Method for gear shaping of a toothing, control program and gear shaping machine for carrying out the method

Abstract

The invention relates to a method for gear shaping a tooth portion (55) on a workpiece (50) with a specified normal pitch (m n ), an action angle (a) and optionally a helix angle (b), wherein a gear shaping tool (40) moved in a stroke cycle with a specified stroke length (h) removes material from the workpiece in a plurality of working strokes in a rolling machining engagement, thereby forming a contact locus, wherein at least in a first plurality of strokes the contact locus on an arc of a circle at the center of the stroke forms an angle (g) with a tooth side line (57), the cotangent of which is smaller than or equal to the product of a constant 40, preferably 33, in particular 25, and a geometric / technological factor.

Description

[0001] The present invention relates to a method for gear forming of teeth on a workpiece, wherein a gear shaper cutter moving in a stroke cycle with a specified stroke length removes material from the workpiece in multiple working strokes during rolling engagement, thereby forming a contact trajectory.

[0002] This gear forming technique is a method for manufacturing gear teeth, which has been well-known for a long time. It is a cutting method in which the main cutting motion is achieved through the stroke of the tool, with material removal of the workpiece occurring during the so-called working stroke, and the return stroke occurring in a raised state to avoid return stroke streaks. The principle of this method is described, for example, in Thomas Bausch et al., "Innovative Zahnradfertigung [Innovative gear production]", 3rd edition, page 281, figure C1-1.

[0003] One important advantage of gear forming over other methods (such as gear hobbing) is that gear forming is versatile, especially for workpieces with internal teeth or shoulders that connect to the teeth, while gear hobbing is not well-suited or not suitable at all for such workpieces.

[0004] In addition to conventional feed, decreasing helical feed is now used. However, regardless of the feed strategy, it can be observed that, especially with higher stroke numbers, and particularly in the tooth section with smaller helix angles up to the spur section, and under generally high cutting forces, higher tool loads occur, which also increases the risk of damage.

[0005] In view of this observation, the object of the present invention is to further develop a gear forming method of the type mentioned at the beginning to achieve a satisfactory combination of rapid machining and engineering safety, while having the least possible tool wear.

[0006] In terms of method, this objective is achieved by the present invention through the development of a method of the type mentioned at the beginning, the basic feature of which is that, at least in the first plurality of strokes, the contact trajectory on the partial circle at the center of the stroke forms an angle γ with the tooth flank, the cotangent of which is less than or equal to the product of constants K1 and K2, wherein K1 is equal to 40°, preferably 33°, particularly 25°, and K2 is a geometry / process factor (second factor) K2 = K h ·K m ·K α ·K β K h =h[mm] / 20, K m =3 / m n [mm],K α=sin 20° / sinα, and K β =cosβ. Here, m n α is the normal tooth pitch, β is the action angle, and β is the optional helix angle of the workpiece tooth (β = 0 in the case of spur teeth), and h is the stroke length.

[0007] It has been found, for example, that this chip formation in conventionally known gear forming leads to chip compression, and in addition, the cutting edge of the gear shaper is subjected to stress at various points in a concentrated manner, thus increasing the wear of the gear shaper, and these effects are related to the orientation of the contact trajectory.

[0008] According to the invention, it is now proposed that, compared with the prior art, the contact trajectories extend over a larger area in the vertical direction of the teeth of the forming tooth, thereby mitigating the effects described above. These contact trajectories are generally parallel to each other and are distributed substantially uniformly on the tooth flanks; wherein the stroke motion is generally achieved via crank drive. However, the speed profile is not constant over the stroke, therefore, with respect to the definition used in the characterizing portion of claim 1, reference is made to the stroke center and the partial circle. Furthermore, it has been found that advantageous designs do not rely on fixed angles independent of the workpiece and process, but rather on advantageous adjustments when the angle conditions according to the invention also depend on the geometry of the process and the workpiece, as represented by the second factor K2 in the characterizing feature of claim 1. However, in conventional methods, the contact trajectories on the workpiece tooth flanks are almost parallel to the tooth flank lines, and even with decreasing radial feed, a cotangent γ value typically 70 or higher can be obtained with a parameter combination (constellation) of K2 = 1.

[0009] K1 can be preferably 20.5, but it can also be only 19.7, or even only 19.4.

[0010] In another preferred embodiment, it is proposed that the gear shaper is fed via a first plurality of strokes, particularly in the form of a constant helical feed, and the feed parameter, defined by the quotient of the radial feed per workpiece rotation divided by the lift of the gear shaper between the working stroke and the return stroke in the first plurality of strokes, is less than 1.4. This is a significantly lower value compared to the prior art; the trend in material surface removal is toward a flatter but broader material removal direction. The combination of the contact trajectory adjustment according to the invention and the relatively early attainment of the overall tooth flank height achieves chip formation and absorption of machining forces that are particularly favorable to the tool. Furthermore, a collision-free return stroke can still be implemented with high process reliability despite the change in contact trajectory position. In this regard, it is also proposed that the feed parameter can be less than 1.3, preferably less than 1.2, particularly less than 1.1, or even 1.0.

[0011] In another preferred configuration, it is proposed that the first and second multiple strokes occur in a feed zone where the majority of the total feed is used to complete the forming of the teeth, and that in a subsequent feed zone, the cocutting γ is greater than 40·K², particularly greater than 60·K². This facilitates a smoother transition to the higher values ​​for the later stages of machining, as described below.

[0012] Therefore, another preferred configuration is provided, wherein during the final feed to the forming tooth, when the final feed depth is reached, the cocutting γ is greater than 80·K2, and particularly greater than 120·K2. This allows for higher machining accuracy near the end of the forming process. In other words, the forming process can be divided into several regions with approximately two or three different kinematic characteristics, with an increasing trend from high machining speed to high machining accuracy.

[0013] The embodiments of the invention are most effective for straight teeth or teeth with a relatively low helix angle. The method is particularly suitable for helix angles less than 14°, more preferably less than 12°, and especially less than 10°.

[0014] Furthermore, it is preferred that the tooth width is at least 60%, preferably at least 70%, and particularly at least 80% of the stroke length (or conversely, the stroke length is adapted to the tooth width within these ratio limits). This enables an advantageous overall configuration in terms of the advantageous utilization of the stroke length used for machining, wherein, in order to achieve satisfactory cutting speeds, it is preferably proposed that this ratio is no greater than 96%, and particularly no greater than 92%.

[0015] In another preferred configuration, it is proposed that the rolling position changes during each machining operation within the forming gap between two successive workpiece rotations. This ensures that not every tooth clearance is repeatedly machined in the exact same rolling position. For this purpose, the number of strokes per zone should not be an exact integer, wherein values ​​less than 1.4, more preferably less than 1.2, and particularly less than 1.1 are preferred within the scope of the invention. However, values ​​less than 1, even less than 0.9, are conceivable in this regard, wherein, on the other hand, these values ​​should preferably not be less than 0.5, more preferably not less than 0.6. It should be understood that the number of strokes per workpiece rotation should also preferably not be an integer.

[0016] In another preferred embodiment, the number of strokes is at least 30 double strokes per minute, preferably at least 100 double strokes per minute, and particularly at least 200 double strokes per minute. However, even higher values, such as 300 double strokes per minute, or even 400 double strokes per minute or higher, can be used to achieve the highest possible processing speed.

[0017] The advantages of the method according to the invention are particularly significant when the width of the formed teeth is greater than 15 mm, or even when the width of the teeth is greater than or equal to 20 mm, especially 35 mm or more, or even 50 mm or more.

[0018] In another preferred embodiment, it is proposed that, at least in the first plurality of strokes, a consistent contact trajectory extends over at least 20%, preferably at least 30%, and particularly at least 40% of the full profile height of the end geometry of the forming tooth, as observed in the profile direction. This further improves chip formation and absorption of machining forces on the tool.

[0019] Furthermore, the present invention provides a control program that, when executed on a controller of a gear forming machine, controls the machine to perform the method according to any one of the preceding claims.

[0020] In terms of device technology, the present invention provides a gear forming machine with a controller equipped with the control program according to claim 12. Preferably, a gear forming machine is provided equipped with an NC controller for the motion axis of the gear forming machine, the stroke motion of which is achieved via crank drive. However, a hydraulic shaft can also be used for the stroke. Furthermore, the invention is not limited to specific details regarding the specific implementation of the machine, and it is possible to use gear forming machines familiar to those skilled in the art and commercially available; the design described in DE 102019 004 299 A1 can be used for exemplary designs of suitable gear forming machines, wherein the aforementioned document is incorporated herein by reference.

[0021] Further features, details, and advantages of the invention will become apparent from the following description with reference to the accompanying drawings, wherein...

[0022] Figure 1 A schematic diagram is shown for machining engagement during gear forming.

[0023] Figure 2 The angle between the contact trajectory on the partial circle at the center of the stroke and the tooth flank is shown, and

[0024] Figure 3 A qualitative comparison of contact trajectories with existing technologies is shown.

[0025] exist Figure 1As can be seen, the gear shaper 40 engages with the workpiece 50 to form the teeth 55 on the workpiece. The diagram shows the situation during the working stroke at the start of engagement, from which the gear shaper 40 moves downward along the stroke axis Z while simultaneously meshing with the workpiece 50. For this purpose, the rotational speeds of the gear shaper 40 and the workpiece 50 are synchronized in a known manner. In this exemplary embodiment, the stroke motion is achieved using a crank drive, as in the prior art; in this given exemplary embodiment, a stroke length of approximately 20 mm is set, wherein the number of strokes is 500 double strokes per minute (working stroke + return stroke), and the rolling speed is 0.95 strokes per section, in order to form, for example, straight teeth on the workpiece. It should be understood that the invention is not limited to a specific tooth type, such as external or internal teeth; internal teeth are also preferably formed. It should also be understood that the invention is not limited to a specific tooth width, associated stroke length, or tooth pitch size; in this exemplary embodiment, the tooth pitch (normal tooth pitch) is, for example, 3 mm, and the teeth are straight teeth. However, the present invention can also be applied to helical teeth, but the helical teeth should preferably be less than 14° or the value described above.

[0026] Regarding the design of a suitable gear forming machine, designs known from the prior art can be used, such as the design shown in DE 102019 004 299 A1, in which the lifting motion for the return stroke is achieved by a rotary driven cam with a predetermined profile. The aforementioned document is incorporated herein by reference in its exemplary design of gear forming machines.

[0027] exist Figure 2 (for the purpose of explanation or definition; of course,) Figure 2 The form of the gear shown is similar to Figure 1 (Different forms), an angle γ is drawn between the contact trajectory of the forming operation and the tooth flank line 57 on the partial circle on the tooth flank 56 (at the center of the stroke, which in this exemplary embodiment coincides with the center in the width direction relative to the tooth 55). Even in the case of conventional gear forming with helical decreasing feed, this angle is very narrow (e.g. Figure 1 As indicated by reference numeral 58, during conventional gear forming, the typical machining trajectory is almost parallel to the tooth flank. In the configuration according to the invention, this angle is relatively large, and the co-cut of this angle is relatively small; in the exemplary embodiment, for simplicity, the second factor K2 is 1, and no correction is provided, the co-cut γ reaches a value of about 20.

[0028] exist Figure 3 In the present invention, exemplary embodiments ( Figure 3 A) and existing technology ( Figure 3The difference between B) is again juxtaposed in a purely relative representation, where there is no need to observe the absolute values ​​(shown in an overly distorted manner); it can be seen that the machining path extends on the tooth flank 56 in a significantly more inclined manner, which, despite not having a lower number of strokes, results in good machining quality of the formed tooth 55 and achieves material removal with lower tool wear.

[0029] It should be understood that the present invention is not limited to the detailed features shown in the exemplary embodiments. Rather, the various features described above and the following claims, individually and in combination, may be necessary for implementing the present invention in various embodiments of these features.

Claims

1. A method for setting a tooth pitch m in the normal direction on a workpiece. n A method for gear forming of teeth using an action angle α and a helix angle β, wherein a gear shaper cutter moving in a stroke cycle with a specified stroke length h removes material from the workpiece in multiple working strokes during rolling machining engagement, thereby forming a contact trajectory. Its features are, At least in the first plurality of strokes, the contact trajectory on the partial circle at the center of the stroke forms an angle γ with the tooth flank, the cotangent of which is less than or equal to the product of constants K1 and K2. Where K1 equals 40, and K2 is the geometry / process factor K2=K h K m K α K β K h =h / 20, K m =3 / m n K α =sin20° / sin α, and K β =cos β.

2. A method for setting a specified normal tooth pitch m on a workpiece. n A method for gear forming of teeth using an action angle α and a helix angle β, wherein a gear shaper cutter moving in a stroke cycle with a specified stroke length h removes material from the workpiece in multiple working strokes during rolling machining engagement, thereby forming a contact trajectory. Its features are, At least in the first plurality of strokes, the contact trajectory on the partial circle at the center of the stroke forms an angle γ with the tooth flank, the cotangent of which is less than or equal to the product of constants K1 and K2. Where K1 equals 33, and K2 is the geometry / process factor K2=K h K m K α K β K h =h / 20, K m =3 / m n K α =sin20° / sin α, and K β =cos β.

3. A method for setting a specified normal tooth pitch m on a workpiece. n A method for gear forming of teeth using an action angle α and a helix angle β, wherein a gear shaper cutter moving in a stroke cycle with a specified stroke length h removes material from the workpiece in multiple working strokes during rolling machining engagement, thereby forming a contact trajectory. Its features are, At least in the first plurality of strokes, the contact trajectory on the partial circle at the center of the stroke forms an angle γ with the tooth flank, the cotangent of which is less than or equal to the product of constants K1 and K2. Where K1 equals 25, and K2 is the geometry / process factor K2=K h K m K α K β K h =h / 20, K m =3 / m n K α =sin20° / sin α, and K β =cos β.

4. A method for setting a tooth pitch m in the normal direction on a workpiece. n A method for gear forming of teeth using an action angle α and a helix angle β, wherein a gear shaper cutter moving in a stroke cycle with a specified stroke length h removes material from the workpiece in multiple working strokes during rolling machining engagement, thereby forming a contact trajectory. Its features are, At least in the first plurality of strokes, the contact trajectory on the partial circle at the center of the stroke forms an angle γ with the tooth flank, the cotangent of which is less than or equal to the product of constants K1 and K2. Where K1 equals 20.5, and K2 is the geometry / process factor K2=K h K m K α K β K h =h / 20, K m =3 / m n K α =sin20° / sin α, and K β =cos β.

5. A method for setting a tooth pitch m in the normal direction on a workpiece. n A method for gear forming of teeth using an action angle α and a helix angle β, wherein a gear shaper cutter moving in a stroke cycle with a specified stroke length h removes material from the workpiece in multiple working strokes during rolling machining engagement, thereby forming a contact trajectory. Its features are, At least in the first plurality of strokes, the contact trajectory on the partial circle at the center of the stroke forms an angle γ with the tooth flank, the cotangent of which is less than or equal to the product of constants K1 and K2. Where K1 equals 19.7, and K2 is the geometry / process factor K2=K h K m K α K β K h =h / 20, K m =3 / m n K α =sin20° / sin α, and K β =cos β.

6. A method for setting a tooth pitch m in the normal direction on a workpiece. n A method for gear forming of teeth using an action angle α and a helix angle β, wherein a gear shaper cutter moving in a stroke cycle with a specified stroke length h removes material from the workpiece in multiple working strokes during rolling machining engagement, thereby forming a contact trajectory. Its features are, At least in the first plurality of strokes, the contact trajectory on the partial circle at the center of the stroke forms an angle γ with the tooth flank, the cotangent of which is less than or equal to the product of constants K1 and K2. Where K1 equals 19.4, and K2 is the geometry / process factor K2=K h K m K α K β K h =h / 20, K m =3 / m n K α =sin20° / sin α, and K β =cos β.

7. The method according to any one of claims 1 to 6, wherein the gear hobbing cutter is fed via the first plurality of strokes, and the feed parameter defined by the quotient of the radial feed per workpiece rotation divided by the lift of the gear hobbing cutter between the working stroke and the return stroke in the first plurality of strokes is less than 1.

4.

8. The method according to claim 7, wherein, The gear hobbing cutter is fed in a constant helical feed manner.

9. The method according to claim 7, wherein the feed parameter is less than 1.

3.

10. The method according to any one of claims 1 to 6, wherein the first plurality of strokes are performed in a feed region where the total feed amount is mostly used to complete the forming tooth, and in a subsequent feed region, the cocutting γ is greater than 40. K2.

11. The method according to any one of claims 1 to 6, wherein the cocut γ is greater than 80° when the final feed depth is reached during the final feed of the shaped tooth. K2.

12. The method according to any one of claims 1 to 6, wherein the tooth portion of the straight tooth portion or the helix angle of said tooth portion is less than 14°.

13. The method according to any one of claims 1 to 6, wherein the tooth width is at least 60% of the stroke length.

14. The method according to any one of claims 1 to 6, wherein during each processing, the rolling position changes in the forming gap between two successive workpiece rotations.

15. The method according to any one of claims 1 to 6, wherein the number of strokes is at least 30 double strokes / minute.

16. The method according to any one of claims 1 to 6, wherein the tooth width is greater than 15 mm.

17. The method according to any one of claims 1 to 6, wherein, at least in the first plurality of strokes, a consistent contact trajectory extends over a region of at least 20% of the full profile height of the end geometry of the forming tooth, as observed in the profile direction.

18. A control program product comprising a control program that, when executed on a controller of a gear forming machine, controls the machine to perform the method according to any one of claims 1-17.

19. A gear forming machine including a controller, the controller being equipped with the control program product according to claim 18.

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