EP3953079B1 - Method for producing a hollow shaft - Google Patents

Description

The invention relates to a method for producing a hollow shaft from a tubular preform by flow forming, wherein both ends of the preform are each formed with at least one forming roller, wherein a tubular preform with a round or polygonal cross-section is used and the preform is held by a workpiece holder in the central tube region during the entire manufacturing process up to the finished hollow shaft.

Out of DE 103 37 929 A1 A method is known for producing one-piece hollow bodies with profiled end regions from a preform with a circular tube cross-section, whereby the preform is first ironed in its middle region in a first process step. After this ironing step has been completed, the preform is inserted into another workpiece holder and then at least one end region is ironed in a second process step and this end region is further processed if necessary in a third process step.

However, this known method is relatively complex, since in order to carry out the various process steps it is necessary to hold the preform or the partially already formed preform in different workpiece holders one after the other, so that a continuous forming process is not possible. In addition, when changing the workpiece holder, complex adjustment is required to ensure that the preform is exactly concentric with the forming rollers. Furthermore, the method is limited to tubular preforms that can be stretched by flow forming.

A method having the features of the preamble of patent claim 1 is known from JP 2002 239657 A and JP 2003 074336 A known.

The object of the invention is to further develop such a process in such a way that it enables a continuous process sequence and is universally applicable.

This object is achieved according to the invention in a method of the type described at the outset in that an external and/or internal profiling is introduced into both ends, wherein, before the external and/or internal profiling is introduced, an optionally profiled internal mandrel is axially inserted into both ends and the two internal mandrels are connected to one another at the front in a force-fitting and/or form-fitting manner.

The method makes it possible to carry out the entire forming process with just one workpiece holder, so that the entire forming process can run continuously. This also eliminates the need for additional adjustments that would be required when changing the workpiece holder. It is also possible to use tubular preforms with a round (circular) or polygonal cross-section, so that the hollow shaft produced in this way is suitable for various applications, e.g. for holding winding packages in an electric motor. During the respective forming, the preform is set in rotation relative to at least one forming roller, for which purpose the workpiece holder with the preform and/or the at least one forming roller is driven. During the forming, the e.g. polygonal cross-section in the middle tube area, which is held by the workpiece holder, remains unchanged, while only the end areas are formed rotationally symmetrically, so that the middle area can, for example, hold winding packages of an electric motor without further forming. Since the middle area is not formed, no inner mandrel is required in the middle area, but inner mandrels are only inserted into the two end areas, while the preform in the middle area is held from the outside by a workpiece holder.

Both drawn and welded tubes can be used as preforms.

In a particularly preferred embodiment, it is provided that the two ends of the preform are formed at least partially simultaneously. This shortens the forming time on the one hand, and on the other hand leads to torque neutralization in the middle tube area.

Depending on the requirements of the finished hollow shaft, it is preferably provided that at least one end is stepped once or several times, i.e. axially adjacent areas with different diameters are created.

Since the finished hollow shaft is to have an external or internal profile at both ends, it is intended that an internal mandrel is inserted into each end. To introduce an external profile, at least one correspondingly profiled forming roller and one non-profiled internal mandrel are used, and to introduce an internal profile, at least one non-profiled forming roller and one profiled internal mandrel are used.

The two inner mandrels are designed to be connected to one another in a force-fitting and/or form-fitting manner at the front. The front ends of the two inner mandrels can, for example, have a spur gear and are pressed axially against one another and thereby locked so that any lateral radial forces that arise can be absorbed.

Finally, it is advantageous that the forming takes place at least temporarily with the application of heat. The heat can be generated inductively, for example, and this application of heat can simultaneously harden the component.

The invention is explained in more detail below with reference to the drawing.

Fig. 1

einen Längsschnitt durch eine rohrförmige Vorform,

Fig. 2

einen Schnitt gemäß der Linie A-A in Fig. 1 mit drei verschiedenen Ausführungsformen,

Fig. 3

eine perspektivische Darstellung der in einem mittleren Rohrbereich von einem Werkstückhalter gehaltenen Vorform während der Umformung,

Fig. 4

eine Seitenansicht der Fig. 3, teilweise im Längsschnitt,

Fig. 5

einen Längsschnitt durch eine fertige Hohlwelle,

Fig. 6

ein Detail X in Fig. 5,

Fig. 7

ein Detail Y in Fig. 5,

Fig. 8

einen Längsschnitt durch eine Hohlwelle während der Umformung unter Verwendung zweier geteilter Innendorne,

Fig. 9

eine Abwandlung der Fig. 8 mit zwei in Axialrichtung formschlüssig miteinander verbundenen Innendornen,

Fig. 10

eine perspektivische Darstellung der beiden Innendorne nach Fig. 9,

Fig. 11

einen Endbereich einer Vorform mit einer eine radiale und axiale Kraft aufbringenden Umformrolle und

Fig. 12

eine perspektivische Darstellung der Fig. 11.

These show in

Fig.1

a longitudinal section through a tubular preform,

Fig.2

a section along the line AA in Fig.1 with three different designs,

Fig. 3

a perspective view of the preform held in a central tube area by a workpiece holder during forming,

Fig.4

a side view of the Fig.3 , partly in longitudinal section,

Fig.5

a longitudinal section through a finished hollow shaft,

Fig.6

a detail X in Fig.5 ,

Fig.7

a detail Y in Fig.5 ,

Fig.8

a longitudinal section through a hollow shaft during forming using two split inner mandrels,

Fig.9

a variation of the Fig.8 with two axially connected inner mandrels,

Fig.10

a perspective view of the two inner mandrels according to Fig.9 ,

Fig. 11

an end region of a preform with a forming roller applying a radial and axial force and

Fig. 12

a perspective view of the Fig. 11 .

A tubular preform is in Fig.1 generally designated 1. This tubular preform 1 can be a drawn or welded tube made of metal. It is essential for the invention that the tubular preform can have any round or polygonal cross-section.

In Fig.2 It is indicated by way of example that it can have a circular, square or triangular cross-section. In general, any cross-sectional shape, preferably polygonal cross-sectional shape, is possible depending on the respective application.

Since the central tube region 1a of the tubular preform 1 is not formed in the method according to the invention, this region is suitable, for example, for receiving winding packages of an electric motor or the like without further processing.

In order to produce a hollow shaft from the tubular preform 1 by flow forming, the invention provides that the tubular preform 1 is held in its central tube region 1a by a workpiece holder 2 throughout the entire manufacturing process up to the finished hollow shaft. This split, ring-shaped workpiece holder 2 accordingly has an inner contour that corresponds to the outer contour of the tubular preform 1.

Since the preform 1 is held in its central region 1a by the workpiece holder 2 during the entire manufacturing process, the entire process sequence can be carried out continuously without changing to another workpiece holder.

Preferably, it is provided that the two ends 1b and 1c of the preform 1 are formed at least partially simultaneously by means of forming rollers generally designated 3. At least one forming roller 3 is provided for forming each of the two ends 1b, 1c. In the embodiment according to the Fig. 3 and 4 For the forming of the end 1b, three forming rollers 3 and of the end 1c a forming roller 3 is indicated.

The forming rollers 3 are designed to be radially movable relative to the longitudinal axis 4 of the preform 1. Depending on the desired forming process, they can also be movable in the axial direction.

During the forming process, the spinning rollers 3 are set in rotation relative to the workpiece holder 2 and the tubular preform 1, so that either the spinning rollers 3 or the workpiece holder 2 with the preform 1 are driven.

Through the Fig. 3 and 4 In the deformation shown, the two ends 1b and 1c of the preform 1 are deformed rotationally symmetrically, ie the two ends 1b and 1c no longer have a polygonal cross-sectional shape if the original preform 1 had a polygonal cross-section. The polygonal cross-section is of course retained in the unprocessed central region 1a.

Starting from the tubular preform 1 which has already been formed at both ends 1b and 1c, the two ends 1b and 1c can be further formed without changing the workpiece holder 2.

In Fig.5 It is shown that the two ends 1b and 1c are each designed with two steps in the radial direction. These stepped areas are in Fig.5 designated 1b', 1b" and 1c', 1c". In addition, a profile is introduced into the two ends 1b and 1c, namely an inner profile 5 in the end 1b and an outer profile 6 on the end 1c. The inner profile 5 and the outer profile 6 can be a toothing, a knurling or another geometric shape.

To produce the inner profiling 5 or the outer profiling 6, suitable forming rolls as well as inner mandrels are used.

An embodiment which is not part of the invention is shown in Fig.8 The preform 1 is held unchanged in its middle area 1a in the workpiece holder 2 and an inner mandrel 7 without profiling is axially inserted into the already stepped end 1b, while an inner mandrel 8 with external profiling 8a is inserted into the end 1c. In order to Fig.8 In order to introduce an external profile 6 into the end 1b of the preform 1, at least one forming roller 9 with an external profile 9a is provided in addition to the inner mandrel 7. On the other hand, in order to introduce an internal profile 5 into the end 1c of the preform 1, at least one forming roller 10 without an external profile is provided in addition to the inner mandrel 8 with an external profile 8a, ie the end 1c is pressed into the external profile 8a of the inner mandrel 8 by the forming roller 10, so that the internal profile 5 is created.

In contrast to the embodiment according to Fig.8 are designed according to the Figs. 9 and 10 not two separate inner mandrels 7 and 8 are used, but the two inner mandrels 7' and 8' are connected to each other at the front and/or in a form-fitting manner. For this purpose, the two inner mandrels 7' and 8' each have a complementary face toothing 7a, 8a. The inner mandrels 7' and 8' are then pressed together in the axial direction during the forming process by applying pressure from the outside, which absorbs lateral radial forces that arise during the forming process.

It is also possible to feed metal material to at least one of the two ends 1b, 1c of the preform 1 during the forming process (in the forming zone) if an axial force is applied to the respective end 1b or 1c. This forming process is described in the Fig. 11 and 12 At least one forming roller 11 is used, which has a stepped, tubular outer peripheral area with a circumferential contact surface 11a. With this forming roller 11, an axial force F _axial and a radial force F _radial are applied to the preform 1. This material feed can also be carried out several times, e.g. before the actual forming of the ends 1b, 1c and afterwards.

The entire manufacturing process can be carried out by cold forming alone. However, the forming can also take place entirely or temporarily under the influence of heat, e.g. by inductive heat generation. This allows the preform 1 to be hardened at the same time.

List of reference symbols:

1

Tubular preform

1a

Middle pipe area

1b, 1c

end up

1b', 1c'

Graduated area

1b", 1c"

Graduated area

2

Workpiece holder

3

Forming rolls

4

Longitudinal axis

5

Internal profiling

6

External profiling

7.7'

Inner mandrel

7b

Spur gearing8.8' inner mandrel

8a

External profiling

8b

Spur gearing

9

Forming roll

9a

External profiling

10

Forming roll

11

Forming roll

Fax

axial force

Fradial

radial force

Claims (5)

1. Method for producing a hollow shaft from a pipe-shaped preform by means of flow-forming, wherein both ends of the preform are reshaped using at least one forming roller, wherein a pipe-shaped preform (1) having a round or a polygonal cross-section is used and the preform (1) is held in the central pipe region (1a) by a workpiece holder (2) during the entire production process until the hollow shaft is finished,
   characterised in that
   in both ends (1b, 1c) an outer and/or inner profiling (5, 6) is introduced, wherein prior to the introduction of the outer and/or inner profiling (5, 6) in each case an inner mandrel (7, 7', 8, 8'), profiled if appropriate, is introduced axially at both ends (1b, 1c) and the two inner mandrels are connected at the end faces in a force-fitting and/or form-fitting manner with one another.
2. Method according to claim 1,
   characterised in that
   a drawn or welded preform (1) is used.
3. Method according to claim 1 or 2,
   characterised in that
   the two ends (1b, 1c) of the preform (1) are reshaped at least partially at the same time.
4. Method according to one or more of claims 1 to 3,
   characterised in that
   at least one end (1b, 1c) has a single or multiple gradation.
5. Method according to one or more of claims 1 to 4,
   characterised in that
   the reshaping takes place at least temporarily during the application of heat.

Images