Method for Producing Twists on the Tooth Flanks of an Internally Toothed Workpiece

Abstract

The invention discloses a method for producing modifications, such as twists, on the tooth flanks of an internally-toothed workpiece by an externally-toothed tool. In order to carry out such a method also with machine tools, which have a reduced number of adjustable axes, the invention provides that the tool is dressed by arranging an internally-toothed dressing tool on the workpiece spindle of the machine tool at the position intended for the workpiece to be respectively honed and by bringing the dressing tool into engagement with the tool to be dressed. The width of the teeth of the dressing tool is smaller than the width of the tool to be dressed such that the dressing tool must be moved by a length along the workpiece longitudinal axis which corresponds to a multiple of the width of the teeth of the dressing tool. Subsequently, the fine machining of the workpiece takes place with the tool dressed in this manner. According to the invention, an axis cross angle is set for the dressing, which is maintained unchanged during the dressing. The respective tooth flank modification is then produced during dressing exclusively by movements of the dressing tool along the workpiece longitudinal axis and the workpiece transverse axis.

Claims

1. A method for producing modifications, such as twists, on the tooth flanks of an internally-toothed workpiece by an externally-toothed tool, whose teeth come into engagement with the teeth of the workpiece during a honing process, on a machine tool which comprises a workpiece spindle with a rotary drive for rotating the workpiece about a workpiece rotational axis, an actuating drive for adjusting the workpiece along a workpiece longitudinal axis aligned parallel to the workpiece rotational axis, an actuating drive for adjusting the workpiece along a workpiece transverse axis, which is aligned transverse to the workpiece longitudinal axis, a tool spindle with a rotary drive for rotating the tool about a tool rotational axis as well as a device for setting an axis cross angle, at which the rotational axes of workpiece and tool are aligned in a skewed manner to one another during the honing process, comprising the following work steps: a) dressing the tool by arranging an internally-toothed dressing tool on the workpiece spindle at the position intended for the workpiece to be respectively honed and by bringing the dressing tool into engagement with the tool to be dressed, wherein the width of the teeth of the dressing tool coming into engagement with the tool to be dressed is smaller than the width of the tool to be dressed to such an extent that the dressing tool, in order to pass over the width of the tool to be dressed, must be moved by a length along the workpiece longitudinal axis which corresponds to a multiple of the width of the teeth of the dressing tool; b) fine machining the workpiece with the tool dressed in this manner, wherein prior to carrying out work step a), the axis cross angle is set, in that, while the work step a) is being carried out, the previously set axis cross angle is maintained unchanged and in that the modification of the tooth flanks is produced exclusively by movements of the dressing tool along the workpiece longitudinal axis and the workpiece transverse axis.

2. The method according to claim 1, wherein the width of the dressing tool is at most 6 mm.

3. The method according to claim 2, wherein the width of the dressing tool is at most 2.5 mm.

4. The method according to claim 1, wherein the width of the dressing tool is at least 0.5 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention will be explained below in more detail by means of a drawing representing an exemplary embodiment. The figures show schematically in each case:

[0033] FIG. 1 a machine tool for internal toothing honing of internally-toothed gear wheels in a frontal view;

[0034] FIG. 2 the flank surfaces of a tooth of an internally-toothed gear wheel in a perspective view;

[0035] FIG. 3a a tool for dressing or toothing an externally-toothed honing tool in frontal view;

[0036] FIG. 3b the tool according to FIG. 3a in a section along the section line A-A drawn in FIG. 3a;

[0037] FIG. 4 the movements of a dressing tool carried out in the course of the method according to the invention during the honing process.

DESCRIPTION OF THE INVENTION

[0038] Neither the spatial assignment nor the width ratios are shown correctly to scale in the figures.

[0039] The conventionally designed machine tool 1 comprises a workpiece spindle 1 and a tool spindle 3.

[0040] The workpiece spindle 2 is equipped with a receptacle 4 for the internally-toothed workpiece to be respectively processed and is coupled to a rotary drive for rotating the workpiece about a workpiece rotational axis C1, to an actuating drive for adjusting the workpiece spindle 2 along a workpiece longitudinal axis Z1 aligned parallel to the workpiece rotational axis C1 and to an actuating drive for adjusting along a workpiece transverse axis X1, which is aligned transverse to the workpiece longitudinal axis Z1.

[0041] The tool spindle 3 is equipped with a receptacle 5 for an externally-toothed tool 6 and is coupled to a rotary drive for rotating the tool 6 about a tool rotational axis E1.

[0042] Furthermore, a device 7 is provided for setting an axis cross angle Σ.sub.A, at which the workpiece rotational axis C1 and the tool rotational axis E1 are aligned in a skewed manner to one another during use such that they intersect at a projection in the drawing plane, as shown in FIG. 4. The device 7 is designed for this purpose in a known manner such that it enables a pivoting and fixing of the tool spindle 3 with respect to a pivot axis B1 which is aligned transverse to the tool rotational axis E1.

[0043] In order to enable an adjustment of the tool spindle 3 with respect to the plane spanned by the workpiece longitudinal axis Z1 and the workpiece transverse axis X1, an adjustment axis Y1 aligned normal to the concerning plane can additionally be provided, but is not required for carrying out the method according to the invention.

[0044] In FIG. 2, the twists to be produced on the tooth flanks F1, F2 of a tooth of an internally-toothed workpiece are shown. The surfaces surrounded with continuous lines thereby indicate the twists FV1, FV2 targetedly produced, i.e. the surface sections, in which the flank surfaces F1, F2 of the flank surfaces processed according to the invention, deviate from the design which the tooth flank surfaces F1, F2 would have if they had a standard shape free of the twists or other targetedly produced flank modifications. This standard shape of the flank surfaces F1, F2 is indicated in FIG. 2 with dashed lines.

[0045] The structure of the annular dressing unit 11 represented in FIG. 3a and FIG. 3b is described in detail in DE 10 2017 104 625 A1 already mentioned above, whose content is incorporated into this application by reference. Accordingly, the dressing unit 11 comprises a support ring 12 formed from a suitable steel material, which support ring 12 circulates around a central longitudinal axis L and surrounds a support ring opening 13. The central longitudinal axis L is thereby aligned concentrically to the support ring opening 13.

[0046] Starting from the one front side 14 of the support ring 12, a circumferential shoulder is formed into the edge region assigned to the support ring opening 13. This circumferential shoulder forms a support element for a dressing tool 15, which is designed as a ring element and is therefore also referred to in practice as a “dressing wheel” and is composed of a plurality of ring segments, and which sits on the support element and at the same time abuts tightly against the inner circumferential surface of the support ring 12 facing the support element.

[0047] The dressing tool 15 has, on its inner circumference assigned to the support ring opening 13, an internal toothing 16, which is formed by teeth 17 arranged distributed at even angular spacings around the centre of the dressing tool 15. The teeth 17 of the internal toothing 16 protrude freely over the edge of the support element facing the support ring opening 13 and have, on their tooth flanks and, if applicable, also on their tooth head, in each case a cutter 18, with which they remove material during the dressing process from the honing tool 6 to be dressed.

[0048] The width D of the dressing tool 15 measured parallel to the longitudinal axis L of, for example, 3.2 mm is substantially smaller than the width of the teeth of the external toothing of the honing tool 6 to be processed. In this case, the dressing tool 15 consists, for example, of synthetic diamond, which is applied as a cutting material layer to a support layer consisting preferably of a hard metal material. The manufacture of the dressing tool 15 takes place in the manner known per se and described for example in EP 2 036 675 B1 and WO 2011/157830 A1.

[0049] For dressing the honing tool 6, the dressing unit 11 is placed with the dressing tool 15 into the receptacle of the workpiece spindle 2 in which the workpiece to be respectively processed sits during normal honing operation.

[0050] The tool rotational axis E1 and the workpiece rotational axis C1 are thereby aligned at an axis cross angle Σ.sub.A, which corresponds unchanged to the axis cross angle at which the rotational axes E1 and C1 are aligned with one another during the normal honing process. If required however, an axis cross angle Σ.sub.A can also be set, which deviates from the axis cross angle provided for the honing process. This can then be the case if the correspondingly deviating setting of the axis cross angle Σ.sub.A provided for the dressing process contributes to producing special modifications of the shape of the tooth flanks F1, F2. What is decisive here is that the axis cross angle Σ.sub.A, which has been set once, is maintained unchanged during the dressing process.

[0051] At the start of the dressing process, the dressing unit 11 rotating about the workpiece rotational axis C1 is positioned with the dressing tool 15 adjacent to the one front side of the honing tool 6 to be dressed and rotating about the tool rotational axis E1. Then, the dressing unit 11 is moved with the dressing tool 15 towards the honing tool 6 along the workpiece longitudinal axis Z1 until the teeth 17 of the dressing tool 15 engage into the tooth gaps of the honing tool 6 which is helically toothed here and dressing tool 15 and honing tool 6 begin to mesh with one another. At the same time, the dressing tool 15 is moved in the direction of the workpiece transverse axis X1.

[0052] In the course of this, the movement along the workpiece transverse axis X1 is varied such that correspondingly to the twist FV1, FV2 to be reproduced, the cutter 18 of the respective tooth 17 of the dressing tool 15 engaged with one of the teeth of the honing tool 6 removes more or less material from the tooth flank F1, F2 respectively processed.

[0053] The invention thus provides a method which allows modifications, such as twists FV1, FV2, to be produced on the tooth flanks F1, F2 of an internally-toothed workpiece by an externally-toothed tool 6 on a machine tool 1, which has a reduced number of adjustable axes. To this end, the invention provides that the tool 6 is dressed by arranging an internally-toothed dressing tool 15 on the workpiece spindle 2 of the machine tool 1 at the position intended for the workpiece to be respectively honed and by bringing the dressing tool 15 into engagement with the tool 6 to be dressed. The width of the teeth 17 of the dressing tool 15 is smaller than the width of the tool 6 to be dressed such that the dressing tool 15 must be moved by a length along the workpiece longitudinal axis Z1 which corresponds to a multiple of the width D of the teeth of the dressing tool 15. Subsequently, the fine machining of the workpiece 6 takes place with the tool 1 dressed in this manner. According to the invention, an axis cross angle Σ.sub.A is set for the dressing which is maintained unchanged during the dressing. The respective tooth flank modification FV1, FV2 is then produced on the workpiece 6 during dressing exclusively by movements of the dressing tool 15 along the tool longitudinal axis Z1 and the tool transverse axis X1.

REFERENCE NUMERALS

[0054] 1 Machine tool [0055] 2 Workpiece spindle [0056] 3 Tool spindle [0057] 4 Receptacle for the internally-toothed workpiece to be processed [0058] 5 Receptacle for an externally-toothed honing tool 6 [0059] 6 Honing tool [0060] 7 Device for setting an axis cross angle Σ.sub.A [0061] 11 Annular dressing unit (see DE 10 2017 104 625 A1) [0062] 12 Support ring [0063] 13 Support ring opening [0064] 14 Front side of the support ring 12 [0065] 15 Dressing tool [0066] 16 Internal toothing of the dressing tool 15 [0067] 17 Teeth of the dressing tool 15 [0068] 18 cutter of the teeth 17 [0069] B1 Pivot axis of the tool spindle 3 [0070] C1 Workpiece rotational axis [0071] D Width of the dressing tool 15 [0072] E1 Tool rotational axis [0073] F1, F2 Tooth flanks of a tooth of an internally-toothed workpiece [0074] FV1, FV2 Twists [0075] L Central longitudinal axis of the dressing unit 11 [0076] X1 Workpiece transverse axis [0077] Y1 Adjusting axis of the tool spindle 3 [0078] Z1 Workpiece longitudinal axis [0079] Σ.sub.A Axis cross angle