THIN-WALLED HOLLOW WHEELS WITH INTERNAL AND EXTERNAL TOOTHING, AND APPARATUS AND METHOD FOR MANUFACTURING THE SAME

Abstract

In a method for manufacturing a hollow wheel which includes an internal toothing and an external toothing, wherein the internal toothing is a gear toothing, a workpiece is machined by way of a stamping tool. The workpiece has a tubular section with a longitudinal axis and a first stabilisation section for the shape stabilisation of the tubular section during the machining. The tubular section is inserted into a die having an internal die toothing. The workpiece is machined on the inner side by the stamping tool so as to simultaneously produce internal and external toothing by way of the workpiece executing a rotation movement with a temporally varying rotation speed and the stamping tool executing radially oscillating movements that are synchronised with the rotation movement.

Claims

1. A method for manufacturing a hollow wheel which comprises an internal toothing and an external toothing, wherein the internal toothing is a gear toothing, wherein a workpiece is machined by way of at least one stamping tool, wherein the workpiece comprises a tubular section with a longitudinal axis as well as at least one first stabilisation section which is connected to the tubular section for shape stabilisation of the tubular section during the machining by way of the at least one stamping tool, wherein a die is provided for receiving the tubular section, the die comprising a tubular opening in which an internal die toothing is provided, and the tubular section is inserted into the tubular opening, and the workpiece is subsequently machined on the inner side of the tubular section inserted into the tubular opening by way of the at least one stamping tool for simultaneously producing the internal toothing and external toothing, as the workpiece executes a rotation movement with a temporally varying rotation speed about said longitudinal axis and the at least one stamping tool executes radially oscillating movements which are synchronised with said rotation movement, so that the at least one stamping tool forms the tubular section into the die toothing for producing the external toothing and simultaneously producing the internal toothing by way of repeated hammering machining of the tubular section, wherein the term radially characterizes alignments perpendicular to the longitudinal axis.

2. The method according to claim 1, wherein a material thickness of the workpiece in the tubular section is less than twice, in particular less than 1.5 times a toothing depth of the internal toothing, before the insertion of the tubular section into the tubular opening.

3. The method according to claim 1, wherein the at least one stamping tool comprises an active region which comprises a tool head and two tool flanks adjoining the tool head, in particular wherein the active region has a shape which is a negative of a shape of a tooth gap of the internal toothing.

4. The method according to claim 3, wherein the tool flanks are shaped such that the internal toothing has a longitudinal crowning.

5. The method according to claim 3, wherein the at least one stamping tool comprises two calibrating regions adjoining one of the two tool flanks each and having a shape which is a negative of a shape of a section of a tooth tip of the internal toothing.

6. The method according to claim 1, wherein the first stabilisation section forms a non-toothed collar of the hollow wheel, said collar forming a unitary part together with the tubular section and being directed towards the longitudinal axis or away from the longitudinal axis

7. The method according to claim 1, wherein the first stabilisation section has a maximal distance to the longitudinal axis which is larger than a maximal distance the tubular section has to the longitudinal axis by at least 0.25 times a toothing depth of the internal toothing, in particular wherein the first stabilisation section has an outer diameter which is larger than an outer diameter of the tubular section by at least 0.5 times a toothing depth of the internal toothing; or the first stabilisation section has a minimal distance to the longitudinal axis which is smaller than a minimal distance the tubular section has to the longitudinal axis by at least 0.25 times a toothing depth of the internal toothing, in particular wherein the first stabilisation section has an inner diameter which is smaller than the inner diameter of the tubular section by at least 0.5 times a toothing depth of the internal toothing.

8. The method according to claim 1, wherein the first stabilisation section forms a peripheral end-face of the hollow wheel which is angled with respect to the tubular section, in particular wherein the first stabilisation section describes an annulus shape or a rotationally symmetrical truncated cone shell shape.

9. The method according to claim 1, wherein the workpiece comprises a second stabilisation section and wherein at least one of the two stabilisation sections is directed towards the longitudinal axis, and in particular wherein a minimal distance the second stabilisation section has to the longitudinal axis is smaller than a minimal distance a tooth crown of the internal toothing has to the longitudinal axis.

10. The method according to claim 1, wherein the internal toothing is designed as a full-depth toothing with a toothing depth of more than 2.0 times a normal module of the internal toothing, in particular with a toothing depth of at least 2.4 times a normal module of the internal toothing.

11. The method according to claim 1, wherein a toothing depth of the external toothing is smaller than a toothing depth of the die toothing and is smaller than a toothing depth of the internal toothing.

12. The method according to claim 1, wherein the internal toothing is a spur toothing or a helical toothing or a herringbone toothing.

13. A method for manufacturing a planetary gear, comprising manufacturing a hollow wheel by way of a method according to claim 1, and further comprising providing at least one externally toothed gearwheel and inserting of the gearwheel into the hollow wheel.

14. An apparatus for manufacturing hollow wheels which comprise an internal toothing and an external toothing, wherein the internal toothing is a gear toothing, comprising a die which for receiving a tubular section of a workpiece comprises a tubular opening in which an internal die toothing is formed; a die holder which is rotatable about a longitudinal axis, for holding the die in a manner such that a tubular section of a workpiece which is received in the die is machinable at its inner side; a rotation drive for the rotation of the die holder, said drive being designed for producing a rotation with a temporally varying rotation speed, in particular for producing an intermittent rotation; a tool holder for holding at least one stamping tool, said tool holder being drivable into a an oscillating movement which runs perpendicularly to the longitudinal axis, so that the tubular section is repeatedly, in particular periodically machinable at its inner side by the at least one stamping tool; a synchronisation device for the synchronisation of the rotation of the die holder which is producible by way of the rotation drive, with the oscillating movement of the tool holder which runs perpendicularly to the longitudinal axis.

15. The apparatus according to claim 14, comprising a loading device for inserting a tubular section of a workpiece which is to be received in the die, into the tubular opening of the die, comprising a further drive for a relative movement of the workpiece and die, said relative movement running parallel to the longitudinal axis.

16. The apparatus according to claim 14, comprising a holding device for fixing a position of a workpiece which is received in the die, relative to the die during said rotation of the die holder, in particular wherein a pressing pressure can be produced by way of the holding device, by way of which pressure the workpiece and the die are pressed onto one another in the axial direction.

17. The apparatus according to claim 14 for simultaneously creating an internal toothing and an external toothing in a tubular section of a workpiece, wherein the internal toothing is a gear toothing.

18. A hollow wheel, comprising a tubular section with a longitudinal axis, which comprises an internal toothing and an external toothing, wherein the internal toothing is a gear toothing; a non-toothed first stabilisation section which forms a unitary part together with the tubular section and forms a collar of the hollow wheel which is directed towards the longitudinal axis or away from the longitudinal axis.

19. A hollow wheel according to claim 18, wherein the first stabilisation section describes an annulus shape or a rotationally symmetrical truncated cone shell shape.

20. The hollow wheel according to claim 18, wherein the collar is directed towards the longitudinal axis and comprises an inner diameter which is smaller than a tip diameter of the internal toothing, in particular smaller than a tip diameter of the internal toothing by 0.3 times a toothing depth of the internal toothing; or the collar is directed away from the longitudinal axis and comprises an outer diameter which is larger than a tip diameter of the external toothing, in particular larger than a tip diameter of the external toothing by at least 0.3 times a toothing depth of the internal toothing.

21. The hollow wheel according to claim 18, comprising a second stabilisation section, wherein the second stabilisation section is directed towards the longitudinal axis, and in particular wherein a minimal distance of the second stabilisation section to the longitudinal axis is smaller than a minimum distance of a tooth tip of the internal toothing to the longitudinal axis.

22. The hollow wheel according to claim 18, wherein the collar is directed away from the longitudinal axis and an internal residual toothing adjoining the internal toothing is formed in a transition region between the tubular section and the first stabilisation section, wherein a tip diameter of the internal residual toothing is smaller than a tip diameter of the internal toothing; and/or an axially projecting bead is formed on each tooth root of the internal residual toothing.

23. The hollow wheel according to claim 18, wherein an external residual toothing adjoining the external toothing is formed in a transition region between the tubular section and the first stabilisation section, wherein a toothing depth of the external residual toothing in the transition region continuously reduces from a toothing depth of the external toothing to zero, in particular wherein teeth of the external residual toothing have a rounded shoulder in the transition region.

24. The hollow wheel according to claim 18, wherein a difference of the root diameter of the external toothing and the tip diameter of the internal toothing is less than twice, in particular less than 1.5 times a toothing depth of the internal toothing

25. A hollow wheel component comprising a hollow wheel according to claim 18 as well as a body which is rotationally secured with respect to the hollow wheel by way of comprising an inner profiling which matches the external toothing, in particular wherein the body is positively connected to the external toothing.

26. A planetary gear comprising a hollow wheel according to claim 18, further comprising at least one externally toothed gearwheel which is inserted into the hollow wheel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0185] The subject-matter of the invention is hereinafter explained in more detail by way of embodiment examples and the attached drawings. There are shown schematically in:

[0186] FIG. 1 shows details of an apparatus for manufacturing hollow wheels, in a section that runs through the longitudinal axis;

[0187] FIG. 2a is an illustration of the method before a first stamping tool engagement into the workpiece, in a section perpendicular to the longitudinal axis;

[0188] FIG. 2b is an illustration of the method during a stamping tool engagement on manufacturing a hollow wheel, in a section perpendicular to the longitudinal axis;

[0189] FIG. 3a shows workpiece with two stabilisation sections, which are directed towards the longitudinal axis, in a section which runs through the longitudinal axis;

[0190] FIG. 3b shows a workpiece with a stabilisation section, which is directed towards the longitudinal axis, and a stabilisation section, which is directed away from the longitudinal axis, in a section that runs through the longitudinal axis;

[0191] FIG. 3c shows a detail of a workpiece with a stabilisation section which is directed towards the longitudinal axis and with a stabilisation section which is directed away from the longitudinal axis, in a section that runs through the longitudinal axis;

[0192] FIG. 3d shows a detail of a hollow wheel with a stabilisation section which is directed towards the longitudinal axis and with a stabilisation section, which is directed away from the longitudinal axis, in a section that runs through the longitudinal axis;

[0193] FIG. 4 shows a detail of a hollow wheel for illustrating an external residual toothing in a section that runs through the longitudinal axis;

[0194] FIG. 5 shows a detail of a hollow wheel with a stabilisation section, which is directed away from the longitudinal axis, for illustrating an internal residual toothing with a bead, in a section through a tooth root of the internal toothing, the section running through the longitudinal axis;

[0195] FIG. 6 shows a detail of a hollow wheel with a stabilisation section, which is directed away from the longitudinal axis, for illustrating an internal residual toothing, in a section through a tooth tip of internal toothing, the section running through the longitudinal axis;

[0196] FIG. 7a shows a detail of the stamping tool, in a section perpendicular to the course of the tool head;

[0197] FIG. 7b shows a detail of the stamping tool of FIG. 7a, in a section parallel to the course of the tool head along the dashed line of FIG. 7a, through the tool flanks;

[0198] FIG. 8a is an illustration of a spur toothing;

[0199] FIG. 8b is an illustration of a helical toothing;

[0200] FIG. 8c is an illustration of a herringbone toothing;

[0201] FIG. 9 is an illustration of a planetary gear;

[0202] FIG. 10 shows hollow wheel component including a hollow wheel and a body, which is positively connected thereto, in a section perpendicular to the longitudinal axis.

DETAILED DESCRIPTION OF THE INVENTION

[0203] Parts that are not essential for the understanding of the invention are to some extent not represented. The described embodiment examples are exemplary for the subject matter of the invention or serve for its explanation and have no limiting effect. Most of the following embodiments, for the sake of simplicity, implicitly or explicitly relate to spur toothings but can also be conferred upon other toothing types.

[0204] FIG. 1 shows details of an apparatus for manufacturing hollow wheels, in a greatly schematised sectioned representation. A workpiece 1 is thin-walled and can be provided with an internal toothing and an external toothing by way of the apparatus, wherein the internal toothing is a gear toothing, for example an involute toothing.

[0205] The workpiece 1 has a longitudinal axis Z and a tubular section 3, which is cylindrical and is aligned coaxially to the longitudinal axis Z and into which the two mentioned toothings are incorporated by way of a stamping tool 2

[0206] The section, which is represented in FIG. 1, runs through the longitudinal axis Z.

[0207] The apparatus further includes a die 5, which includes an internal die toothing 5z as well as a tubular opening 5o for receiving the workpiece 1. The die 5 is held in a die holder 15, which is driveable into rotation about a rotation axis, for example, by way of a driven headstock 8

[0208] The stamping tool 2, by way of which a workpiece 1 can be periodically machined, is held by way of a tool holder 12. For this, the tool holder 12 executes an oscillating movement in the radial direction (illustrated by a small double arrow in FIG. 2). Directions that run perpendicular to the longitudinal axis Z are indicated as radial.

[0209] The workpiece 1 is inserted into the tubular opening 5o of the die 5 in the axial direction, as is symbolised by the open arrows, by way of the loading device 16. The tool 1 is then held in a fixed position relative to the die 5 by way of a holding device 18, which can be partly identical to the loading device 16, typically before and during the workpiece and die rotation, for example by way of pressing the two parts against one another in the axial direction.

[0210] The die 5 (and in particular its die toothing 5z), the workpiece 1 (and in particular its tubular section 3 and its longitudinal axis Z) and the rotation axis of the die holder 15 are aligned coaxially to one another during the machining of the workpiece 1 by the stamping tool 2. And the workpiece 1 co-rotates with the die holder 15, for example by way of the holding device 18 being rotatably mounted.

[0211] Since therefore the longitudinal axis Z of the workpiece 1 coincides with the rotation axis of the rotatable die holder 15 during the machining, for the sake of simplicity the respective axes are hereinafter both indicated as the longitudinal axis Z or as the axis Z

[0212] The die holder 15 does not need to be directly drivable for its rotation. For example, the holding device 18 can also be driven (for example directly) for rotation, and the die holder 15 is rotatably mounted and co-rotates, including the die 5 and the workpiece 1, with the holding device 18.

[0213] The rotation takes place with a temporally varying rotation speed, synchronised with the radially oscillating movement of the stamping tool 2.

[0214] The tool holder 12, as illustrated, can include a shank, which is driven into an oscillating movement, for producing the radially oscillating movement of the stamping tool 2. In this manner, the stamping tool 2 repeatedly, generally periodically engages with the workpiece. The workpiece 1 for its part is rotated about the axis Z with a varying rotation speed, in particular intermittently rotated (illustrated by the dashed circular arrow in FIG. 1). The oscillating movement of the tool holder 12, which corresponds to an oscillating movement of the stamping tool 2, is synchronised with the rotation of the workpiece 1 such that the stamping tool 2 engages with the workpiece 1 in phases of minimal workpiece rotation speed (in the case of an intermittent workpiece rotation: in phases of the standstill of the intermittent rotation of the workpiece). In the case of an intermittent workpiece rotation, the workpiece 1 can be rotated further (typically by one pitch) as soon as the tool holder 12 is displaced far enough (in the radial direction) such that no stamping tool comes into contact with the workpiece 1 during the workpiece rotation. The speed profile (temporal variation of the rotation speed) is to be selected accordingly given a non intermittent workpiece rotation.

[0215] Thereafterthus in the case of intermittent rotation within the next standstill phasethe stamping tool 2 engages into the workpiece 1 again, for the further formation of the next tooth gap of the toothing to be produced, etc. The toothings are therefore produced in a cold reshaping manner by way of successively carrying out a number of stamping steps.

[0216] The forces, which act upon the thin-walled workpiece 1 by way of the stamping tool 2 with the stamping reshaping, are so large that undesirable deformations of the tubular section 3 can occur without further precautions. Instead of retaining its basic circular cross section, an oval or elliptical cross section of the tubular section 3 can form and lead to an insufficient accuracy of the toothings, which is very undesirable. An undesirable conicity of the tubular section 3 can also form, so that its diameter would be increasing in a direction along the longitudinal axis.

[0217] For this reason, the workpiece (during its machining) includes at least one stabilisation section. In the example of FIG. 1, the workpiece 1 has an inwardly (to the longitudinal axis) directed stabilisation section 4 and an outwardly (away from the longitudinal axis) directed stabilisation section 4 which both each connect to an end of the tubular section 3. The stabilisation sections 4, 4 form collars of the workpiece 1 and are integrally formed (and thus form a unitary part) with the tubular section 3.

[0218] Due to their extension in the radial direction, the stabilisation sections 4, 4 effect a shape stabilisation, so that said deformations can be prevented or at least reduced to an acceptable amount.

[0219] The thin-walled workpiece 1 is formed into the die toothing 5z of the die 5 by way of the stamping tool in the described manner, for the simultaneous creation of the internal and external toothing in the tubular section 3. This is illustrated by way of FIGS. 2a, 2b.

[0220] FIG. 2a is a schematic illustration of the method before a first stamping tool engagement into the workpiece 1, in a section perpendicular to the longitudinal axis; and FIG. 2b is a schematic illustration of the method during a stamping tool engagement on completing the hollow wheel 1a, in the same step.

[0221] The still untoothed workpiece 1 is located in the opening 5o of the die 5 before the first stamping tool engagement (FIG. 2a). A tooth tip 5a, a tooth root 5b and a tooth flank 5f of the internal die toothing are characterised in FIG. 2a. Many hammering engagements of the stamping tool 2 are carried out at each of the peripheral positions, at which the tooth gaps of the die toothing are provided, and the internal toothing and external toothing are completed after this. FIG. 2b shows the workpiece which is now a toothed hollow wheel 1a, during a last reshaping engagement of the stamping tool 2.

[0222] The thickly dashed line in FIGS. 2a, 2b characterises a radial direction, along which the periodic linear movement of the stamping tool 2 for reshaping the workpiece runs.

[0223] The thin dashed lines in FIG. 2b characterise the root diameter or the tip diameter of the internal toothing. The open arrow in FIG. 2b characterises the toothing depth t6 of the internal toothing. In the embodiment example of FIGS. 2a, 2b, the material thickness D of the untoothed tubular section 3 (FIG. 2a) is about 0.4 times the toothing depth t6 of the internal toothing.

[0224] The stamping tool 2 includes an active region 2w, which includes a tool head 2k and two tool flanks 2f The active region 2w has a shape that is a negative of a shape of a tooth gap of the internal toothing that is to be produced (FIG. 2b). Furthermore, the stamping tool 2 includes two calibrating regions 2x, by way of which the tooth tips 6a (FIG. 2b) of the internal toothing are shaped, for example, one can envisage the shape of a section of a calibrating region 2x being a negative of the shape of a section of a tooth tip 6a of the internal toothing.

[0225] The tool flanks 2f have the shape of a negative of a flank 6f of the internal toothing 2, and the tool head 2k has the shape of a negative of a tooth root 6b of the internal toothing (FIG. 2b).

[0226] Whereas the shape of the internal toothing is essentially defined by the shape of the stamping tool 2, the shape of the external toothing is defined essentially by the shape of the die toothing.

[0227] The shape of a tooth tip 5a of the die toothing corresponds to a negative of the shape of a tooth root 7b of the external toothing that is to be produced. And the shape of the tooth flanks 5f of the die toothing corresponds to a negative of the shape of tooth flanks 7f of the external toothing. However, the shape of the tooth tip 7a of the external toothing is determined by free material flow. A distance remains between the tooth tips 7a of the external toothing and the respective tooth roots 5b of the die toothing. Of the tooth flanks 5f of the die toothing, it is only a section that comes into contact with the workpiece and thus determines the shape of the flanks 7f of the external toothing.

[0228] A hammering forming of the first untoothed tubular section 3 into the die toothing takes place at those locations which are distributed over the periphery of the tubular section 3, at which tooth gaps of the die toothing are located, thus where the teeth of the external toothing and tooth gaps of the internal toothing come to lie (arise). For example, the workpiece 1 can be machined once in each tooth gap of the die toothing 5z by the stamping tool 2 (thus receive precisely one radially hammering impact and be reshaped by way of this), before it is machined a further time at one of the tooth gaps of the die toothing 5z.

[0229] A production of the internal toothing takes place with a simultaneous production of external toothing.

[0230] The number of teeth and the number of tooth gaps is identical for the internal toothing and for the external toothing and for the die toothing. And the tooth roots 6b of the internal toothing are located at the same positions along the periphery of the tubular section as the tooth tips 7a of the external toothing. And accordingly the tooth tips 6a of the internal toothing are located at the same positions along the periphery of the tubular section 3 as the tooth roots 7b of the external toothing.

[0231] It is also possible to apply a second stamping tool. This, at least with regard to its active region and calibrating region, can have the same shape as the other stamping tool.

[0232] The stamping tool is distanced radially from the workpiece again each between the individual hammering machining steps.

[0233] In the method that is described here, no rolling of the stamping tool on the workpiece takes place, which is in contrast to some methods for profiling workpieces, termed as rolling-off. And the tool is also not permanently in contact with the workpiece but always only briefly with a subsequent phase in which no contact and no reshaping takes place. And the tool does not have a multitude of teeth that are distributed over its periphery, but, as represented, only a tooth-like active region or at the most two (not represented).

[0234] FIG. 3a shows a workpiece 1 with two stabilisation sections 4, 4, which are directed towards the longitudinal axis Z, in a section that runs through the longitudinal axis Z. The stabilisation sections 4, 4 each form a collar, which is also the case with the further embodiments. The characteristics that are described hereinafter can also be attributed to the respective collar.

[0235] FIG. 3b shows a workpiece 1 with a stabilisation section 4, which is directed towards the longitudinal axis and a stabilisation section 4, which is directed away from the longitudinal axis, in a section that runs through the longitudinal axis Z.

[0236] The stabilisation sections, which are shown in FIGS. 3a, 3b, each form annulus-shaped end-faces 4f of the workpiece 1. An opening angle of the end-faces 4f, however, does not need to be 90 as in FIGS. 1 and 3a and 3b. However, a high shape stability with very small extensions along the longitudinal axis Z can be achieved at 90.

[0237] FIG. 3c shows a detail of a further rotationally symmetrical workpiece 1 with a stabilisation section 4 that is directed towards the longitudinal axis Z and, with a stabilisation section 4 that is directed away from the longitudinal axis Z, in a section that runs through the longitudinal axis, wherein the stabilisation section 4 has an opening angle of about 45. There, the diameter of the workpiece 1 enlarges with an increasing distance to the tubular section 3. The end-face 4f, which forms the stabilisation section 4, is a rotational symmetrical truncated cone shape.

[0238] However, a stabilisation section does not need to display a straight line in the represented sections, which contain the longitudinal axis Z; other shapes are also possible. FIG. 3d shows one example.

[0239] FIG. 3d shows a detail of a workpiece 1, which is already reshaped into a toothed hollow wheel 1a, with a stabilisation section 4, which is directed towards the longitudinal axis Z, and with a stabilisation section 4, which is directed away from the longitudinal axis, in a section that runs through the longitudinal axis Z. The stabilisation section 4 has the shape of a funnel with a bent, conical wall.

[0240] In FIG. 3d, a tooth tip 7a of the external toothing and a tooth tip 6a of the internal toothing are indicated in FIG. 3d (even if these do not lie precisely in the same section plane), independently of the shape of the stabilisation sections 4, 4. The toothed length can be recognised; this does not need to extend over the complete length of the tubular section 3.

[0241] FIG. 3d also illustrates that a maximal distance d4, which a part of the stabilisation section 4, has to the longitudinal axis Z, which with the rotational symmetry that is assumed here corresponds to half the outer diameter of the stabilisation section 4, is greater than half k7 the tip diameter of the external toothing.

[0242] FIG. 3d also illustrates that a minimal distance d4, which a part of the stabilisation section has to the longitudinal axis Z, which with the rotational symmetry, which is assumed here, corresponds to half the inner diameter of the stabilisation section 4, is smaller than a minimal distance k6, which a tooth tip 6a of the internal toothing has to the longitudinal axis Z, thus is smaller than half k6 the tip diameter of the internal toothing.

[0243] The typically one or two stabilisation sections are generally untoothed (toothing-free); at least they are free of the internal toothing that is to be produced and free of the external toothing that is to be produced.

[0244] FIG. 4 shows a detail of a hollow wheel 1a for illustrating an external residual toothing 45a, in a section through a tooth tip 7a of the external toothing, the section running through the longitudinal axis Z. Such an external residual toothing 45a forms due to the selected cold-reshaping manufacturing method, due to the free material flow not only in the radial but also in the axial direction within tooth gaps of the die toothing.

[0245] In this embodiment example, with regard to which the stabilisation section 4 could otherwise also be directed inwards instead of outwards, there is a transition region 45 between the tubular section 3 and the stabilisation section 4. In the transition region there is an external residual toothing with tooth tips 45, the external residual toothing connecting to the external toothing and in which the toothing depth of the residual toothing slowly decreases, specifically from the toothing depth t7 of the external toothing to zero. An angle of the reduction of the toothing depth can be defined for example as described further above: the points, at which the residual toothing has a toothing depth of 90% of the toothing depth t7 of the external toothing or only yet 10% of the toothing depth t7 of the external toothing, in FIG. 4 are where the dotted lines change directions at right angles. The thickly dashed line with the longitudinal axis Z forms the same angle as a straight line through the two mentioned points, but is not drawn there for the purpose of a better overview. The angle in FIG. 4 is about 20

[0246] In FIG. 4, independently of this, it is yet represented that the transition region 45 that otherwise describes a region that is extended along the longitudinal axis Z can include an untoothed section and/or a region that is not machined by the stamping tool 2

[0247] As mentioned further above, further structures that are characteristic of the manufacturing method also form in a transition region 45 where an internal residual toothing is produced close to a stabilisation section, for example because of a stamping tool, which is longer than the length of the internal toothing is used for producing the internal and external toothing. FIGS. 5 and 6 show respective examples.

[0248] FIG. 5 shows a detail of a workpiece 1, which is already reshaped into the toothed hollow wheel 1a, with a stabilisation section 4 which is directed away from the longitudinal axis Z, for illustrating an internal residual toothing with a bead 45, in a section through a tooth root 6b of the internal toothing, the section running through the longitudinal axis Z. The section therefore also runs through a tooth root 45b of the internal residual toothing. A bead 45w forms for each tooth root 6b of the internal toothing. This can project axially as is illustrated in FIG. 5.

[0249] FIG. 6 shows a detail of a workpiece 1, which has already been reshaped into the toothed hollow wheel 1a, with a stabilisation section 4, which is directed away from the longitudinal axis Z for illustrating an internal residual toothing, in a section through a tooth tip 45i of the internal toothing, the section running through the longitudinal axis Z. The section therefore also runs through a tooth crown 45i of the internal residual toothing. As is evident in FIG. 6, the internal residual toothing has a tip diameter that is smaller than a tip diameter of the internal toothing. In particular, the smallest tip diameter of the residual toothing is smaller than the tip diameter of the internal toothing. Half the minimal tip diameter of the internal toothing is indicated in FIG. 6 as k45, and half the tip diameter of the internal toothing is indicted as k6.

[0250] Since the described hollow wheels are thin-walled, these tend to be subjected to elastic deformations under loading. It is therefore appropriate to provide a longitudinal crowning of the internal toothing for a good running behaviour. Edge supports can be avoided in this manner. This can be achieved by way of a suitable design of the stamping tool 2.

[0251] FIG. 7 shows a detail of a stamping tool 2, in a section perpendicular to the course of the tool head 2k, thus in the same manner as FIGS. 2a, 2b.

[0252] FIG. 7b shows a detail of the stamping tool 2 of FIG. 7a, but in a section parallel to the course of the tool head 2k, along the dashed line of FIG. 7a, through the tool flanks 2f. A concavity of the stamping tool 2 can be recognised in FIG. 7b, by way of which concavity the longitudinal crowning can be produced. This however is represented in an exaggeratedly large manner in FIG. 7b. The tool flanks 2f are designed for forming the longitudinal crowning of the internal toothing due to their concavity.

[0253] FIGS. 8a to 8c illustrate a spur toothing, a helical toothing and a herringbone toothing. All these and yet further toothings can be manufactured by way of the described method. The wide black lines represent the position of the tooth crowns 6a of the internal toothing. The drawn dashed line corresponds to an axis Z, which runs parallel to the longitudinal axis Z. The representation can be understood in concept by way of cutting open the hollow wheel and then pressing it with a downwardly pointing external toothing onto a plane (flatly pressed).

[0254] In FIG. 8b, indicates the helix angle of the helical toothing.

[0255] FIG. 9 shows an illustration of a planetary gear 20 with a sun wheel 22, three planet wheels 24 and a hollow wheel 1a of the type which is described here. The respective external toothings of the wheels 22, 24, 1a are illustrated by the thick lines. The thinly drawn circular line at the outside illustrates the external toothing 7 of the hollow wheel 1a. Stabilisation sections are not represented in FIG. 9.

[0256] FIG. 10 illustrates a hollow wheel component 10, including hollow wheel 1a, which is represented in FIG. 10 in an exaggeratedly thin-walled manner and without a stabilisation section, and a body 11, which is positively connected thereto, in a section perpendicular to the longitudinal axis Z. For example, the body 11 can be of a plastic. The body 11 can be moulded, for example, onto the hollow wheel 1a, more precisely: on its external toothing.

[0257] New types of hollow wheels, components and gears can be created in the described manner, in particular ones that are suitable for lightweight construction. The respective internal cylinder toothings can be produced economically and with a high precision. The at least one collar, be it directed inwardly or outwardly, permits a shape stability during manufacture, such stability being necessary for high-precision toothings.