Method for Producing Tooth Flank Modifications on Toothing of Workpieces and Tools for Performing Said Method

The invention relates to a method for producing tooth flank modifications on toothing of workpieces, in which the workpiece and a tool are moved relative to one another and, as a result, material is removed from the tooth flank (3) of the workpiece. Different tooth flank modifications are generated on teeth (1) of the workpiece by means of a continuously rolling manufacturing process, by the tool comprising individually different tool profile geometries which generate the different tooth flank modifications on the teeth (1) of the workpiece. The tool can be a dresser with variable profile in order to provide, with dressable tools, individually different tool profile geometries.

The invention concerns a method for producing tooth flank modifications on toothings of workpieces according to the preamble of claim1as well as at least one tool for performing the method according to claim9.

In the course of electromobility, increased importance is placed on the noise behavior of gear mechanisms. The tonal characteristic of the gear noise is perceived as particularly disturbing. Tonal noises are characterized in that the frequency spectrum comprises pronounced amplitudes of individual frequencies (tones) that lie above the amplitude level of the basic noise. In gear toothings, these are in particular, but not exclusively, the frequency of the tooth engagement and its higher harmonic that determine substantially the tonality of the gear noise. With increasing rotational speed, often the tonality increases. In order to reduce the gear noise, flank modifications that are of great importance for the running behavior are carried out at the toothings of the gear wheels. Usually, the modifications are identically provided tooth by tooth. By a variable flank modification tooth by tooth, a significant improvement of the running behavior and thus also of the noise behavior is observed because in particular the tonality, produced by an identical excitation of tooth engagement to tooth engagement, is reduced.

In order to provide such flank modifications at the teeth, usually the discontinuous profile grinding is employed. For this purpose, the position of the tool in regard to the engagement conditions at the workpiece is somewhat changed space by space. Such methods are however very complex and only little suitable for a highly productive manufacture.

For highly productive manufacturing methods, continuously rolling manufacturing methods are employed. However, only the same flank modification can always be provided by them at the teeth of the workpiece. However, the tonality and thus the noise behavior can be reduced only minimally in this way.

The invention has the object to design the method of the aforementioned kind and the tools in such a way that in an inexpensive and in a highly productive manner the noise development of a gear mechanism can be significantly reduced.

This object is solved for the method of the aforementioned kind in accordance with the invention with the characterizing features of claim1and for the tools in accordance with the invention with the features of claim9.

With the method according to the invention, different tooth flank modifications at the workpiece can be produced tooth by tooth by a continuously rolling manufacturing method. For this purpose, the employed tool is provided with individually different tool profile geometries. In case of dressable tools, this geometry is introduced by a corresponding dresser with variable profile. During the rolling process, the different tooth flank modifications are produced at the teeth of the workpiece tooth by tooth with these different tool profile geometries. Depending on the configuration of the gear, the tool profile geometries at the tool are designed such that the tooth flank modifications at the workpiece formed by them lead to only a minimal noise development and in particular tonality of the gear. Due to the continuously rolling manufacturing manner the workpieces can be provided inexpensively and at high productivity.

For the continuously rolling manufacturing methods, the conventional known methods are conceivable, for example, a continuous generation grinding, continuous profile grinding, gear hobbing, gear honing, gear shaving, power skiving, gear shaping and the like. With these methods, the fine machining is possible in the soft as well as hardened workpiece material state.

Advantageously, a divider equality of number of teeth of the workpiece and number of teeth of the tool is realized.

As tools, worm-type embodied tools can be employed. They are used, for example, for continuous generation grinding, continuous profile grinding, gear hobbing and the like.

The worm-type tool can be provided with at least two threads that are differently profiled. In this manner, it is achieved that the individual tool profile geometries are periodically imprinted thread by thread on the workpiece to be machined.

The number of threads of the worm-type tool can be designed depending on the gear configuration and/or the workpiece to be machined. When the worm-type tool, for example, has three differently profiled threads, then the teeth of the workpiece are provided periodically with the corresponding tooth flank modifications. In case of three threads with different profiling, the formation of the tooth flank modifications is therefore repeated at the workpiece after three teeth, respectively.

In another advantageous embodiment, the worm-type tool is designed such that it comprises at least only one thread that along its length comprises differently profiled thread regions. These thread regions are then provided such that sequential teeth of the workpiece can be machined by them. In this case and also taking into account a targeted influence of the machining kinematics, it is not required that an integer divider is realized between the number of teeth of the workpiece and the number of threads of the tool.

The thread comprises at least two differently profiled thread regions so that at the workpiece two different tooth flank modifications can be provided. The different profiled thread regions are advantageously provided within the thread such that sequential teeth of the workpiece are provided with the respective tooth flank modification. Due to the continuously rolling manufacturing method, in the individual thread of the worm-type tool the corresponding thread regions are therefore arranged one behind the other so as to repeat at a distance. For imprinting different modifications, possibly a relative movement of the workpiece, e.g., by shifting (diagonal grinding) or a relative movement of the tool, e.g., by releasing the coupling of rolling is required.

The method is designed such that the workpiece that is installed later on in the gear can be machined directly with the tool. As tool, also a correspondingly geometrically modified dressing tool, e.g., multi-fluted profile rolls, can be employed with which the actual machining tool can be machined with respect to variable geometries. With the dressing tool, the different tooth flank modifications at the machining tool can be produced in a simple manner.

It is also possible to employ as machining tools gear wheel-type tools whose teeth are provided with different tooth geometries. They are employed, for example, for gear honing, gear shaping, power skiving, and the like. These different tooth geometries are periodically imprinted during the continuous rolling manufacturing method at the tooth flanks of the workpiece. The gear wheel-type tool has at least two different tooth geometries that advantageously are repeated irregularly about the circumference of the gear wheel-type tool.

The tool according to the invention for performing the method is characterized in that is comprises individual tool profile geometries. Depending on the number of these different tool profile geometries, at the workpiece corresponding tooth flank modifications can be provided. The tool has at least two individual tool profile geometries so that the workpiece to be machined can be provided with two different tooth flank modifications.

In an advantageous embodiment, the tool is embodied of a worm-type configuration. It can have in this context two threads that are differently profiled. With such a tool, the desired tooth flank modifications can be produced periodically at the workpiece.

In another advantageous embodiment, the tool is also of a worm-type configuration but provided with only one thread. In this case, the thread comprises along its length differently profiled thread regions. They are provided one after another at such a distance along the thread that the tooth flanks of sequential teeth of the workpiece can be modified with these thread regions.

Also, it is possible to design the tool like a gear wheel. In this case, the teeth are provided with an individual tooth geometry. This tool has then at least two individually different tooth geometries so that at the teeth of the workpiece at least two different tooth flank modifications can be provided. In this context, an integer divider ratio of the number of teeth of tool and workpiece is used.

The gear wheel-type tool can comprise an outer toothing or an inner toothing.

The tool can also be a dresser with variable profile in order to provide individually different tool profile geometries in case of dressable tools.

The subject matter of the application results not only from the subject matter of the individual claims but also from all specifications and features disclosed in the drawings and the description. They are considered important to the invention, even if they are not subject matter of the claims, inasmuch as, individually or in combination, they are novel in relation to the prior art.

Further features of the invention result from the additional claims, the description, and the drawings.

With the method disclosed in the following, individual teeth or threads of a tool are configured individually differently. For divider equality to the workpiece to be machined, these individual tooth geometries or thread geometries are applied onto the workpiece in a continuous method.

In case of no divider equality, in particular for worm-based tools, a variable tool geometry generation is realized not only per thread but also along the thread. Due to the coupling of the variable geometries thread by thread as well as along a thread with a corresponding feed kinematics, a flank-individual geometry is imprinted on the teeth of the workpiece.

InFIG. 1, typical tooth flank modifications are illustrated. The method can be used, of course, also for non-typical modifications.

FIG. 1ashows a profile angle modification fHαat a tooth. The profile angle modification is illustrated by the thick solid lines. The illustrated tooth1has the two tooth flanks2,3. With dashed lines, the unmachined tooth flanks are illustrated. In the embodiment, the tooth flank3has been machined by a corresponding tool such that this tooth flank comprises the profile angle modification that is indicated by the thick lines.

FIG. 1bshows as a tooth flank modification a tip relief caof the tooth flank3. The tip relief is again illustrated by thick solid lines. The tip relief cabegins at dcaand extends to the addendum circle. The material removal for obtaining the tip relief thus increases, in an end face section, beginning at dcaall the way to the addendum circle.

InFIG. 1c, a profile crowning cαprovided at the tooth flank3is illustrated. The profile crowning is provided across the height from the root4to the top land5as well as well as across the entire width of the tooth1.

The tooth flank modification according toFIG. 1dis a twist cVβ. It is again illustrated by bold solid lines and provided at the tooth flank3of the tooth1in the embodiment. The twist cVβextends across the height and the width of the tooth flank3. The twist is designed such that the width of the top land5is smaller at the end face6of the tooth1than at the oppositely positioned end face7. The root width of the tooth1in the region of the end face6is larger than in the region of the oppositely positioned end face7. The configuration of the twist can also be carried out precisely in opposite direction in relation to the end faces.

A further typical tooth flank modification is illustrated inFIG. 1e. This is a flank line angle modification fHβ. It is provided at the tooth flank3of the tooth1and extends across the height of the tooth1as well as across its width. The solid lines show the flank line angle modification fHβ. Such a modification is produced by a linear relief of the material of the tooth1across its width. Accordingly, the end face7of the tooth1is wider across its height than the oppositely positioned end face6.

The end relief be, leinFIG. 1fis a further typical tooth flank modification. The end relief is provided, for example, at the tooth flank3of the tooth1. The end relief be, leresults in that material is removed from the tooth1across a certain tooth width in the region of its two end faces6,7across the tooth height. The two end reliefs at the tooth flank3are illustrated by solid lines.

In the production of the width crowning cβ(FIG. 1g), material is removed symmetrically in the direction toward the two end faces6,7of the tooth1. The width crowning cβis therefore designed such that the flank lines extending across the width extend in a circular arc shape.

Finally, the root relief cfis illustrated inFIG. 1has a further typical tooth flank modification. It is provided across the width of the tooth flank3in the root region and extends only across a portion of the height of the tooth flank3.

The tooth flank modifications illustrated with the aid ofFIGS. 1ato 1hcan be provided symmetrically or non-symmetrically and in different superpositions and sizes at both tooth flanks2,3.

FIG. 2shows in an exemplary fashion three teeth1of a spur-toothed gear wheel. All teeth1of this gear wheel are provided in an exemplary fashion with a width crowning cβat their tooth flank3. All teeth1of this gear wheel are of the same configuration, i.e., they have each the same tooth flank modification.

FIG. 3shows a portion of a gear wheel that is produced according to the method of the invention. With this method, it is possible to provide the tooth flanks3of the teeth1with different tooth flank modifications. For example, it is illustrated that the tooth1is provided with a width crowning cβat its tooth flank3, the tooth1′ with a profile angle modification fHαat the tooth flank3, and the tooth1′ with a profile crowning cαat the tooth flank3.

The tooth flank modifications at the teeth of the gear wheel illustrated inFIG. 3are to be understood only as examples. With the method, it is possible to vary in a targeted fashion at a gear wheel the teeth with respect to their tooth flank modifications.

With this method, it is possible to satisfy the increasing requirements in regard to the noise behavior of gear wheels in particular in the field of electromobility. Since in the field of electromobility no noise-emitting combustion engines are present anymore, the noise behavior of the gear wheels or of the gear mechanism plays an important role. The tonality of the tooth engagement in the gears comes to the fore in electromobility. The tonality is broken due to the tooth-by-tooth variable geometries. These variable geometries can be produced by means of a continuously working method so that a high productivity is achieved.

The method can be a machining method or a dressing method.

The teeth can be components of gear wheels but also of dressing tools and machining tools for producing such gear wheels.

With the aid ofFIG. 4, it will be explained where the method is employed. The gear cutting methods can be divided into discontinuously as well as continuously dividing gear cutting methods. Relevant are the continuously dividing gear cutting methods. For this, worm-type tools can be employed, for example, for generation grinding, for profile grinding or for (finish/skiving) gear hobbing.

Alternatively, gear wheel-type tools can be employed. They are used, for example, in gear honing, gear shaving, (hard) power skiving or (hard) gear shaping.

With the aid ofFIG. 5, machining of a workpiece9by a worm-type tool10or11will be explained. The gear ratio between the tool10/11and the workpiece9is an integer.

The workpiece9has the number of teeth z2which amounts to 12 in the embodiment.

The tool10/11has the number of threads z0wherein in the embodiment three threads are individually profiled. These differently profiled threads are identified inFIG. 5by z0.1, z0.2, and z0.3. The further threads of the tool10/11are embodied in a repetition in accordance with the threads z0.1to z0.3.

The number of teeth z2of the workpiece9results thus from the equation

Thus, the equation

applies in the illustrated embodiment.

The tool10is a grinding tool that is embodied of a worm-type configuration and advantageously is dressable.

The tool10is in engagement with the workpiece9during machining. The workpiece9in the form of a spur gear rotates at the rotational speed n2about its axis13which, in the usual manner, is positioned at an angle to the axis of rotation12of the workpiece9.

The rotation of workpiece9and workpiece10is coupled kinematically in a known manner, wherein in addition the tool10is moved by a feed amount aeaxially (axial feed fa) as well as advantageously tangentially in relation to the workpiece9in advancing direction. By means of the three individually profiled threads z0.1to z0.3of the tool10, the corresponding tooth flanks of the workpiece9are profiled. Since the tool10comprises three differently profiled threads, corresponding differently modified tooth flanks can be produced at the teeth Z1to Z12by generation grinding.

As can be seen inFIG. 5, the tooth Z1has, for example, the tooth flank modification which is determined by the thread z0.1of the tool10. The teeth Z2and Z3have the tooth flank modifications which are determined by the threads z0.2and z0.3of the tool10. Subsequently, the tooth flank modifications are repeated at the teeth Z4to Z6, Z7to Z9, and Z10to Z12.

When a gear hobbing tool that is of a worm-type configuration is used as a tool11, in principle the same sequences as for use of the generation grinding cylinder10result. The workpiece9and the tool11are rotated about their respective axes12,13at the rotational speeds n2and n0. In a known manner, the two axes of rotation12,13are positioned at an angle relative to each other. The rotation of workpiece9and tool11is coupled again kinematically so that the desired profile can be produced at the workpiece9by the tool11.

The tool11in the form of the gear hobbing tool has, for example, three individually profiled threads z0.1to z0.3. Correspondingly, teeth comprising individually profiled tooth flanks, respectively, are produced at the workpiece9upon machining, as has been explained with the aid of the generation grinding method.

The two methods explained in an exemplary fashion by means of worm-type tool10,11enable in a continuously working method the production of variable topographies tooth by tooth at the workpiece9. In deviation from the embodiment, the tool10,11can also be provided with only two individually profiled threads but also more than three individually profiled threads so that at the workpiece9a corresponding number of teeth with individually designed tooth flank modifications can be produced.

FIG. 6shows two embodiments in which the tooth flank modifications at the workpiece9are produced by a gear wheel-type tool14,15.

The tools14,15have the tooth number z0with an individual tooth geometry. The correlation of the respective tool14,15to the workpiece9is realized in the same manner as in the embodiments according toFIG. 5. Between the tool14,15and the workpiece9, an integer gear ratio is provided.

The workpiece14is a cylindrical honing stone with inner toothing. In workpiece machining, the tool14is rotated about the axis13and the workpiece9about the axis12at the rotational speeds n0and n2. The two axes of rotation12,13are positioned at an axis crossing angle Σ relative to each other. The rotational speeds n0and n2are matched to each other in a known manner.

The workpiece9is displaced during machining at an oscillation speed voscin the direction of its axis12as well as perpendicularly thereto in accordance with the feed aein the direction toward the tool14. The gear honing is generally known and is therefore not explained here in more detail. The process applies in the same manner to workpieces with inner toothing as well as workpieces with outer toothing.

The workpiece9has the number of teeth z2, wherein the correlation with the number of teeth z0of the tool14according to the equation z0=i·z2applies, wherein i=1, 2, 3, . . . . This applies to a workpieces with outer toothing as illustrated in the embodiment.

When the workpiece has an inner toothing, then for the correlation between the number of teeth z2of the workpiece9and the number of teeth of the tool15the relation z2=i·z0applies wherein i=1, 2, 3, . . . .

The tool14comprises teeth with different profiling so that the teeth of the workpiece9in the described manner can be provided with different tooth flank modifications, depending on the configuration of the teeth z0of the tool14.

FIG. 6shows as a further embodiment the power skiving by means of the tool15. The tool15is rotated about its axis13and the workpiece about its axis12during the manufacture at the rotational speeds n0and n2. The two axes12,13are positioned at an axis crossing angle Σ relative to each other. The tool15is displaced during the machining in the direction of its axis13(axial advance fa) and at the same time radially in the direction toward the workpiece9.

The rotations of workpiece9and tool15are coupled with each other in a known manner kinematically so that the tooth profile is produced in the desired degree. Due to the individual tooth geometries of the tool15, teeth with individual flank modification can be produced at the workpiece9in a continuous method.

FIG. 7shows further examples of how workpieces with individually configured tooth flank modifications can be produced in a continuous method.

In an exemplary fashion, the employed tool16is a worm-type grinding tool with which a diagonal generation grinding can be performed. In this method, an axial advance and tangential advance occur simultaneously with the rotation of the tool16about its axis13.

The tool16has in an exemplary fashion the number of threads Z0=1. This thread along its length is provided with differently profiled thread regions, as is illustrated in an exemplary fashion. The thread region Z0.1,Refforms a reference region with which a reference tooth flank modification is produced at the tooth of the workpiece.

The thread region Z0.1is designed such that with it, in the disclosed manner, a profile angle modification fHαat the tooth flank of the workpiece tooth can be produced.

The thread region z0.1,fHα,2is designed such that with it a further different profile angle modification at the tooth flank3of the workpiece tooth can be produced.

The thread region z0.1,cαis formed such that with it at the tooth flank13of the workpiece9the profile crowning cαcan be produced.

The thread regions are positioned at such a distance one behind the other that each thread region machines the tooth flanks of different teeth of the workpiece.

InFIG. 7, it is indicated by the arrows how the workpiece removal at the tooth flanks of the workpiece is realized at the teeth of the workpiece9in relation to the thread regions producing the profile angle modification.

For diagonal generation grinding, the workpiece9and the tool16are rotated in a synchronized manner about their respective axes12,13at rotational speeds n0, n2, wherein the two axes of rotation12,13, in a known manner, are arranged at a pivot angle relative to each other.

As can be taken furthermore fromFIG. 7, the workpiece machining can also be varied in a targeted manner by a targeted pivot angle variation or a targeted coupling of rolling. In this way, the pivot angle φ of the tool16relative to the workpiece9can be changed.

For the coupling of rolling solution, it can be provided that the ratio of rotational speed n0of the tool16to the rotational speed n2of the workpiece9is not constant.

The pivot angle variation and the coupling of rolling variation are simply further examples as to how in a targeted fashion workpiece tooth flank modifications in a continuously rolling manufacturing method can be advantageously produced by affecting the method kinematics.

In the embodiment according toFIG. 7, the gear ratio between the worm-type tool16and the workpiece9can be integer or non-integer.

As shown with the aid of the examples ofFIGS. 5 to 7, different flank modifications can be provided on toothings by a continuously rolling manufacturing method. When worm-type tools are employed (FIGS. 5 and 7), then dressable tools can be employed, wherein individual threads of the worm-type tools10,11,16can be individually dressed for producing variable tooth geometries in the individual threads. In the embodiment according toFIG. 5, three threads are provided at the worm-type tool10,11which are each individually profiled (standard kinematics).

FIG. 7shows in an exemplary fashion that along one thread of the worm-type tool16variable tool geometries along this thread can be dressed (diagonal kinematics).

When non-dressable tools are used for the worm-type tools10,11,16, then the variable tool geometries along a thread are ground in different thread regions, as explained in an exemplary fashion with the aid ofFIG. 7.

When realizing integer dividers between the number of teeth z2of the workpiece and the number of teeth z0of the tool, the same teeth of the workpiece9will always come into contact with the same thread of the tool10,11.

The result is that different thread geometries are imprinted onto the toothing of the workpiece9as variable geometries.

The use of the worm-type tool is in particular provided for finish gear hobbing, for generation grinding or for skiving gear hobbing.

When gear wheel-type tools are used as tools (FIG. 6), then the variable flank modifications at the toothings are produced also with continuously rolling manufacturing methods. In this context, dressable tools14,15can be employed. For this dressing process, a dressing wheel with variable modifications can be used. In this method, an integer divider between the number of teeth z2of the workpiece9and the number of teeth z0of the tool is also realized. In this way, it is achieved that always the same teeth of the workpiece9come into contact with the same teeth of the tool14.

In this way, the different dresser tooth geometries are imprinted onto the toothing as variable geometries by the tools14,15. In an exemplary fashion, the gear honing process is explained for this purpose.

With the aid ofFIG. 6, also the power skiving has been explained. When the tool15is not dressable, then the individual teeth of the tool15are ground individually with the desired correction.

For this purpose, an integer divider between the number of teeth z2of the workpiece9and the number of teeth z0of the tool15is also realized so that always the same teeth of the workpiece9will come into contact with the same teeth of the tool15.

Aside from skiving, for this purpose also shaving or in an exemplary fashion shaping are conceivable.

Due to the described divider equality of numbers of teeth of the workpiece and number of threads or number of teeth of the tool, in the described manner individual tool profile geometries are periodically imparted thread by thread or tooth by tooth onto the workpiece.

When during machining a targeted tool movement during the machining process is additionally performed, as explained in an exemplary fashion with the aid ofFIGS. 5 to 7, individual geometries can be reinforced tooth by tooth at the workpiece9.

In addition, or in place of the targeted supplemental tool movement, a variable geometry along a thread or periodically engaging tool teeth can also be used as well as the manufacturing kinematics can be expanded as described in order to reinforce an individual geometry on the workpiece tooth by tooth. In this way, elimination of the divider equality of number of teeth of the tool or number of threads of the tool and number of teeth of the workpiece is possible.

With the described method, machining methods and dressing methods can be performed. For this purpose, the described machining tools10,11,14to16as well as corresponding dressing tools are employed.