur in Fig. 1) were equal, a cover ratio u modified according to the number of threads would be used. d* introduced, which is defined as the ratio of the effective width of the dresser and the axial dressing feed, but multiplied by the number of threads G, where the axial dressing feed is the dressing feed related to a specific track, so that the previous conventions can also be retained in this respect, namely the relationship between the speed at which the dresser is moved relative to the grinding wheel and the dressing feed. In the case of single-start dressing, of course u d * = u d When the term "coverage" is used below, the definition for multi-start dressed grinding wheels is as follows: d * meant according to the above definition, and in representations such as in Fig. 1 an hs pU r, which corresponds to the conventional image, i.e., with an overlap of 1, corresponds to the dressing feed of the dressing tool.

[0058] As is immediately apparent to those skilled in the art, Rabr is not specifying half the diameter of the rotating dressing roller (if the dressing tool is designed as a form roller), but rather the radius of the rounding of the dressing area of ​​the roller, as explained by Bausch in the aforementioned reference. The depiction of a full circle is purely illustrative, and the axis of rotation in the case of a form roller is naturally not orthogonal to the plane of the paper in Fig. 1 and through the center of the depicted circle, but, as usual, parallel to the axis of rotation of the grinding wheel. In the case of a non-rotating dressing tool, R corresponds to a t>r also corresponds to the radius of curvature of the rounding of the dressing area.

[0059] Fig. 2 schematically illustrates this multi-start dressing track configuration, here for an example with 3 starts. Figures 3a, 3b, and 3c show roughness measurements in the profile direction of a gear tooth ground with a conventionally single-start dressed grinding wheel, in which periodic substructures are visible that affect the overall roughness. For Fig. 3a, Ud = 4 and R a br= 0.5 mm and a rotational speed ratio nd of about 0.9 and ground with a feed rate of about 4200 mm / min.

[0060] In Fig. 3b, the speed ratio is 1.5 compared to Fig. 3a, instead of 0.9. In Fig. 3c, the speed ratio is 2.5, the overlap is lower, namely only 1.3, and the feed rate during grinding is approximately 664 mm / min. Despite the low feed rate, a periodic substructure is visible alongside other roughness (measured result Rz 3.3 pm, shown here are five consecutive sections with Lc 0.8 mm). A regularity influencing the roughness exists despite the seemingly random appearance of the surface roughness.

[0061] As shown in Figures 3a to 3c, which depict the roughness of the workpiece flanks after profile grinding in the profile direction and present it as a measurement diagram, at least partially regular deviations are discernible, which relatively influence the surface structure and its roughness values ​​of the workpiece flank. These regular deviations occur partly only in individual sections of the measurement diagram, or over the entire length of the measurement diagram.

[0062] These structures are often too regular to be attributed to scratches caused by the grinding wheel's grain structure. Nor can they always be explained by vibrations during the grinding stroke. Rather, it has been recognized that in many cases they are caused by a surface geometry of the grinding wheel that develops during the dressing process and is transferred to the workpiece flank. This leads to increased roughness values, which have often been addressed by adjusting the process parameters.

[0063] However, according to the invention, such structures can be reduced by means of a multi-start dressed grinding wheel. A multi-start dressed grinding wheel influences the transfer of the grinding wheel's surface geometry to the workpiece flank. This allows for the same or even better surface finishes and roughness on the workpiece flank, even with shorter machining times (and their cycle time) and process parameters that would otherwise be less favorable for the surface and roughness of the workpiece flank, as illustrated below with reference to Fig. 4. Fig. 4 schematically shows how the roughness changes in the profile direction for a gear tooth ground on a multi-start dressed grinding wheel.

[0064] Figure 4a, top left in Fig. 4, shows a roughness representation for a single-start dressed grinding wheel, here with nd of 1.5, in comparison to the still not optimal representation in Fig. 4b for a three-start dressed grinding wheel. The improved roughness effect is more effective when comparing Figures 4c and 4d, where again on the left (Fig. 4c) a roughness representation on the workpiece gear teeth with 1 start and nd of 2.5 is shown, and for comparison, to the right in Fig. 4d, the roughness representation for the three-start dressed worm (also with nd = 2.5). Due to the effect of the improved overgrinding, the roughness is hardly visible in Fig. 4d.

[0065] Fig. 5 shows a representation corresponding to Fig. 4 of the roughness of a gear flank (in profile direction) for selected cuts at different speed ratios in nd = 0.5, 1.5, 2.5 and 3.5, of five-start dressed grinding wheels. Except for the value where the speed ratio corresponds exactly to half the number of starts, the considered regular structures influencing the roughness profile are essentially completely ground over.

[0066] Fig. 6 shows another representation corresponding to Fig. 5 for a profile of the gearing ground with a seven-start dressed grinding wheel, with a speed ratio increasing from left to right (0.5, 1.5, 2.5, 3.5).

[0067] With an even-numbered speed ratio, the grinding effects achieved to this extent do not occur, especially when runout and concentricity primarily act as normal runout, which is difficult to control. Therefore, only half-integer speed ratios are shown in Figures 3 to 6.

[0068] It is understood that the invention is not limited to precisely half-integer speed ratios. Rather, speed ratios of any kind can be used, including those between integer and half-integer ratios, whereby, as quantitatively specified above, a certain minimum distance between integer speed ratios and, in particular, a certain maximum distance between half-integer speed ratios are preferred in some embodiments. In a specific embodiment, a grinding wheel has an outer diameter of 300 mm at the beginning of its service life and is dressed to an outer diameter of 200 mm over the course of its service life, with a profile area of ​​approximately 50 mm. The grinding wheel is dressed with seven starts, and the speed ratio during dressing is set to a constant 2.5 over the service life of the grinding wheel.Such a maintained speed ratio also differs from conventional dressing, in which the speed ratio is kept constant at a predetermined reference radius, resulting in a significant change in the speed ratio over the grinding wheel's service life. To achieve a constant speed ratio over the grinding wheel's service life, the absolute speeds can be increased without changing the speed ratio. This preferably maintains an equal speed difference between the dressing roll and the grinding wheel. Furthermore, the speed coupling is designed such that the speed difference remains at least approximately constant across the grinding wheel's profiling area.Furthermore, while the dressing roll moves from the grinding wheel head towards the grinding wheel shoulder, the rotational speeds can be increased simultaneously, yet the speed ratio can be maintained at the same or at least approximately the same. This results in even greater uniformity, which translates into increased consistency of gear quality within a batch of gears.

[0069] With reference to Fig. 7, further relationships between the dressing process and the profile grinding process will now be explained. Fig. 7 schematically depicts a region of a tooth flank of a profile-ground gear, where the flank line direction from left to right is shown as horizontal, and the vertical axis represents the profile direction of the tooth flank. KP denotes a selected contact point that lies on a (not shown) contact line at a specific time. The solid dot indicates that a (high) degree of the multi-start dressing track configuration is present at the contact point on the grinding wheel side, for example, in the case of a first start G1.

[0070] During profile grinding, the grinding wheel rotates while being advanced. Figure 7 shows the feed between contact point KP and contact point KP' that occurs during one grinding wheel revolution. Accordingly, after one grinding wheel revolution, the grinding wheel-side contact point KP is in contact again and is labeled KP in Figure 7. 1 The horizontal line thus corresponds to the circumferential direction of the grinding wheel on the grinding wheel side.

[0071] Due to the multiple passes (in the example shown in Fig. 7, the number of passes G is 7), the passes of the subsequent passes G2 to G7 are located on the flank line between KP and KP' at the same profile height. Furthermore, the image of the burrs as the grinding wheel rotates and is advanced is shown as lines in Fig. 7. During one revolution of the grinding wheel, the image of the burr on the flank of the first pass G1 thus moves by one pass height in the profile direction, i.e., by 360° multiplied by the track pitch Ar / AO (the radial offset Ar of the dressing track of the first pass when rotating around AS). The tangent of the angle βcang shown in Fig. 7 is therefore the quotient of this track pitch and the feed per rotation angle of the profile grinding wheel during profile grinding.

[0072] Due to runout or concentricity errors during dressing, the sequence of burrs and valleys of the dressing track configuration produced on the grinding wheel will not be perfect in the sense that the axial section shows the ideal situation depicted in Fig. 1. Rather, normal and tangential runout cause deviations in burr heights and positions. These deviations vary, depending on the rotational speed ratio nd, essentially periodically between two extremes. One extreme is referred to here as the "high burr" and is symbolized by the filled dot, while the other extreme is referred to as the "low burr" and is symbolized by a hollow circle.

[0073] As can be seen in Fig. 7, if one traces the image of this burr along the first gear G1, there is a distance between these two extremes. The distance between the two extremes, relative to a rotational angle, is determined by the rotational speed ratio during dressing and is 3607(2n). d That is, one rotation of the grinding wheel by 3607(2n d ) brings one extreme to the angular position where the other extreme was before the rotation. A rotation of 3607n d This brings one extreme back into the rotational position of the same extreme; therefore, there is no change in the image of the structure, and the statements made regarding the changes in rotational angle and differences in rotational position can be expressed as "modulo 3607n". d " understand.

[0074] In the illustration in Fig. 7, the rotational speed ratio n d 1.875, one would have had an n instead. dIf 2 is used, the next filled point (high ridge) emanating from the contact point KP would be located on the ridge image G1 in Fig. 7 exactly above KP".

[0075] The explanatory illustration in Fig. 7 depicts a case in which, during dressing from one pass to the next, an additional displacement in the rotational position of the grinding wheel relative to the rotational position of the dressing roll was set. Without such a set rotational displacement or differential, the high burr present at KP in the illustration of Fig. 7 would be located essentially below KP at the point where a cross is drawn in Fig. 7 (slightly shifted circumferentially relative to KP). However, the high burr, labeled P2 in Fig. 7, is displaced by the rotational differential relative to the grinding wheel.

[0076] For the next-but-one burr (at G3, second order), there is also no high burr below KP. Rather, the set rotational position difference is such that, in Fig. 7, the high burr of the next-but-one burr (P3) is located on the horizontal line, or, with respect to the grinding wheel, has the same radial position as the grinding wheel contact point KP. In Fig. 7, the horizontal line thus represents the connection direction between the contact point KP and the image of the next-but-one burr at the second second-order reference angle, and therefore the second second-order direction VL2-2. Since the low burr (the other extreme) is located at the intersection between the adjacent channel (G2, first order) and the horizontal line, the horizontal line also corresponds to the third first-order direction VL3-1 in this case. For the [unclear] in Fig.The situation shown in section 7 is the angle of rotation difference between two adjacent ridges (passages) 360° / G+3607(2nd), which is approximately 147.4°.

[0077] The line marked VL1 in Fig. 7 represents the first direction of travel, which results from the position of the burr of the grinding wheel containing the contact point KP above the tooth flank in a snapshot at contact at KP (and depends, among other things, on the pitch). This first direction of travel is also curved, varying across the profile height, as is usual when grinding helical gears, as soon as the contact line does not run radially on the grinding wheel, but is curved.

[0078] For illustrative purposes, the rotational position differences for the image in Fig. 7 are chosen such that an irregularity occurs along the horizontal (or VL3-1 or VL2-2) at the transition of the passage of the 6th adjacent channel (at G7) and KP". In other, not shown, but preferred embodiments, such an irregularity along a second or third direction can be avoided by adjusting the rotational position differences and, if necessary, the angle β.

[0079] It is understood that the representation in Fig. 7 is purely illustrative and neither the distances nor the angles necessarily have any relation to the actual quantities occurring.

[0080] The illustration in Fig. 7 shows that one can proceed in the following exemplary manner.

[0081] As part of the process design, the pivot angle of the profile grinding wheel's axis of rotation relative to the gear's axis of rotation is determined (usually measured relative to the orthogonal plane of the gear's axis of rotation, i.e., 0° pivot angle for spur gears). From this, the profile design for the profile grinding wheel and the shape of the contact line are typically derived.

[0082] From the tool data (shoulder radius of the grinding wheel, head radius of the grinding wheel, the contact line shape and the track pitch determined based on the dressing parameters), it is determined where, viewed over the profile height, the locally changing angle β structure assumes the greatest value.

[0083] In a first virtual intermediate calculation, a first virtual rotational position difference can be determined until either one extreme (or the other extreme) lies in the circumferential direction for each turn (3607G). This corresponds computationally to the image of a deformation of the spiral on the grinding wheel into a circle.

[0084] A second virtual rotational position difference (36072nd) introduces an asynchrony along the circumferential direction (or the horizontal line in Fig. 7), resulting in the situation shown in Fig. 7. A further virtual rotational position difference between the gears simulates a case considered unfavorable, in which there is no significant deviation of the second or third first-order direction of travel from the first direction of travel. A further virtual rotational position difference between the gears, by a multiple (factor m) of an angular increment At cn, superimposed on all the previously mentioned rotational position differences, yields a total rotational position difference from one gear to the next, under which the dressing process can be controlled. The multiple m could be an integer to counteract the irregularities explained above (during the transition from gear G7 back to G1).If G were an even number, odd factors m would be more favorable.

[0085] This design, based on the largest occurring angle of β-structure, also results in a good grinding effect at other profile heights with low β-structure.

[0086] Further favorable conditions are obtained if a parameter value T is greater than or equal to 0.05 / G, preferably greater than or equal to 0.1 / G, more preferably greater than or equal to 0.15 / G and less than or equal to 1-0.05 IG, preferably less than or equal to 1-0.1 / G less than or equal to 1-0.15 / G (with the number of threads G), which parameter value T is defined as the decimal slope of the quotient of WGang-sis and 3607(2nd), where wcang-sis corresponds to the rotation angle of the grinding wheel by which the grinding wheel rotates during profile grinding during a feed distance which lies between the intersection points of the image of a burr (G2) adjacent to a contact point KP with, on the one hand, a line emanating from this contact point (KP) along the first direction of travel and, on the other hand, a line emanating from this contact point (KP) in the flank line direction.

[0087] Figure 8 shows another top view of a grinding wheel to illustrate the rotational position difference, but instead of seven passes as in Figure 7, it shows only three passes as in Figure 2 for illustrative purposes. If, for example, a point on the grinding wheel corresponding to the contact point KP is located at a first reference angle qji, which is generated here by dressing with a specific relative rotational position to the rotational position of the dressing roll, then, without a rotational position difference between G1 and G2, the corresponding nearest high burr on G2 would also be at an angle yji, since any disturbance during dressing affects both passes G1 and G2 equally. However, if a phase shift Ai is set relative to the rotational position of the dressing roll that is not zero, the position of this point P2 shifts azimuthally by the rotational position difference relative to the second reference angle (first order).

[0088] Preferably, to generate a uniformly distributed recording of the disturbance structure, the rotational position difference between adjacent gears is set to the same.

[0089] The invention is not limited to the details and features shown in the individual embodiments. Rather, the individual features of the above description as well as of the following claims can be essential, individually and in combination, for the realization of the invention in its various embodiments.

Claims

Claims 1. Method for profile grinding of a periodic structure, in particular a gear, with a grinding wheel (10) driven to rotate about its axis of rotation, in which the grinding wheel surface on a first side is provided with a spiral dressing track configuration by a profile dressing process, characterized in that the dressing track configuration is multi-turn.

2. Method of profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear, in which a spiral dressing configuration is produced on the grinding wheel surface of a first side of the grinding wheel by means of one or more dressing tools, in particular one or more rotatingly driven dressing roll(s) (20), characterized in that the dressing track configuration is multi-turn.

3. Method according to claim 2, comprising a first relative rotational position of the grinding wheel relative to a predetermined rotational position of the dressing roll when dressing a first pass (G1) of the multi-pass dressing track configuration, and a second relative rotational position of the grinding wheel of the nth order relative to the predetermined rotational position of the dressing roll when dressing a further pass (G2, G3, ...) of the multi-pass dressing track configuration adjacent to the first pass in the nth order, wherein a first reference angle in the plane of rotation of the grinding wheel is given by the rotational position of a predetermined contact point (KP) of the contact line of the profile grinding, which lies on a burr associated with the first pass of the burrs appearing between valleys of the dressing track configuration in the axial section of the grinding wheel and a second reference angle of nth order is rotated relative to the first reference angle by the rotational position difference generated during dressing between the second relative rotational position of nth order and the first relative rotational position, and wherein a first direction of travel (VL1) is determined by the direction of travel of the position of the burr containing the specified contact point and associated with the first thread over the tooth flank in a snapshot of the grinding wheel at contact in the specified contact point, and a second direction of travel of nth order (VL2-n) is determined as the connection direction between the specified contact point and an image of a further burr located on the grinding wheel surface on the tooth flank during profile grinding, adjacent to the burr associated with the first thread in nth order at the second reference angle of nth order.where, during profile grinding, the second first-order direction of rotation (VL2-1) differs from the first direction of rotation (VL1) due to the rotational position differences generated during dressing.

4. Method according to claim 3, wherein the deviation from the first direction of travel also exists for the second direction of travel of the second order, (VL2-2), preferably also for the second direction of travel of the third order (VL2-3).

5. A method according to claim 3 or 4, wherein a third reference angle of nth order is the angle rotated by an additional rotation angle of 3607(2 nd) relative to the second reference angle of nth order, and a third direction of nth order (VL3-n) is defined as the direction of connection between the predetermined contact point and an image of a further burr located on the grinding wheel surface on the tooth flank during profile grinding, adjacent to the burr associated with the first pass in nth order at the third reference angle of nth order. where, during profile grinding, the third first-order direction (V3L-1) differs from the first direction (VL1) due to the rotational position differences generated during dressing.

6. Method according to claim 5, wherein the deviation from the first direction of travel (VL1) also exists for the third direction of travel of the second order (VL3-2), preferably also for the third direction of travel of the third order (VL3-3).

7. Method according to any one of claims 3 to 6, wherein the deviation(s), with respect to the grinding wheel, is / are preferably greater than 0.05 • Acpc.n, preferably greater than 0.1 ■ AcpG.n, in particular greater than 0.15 ■ A <pc,n, wobei AcpG.n gegeben ist durch 3607(2 n d -G), where n d The speed ratio of the speed of the rotating driven dressing roll to the speed of the grinding wheel during dressing is, and G is the number of threads.

8. Method according to claim 7, wherein the deviation, with respect to the grinding wheel, is greater than 0.05 ■ Acp n , preferably as 0, 1 ■ Acp n , especially as 0, 15 ■ Acp n , where ACP n is given by 3607(2-n d )t, where n dThe speed ratio of the speed of the rotating driven dressing roll to the speed of the grinding wheel during dressing.

9. Method according to any one of claims 2 to 8, wherein the number of turns of the multi-turn mechanism is odd and is selected in particular from the group 3, 5 or 7.

10. Method according to claim 9, wherein the multi-start configuration is a five-start configuration and the speed ratio does not deviate by more than 0.3, preferably less than 0.2, further preferably not more than 0.15, in particular not more than 0.1 from 1.5, or the multi-start configuration is a seven-start configuration and the speed ratio does not deviate by more than 0.3, preferably less than 0.2, in particular preferably not more than 0.15, in particular not more than 0.1 from 1.5 or from 2.

5.

11. Method according to any one of claims 2 to 10, wherein the spiral shape of the dressing track configuration is of the Archimedean spiral type.

12. Method of profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear, in which a spiral dressing configuration is produced on the grinding wheel surface of a first side of the grinding wheel by means of one or more dressing tools, in particular one or more rotatingly driven dressing roll(s), in particular according to one of the claims 2 to 11, in which the speeds of the dressing roller and the grinding wheel are controlled during dressing in such a way as to counteract a change in the speed difference between the wheel and the roller at a reference radius of the grinding wheel due to the reduced diameter of the grinding wheel over the lifetime of the grinding wheel through continuous dressing, in particular primarily by a common increase of both speeds.

13. Method of profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear, in which a spiral dressing configuration is generated on the grinding wheel surface of a first side of the grinding wheel by means of one or more dressing tools, in particular one or more rotatingly driven dressing roller(s), in particular according to one of claims 2 to 11, in which the rotational speeds of the dressing roller and the grinding wheel are controlled during dressing in such a way that in one dressing pass a change in the speed difference between the wheel and the roller due to the changing diameter of the grinding wheel over the grinding wheel profile in the profiling area is counteracted, in particular primarily by a common change in the direction of the two rotational speeds.

14. Method according to one of claims 2 to 13, wherein the grinding wheel is also provided on its second side with a spiral dressing configuration on the grinding wheel surface, in particular also there according to the characterizing features of one or more of claims 3 to 13.

15. Method according to claim 14, wherein the chirality of the dressing configuration is the same on both sides of the grinding wheel.

16. Method according to claim 1, wherein the profiling dressing process for generating the spiral dressing track configuration is carried out according to one of claims 3 to 15.

17. Computer program product which, when executed on a profile grinding machine and / or dressing unit, controls the profile grinding machine / dressing unit to execute a method according to any one of claims 1 to 16.

18. Dressing unit for profiling / dressing a grinding wheel designed for profile grinding of a periodic structure, in particular a gear, with a grinding spindle to rotate the grinding wheel, a positioning device for positioning at least one dressing tool for the grinding wheel and a control device that controls the dressing unit in at least one operating mode for carrying out a method according to one of claims 2 to 16.

19. Gear grinding machine for profile grinding of a periodic structure, in particular a gear, comprising a workpiece spindle for clamping a gear, a tool spindle for positioning the grinding wheel for the gear and a control device that controls the profile grinding machine in at least one operating mode for carrying out a method according to claim 1 or claim 16.

20. Profile grinding machine according to claim 15, wherein a dressing unit according to claim 18 is integrated into the profile grinding machine, and / or with an internal grinding head for grinding internal gears.

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