Tool and Method for Creating Back Tapers at the Teeth of a Toothing of a Gear

Abstract

The present invention relates to a tool and a method for creating back tapers at an internal or external toothing of a gear. The tool rotates during use about a tool axis of rotation includes a tool shaft extending along the tool axis of rotation, a fastening section for fastening the tool to a tool drive of a machine tool, the fastening section formed at an end of the tool shaft, and at least one cutting blade, which is arranged at a fastening position provided at the circumference of the tool shaft. The tool according to the invention and the method according to the invention enable with simple means the creation of geometrically precisely shaped back tapers at toothings without the need for the use of specially shaped cutting inserts or a change of machine tools proven in practice for the creation of back tapers. This is achieved according to the invention in that the diameter of the tool shaft measured in a plane oriented normal to the tool axis of rotation increases starting from the diameter, which the tool shaft has at the fastening position of the cutting blade, in a direction directed towards the fastening section.

Claims

1. A tool for creating back tapers at an internal or external toothing of a gear, wherein the tool rotating during use about a tool axis of rotation comprises a tool shaft extending along the tool axis of rotation, a fastening section for fastening the tool to a tool drive of a machine tool, the fastening section formed at an end of the tool shaft, and at least one cutting blade, which is arranged at a fastening position provided at the circumference of the tool shaft, wherein the diameter of the tool shaft measured in a plane oriented normal to the tool axis of rotation increases starting from the diameter, which the tool shaft has at the fastening position of the cutting blade, in a direction directed towards the fastening section.

2. The tool according to claim 1 wherein the distance of the fastening position of the cutting blade to the front side of the tool shaft that is free during use is smaller than the distance of the fastening position to the end of the tool shaft adjoining the fastening section.

3. The tool according to claim 2, wherein the fastening position of the cutting blade directly adjoins the front side of the tool shaft that is free during use.

4. The tool according to claim 2, wherein two fastening positions each for a cutting blade are provided at the circumference of the tool shaft and in that of these two fastening positions, the first fastening position is arranged according to claim 2, while the second fastening position is arranged spaced apart from the first fastening position in a longitudinal direction of the tool shaft in a direction towards the fastening section.

5. The tool according to claim 4, wherein the second fastening position directly adjoins the end of the tool shaft assigned to the fastening section.

6. The tool according to claim 1, wherein the respective fastening position is formed by a recess and the cutting blade arranged in the respective fastening position is designed as a cutting insert, which is held in the recess with a holding section, while a cutting blade of the cutting insert projects in a radial direction beyond the circumference of the tool shaft.

7. The tool according to claim 1, wherein the diameter of the tool shaft continuously increases starting from the fastening position of the cutting blade in a direction towards the end of the tool shaft assigned to the fastening section.

8. The tool according to claim 7, wherein the diameter of the tool shaft continuously increases starting from the front side of the tool shaft that is free during use in a direction towards the end of the tool shaft assigned to the fastening section.

9. The tool according to claim 7, wherein the tool shaft is shaped at least in sections in the manner of a cone or a truncated cone.

10. The tool according to claim 1, wherein the tool shaft is manufactured as a massive body.

11. A method for creating back tapers at the teeth of a toothing of a gear, in which material is removed by chip removal from the flanks of the teeth of the gear rotating about a workpiece axis of rotation by means of at least one cutting blade fastened at the circumference of a tool shaft of a tool rotating about a tool axis of rotation oriented along the tool shaft, wherein the tool is designed according to claim 1 and in that the tool axis of rotation is oriented with respect to the workpiece axis of rotation at an angle Σ greater than 0°.

12. The method according to claim 11, wherein the angle Σ, at which the tool axis of rotation and the workpiece axis of rotation are arranged angularly with respect to one another, is at least equal to an angle β that a surface line, which is applied to the tool shaft and forms the enveloping of the tool shaft, encloses with the tool axis of rotation

13. The method according to claim 11, wherein the angle β is 4° to 16°.

14. The method according to claim 11, wherein the cutting blade comprises a cutting edge designed straight-lined at least in sections, which is oriented parallel to the surface line, which creates the enveloping of the tool shaft, and in that the angle Σ is set such that the straight-lined section of the cutting edge, at the moment of contact with the tooth to be machined in each case, is oriented parallel to the head surface of the respective tooth of the gear.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention is explained in more detail in the following with reference to a drawing representing an exemplary embodiment. The schematic drawings show:

[0033] FIG. 1 a tool when creating back tapers at the teeth of an externally toothed gear in a lateral view;

[0034] FIG. 2 the tool according to FIG. 1 in a frontal view;

[0035] FIG. 3 the tool according to FIGS. 1 and 2 in a perspective view from behind;

[0036] FIG. 4 an alternative design of a tool for creating back tapers in a lateral view.

DESCRIPTION OF THE INVENTION

[0037] The tool 1 for creating back tapers H at the external toothing A of a gear ZR rotates about a tool axis of rotation W during use.

[0038] In this case, the tool 1 comprises a tool shaft 4 extending along the tool axis of rotation W, on an end 5 of which a conventionally designed fastening section 6 for fastening the tool 1 to a clamping of a tool drive, not shown here for the sake of clarity, of a machine tool, also not shown, is formed. The tool shaft 4 and the fastening section 5 are made massively from a piece from a tool steel proven in the prior art for the manufacture of tools of the type in question here.

[0039] At its end opposite to the fastening section 6 and protruding freely from the clamping of the tool drive during use, the tool shaft 4 comprises a front side 7, which has a circular basic shape with a diameter D1. Starting from the front side 7, the diameter D of the tool shaft 4 increases continuously in the direction of the longitudinal direction L of the tool shaft 4 extending parallel to the tool axis of rotation W until the end 5 of the tool shaft 4 assigned to the fastening section 6 is reached at which the diameter D has its greatest value D2.

[0040] In this way, the tool shaft 4 has the shape of a truncated cone, the circumferential surface 8 of which is represented by rotation of a straight surface line M about the tool axis of rotation W and thus proceeds from its thickest point adjoining the fastening section 6 conically in the direction of the front side 7 of the tool shaft 4 that is free during use.

[0041] The surface line M is thereby inclined relative to the tool axis of rotation W by an angle β of 5°, for example.

[0042] Starting from the front side 7, a recess 9 opened laterally towards the circumferential surface 8 is formed into the tool shaft 4, in which recess 9 a conventionally designed cutting blade insert 10 sits with its holding section. The holding section of the cutting blade insert 10 carries a cutting blade 11, which protrudes freely in the radial direction R beyond the circumferential surface 8 of the tool shaft 4. In this way, the cutting blade 11 is held at a fastening position B1 which directly adjoins the front side 7 of the tool shaft 4 that is free during use and thus has the greatest possible distance S to the end 5 of the tool shaft 4 adjoining the fastening section 7. The cutting blade 11 comprises a straight-lined cutting edge 12, which in the example described here extends parallel to the circumferential surface 8 of the tool shaft 4.

[0043] In use, the gear ZR rotates synchronously with the tool 1 about a tool axis of rotation W. The rotational speed ratio R1/R2 of the rotational speed R1 at which the tool 1 rotates about the tool axis of rotation W to the rotational speed R2 at which the workpiece (gear ZR) rotates about its workpiece axis of rotation X is selected such that both rotational speeds R1, R2 do not have a common divisor. In this manner, it is achieved in a known manner that all teeth Z of the gear ZR are evenly machined after a sufficient number of circulations.

[0044] In order to create the back tapers H at the teeth Z of the external toothing A of the gear ZR, the tool 1 with its tool axis of rotation W is positioned relative to a workpiece axis of rotation X such that, between the workpiece axis of rotation X and the tool axis of rotation W, an axis-crossing angle Σ is enclosed, which is, for example, the same as the angle β about which the surface line M representing the circumferential surface 8 of the conical tool shaft 4 is oriented with respect to the tool axis of rotation W.

[0045] In this way, the circumferential surface 8 of the tool shaft 4 is oriented at the point of its greatest approach to the workpiece axis of rotation X parallel to the workpiece axis of rotation X. As a result, the cutting edge 12 of the cutting blade 11, at the moment of engagement in the respective tooth Z to be machined, is also oriented parallel to its head surface K and thus parallel to the workpiece axis of rotation X.

[0046] In this way, despite the conicity of the tool shaft 4 and the cutting edge 12 of the cutting blade 11 oriented parallel to the circumferential surface 8 of the tool shaft 4, a cutting pattern is created during the chip-removing creation of the back tapers H on the teeth Z of the gear ZR performed by the cutting blade 11, which cutting pattern corresponds to that which results when back tapers are introduced into the teeth of a gear with a slim tool of the type mentioned at the outset and described in EP 0 550 877 B1, but which is susceptible to deformation.

[0047] In contrast to the prior art, in which slim tools have to be used in order to reach the place where the respective back taper is to be created, in the tool 1 according to the invention the risk of a bending deformation along its tool axis of rotation W is minimized in that the tool shaft 4, due to its increasing thickness starting from the fastening position B1 in the direction towards the fastening section 6, offers a high resistance to deformation to the forces that occur during the engagement of the cutting blade 11 into the material of the teeth Z of the gear ZR and are oriented transversely to the tool axis of rotation W.

[0048] As a result, high-precision production of the back tapers H at the gear ZR is also enabled if the fastening position B1 for the cutting blade 11 is selected to protrude widely freely with respect to the fastening section 6 with which the tool 1 is held in the tool recess of the respective machine tool during use.

[0049] If back tapers H at the gear ZR are not only to be created at the end sections of the teeth Z with the tool 1, which end sections are assigned to the one front side S1 of the gear ZR, but also at the end sections adjoining the opposite front side S2, then for this purpose, in FIG. 1, the tool 1 can be turned about a vertical axis V as soon as the creation of the back tapers H adjoining the first front side S1 is completed, and a further machining run can be performed with the tool 1.

[0050] FIG. 2 shows an example of a tool 101 that enables the simultaneous creation of back tapers H1, H2 at the front sided S1, S2 of the gear ZR to be machined.

[0051] For this purpose, the tool 101 has a tool shaft 104 and a fastening section 106, which are shaped in one piece as a massive body in the manner described above for the tool 1.

[0052] As with the tool 1, a recess is also formed into the tool 101 in its front side 107 that is free during use, which recess, like the recess 9 of the tool 1, is open in the radial direction R to the circumferential surface 108 of the tool 101. A conventionally shaped first cutting blade insert 110 sits in the recess. The cutting blade 111 of the cutting blade insert 110 is located in the tool 101 at the same fastening position B1 as the cutting blade 11 in the tool 1. Here too, the cutting edge of the cutting blade 111 is oriented parallel to the axis of rotation W of the tool 101.

[0053] Additionally, a second cutting blade 113 is provided with the tool 101. For this purpose, at a fastening position B2, which is provided approximately in the middle of the longitudinal extension of the tool shaft 104, a recess is formed into the circumferential surface 108 of the tool 101 in which recess a cutting blade insert 114 sits. Like the cutting blade inserts 10 and 110, the cutting blade insert 114 carries the second cutting blade 113 projecting in the radial direction R beyond the circumferential surface 108 of the conically shaped tool shaft 104.

[0054] For machining the gear ZR, the tool 101, like the tool 1, is oriented with its axis of rotation W with respect to the axis of rotation X of the gear ZR rotating synchronously with the tool 101 under the axis-crossing angle Σ and positioned such that the cutting blades 110 and 113 engage with the respective tooth Z to be machined. Here too, the conical shape of the tool shaft 104, which increases in thickness starting from the front side 107 that is free during use, ensures that no deformations of the tool 101 occur during machining, despite the transverse loads of the tool 101 occurring thereby, which deformations could impair the precision of the machining result.

REFERENCE NUMERALS

[0055] 1 Tool for creating the back tapers H [0056] 4 Tool shaft [0057] 5 End of the tool shaft 4 assigned to the fastening section 6 [0058] 6 Fastening section [0059] 7 Front side 7 of the tool shaft 4 that is free during use [0060] 8 Circumferential surface of the tool shaft 4 [0061] 9 Recess [0062] 10 Cutting blade insert [0063] 11 Cutting blade of the cutting blade insert 10 [0064] 12 Cutting edge of the cutting blade 11 [0065] 101 Tool for simultaneous creation of back tapers H1, H2 [0066] 104 Tool shaft [0067] 105 End of the tool shaft 104 assigned to the fastening section 106 [0068] 106 Fastening section [0069] 107 Front side of the tool shaft 104 that is free during use [0070] 108 Circumferential surface of the tool 101 [0071] 110 Cutting blade insert [0072] 111 Cutting blade of the cutting blade insert 110 [0073] 113 Second cutting blade [0074] 114 Second cutting blade insert [0075] β Inclination angle of the surface line M relative to the tool axis of rotation W [0076] Σ Axis-crossing angle [0077] A External toothing of the gear ZR [0078] B1 Fastening position of the cutting blade 11 (FIGS. 1 to 3) and the cutting blade 111 (FIG. 4) [0079] B2 Fastening position of the second cutting blade 113 (FIG. 4) [0080] D Diameter of the tool shaft 4 [0081] D1 Diameter of the tool shaft 4 at its front side 7 [0082] D2 Diameter of the tool shaft 4 at its end 5 [0083] H Back taper [0084] H1, H2 Back tapers [0085] K Respective head surface of the teeth Z [0086] L Longitudinal direction [0087] M Surface line creating the circumferential surface 8 [0088] R Radial direction [0089] S Distance [0090] S1, S2 Front sides of the gear ZR to be machined [0091] W Tool axis of rotation [0092] X Workpiece axis of rotation [0093] z Teeth of the gear ZR [0094] ZR Gear